Thermo-optic phase shifter with partial suspension structure

Abstract

Thermo-optical phase shifter having a partially suspended structure. Disclosed embodiments relate to a thermo-optical phase shifter and a method of adjusting the speed and efficiency of intensity modulation using the thermo-optical phase shifter. The thermo-optical phase shifter includes a substrate defining at least one trench within a portion of the substrate and a buried oxide (BOX) layer formed over the substrate. The BOX layer is disposed along a length of the substrate. The thermo-optical phase shifter includes a waveguide disposed on the BOX layer for guiding an input signal, the substrate extending partially outward on either side of the waveguide. The method includes receiving an input signal by the thermo-optical phase shifter, adjusting a voltage applied to a heater of the thermo-optical phase shifter, and transmitting an output signal from the thermo-optical phase shifter.

Description

[Technical field]

[0001] The present invention generally relates to a thermo-optical phase shifter with a suspended structure. The thermo-optical phase shifter of the present invention balances efficiency and speed to meet different application requirements. These thermo-optical phase shifters can be used in all fields of photonics devices and integrated circuits with phase shifting or modulation, including but not limited to silicon photonics, near / mid infrared, visible light and microwave photonics. In particular, these phase shifters can be used as key components for different applications such as quantum computing, LiDAR (Light Detection And Ranging) and sensors to increase speed, improve thermal isolation and increase power efficiency. The present invention also relates to a method for adjusting the speed and efficiency of intensity modulation. [Background technology]

[0002] Generally, thermo-optical phase shifters are used for phase modulation or intensity modulation of optical signals. The thermo-optical phase shifter changes the phase and intensity of the input optical signal based on the characteristics of the input optical signal and the thermo-optical phase shifter, and transmits an output optical signal. Thermo-optical phase shifters generally have low loss, simple fabrication, and power efficiency, and are applied in a wide range of fields such as quantum computing, optical parametric amplifiers (OPAs), various sensor and switching applications, advanced communications, and neural networks.

[0003] The thermo-optic phase shifter has a composite having an optical waveguide, a p-type region, and an n-type region formed on a silicon substrate. The optical waveguide is disposed between the p-type region and the n-type region. The thermo-optic phase shifter further has a heater, a core including a silicon substrate, and a cladding layer disposed on the silicon substrate.

[0004] In the operation of a thermo-optic phase shifter, the overall performance of the thermo-optic phase shifter mainly depends on two main characteristics: power efficiency and limited rise / fall time constant. These two characteristics depend on the heat dissipation of the thermo-optic phase shifter and differ based on the change in the heat dissipation of the thermo-optic phase shifter.

[0005] Existing thermo-optical phase shifters are mainly of two types, as shown in FIG. 1A and FIG. 1B. FIG. 1A shows a first type of thermo-optical phase shifter, which is commonly used for different applications. The first type of thermo-optical phase shifter has a substrate 102, a Buried Oxide (BOX) layer 104, a waveguide 106, a heater 108 and a cladding 110. In FIG. 1B, the suspension region is arranged along the complete structure. The thermo-optical phase shifter in FIG. 1B has a small power consumption at low efficiency and high speed. FIG. 1B shows a second type of thermo-optical phase shifter with a trench 112 in the substrate 114. The second type of thermo-optical phase shifter also has a BOX layer 116, a waveguide 118, a heater 120 and a cladding 122. The second type of thermo-optical phase shifter in FIG. 1B is high efficiency and low speed.

[0006] The second type of thermo-optic phase shifter, as shown in Figure 1B, has improved power efficiency, while the first type of thermo-optic phase shifter, as shown in Figure 1A, has improved speed during operation. The second type of thermo-optic phase shifter has reduced power efficiency, while the first type of thermo-optic phase shifter has reduced speed during operation. However, none of the existing thermo-optic phase shifters offer the combined advantages of increased speed during operation, improved thermal isolation, and improved power efficiency in one thermo-optic phase shifter. Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need to provide a thermo-optic phase shifter that solves the above problems and offers the combined advantages of increased speed, improved thermal isolation and increased power efficiency during operation. [Means for solving the problem]

[0008] The embodiments of the present disclosure relate to a thermo-optic phase shifter and a method of receiving an input signal and transmitting an output signal using a thermo-optic phase shifter. In an exemplary embodiment, the thermo-optic phase shifter includes a substrate defining at least one trench, each trench having the same length. Additionally, the thermo-optic phase shifter includes a Buried Oxide (BOX) layer formed over the substrate and disposed along the length of the substrate. The thermo-optic phase shifter further includes a waveguide disposed on the BOX layer for guiding the input signal, and the substrate defining the trench extends partially outward on both sides of the waveguide.

[0009] In an exemplary embodiment, each of the plurality of trenches has a depth of 120 micrometers (μm).

[0010] In some embodiments, the substrate extends along the transverse axis of the waveguide.

[0011] In some embodiments, the thermo-optic phase shifter includes a heater disposed adjacent to the waveguide, the heater heating the waveguide.

[0012] In one embodiment, the thermo-optic phase shifter includes a cladding layer disposed along the length of the heater to cover the thermo-optic phase shifter, the cladding layer configured to protect the thermo-optic phase shifter and to provide light isolation between the heater and the waveguide.

[0013] In some embodiments, each trench has a different duty cycle.

[0014] In one embodiment, the thermo-optic phase shifter has a substrate made of silicon, which provides heat dissipation.

[0015] In another embodiment, a thermo-optic phase shifter includes a substrate defining a trench within a portion of the substrate, the trench having a length, and a BOX layer formed over the substrate, the BOX layer disposed along the length of the substrate to cover the trench, the thermo-optic phase shifter includes a waveguide disposed over the BOX layer for guiding an input signal, the substrate extending partially outward on either side of the waveguide.

[0016] In another embodiment, the trenches have a predetermined period of 120 micrometers (μm).

[0017] In some embodiments, the thermo-optic phase shifter includes a heater disposed adjacent to the waveguide, the heater being configured to heat the waveguide.

[0018] In other embodiments, the heater includes multiple heater elements disposed adjacent to the waveguide.

[0019] In an exemplary embodiment, a cladding layer is disposed along the length of the heater to cover and protect the thermo-optic phase shifter, the cladding layer being configured to separate light between the heater and the waveguide.

[0020] In an exemplary embodiment, the BOX layer is composed of silica to prevent light leakage into the substrate.

[0021] In some embodiments, the substrate is made of silicon and provides heat dissipation.

[0022] In some embodiments, a method of adjusting the speed and efficiency of intensity modulation is disclosed. The method includes receiving an input signal by a thermo-optic phase shifter. The input signal is an optical signal. The thermo-optic phase shifter includes a substrate defining at least one trench, a BOX layer formed on the substrate, and a waveguide disposed on the BOX layer. The substrate extends partially outward on either side of the waveguide. The method includes adjusting a voltage applied to a heater of the thermo-optic phase shifter. The thermo-optic phase shifter transmits an output signal. The output signal has a different phase than the input signal, the phase difference being based on a change in the applied voltage. Effect of the Invention

[0023] The thermo-optic phase shifters of the present disclosure provide the combined advantages of improved speed, better thermal isolation and improved power efficiency during the operation of a single thermo-optic phase shifter. These phase shifters can be used as key components for different applications such as quantum computing, LiDAR and sensors.

[0024] For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in conjunction with the accompanying drawings and detailed description, where like reference numerals represent like parts. [Brief description of the drawings]

[0025] [Figure 1A] 1 is prior art showing an existing type of thermo-optic phase shifter. [Figure 1B] 1 is prior art showing an existing type of thermo-optic phase shifter.

[0026] [Figure 2A] FIG. 2 is an exemplary diagram illustrating a photothermal phase shifter according to a first embodiment of the present disclosure. [Figure 2B] FIG. 2 is an exemplary diagram illustrating a photothermal phase shifter according to a first embodiment of the present disclosure.

[0027] [Figure 3A]FIG. 13 is an exemplary diagram illustrating a photothermal phase shifter according to a second embodiment of the present disclosure. [Figure 3B] FIG. 13 is an exemplary diagram illustrating a photothermal phase shifter according to a second embodiment of the present disclosure.

[0028] [Figure 4] 13 is a graph showing the power efficiency of a thermo-optic phase shifter as a function of heater length.

[0029] [Diagram 5] 1 is an exemplary flow diagram illustrating a method for adjusting the speed and efficiency of intensity modulation using a thermo-optic phase shifter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] First, exemplary embodiments of one or more embodiments are presented below, but it should be understood that the disclosed systems and methods can be implemented using any number of technologies, whether currently known or not. The present disclosure should in no way be limited to the exemplary embodiments, drawings, and technologies presented below, but can be modified within the scope of the appended claims, along with their full scope of equivalents.

[0031] The following brief definitions of terms apply throughout the application:

[0032] Use of the terms "comprising" and "including" (as well as other forms such as "comprising," "including," "including") should not be construed as limiting.

[0033] The phrases "in one embodiment," "according to one embodiment," and the like generally mean that the particular feature, structure, or characteristic that follows the phrase may be included in at least one embodiment of the invention, and may be included in more than one embodiment of the invention (importantly, such phrases do not necessarily refer to the same embodiment).

[0034] Use of the words "exemplary" or "example" should be understood to refer to non-limiting examples, and use of such words means "serving as an example, illustration, or illustration," and should not necessarily be construed as preferred or advantageous over other embodiments.

[0035] The terms "about" or "approximately," when used in connection with a number, are understood to mean the particular number, or alternatively, a range surrounding the particular number, as would be understood by one of ordinary skill in the art.

[0036] When the specification describes an element or feature as "may include," "can," "may," "should," "will," "preferably," "potential," "typically," "optionally," "for example," "often," or "may" (or other such phrases), it does not require the inclusion or having of that particular element or feature. Such elements or features may be optionally included or excluded in some embodiments.

[0037] In the following description, reference is made to the accompanying drawings which form a part of this specification, and which illustrate specific embodiments which may be implemented. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it should be understood that other embodiments may be utilized, and structural, logical, and electrical changes may be made without departing from the scope of the disclosure. Thus, the following description of exemplary embodiments should not be construed in a limiting sense.

[0038] 2A and 2B show different views of a thermo-optic phase shifter 200 according to a first embodiment of the present disclosure, with Fig. 2A showing a top view of the thermo-optic phase shifter 200 and Fig. 2B showing a cross-sectional view.

[0039] The thermo-optic phase shifter 200 includes a substrate 202, a buried oxide (BOX) layer 204, and a waveguide 206. Additionally, the thermo-optic phase shifter 200 includes a heater 208 and a cladding layer 210. The substrate 202 includes a plurality of trenches, such as trenches 212, 214, 216, 218, and 220, as shown in FIG. 2B.

[0040] In this regard, the trenches 212, 214, 216, 218, 220 are included in the substrate layer and include holes or spaces between the substrate pillar structures 226 that contact the BOX layer 204. The trenches 212, 214, 216, 218, 220 are formed such that the top of the substrate layer and the layers above are suspended through the pillar structures 226. Such a structural configuration may be referred to as a suspended structure as referred to herein. The suspended structure is the suspension of the optical waveguide 206, the BOX 204, and the cladding layer 210 by partial etching of the silicon (Si) substrate.

[0041] The oxide layer 205 separates the heater 208 and the optical waveguide 206 to reduce metal absorption. In one embodiment, the oxide layer 205 can act as a cladding layer for a thermal phase optical shifter without the heater 208. Additionally, the oxide layer 205 acts to separate the light.

[0042] In one example, the substrate 202 is composed of silicon. In another example, the substrate 202 is formed of a glass material including quartz or silica. As shown in FIG. 2B, the substrate 202 includes a plurality of trenches 212, 214, 216, 218, and 220. Although FIG. 2B shows the substrate 202 having five trenches 212, 214, 216, 218, and 220, in some embodiments, there may be more than five trenches in the substrate 202. In FIG. 2B, there are five trenches, but it will be understood that the number of trenches may be less than five or more than two. The length (L) of each of the trenches may be less than 80 μm. The number of trenches may depend on the overall length of each structure. The trenches may be formed by etching.

[0043] Each of the multiple trenches 212, 214, 216, 218, 220 can have the same length L1 and period P1, and each trench 212, 214, 216, 218, 220 is disposed equidistant from adjacent trenches in the substrate 202. In one example, the length L1 and period P1 are arbitrary values ​​based on the structure of the trench. In one example, the trench is obtained by partially etching the silicon substrate under the optical waveguide by an isotropic etching process. The optical waveguide is suspended in the air by a small bridge to hold the structure and prevent collapse.

[0044] In one example, the substrate 202 is positioned such that the substrate 202 extends outward along the transverse axis of the thermo-optic phase shifter 200, for example, on both sides of the waveguide 206. The substrate 202, the waveguide 206, and the heater 208 are aligned such that the trenches 212, 214, 216, and 218 are not covered by the waveguide 206 and the heater 208 formed on the substrate 202. In one example, the trenches 212, 214, 216, 218, and 220 isolate the heat dissipation. Since the heated optical waveguide is suspended in air, there is no connection with the silicon substrate. Thus, the trenches isolate the heat dissipation to the silicon substrate. In comparison, FIG. 1A and FIG. 1B consist of a structure 112 having a trench 124 on the side of the waveguide, whereby the air in the structure 112 can prevent the heat dissipation to the silicon substrate.

[0045] 2A, each trench includes two holes or spaces on either side of the waveguide 206. For example, trench 212 includes two holes 212a and 212b. The depth of each of the two holes from the top of the cladding layer 210 to the substrate 202 may be 120 micrometers (μm). The holes themselves form a trench.

[0046] In one embodiment, the BOX layer 204 can be composed of silica or silicon dioxide (SiO2). The BOX layer 204 is sandwiched between a thicker silicon substrate, such as the substrate 202, and the top silicon layer 203, whereby the BOX layer 204 acts as an insulating layer. The BOX layer 204 has two opposing surfaces, a top surface and a bottom surface. In one embodiment, the top silicon layer 203 contacts the top surface of the BOX layer 204, and the substrate 202 contacts the bottom surface of the BOX layer 204 through the substrate pillars 226. During operation of the thermo-optic phase shifter 200, the BOX layer 204 prevents light leakage to the substrate 202. The BOX layer 204 is thicker, for example, than 2 micrometers, to prevent light coupling to the substrate. This provides the advantage of reducing light loss.

[0047] The waveguide 206 is formed on the BOX layer 204 and is made of a high thermo-optic coefficient material with a linear index of refraction, such as silicon or silicon nitride. The index of refraction changes in response to a change in temperature, with an increase in temperature increasing the index of refraction and a decrease in temperature decreasing the index of refraction. In one example, the material of the waveguide 206 is selected such that a change in the index of refraction of the waveguide 206 causes a change in the phase of light passing through the waveguide 206. The waveguide 206 may be used to couple optical signals, such as an input signal and a corresponding output signal, into and out of the thermo-optic phase shifter 200.

[0048] The heater 208, in one example, is made of doped silicon or a metal such as titanium nitride (TiN). The heater 208 is disposed adjacent to the waveguide 206 and extends along the length of the waveguide 206. In one example, the heater 208 is a single heating element extending along the length of the waveguide 206 or multiple heating elements distributed around the waveguide 206. The purpose of the heater 208 placement is to provide direct and efficient heating to the waveguide 206, causing a rapid increase in the refractive index of the waveguide 206.

[0049] The heater 208 generates heat based on a voltage applied by a power source. The power source is electrically connected to the heater 208 through a pair of electrodes. For example, when the heater 208 is to be heated, the power source applies a voltage to the heater 208, and the heater generates heat. The amount of heat generated depends on the change in the voltage applied to the heater 208. In one example, the heater 208 supplies a large amount of heat to the waveguide 206, causing the temperature of the waveguide 206 to increase rapidly. For example, if the heater 208 is made of titanium nitride (TiN), titanium (Ti), or other materials, the heater 208 supplies heat when electricity is applied. When the waveguide 206 is heated, the refractive index of the waveguide 206 changes based on the temperature response of the waveguide 206. The change in the refractive index causes a change in the phase and intensity of the signal transmitted through the waveguide 206 as the output signal.

[0050] In one embodiment of the present disclosure, the cladding layer 210 is composed of an insulating material such as silicon dioxide (SiO2). The cladding layer 210 is disposed on top of the heater 208. The cladding layer 210 protects the thermo-optic phase shifter 200 and provides optical isolation between the heater 208 and the waveguide 206.

[0051] The thermo-optic phase shifter 200 is rectangular in shape, as shown in Figures 2A and 2B. The thermo-optic phase shifter 200 is configured to receive an input signal at one end 222 of the thermo-optic phase shifter 200 and transmit an output signal at the other end 224 of the thermo-optic phase shifter 200. In one example, the input signal and the output signal are light waves or light waves received by the thermo-optic phase shifter 200 and propagating through the thermo-optic phase shifter 200. In one example, when no phase shifting is performed by the thermo-optic phase shifter 200, the input signal and the output signal are collinear with each other along a major axis of the thermo-optic phase shifter 200. In other words, when the input signal enters the thermo-optic phase shifter 200 at the end 222 and the output signal is transmitted from the other end 224, the input signal and the output signal are substantially along the same line. In one example, the output signal has the same amplitude and frequency as the input signal. The thermo-optic phase shifter 200 has suspended regions arranged in different ratios in parts to balance power consumption and speed. In Fig. 2B, there is no duty cycle, the only parameter is the length of the suspended part. Longer length reduces speed and increases efficiency. Shorter length increases speed and decreases efficiency.

[0052] During operation, in which a phase shift is introduced by the thermo-optic phase shifter 200, a power supply applies a voltage to the heater 208, which heats the waveguide 206 as described above. Heating the waveguide 206 changes the refractive index, thereby changing the phase of the input signal. As the input signal propagates through the thermo-optic phase shifter 200, the trenches 212, 214, 216, 218, and 220 in the substrate 202 provide different duty cycles, thereby improving the efficiency and speed of the intensity modulation. An output signal is transmitted from the thermo-optic phase shifter 200 with a phase difference relative to the input signal. The magnitude of the phase difference is based on the amount of voltage applied to the thermo-optic phase shifter 200. The higher the voltage applied to the thermo-optic phase shifter 200, the higher the temperature of the heater 208, which increases the phase shift of the output signal. The trenches 212, 214, 216, 218, and 220 allow for tuning of the efficiency and speed of the intensity modulation by the thermo-optic phase shifter 200.

[0053] 3A and 3B show various views of a thermo-optic phase shifter 300 according to a second embodiment of the present disclosure, with FIG 3A being a top view of the thermo-optic phase shifter 300 and FIG 3B being a cross-sectional view of the thermo-optic phase shifter 300.

[0054] The thermo-optic phase shifter 300 includes a substrate 302, a buried oxide (BOX) layer 304, an oxide layer 305, and a waveguide 306. The thermo-optic phase shifter 300 includes a heater 308 and a cladding layer 310. The substrate 302 includes a single trench 312, as shown in FIG. 3B. The trench 312 is disposed within a portion of the substrate 302, for example, within a central region of the substrate 302.

[0055] The substrate 302 is made of silicon or glass materials, including quartz. In one embodiment, the trench 312 has a predetermined length L2 and has two holes on each side of the waveguide 306. The depth of each of the two holes from the top of the cladding layer 310 to the substrate 302 is 120 μm. In one example, the substrate 302 defining the trench 312 extends outward on either side of the waveguide 306 along the transverse axis of the thermo-optic phase shifter 300. The substrate 302, the waveguide 306 and the heater 308 are aligned such that the trench 312 is not covered by the waveguide 306 and the heater 308.

[0056] 3A, the trench 312 includes two holes on each side of the waveguide 306. For example, the trench 312 includes two holes, 312a and 312b. The depth of each of the two holes from the top of the cladding layer 310 to the substrate 302 may be 120 micrometers (μm).

[0057] In one embodiment, the BOX layer 304 is comprised of silica. The waveguide 306 is formed on the BOX layer 304 and is comprised of a high thermo-optic coefficient material with a linear index of refraction, such as silicon or silicon nitride. The index of refraction of the waveguide 306 changes in response to changes in temperature. The heater 308 is disposed adjacent to the waveguide 306 and extends along the length of the waveguide 306. The heater 308, in one example, has multiple heating elements distributed around the waveguide 306.

[0058] 2A and 2B, the heater 308 is similarly connected to a power source via a pair of electrodes, and when a voltage is applied across the pair of electrodes, variations in the voltage cause variations in the temperature of the heater 308. The heater 308, in one example, is constructed of doped silicon or a metal such as titanium nitride (TiN).

[0059] In an exemplary embodiment, the cladding layer 310 is composed of an insulating material such as silicon dioxide (SiO2). The cladding layer 310 protects the thermo-optic phase shifter 300 and provides optical isolation between the heater 308 and the waveguide 306.

[0060] In operation, the thermo-optic phase shifter 300 receives an input signal at one end 314 of the thermo-optic phase shifter 300. The phase shift performed by the thermo-optic phase shifter 300 is based on heating by the heater 308, similar to heating by the heater 208, as described above with respect to the operation of the thermo-optic phase shifter 200. As the input signal propagates through the thermo-optic phase shifter 300, the trenches 312 provide a different duty cycle, improving the efficiency and speed of intensity modulation. An output signal is then transmitted from the other end 316 of the thermo-optic phase shifter 300. The output signal has a phase difference with respect to the input signal.

[0061] In one example, the magnitude of the phase difference is based on the voltage applied to the thermo-optic phase shifter 300. The trenches 312 provide different duty cycles and associated efficiencies and speeds in phase modulation, so that the efficiency and speed can be tuned.

[0062] The speed and efficiency adjustments are shown in graph 400 of FIG. 4. FIG. 4 shows test results for different duty and hanging length or total heater length. Graph 400 shows power efficiency plotted on the y-axis and heater length plotted on the x-axis versus time. Lines 402 and 404 show experimental results for the thermo-optic phase shifter 200 of FIG. 2A and FIG. 2B. Graph 400 shows measurements of the rise-limited time constant or speed and power efficiency for different ratios of hanging heater length to total heater length. In FIG. 4, when the duty is 100%, the structure has the low power consumption and slow speed of the hanging heater total of FIG. 1B, and when the duty is 0%, the structure has the high power consumption and fast speed of the hanging heater without the hanging heater of FIG. 1A. The experimental results are comparable for both the embodiments of FIG. 2A-B and FIG. 3A-B.

[0063] In one example, an ultra-low power 2x2 thermo-optic waveguide-based switch is fabricated using standard Complementary Metal-Oxide-Semiconductor (CMOS) processes. The phase arm is suspended by removing the adjacent SiO2 and 120 micrometers of underlying Si, while leaving a small SiO2 beam to support the suspended phase arm for structural strength. A significant power consumption reduction of over 98% is achieved compared to a switch without an insulating layer. The power consumption reduction is achieved by preventing heat leakage from the phase arm due to the presence of an air insulating layer. The thermo-optic phase shifter according to the present invention exhibits an extinction ratio of over 23 dB at 1550 nm for the TE mode with an ultra-low power consumption of 0.49 milliwatts (mW), and a response time of 266 microseconds, including a rise time of 144 microseconds and a fall time of 122 microseconds.

[0064] The operation of the thermo-optic phase shifters 200 and 300 will be described with reference to FIG.

[0065] Referring to FIG. 5, in conjunction with FIGS. 2A and 2B and 3A and 3B, a method flow diagram 500 illustrating adjusting the speed and efficiency of intensity modulation by a thermo-optical phase shifter, such as thermo-optical phase shifters 200 and 300, is described.

[0066] Moving first to block 502, an input signal is received. The input signal may be an optical signal, a light wave, or an incident light beam. In one example, the input signal is received by a thermo-optic phase shifter, such as thermo-optic phase shifters 200 and 300. The thermo-optic phase shifter includes a substrate defining at least one trench, a BOX layer formed on the substrate and a waveguide disposed on the BOX layer, and a heater. The substrate extends partially outward on either side of the waveguide.

[0067] The heater is positioned adjacent to the waveguide to directly heat the waveguide. In one example, the heater is connected to a power source via a pair of electrodes or wires. The power source is used to apply a voltage to the heater to generate heat. In block 504, a voltage applied to the heater of the thermo-optic phase shifter is adjusted. The voltage is adjusted to control the amount of heat generated by the heater. The amount of heat generated by the heater causes the waveguide to change its refractive index. The waveguide modulates the phase of an input signal based on the change in the refractive index of the waveguide and transmits an output signal.

[0068] Thereafter, in block 506, an output signal is transmitted from the thermo-optic phase shifter. In one example, the phase of the output signal differs from the phase of the input signal, and the phase difference is based on a change in the applied voltage. For example, a higher voltage increases the phase difference between the input and output signals, and a decrease in the applied voltage decreases the phase difference. The substrate having at least one trench creates a difference in the duty cycle, allowing a balance between speed and power efficiency of the thermo-optic phase shifter.

[0069] Although several embodiments are provided in the present disclosure, it should be understood that the disclosed systems and methods can be embodied in many other specific forms without departing from the spirit or scope of the present disclosure. The present examples should be considered as illustrative and not restrictive, and the intention is not to be limited to the details described herein. For example, various elements or components may be combined or integrated into another system, or certain features may be omitted or not implemented.

[0070] Additionally, techniques, systems, subsystems, and methods described and illustrated in various embodiments as separate or distinct may be combined or integrated with other systems, modules, techniques, or methods without departing from the scope of the present disclosure. Other items shown or described as directly coupled or in communication with one another may be indirectly coupled or in communication through some interface, device, or intermediate component, whether electrical, mechanical, or otherwise. Other examples of modifications, substitutions, and alterations will be ascertainable by those skilled in the art and may be made without departing from the spirit and scope disclosed herein.

[0071] Although various embodiments according to the principles disclosed herein have been shown and described above, modifications thereof may be made by those skilled in the art without departing from the spirit and teachings of the present specification. The embodiments described herein are merely representative and are not intended to be limiting. Many variations, combinations, and modifications are possible and are within the scope of the present disclosure. Alternative embodiments resulting from combining, integrating, and / or omitting features of the embodiments are also within the scope of the present disclosure. Thus, the scope of protection is not limited by the above description, but is defined by the following claims, the scope of which includes all equivalents of the subject matter of the claims. Each claim is incorporated herein as a further disclosure, and the claims are embodiments of the present invention. Moreover, any advantages and features described above may be related to a particular embodiment, but are not intended to limit the application of such issued claims to processes and structures that achieve any or all of the above advantages or have any or all of the above features.

[0072] Various systems and methods have been described herein, various embodiments of which may include, but are not limited to, the claims provided herein.

Claims

1. 1. A thermo-optic phase shifter comprising: a substrate defining at least one trench; a BOX layer formed on the substrate; a waveguide disposed on the BOX layer for guiding an input signal; a heater disposed on the waveguide to supply heat to the waveguide; A thermo-optic phase shifter, wherein each trench includes two holes disposed on each side of the waveguide and configured to isolate heat dissipation.

2. The thermo-optic phase shifter of claim 1 , wherein at least one of the trenches has a depth of 120 micrometers (μm).

3. The thermo-optic phase shifter of claim 1 , wherein the substrate extends along a transverse axis of the waveguide.

4. Silicon dioxide (SiO ２ 10. The thermo-optic phase shifter of claim 1 further comprising a cladding layer composed of:

5. 2. The thermo-optic phase shifter of claim 1, further comprising a cladding layer disposed along a length of the heater to cover and protect the thermo-optic phase shifter, the cladding layer configured to separate light between the heater and the waveguide.

6. The thermo-optic phase shifter of claim 1 , wherein each of the at least one trench has a different duty cycle.

7. The thermo-optic phase shifter of claim 1 , wherein the substrate is made of silicon, and the substrate provides heat dissipation.

8. The thermo-optic phase shifter of claim 1 , wherein the at least one trench comprises five trenches.

9. The thermo-optic phase shifter of claim 1 , wherein the at least one trench comprises a single trench.

10. 1. A method for adjusting a rate and efficiency of intensity modulation, comprising: receiving an input signal with the thermo-optic phase shifter of claim 1, the input signal being an optical signal; Adjusting a voltage applied to a heater of a thermo-optic phase shifter; transmitting an output signal from the thermo-optic phase shifter, the output signal having a different phase from the input signal, the phase difference being based on a change in an applied voltage.

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