A short wavelength narrow linewidth semiconductor laser based on coupled cavities

Abstract

This application provides a short-wavelength, narrow-linewidth semiconductor laser based on a coupled cavity and its fabrication method, relating to the field of semiconductor laser technology. The semiconductor laser includes a first optical resonant cavity, a second deep optical resonant cavity, a deep etched groove, an injection electrode for the first optical resonant cavity, an injection electrode for the second optical resonant cavity, and a phase-tuning electrode for the second optical resonant cavity. The two optical resonant cavities are located on the same epitaxial wafer, simplifying the fabrication process, eliminating the need for secondary epitaxy, reducing manufacturing costs, and facilitating mass production. The two optical resonant cavities have different lengths and are coupled together through the deep etched groove, enabling common mode selection to ensure single-mode operation of the laser. By jointly adjusting the injection current of the three electrodes, the single-mode narrow-linewidth characteristics and operating wavelength of the laser are controlled, resulting in a wide tunable wavelength range. The structure lacks relatively high-loss structures such as gratings and coupling alignment, which is beneficial for high-power (>50mW) operation of the laser and allows for further narrowing of the linewidth.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a short-wavelength, narrow-linewidth semiconductor laser based on a coupled cavity and its fabrication method. Background Technology

[0002] The main implementation schemes for short-wavelength, narrow-linewidth semiconductor lasers are frequency doubling and non-frequency doubling.

[0003] Frequency doubling schemes require a tuning mechanism to meet the phase-matching conditions for nonlinear effects, making integration and miniaturization difficult. Non-frequency doubling schemes require grating structures, which are complex to manufacture, prone to multimode oscillations, and have poor linewidth stability.

[0004] A small number of two-stage photocells with similar coupling structures use thermoelectric phase modulation, resulting in weak phase adjustment capabilities and the heating effect affecting the laser's linewidth performance. Furthermore, the use of only a single electrode makes it difficult to achieve precise wavelength control. Summary of the Invention

[0005] This application provides a short-wavelength, narrow-linewidth semiconductor laser based on a coupled cavity and its fabrication method, which realizes the coupling of two resonant cavities and can simultaneously meet the requirements of narrow linewidth (<1MHz) and fine wavelength tuning.

[0006] To achieve the above objectives, embodiments of this application provide the following technical solutions: On one hand, a short-wavelength, narrow-linewidth semiconductor laser based on a coupled cavity is provided. The laser includes three regions: an active region of a first optical resonant cavity, an active region of a second optical resonant cavity, and a passive region of a second optical resonant cavity. Furthermore, the laser includes a common electrode, a first substrate, a first core region, a quantum well layer, a second core region, a quantum well disordering layer, a second substrate, a first optical resonant cavity injection electrode, a second optical resonant cavity injection electrode, and a second optical resonant cavity phase-tuning electrode. The first substrate is disposed on the common electrode. The first core region is disposed on the side of the first substrate away from the common electrode and is located within the active regions of both the first and second optical resonant cavities. The quantum well layer is disposed on the side of the first core region away from the common electrode and is located within both the active regions of both the first and second optical resonant cavities. The second core region is disposed on the side of the quantum well layer away from the common electrode and is located within both the active regions of both the first and second optical resonant cavities. A quantum well disordering layer is disposed on the side of the first substrate away from the common electrode and located in the passive region of the second optical resonator. A second substrate is disposed on the side of the second core region away from the common electrode and on the side of the quantum well disordering layer away from the common electrode. A first optical resonator injection electrode is disposed on the side of the second substrate away from the common electrode and located in the active region of the first optical resonator. A second optical resonator injection electrode is disposed on the side of the second substrate away from the common electrode and located in the active region of the second optical resonator. A second optical resonator phase-tuning electrode is disposed on the side of the second substrate away from the common electrode and located in the passive region of the second optical resonator.

[0007] In the above embodiments of this application, the laser includes two optical resonant cavities, namely a first optical resonant cavity and a second optical resonant cavity, and the two optical resonant cavities use ridge waveguides for lateral mode confinement. The structure has no gratings, coupling alignment, or other relatively high-loss structures, which is beneficial for the high-power (>50mW) operation of the laser and can further narrow the linewidth.

[0008] The entire first optical resonator is an active structure (the active region of the first optical resonator), and the injection electrode of the first optical resonator is a single electrode that controls the laser current (equivalent to controlling the injection current density). The second optical resonator includes an active region and a passive region (the active region of the second optical resonator and the passive region of the second optical resonator). The passive region is realized by using rapid thermal annealing and selective surface coating with a silicon dioxide film to induce quantum well disordering, thereby forming a quantum well disordered layer in the passive region. Each of the active and passive regions has one electrode (the injection electrode of the second optical resonator and the phase-tuning electrode of the second optical resonator) to control the injection current density in the two regions respectively.

[0009] By jointly adjusting the injection current of the three electrodes (the first optical resonant cavity injection electrode, the second optical resonant cavity injection electrode, and the second optical resonant cavity phase-tuning electrode), the coupling of the two resonant cavities can be achieved, which can simultaneously meet the requirements of narrow linewidth (<1MHz) and fine wavelength tuning.

[0010] In some embodiments, along a first direction, the active region of the first optical resonator, the active region of the second optical resonator, and the passive region of the second optical resonator are sequentially connected, and the first direction is parallel to the plane where the common electrode is located. The laser also includes a deep etching groove located at the junction of the active regions of the first and second optical resonators. Furthermore, the deep etching groove penetrates the second substrate, the second core region, the quantum well disordering layer, and the first core region, and extends into the first substrate.

[0011] In some embodiments, along the first direction, the first optical resonant cavity includes opposing first and second partial reflective surfaces, and the second optical resonant cavity includes opposing first and second partial reflective surfaces. The deep etched groove includes two opposing sides in the first direction, wherein the side closest to the active region of the first optical resonant cavity is the second partial reflective surface of the first optical resonant cavity. The side closest to the active region of the second optical resonant cavity is the second partial reflective surface of the second optical resonant cavity.

[0012] In some embodiments, along the first direction, the width of the deep etched groove is a half-integer multiple of the operating wavelength of the laser.

[0013] In some embodiments, the depth of the deep etch trench is greater than or equal to 3 μm in a direction perpendicular to the plane containing the common electrode. Furthermore, the distance between the bottom of the deep etch trench and the surface of the first substrate furthest from the common electrode is greater than or equal to 1 μm in a direction perpendicular to the plane containing the common electrode.

[0014] On the other hand, a method for fabricating a laser is provided, the laser including an active region of a first optical resonant cavity, an active region of a second optical resonant cavity, and a passive region of a second optical resonant cavity. The fabrication method includes: sequentially stacking a first core region, a quantum well layer, a second core region, and a second substrate on a first substrate, wherein the first core region is located in the active regions of the first and second optical resonant cavities, the quantum well layer is located in the active regions of the first and second optical resonant cavities, and the second core region is located in the active regions of the first and second optical resonant cavities.

[0015] A quantum well disordered layer is formed, which is located between the first substrate and the second substrate, and is located in the passive region of the second optical resonator.

[0016] A first optical resonant cavity injection electrode, a second optical resonant cavity injection electrode, and a second optical resonant cavity phase-tuning electrode are formed. The first optical resonant cavity injection electrode is disposed on the side of the second substrate away from the first substrate and is located in the active region of the first optical resonant cavity. The second optical resonant cavity injection electrode is disposed on the side of the second substrate away from the first substrate and is located in the active region of the second optical resonant cavity. The second optical resonant cavity phase-tuning electrode is disposed on the side of the second substrate away from the first substrate and is located in the passive region of the second optical resonant cavity.

[0017] A common electrode is formed, which is located on the side of the first substrate away from the second substrate.

[0018] In the above embodiments of this application, the laser includes three regions: an active region of a first optical resonant cavity, an active region of a second optical resonant cavity, and a passive region of a second optical resonant cavity. A first core region, a quantum well layer, a second core region, and a second substrate are sequentially stacked on a first substrate. The first core region, the quantum well layer, and the second core region are all located within the active regions of the first and second optical resonant cavities. A quantum well disordering layer is formed in the passive region of the second optical resonant cavity. Therefore, the active region of the first optical resonant cavity is an active structure, and the second optical resonant cavity includes both an active region and a passive region.

[0019] Then, a first optical resonant cavity injection electrode is formed in the active region of the first optical resonant cavity, a second optical resonant cavity injection electrode is formed in the active region of the second optical resonant cavity, a second optical resonant cavity phase modulation electrode is formed in the passive region of the second optical resonant cavity, and a common electrode is formed on the side of the first substrate away from the second substrate.

[0020] In this design, the first optical resonator injection electrode is a single electrode that controls the laser current (equivalent to controlling the injection current density). The second optical resonator has one electrode each in its active and passive regions (the second optical resonator injection electrode and the second optical resonator phase-tuning electrode) to control the injection current density in each region respectively. By jointly adjusting the injection current of the three electrodes (the first optical resonator injection electrode, the second optical resonator injection electrode, and the second optical resonator phase-tuning electrode), dual-cavity coupling is achieved, simultaneously meeting the requirements for narrow linewidth (<1MHz) and fine wavelength tuning.

[0021] In some embodiments, the first core region is also located in the passive region of the second optical resonant cavity, the quantum well layer is also located in the passive region of the second optical resonant cavity, and the second core region is also located in the passive region of the second optical resonant cavity. The formation of the quantum well disordering layer includes: forming a vacancy promoting layer on the side of the second substrate away from the first substrate, and the vacancy promoting layer is located in the passive region of the second optical resonant cavity.

[0022] The first substrate, the first core region, the quantum well layer, the second core region, the second substrate, and the vacancy promotion layer are rapidly annealed so that the first core region, the quantum well layer, and the portion of the second core region in the passive region of the second optical resonator jointly form the quantum well disordered layer.

[0023] In some embodiments, along a first direction, the active region of the first optical resonant cavity, the active region of the second optical resonant cavity, and the passive region of the second optical resonant cavity are sequentially connected, and the first direction is parallel to the plane where the first substrate is located.

[0024] After forming the quantum well disordered layer, the fabrication method further includes: forming a deep etch groove, the deep etch groove being located at the connection between the active region of the first optical resonant cavity and the active region of the second optical resonant cavity; and the deep etch groove penetrating the second substrate, the second core region, the quantum well disordered layer and the first core region, and extending into the first substrate.

[0025] In some embodiments, along the first direction, the first optical resonant cavity includes opposing first and second partial reflective surfaces, and the second optical resonant cavity includes opposing first and second partial reflective surfaces.

[0026] The deep etched groove includes two opposing sides in the first direction, wherein the side closest to the active region of the first optical resonant cavity is the second part of the reflecting surface of the first optical resonant cavity.

[0027] The side closest to the active region of the second optical resonant cavity is the second part of the reflecting surface of the second optical resonant cavity.

[0028] In some embodiments, forming the first optical resonant cavity injection electrode, the second optical resonant cavity injection electrode, and the second optical resonant cavity phase-tuning electrode includes: A mask layer is formed on the side of the second substrate away from the first substrate. The mask layer includes a first opening, a second opening, and a third opening. The first opening is located in the active region of the first optical resonant cavity, the second opening is located in the active region of the second optical resonant cavity, and the third opening is located in the passive region of the second optical resonant cavity.

[0029] The first optical resonant cavity injection electrode is formed in the first opening, the second optical resonant cavity injection electrode is formed in the second opening, and the second optical resonant cavity phase-tuning electrode is formed in the third opening. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in this application, the accompanying drawings used in some embodiments of this application will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual flow of the method, the actual timing of the signals, etc. involved in the embodiments of this application.

[0031] Figure 1 A schematic diagram of a narrow-linewidth semiconductor laser based on a coupled cavity, provided for an embodiment of this application; Figures 2A-2E Schematic diagrams illustrating the fabrication steps of a narrow-linewidth semiconductor laser based on a coupled cavity, as provided in the embodiments of this application. Figure 3 A graph showing the relationship between the width of the deep etched groove and the reflectivity and transmittance provided for embodiments of this application; Figure 4 A diagram showing the relationship between the width of the deep etch groove and the transmission phase provided in the embodiments of this application; Figure 5 A graph showing the relationship between the primary mode and the second-highest order mode thresholds of a narrow-linewidth semiconductor laser based on a coupled cavity, provided for embodiments of this application. Detailed Implementation

[0032] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0033] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and the number of objects is not limited; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0034] In the description of this application, "multiple" means two or more.

[0035] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0036] Embodiments of this application provide a short-wavelength, narrow-linewidth semiconductor laser based on a coupled cavity, see [link to relevant documentation]. Figure 1 The laser 1 includes three regions: an active region 2 of a first optical resonant cavity, an active region 3 of a second optical resonant cavity, and a passive region 4 of a second optical resonant cavity. Furthermore, the laser 1 includes a common electrode 5, a first substrate 6, a first core region 7, a quantum well layer 8, a second core region 9, a quantum well disordering layer 10, a second substrate 11, a deep etched groove 12, a first partial reflecting surface 13 of the first optical resonant cavity, a second partial reflecting surface 14 of the first optical resonant cavity, a first partial reflecting surface 15 of the second optical resonant cavity, a second partial reflecting surface 16 of the second optical resonant cavity, an injection electrode 17 of the first optical resonant cavity, an injection electrode 18 of the second optical resonant cavity, and a phase-tuning electrode 19 of the second optical resonant cavity.

[0037] The common electrode 5 is shared by three regions: the active region 2 of the first optical resonant cavity, the active region 3 of the second optical resonant cavity, and the passive region 4 of the second optical resonant cavity. A first substrate 6 is disposed on the common electrode 5 and includes a lower cladding layer and an auxiliary layer. A first core region 7 is disposed on the side of the first substrate 6 away from the common electrode 5, and is located in the active regions 2 and 3 of the first and second optical resonant cavities. A quantum well layer 8 is disposed on the side of the first core region 6 away from the common electrode 5, and is located in the active regions 2 and 3 of the first and second optical resonant cavities. A second core region 9 is disposed on the side of the quantum well layer 8 away from the common electrode 5, and is located in the active regions 2 and 3 of the first and second optical resonant cavities. A quantum well disordering layer 10 is disposed on the side of the first substrate 6 away from the common electrode 5, and is located in the passive region 4 of the second optical resonant cavity. The second substrate 11 is disposed on the side of the second core region 9 away from the common electrode 5, and the second substrate 11 is disposed on the side of the quantum well disordered layer 10 away from the common electrode 5. The second substrate 11 includes an upper cladding layer and an auxiliary layer. The first substrate 6, the first core region 7, the quantum well layer 8, the second core region 9, the quantum well disordered layer 10, and the second substrate 11 are stacked together to form a ridge waveguide.

[0038] The first optical resonant cavity injection electrode 17 is disposed on the side of the second substrate 11 away from the common electrode 5, and the first optical resonant cavity injection electrode 17 is located in the active region 2 of the first optical resonant cavity. The second optical resonant cavity injection electrode 18 is disposed on the side of the second substrate 11 away from the common electrode 5, and the second optical resonant cavity injection electrode 18 is located in the active region 3 of the second optical resonant cavity. The second optical resonant cavity phase modulation electrode 19 is disposed on the side of the second substrate 11 away from the common electrode 5, and the second optical resonant cavity phase modulation electrode 19 is located in the passive region 4 of the second optical resonant cavity.

[0039] In the above embodiments of this application, the laser 1 includes two optical resonant cavities, namely a first optical resonant cavity and a second optical resonant cavity, and the two optical resonant cavities use ridge waveguides for lateral mode confinement. The structure has no gratings, coupling alignment, or other relatively high-loss structures, which is beneficial for the high-power (>50mW) operation of the laser and can further narrow the linewidth.

[0040] The entire first optical resonator is an active structure (region 2 of the first optical resonator). The injection electrode 17 of the first optical resonator is a single electrode that controls the laser current (equivalent to controlling the injection current density). The second optical resonator includes an active region and a passive region (regions 3 of the second optical resonator and 4 of the second optical resonator). The passive region is achieved by using rapid thermal annealing and selective surface coating of silicon dioxide film to induce quantum well disordering, thereby forming a quantum well disordered layer 10 in the passive region. Each of the active and passive regions has an electrode (the injection electrode 18 of the second optical resonator and the phase-tuning electrode 19 of the second optical resonator) to control the injection current density in the two regions respectively.

[0041] By jointly adjusting the injection current of the three electrodes (first optical resonant cavity injection electrode 17, second optical resonant cavity injection electrode 18, and second optical resonant cavity phase-tuning electrode 19), the coupling of the two resonant cavities can be achieved, which can simultaneously meet the requirements of narrow linewidth (<1MHz) and fine wavelength tuning.

[0042] In some embodiments, see Figure 1 Along the first direction X (the first direction X is parallel to the plane where the common electrode 5 is located), the active region 2 of the first optical resonator, the active region 3 of the second optical resonator, and the passive region 4 of the second optical resonator are connected in sequence.

[0043] The laser 1 also includes a deep etching groove 12, which is located at the junction P of the active region 2 of the first optical resonant cavity and the active region 3 of the second optical resonant cavity. Furthermore, the deep etching groove 12 penetrates the second substrate 11, the second core region 9, the quantum well layer 8 and the first core region 7, and extends into the first substrate 6.

[0044] The deep etched groove 12 penetrates the second substrate 11, the second core region 9, the quantum well layer 8 and the first core region 7, and extends into the first substrate 6, so that the deep etched groove 12 divides the ridge waveguide into two optical resonant cavities, thereby enabling the coupling of the two resonant cavities.

[0045] In some embodiments, see Figure 1 Along the first direction X, the first optical resonant cavity includes a first partial reflecting surface 13 and a second partial reflecting surface 14, and the second optical resonant cavity includes a first partial reflecting surface 15 and a second partial reflecting surface 16, which are opposite to each other.

[0046] The deep etched groove 12 includes two opposite sides in the first direction X. The side closer to the active region 2 of the first optical resonant cavity is the second part of the reflecting surface 14 of the first optical resonant cavity. The side closer to the active region 3 of the second optical resonant cavity is the second part of the reflecting surface 16 of the second optical resonant cavity.

[0047] In the above embodiments of this application, the first part of the reflecting surface 13 of the first optical resonant cavity is a reflecting surface formed by cleaving along the crystal direction of the wafer, and the second part of the reflecting surface 14 of the first optical resonant cavity is a sidewall of a deep etch groove. Similarly, the first part of the reflecting surface 13 of the second optical resonant cavity is a reflecting surface formed by cleaving along the crystal direction of the wafer, and the second part of the reflecting surface 14 of the second optical resonant cavity is a sidewall of a deep etch groove 12.

[0048] The input end face of laser 1 is the first part of the reflective surface 15 of the second optical resonant cavity. Along the first direction X, the second part of the reflective surface 16 of the second optical resonant cavity and the second part of the reflective surface 14 of the first optical resonant cavity are coupled and connected through a deep etched groove 12. The output end face is the first part of the reflective surface 13 of the first optical resonant cavity.

[0049] In some embodiments, see Figure 1 Along the first direction X, the width of the deep etching groove 12 is a half-integer multiple of the laser's operating wavelength.

[0050] The propagation mode of light in the deep etched groove 12 was calculated by simulation. The results are shown in [link to simulation]. Figure 3 , Figure 4 , Figure 5 See also Figure 3 When the width of the deep etching groove 12 is approximately an integer multiple of half the operating wavelength of the laser, the resonance within the groove is enhanced, and the transmission value is maximized. (See also...) Figure 4 When the width of the deep etched groove 12 is approximately an integer multiple of half the operating wavelength of the laser, the transmission phase approaches 0. (See also...) Figure 5 When the width of the deep etching groove 12 is approximately an integer multiple of half the working wavelength of the laser, the mode selectivity is stronger.

[0051] In some embodiments, see Figure 1 Along the first direction X, the length of the first optical resonant cavity is different from that of the second optical resonant cavity. The two optical resonant cavities and the resonant cavity formed by the two first partial reflective surfaces (13 and 15) (referred to as the main optical resonant cavity) work together to ensure single-mode operation.

[0052] In some embodiments, see Figure 1 Along the second direction Z (the second direction Z is perpendicular to the plane where the common electrode 5 is located), the depth of the deep etching groove 12 is greater than or equal to 3 μm. For example, the depth of the deep etching groove 12 is 3 μm, 4 μm, 5 μm, 6 μm, or 7 μm. Furthermore, along the second direction Z, the distance between the bottom of the deep etching groove 12 and the surface of the first substrate 6 away from the common electrode 5 is greater than or equal to 1 μm. For example, the distance between the bottom of the deep etching groove 12 and the surface of the first substrate 6 away from the common electrode 5 is 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm.

[0053] In the above embodiments of this application, setting the depth of the deep etching groove 12 within the above-mentioned suitable range can reduce scattering loss, facilitate low threshold operation of the laser, make it easier to control coupling, and enhance mode selection capability.

[0054] Embodiments of this application also provide a method for fabricating a laser, see [link to relevant documentation]. Figures 2A-2E The preparation method includes the following steps S1~S4: Step S1: See Figure 2A A first core region 7, a quantum well layer 8, a second core region 9, and a second substrate 11 are sequentially stacked on a first substrate 6. The first core region 7 is located in the active region 2 of the first optical resonant cavity and the active region 3 of the second optical resonant cavity. The quantum well layer 8 is located in the active region 2 of the first optical resonant cavity and the active region 3 of the second optical resonant cavity. The second core region 9 is located in the active region 2 of the first optical resonant cavity and the active region 3 of the second optical resonant cavity. Exemplarily, the first core region 7, the quantum well layer 8, and the second core region 9 are also located in the passive region 4 of the second optical resonant cavity.

[0055] Step S2: See Figure 2B A quantum well disordered layer 10 is formed, which is located between the first substrate 6 and the second substrate 9, and is located in the passive region 4 of the second optical resonator.

[0056] For example, step S2 above includes the following steps S21 to S22: Step S21: See Figure 2A The first core region 7, the quantum well layer 8, and the second core region 9 are also located in the passive region 4 of the second optical resonator, see [link / reference]. Figure 2B A vacancy promotion layer a is formed on the side of the second substrate 11 away from the first substrate 6, and the vacancy promotion layer a is located in the passive region 4 of the second optical resonator.

[0057] For example, the material of the vacancy promotion layer a may include silicon dioxide. A thin film deposition process may be used to deposit a silicon dioxide film layer over the entire surface. Then, a photolithography process may be used to pattern the silicon dioxide film layer, retaining a portion of the silicon dioxide film layer in the passive region 4 of the second optical resonant cavity as the vacancy promotion layer a.

[0058] Step S22: See Figure 2B The first substrate 6, the first core region 7, the quantum well layer 8, the second core region 9, the second substrate 11, and the vacancy promotion layer a are rapidly annealed so that the first core region 7, the quantum well layer 8, and the second core region 9 together form the quantum well disorder layer 10 in a portion of the passive region 4 of the second optical resonator.

[0059] A quantum well disorder layer 10 is formed by inducing quantum well disorder through rapid thermal annealing (RTA) and selective deposition of a silicon dioxide thin film, thereby creating a passive region 4 for the second optical resonator. The phase of this passive region 4 is adjustable. This technique allows for the fabrication of a phase-adjustable passive region on an active epitaxial wafer without secondary epitaxy, and with minimal impact on the performance of the active region. The fabrication process is simple, requires no secondary epitaxy, and has low manufacturing costs, making it suitable for mass production.

[0060] For example, see Figure 2C Along the first direction X, the active region 2 of the first optical resonator, the active region 3 of the second optical resonator, and the passive region 4 of the second optical resonator are sequentially connected. Following step S2, the fabrication method further includes step S23: Step S23: See Figure 2C A deep etch groove 12 is formed. The deep etch groove 12 is located at the junction P of the active region 2 of the first optical resonant cavity and the active region 3 of the second optical resonant cavity. Furthermore, the deep etch groove 12 penetrates the second substrate 11, the second core region 9, the quantum well disordered layer 8 and the first core region 7, and extends into the first substrate 6.

[0061] For example, an inductively coupled plasma (ICP) process is used to form a deep etching trench 12, the mask pattern of which is processed onto silicon nitride via a Cr lift-off process using contact exposure. Contact exposure reduces processing time and lowers process costs. Both pattern transfer steps improve the etching selectivity, ensuring that deep etching on group III-V materials can be completed.

[0062] Step S3: See Figure 2D This forms a first optical resonant cavity injection electrode 17, a second optical resonant cavity injection electrode 18, and a second optical resonant cavity phase-tuning electrode 19. The first optical resonant cavity injection electrode 17 is disposed on the side of the second substrate 11 away from the first substrate 6 and is located in the active region 2 of the first optical resonant cavity. The second optical resonant cavity injection electrode 18 is disposed on the side of the second substrate 11 away from the first substrate 6 and is located in the active region 3 of the second optical resonant cavity. The second optical resonant cavity phase-tuning electrode 19 is disposed on the side of the second substrate 11 away from the first substrate 6 and is located in the passive region 4 of the second optical resonant cavity.

[0063] For example, step S3 above includes the following steps S31 to S32: Step S31: A mask layer is formed on the side of the second substrate 11 away from the first substrate 6. The mask layer includes a first opening, a second opening, and a third opening. The first opening is located in the active region 2 of the first optical resonant cavity, the second opening is located in the active region 3 of the second optical resonant cavity, and the third opening is located in the passive region 4 of the second optical resonant cavity.

[0064] Step S32: A first optical resonant cavity injection electrode 17 is formed in the first opening, a second optical resonant cavity injection electrode 18 is formed in the second opening, and a second optical resonant cavity phase modulation electrode 19 is formed in the third opening.

[0065] By jointly adjusting the injection current of the three electrodes, the single-mode narrow linewidth characteristics and operating wavelength of the laser are controlled, resulting in a large wavelength tunable range and enabling precise alignment of the laser wavelength with atomic spectral lines.

[0066] Step S4: See Figure 2E A common electrode 5 is formed, which is located on the side of the first substrate 6 away from the second substrate 11.

[0067] In the above embodiments of this application, the laser 1 includes three regions: an active region 2 of a first optical resonant cavity, an active region 3 of a second optical resonant cavity, and a passive region 4 of a second optical resonant cavity. A first core region 7, a quantum well layer 8, a second core region 9, and a second substrate 11 are sequentially stacked on a first substrate 6. The first core region 7, the quantum well layer 8, and the second core region 9 are all located in the active regions 2 and 3 of the first and second optical resonant cavities, respectively. A quantum well disordering layer 10 is formed in the passive region 4 of the second optical resonant cavity. Therefore, the active region 2 of the first optical resonant cavity is an active structure, and the second optical resonant cavity includes both active and passive regions.

[0068] Then, a first optical resonant cavity injection electrode 17 is formed in the active region 2 of the first optical resonant cavity, a second optical resonant cavity injection electrode 18 is formed in the active region 3 of the second optical resonant cavity, a second optical resonant cavity phase modulation electrode 19 is formed in the passive region 4 of the second optical resonant cavity, and a common electrode 5 is formed on the side of the first substrate 6 away from the second substrate 11.

[0069] The first optical resonator injection electrode 17 is a single electrode that controls the laser current (equivalent to controlling the injection current density). The second optical resonator has one electrode each in its active and passive regions (the second optical resonator injection electrode 18 and the second optical resonator phase-tuning electrode 19) to control the injection current density in each region. By jointly adjusting the injection current of the three electrodes (the first optical resonator injection electrode 17, the second optical resonator injection electrode 18, and the second optical resonator phase-tuning electrode 19), dual-cavity coupling is achieved, simultaneously meeting the requirements for narrow linewidth (<1MHz) and fine wavelength tuning.

[0070] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A short-wavelength, narrow-linewidth semiconductor laser based on a coupled cavity, characterized in that, It includes the active region of the first optical resonator, the active region of the second optical resonator, and the passive region of the second optical resonator; The laser includes: Common electrode; A first substrate is disposed on the common electrode; The first core region is disposed on the side of the first substrate away from the common electrode, and is located in the active region of the first optical resonant cavity and the active region of the second optical resonant cavity. A quantum well layer is disposed on the side of the first core region away from the common electrode, and is located in the active region of the first optical resonant cavity and the active region of the second optical resonant cavity; The second core region is located on the side of the quantum well layer away from the common electrode, and is situated in the active region of the first optical resonant cavity and the active region of the second optical resonant cavity. A quantum well disordering layer is disposed on the side of the first substrate away from the common electrode and located in the passive region of the second optical resonant cavity; The second substrate is disposed on the side of the second core region away from the common electrode, and on the side of the quantum well disordered layer away from the common electrode; The first optical resonant cavity injection electrode is disposed on the side of the second substrate away from the common electrode and is located in the active region of the first optical resonant cavity; The second optical resonant cavity injection electrode is disposed on the side of the second substrate away from the common electrode and is located in the active region of the second optical resonant cavity; The second optical resonant cavity phase-tuning electrode is disposed on the side of the second substrate away from the common electrode and located in the passive region of the second optical resonant cavity.

2. The laser according to claim 1, characterized in that, Along the first direction, the active region of the first optical resonant cavity, the active region of the second optical resonant cavity, and the passive region of the second optical resonant cavity are connected in sequence, and the first direction is parallel to the plane where the common electrode is located. The laser also includes a deep etching groove, which is located at the connection between the active region of the first optical resonant cavity and the active region of the second optical resonant cavity. Furthermore, the deep etched trench penetrates the second substrate, the second core region, the quantum well disordered layer, and the first core region, and extends into the first substrate.

3. The laser according to claim 2, characterized in that, Along the first direction, the first optical resonant cavity includes opposing first and second reflective surfaces, and the second optical resonant cavity includes opposing first and second reflective surfaces. The deep etching groove includes two opposite sides in the first direction, and the side closest to the active region of the first optical resonant cavity is the second part of the reflecting surface of the first optical resonant cavity. The side closest to the active region of the second optical resonant cavity is the second part of the reflecting surface of the second optical resonant cavity.

4. The laser according to claim 2 or 3, characterized in that, Along the first direction, the width of the deep etched groove is a half-integer multiple of the operating wavelength of the laser.

5. The laser according to claim 2 or 3, characterized in that, Along the first direction, the length of the first optical resonant cavity is different from the length of the second optical resonant cavity.

6. The laser according to claim 2 or 3, characterized in that, Along a direction perpendicular to the plane where the common electrode is located, the depth of the deep etched groove is greater than or equal to 3 μm; Furthermore, along a direction perpendicular to the plane where the common electrode is located, the distance between the bottom of the deep etched groove and the surface of the first substrate away from the common electrode is greater than or equal to 1 μm.

7. A method for fabricating a laser, characterized in that, The laser includes an active region of a first optical resonant cavity, an active region of a second optical resonant cavity, and a passive region of a second optical resonant cavity. The preparation method includes: A first core region, a quantum well layer, a second core region, and a second substrate are sequentially stacked on a first substrate. The first core region is located in the active region of the first optical resonant cavity and the active region of the second optical resonant cavity. The quantum well layer is located in the active region of the first optical resonant cavity and the active region of the second optical resonant cavity. The second core region is located in the active region of the first optical resonant cavity and the active region of the second optical resonant cavity. A quantum well disordered layer is formed, wherein the quantum well disordered layer is located between the first substrate and the second substrate, and the quantum well disordered layer is located in the passive region of the second optical resonator. A first optical resonant cavity injection electrode, a second optical resonant cavity injection electrode, and a second optical resonant cavity phase-tuning electrode are formed. The first optical resonant cavity injection electrode is disposed on the side of the second substrate away from the first substrate and is located in the active region of the first optical resonant cavity. The second optical resonant cavity injection electrode is disposed on the side of the second substrate away from the first substrate and is located in the active region of the second optical resonant cavity. The second optical resonant cavity phase-tuning electrode is disposed on the side of the second substrate away from the first substrate and is located in the passive region of the second optical resonant cavity. A common electrode is formed, which is located on the side of the first substrate away from the second substrate.

8. The preparation method according to claim 7, characterized in that, The first core region is also located in the passive region of the second optical resonant cavity, the quantum well layer is also located in the passive region of the second optical resonant cavity, and the second core region is also located in the passive region of the second optical resonant cavity. The formation of the quantum well disordered layer includes: A vacancy promoting layer is formed on the side of the second substrate away from the first substrate, and the vacancy promoting layer is located in the passive region of the second optical resonant cavity; The first substrate, the first core region, the quantum well layer, the second core region, the second substrate, and the vacancy promotion layer are rapidly annealed so that the first core region, the quantum well layer, and the portion of the second core region in the passive region of the second optical resonator jointly form the quantum well disordered layer.

9. The preparation method according to claim 7, characterized in that, Along a first direction, the active region of the first optical resonant cavity, the active region of the second optical resonant cavity, and the passive region of the second optical resonant cavity are connected in sequence, and the first direction is parallel to the plane of the first substrate. After forming the quantum well disordered layer, the fabrication method further includes: A deep etching groove is formed, which is located at the connection between the active region of the first optical resonant cavity and the active region of the second optical resonant cavity; Furthermore, the deep etched trench penetrates the second substrate, the second core region, the quantum well disordered layer, and the first core region, and extends into the first substrate.

10. The preparation method according to claim 7, characterized in that, The formation of the first optical resonant cavity injection electrode, the second optical resonant cavity injection electrode, and the second optical resonant cavity phase-tuning electrode includes: A mask layer is formed on the side of the second substrate away from the first substrate. The mask layer includes a first opening, a second opening, and a third opening. The first opening is located in the active region of the first optical resonant cavity, the second opening is located in the active region of the second optical resonant cavity, and the third opening is located in the passive region of the second optical resonant cavity. The first optical resonant cavity injection electrode is formed in the first opening, the second optical resonant cavity injection electrode is formed in the second opening, and the second optical resonant cavity phase-tuning electrode is formed in the third opening.

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