A wavelength thermally-tunable photonic integrated device and a method for fabricating the same
By integrating a cantilever beam structure with a thermally tuned and electrically absorbed modulator, a photonic integrated device with low power consumption, wide wavelength tuning range, and high modulation rate was realized, solving the problems of high power consumption and complex control of existing tunable lasers and improving the performance of optical communication systems.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN GUOKE OPTICAL SEMICON TECH CO LTD
- Filing Date
- 2025-11-25
- Publication Date
- 2026-07-07
AI Technical Summary
Existing tunable lasers have high power consumption and complex control, making it difficult to meet the development needs of future high-speed, low-power optical communication systems.
By integrating a thermally tuned structure based on a sampling grating and an electroabsorption modulator, the cantilever beam structure is locally thermally controlled by a heating resistor, simplifying the external control system and achieving low power consumption, wide wavelength tuning range, and high modulation rate.
It significantly reduces power consumption, simplifies the control system, improves wavelength tuning efficiency and range, and enhances the system's control response speed and overall reliability.
Smart Images
Figure CN121546427B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the technical field of semiconductor optoelectronic integrated devices, and more specifically, to a wavelength thermally tunable photonic integrated device and its fabrication method. Background Technology
[0002] With the development of high-speed optical communication and optical interconnect technologies, tunable lasers, as core light source devices in wavelength division multiplexing (WDM) systems, directly affect the integration density, energy consumption, and transmission rate of optical modules. Existing tunable lasers generally employ current tuning methods based on carrier injection or depletion effects. Wavelength tuning is achieved by injecting current into different sections to change the refractive index. A typical structure of these devices includes multiple functional sections such as a gain region, a front reflection region, a back reflection region, a phase region, and an electro-absorption modulator region. These sections are connected by optical waveguides to form a complete resonant cavity. In this structure, each section requires independent electrodes to achieve wavelength or phase control. For example, the gain region is used for optical amplification, the front and back reflection regions for wavelength selection, the phase region for cavity length fine-tuning, and the modulation region for output optical signal modulation. To achieve precise wavelength control, independent current signals are typically injected into each section, and there are coupling effects between current changes in different sections. Therefore, traditional electro-tunable lasers usually require 4-5 independent current sources for precise control, along with complex feedback algorithms to maintain stable output wavelength. This multi-segment current tuning method has the following prominent problems:
[0003] 1) High power consumption: Each tuning segment requires a continuous injection of a large current (typically in the tens of milliamperes). When multiple segments operate simultaneously, significant Joule heating occurs, leading to high overall device power consumption. For example, to achieve wavelength tuning at the nanometer level, electrically tuned devices typically require a total tuning current of approximately 0–80 mA, resulting in severe heat loss and hindering energy efficiency optimization for high-density optical modules. 2) Complex control circuitry: Due to thermal and electrical coupling between different segments, wavelength tuning requires coordinated adjustment of multiple current channels. The system needs to be configured with multiple constant current sources, a wavelength monitoring unit, and a feedback control module. The control algorithm needs to calculate the current combinations of each segment in real time to lock onto the target wavelength, resulting in a large circuit size and limited response speed.
[0004] In summary, while existing tunable lasers can achieve a wide wavelength tunability range, their high power consumption and complex control make them unsuitable for the development needs of future high-speed, low-power optical communication systems. Therefore, there is an urgent need for a wavelength-thermally tunable photonic integrated device structure with low power consumption and simplified control. Summary of the Invention
[0005] The purpose of this invention is to address the problems in the prior art by providing a wavelength thermally tunable photonic integrated device and its fabrication method, which integrates a thermally tunable structure based on a sampling grating cantilever beam structure and an electro-absorption modulator together, thereby achieving the low power consumption of the cantilever beam structure, the wide wavelength tuning range of the sampling grating structure, and the high modulation rate of the electro-absorption modulator.
[0006] The technical solution of this application is: a method for fabricating a wavelength thermally tunable photonic integrated device, the method comprising:
[0007] S1: Prepare the substrate and divide the modulator area, front grating area, gain area and rear grating area into the substrate in a predetermined direction, with adjacent areas closely connected.
[0008] S2: Grow a gain layer material on the entire surface of the substrate to form a gain layer, wherein the gain layer is located in the gain region. Selectively remove the gain layer material in the modulator region and grow the modulator layer.
[0009] S3: Selectively remove the gain layer material in the front grating region and the back grating region and grow the grating layer material. Create periodically arranged micro-reflective structures on the grating layer material to form a patterned front sampling grating layer and a back sampling grating layer.
[0010] S4: A capping layer and an electrical contact layer are grown sequentially above the entire functional layer consisting of a modulator layer, a front sampling grating layer, a gain layer, and a back sampling grating layer. The capping layer and the electrical contact layer are etched according to a predetermined ridge strip pattern to form a shallow ridge waveguide structure. The shallow ridge waveguide structure is laterally distributed at the center of the upper surface of the modulator layer, the front sampling grating layer, the gain layer, and the back sampling grating layer.
[0011] S5: According to the predetermined cantilever strip pattern, the material in the region below the shallow ridge waveguide structure in the post-sampling grating layer is etched to form a cantilever beam structure, which includes a cantilever beam and air slots symmetrically distributed on both sides.
[0012] S6: P-side electrodes are fabricated above the electrical contact layers in the modulator region, front grating region, and gain region, respectively. A heating resistor is fabricated above the electrical contact layer in the rear grating region. N-side electrodes are fabricated below the substrate.
[0013] Further, S2 specifically includes: growing gain layer material layer by layer from bottom to top on the substrate to form a gain layer consisting of a second lower confinement layer, a second multiple quantum well layer, and a second upper confinement layer; covering the gain layer material of the front grating region, the gain region, and the rear grating region with a mask; etching away the gain layer material of the modulator region; growing modulator layer material layer by layer from bottom to top in the modulator region; removing the mask; and forming a modulator layer consisting of a first lower confinement layer, a first multiple quantum well layer, and a first upper confinement layer.
[0014] Further, in S4, the capping layer and electrical contact layer are etched according to a predetermined ridge-shaped stripe pattern, specifically including:
[0015] First, a transverse strip mask is fabricated at the center of the electrical contact layer. The entire capping layer and electrical contact layer are then dry-etched with SiCl4 gas to form a shallow ridge structure. Next, wet etching with HCl solution is used to modify the two sides of the shallow ridge structure, ultimately forming a shallow ridge waveguide structure that conforms to the predetermined ridge strip pattern. The etching depth is controlled within the capping layer and does not penetrate the capping layer to the material layer below it.
[0016] Furthermore, S4 also includes etching electrical isolation trenches on the electrical contact layer located between two adjacent regions, so that electrical isolation is formed between the modulator region, the front grating region, the gain region and the rear grating region to avoid mutual interference of current in each functional region.
[0017] Furthermore, S5 specifically includes: dividing the positions corresponding to the air slots on both sides of the cantilever beam on the upper surface of the post-sampling grating layer; fabricating a mask with a cantilever strip pattern on the entire device; using the mask to cover the positions other than the air slots; and using reactive ion etching equipment and hydrobromic acid etching to remove the grating layer material corresponding to the air slots to form a cantilever beam structure.
[0018] The technical solution of this application also provides a wavelength thermally tunable photonic integrated device, which includes: a substrate, a modulator layer, a front sampling grating layer, a gain layer, a back sampling grating layer, a capping layer, and an electrical contact layer;
[0019] The modulator layer, the front sampling grating layer, the gain layer, and the back sampling grating layer are arranged closely together along the plane above the substrate. The capping layer and the electrical contact layer are arranged from bottom to top above the functional layer composed of the modulator layer, the front sampling grating layer, the gain layer, and the back sampling grating layer.
[0020] The capping layer and the electrical contact layer together form a shallow ridge waveguide structure. The shallow ridge waveguide structure is located laterally at the center of the upper surface of the modulator layer, the front sampling grating layer, the gain layer and the back sampling grating layer. It is formed by etching the entire capping layer and the electrical contact layer according to a predetermined ridge strip pattern.
[0021] A cantilever beam structure is laterally arranged in the post-sampling grating layer. The cantilever beam structure includes a cantilever beam and air slots symmetrically distributed on both sides. The cantilever beam is located directly below the shallow ridge waveguide structure. The cantilever beam structure is formed by etching the post-sampling grating layer located below the shallow ridge waveguide structure according to a predetermined cantilever strip pattern.
[0022] Furthermore, the gain layer is disposed in the gain region of the substrate, and from bottom to top, it includes a second lower confinement layer, a second multiple quantum well layer, and a second upper confinement layer; the modulator layer is disposed in the modulator region of the substrate by docking growth, and from bottom to top, it includes a first lower confinement layer, a first multiple quantum well layer, and a first upper confinement layer, wherein the photofluorescence wavelength of the second multiple quantum well layer is shorter than the photofluorescence wavelength of the first multiple quantum well layer by a first predetermined wavelength value.
[0023] Furthermore, the front sampling grating layer and the rear sampling grating layer are respectively disposed in the front grating region and the rear grating region of the substrate by docking growth. Periodically arranged micro-reflective structures are etched on the front sampling grating layer and the rear sampling grating layer, wherein the photofluorescence wavelength of the front sampling grating layer and the rear sampling grating layer is shorter than the photofluorescence wavelength of the second quantum layer by a second predetermined wavelength value.
[0024] Furthermore, electrical isolation trenches are etched on the electrical contact layer, and the electrical isolation trenches are located between two adjacent regions arranged in a predetermined direction on the substrate.
[0025] Furthermore, corresponding P-side electrodes are respectively disposed above the electrical contact layers corresponding to the modulator layer, the front sampling grating layer, and the gain layer. A heating resistor is disposed above the electrical contact layer corresponding to the rear sampling grating layer. The heating resistor includes a positive electrode and a negative electrode, which are used to provide heating power to the rear sampling grating layer for thermal tuning of the grating layer. An N-side electrode is disposed below the substrate.
[0026] The beneficial effects of this application are:
[0027] First, the technical solution in this application processes the capping layer and electrical contact layer into a shallow ridge waveguide structure, and fabricates a cantilever beam and air slots on both sides of the post-sampling grating layer below the shallow ridge waveguide structure, thereby forming a cantilever beam grating structure that cooperates with the shallow ridge waveguide to achieve effective thermal isolation between the grating region and the surrounding materials. Simultaneously, a titanium-platinum heating resistor is set in the electrical contact layer above the post-sampling grating layer, and the post-sampling grating layer is thermally tuned by heating the resistor. The technical solution in this application, through the synergistic design of the shallow ridge waveguide structure and the cantilever beam grating structure, forms a local thermal isolation and heat concentration area in the grating region, significantly improving the temperature rise efficiency of the grating region and increasing the magnitude of the material's refractive index change. This achieves a larger wavelength redshift and tuning range than traditional current tuning, resulting in a faster temperature rise and more significant refractive index change in the cantilever beam grating region under the same tuning current conditions, achieving a temperature rise exceeding 12°C within the 0–20 mA current range. Wavelength tuning of nm; in contrast, traditional current tuning schemes based on carrier injection / depletion require 0–80 mA current to achieve the same tuning range, while the scheme in this application uses heating resistors for thermal tuning. Due to the strong thermal accumulation effect of the material, the tuning range is not limited by the carrier concentration of the material. The scheme in this application has fast thermal response, reduced power consumption, and improved wavelength tuning efficiency and range.
[0028] Secondly, the technical solution of this invention sets a cantilever beam structure in the second sampling grating layer and uses a heating resistor to perform local thermal control on the cantilever beam structure, thereby achieving wavelength tuning. This simplifies the complex multi-channel current coordinated control to direct control using heating resistors, significantly simplifying the external control system. Since the thermal tuning process is highly concentrated in the cantilever beam section of the second grating region, the coupling effect between current changes in different sections is weak, resulting in minimal impact on the performance of the gain and modulation regions. The modulation region only needs one RF signal to carry data, and wavelength tuning only needs one control current, simplifying the external control system. This design no longer relies on multiple high-precision constant current sources and complex real-time feedback algorithms; by adjusting the heating current, the target wavelength switching and control can be achieved efficiently and stably, avoiding the complexity of multi-segment current coordinated control in traditional solutions, while improving the system's control response speed and overall reliability. Attached Figure Description
[0029] The advantages of the above and / or additional aspects of this application will become apparent and readily understood in the description of the embodiments in conjunction with the following drawings, wherein:
[0030] Figure 1 This is a schematic diagram of the overall structure of a wavelength thermally tunable photonic integrated device according to an embodiment of this application;
[0031] Figure 2 This is a schematic diagram of the structure after the growth of the gain layer according to an embodiment of this application;
[0032] Figure 3 This is a schematic diagram of the structure after removing the gain layer material in the modulator region according to an embodiment of this application;
[0033] Figure 4 This is a schematic diagram of the structure after the growth modulator layer according to an embodiment of this application;
[0034] Figure 5 This is a schematic diagram of the structure after removing the layer material in the front and rear grating regions according to an embodiment of this application;
[0035] Figure 6 This is a schematic diagram of the structure after pre-growing sampling grating layer and post-growing sampling grating layer according to an embodiment of this application;
[0036] Figure 7 This is a schematic diagram of the structure after the growth of the capping layer and the electrical contact layer according to an embodiment of this application;
[0037] Figure 8 This is a schematic diagram of a cantilever beam structure according to an embodiment of this application;
[0038] Figure 9 This is a top view of a cantilever beam structure according to an embodiment of this application;
[0039] Figure 10 This is a side section view of a cantilever beam structure according to an embodiment of this application;
[0040] Figure 11 This is a schematic diagram of the structure of each N-face electrode and heating resistor according to an embodiment of this application.
[0041] Among them, 10-substrate, 11-modulator layer, 111-first lower confinement layer, 112-first multiple quantum well layer, 113-first upper confinement layer, 12-front sampling grating layer, 13-gain layer, 131-second lower confinement layer, 132-second multiple quantum well layer, 133-second upper confinement layer, 14-back sampling grating layer, 141-cantilever beam, 142-air groove, 15-capping layer, 16-electrical contact layer, 161-electrical isolation trench, 17-micro-reflective structure, 18-modulator region electrode, 19-front grating region electrode, 20-gain region electrode, 21-heating resistor, 211-positive electrode, 212-negative electrode, 22-N-surface electrode, 23-mask. Detailed Implementation
[0042] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other.
[0043] In the following description, many specific details are set forth in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.
[0044] This embodiment takes the InP-based material system as an example. The following is a general introduction to a direct modulation laser array chip and its fabrication method in this embodiment of the invention.
[0045] like Figures 1 to 8 As shown, this embodiment provides a wavelength thermally tunable photonic integrated device, which includes a substrate 10, a modulator layer 11, a front sampling grating layer 12, a gain layer 13, a rear sampling grating layer 14, a capping layer 15, and an electrical contact layer 16.
[0046] The modulator layer 11, the front sampling grating layer 12, the gain layer 13, and the rear sampling grating layer 14 are arranged closely in sequence along the upper plane of the substrate 10. The capping layer 15 and the electrical contact layer 16 are arranged from bottom to top above the functional layer composed of the modulator layer 11, the front sampling grating layer 12, the gain layer 13, and the rear sampling grating layer 14. The corresponding P-side electrodes are respectively arranged above the electrical contact layers 16 of the modulator layer 11, the front sampling grating layer 12, and the gain layer 13. The heating resistor 21 is arranged above the electrical contact layer 16 of the rear sampling grating layer 14. The N-side electrode 22 is arranged below the substrate 10.
[0047] The substrate 10 is divided into a modulator region (EAM), a front grating region (FG), a gain region (G), and a rear grating region (BG) along a preset direction, with adjacent regions closely connected.
[0048] The gain layer 13 is disposed in the gain region of the substrate 10 and is used to provide a light source and gain medium for the device to emit light. The gain layer 13 generates photon gain by injecting current, enabling the device to emit tunable light signals. By applying different DC voltages in the gain region, multiple lasers of different wavelengths can be excited to meet the multi-wavelength requirements of the device.
[0049] Specifically, the gain layer 13 includes, from bottom to top, a second lower confinement layer 131, a second multi-quantum layer 132, and a second upper confinement layer 133. The second multi-quantum layer 132 is an active layer that provides laser gain. The second lower confinement layer 131 and the second upper confinement layer 133 are used to form the lower and upper barriers of the quantum well, respectively, to restrict the movement of charge carriers in the quantum well, prevent diffusion, and ensure the stability of the optical field and the distribution of charge carriers.
[0050] The modulator layer 11 is disposed in the modulator region of the substrate 10 by docking growth and is used for electro-absorption modulation of optical signals. Applying a reverse voltage (e.g., 0-3V) to the modulator region causes a wavelength redshift, enhancing the absorption of the emitted laser and achieving controllable attenuation of light intensity. Furthermore, a radio frequency (RF) signal is superimposed on the reverse bias voltage, causing the electric field at both ends of the modulator to change rapidly over time, resulting in a periodic change in the absorption coefficient. When the applied RF signal is at a high level, the total reverse voltage increases, absorption is enhanced, and the output light intensity decreases; when the RF signal is at a low level, the total reverse voltage decreases, absorption is weakened, and the output light intensity increases. Through this electric field modulation, the high and low levels of the electrical signal can be mapped to the "0" and "1" states of the optical signal, respectively, thereby achieving high-speed intensity modulation of continuous laser light and improving the optical signal transmission rate and modulation accuracy. When operating, this modulator can support optical signal modulation and transmission rates exceeding 100 Gbps (i.e., 100 billion bits per second).
[0051] Specifically, the modulator layer 11 comprises, from bottom to top, a first lower confinement layer 111, a first multiple quantum well layer 112, and a first upper confinement layer 113. The first multiple quantum well layer 112 is an active absorption layer used to absorb and modulate optical signals under the action of an external electric field. The first lower confinement layer 111 and the first upper confinement layer 113 are used to form the lower and upper potential barriers of the quantum wells, respectively, to restrict the movement of charge carriers within the quantum wells (i.e., confine the charge carriers and light within the active layer), prevent diffusion, and ensure the stability of the optical field and charge carrier distribution. The photofluorescence wavelength of the second multiple quantum well layer is 60 nm shorter than that of the first multiple quantum well layer 112.
[0052] The front sampling grating layer 12 is disposed in the front grating region of the substrate 10 by a docking growth method, and is located between the modulator layer 11 and the gain layer 13. Periodically arranged micro-reflective structures 17 are etched on it; the front sampling grating layer 12 is used to reflect the optical signal in the laser cavity.
[0053] The post-sampling grating layer 14 is disposed on the post-grating region of the substrate 10 by a docking growth method and is located on the other side of the gain layer 13. Periodically arranged micro-reflective structures 17 are also etched on it. The post-sampling grating layer 14 is used to change the effective refractive index and reflection phase through thermal tuning to achieve fine wavelength tuning of the output optical signal and ensure stable single-mode output (selecting the center wavelength of the main mode of the optical signal in the laser cavity).
[0054] It should be noted that the front sampling grating layer 12, the gain layer 13, and the rear sampling grating layer 14 together constitute the overall structure of the laser resonant cavity. The front sampling grating layer 12 is disposed on one side of the gain layer 13 and is used to form the front reflection structure of the laser resonant cavity (its main function is reflection). The rear sampling grating layer 14 is disposed on the other side of the gain layer 13 and is used to form the rear reflection structure of the laser resonant cavity (its main function is wavelength tuning). Thermal tuning is performed by heating resistor 21 to change the refractive index and reflection phase of the grating region, thereby achieving phase compensation and fine wavelength tuning of the output optical signal wavelength. The two work together to achieve continuous and controllable single-mode wavelength output.
[0055] The electrical contact layer 16 is located above the capping layer 15. The capping layer 15 and the electrical contact layer 16 together form a shallow ridge waveguide structure. This shallow ridge waveguide structure is laterally disposed at the center of the upper surface of the modulator layer 11, the front sampling grating layer 12, the gain layer 13, and the rear sampling grating layer 14. It is formed by etching the capping layer 15 and the electrical contact layer 16 above the entire functional layer consisting of the modulator layer 11, the front sampling grating layer 12, the gain layer 13, and the rear sampling grating layer 14 according to a predetermined ridge strip pattern. The capping layer 15 is used to protect the underlying structure and control the current distribution, while the electrical contact layer 16 is used to achieve good ohmic contact.
[0056] It should be noted that the capping layer 15 and the electrical contact layer 16 are formed after partial etching, as shown in the figure. Figure 8 The ridge structure shown has an etching depth that does not penetrate into the active layer (i.e., the modulator layer 11, the front sampling grating layer 12, the gain layer 13, and the rear sampling grating layer 14 below), but only within the capping layer 15 and the electrical contact layer 16. The shallow ridge waveguide structure can improve carrier injection efficiency and optimize electro-optic conversion performance through the refractive index difference in shape and the current confinement effect; at the same time, it can also achieve lateral confinement of light waves and current, reduce optical losses, and improve the stability and reliability of the device.
[0057] In this embodiment, the horizontal direction from the modulator layer 11 to the post-sampled grating layer 14 (i.e., the preset reverse direction) is taken as the lateral direction, such as... Figure 8 As shown, the shallow ridge waveguide structure is laterally distributed along the horizontal direction from the modulator layer 11 to the post-sample grating layer 14.
[0058] A cantilever beam structure is laterally arranged in the post-sampling grating layer 14. The cantilever beam structure includes a cantilever beam 141 and air slots 142 symmetrically distributed on both sides. The cantilever beam 141 is located directly below the shallow ridge waveguide structure. The cantilever beam structure is formed by etching the post-sampling grating layer 14 located below the shallow ridge waveguide structure according to a predetermined cantilever strip pattern.
[0059] Electrical isolation trenches 161 are also etched on the electrical contact layer 16. The electrical isolation trenches 161 are located between two adjacent regions arranged in a preset direction on the substrate 10, and are used to electrically isolate the modulator region, the front grating region, the gain region and the rear grating region.
[0060] Above the electrical contact layer 16 corresponding to the modulator layer 11, the front sampling grating layer 12, and the gain layer 13, respectively, there are modulator region electrodes 18, front grating region electrodes 19, and gain region electrodes 20. The gain region electrode 20 is used to connect the driving current to the gain layer 13, the front grating region electrode 19 is used to connect the driving current to the front sampling grating layer 12, and the modulator region electrode 18 is used to connect the radio frequency signal to the modulator layer 11.
[0061] A heating resistor 21, located above the electrical contact layer 16 corresponding to the post-sampling grating layer 14, includes a positive electrode 211 and a negative electrode 212. The positive electrode 211 and the negative electrode 212 are used to connect to the positive and negative terminals of an external power supply, respectively. The heating resistor 21 provides heating power to the post-sampling grating layer 14 for thermal tuning, thereby adjusting the wavelength of the output optical signal. An N-plane electrode 22 is located below the substrate 10 to provide a common current loop for the entire device.
[0062] A silicon nitride insulating film is also disposed above the electrical contact layer 16. This silicon nitride insulating film is located below the modulator region electrode 18, the front grating region electrode 19, the gain region electrode 20, and the heating resistor 21. It is used to achieve electrical insulation, surface passivation, and structural protection. At the same time, it serves as an upper cladding layer in optics to suppress surface state recombination and metal absorption, thereby improving device stability and tuning efficiency.
[0063] It should be noted that, in the InP-based material system, substrate 10 is an N-type InP substrate (indium phosphide), modulator layer 11 is an InGaAsP (indium gallium arsenide phosphide) active material, front sampling grating layer 12 and back sampling grating layer 14 are InGaAsP grating materials, gain layer 13 is an InGaAsP active material, capping layer 15 is an InP cladding material, and electrical contact layer 16 is an InGaAs contact layer material. Each layer uses materials with the same composition but different proportions to achieve different effects. The P-side electrode can be made of titanium, and the N-side electrode can be made of gold-germanium-nickel alloy to reduce contact resistance and improve the current-to-light output characteristics of the laser.
[0064] like Figure 1 As shown, this embodiment provides a method for fabricating a wavelength-tunable photonic integrated device, including:
[0065] S1: Prepare substrate 10, and divide the modulator region, front grating region, gain region and rear grating region into the substrate 10 in a preset direction, with adjacent regions closely connected.
[0066] S2: Grow a gain layer material on the entire surface of the substrate 10 to form a gain layer 13. The gain layer 13 is located in the gain region. Selectively remove the gain layer material in the modulator region and grow a modulator layer 11. The photofluorescence wavelength of the modulator layer 11 is shorter than the photofluorescence wavelength of the gain layer 13 by a first predetermined wavelength value. The first predetermined wavelength value can be set to 60 nm.
[0067] Specifically, gain layer material is grown layer by layer from bottom to top on substrate 10 to form gain layer 13, which consists of a second lower confinement layer 131, a second multiple quantum well layer, and a second upper confinement layer 133. Gain layer 13 is located in the gain region. Gain layer material in front grating region, gain region and back grating region is covered with mask 23. Gain layer material in modulator region is removed by reactive ion etching equipment and sulfuric acid etching. Modulator layer material is grown layer by layer from bottom to top in modulator region by metal-organic chemical vapor deposition equipment. Mask 23 is removed to form modulator layer 11, which consists of a first lower confinement layer 111, a first multiple quantum well layer 112 and a first upper confinement layer 113. The photofluorescence wavelength of the second multiple quantum well layer is 60 nm shorter than the photofluorescence wavelength of the first multiple quantum well layer 112.
[0068] In this embodiment, the material of the mask 23 can be silicon dioxide, and the mask 23 can be prepared by etching, such as forming a silicon dioxide thin film layer with a predetermined pattern by photolithography. After the operation of removing the gain layer material of the modulator region is completed, the mask 23 is removed by wet etching or dry etching.
[0069] S3: Selectively remove the gain layer material of the front grating region and the rear grating region and grow the grating layer material. Create periodically arranged micro-reflective structures 17 on the grating layer material to form a patterned front sampling grating layer 12 and a rear sampling grating layer 14. The photofluorescence wavelength of the front sampling grating layer 12 and the rear sampling grating layer 14 is shorter than the photofluorescence wavelength of the gain layer 13 by a second predetermined wavelength value. The second predetermined wavelength value can be set to 100 nm.
[0070] Specifically, a mask 23 is used to cover the modulator layer 11 and the gain layer 13. The gain layer material of the front grating region and the back grating region is removed by reactive ion etching and sulfuric acid etching. The grating layer material is grown by mating the front grating region and the back grating region using metal-organic chemical vapor deposition. The mask 23 is removed, and periodically arranged micro-reflective structures 17 are etched on the grating layer material to form a patterned front sampling grating layer 12 and a back sampling grating layer 14.
[0071] In this embodiment, a periodically arranged micro-reflective structure 17 is fabricated above the grating layer material. This can be achieved by photolithography and dry etching. A periodic patterned mask 23 is formed by photolithography, and then the microstructure is etched using reactive ion etching or deep silicon etching processes.
[0072] S4: A capping layer 15 and an electrical contact layer 16 are grown sequentially from bottom to top above the entire functional layer consisting of modulator layer 11, front sampling grating layer 12, gain layer 13 and rear sampling grating layer 14. The capping layer 15 and the electrical contact layer 16 are etched according to a predetermined ridge strip pattern to form a shallow ridge waveguide structure. The shallow ridge waveguide structure is laterally distributed at the center of the upper surface of modulator layer 11, front sampling grating layer 12, gain layer 13 and rear sampling grating layer 14.
[0073] Specifically, a transverse strip mask is first fabricated at the center of the electrical contact layer 16. The entire capping layer 15 and the electrical contact layer 16 are then dry-etched with SiCl4 gas to form a shallow ridge structure. Next, the two sides of the shallow ridge structure are modified by wet etching with HCl solution to finally form a shallow ridge waveguide structure that conforms to the predetermined ridge strip pattern. The etching depth is controlled within the capping layer 15 and does not penetrate the capping layer 15 to the material layer below it. Electrical isolation trenches 161 are etched on the electrical contact layer 16 located between two adjacent regions to form electrical isolation between the modulator region, the front grating region, the gain region, and the rear grating region, avoiding current interference between the functional regions and ensuring independent driving and tuning of each region.
[0074] In this embodiment, the etching of the electrical isolation trench 161 can be carried out by photolithography and dry etching. For example, the patterned mask 23 corresponding to the electrical isolation trench 161 can be formed by photolithography, and then the electrical isolation trench 161 can be etched on the electrical contact layer 16 between adjacent regions by reactive ion etching or deep silicon etching process, and finally the mask 23 can be removed.
[0075] S5: According to the predetermined cantilever strip pattern, the material in the region below the shallow ridge waveguide structure in the post-sampling grating layer 14 is etched to form a cantilever beam structure, which includes a cantilever beam 141 and air slots 142 symmetrically distributed on both sides.
[0076] The positions corresponding to the air grooves 142 on both sides of the cantilever beam 141 are marked on the upper surface of the post-sampling grating layer 14. A mask with a cantilever strip pattern is fabricated on the entire device using photolithography. The mask 23 is used to cover the positions other than the positions of the air grooves 142. The grating layer material corresponding to the positions of the air grooves 142 is removed using reactive ion etching equipment and hydrobromic acid etching to form a cantilever beam structure. The cantilever beam structure includes the cantilever beam 141 located directly below the shallow ridge waveguide structure and the air grooves 142 located on both sides of the cantilever beam 141. The etching depth is controlled within the post-sampling grating layer 14 and does not penetrate the post-sampling grating layer 14 to the substrate 10 below it.
[0077] S6: P-side electrodes are fabricated above the electrical contact layers 16 in the modulator region, front grating region, and gain region, respectively. A heating resistor 21 is fabricated above the electrical contact layer 16 in the rear grating region. An N-side electrode 22 is fabricated below the substrate 10.
[0078] Specifically, a silicon nitride insulating film is grown on top of the entire device to achieve electrical insulation, surface passivation, and structural protection. Optically, it serves as an upper cladding layer to suppress surface state recombination and metal absorption, improving device stability and tuning efficiency. Then, P-plane electrodes are fabricated on the electrical contact layers 16 in the modulator region, front grating region, and gain region, forming the modulator region electrode 1830, the front grating region electrode 19, and the gain region electrode 20, respectively. A heating resistor 21 is fabricated on the electrical contact layer 16 in the rear grating region using titanium-platinum material. The heating resistor 21 includes a positive electrode 211 and a negative electrode 212, used to connect to the positive and negative terminals of an external power supply, respectively. The titanium-platinum heating resistor has a strong bond with the silicon nitride insulating film, and this combination improves the heating efficiency after energization.
[0079] It should be noted that existing tunable lasers generally employ current tuning methods based on carrier injection or depletion effects. This method relies on the influence of changes in carrier concentration in the semiconductor on the refractive index. Due to limitations imposed by the carrier concentration in the material, the range of refractive index changes is limited, resulting in a relatively small wavelength tuning range. Furthermore, a large current is required to accumulate sufficient carriers, leading to high power consumption. In contrast, this invention employs a cantilever beam structure to achieve thermal tuning. Its tuning mechanism is based on the sensitivity of the semiconductor refractive index (changes in the refractive index of the grating material cause changes in the grating period, which in turn alters the laser's lasing wavelength, thus achieving wavelength tuning) to temperature variations. The cantilever beam structure is not just a conventional thermal tuning, but enhances the temperature rise efficiency of the grating region through thermal isolation and local heat concentration effects. Specifically, a cantilever beam 141 and air slots 142 on both sides are set in the post-sampling grating layer 14 to thermally isolate the grating region from the surrounding materials, forming a local heat concentration area with fast response and no limitation by heat diffusion. Therefore, under the same current, the temperature rises faster in the cantilever beam 141 region, the material refractive index changes more significantly, and the heat accumulation effect is significant. The refractive index change amplitude is larger than that of current tuning, and the wavelength can be significantly redshifted, achieving a larger wavelength tuning range than traditional current tuning, while significantly reducing tuning current and power consumption.
[0080] The wavelength thermally tunable photonic integrated device fabricated using the method described in this application is tested using the following specific steps:
[0081] An 80 mA DC current is applied to the gain region, causing stimulated emission in the gain layer 13, resulting in normal light emission and output of a laser signal. A 0-3 V reverse voltage is applied to the modulator region to achieve absorption modulation of the output laser signal. By changing the magnitude of the reverse voltage, the intensity of the output laser signal is adjusted to a preset value for subsequent experimental observation. A 0-50 mA current is applied to the front grating electrode 19 in the front grating region to achieve laser mode selection. A 0-50 mA current is applied to the heating resistor 21 in the rear grating region (gradually changing from 0 to 50 mA). By locally heating the grating region, thermal tuning of the laser output wavelength is achieved. The center wavelength of the laser output is measured at each current point, and the tuning range of the wavelength as a function of the current in the heating resistor 21 is recorded to obtain the final test results.
[0082] The test results show that the wavelength tuning of more than 12 nm can be achieved with the current in the rear grating region within the range of 0-20 mA. In contrast, the traditional current tuning method requires 0-80 mA to achieve the same wavelength tuning range. Therefore, the present invention significantly reduces power consumption.
[0083] The steps in this invention can be adjusted, combined, or deleted according to actual needs.
[0084] The units in the device of the present invention can be merged, divided, or reduced according to actual needs.
[0085] In this invention, the terms "installation," "connection," "linking," and "fixing" should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "linking" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.
[0086] The shapes of the components in the accompanying drawings are schematic and may differ from their actual shapes. The drawings are only used to illustrate the principles of the present invention and are not intended to limit the present invention.
[0087] Although the invention has been disclosed in detail with reference to the accompanying drawings, it should be understood that these descriptions are merely exemplary and not intended to limit the application of the invention. The scope of protection of the invention is defined by the appended claims and may include various modifications, alterations, and equivalents made to the invention without departing from the scope and spirit of the invention.
Claims
1. A method for fabricating a wavelength-modulated photonic integrated device, characterized in that, The method includes: S1: Prepare substrate (10), and divide the modulator area, front grating area, gain area and rear grating area in sequence according to the preset direction on the substrate (10), with adjacent areas closely connected; S2: Grow gain layer material on the entire surface of the substrate (10) to form a gain layer (13), wherein the gain layer (13) is located in the gain region. Selectively remove the gain layer material in the modulator region and grow the modulator layer (11). S3: Selectively remove the gain layer material of the front grating region and the back grating region and grow the grating layer material. Create a periodically arranged micro-reflection structure (17) on the grating layer material to form a patterned front sampling grating layer (12) and a back sampling grating layer (14). S4: A capping layer (15) and an electrical contact layer (16) are grown sequentially above the entire functional layer consisting of the modulator layer (11), the front sampling grating layer (12), the gain layer (13), and the rear sampling grating layer (14). The capping layer (15) and the electrical contact layer (16) are etched according to a predetermined ridge strip pattern to form a shallow ridge waveguide structure. The shallow ridge waveguide structure is laterally distributed at the center of the upper surface of the modulator layer (11), the front sampling grating layer (12), the gain layer (13), and the rear sampling grating layer (14). S5: According to the predetermined cantilever strip pattern, the material in the area below the shallow ridge waveguide structure in the post-sampling grating layer (14) is etched to form a cantilever beam structure, which includes a cantilever beam (141) and air slots (142) symmetrically distributed on both sides. S6: P-side electrodes are fabricated above the electrical contact layers (16) of the modulator region, the front grating region, and the gain region, respectively. A heating resistor (21) is fabricated above the electrical contact layer (16) of the rear grating region. An N-side electrode (22) is fabricated below the substrate (10).
2. The fabrication method of the wavelength thermally tunable photonic integrated device as described in claim 1, characterized in that, S2 specifically includes: Gain layer material is grown layer by layer from bottom to top on substrate (10) to form a gain layer (13) consisting of a second lower confinement layer (131), a second multiple quantum well layer (132) and a second upper confinement layer (133). Gain layer material of front grating region, gain region and back grating region is covered with a mask. Gain layer material of modulator region is etched away. Modulator layer material is grown layer by layer from bottom to top in modulator region. Mask is removed to form modulator layer (11) consisting of first lower confinement layer (111), first multiple quantum well layer (112) and first upper confinement layer (113).
3. The fabrication method of the wavelength thermally tunable photonic integrated device as described in claim 1, characterized in that, In step S4, the capping layer (15) and the electrical contact layer (16) are etched according to a predetermined ridge-shaped strip pattern, specifically including: First, a transverse strip mask is made at the center of the electrical contact layer (16). The entire capping layer (15) and electrical contact layer (16) are etched by SiCl4 gas dry etching to form a shallow ridge structure. Then, the two sides of the shallow ridge structure are modified by HCl solution wet etching to finally form a shallow ridge waveguide structure that conforms to the predetermined ridge strip pattern. The etching depth is controlled inside the capping layer (15) and does not penetrate the capping layer (15) to the material layer below it.
4. The fabrication method of the wavelength thermally tunable photonic integrated device as described in claim 3, characterized in that, S4 further includes: Electrical isolation trenches (161) are etched on the electrical contact layer (16) located between two adjacent regions to form electrical isolation between the modulator region, the front grating region, the gain region and the rear grating region, so as to avoid mutual interference of current in each functional region.
5. The fabrication method of the wavelength thermally tunable photonic integrated device as described in claim 1, characterized in that, S5 specifically includes: The positions corresponding to the air slots (142) on both sides of the cantilever beam (141) are divided on the upper surface of the post-sampling grating layer (14). A mask with a cantilever strip pattern is made on the entire device. The mask is used to cover the positions other than the positions of the air slots (142). The grating layer material corresponding to the positions of the air slots (142) is removed by reactive ion etching equipment and hydrobromic acid etching to form a cantilever beam structure.
6. A wavelength-thermally tunable photonic integrated device fabricated using the fabrication method of any one of claims 1-5, characterized in that, The wavelength-modulated photonic integrated device includes: a substrate (10), a modulator layer (11), a front sampling grating layer (12), a gain layer (13), a back sampling grating layer (14), a capping layer (15), and an electrical contact layer (16). The modulator layer (11), the front sampling grating layer (12), the gain layer (13) and the back sampling grating layer (14) are arranged closely along the plane above the substrate (10), and the capping layer (15) and the electrical contact layer (16) are arranged from bottom to top above the functional layer composed of the modulator layer (11), the front sampling grating layer (12), the gain layer (13) and the back sampling grating layer (14); The capping layer (15) and the electrical contact layer (16) together form a shallow ridge waveguide structure. The shallow ridge waveguide structure is located laterally at the center of the upper surface of the modulator layer (11), the front sampling grating layer (12), the gain layer (13) and the rear sampling grating layer (14). It is formed by etching the entire capping layer (15) and the electrical contact layer (16) according to a predetermined ridge strip pattern. A cantilever beam structure is laterally arranged in the post-sampling grating layer (14). The cantilever beam structure includes a cantilever beam (141) and air slots (142) symmetrically distributed on both sides. The cantilever beam (141) is located directly below the shallow ridge waveguide structure. The cantilever beam structure is formed by etching the post-sampling grating layer (14) located below the shallow ridge waveguide structure according to a predetermined cantilever strip pattern.
7. The wavelength-thermally tunable photonic integrated device as described in claim 6, characterized in that, The gain layer (13) is disposed in the gain region of the substrate (10), and from bottom to top, it includes a second lower confinement layer (131), a second multiple quantum well layer (132), and a second upper confinement layer (133); the modulator layer (11) is disposed in the modulator region of the substrate (10) by docking growth, and from bottom to top, it includes a first lower confinement layer (111), a first multiple quantum well layer (112), and a first upper confinement layer (113), wherein the photofluorescence wavelength of the second multiple quantum well layer (132) is shorter than the photofluorescence wavelength of the first multiple quantum well layer (112) by a first predetermined wavelength value.
8. The wavelength-thermally tunable photonic integrated device as described in claim 7, characterized in that, The front sampling grating layer (12) and the rear sampling grating layer (14) are respectively disposed in the front grating region and the rear grating region of the substrate (10) by a docking growth method. Periodically arranged micro-reflective structures (17) are etched on the front sampling grating layer (12) and the rear sampling grating layer (14). The photofluorescence wavelength of the front sampling grating layer (12) and the rear sampling grating layer (14) is shorter than the photofluorescence wavelength of the second quantum well layer (132) by a second predetermined wavelength value.
9. The wavelength thermally tunable photonic integrated device as described in claim 6, characterized in that, An electrical isolation trench (161) is also etched on the electrical contact layer (16), and the electrical isolation trench (161) is located between two adjacent regions arranged in a preset direction on the substrate (10).
10. The wavelength-thermally tunable photonic integrated device as described in claim 6, characterized in that, The modulator layer (11), the front sampling grating layer (12), and the gain layer (13) are respectively provided with corresponding P-side electrodes on the electrical contact layer (16). The rear sampling grating layer (14) is provided with a heating resistor (21) on the electrical contact layer (16). The heating resistor (21) includes a positive electrode (211) and a negative electrode (212) for providing heating power to the rear sampling grating layer (14) to thermally tune the grating layer. The substrate (10) is provided with an N-side electrode (22).