Narrow linewidth laser based on external cavity grating waveguide and DFB chip

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a narrow linewidth laser based on an external cavity grating waveguide and a DFB chip. The high-reflection film is arranged on the left end surface of the DFB laser chip in a plating manner; the first antireflection film is arranged on the right end surface of the DFB laser chip in a plating manner; the grating optical waveguide chip is arranged on the right side of the DFB laser chip, and the left end face of the grating optical waveguide chip abuts against the right end face of the DFB laser chip; the second antireflection film is plated on the left end surface of the grating optical waveguide chip; the third antireflection film is plated on the right end surface of the grating optical waveguide chip; the grating optical waveguide chip comprises a waveguide substrate, and the waveguide substrate is made of an insulating transparent material. The method has the following beneficial effects: 1, the filtering sufficiency and the line width compression effect are remarkable; 2, the advantages of low loss and low power consumption are outstanding; 3, mode regulation and control are flexible, and stability and tunability are both considered; and 4, the compatibility is high.

Description

A narrow-linewidth laser based on external cavity grating waveguide and DFB chip Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to a narrow linewidth laser based on an external cavity grating waveguide and a DFB chip. Background Technology

[0002] Distributed feedback (DFB) lasers were developed in the 1970s to improve the monochromaticity and wavelength stability of lasers. They achieve wavelength selection and optical feedback by integrating a periodically varying refractive index grating structure into the laser cavity, replacing the end-face mirrors of traditional FP cavities, and utilizing the Bragg condition.

[0003] DFB lasers, due to their advantages of single-mode output, small size, and high reliability, have been widely used in optical communication, sensing, and other fields. However, traditional monolithic DFB lasers have the following core limitations, making it difficult to meet the demands of high-performance applications:

[0004] 1. Insufficient filtering and limited linewidth compression: The filtering function of traditional DFB lasers relies on a built-in distributed feedback grating, and the grating length is strictly equal to the resonant cavity length (typically 200-500μm). Limited by the cavity length, the grating has a short spectral filtering path, which can only achieve one filtering, resulting in a low side-mode suppression ratio (typically ≤40dB). The linewidth is difficult to break through the hundred kHz level (typical value 100-500kHz), which cannot meet the requirements of precision measurement and coherent communication for narrow linewidths at the kHz level and below.

[0005] 2. High absorption loss and high power consumption in resonant cavity materials: The resonant cavity of a DFB laser is composed of semiconductor gain materials (such as InP / InGaAsP, GaAs / AlGaAs). These materials provide optical gain while having extremely high absorption coefficients for laser light (the absorption coefficient of InP material at 1550nm is about 10cm⁻¹). If the resonant cavity is lengthened to improve the filtering effect, the absorption loss of light in the cavity will increase dramatically, requiring a significant increase in the driving current to maintain sufficient output power (when the cavity length is doubled, the driving current needs to increase by more than 50%), leading to a surge in power consumption. At the same time, the thermal effect generated by the large current will deteriorate the laser wavelength stability and further broaden the linewidth.

[0006] 3. Mode control relies on the gain chip, resulting in poor flexibility: The resonant mode of a traditional DFB laser is entirely determined by the built-in grating and cavity length of the gain chip, and cannot be independently controlled. When it is necessary to adjust the laser wavelength or optimize the mode, the operating current or temperature of the gain chip must be changed, which can easily cause problems such as gain fluctuations and linewidth broadening, making it difficult to meet the dual requirements of "narrow linewidth" and "tunability". Summary of the Invention

[0007] The purpose of this invention is to provide a narrow linewidth laser based on an external cavity grating waveguide and a DFB chip to solve the problems mentioned in the background art.

[0008] A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip, comprising:

[0009] DFB laser chip;

[0010] A high-reflectivity film is deposited on the left end face of the DFB laser chip;

[0011] A first antireflection film is deposited on the right end face of the DFB laser chip;

[0012] A grating waveguide chip is disposed on the right side of the DFB laser chip, and the left end face of the grating waveguide chip abuts against the right end face of the DFB laser chip.

[0013] The second antireflection film is deposited on the left end face of the grating waveguide chip;

[0014] The third antireflection film is deposited on the right end face of the grating waveguide chip;

[0015] The grating waveguide chip includes a waveguide substrate, wherein a back ridge waveguide is disposed on the upper part of the waveguide substrate, and a planar metal grating is etched on the upper part of the back ridge waveguide.

[0016] The waveguide substrate is an insulating transparent material with a thickness of 300-500μm.

[0017] As a preferred embodiment of the above technical solution, the waveguide substrate is made of quartz glass with a thickness of 300-500μm.

[0018] As a preferred embodiment of the above technical solution, the waveguide substrate is made of quartz glass with a thickness of 400μm.

[0019] As a preferred embodiment of the above technical solution, the waveguide substrate is made of sapphire material with a thickness of 300-500μm.

[0020] As a preferred embodiment of the above technical solution, the waveguide substrate is made of sapphire material with a thickness of 400μm.

[0021] As a preferred embodiment of the above technical solution, the emission center wavelength of the DFB laser chip is 1530-1610nm.

[0022] As a preferred embodiment of the above technical solution, the emission center wavelength of the DFB laser chip is 1550nm.

[0023] This invention provides a narrow linewidth laser based on an external cavity grating waveguide and a DFB chip, which has the following advantages:

[0024] 1. Significant filtering adequacy and linewidth compression: The outer cavity length is 3-10 times that of the DFB cavity length. Combined with the dual effects of "primary filtering + secondary filtering", the side mode rejection ratio is increased from the traditional 40dB to more than 50dB, and the linewidth compression ratio can reach 100:1 (e.g., 200KHz→2KHz), meeting the requirements of KHz-level narrow linewidth.

[0025] 2. Outstanding advantages in low loss and low power consumption: The external cavity waveguide uses a low-absorption material (absorption coefficient ≤ 0.1cm). -1 Even with an extended external cavity, losses remain minimal; simultaneously, external cavity feedback reduces dependence on DFB drive current, resulting in a 20%-30% reduction in current, a more than 20% reduction in power consumption, a significant reduction in thermal effects, and a 50% improvement in laser wavelength stability.

[0026] 3. Flexible mode control, balancing stability and tunability: The external cavity mode can be independently controlled via temperature / electric control without changing the DFB operating parameters, achieving wavelength tuning from 10-50nm. Simultaneously, the low-absorption material has a low coefficient of thermal expansion (e.g., silicon nitride 2.5×10⁻⁶). -6 / ℃), the linewidth variation of the laser during long-term operation (1000 hours) is ≤0.1KHz, and the power fluctuation is ≤±2%;

[0027] 4. Strong compatibility and wide range of applications: The external cavity grating waveguide can be adapted to DFB chips of different wavelengths (1064nm, 1550nm, 2μm) without redesigning the gain layer structure, and can be quickly expanded to fields such as sensing, communication, and precision measurement. Attached Figure Description

[0028] Figure 1 is a front view of the present invention;

[0029] Figure 2 is a top view of Figure 1.

[0030] In the figure: 1. DFB laser chip; 11. High reflectivity film; 12. First antireflection film; 2. Grating waveguide chip; 21. Waveguide substrate; 22. Back ridge waveguide; 23. Planar metal grating; 24. Second antireflection film; 25. Third antireflection film. Detailed Implementation

[0031] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0032] Example 1

[0033] A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip, comprising:

[0034] DFB laser chip 1;

[0035] High reflectivity film 11, the high reflectivity film 11 is deposited on the left end face of the DFB laser chip 1;

[0036] A first antireflection film 12 is deposited on the right end face of the DFB laser chip 1;

[0037] A grating waveguide chip 2 is disposed on the right side of the DFB laser chip 1, with the left end face of the grating waveguide chip 2 abutting against the right end face of the DFB laser chip 1.

[0038] The second antireflection film 24 is deposited on the left end face of the grating waveguide chip 2;

[0039] The third antireflection film 25 is deposited on the right end face of the grating waveguide chip 2;

[0040] The grating waveguide chip 2 includes a waveguide substrate 21, on which a back ridge waveguide 22 is disposed, and a planar metal grating 23 is etched on the upper part of the back ridge waveguide 22.

[0041] The waveguide substrate 21 is made of quartz glass with a thickness of 300μm.

[0042] The emission center wavelength of the DFB laser chip 1 is 1530nm.

[0043] Example 2

[0044] A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip, comprising:

[0045] DFB laser chip 1;

[0046] High reflectivity film 11, the high reflectivity film 11 is deposited on the left end face of the DFB laser chip 1;

[0047] A first antireflection film 12 is deposited on the right end face of the DFB laser chip 1;

[0048] A grating waveguide chip 2 is disposed on the right side of the DFB laser chip 1, with the left end face of the grating waveguide chip 2 abutting against the right end face of the DFB laser chip 1.

[0049] The second antireflection film 24 is deposited on the left end face of the grating waveguide chip 2;

[0050] The third antireflection film 25 is deposited on the right end face of the grating waveguide chip 2;

[0051] The grating waveguide chip 2 includes a waveguide substrate 21, on which a back ridge waveguide 22 is disposed, and a planar metal grating 23 is etched on the upper part of the back ridge waveguide 22.

[0052] The waveguide substrate 21 is made of quartz glass with a thickness of 400μm.

[0053] The emission center wavelength of the DFB laser chip 1 is 1550nm.

[0054] Example 3

[0055] A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip, comprising:

[0056] DFB laser chip 1;

[0057] High reflectivity film 11, the high reflectivity film 11 is deposited on the left end face of the DFB laser chip 1;

[0058] A first antireflection film 12 is deposited on the right end face of the DFB laser chip 1;

[0059] A grating waveguide chip 2 is disposed on the right side of the DFB laser chip 1, with the left end face of the grating waveguide chip 2 abutting against the right end face of the DFB laser chip 1.

[0060] The second antireflection film 24 is deposited on the left end face of the grating waveguide chip 2;

[0061] The third antireflection film 25 is deposited on the right end face of the grating waveguide chip 2;

[0062] The grating waveguide chip 2 includes a waveguide substrate 21, on which a back ridge waveguide 22 is disposed, and a planar metal grating 23 is etched on the upper part of the back ridge waveguide 22.

[0063] The waveguide substrate 21 is made of quartz glass with a thickness of 500μm.

[0064] The emission center wavelength of the DFB laser chip 1 is 1610nm.

[0065] Example 4

[0066] A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip, comprising:

[0067] DFB laser chip 1;

[0068] High reflectivity film 11, the high reflectivity film 11 is deposited on the left end face of the DFB laser chip 1;

[0069] A first antireflection film 12 is deposited on the right end face of the DFB laser chip 1;

[0070] A grating waveguide chip 2 is disposed on the right side of the DFB laser chip 1, with the left end face of the grating waveguide chip 2 abutting against the right end face of the DFB laser chip 1.

[0071] The second antireflection film 24 is deposited on the left end face of the grating waveguide chip 2;

[0072] The third antireflection film 25 is deposited on the right end face of the grating waveguide chip 2;

[0073] The grating waveguide chip 2 includes a waveguide substrate 21, on which a back ridge waveguide 22 is disposed, and a planar metal grating 23 is etched on the upper part of the back ridge waveguide 22.

[0074] The waveguide substrate 21 is made of sapphire and has a thickness of 400μm.

[0075] The emission center wavelength of the DFB laser chip 1 is 1550nm.

[0076] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip, characterized in that, include: DFB laser chip (1); high reflectivity film (11), the high reflectivity film (11) is deposited on the left end face of the DFB laser chip (1); first antireflection film (12), the first antireflection film (12) is deposited on the right end face of the DFB laser chip (1); grating waveguide chip (2), disposed on the right side of the DFB laser chip (1), the left end face of the grating waveguide chip (2) abuts against the right end face of the DFB laser chip (1); second antireflection film (24). The third antireflective coating (25) is deposited on the left end face of the grating waveguide chip (2); the third antireflective coating (25) is deposited on the right end face of the grating waveguide chip (2); the grating waveguide chip (2) includes a waveguide substrate (21), the waveguide substrate (21) has a back ridge waveguide (22) on its upper part, and a planar metal grating (23) is etched on the upper part of the back ridge waveguide (22); the waveguide substrate (21) is an insulating transparent material with a thickness of 300-500μm.

2. A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip according to claim 1, characterized in that: The waveguide substrate (21) is made of quartz glass with a thickness of 300-500μm.

3. A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip according to claim 2, characterized in that: The waveguide substrate (21) is made of quartz glass with a thickness of 400 μm.

4. A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip according to claim 1, characterized in that: The waveguide substrate (21) is made of sapphire with a thickness of 300-500μm.

5. A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip according to claim 4, characterized in that: The waveguide substrate (21) is made of sapphire and has a thickness of 400 μm.

6. A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip according to claim 1, characterized in that: The emission center wavelength of the DFB laser chip (1) is 1530-1610nm.

7. A narrow-linewidth laser based on an external cavity grating waveguide and a DFB chip according to claim 6, characterized in that: The emission center wavelength of the DFB laser chip (1) is 1550nm.

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