Patent Application
20230163154
The disclosure relates to devices for converting invisible light into visible light and its applications, and more particularly, to a terahertz wave-visible light conversion device and an image sensing device including the same.
A conventional terahertz wave detection device may use photons, thermal rectification, and a heterodyne method according to a detection principle, and may be used for a spectroscopic and imaging system configuration.
A photo-conductive antenna method that is used in a typical terahertz wave detector (having a structure in which a broadband antenna is formed on a Group III-V semiconductor) generates electron-hole pairs inside a photoconductive layer using ultrafast femtosecond pulsed laser. When using this method, an electron-hole pair is separated and accelerated by an incident terahertz wave, and is detected as a photocurrent. For detecting a signal in a terahertz band, low-temperature grown GaAs or InGaAs having high mobility and a charge lifetime of 1 ps (picosecond) or less is used for high-speed operation of the terahertz wave detection device.
A conventional superconductor-based terahertz wave detector may have a sandwich structure (Superconductor-Insulator-Superconductor (SIS)) in which a thin insulating layer with a thickness of about 2 nm is formed between two superconductors. In the conventional superconductor-based terahertz wave detector, a terahertz wave is measured by measuring a tunneling current of quasi-particles generated by electromagnetic waves having photon energy greater than or equal to a binding energy of a Cooper pair in the superconductor. Because the size of the binding energy of the Cooper pair is only 10-3 to 10-2 of a semiconductor energy gap, it is suitable for the detection of terahertz waves, but requires a measurement environment at a cryogenic temperature (several K) which can be difficult and/or expensive to maintain.
A bolometer, operates by measuring changes in electrical resistance (electric conductivity) that appear according to changes in a lattice or electron temperature of an absorber by an incident wave, and may utilize a non-cooling method or a cooling method depending on the operating temperature. Because a single-type micro-bolometer method is based on conventional silicon-based MEMS technology, it is easy to arrange and integrate, may be operated at room temperature, and thus may be suitable for real-time imaging and spectroscopy in a band of 3 THz or higher.
Provided are terahertz wave detection devices capable of detecting a terahertz wave at a high speed while having a relatively high sensitivity.
Provided are image sensing devices capable of easily acquiring information on a polarization state of a terahertz wave by including the terahertz wave detection devices.
Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the disclosure.
A light conversion device may include a substrate; a plurality of metal patterns provided on the substrate and separated from each other; a metal layer provided on the substrate and surrounding each of the plurality of metal patterns; a first slit positioned between the metal layer and each of the plurality of metal patterns and surrounding each of the plurality of metal patterns; and a light-emitting layer filling the first slit. The first slit and the metal pattern surrounded by the first slit may be concentric. The metal layer and the plurality of metal patterns may be aligned so that a first electric field enhancement occurs when a wave belonging to an invisible light band is incident to the first slit.
The light-emitting layer may extend onto the metal layer and the plurality of metal patterns.
The light-emitting layer may include at least one of quantum dots or an organic light-emitting diode (OLED) material.
The first slit may define a side surface substantially perpendicular or inclined with respect to the substrate.
Each of the plurality of metal patterns (i) may be arranged to form a second slit in which a second electric field enhancement occurs when a wave of an invisible light band is incident to the second slit, and (ii) may include a first metal portion and a second metal portion that are separated from each other. The second metal portion may completely surround the first metal portion. The second slit (i) may be present between the first metal portion and the second metal portion, (ii) may be filled with the light-emitting layer, and (iii) may have a width configured to generate visible light from the light-emitting layer by the second electric field enhancement.
The second slit may define a side surface substantially perpendicular or inclined with respect to the substrate.
The light-emitting layer may extend onto the first and second metal portions.
Each of the plurality of metal patterns (i) may be arranged to form a second slit and a third slit in which a second electric field enhancement and a third electric field enhancement respectively occur when a wave of an invisible light band is incident to the second slit and the third slit respectively, and (ii) may include a first metal portion, a second metal portion, and a third metal portion separated from each other. The first metal portion, the second metal portion, and the third metal portion may be concentric circles and may be sequentially provided in a radial direction. The second slit may be positioned between the first metal portion and the second metal portion. The third slit may be positioned between the second metal portion and the third metal portion. The second slit and third slit (i) may be filled with the light-emitting layer and (ii) may each have a respective width configured to generate visible light from the light-emitting layer by the second electric field enhancement and the third electric field enhancement.
Each of the first slit, the second slit, and the third slit may have a same width as each other.
The first slit, the second slit, and the third slit respectively may have a first width, a second width, and a third width. At least two from among the first width, the second width and the third width may be different from each other.
The first slit, the second slit, and the third slit may each define a side surface substantially perpendicular to or inclined to the substrate.
The light-emitting layer may completely fill each of the first slit, the second slit, and the third slit and extend onto the first metal portion, the second metal portion, and the third metal portion.
A light conversion device may include a substrate; a first metal layer formed on the substrate and including a plurality of first through holes separated from each other; a second metal layer provided in the plurality of first through holes and separated from the first metal layer; and a light-emitting layer filling a first gap between the first metal layer and the second metal layer. The first gap may have a first width configured to generate a first electric field enhancement according to a polarization state of a wave when the wave belonging to an invisible light band is incident.
A side surface of the first metal layer and a side surface of the second metal layer each defined by the first gap may be substantially perpendicular or inclined to the substrate.
The light-emitting layer may extend onto the first metal layer and the second metal layer.
The second metal layer may include a second through hole through which the substrate is exposed; and a third metal layer formed on the substrate in the second through hole and separated from the second metal layer. A second gap between the second metal layer and the third metal layer may be filled with the light-emitting layer. The second gap may have a second width configured to generate a second electric field enhancement according to a polarization state of the wave when the wave is incident.
The light-emitting layer may extend onto the first metal layer, the second metal layer and the third metal layer.
The third metal layer may include a third through hole through which the substrate is exposed; and a fourth metal layer formed on the substrate in the third through hole and separated from the third metal layer. A third gap between the third metal layer and fourth metal layer may be filled with the light-emitting layer. The third gap may have a third width configured to generate a third electric field enhancement according to a polarization state of the wave when the wave is incident.
The light-emitting layer may onto the first metal layer, the second metal layer and the fourth metal layer.
An image sensing device may include a light conversion device and an image sensor configured to sense visible light emitted from the light conversion device. The light conversion device may include a substrate; a plurality of metal patterns provided on the substrate and separated from each other; a metal layer provided on the substrate and surrounding each of the plurality of metal patterns; a first slit positioned between the metal layer and each of the plurality of metal patterns and surrounding each of the plurality of metal patterns; and a light-emitting layer filling the first slit. The first slit and the metal pattern surrounded by the first slit may be concentric, and the metal layer and the plurality of metal patterns may be aligned so that a first electric field enhancement occurs when a wave belonging to an invisible light band is incident to the first slit. The image sensing device may be used to detect a polarization state of invisible light.
The invisible light band may have a frequency of less than 100 THz.
The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:
Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. The embodiments are merely described below, by referring to the figures, to explain aspects. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
Hereinafter, a terahertz wave-visible light conversion device and an image sensing device including the same according to various embodiments will be described in detail with reference to the accompanying drawings. The drawings are not to scale, and thicknesses of layers and regions may be exaggerated for clarification of the specification. The following embodiments described below are merely illustrative, and various modifications may be possible from the embodiments of the present disclosure. In the layer structures, when an element or layer is referred to as being “on” or “above” another element or layer, the element or layer may be directly on another element or layer or intervening elements or layers. In the drawings, like reference numerals are used to indicate like elements.
First, a terahertz wave-visible light conversion device according to an embodiment is described.
As used in this disclosure, a “terahertz wave-visible light conversion device” may refer to a device that converts a terahertz wave into visible light, and not that converts visible light into a terahertz wave. Accordingly, the “terahertz wave-visible light conversion device” may be expressed as a visible light-emitting device using a terahertz wave.
In addition, because a terahertz wave is a wave outside of the visible light band and is therefore invisible light, the “terahertz wave-visible light conversion device” may be expressed as a device for converting invisible light into visible light or a light conversion device.
In some embodiments, a range of the terahertz waves may be 100 THz or less, for example, 50 THz or less or in a range from about 0.3 THz to about 30 THz, but may not be limited thereto.
Referring to
Because the first metal pattern 120A and the plurality of second metal patterns 120B are separated from each other, there may be a gap 2g1 between the first metal pattern 120A and the plurality of second metal patterns 120B. Each of the second metal patterns 120B may be completely surrounded by the gap 2g1. A width W1 of the gap 2g1 around each of the second metal patterns 120B may be constant. In other words, each of the second metal patterns 120B may be completely surrounded by the gap 2g1 having a constant width W1. In some embodiments, the gap 2g1 may be less than a first diameter D1 of the second metal pattern 120B. In some embodiments, the width W1 of the gap 2g1 may be several micrometers (µm) or less. For example, the width W1 may be several nanometers (nm) to several hundred nanometers, or 1 micrometer or less or 2 micrometers or less. The first diameter D1 of the second metal pattern 120B may be on the order of several tens of nanometers to several hundred micrometers.
The first metal pattern 120A may include a plurality of through holes H1 in the same number as the number of second metal patterns 120B. The plurality of through holes H1 may correspond the plurality of second metal patterns 120B one-to-one. One second metal pattern 120B may be in each through hole H1. Each through hole H1 may be formed to have a second diameter D2. The second diameter D2 may be greater than the first diameter D1. A difference (D2-D1) between the second diameter D2 and the first diameter D1 may correspond to the width W1 of the gap 2g1. In an example embodiment, the center of the through hole H1 may be the same as the center of the second metal pattern 120B. In other words, the center of the through hole H1 and the center of the second metal pattern 120B may coincide with each other. As described above, because the through hole H1 and the second metal pattern 120B have the same center, it may be stated that the through hole H1 and the second metal pattern 120B are concentric.
Because the through hole H1 and the second metal pattern 120B may be concentric circles, the gap 2g1 around the second metal pattern 120B may also be concentric. And, because the width W1 of the gap 2g1 may be at a nanometer level, the gap 2g1 may be regarded as a ring-shaped nanostructure or a nano-coax structure, and may be regarded as a nano-slit having a nano-coax structure.
As a result, the first and second metal patterns 120A and 120B on the substrate 110 may be provided to form a nano-coax structure.
In some embodiments, a geometric shape of each of the second metal patterns 120B on a plane may be circular, but is not limited thereto. For example, the geometric shape of each of the second metal patterns 120B may be non-circular, or may be a polygonal (e.g., quadrangular, etc.) shape.
In some embodiments, the metal layer 120 may include a conductive material, for example, at least one of Au, Al, W, Pt, Mo, Cr, Ti, TiN, AIN, AINd, Ni and Cu, but is not limited thereto. In some embodiments, the metal layer 120 may be a graphene layer or may include graphene. In some embodiments, the material of the first metal pattern 120A may be the same as that of the second metal pattern 120B, but the materials thereof may be different from each other.
The plurality of second metal patterns 120B may be aligned or arranged to have a first pitch P1 in a horizontal direction (e.g., X-axis direction) and/or a vertical direction (e.g., Y-axis direction). The first pitch P1 may correspond to a distance between the centers of two adjacent second metal patterns 120B, but the pitches of the plurality of second metal patterns 120B may be expressed or defined differently. For example, a distance between each starting point of two adjacent second metal patterns 120B arranged in the same direction (e.g., a first direction) may be a third distance D3, and the third distance D3 may be referred to as a pitch of the plurality of second metal patterns 120B. The first direction may be an X-axis direction or a Y-axis direction. The first diameters D1 of the plurality of second metal patterns 120B may be equal to or substantially equal to each other. Also, in the plurality of second metal patterns 120B, intervals between the second metal patterns 120B adjacent to each other in the horizontal and vertical directions may be the same or substantially the same. Accordingly, a distance between the end points of each of two adjacent second metal patterns 120B aligned in the same direction among the plurality of second metal patterns 120B may be equal to the third distance D3.
In some embodiments, the plurality of through-holes H1 may be aligned or arranged to have a second pitch P2 in the horizontal and/or vertical directions. In some embodiments, the second pitch P2 may correspond to a distance between the centers of two adjacent through-holes H1. Accordingly, the second pitch P2 may be equal to or substantially equal to the first pitch P1. In some embodiments, a distance between the plurality of through holes H1 in the first direction and/or the second direction may be greater than an interval (D2-D1) between the first metal pattern 120A and the second metal pattern 120B, that is, the width W1 of the gap 2g1. In some embodiments, the interval of the plurality of through holes H1 in the first and/or second direction may be the same as or substantially the same as the first diameter D1 of the second metal pattern 120B, or may be less than the first diameter D1. The first direction and the second direction may be perpendicular to or substantially perpendicular to each other. In some embodiments, one of the first and second directions may be in the X-axis direction or substantially parallel to the X-axis direction, and the other may be in the Y-axis direction or substantially parallel to the Y-axis direction.
In some embodiments, the light-emitting layer 130 includes a light-emitting material that fills the gap 2g1 between the first metal pattern 120A and the second metal pattern 120B. Accordingly, the light-emitting layer 130 may be expressed as a light-emitting material layer. Because the gap 2g1 is a partial region of the through hole H1, the partial region of the through hole H1 may be expressed as being filled with the light-emitting layer 130. In other words, it may be expressed that a partial region of the through hole H1 may be filled with the light-emitting layer 130, and the remaining area may be filled with the second metal pattern 120B.
In some embodiments, the gap 2g1 may be completely filled with the light-emitting layer 130. In other words, the through hole H1 between the first metal pattern 120A and the second metal pattern 120B may be completely filled with the light-emitting layer 130.
In some embodiments, as in the case of a second terahertz wave-visible light conversion device 200 illustrated in
In some embodiments, as in the case of a third terahertz wave-visible light conversion device 300 shown in
In some embodiments, the light-emitting layer 130 may be or include an electroluminescence layer. In some embodiments, the light-emitting layer 130 may be a quantum dot layer formed of quantum dots or may include quantum dots. In some embodiments, the quantum dots may include a Group II-VI series compound, a Group III-V series compound, and/or a Group IV-VI series compound, but are not limited thereto.
In some embodiments, the Group II-VI series compound may include CdSe, CdTe, CdS, or ZnSe, but is not limited thereto. In some embodiments, the Group III-V compound may include InP, InAs, or InSb, but is not limited thereto. In some embodiments, the Group IV-VI series compound may include PbS or PbSe, but is not limited thereto.
In some embodiments, the quantum dot may include only a single core, but may have a core-shell structure including a core and a shell surrounding the core.
The shell may be expressed as a shell layer, and may completely cover the entire core. The core and the shell may be in direct contact with each other. In the core-shell structure, the core may include a first quantum dot material, and the shell may include a second quantum dot material. “Quantum dot material” may refer to a material forming a quantum dot or a material of the quantum dot. In some embodiments, the first quantum dot material may include a Group II-VI series compound, a Group III-V series compound, and/or a Group IV-VI series compound, but is not limited thereto. In some embodiments, the second quantum dot material may include a Group II-VI series compound, a Group III-V series compound, and/or a Group IV-VI series compound, but may be different from the first quantum dot material. In some embodiments, the second quantum dot material may include CdS, CdTe, or ZnS, but is not limited thereto.
For example,
The first quantum dot 550 may include a first core C11 and a first shell S11. The first shell S11 may surround the entire first core C11 and may be in direct contact with the first core C11. The first shell S11 may be a single layer. A thickness of the first shell S11 may be constant or substantially constant. The second quantum dot 560 may include a second core C22, a first shell S21, and a second shell S22. The first shell S21 may completely surround the second core C22 and is in contact with the second core C22. A thickness of the first shell S21 may be constant or substantially constant. The second shell S22 may surround both the second core C22 and the first shell S21. The second shell S22 may be formed on a surface of the first shell S21, may cover the entire outer surface of the first shell S21, and may be in direct contact with the entire outer surface of the first shell S21. A thickness of the second shell S22 may be constant or substantially constant. In some embodiments, the thicknesses of the first and second shells S21 and S22 may be the same as or different from each other.
In some embodiments, the material of the first core C11 and the material of the second core C22 may be the same, but the materials thereof may be different from each other. In some embodiments, the material of the first and second cores C11 and C22 may include the first quantum dot material described above. In some embodiments, the material of the first shell S11 of the first quantum dots 550 may be different from the material of the first core C11. The material of the first shell S11 may include the second quantum dot material described above. In some embodiments, the materials of the first and second shells S21 and S22 of the second quantum dot 560 may be different from each other, and may include the second quantum dot material. In an example embodiment, the material of the first shell S21 may be different from the material of the second core C22. In some embodiments, the material of the second shell S22 and the material of the second core C22 may be the same as or different from each other. In an example embodiment, the materials of the second core C22, the first shell S21, and the second shell S22 may be different from each other.
When a terahertz wave is incident on the terahertz wave-visible light conversion device, the wavelength of visible light emitted from the light-emitting layer 130 may vary depending on a size and/or constituent material of the quantum dots. As an example, the smaller the size of the quantum dot, the shorter wavelength of the visible light (e.g., blue light) may be emitted from the light-emitting layer 130, and the larger the size of the quantum dot, the longer wavelength of the visible light (e.g., red light) may be emitted from the light-emitting layer 130.
In some embodiments, the light-emitting layer 130 may be a light-emitting material layer for an organic light-emitting diode (OLED) or include a light-emitting material for an OLED (hereinafter, referred to as an ‘OLED material’). In an example embodiment, the OLED material may include an organic light-emitting material, for example, TFB, TAZ, TCTA, TPD and/or PVK, etc., but is not limited thereto.
When the terahertz wave is incident on the visible light conversion device, depending on the OLED material used as the light-emitting layer 130, the type of visible light emitted from the light-emitting layer 130 may vary. For example, when the OLED material is a red light-emitting material, red light may be emitted from the light-emitting layer 130 when a terahertz wave is incident on the terahertz wave-visible light conversion device, and the OLED material may be a green light-emitting material or a blue light-emitting material, green light or blue light may be emitted from the light-emitting layer 130.
In some embodiments, when the light-emitting layer 130 includes quantum dots, the light-emitting layer 130 may include only quantum dots of substantially the same size, or quantum dots of different sizes. When the light-emitting layer 130 includes an OLED material, the light-emitting layer 130 may include only a single color (e.g., red, green, or blue) light-emitting material, but may include a layer in which a plurality of light-emitting materials emitting different visible light are mixed. Accordingly, when a terahertz wave is incident on the terahertz wave-visible light conversion device, according to a selection or combination of materials used as the light-emitting layer 130, visible light of a single color or a substantially single color may be emitted from the light-emitting layer 130, or several types of visible light having different wavelengths from each other may be simultaneously emitted.
As shown in
In some embodiments, the inner wall of the through hole H1 and/or the outer wall of the second metal pattern 120B may not be perpendicular to or substantially perpendicular to the one surface 2S1 of the substrate 110. Accordingly, one side or both sides in the gap 2g1 may not be perpendicular to or substantially not perpendicular to the one surface 2S1 of the substrate 110.
For example,
Referring to
In the fourth terahertz wave-visible light conversion device 400, the inner wall 12S1 of the second through hole H2 and the outer wall 12S2 of the second metal pattern 120B are inclined surfaces, but dimensions, alignment relationships, and alignment types of the first and second metal patterns 120A and 120B may follow the first terahertz-visible light conversion device 100. Accordingly, the light-emitting layer 130 filling a gap around the second metal pattern 120B (i.e., the light-emitting layer 130 filling the second through hole H2 between the first metal pattern 120A and the second metal pattern 120B) may be a ring-shaped nano structure or a nano-coax structure.
When a side surface in the gap 2g1 is an inclined surface, a width of the gap 2g1 may change in a direction perpendicular to the substrate 110 (i.e., according to a depth of the gap 2g1). In this case, a width WT1 of an upper end of the gap 2g1 may be greater than a width WB1 of a lower end. Accordingly, a size of an entrance of the gap 2g1 may be greater than a size of a bottom of the gap 2g1. When the side surface in the gap 2g1 is an inclined surface, the width WT1 of the upper end and the width WB1 of the lower end of the gap 2g1 may fall within a range of the width W1 of the gap 2g1 described with reference to
In some embodiments, the second through hole H2 may be completely filled with the light-emitting layer 130.
However, like a fifth terahertz wave-visible light conversion device 500 shown in
In some embodiments, like a sixth terahertz wave-visible light conversion device 600 shown in
Referring to
The plurality of metal patterns 820 may be arranged in a stripe shape parallel to the Y-axis, and may be aligned to have a third pitch P3 in the X-axis direction. In some embodiments, a size of the third pitch P3 may be the same as or substantially the same as the first pitch P1 of
There may be a plurality of gaps 8g1 between the plurality of metal patterns 820. As a result, the plurality of gaps 8g1 may exist on the substrate 110 together with the plurality of metal patterns 820. The plurality of gaps 8g1 may also be arranged parallel to each other in a stripe shape. Each of the gap 8g1 may correspond to a gap between two adjacent metal patterns 820. A size of the gap 8g1 is less than the first length L1 of the metal pattern 820. In an example embodiment, the gap 8g1 may be less than ½ of the first length L1 of the metal pattern 820, but is not limited thereto. A portion of the substrate 110 may be exposed through the gap 8g1. The gap 8g1 may be filled with a light-emitting layer 830, and a portion of the substrate 110 exposed through the gap 8g1 may be completely covered by the light-emitting layer 830. In some embodiments, one gap 8g1 may be completely filled with the light-emitting layer 830 as shown in
In some embodiments, a size of the gap 8g1 may be the same as or substantially the same as the size of the gap 2g1 described with reference to
In some embodiments, a material (substance) of the metal layer 820 may be the same as that of the metal layer 120 of
In an some embodiments, a material (substance) of the light-emitting layer 830 may be the same as the material of the light-emitting layer 130 described above, but may not be limited to the case.
In
The seventh terahertz wave-visible light conversion device 700 illustrated in
When a terahertz wave polarized in a direction perpendicular to the gap 8g1 is incident on the gap 8g1, a strong field enhancement may occur in the gap 8g1, and thus, even when a terahertz wave with very small photon energy is incident, visible light may be emitted from the light-emitting layer 830. This may denote that the terahertz wave-visible light conversion device has high sensitivity for detecting terahertz waves. In addition, because terahertz wave incident and resulting visible light emission may occur immediately, a rapid terahertz wave detection is possible, and because such detection may be performed at room temperature, use of the device may be free from environmental constraints related to temperature and pressure.
In the seventh terahertz wave-visible light conversion device 700, the metal pattern 820 and the gap 8g1 are aligned parallel to the y-axis, but may be aligned in a direction different from the y-axis. For example, as shown in
When the metal pattern 820 and the gap 8g1 of the seventh terahertz wave-visible light conversion device 700 are aligned as shown in
In some embodiments, the metal pattern 820 and the gap 8g1 of the seventh terahertz wave-visible light conversion device 700, as shown in
When the metal pattern 820 and the gap 8g1 of the seventh terahertz wave-visible light conversion device 700 are aligned at an acute angle with respect to the x-axis as shown in
When the metal pattern 820 and the gap 8g1 of the seventh terahertz wave-visible light conversion device 700 are aligned at an obtuse angle with respect to the x-axis as shown in
As described above, the seventh terahertz wave-visible light conversion device 700 may detect terahertz waves linearly polarized in various directions according to alignment directions of the metal pattern 820 and the gap 8g1.
For convenience of illustration, in
In the first experiment and simulation to obtain the result of
The first experiment and simulation were divided into cases when the size of the gap 8g1 (nano-slit) was 50 nm, 100 nm, 150 nm, 500 nm, and 2 µm, and the same material (e.g., quantum dots) of the light-emitting layer 830 was used.
In
Comparing the first to fourth graphs 11G1 to 11G4, as the size of the gap 8g1 decreases, a threshold intensity of the terahertz wave for exhibiting the electroluminescence of a given intensity lowers.
Referring to
In the second experiment, the seventh terahertz wave-visible light conversion device 700 having nano-slits shown in
In the second experiment, a gap 8g1 of the seventh terahertz wave-visible light conversion device 700 was divided into a case of 100 nm and a case of 2 µm.
In addition, in the second experiment, first to fifth light-emitting layers different from each other were used as the light-emitting layer 830. The first light-emitting layer includes a first quantum dot, the second light-emitting layer includes a second quantum dot, the third light-emitting layer includes a third quantum dot, the fourth light-emitting layer includes a fourth quantum dot, and the fifth light-emitting layer includes TFB, which is an OLED material. The first to fourth quantum dots have different sizes and configurations from each other.
As shown in
The first and second quantum dots a-1 and a-2 emit visible light belonging to a red light (R) band in response to an electric field enhancement caused by an incident terahertz wave. Although the first and second quantum dots a-1 and a-2 both emit visible light belonging to the red light band, sizes (e.g., diameters) D21 and D22 of the first and second quantum dots a-1 and a-2 are different from each other. Accordingly, the size D21 of the first quantum dot a-1 is greater than that of the second quantum dot a-2 (i.e., D21>D22). Therefore, a wavelength of visible light emitted from the first quantum dot a-1 is longer than a wavelength of visible light emitted from the second quantum dot a-2. A core material of the first quantum dot a-1 may include CdSe, and a shell material may include CdS, and thus, the first quantum dot a-1 may emit red visible light having a wavelength of 625 nm. A core material of the second quantum dot a-2 includes CdSe, a material of the first shell S21 includes CdS, and a material of the second shell S22 includes ZnS, and thus, the second quantum dot a-2 may emit red visible light with a wavelength of 605 nm.
The third quantum dot a-3 emits green visible light in response to an electric field enhancement caused by an incident terahertz wave. The size D23 of the third quantum dot a-3 is less than the size D22 of the second quantum dot a-2 (D22>D23). A core material of the third quantum dots a-3 includes CdSeS, and a material of the shell includes ZnS. The third quantum dot a-3 may emit green visible light having a wavelength of 530 nm. The size D24 of the fourth quantum dot a-4 is less than that of the third quantum dot a-3 (D23>D24). The fourth quantum dot a-4 emits blue visible light in response to an electric field enhancement caused by an incident terahertz wave. A core material of the fourth quantum dot a-4 includes CdS, a material of the shell S41 includes ZnS, and thus, the fourth quantum dot a-4 may emit blue visible light having a wavelength of 480 nm.
In
In
In
These results indicate that, when the gap 8g1 is constant (i.e., when the size of the nano-slit is constant, even when quantum dot layers having different sizes and/or configurations are used as the light-emitting layer 830) there is no significant difference in the terahertz wave threshold intensity, at which electroluminescence occurs.
In
A fifth graph 12G5 in
Comparing the fifth to eighth graphs 12G5 to 12G8 in
In
A third photo 13P3 at an upper center is an enlarged photo of an area limited by the rectangular box of the first photo 13P1, and a fourth photo 13P4 at a lower center is a square box of the second photo 13P2, and is an enlarged picture of a limited area.
In the third photo 13P3, reference numeral 13M1 denotes one metal pattern, and 13R1 denotes a ring-shaped nano-slit surrounding the one metal pattern 13M1, that is, a nano-slit having a nano-coax structure. In a fourth photograph 13P4, reference numeral 13M2 denotes one metal pattern, and 13R2 denotes a nano-slit of a nano-coax structure that completely surrounds the one metal pattern 13M2. The metal layer outside the nano-slits 13R1 and 13R2 corresponds to the first metal pattern 120A of
A fifth photo 13P5 at an upper right is an enlarged photo of the limited area (see square box) of the third photo 13P3, and a sixth photo 13P6 at a lower right is an enlarged photo of the limited area (see square box) of the fourth photo 13P4.
The fifth and sixth photos 13P5 and 13P6 clearly show the nano-slit (gap) having the nano-coax structure.
A simulation was performed to confirm whether a field enhancement occurs on a nano-slit having a nano-coax structure when a terahertz wave is incident on the terahertz wave-visible light conversion device shown in
A third photo 13BP3 in an upper right of
Referring to the first and second photos 13BP1 and 13BP2 of
The field enhancement causes electroluminescence of the nano-slit. That is, when a light-emitting layer is present in the nano-slit, a material of the light-emitting layer is in an excited state due to the field enhancement. A material of the light-emitting layer in an excited state becomes in its original stable state while emitting visible light, and various colors of visible light may be emitted according to the type of the material used as the light-emitting layer.
As a result, a portion where a field enhancement occurs in the nano-slit may be generally a portion where the electroluminescence occurs (i.e., a portion where visible light is emitted).
In the third experiment, two terahertz wave-visible light conversion devices were used. One of the two terahertz wave-visible light conversion devices corresponds to the first photograph 13P1 of
In the third experiment, in consideration of the size of the nano-slits of the two terahertz wave-visible light conversion devices, a horizontally polarized terahertz wave having a first intensity was incident on the terahertz wave-visible light conversion device having a nano-slit size of 100 nm, and a horizontally polarized terahertz wave having a second intensity was incident on the terahertz wave-visible light conversion device having a nano-slit size of 1 µm. The first intensity is about 40 kV/cm, and the second intensity is about 80 kV/cm.
In the third experiment, quantum dots having a core-shell structure emitting red light were used as the light-emitting layer filling the nano-slits, for example, quantum dots, in which a core material is CdSe, a material of the first shell is CdS, and a material of the second shell is ZnS, were used.
In
Referring to the first and second photos 13CP1 and 13CP2, visible light-emitting regions LB1 and LB2 exist in both of the two terahertz wave-visible light conversion devices. The first light-emitting region LB1 corresponds to the position of the nano-slit having a gap of about 100 nm, and the second light-emitting region LB2 corresponds to the position of the nano-slit having a gap of about 1 µm.
In addition, because the incident terahertz wave is a wave polarized in the horizontal direction (x-axis direction), it may be seen that the light-emitting regions LB1 and LB2 are along the nano-slits with the nano-slit portion perpendicular to the polarization direction (x-axis direction) as the center, and are not in the nano-slit portion horizontal to the polarization direction (the nano-slit portion perpendicular to the y-axis direction). A relationship between the polarization state of the incident terahertz wave and the light-emitting region provides information about the polarization state of the incident terahertz wave. That is, by observing the light-emitting region of visible light emitted from the terahertz wave-visible light conversion device, it is possible to obtain information for the polarization state of a terahertz wave incident on the terahertz wave-visible light conversion device. For example, when the incident terahertz wave is polarized in the vertical direction (y-axis direction), the first and second light-emitting regions LB1 and LB2 are rotated to the left or right by 90°.
The positions of the first and second light-emitting regions LB1 and LB2 correspond to the field enhancement region described with reference to
Visible light emitted from the first and second light-emitting regions LB1 and LB2 is emitted from the light-emitting layer filling the nano-slits of the nano-coax structure. In the second experiment, the light-emitting layer includes quantum dots.
When reviewing a process of emitting visible light from the light-emitting layer, as shown in
Referring to
In
Comparing the first and second graphs 13G1 and 13G2, in the gap of the nano-coax structure, it may be seen that the smaller the gap size, the lower the threshold intensity of the terahertz wave for electroluminescence, and the larger the gap size, the higher the threshold intensity.
In the third experiment, an experiment (hereinafter, a fourth experiment) was also performed on the change in electroluminescence when the size of the nano-slit was the same and the shape of the nano-slit was changed.
In the fourth experiment, a terahertz wave-visible light conversion device having a nano-slit (gap) of a first shape (hereinafter, a first device) and a terahertz wave-visible light conversion device having a nano-slit of a second shape different from the first shape (hereinafter, a second device) was used.
The first type of nano-slit may be a nano-slit having a nano-coax structure, and the second type of nano-slit may be a linear or striped nano-slit. The size of the nano-slits in the first and second devices was maintained as constant or substantially constant to about 100 nm. In addition, in the fourth experiment, the nano-slits of the first and second devices were all filled with the same light-emitting material (e.g., quantum dots).
The fourth experiment was performed in the order that terahertz waves were incident on the first and second devices, and visible light emitted from the light-emitting material filling the nano-slits of each device was measured. The intensity of the terahertz wave incident on the first and second devices was the same.
In
In
Comparing the first and second graphs 14G1 and 14G2 of
In
In the unit pattern, the one second metal pattern 120B may be divided into a plurality of metal patterns. In other words, the one second metal pattern 120B may be configured to include a plurality of metal patterns separated from each other.
For example, as shown in
In some embodiments, materials of the first and second metal portions 19a and 19b may be the same or different from each other. For example, materials used for the first and second metal portions 19a and 19b may be the same or different from each other within a range of materials used for the second metal pattern 120B.
In some embodiments, dimensions and characteristics of the gap 19g1 may be the same as those of the gap 2g1 of
The gap 19g1 is filled with the light-emitting layer 1930. The gap 19g1 may be completely filled or may be partially filled with the light-emitting layer 1930. The degree of filling the gap 19g1 with the light-emitting layer 1930 may follow the example of filling the gap 2g1 with the light-emitting layer 130 described with reference to
An inner surface of the gap 19g1, that is, the inner surface of the cylindrical through hole existing between the first and second metal portions 19a and 19b, may be perpendicular to or substantially perpendicular to the substrate 110 like the side surface of the through hole H1 in
In some embodiments, a material and configuration of the light-emitting layer 1930 may follow the case of the light-emitting layer 130 described with reference to
In some embodiments, for example, as shown in
In some embodiments, the first to third metal portions 20a to 20c may be separated from each other and without contacting each other. A mutually spaced interval (distance) between the first to third metal portions 20a to 20c in a given direction may be the same, but may be different from each other.
The first metal portion 20a may be positioned inside the second metal portion 20b, and the second metal portion 20b may completely surround a circumference of the first metal portion 20a. The second metal portion 20b may be positioned inside the third metal portion 20c, and a circumference of the second metal portion 20b may be completely surrounded by the third metal part 20c. The second and third metal portions 20b and 20c may have a cylindrical shape having a given thickness in a radial direction. In some embodiments, the thickness of the second metal portion 20b in a radial direction may be the same as or different from the thickness of the third metal portion 20c. The thickness of the second metal portion 20b and/or the third metal portion 20c may be the same as or different from a diameter of the first metal portion 20a.
In some embodiments, a material of the first to third metal portions 20a to 20c may be the same as the material of the second metal pattern 120B. In some embodiments, materials used for the first to third metal portions 20a to 20c may be the same or different from each other within a range of materials used for the second metal pattern 120B.
A spacing interval between the first metal portion 20a and the second metal portion 20b may correspond to the first gap 20g1, and a spacing interval between the second metal portion 20b and the third metal portion 20c may corresponds to the second gap 20g2. Thicknesses of the first and second gaps 20g1 and 20g2 in the radial direction may be equal to each other. The thickness may be expressed as a width. A thickness in the radial direction of the first and second gaps 20g1 and 20g2 may be the same as a width of the gap 2g1 of
The centers of the first to third metal portions 20a to 20c may be at the same position. Accordingly, the first to third metal portions 20a to 20c may be concentric circles. Accordingly, the first and second gaps 20g1 and 20g2 may also be concentric, and the thickness of the first and second gaps 20g1 and 20g2 may fall within a range of the width W1 of the gap 2g1 of
The first gap 20g1 may be filled with a first light-emitting layer 2030a, and the second gap 20g2 may be filled with a second light-emitting layer 2030b. The degree of filling the first gap 20g1 with the first light-emitting layer 2030a and the degree of filling the second gap 20g2 with the second light-emitting layer 2030b may follow the degree of filling the gap 2g1 with the light-emitting layer 130 described with reference to
Because the first and second light-emitting layers 2030a and 2030b may fill the first and second gaps 20g1 and 20g2, respectively, the first and second light-emitting layers 2030a and 2030b may also be concentric and have a nano-coax structure.
Materials of the first and second light-emitting layers 2030a and 2030b may be the same as or different from each other, and may be within a range of materials used as the light emitting layer 130 of
Side surfaces of the first and second gaps 20g1 and 20g2 seen in a cross section of the first to third metal portions 20a to 20c in a direction perpendicular to the upper surface of the substrate 110 on which the first to third metal portions 20a to 20c are formed may be perpendicular to or substantially perpendicular to the upper surface of the substrate 110, but may be inclined surfaces like the side surfaces of the second through hole H2 shown in
The morphological relationship between the first to third metal portions 20a to 20c and the first and second gaps 20g1 and 20g2 may represent a structure in which a through hole (hereinafter, an outer through hole) through which the substrate 110 is exposed exists in the third metal portion 20c, the second metal portion 20b separated from the third metal portion 20c exists in the outer through hole, a through hole (hereinafter, an inner through hole) through which the substrate 110 is exposed exists in the second metal portion 20b, and the first metal portion 20a separated from the second metal portion 20b exists in the inner through hole. The centers of the first to third metal portions 20a to 20c and the centers of the inner and outer through holes may all be at the same position.
The thicknesses in the radial direction of the first and second gaps 20g1 and 20g2 may be constant or different from each other. For example, as shown in
The eighth terahertz wave-visible light conversion device 800 is a case in which the second metal pattern 120B inside the gap 2g1 in the first terahertz wave-visible light conversion device 100 of
In the first terahertz wave-visible light conversion device 100 of
When the second metal pattern 120B in the first terahertz wave-visible light conversion device 100 of
In the eighth terahertz wave-visible light conversion device 800 illustrated in
In all of the spiral nano-coax structures in
Because the light-emitting layer is filled in a gap, the positions of the gap and the light-emitting layer on a plane may be the same. Accordingly, in
Next, an image sensing device including the terahertz wave-visible light conversion device described above is described. An image sensing device, which will be described later, may be an image sensor, may detect a terahertz wave, and may also acquire information on a polarization state of the terahertz wave. Accordingly, the image sensing device to be described later may be viewed as a terahertz wave polarization detector or a polarization measuring device.
Referring to
The terahertz wave-visible light conversion device 2410 may be provided on the light incident side of the image sensor 2420, but is not limited thereto. The terahertz wave-visible light conversion device 2410 may be one of the various terahertz wave-visible light conversion devices described above, for example, the first to eighth terahertz wave-visible light conversion devices 100, 200, 300, 400, 500, 600, 700, and 800.
In some embodiments, the terahertz wave-visible light conversion device 2410 may be configured by combining two or more of the first to eighth terahertz wave-visible light conversion devices 100, 200, 300, 400, 500, 600, 700, 800. This will be described later.
The image sensor 2420 may be a device for sensing visible light emitted from the terahertz wave-visible light conversion device 2410. Visible light emitted from the terahertz wave-visible light conversion device 2410 may include information about the intensity of the terahertz wave and information about the polarization state as described in the experimental results of
As it may be seen from the experimental results of
Accordingly, a region of the terahertz wave-visible light conversion device 2410, from which visible light is emitted, may be limited according to a polarization state of a terahertz wave incident on the terahertz wave-visible light conversion device 2410. Therefore, the intensity and polarization state of the terahertz wave incident on the terahertz wave-visible light conversion device 2410 may be seen by measuring the visible light emitted from the terahertz wave-visible light conversion device 2410 with the image sensor 2420. The visible light measurement may denote measuring an image of a region of the terahertz wave-visible light conversion device 2410, where visible light is emitted.
In some embodiments, the image sensor 2420 may include an image sensor such as a charge coupled device (CCD) or a CMOS image sensor (CIS).
Because the substrate 24A is transparent to terahertz waves and visible light, as shown in
The terahertz wave-visible light conversion device 2410 may be disposed between components included in the image sensor 2420, for example, as shown in
In the case of
Also, in the structure illustrated in
In some embodiments, in the image sensing device 2400 illustrated in
In addition, in
In some embodiments, as shown in
Referring to
Considering the alignment directions of the metal pattern 820 and the gap 8g1 of each of the first to fourth portions A11, A22, A33, and A44, the first portion A11 may be a nano-slit for detecting a vertically polarized terahertz wave, the second portion A22 may be a nano-slit for detecting terahertz wave polarized at an obtuse angle (e.g., 135°) with respect to the x-axis, the third portion A33 may be a nano-slit for detecting a horizontally polarized terahertz wave, and the fourth portion A44 may be a nano-slit for detecting a terahertz wave polarized at an acute angle (e.g., 45°) with respect to the x-axis.
As a result, the visible light generating layer 24B including the first to fourth portions A11, A22, A33, and A44 may be used to detect terahertz waves having linear polarization angles of 0°, 45°, 90°, and 135°.
The first to fourth portions A11, A22, A33, and A44 may form one pixel for measurement of polarized light. The pixel may correspond to one of the pixels included in the image sensor 24A.
The visible light generating layer 24B may include a plurality of pixels for measurement of polarized light. Accordingly, the visible light generating layer 24B may be expressed as a pixel layer for measurement of polarized light.
Stoke vectors for the first to fourth portions A11, A22, A33, and A44 constituting one pixel may be calculated to obtain the degree of linear polarization (DoLP) of a terahertz wave and angle of linear polarization (AoLP) may be measured, and may be directly imaged through the image sensor 2420.
In traditionally used conventional methods, it was inconvenient and cumbersome because the polarizing plate had to be rotated to secure a polarization angle. However, in the case of the illustrated image sensing device 2400, a polarization state of the terahertz wave may be directly imaged by using the visible light generating layer 24B.
The DoLP and the AoLP of a terahertz wave incident on the first to fourth portions A11, A22, A33, and A44 of the visible light generating layer 24B may be calculated by the following Equations 1 and 2, respectively.
In Equations 1 and 2, S1, S2, and S0 may be obtained from the following Stokes vectors S for the first to fourth portions A11, A22, A33, and A4 forming a pixel.
Stoke Vector
In the above Stokes vector, I0 denotes the intensity of a terahertz wave having a linear polarization angle of 0°, and I90 denotes an intensity of a terahertz wave having a linear polarization angle of 90°. I45 denotes the intensity of a terahertz wave having a linear polarization angle of 45°, and I135 denotes an intensity of a terahertz wave having a linear polarization angle of 135°. ILHC represents the intensity of a terahertz wave having left-handed polarization, and IRHC represents the intensity of a terahertz wave having right-handed polarization.
Considering the Stoke vector and Equations 1 and 2, by measuring the intensities according to the polarization state of the terahertz wave incident on the visible light generating layer 24B, the DoLP and the AoLP of the incident terahertz wave may be calculated.
In the light conversion device for detecting a terahertz wave according to an embodiment, a plurality of metal patterns are arranged to form nano-slits (gaps), the nano-slits have a width at which a field enhancement strongly occurs according to the polarization state of an incident terahertz wave, and the nano-slit is filled with a light-emitting layer that emits visible light due to the field enhancement. Accordingly, even when a terahertz wave having very small photon energy is incident, visible light may be emitted from the light-emitting layer by a field enhancement. Thus, when a light conversion device according to an embodiment is used, high sensitivity to a terahertz wave may be secured.
In addition, in the case of the disclosed light conversion device, an emission region of visible light may vary according to a polarization state of a terahertz wave. Therefore, by combining the disclosed light conversion device with a visible light image sensor, information on a polarization state (e.g., polarization intensity, polarization angle) of an incident terahertz wave may be readily obtained, and the information may be directly imaged.
In addition, the detection of a terahertz wave using the disclosed device may be performed at atmospheric pressure and room temperature, and thus, it may be free from an environment in which temperature and pressure are extremely limited.
It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2022-0083162 | Jul 2022 | KR | national |
This application claims the benefit of U.S. Provisional Application No. 63/281,335, filed on Nov. 19, 2021, in the US Pat. Office and Korean Patent Application No. 10-2022-0083162, filed on Jul. 06, 2022, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entireties by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63281335 | Nov 2021 | US |
