Patent Application
20130128366
This application claims priority under 35 USC §119 to Korean Patent Application No. 2011-0119947, filed on Nov. 17, 2011 in the Korean Intellectual Property Office (KIPO), the contents of which are herein incorporated by reference in their entirety.
1. Technical Field
Example embodiments relate generally to antennas, and more particularly to optical nanoantennas.
2. Description of the Related Art
An optical antenna, as a miniaturization of radio antenna, may convert freely propagating optical radiation into localized fields and vice versa, and may be widely used in the fields of nanosciences. In particular, a plasmonic nanoantenna, which is a kind of an optical nanoantenna, can engineer confinement and absorption of light into specific targets of a nanosize and can control emission properties and even transition lifetimes of fluorescent molecules or photoluminescent quantum dots interfaced with the antenna. Recently, various plasmonic nanoantennas have been researched and developed.
However, a conventional plasmonic nanoantenna, which employs small metallic nanostructures such as bow-ties or nanoparticles, has only a single resonance with a finite spectral width. For optimum interface with the radiation field, a plasmonic nanoantenna may need to play a dual role as a receiver and a transmitter at the same time, for which the operating frequencies can be different. Furthermore, multiwavelength channels may be required in broadband nano-optical spectroscopy as well as in biochemical sensing employing multiple emitters operating at different colors. Accordingly, a plasmonic nanoantenna is required to reliably operate at multiple resonances in the full visible range.
Accordingly, the inventive concept is provided to substantially obviate one or more problems due to limitations and disadvantages of the related art.
Some example embodiments provide an optical nano antenna using a single-crystalline silver nanowire.
Some example embodiments provide a method of manufacturing an optical nanoantenna using a single-crystalline silver nanowire.
Some example embodiments provide an optical nanoantenna using a single-crystalline metal nanowire.
According to example embodiments, an optical nanoantenna includes a single-crystalline silver (Ag) nanowire. The single-crystalline silver nanowire is configured to output an optical antenna radiation pattern based on incident lights. The optical antenna radiation pattern includes multilobe radiation patterns, and each multilobe radiation pattern has a plurality of lobes that are radially disposed centered on the single-crystalline silver nanowire. The incident lights are visible lights in entire visible wavelength bands.
In an example embodiment, the incident lights may include a first light signal having a first wavelength and a second light signal having a second wavelength shorter than the first wavelength. The optical antenna radiation pattern may include a first multilobe radiation pattern emitted based on the first light signal and a second first multilobe radiation pattern emitted based on the second light signal.
A first distance between adjacent two lobes of the plurality of lobes in the first multilobe radiation pattern may be longer than a second distance between adjacent two lobes of the plurality of lobes in the second multilobe radiation pattern.
In an example embodiment, the optical antenna radiation pattern may be generated by converting the incident lights into surface plasmonic polariton (SPP) currents and by reflecting the SPP currents at both ends of the single-crystalline silver nanowire.
In an example embodiment, the single-crystalline silver nanowire may be synthesized by a vapor transportation method.
The single-crystalline silver nanowire may be synthesized by thermally evaporating a silver slug in a furnace to generate a silver vapor, by transporting the silver vapor to a single-crystalline substrate using an inert gas, and by growing the single-crystalline silver nanowire on the single-crystalline substrate, and wherein the single-crystalline substrate is located in the furnace and has a temperature lower than a temperature of the silver slug.
According to example embodiments, in a method of manufacturing an optical nanoantenna including a single-crystalline silver (Ag) nanowire, a silver slug is thermally evaporated in a furnace to generate a silver vapor. The silver vapor is transported to a single-crystalline substrate using an inert gas. The single-crystalline substrate is located in the furnace and has a temperature lower than a temperature of the silver slug. The single-crystalline silver nanowire is grown on the single-crystalline substrate. The single-crystalline silver nanowire outputs an optical antenna radiation pattern based on incident lights. The optical antenna radiation pattern includes multilobe radiation patterns, and each multilobe radiation pattern has a plurality of lobes that are radially disposed centered on the single-crystalline silver nanowire. The incident lights are visible lights in entire visible wavelength bands.
In an example embodiment, the single-crystalline silver nanowire may have a face-centered cubic structure and may be grown in a [110] crystalline direction.
According to example embodiments, an optical nanoantenna includes a single-crystalline silver (Ag) nanowire. The single-crystalline silver nanowire is configured to output an optical antenna radiation pattern based on incident lights. The optical antenna radiation pattern includes multilobe radiation patterns, and each multilobe radiation pattern has a plurality of lobes that are radially disposed centered on the single-crystalline silver nanowire. The incident lights include infrared lights in entire infrared wavelength bands, visible lights in entire visible wavelength bands, and ultraviolet lights in entire ultraviolet wavelength bands.
In an example embodiment, the incident lights may include a first light signal having a first wavelength and a second light signal having a second wavelength shorter than the first wavelength. The optical antenna radiation pattern may include a first multilobe radiation pattern emitted based on the first light signal and a second first multilobe radiation pattern emitted based on the second light signal.
A first distance between adjacent two lobes of the plurality of lobes in the first multilobe radiation pattern may be longer than a second distance between adjacent two lobes of the plurality of lobes in the second multilobe radiation pattern.
According to example embodiments, an optical nanoantenna includes a single-crystalline metal nanowire. The single-crystalline metal nanowire is configured to output an optical antenna radiation pattern based on incident lights. The optical antenna radiation pattern includes multilobe radiation patterns, and each multilobe radiation pattern has a plurality of lobes that are radially disposed centered on the single-crystalline metal nanowire. The incident lights are visible lights in entire visible wavelength bands.
In an example embodiment, the incident lights may include a first light signal having a first wavelength and a second light signal having a second wavelength shorter than the first wavelength. The optical antenna radiation pattern may include a first multilobe radiation pattern emitted based on the first light signal and a second first multilobe radiation pattern emitted based on the second light signal.
A first distance between adjacent two lobes of the plurality of lobes in the first multilobe radiation pattern may be longer than a second distance between adjacent two lobes of the plurality of lobes in the second multilobe radiation pattern.
In an example embodiment, the single-crystalline metal nanowire may be synthesized using gold (Au), platinum (Pt), palladium (Pd) or aluminum (Al).
Accordingly, the optical nanoantenna according to example embodiments may output the multilobe-shaped optical antenna radiation patterns, may operate at multiple resonances in the full visible range. The optical nanoantenna according to example embodiments may efficiently transmit and receive optical signals.
Illustrative, non-limiting example embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.
Various example embodiments will be described more fully with reference to the accompanying drawings, in which embodiments are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like reference numerals refer to like elements throughout this application.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of the inventive concept. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.).
The terminology used herein is for the purpose of describing particular embodiments and is not intended to be limiting of the inventive concept. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
An optical nanoantenna according to example embodiments may be implemented using a single-crystalline silver (Ag) nanowire. The silver has no interband electronic transition at visible wavelength bands (e.g. from about 430 nm to about 700 nm), and a sufficiently long metal nanowire may support multiple surface plasmon polariton (SPP) resonances in a relatively wide spectral range. Thus, the optical nanoantenna using a silver nanowire may operate at multiple resonances in the full visible range.
A silver nanowire synthesized by a conventional method has a relatively rough surface, and performances of the optical nanoantenna implemented using the conventional silver nanowire may be degraded due to the relatively rough surface. As described later with reference to
Hereinafter, the optical nanoantenna according to example embodiments will be described based on the single-crystalline silver nanowire. However, the optical nanoantenna according to example embodiments may be implemented using a single-crystalline metal nanowire that is synthesized using at least one of various metals. For example, the single-crystalline metal nanowire may be synthesized using gold (Au), platinum (Pt), palladium (Pd) or aluminum (Al).
Referring to
The quartz tube 12 may be horizontally disposed with respect to the ground. For example, the quartz tube 12 may have a diameter of about 1 inch. The alumina boat 14 may be disposed at a front part of the quartz tube 12. A precursor, e.g., a silver slug 16, may be inserted in the quartz tube 12 using the alumina boat 14. The single-crystalline substrate 18, e.g., a sapphire substrate, may be disposed at a back part of the quartz tube 12. The single-crystalline silver nanowire may be generated on the single-crystalline substrate 18. An inert gas, e.g., an argon (Ar) gas, may be injected into the front part of the quartz tube 12, may flow through the quartz tube 12, and may be exhausted from the back part of the quartz tube 12. Although not illustrated in
The single-crystalline silver nanowire may be synthesized by thermally evaporating the precursor (e.g., the silver slug 16) in the furnace 10 to generate a silver vapor, by transporting the silver vapor to the single-crystalline substrate 18 using the inert gas, and by growing the single-crystalline silver nanowire on the single-crystalline substrate 18. The single-crystalline substrate 18 may have a temperature lower than a temperature of the silver slug 16. For example, a heating zone 20 in the furnace 10 may be heated to a temperature of about 800° C., the inert gas may flow through the quartz tube 12 at about 100 sccm, a distance between the alumina boat 14 and the single-crystalline substrate 18 may be about 5 cm, a pressure in the furnace 10 may be about 5 to 15 torr, and a reaction time may be about 30 minutes.
Referring to
Because surface plasmons exist very close to a metal/dielectric interface, SPP propagation at the metal/dielectric interface is improved as the metal/dielectric surface becomes smooth. The metal or dielectric with the single-crystalline structure has an electrical conductivity higher than an electrical conductivity of the metal or dielectric with the poly-crystalline structure. Moreover, scattering loss gets higher at the shorter wavelength. Accordingly, the optical nanoantenna using the single-crystalline silver nanowire may support the SPP propagation without the scattering loss and may operate in the full visible range.
Referring to
The optical antenna radiation pattern 110 may be generated by converting the incident lights into charge density waves (CDWs), e.g., SPP currents 120, and by reflecting the SPP currents 120 at both ends of the single-crystalline silver nanowire 100. In other words, the incident light excites the SPP currents 120, which propagate back and forth along a surface of the single-crystalline silver nanowire 100 by reflecting at both ends of the single-crystalline silver nanowire 100. According to the antenna theory, the SPP currents 120 propagating toward both ends of the single-crystalline silver nanowire 100 form a standing wave in time-harmonic motion, and time-varying currents of charges in the single-crystalline silver nanowire 100 create radiations, even if the single-crystalline silver nanowire 100 is straight. Therefore, unique multilobe radiation patterns may be generated and observed by SPP standing currents on the single-crystalline silver nanowire 100. Because the charge-density waves (e.g., the SPP currents 120) are generated along the surface of the single-crystalline silver nanowire 100, the polarization of the optical antenna radiation pattern 110 may be parallel to the long axis of the single-crystalline silver nanowire 100, as described later with reference to
Referring to
The optical antenna radiation pattern 110′ includes multilobe radiation patterns 112, 114 and 116. Each multilobe radiation pattern has a plurality of lobes that are radially disposed centered on the single-crystalline silver nanowire 100. For example, the optical antenna radiation pattern 110′ may include a first multilobe radiation pattern emitted based on the first light signal and a second first multilobe radiation pattern emitted based on the second light signal. A first distance between adjacent two lobes of the plurality of lobes in the first multilobe radiation pattern may be longer than a second distance between adjacent two lobes of the plurality of lobes in the second multilobe radiation pattern. In other words, a distance between adjacent two lobes in a single multilobe radiation pattern may be short as a wavelength of a light signal corresponding the single multilobe radiation pattern becomes short.
For example, a distance d1 between adjacent two lobes (e.g., two red lobes) in a multilobe radiation pattern 112 emitted based on the red light RL may be longer than a distance d2 between adjacent two lobes (e.g., two green lobes) in a multilobe radiation pattern 114 emitted based on the green light GL. The distance d2 between adjacent two lobes (e.g., two green lobes) in the multilobe radiation pattern 114 emitted based on the green light GL may be longer than a distance d3 between adjacent two lobes (e.g., two blue lobes) in a multilobe radiation pattern 116 emitted based on the blue light BL.
The optical nanoantenna according to example embodiments may output the optical antenna radiation pattern from the single-crystalline silver nanowire 100 based on the visible lights in the entire visible wavelength bands. Accordingly, as illustrated in
Although
Referring to
The single-crystalline silver nanowire 100 included in the optical nanoantenna may be placed on the glass substrate 34. The incident lights may be provided from a white light source or a laser source having a specific color, and may be concentrated by the lens 32. The incident lights concentrated by the lens 32 may be injected into the single-crystalline silver nanowire 100 at an angle θ of about 80° with respect to the normal direction of glass substrate 34. The objective lens 36 may be a dry type objective lens, and may have a magnification of about 1000 and a numerical aperture (NA) of about 0.7. When the incident angle (e.g., about 80°) of light is greater than the angle of the numerical aperture of the objective lens 36, an environment of a dark-field optical microscope may be set up, the SPP antenna radiation may be separated from light that is directly reflected by the glass substrate 34, and thus only the SPP antenna radiation (e.g., the optical antenna radiation pattern) may be detected. The linear polarizer 38 on the objective lens 36 may determine the polarization states of the optical antenna radiation pattern. The radiation patterns may be measured by CCD camera 40 with respect to a first direction “∥” parallel to the single-crystalline silver nanowire 100 and a second direction “⊥” perpendicular to the single-crystalline silver nanowire 100.
Referring to
Although some patterns are blurredly measured due to the numerical aperture and limited resolution of the objective lens 36 in
A distance between adjacent two lobes in a single multilobe radiation pattern may be short as a wavelength of a light signal corresponding the single multilobe radiation pattern becomes short. For example, a distance between adjacent two red lobes (e.g., adjacent two lobes in the multilobe radiation pattern emitted based on the red light having the wavelength of about 633 nm) may be about 600 nm. A distance between adjacent two green lobes (e.g., adjacent two lobes in the multilobe radiation pattern emitted based on the green light having the wavelength of about 532 nm) may be about 510 nm. A distance between adjacent two blue lobes (e.g., adjacent two lobes in the multilobe radiation pattern emitted based on the blue light having the wavelength of about 440 nm) may be about 420 nm. The distances between adjacent two lobes are shorter than the free-space light wavelengths, reflecting the sub-wavelength-scale properties of the SPP antenna modes.
Referring to
As described above with reference to
Referring to
Similarly to
As described with reference to
Referring to
As described above, as the 1-dimensional (1-D) SPP cavity, the optical nanoantenna using the single-crystalline silver nanowire supports its resonance modes by reflecting the SPP currents at both ends of the single-crystalline silver nanowire. The propagation wavelength of the SPP currents, e.g., λSPP, in the cavity are given by the waveguide modes of the single-crystalline silver nanowire, which depends on a diameter of the single-crystalline silver nanowire. The resonance condition of the optical nanoantenna using the single-crystalline silver nanowire is determined by a length of the single-crystalline silver nanowire, which is slightly shifted from the multiples of λSPP/2, because the ends of the single-crystalline silver nanowire are not rigid mirrors. In a sufficiently long optical nanoantenna, several resonance modes can exist over the full visible frequency range. When the SPP currents are excited by a white light source, distinct conditions for each resonance make radiating near-field lobes appear at different locations of the single-crystalline silver nanowire. Accordingly, the single-crystalline silver nanowire may output the optical antenna radiation pattern such that the multilobe radiation patterns emitted based on various visible lights are overlapped, as illustrated in
Although the optical nanoantenna according to example embodiments is mainly described to operate based on the visible lights, the optical nanoantenna may operate based on the incident lights including infrared lights, the visible lights and ultraviolet lights. In other words, the optical nanoantenna according to example embodiments includes a single-crystalline silver nanowire configured to output an optical antenna radiation pattern based on incident lights. The incident lights include the infrared lights in entire infrared wavelength bands, the visible lights in entire visible wavelength bands, and the ultraviolet lights in entire ultraviolet wavelength bands. The optical antenna radiation pattern includes multilobe radiation patterns, and each multilobe radiation pattern has a plurality of lobes that are radially disposed centered on the single-crystalline silver nanowire. In this embodiment, as described with reference to
Although the optical nanoantenna according to example embodiments is mainly described to include the single-crystalline silver nanowire, the optical nanoantenna may include a single-crystalline metal nanowire that is synthesized using at least one of various metals, such as gold (Au), platinum (Pt), palladium (Pd) or aluminum (Al).
The above described embodiments may be applied to a device and an electronic system having the optical nanoantenna. For example, the above described embodiments may be applied to applications in nano-optical spectroscopy, high-resolution nanoimaging, photovoltaics, and nonlinear signal conversion.
The foregoing is illustrative of example embodiments and is not to be construed as limiting thereof. Although a few example embodiments have been described, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from the novel teachings and advantages of the present inventive concept. Accordingly, all such modifications are intended to be included within the scope of the present inventive concept as defined in the claims. Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and is not to be construed as limited to the specific example embodiments disclosed, and that modifications to the disclosed example embodiments, as well as other example embodiments, are intended to be included within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2011-0119947 | Nov 2011 | KR | national |
