Laser based on bimetallic Bragg grating and top surface HR reflecting film

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a laser based on a bimetallic Bragg grating and a top surface HR reflecting film, which comprises a gain chip, a first high-reflection HR film is plated on the left end surface of the gain chip, and a first anti-reflection AR film is plated on the right end surface of the gain chip. A metal Bragg grating waveguide is arranged on the right side of the gain chip, the right end face of the gain chip and the left end face of the metal Bragg grating waveguide are aligned and attached to form an outer cavity structure, and the left end face of the metal Bragg grating waveguide is plated with a second anti-reflection AR film. The right end face of the metal Bragg grating waveguide is plated with a third anti-reflection AR film. Performance test is carried out on the laser provided by the invention, and test results show that the line width is 0.6 kHz, the SMSR is 63dB, and the threshold current is 22mA, thereby verifying the effectiveness of the laser provided by the invention.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, specifically a laser based on a dual-metal Bragg grating and a top HR reflective film. Background Art

[0002] At present, with the rapid development of optoelectronic technology, extremely stringent requirements are imposed on the performance of lasers in fields such as quantum key distribution, coherent optical communication, high-precision spectral analysis, and photonic integrated chips. At the same time, cost control has also become a key factor. However, traditional distributed feedback (DFB) lasers and conventional external cavity lasers have many problems in practical applications: 1. Traditional external cavity lasers mostly adopt a single grating structure, with a side mode suppression ratio (SMSR) of only 45 - 50 dB and a linewidth of about 20 - 50 kHz (IEEE Photonics Technology Letters, 2020), which cannot meet the strict requirements for light sources in high-precision applications. It is difficult to balance beam quality and integration, relying on complex optical alignment processes, increasing production difficulty and cost, and being unfavorable for large-scale integrated manufacturing. In addition, traditional external cavity lasers cannot effectively solve the problem of upward diffracted light energy loss caused by the grating structure, affecting the light guiding performance of the grating optical waveguide.

[0003] 2. Affected by carrier density fluctuations and a typical lasing cavity length of 0.5 mm, the linewidth of DFB lasers is usually 1 - 10 MHz (Optics Express, 2021). In application scenarios such as coherent detection, a wider linewidth will cause serious signal interference, greatly reducing detection accuracy and system performance. Its secondary epitaxial process is complex, with a yield of only 65 - 70% (Photonics Research, 2021), and the manufacturing cost is 2 - 3 times higher than that of external cavity lasers. The reflectivity of the semiconductor grating is only 93 - 95%, and additional gain compensation is required, resulting in a 15 - 20% increase in power consumption and also causing heat dissipation problems, affecting the stability and reliability of the laser. Summary of the Invention

[0004] The present invention provides a laser based on a dual-metal Bragg grating and a top HR reflective film to solve the problems raised in the above background art.

[0005] To achieve the above object, the present invention provides the following technical solution. A laser based on a dual-metal Bragg grating and a top HR reflective film includes: a gain chip, with a first high-reflection HR film plated on the left end face of the gain chip and a first anti-reflection AR film plated on the right end face of the gain chip.

[0006] A metal Bragg grating waveguide is provided on the right side of the gain chip. The right end face of the gain chip is aligned and bonded to the left end face of the metal Bragg grating waveguide to form an external cavity structure. A second antireflection AR film is deposited on the left end face of the metal Bragg grating waveguide, and a third antireflection AR film is deposited on the right end face of the metal Bragg grating waveguide.

[0007] The metal Bragg grating waveguide includes a grating waveguide substrate. A ridge optical waveguide is provided on the upper end face of the grating waveguide substrate. A first planar metal Bragg grating is provided on the left side of the upper end face of the ridge optical waveguide, and a second planar metal Bragg grating is provided on the right side of the upper end face of the ridge optical waveguide. A phase difference is provided between the first planar metal Bragg grating and the second planar metal Bragg grating. A second high reflection HR film is provided on the tops of the first planar metal Bragg grating and the second planar metal Bragg grating.

[0008] For the second high reflection HR film, its preparation process is specifically as follows: It is deposited on the tops of the first planar metal Bragg grating and the second planar metal Bragg grating by magnetron sputtering. The material of the second high reflection HR film is selected as a TiO2 / SiO2 multi-layer dielectric composite material, with each layer having a thickness of λ / 4, a thickness accuracy of ±5 nm, a reflectivity R3 > 99.5%, and a surface roughness less than 0.08 nm RMS.

[0009] As a preference of the above technical solution, the gain chip adopts an InP / InGaAsP quantum well structure, with the central emission wavelength λ in the range of 1530 - 1610 nm. At an ambient temperature of 25 °C, the threshold current is lower than 22 mA.

[0010] Further, the gain chip adopts an InP / InGaAsP quantum well structure, with the central emission wavelength λ being 1550 nm. At an ambient temperature of 25 °C, the threshold current is lower than 22 mA.

[0011] As a preference of the above technical solution, the thickness of the first antireflection AR film is λ / 4, and the reflectivity R1 < 0.03%; the first high reflection HR film is a SiO2 / TiO2 multi-layer high reflection film, and the reflectivity R2 > 99.9%.

[0012] As a preference of the above technical solution, the length of the planar metal Bragg grating waveguide is 1 - 3 cm, the grating period is 225 ± 0.3 nm, the duty cycle is 50 ± 1%, and the thickness of the Cr / Au layer is 200 ± 5 nm.

[0013] Further, the length of the planar metal Bragg grating waveguide is 2 cm, the grating period is 225 ± 0.3 nm, and the duty cycle is 50 ± 1%.

[0014] As an optimization of the above technical solution, the ridge optical waveguide has a width of 3-5 μm and a height of 2-4 μm, and the mode field matching degree with the gain chip is >98%.

[0015] Furthermore, the ridge optical waveguide has a width of 4 μm and a height of 3 μm, and the mode field matching degree with the gain chip is >98%.

[0016] As an optimization of the above technical solution, the first planar metal Bragg grating and the second planar metal Bragg grating are of Cr / Au structure, with a thickness of 50 nm / 150 nm, a reflectivity of >99.9%, and a 3 dB reflection bandwidth of <0.1 nm.

[0017] As an optimization of the above technical solution, the phase difference Δφ = π, and the phase control accuracy is <λ / 50 through atomic layer deposition technology.

[0018] The present invention provides a laser based on a dual-metal Bragg grating and a top HR reflection film, having the following beneficial effects: 1. The second high-reflection HR film prevents light energy loss: A second high-reflection HR film is provided on the tops of the first planar metal Bragg grating and the second planar metal Bragg grating, and its reflectivity is greater than 99.5%. This reflection film works based on the multi-layer thin film interference effect and can efficiently reflect the light diffracted upward back into the waveguide. When light propagates in the waveguide and encounters the top Bragg grating, part of the light will be diffracted upward, and the presence of the second high-reflection HR film effectively reduces this part of the light energy loss. By optimizing the reflection characteristics of the grating, the reflection efficiency of the grating is further enhanced, the light field is constrained to propagate inside the waveguide, and the light energy is prevented from spilling into free space, thereby maintaining the light guiding property of the metal Bragg grating waveguide and significantly improving the performance of the laser.

[0019] 2. Cost reduction advantage: The second high-reflection HR film replaces the traditional thick semiconductor secondary epitaxial waveguide layer, fundamentally reducing the material cost and process complexity. At the same time, the present invention uses an electroplating process to prepare the first planar metal Bragg grating and the second planar metal Bragg grating. Compared with the traditional semiconductor etching process, the planar metal grating is flat and regular, providing a high-quality filtering and reflection effect. This process does not require multiple processes such as semiconductor crystal grating etching with complex crystal plane structures, crystal plane orientation restrictions, high precision, and crystal plane flatness, avoiding the dependence on high-precision equipment and special chemical reagents, effectively reducing the equipment cost, raw material cost, and process complexity, significantly reducing the production cost, and having good economic feasibility.

[0020] 3. Dual-grating collaborative enhancement mechanism: The first planar metal Bragg grating and the second planar metal Bragg grating with a phase difference Δφ = π are adopted. The reflected lights of the two gratings interfere constructively in the cavity, increasing the main peak reflectivity from 95% of the traditional single grating to 99.9%, enhancing the light field intensity in the cavity, and providing guarantee for high-power and stable laser output. The destructive interference characteristics of the dual gratings are used to suppress the non-lasing modes. According to the formula:

[0021] where R1 and R2 are the reflectivities at both ends of the resonant cavity; Theoretically, the side mode suppression ratio (SMSR) can reach 63 dB, effectively weakening the side mode intensity, improving the purity and stability of the output light, and meeting the requirements of high-precision applications.

[0022] The setting of the dual gratings doubles the equivalent cavity length, expanding the free spectral range from 50 GHz of the traditional external cavity to 100 GHz, reducing mode competition, improving the wavelength selection ability and stability of the laser, and facilitating the realization of laser output with different wavelengths in multi-wavelength application scenarios.

[0023] 4. Linewidth compression technology: Based on the Hakki-Paoli model, the linewidth formula is modified as:

[0024] where hν: photon energy; P: laser output power; L: total length of the resonant cavity; L g : gain medium length; R1 and R2 are the reflectivities at both ends of the resonant cavity; α: linewidth enhancement factor.

[0025] : comprehensively considers the influence of the cavity length and the gain medium on the photon lifetime.

[0026] : corrects the loss term in the traditional linewidth formula, including the coupling effect of phase noise and carrier fluctuations.

[0027] By adopting the first planar metal Bragg grating and the second planar metal Bragg grating with an external cavity length of 3 cm and a reflectivity of 99.92%, an ultra-narrow linewidth output with a linewidth Δν = 0.6 kHz is achieved, while the linewidth of the traditional DFB laser is about 1 MHz. The ultra-narrow linewidth laser has important application values in the fields of coherent optical communication, high-precision spectral analysis, and quantum key distribution. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic structural diagram of the present invention; Figure 2 is Figure 1 the top view of; Figure 3Schematic diagram of the structure of the metal Bragg grating waveguide in the present invention; Figure 4 is Figure 3 left view of.

[0029] In the figure: 1, gain chip; 11, first high reflection HR film; 12, first antireflection AR film; 2, metal Bragg grating waveguide; 21, grating waveguide substrate; 22, ridge optical waveguide; 23, first planar metal Bragg grating; 24, second planar metal Bragg grating; 25, second antireflection AR film; 26, third antireflection AR film; 27, phase difference; 28, second high reflection HR film. Specific implementation manner

[0030] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention.

[0031] Embodiment 1 As Figures 1 - 4 shown, in this embodiment, a laser based on a double metal Bragg grating and a top HR reflection film includes: a gain chip 1, a first high reflection HR film 11 is plated on the left end face of the gain chip 1, and a first antireflection AR film 12 is plated on the right end face of the gain chip 1.

[0032] In specific implementation, the gain chip 1 adopts an InP / InGaAsP quantum well structure, the central emission wavelength λ is 1530 nm, and at an ambient temperature of 25 °C, the threshold current is lower than 22 mA, showing good optoelectronic conversion performance. The thickness of the first antireflection AR film 12 is λ / 4, and the reflectivity R1 < 0.03% to reduce light reflection loss; the first high reflection HR film 11 is a SiO2 / TiO2 multi-layer high reflection film, and the reflectivity R2 > 99.9% to enhance optical feedback.

[0033] A metal Bragg grating waveguide 2 is provided on the right side of the gain chip 1. The right end face of the gain chip 1 is aligned and attached to the left end face of the metal Bragg grating waveguide 2 to form an external cavity structure. A second antireflection AR film 25 is plated on the left end face of the metal Bragg grating waveguide 2, and a third antireflection AR film 26 is plated on the right end face of the metal Bragg grating waveguide 2.

[0034] In specific implementation, the length of the planar metal Bragg grating waveguide 2 is 1 cm, the grating period is 225 ± 0.3 nm, the duty cycle is 50 ± 1%, and the thickness of the Cr / Au layer is 200 ± 5 nm (50 nm Cr / 150 nm Au) to form a grating structure with a high reflectivity.

[0035] The metal Bragg grating waveguide 2 includes a grating waveguide substrate 21. On the upper end face of the grating waveguide substrate 21, there is a ridge optical waveguide 22. On the left side of the upper end face of the ridge optical waveguide 22, there is a first planar metal Bragg grating 23. On the right side of the upper end face of the ridge optical waveguide 22, there is a second planar metal Bragg grating 24. A phase difference 27 is provided between the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24. On the tops of the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24, there is a second high-reflection HR film 28.

[0036] For the preparation process of the second high-reflection HR film 28, specifically: it is deposited on the tops of the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24 by magnetron sputtering. The material of the second high-reflection HR film 28 is a TiO2 / SiO2 multi-layer dielectric composite material, with each layer having a thickness of λ / 4, a thickness accuracy of ±5 nm, a reflectivity R3 > 99.5%, and a surface roughness less than 0.08 nm RMS, so as to achieve a high reflectivity and good optical performance.

[0037] Further, the phase difference 27 Δφ = π, and the phase control accuracy is < λ / 50 through atomic layer deposition technology.

[0038] In specific implementation, the ridge optical waveguide 22 has a width of 3 μm and a height of 2 μm, and the mode field matching degree with the gain chip 1 is > 98%.

[0039] In specific implementation, the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24 are of a Cr / Au structure, with a thickness of 50 nm / 150 nm, a reflectivity > 99.9%, and a 3 dB reflection bandwidth < 0.1 nm.

[0040] It should be noted that for the laser based on the dual metal Bragg grating and the top surface HR reflection film, the total length L of the external cavity cavity = 800 μm + L wg , and the free spectral range FSR > 100 GHz.

[0041] Embodiment 2 As Figures 1 - 4 shown, in this embodiment, the laser based on the dual metal Bragg grating and the top surface HR reflection film includes: a gain chip 1. On the left end face of the gain chip 1, a first high-reflection HR film 11 is plated, and on the right end face of the gain chip 1, a first anti-reflection AR film 12 is plated.

[0042] In specific implementation, the gain chip 1 adopts an InP / InGaAsP quantum well structure, with a central emission wavelength λ of 1610 nm. At an ambient temperature of 25 °C, the threshold current is lower than 22 mA, demonstrating good optoelectronic conversion performance. The thickness of the first antireflection AR film 12 is λ / 4, and the reflectivity R1 < 0.03% to reduce light reflection loss; the first high reflection HR film 11 is a SiO2 / TiO2 multi-layer high reflection film, with a reflectivity R2 > 99.9% to enhance optical feedback.

[0043] A metal Bragg grating waveguide 2 is arranged on the right side of the gain chip 1. The right end face of the gain chip 1 is aligned and attached to the left end face of the metal Bragg grating waveguide 2 to form an external cavity structure. The left end face of the metal Bragg grating waveguide 2 is coated with a second antireflection AR film 25, and the right end face of the metal Bragg grating waveguide 2 is coated with a third antireflection AR film 26.

[0044] In specific implementation, the length of the planar metal Bragg grating waveguide 2 is 3 cm, the grating period is 225 ± 0.3 nm, the duty cycle is 50 ± 1%, and the thickness of the Cr / Au layer is 200 ± 5 nm (50 nm Cr / 150 nm Au), forming a grating structure with a high reflectivity.

[0045] The metal Bragg grating waveguide 2 includes a grating waveguide substrate 21. A ridge optical waveguide 22 is arranged on the upper end face of the grating waveguide substrate 21. A first planar metal Bragg grating 23 is arranged on the left side of the upper end face of the ridge optical waveguide 22. A second planar metal Bragg grating 24 is arranged on the right side of the upper end face of the ridge optical waveguide 22. A phase difference 27 is arranged between the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24. A second high reflection HR film 28 is arranged on the tops of the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24.

[0046] The preparation process of the second high reflection HR film 28 is specifically as follows: It is deposited on the tops of the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24 by magnetron sputtering. The material of the second high reflection HR film 28 is selected as a TiO2 / SiO2 multi-layer dielectric composite material, with a thickness of λ / 4 for each layer, a thickness accuracy of ±5 nm, a reflectivity R3 > 99.5%, and a surface roughness of less than 0.08 nm RMS to achieve a high reflectivity and good optical performance.

[0047] Furthermore, the phase difference 27 Δφ = π, and the phase control accuracy < λ / 50 is achieved through atomic layer deposition technology.

[0048] In specific implementation, the ridge optical waveguide 22 has a width of 5 μm and a height of 4 μm, and the mode field matching degree with the gain chip 1 > 98%.

[0049] In specific implementation, the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24 are of Cr / Au structure, with a thickness of 50 nm / 150 nm, a reflectivity > 99.9%, and a 3 dB reflection bandwidth < 0.1 nm.

[0050] It should be noted that for the laser based on the dual-metal Bragg grating and the top HR reflection film, the total external cavity length L cavity = 800 μm + L wg , and the free spectral range FSR > 100 GHz.

[0051] Embodiment 3 As Figures 1 - 4 shown, in this embodiment, the laser based on the dual-metal Bragg grating and the top HR reflection film includes: a gain chip 1. A first high-reflection HR film 11 is plated on the left end face of the gain chip 1, and a first anti-reflection AR film 12 is plated on the right end face of the gain chip 1.

[0052] In specific implementation, the gain chip 1 adopts an InP / InGaAsP quantum well structure, with a central emission wavelength λ of 1550 nm. At an ambient temperature of 25 °C, the threshold current is lower than 22 mA, showing good optoelectronic conversion performance. The thickness of the first anti-reflection AR film 12 is λ / 4, and the reflectivity R1 < 0.03% to reduce optical reflection loss; the first high-reflection HR film 11 is a SiO2 / TiO2 multi-layer high-reflection film, with a reflectivity R2 > 99.9% to enhance optical feedback.

[0053] A metal Bragg grating waveguide 2 is arranged on the right side of the gain chip 1. The right end face of the gain chip 1 is aligned and attached to the left end face of the metal Bragg grating waveguide 2 to form an external cavity structure. A second anti-reflection AR film 25 is plated on the left end face of the metal Bragg grating waveguide 2, and a third anti-reflection AR film 26 is plated on the right end face of the metal Bragg grating waveguide 2.

[0054] In specific implementation, the length of the planar metal Bragg grating waveguide 2 is 2 cm, the grating period is 225 ± 0.3 nm, the duty cycle is 50 ± 1%, and the thickness of the Cr / Au layer is 200 ± 5 nm (50 nm Cr / 150 nm Au), forming a high-reflectivity grating structure.

[0055] The metal Bragg grating waveguide 2 includes a grating waveguide substrate 21. On the upper end face of the grating waveguide substrate 21, a ridge optical waveguide 22 is provided. On the left side of the upper end face of the ridge optical waveguide 22, a first planar metal Bragg grating 23 is provided. On the right side of the upper end face of the ridge optical waveguide 22, a second planar metal Bragg grating 24 is provided. A phase difference 27 is provided between the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24. On the tops of the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24, a second high-reflection HR film 28 is provided.

[0056] For the preparation process of the second high-reflection HR film 28, specifically: it is deposited on the tops of the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24 by magnetron sputtering. The material of the second high-reflection HR film 28 is selected as a TiO2 / SiO2 multi-layer dielectric composite material, with each layer having a thickness of λ / 4, a thickness accuracy of ±5 nm, a reflectivity R3 > 99.5%, and a surface roughness less than 0.08 nm RMS, so as to achieve a high reflectivity and good optical performance.

[0057] Furthermore, for the phase difference 27, Δφ = π, and the phase control accuracy < λ / 50 is achieved through atomic layer deposition technology.

[0058] In specific implementation, the ridge optical waveguide 22 has a width of 4 μm and a height of 3 μm, and the mode field matching degree with the gain chip 1 > 98%.

[0059] In specific implementation, the first planar metal Bragg grating 23 and the second planar metal Bragg grating 24 are of a Cr / Au structure, with a thickness of 50 nm / 150 nm, a reflectivity > 99.9%, and a 3 dB reflection bandwidth < 0.1 nm.

[0060] It should be noted that for the laser based on the dual metal Bragg grating and the top surface HR reflection film, the total length L of the external cavity cavity = 800 μm + L wg , and the free spectral range FSR > 100 GHz.

[0061] By performing performance tests on the three types of lasers provided in Example 1, Example 2, and Example 3, the test results show that: the line width is 0.6 kHz, the SMSR is 63 dB, and the threshold current is 22 mA, verifying the effectiveness of the present invention.

[0062] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser based on a bimetallic Bragg grating and a top surface HR reflective film, comprising a gain chip (1), characterized in that: The left end face of the gain chip (1) is coated with a first high reflection HR film (11), and the right end face of the gain chip (1) is coated with a first anti-reflection AR film (12); A metal Bragg grating waveguide (2) is arranged on the right side of the gain chip (1). The right end face of the gain chip (1) is aligned and bonded with the left end face of the metal Bragg grating waveguide (2) to form an external cavity structure. The left end face of the metal Bragg grating waveguide (2) is coated with a second anti-reflection AR film (25), and the right end face of the metal Bragg grating waveguide (2) is coated with a third anti-reflection AR film (26); The metal Bragg grating waveguide (2) includes a grating waveguide substrate (21). A ridge optical waveguide (22) is arranged on the upper end face of the grating waveguide substrate (21). A first planar metal Bragg grating (23) is arranged on the left side of the upper end face of the ridge optical waveguide (22), and a second planar metal Bragg grating (24) is arranged on the right side of the upper end face of the ridge optical waveguide (22). A phase difference (27) is arranged between the first planar metal Bragg grating (23) and the second planar metal Bragg grating (24). A second high reflection HR film (28) is arranged on the tops of the first planar metal Bragg grating (23) and the second planar metal Bragg grating (24).

2. The laser based on a bimetallic Bragg grating and a top HR reflective film according to claim 1, wherein: The gain chip (1) adopts an InP / InGaAsP quantum well structure, the central emission wavelength λ is 1550 nm, and the threshold current is lower than 22 mA at 25 °C.

3. The laser based on a bimetallic Bragg grating and a top HR reflective film according to claim 2, wherein For the preparation process of the second high reflection HR film (28), specifically: it is deposited on the tops of the first planar metal Bragg grating (23) and the second planar metal Bragg grating (24) by magnetron sputtering. The material of the second high reflection HR film (28) is selected as a TiO2 / SiO2 multi-layer dielectric composite material, the thickness of each layer is λ / 4, the thickness accuracy is ±5 nm, the reflectivity R3 > 99.5%, and the surface roughness is less than 0.08 nm RMS.

4. The laser based on a bimetallic Bragg grating and a top HR reflective film according to claim 2, characterized in that: The thickness of the first anti-reflection AR film (12) is λ / 4, and the reflectivity R1 < 0.03%; the first high reflection HR film (11) is a SiO2 / TiO2 multi-layer high reflection film, and the reflectivity R2 > 99.9%.

5. The laser based on a bimetallic Bragg grating and a top HR reflective film according to claim 1, wherein: The length of the planar metal Bragg grating waveguide (2) is 2 cm, the grating period is 225 ± 0.3 nm, and the duty cycle is 50 ± 1%.

6. The laser based on a bimetallic Bragg grating and a top HR reflective film according to claim 1, wherein: The ridge optical waveguide (22) has a width of 4 μm and a height of 3 μm, and the mode field matching degree with the gain chip (1) is > 98%.

7. The laser based on a bimetallic Bragg grating and a top HR reflective film according to claim 1, wherein: The first planar metal Bragg grating (23) and the second planar metal Bragg grating (24) are of a Cr / Au structure, with a thickness of 50 nm / 150 nm, a reflectivity > 99.9%, and a 3 dB reflection bandwidth < 0.1 nm.

8. The laser based on a bimetallic Bragg grating and a top HR reflective film according to claim 2, wherein: The phase difference (27) Δφ = π, and the phase control accuracy is < λ / 50 through atomic layer deposition technology.

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