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CN-120601252-B - External cavity laser for realizing narrow linewidth by phase difference regulation and control of bimetallic Bragg grating

CN120601252BCN 120601252 BCN120601252 BCN 120601252BCN-120601252-B

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to an external cavity laser for realizing narrow linewidth by regulating and controlling the phase difference of a bimetallic Bragg grating, which comprises a gain chip, a first high reflection HR film, a second high reflection HR film and a first anti-reflection AR film, wherein the left end face of the gain chip is plated with the first high reflection HR film; the right side of the gain chip is provided with a metal Bragg grating waveguide, the right end face of the gain chip is aligned with the left end face of the metal Bragg grating waveguide to be attached to form an outer cavity structure, the left end face of the metal Bragg grating waveguide is plated with a second anti-reflection AR film, and the right end face of the metal Bragg grating waveguide is plated with a third anti-reflection AR film. Through tests, the invention utilizes the interference enhancement effect and the mode suppression mechanism to improve the Side Mode Suppression Ratio (SMSR) to 65dB and compress the line width to 0.6kHz.

Inventors

  • YU SHOUSHAN

Assignees

  • 聚光科芯(苏州)光电子科技有限公司

Dates

Publication Date
20260508
Application Date
20250429

Claims (7)

  1. 1. The external cavity laser for realizing narrow linewidth by the phase difference regulation of the bimetallic Bragg grating comprises a gain chip (1) and is characterized in that 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); The right side of the gain chip (1) is provided with a metal Bragg grating waveguide (2), the right end face of the gain chip (1) is aligned and attached with the left end face of the metal Bragg grating waveguide to form an outer cavity structure, the left end face of the metal Bragg grating waveguide (2) is plated with a second anti-reflection AR film (25), and the right end face of the metal Bragg grating waveguide (2) is plated with a third anti-reflection AR film (26); The metal Bragg grating waveguide (2) comprises 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 metal Bragg reflection grating (23) is arranged on the left side of the upper end face of the ridge optical waveguide (22), a second metal Bragg reflection grating (24) is arranged on the right side of the upper end face of the ridge optical waveguide (22), and a phase difference (27) is arranged between the first metal Bragg reflection grating (23) and the second metal Bragg reflection grating (24).
  2. 2. The external cavity laser for realizing narrow linewidth by dual metal Bragg grating phase difference modulation according to claim 1, wherein the phase difference (27) is delta phi = pi.
  3. 3. The external cavity laser for realizing narrow linewidth by phase difference regulation and control of the bimetallic Bragg grating according to claim 2, wherein the phase difference (27) realizes phase control precision < lambda/50 by an atomic layer deposition technology.
  4. 4. The external cavity laser for realizing narrow linewidth by the phase difference regulation and control of the bimetallic Bragg grating according to claim 1, wherein the length of the metal Bragg grating waveguide (2) is 1-3cm, the period is 220-230nm, and the surface roughness is less than 0.8nm.
  5. 5. The external cavity laser for realizing narrow linewidth by phase difference regulation and control of the bimetallic Bragg grating according to claim 4, wherein the length of the metal Bragg grating waveguide (2) is 2cm, the period is 225nm, and the surface roughness is less than 0.8nm.
  6. 6. The external cavity laser for realizing narrow linewidth by the phase difference regulation and control of the bimetallic Bragg grating according to claim 1, wherein the ridge optical waveguide (22) is 3-5 μm wide and 2-4 μm high, and the matching degree of the ridge optical waveguide and the mode field of the gain chip (1) is more than 98%.
  7. 7. The external cavity laser for realizing narrow linewidth by the phase difference regulation and control of the bimetallic Bragg grating according to claim 6, wherein the ridge optical waveguide (22) is 4 μm wide and 3 μm high, and the matching degree of the ridge optical waveguide and the mode field of the gain chip (1) is more than 98%.

Description

External cavity laser for realizing narrow linewidth by phase difference regulation and control of bimetallic Bragg grating Technical Field The invention relates to the technical field of semiconductor lasers, in particular to an external cavity laser for realizing narrow linewidth by phase difference regulation of a bimetallic Bragg grating. Background A laser is a device that generates high-intensity, high-directivity, high-monochromaticity coherent light by the principle of stimulated radiation. The laser consists of three parts, namely a working substance, a pumping source and a resonant cavity, wherein the working substance (such as a crystal, a gas or a semiconductor) absorbs energy and is excited to a high energy state, photons are released through stimulated radiation, and the resonant cavity repeatedly oscillates the photons through a reflecting mirror to form light amplification and finally outputs laser. Limitations of the prior art: 1. Performance limitations of DFB lasers 1.1, Limited by carrier density fluctuation and lasing cavity length (typically 0.5 mm), line width is usually 1-10MHz (Optics Express, 2021), and cannot meet application requirements such as coherent detection. 1.2, The secondary epitaxy process results in a yield of only 65-70% (Photonics Research, 2021), which is 2-3 times higher than that of external cavity lasers. 1.3, The reflectivity of the semiconductor grating (93-95%) needs additional gain compensation, resulting in 15-20% increase in power consumption. 2. Shortcomings of conventional external cavity lasers 2.1, Single grating structure Side Mode Suppression Ratio (SMSR) of only 45-50dB, linewidth of about 20-50kHz (IEEE Photonics Technology Letters, 2020). 2.2, The beam quality and the integration are difficult to be compatible, and a complex optical alignment process is required. Disclosure of Invention The invention provides an external cavity laser for realizing narrow linewidth by phase difference regulation of a bimetallic Bragg grating, which aims to solve the problems in the background technology. In order to achieve the purpose, the external cavity laser with the narrow linewidth is realized by the phase difference regulation and control of the bimetallic Bragg grating, and the external cavity laser comprises a gain chip, wherein a first high reflection HR film is plated on the left end face of the gain chip, and a first anti-reflection AR film is plated on the right end face of the gain chip. The right side of the gain chip is provided with a metal Bragg grating waveguide, the right end face of the gain chip is aligned with the left end face of the metal Bragg grating waveguide to be attached to form an outer cavity structure, the left end face of the metal Bragg grating waveguide is plated with a second anti-reflection AR film, and the right end face of the metal Bragg grating waveguide is plated with a third anti-reflection AR film. The metal Bragg grating waveguide comprises a grating waveguide substrate, a ridge optical waveguide is arranged on the upper end face of the grating waveguide substrate, a first metal Bragg reflection grating is arranged on the left side of the upper end face of the ridge optical waveguide, a second metal Bragg reflection grating is arranged on the right side of the upper end face of the ridge optical waveguide, and a phase difference is arranged between the first metal Bragg reflection grating and the second metal Bragg reflection grating. As the preferable choice of the technical proposal, the length of the metal Bragg grating waveguide is 1-3cm, the period is 220-230nm, and the surface roughness is less than 0.8nm. As a preferable mode of the above technical scheme, the length of the metal bragg grating waveguide is 2cm, the period is 225nm, and the surface roughness is <0.8nm. As a preferable aspect of the above-described aspect, the phase difference ΔΦ=pi. As a preferred aspect of the above-described technical solution, the phase difference achieves a phase control accuracy < λ/50 by an atomic layer deposition technique. As the preferable choice of the technical proposal, the ridge optical waveguide has the width of 3-5 μm and the height of 2-4 μm, and the matching degree with the mode field of the gain chip is more than 98 percent. As a preferable mode of the technical scheme, the ridge optical waveguide has a width of 4 μm and a height of 3 μm, and the matching degree of the ridge optical waveguide and the mode field of the gain chip is more than 98%. The invention provides an external cavity laser for realizing narrow linewidth by phase difference regulation and control of a bimetallic Bragg grating, which has the following beneficial effects: 1. The interference enhancement is that the reflected light of the two gratings constructively interfere in the cavity, and the reflectivity of the main peak reaches 99.9 percent (95 percent of the traditional single grating). 2. Mode suppression-non-lasing mode is suppressed du