Exemplary embodiments of the disclosure relate to an optical device using semiconductors, more particularly, to an optical device for selective transmission of lights or optical signals to a first waveguide or a second waveguide, using a reflector formed of silicon materials.
Structures for optical modulator to modulate light signals and optical switch to switch light paths are published based on the control of light reflection with a small angle (Korean Patent No. 10-2010-0066834, hereinafter, “Cited Reference 1”). However, Cited Reference 1 only proposes basic structures of reflectors for reflection or refraction of light and did not disclose a semiconductor-based structure for a semiconductor device for transmission of light signals in semiconductor chip etc.
Prior inventions propose structures of p-n junctions and waveguides to control refractive index of silicon used most in other semiconductors (U.S. Pat. No. 7,116,853, U.S. Pat. No. 7,751,654 and U.S.P. 2011/0058765). Those prior inventions have an object to control the speed of light in a waveguide, in other words, control the phase of light wave.
Exemplary embodiments of the present disclosure provide an optical device using semiconductors, which can achieve control of light refraction or reflection based on the silicon semiconductor having p-n junction and waveguide structures.
Exemplary embodiments of the present disclosure also provide an optical device using a semiconductor, which may directly modulate the amplitude of light by control of reflection or refraction.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an optical device includes a first waveguide in which an optical signal is incident along the same direction with the first waveguide; a second waveguide forming a preset angle from the first waveguide; and a reflector where the refractive index is varied by an applied voltage to select a path of the optical signal to the first waveguide or the second waveguide, wherein the reflector includes a first interface partially in contact with the first waveguide, with the optical signal incident therein; and a second interface partially in contact with the first waveguide, with the optical signal transmitted there through, and the reflector is a semiconductor element having a p-type or n-type impurity doped therein.
The refractive index of the reflector can be varied by applying a voltage o a region of the reflector where a p-type impurity or an n-type impurity is doped, and a p+-type impurity may be further doped near the region where the p-type impurity is doped and a n+-type impurity may be further doped near the region where and the n-type impurity is doped, to apply a voltage to the region where the p-type and n-type impurities are doped.
The reflector may include a lower clad layer formed on a silicon substrate; a waveguide layer formed on the lower clad layer; a first impurity layer formed in one end of the waveguide layer; a second impurity layer formed in the other end of the waveguide layer; an upper clad layer formed on the waveguide layer; a first electrode formed on the first impurity layer, passing through the upper clad layer; and a second electrode formed on the second impurity layer, passing through the upper clad layer, and each of the first impurity layer and the second impurity layer is a p+-type impurity layer or a n+-type impurity layer.
A vertical cross section of the waveguide layer may include a first waveguide layer having a horizontal side with a first length and a vertical side with a second length; a second waveguide layer provided on the first waveguide layer, having a horizontal side with a third length and a vertical side with a fourth length, and the first length is larger than the third length.
The optical device may further include a third impurity layer formed on the second waveguide layer, in case the same type impurity is doped in the first impurity layer and the second impurity layer; and a third electrode formed on the third impurity layer, passing through the clad layer, wherein in case the first impurity layer and the second impurity layer are the same n+-type impurity, the third impurity layer is a p+-type impurity layer, and in case the first impurity layer and the second impurity layer are the same p+-type impurity layer, the third impurity layer is a n+-type impurity layer.
According to the embodiments of the present disclosure, exemplary embodiments of the present disclosure provide an optical device using semiconductors, which can achieve control of light refraction or reflection based on the silicon semiconductor having a p-n junction and a waveguide structure.
Furthermore, exemplary embodiments of the present disclosure also provide an optical device using semiconductors, which may directly modulate an amplitude of light by control of reflection or refraction.
a through 3h are diagram illustrating a structure and operation of an optical device according to a first embodiment of the disclosure;
a through 4h are diagrams illustrating a structure and operation of an optical device according to a second embodiment of the disclosure;
a through 5h are diagrams illustrating a structure and operation of an optical device according to a third embodiment of the disclosure;
a through 6h are diagrams illustrating a structure and operation of an optical device according to a fourth embodiment of the disclosure;
a through 7h are diagrams illustrating a structure and operation of an optical device according to a fifth embodiment of the disclosure;
a through 8c are diagrams illustrating a structure and operation of an optical device according to a sixth embodiment of the disclosure;
a through 9h are diagrams illustrating a structure and operation of an optical device according to a seventh embodiment of the disclosure;
a through 10f are diagrams illustrating a structure and operation of an optical device according to an eighth embodiment of the disclosure; and
a and 11b are diagram illustrating a structure of a waveguide and a clad and an arrangement of electrodes which can be applied to the first through eighth embodiments of the disclosure.
To solve the disadvantages described hereinabove, an optical device using semiconductors according to exemplary embodiments of the disclosure will be described in detail.
Exemplary embodiments of the disclosed subject matter are described more fully hereinafter with reference to the accompanying drawings. The disclosed subject matter may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein.
The change of refractive index in silicon semiconductor may be implemented by the electro-optic Kerr effect, the nonlinear optical Kerr effect, the Franz-Keldysh effect, the plasma dispersion effect (in other words, the effect of carrier injection or depletion) and the thermo-optic effect. Among those effects, the plasma dispersion effect provided by a p-n doping and an electric field may cause relatively large change in the refractive index and a high-speed control, such that it can be used the most. When an electric field is applied to the p-n doping structure, the Franz-Keldysh effect and the electro-optic Kerr effect may be also caused. However, the plasma dispersion effect is predominantly caused and thus the effect of the disclosure will be described mainly considering the plasma dispersion effect.
Functions of the disclosure are described based on a tendency of refractive index change caused by the carrier in the silicon semiconductor. The structure and method disclosed in the specification are not limited to the silicon semiconductor and they may be applied to other semiconductor materials.
According to the plasma dispersion effect in the silicon semiconductor, when the electron or the hole is injected, a refractive index is reduced in comparison with an intrinsic state. Considering such effect of the refractive index change, the present disclosure may provide a p-n junction structure and a method for current injection for reflecting or refracting light.
An optical device according to one embodiment of the disclosure may include a first waveguide 10 aligned along the same direction with a propagation direction of an optical signal incident therein, a second waveguide 20 forming a preset angle from the first waveguide 10, and a reflector 30 arranged in the branched portion of the second waveguide 20 from the first waveguide 10, of which refractive index is varied by an applied voltage. The reflector 30 according to the embodiment is a semiconductor element having a p-type or n-type impurity-doped therein and it has a function to select a path of the optical signal to the first waveguide 10 or the second waveguide 20 through the mean to change the refractive index by applying a voltage.
Specifically, the reflector 30 has a first interface partially in contact with the first waveguide 10 to receive the optical signal, a second interface partially in contact with the first waveguide 10 to pass the optical signal. The n-type and p-type impurities are doped in the reflector 30. The voltage applied to the reflector 30 may be applied via electrodes formed on n+-type and p+-type impurities-doped regions formed adjacent to the n-type and p-type impurities-doped regions. When the concentrations of the n-type or p-type impurities are sufficiently high, the voltage applied to the reflector 30 may be applied via electrodes formed directly on the n-type and p-type regions. Here, the n+-type and p+type mentioned above have a higher doping concentration than the n-type and p-type.
The first waveguide 10 according to the embodiment of the disclosure may be a main waveguide where light straightly pass through and the second waveguide 20 may be a branch waveguide where light is deflected in with a small angle.
The small angle in the embodiments of the disclosure may mean as follows.
In case p-type or n-type impurities are doped in a silicon semiconductor, the refractive index becomes lower than the refractive index in an intrinsic state by carriers of the electron and the hole. According to the carrier effect on the refractive index, a theoretical value of the refractive index in a range of a donor concentration from 5×1017 to 1×1020 may be lowered by 5×10 through 1×10−1 in comparison to an intrinsic-stated silicon (the refractive index n1 of the intrinsic silicon is approximately 3.5). In other words, a difference of the refractive index A n between the doped state (n2) and the intrinsic state (n1) is in a range of Δn=n1 -n2 from −0.0005 to −0.1 and (n1 -n2)/n1 from −0.00015 to −0.03. A critical angle to induce the total internal reflection of light at the interface where the refractive index is lowered in this range is in a range of 1° to 15°. In other materials the variation of the refractive index induced by an electric field or doping is not exceeding the range mentioned above. Considering the range of the variation of the refractive index achievable by an electric field even in a generally usable material, the critical angle is smaller enough to be in a range of 20° or less. Accordingly, the reflection at the small angle means the reflection at a range of 20° or less which can substantially achieve the total reflection with the variation of the refractive index and the embodiments of the disclosure are not limited thereto.
The optical device according to the embodiment of the disclosure may vary the refractive index of the reflector 30 once a controller (not shown) applies an electric signal to the reflector 30 and it may control reflection and/or refraction of light, to control the path of an optical signal.
First of all,
In the first operation mode of the reflector 30 as shown in
Specifically, the first interface of the reflector 30 (a line connected from ai to b1) is the interface where light is reflected. The reflector 30 has to be installed an inner portion of a line connected between c1 and d1 which is an aperture of the second waveguide 20. An angle (θb) formed by the second waveguide 20 with the first waveguide 10 is equal to or larger than an angle (θ1) formed by the reflector 30 with the first waveguide 10 (θb≧θr1).
Next,
In the second operation mode of the reflector 30 as shown in
Specifically, in the structure shown in
Even when the angle (θb) formed by the second waveguide 20 with the first waveguide 10 is smaller than the angle (θr2) formed by the reflector 30 with the first waveguide 10 (θb<θr2), the light internally reflected in the second interface can be internally reflected again at the first interface, guiding the light to the second waveguide 20. In other words, either of those cases that the angle (θb) formed by the second waveguide 20 with the first waveguide 10 is larger or smaller than the angle (θr2) formed by the reflector 30 with the first waveguide 10, the structure shown in
Hereinafter, the state where the light passes through the overall reflector 30 to travel to the first waveguide 10 as shown in
Examples of the p-n junction structure capable of achieving the function of the optical path change, using the structure shown in
a through 3h are diagram illustrating a structure and operation of an optical device according to a first embodiment of the disclosure.
Specifically, the optical device according to the first embodiment of the disclosure has the p-n junction arranged near a center of the first waveguide 10 and the p-n junction is arranged longitudinally with respect to the first waveguide 10.
a is a top view of the arrangement of p and n doped regions and
Specifically, in the first embodiment of the disclosure, when the electric bias is not applied to the p-n junction (Vr=0), a refractive index of a doped p and n regions 133 and 132 is relatively lower than neighboring regions as shown in
In brief, the reflector 30 provided in the optical device according to the first embodiment of the disclosure may include the first interface partially in contact with the first waveguide 10 to have the optical signal incident therein and the second interface partially in contact with the first waveguide 10 to have the optical signal transmitted there through, and the reflector 30 has the n-type and p-type impurities 132 and 133 doped therein. The n-type and p-type impurity-doped regions 132 and 133 are provided in the first interface and a junction area between the n-type 132 and the p-type 133 is arranged in the longitudinal direction of the first waveguide, such that the optical signal can be incident in the n-type 132 and the p-type 133 impurities-doped regions. It is preferred that the n+-type 131 and p+-type 134 impurities-doped regions are formed near the n-type region 132 and the p-type region 133, to apply a voltage.
In the structure of the first embodiment of the disclosure, a thin range of a depletion region is provided in the junction between the p-type 133 and n-type 132, even when a bias is not applied. Accordingly, some of the light might be leaked through the depletion region in a state of Vr=0. Also, as the applied reverse bias is getting larger, the depletion region of the junction between the p-type region 133 and the n-type region 132 is getting broadening but their depletion regions of the p-type region and the n-type region may be asymmetrically broaden. The function of the reflector 30 might be affected by the position of the junction between the p-type region and the n-type region. To overcome such disadvantages in the junction area, the p-n junction is arranged aside to an outer portion of the first waveguide 10 as shown in the second embodiment of
a through 4h are diagrams illustrating a structure and operation of an optical device according to a second embodiment of the disclosure.
As shown in
In other words, the optical device according to the second embodiment of the disclosure has most of the waveguide region of the reflector 30 is arranged in a p-type region 233 for instance. Correspondingly, even in case most of the waveguide region of the reflector 30 can be arranged in an n-type region 232, a similar effect can be achieved. In the structure shown in
In brief, in the optical device according to the second embodiment of the disclosure shown in
In the structure of the optical device according to the second embodiment of the disclosure, the range of the depletion region when the reverse bias is applied is expanded from one lateral surface of the waveguide region of the reflector 30 and the width of the waveguide region of the reflector 30 could be relatively small. An example of the structure for overcoming such a disadvantage of the first embodiment is shown in a third embodiment of the disclosure.
a through 5h are diagrams illustrating a structure and operation of an optical device according to a third embodiment of the disclosure.
As shown in
The optical device according to the third embodiment of the disclosure has an advantage that a distance where carriers are moving for depletion (or a vertical direction distance with respect to the p-n junction) could be shorten, compared with the first and second embodiments.
In brief, in the optical device according to the fifth embodiment of the disclosure shown in
a through 6h are diagrams illustrating a structure and operation of an optical device according to a fourth embodiment of the disclosure.
As shown in
Specifically,
In brief, in the optical device according to the fourth embodiment of the disclosure, an n-type or p-type impurity-doped region 432 or 433 is arranged in the upper region of the first interface and a p-type or n-type impurity-doped region is arranged in the lower region of the first interface.
In the optical device according to the fourth embodiment of the disclosure, n+-type impurity-doped regions 431 and 434 are in contact with both ends of an n-type region 432 and a p+-type impurity-doped region 435 is in contact on the p-type region 433, in case an n-type region 432 is arranged in the lower region of the first interface. In this instance, most light is incident via the p-type impurity-doped region 433.
In the optical device according to the fourth embodiment of the disclosure, in case a p-type is arranged under the first interface, a p+-type impurity-doped region is in contact with both ends of the p-type region and n+-type impurity-doped region is in contact on the n-type. In this instance, most light may be incident via the n-type impurity-doped region.
a through 7h are diagrams illustrating a structure and operation of an optical device according to a fifth embodiment of the disclosure.
As shown in
Specifically, the optical device according to the fifth embodiment of the disclosure has an intrinsic region 533 installed in a first waveguide 10 shown in
In brief, the optical device according to the fifth includes the intrinsic region 533 arranged between the n-type impurity-doped region 532 and the p-type impurity-doped region 534. The optical signal is incident in the intrinsic region 533.
In the optical device according to the fifth embodiment of the disclosure, carrier injection is accomplished in a traverse direction when the forward bias is applied. Even in case the width of the waveguide region of the reflector 30 is broad, the injection time is increased and the operation speed of the device might be lowered disadvantageously. An example of the structure for overcoming such disadvantage is shown as a sixth embodiment of the disclosure.
a through 8c are diagrams illustrating a structure and operation of an optical device according to a sixth embodiment of the disclosure.
A shown in
In brief, in a first structure of the optical device according to the sixth embodiment of the disclosure, a first n-type impurity-doped region 632 and a first n-type impurity-doped region 634 are sequentially arranged. An intrinsic region 633 is provided between the first n-type impurity-doped region 632 and the second n-type impurity-doped region 634. Also, a p+ type impurity-doped region 636 is arranged on the upper intrinsic region 633 and the optical signal is incident in the intrinsic region 633.
Moreover, a third n-type impurity-doped region 640 may be additionally arranged between the first n-type impurity-doped region 632 and the second n-type impurity-doped region 634, under the lower intrinsic region.
In a second structure (not shown) of the optical device according to the sixth embodiment of the disclosure, a first p-type impurity-doped region and a first p-type impurity-doped region are sequentially arranged. An intrinsic region is provided between the first p-type impurity-doped region and the second p-type impurity-doped region. Also, an n+-type impurities-doped region is arranged on the upper intrinsic region and the optical signal is incident in the intrinsic region. Moreover, a third p-type impurity-doped region may be additionally arranged between the first p-type impurity-doped region and the second p-type impurity-doped region, under the lower intrinsic region.
a through 9h are diagrams illustrating a structure and operation of an optical device according to a seventh embodiment of the disclosure.
As shown in
More specifically, the structure and operation of the optical device according to the seventh embodiment of the disclosure shown in
In the structure of the first through sixth embodiments of the disclosure mentioned above, a p-region or n-region is arranged in a parallelogram shape along a shape of the reflector 30. Reflection of light occurs at the first interface of the p-type or n-type region. In contrast, the structure of the optical device according to the seventh embodiment of the disclosure is approximately trapezoid-shaped. Light passes through parallel sides (almost vertical with respect to the first waveguide 10) in the trapezoid shaped region and a depletion region is formed in a junction between p-type region 733 and n-type region 732 having inclined sides and total reflection is generated in the inclined depletion region, only to guide the light to the second waveguide 20. In the structure shown in
When a bias is not applied in the structure shown in
g shows a method for attaining a reflection state by applying a reverse bias. Once the reverse bias is applied, the depletion region is expanded near the p-n junction as shown in
In brief, in the optical device according to the seventh embodiment of the disclosure, a line in contact with an n-type 732 and a p-type 733 is formed with a diagonal shape on a plane of the reflector 30. A first interface and a second interface are formed in a junction region of this diagonal line and the optical signal is guided between the first interface and the second interface, to be guided out to the second waveguide. In the optical device according to the seventh embodiment, the outer interfaces of an area where an n-type 732 and a p-type 733 are doped in the reflector may form a right angle with the first waveguide 10 or an inclined angle near the right angle and may not affect traveling of the optical signal.
Moreover, the optical signal is incident from the p-type-impurity-doped region 733 forming the first interface and guided out to the first waveguide 10, passing the n-type-impurity-doped region 732 forming the second interface Or it may be guided out to the second waveguide 20, using a depletion layer generated in a junction region between the n-type impurity-doped region 732 and the p-type impurity-doped region 733a.
Alternatively, the optical signal may be incident from the n-type-impurity-doped region 732 forming the first interface, using the p-type-impurity-doped region 733 forming the second interface.
a through 10f are diagrams illustrating a structure and operation of an optical device according to an eighth embodiment of the disclosure.
a is a top view illustrating arrangement of p 833 and n 832 doped regions.
Even in a state where no bias is applied, at the first interface (the interface where a dot i2 is placed) of the reflector 30 the refractive index is varied to a higher value as shown in
Once the forward bias is applied in the structure shown in
In brief, in the optical device according to the eighth embodiment of the disclosure, a reflector 30 includes an intrinsic region 835 having both diagonal-shaped sides between n-type 832 and p-type 833 regions, seen on the plane view. A first interface and a second interface are formed in both diagonal-shaped sides in the intrinsic region 835. The optical signal is incident from the n-type or p-type-impurity-doped region 832 or 833 forming the first interface and is guided out to the first waveguide 10, or to the second waveguide 20, using the intrinsic region 835 forming the second interface.
a and 11b are diagram illustrating structures of a waveguides and dads and configurations of electrodes which can be applied to the first through eighth embodiments of the disclosure.
a is a diagram illustrating that a p+ layer 932 and an n+ layer 931 and electrodes 933 and 934 are laterally configured in both lateral ends of the waveguide. A silicon oxide layer 912 is formed on a silicon substrate 911 and a silicon rib waveguide 936 is formed on the silicon oxide layer. An upper silicon oxide layer 913 is covered on the rib waveguide 914. A lower silicon oxide layer 912 and the upper silicon oxide layer 913 are used as a clad layer of the waveguide. The p, n or i region with a p-n junction or p-i-n junction may be formed in the reflector 30 of the rib waveguide 914. According to a main feature shown in
In
In
The electric connection between the p+ electrode 934 in
The structure shown in
In brief, the reflector 30 according to the present disclosure may include a waveguide layer 914 crossing a cross section of a first waveguide 10, to pass an incident optical signal there through, a first impurity layer formed in one end of the waveguide layer 914, a second impurity layer formed in the other end of the waveguide layer 914, a first electrode 933 formed on the first impurity layer, passing through an upper clad layer 913 formed on the waveguide layer 914, and a second electrode 934 formed on the second impurity layer, passing through the upper clad layer 913. The first impurity layer and the second impurity layer are the p+-type impurity layer or n+-type impurity layer, respectively.
The optical device according to the disclosure may further include a silicon substrate 911, a lower clad layer 912 formed on the silicon substrate 911, a waveguide layer 914 formed on the lower clad layer 912 and an upper clad layer 913 formed on the waveguide layer 914.
A longitudinal cross section of the waveguide layer 914 includes a first waveguide layer having a horizontal side with a first length and a vertical side with a second length, and a second waveguide layer arranged in a central portion above the first waveguide layer, having a horizontal side with a third length and a vertical side with a fourth length. Specifically, the first length is longer than the third length and the waveguide layer 914 forms the rib waveguide.
The reflector 30 may further include a third impurity layer 936 formed on the second waveguide layer, and a third electrode 937 formed on the third impurity layer, in case the type of the impurities doped in the first impurity layer and the second impurity layer is the same type. Also, in case the first impurity layer and the second impurity layer are the same n+-type impurity layer, the third impurity layer is a p+type impurity layer. In case the first impurity layer and the second impurity layer are the same p+-type impurity layer, the third impurity layer is the n+-type impurity layer.
The upper clad layer 913 and the lower clad layer 912 may be formed of silicon oxide. Also, the waveguide layer 914 may be formed of silicon semiconductor.
According to the optical device using semiconductors of a preferred embodiment of the present invention, optical refraction and reflection control can be achieved by means of semiconductor silicon which has a p-n junction structure and a waveguide structure. Also, according to the optical device using semiconductors of the present invention, the amplitude of light can be directly modulated using the reflection or refraction control.
Number | Date | Country | Kind |
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10-2012-0106783 | Sep 2012 | KR | national |
Filing Document | Filing Date | Country | Kind |
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PCT/KR2012/010506 | 12/6/2012 | WO | 00 |