Silicon-based silicon oxide grating precise tuning external cavity narrow linewidth laser

Abstract

The utility model provides a silicon-based silicon oxide grating precise tuning external cavity narrow linewidth laser, which is used for solving the technical problems of insufficient wavelength control precision, low yield, complex processing, high cost and low coupling efficiency of the existing narrow linewidth laser. The laser comprises an active gain chip and a silicon-based silicon dioxide external cavity grating, the active gain chip is a single-ended adjustable laser, and emergent light of the active gain chip corresponds to the silicon-based silicon dioxide external cavity grating to form a resonant cavity. According to the utility model, through efficient coupling of the active gain chip and the silicon-based silicon dioxide external cavity grating, precise fine tuning of the central wavelength is realized in combination with the vernier effect, and meanwhile, the large-scale processing advantage of the silicon-based platform is utilized, so that the cost is reduced and the reliability is improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of semiconductor laser especially relates to a kind of precise tuning external cavity narrow linewidth laser. BACKGROUND

[0002] Narrow linewidth laser has important applications in the fields of precision measurement, optical communication, spectral analysis, etc. As a high-precision light source, narrow linewidth laser occupies a core position in modern optoelectronic technology, and its core advantage lies in the high monochromaticity and frequency stability of the output spectrum, which makes it a key device in the fields of precision interferometric measurement (such as gravitational wave detection, nanometer-level displacement sensing), high-speed coherent optical communication (such as 100G / 400G optical fiber transmission system), high-resolution spectral analysis (such as gas trace detection, atomic clock frequency reference), etc. With the continuous improvement of the requirements for light source wavelength accuracy (sub-picometer level), linewidth (below hundred kilohertz level) and long-term stability in the above-mentioned fields, traditional wide linewidth lasers (such as FP cavity lasers, with a linewidth usually >1 nm) have been unable to meet the demand, and existing narrow linewidth laser technologies mainly include distributed Bragg reflection (DBR) lasers, distributed feedback (DFB) lasers and external cavity lasers. Among them, external cavity lasers construct a resonant cavity through external optical elements (such as gratings, fiber Bragg gratings), which can realize linewidth compression and wavelength tuning. Existing technologies usually use semiconductor chips integrated with built-in gratings or externally connected body gratings, but there are the following problems: the wavelength tuning range of built-in gratings (such as DBR) is limited, and it relies on temperature or current adjustment, which is not accurate enough, the coupling efficiency of externally connected body gratings is low, the structure is complex and difficult to integrate; the processing cost of traditional external cavity grating materials (such as III-V semiconductor) is high, and it is difficult to mass-produce.

[0003] The invention patent with application number 202411673154.7 discloses an external cavity narrow linewidth laser assembly, which comprises a substrate, a gain chip for emitting laser light fixedly connected to the substrate, and a first light-transmitting mirror and a second light-transmitting mirror sequentially and spacedly arranged in the direction of the laser emission end of the gain chip. The first light-transmitting mirror is spacedly arranged with the gain chip and forms a first external optical resonant cavity together, and the second light-transmitting mirror is spacedly arranged with the first light-transmitting mirror and forms a second external optical resonant cavity together with the gain chip. The first external optical resonant cavity and the second external optical resonant cavity of the external cavity narrow linewidth laser assembly of the above-mentioned application greatly increase the resonant cavity length in a limited tube space. The longer the resonant cavity length, the longer the coherent light length, and thus the narrower the linewidth, which realizes higher performance while maintaining lower cost. However, the above-mentioned patent has poor center wavelength consistency, and the center wavelength only depends on the external cavity grating mode selector, which cannot accurately control the center wavelength. UTILITY MODEL CONTENTS

[0004] The utility model proposes a kind of silicon-based silicon oxide grating precision tuning external cavity narrow linewidth laser aiming at the technical problems, such as wavelength control accuracy insufficient of existing narrow linewidth laser, low yield, processing complex cost high and coupling efficiency low, external cavity narrow linewidth laser structure design is carried out based on silicon-based silicon dioxide Bragg grating, the precision fine adjustment of center wavelength is realized by integrated design and vernier effect, output wavelength is accurately controlled, and the processing advantage of silicon-based material is utilized to reduce cost and improve reliability.

[0005] In order to achieve the above object, the technical scheme of the utility model is as follows: a kind of silicon-based silicon oxide grating precision tuning external cavity narrow linewidth laser, including active gain chip and silicon-based silicon dioxide external cavity grating, active gain chip is single-end adjustable laser, the outgoing light of active gain chip and silicon-based silicon dioxide external cavity grating correspond to form resonant cavity.

[0006] Preferably, the side of the active gain chip away from the outgoing light is provided with a distributed Bragg grating, which serves as a wavelength selection cavity surface and changes the effective refractive index by applying current injection to select the mode.

[0007] Preferably, a coupling unit is provided between the active gain chip and the silicon-based silicon dioxide external cavity grating, and the coupling unit is arranged on the outgoing light of the active gain chip.

[0008] Preferably, the coupling unit includes a focusing lens and an isolator arranged in sequence, the focusing lens is arranged on the outgoing light side of the active gain chip, the centers of the focusing lens and the isolator are on the same horizontal line as the center of the outgoing light of the active gain chip, and the output end of the isolator corresponds to the input end of the silicon-based silicon dioxide external cavity grating.

[0009] Preferably, the silicon-based silicon dioxide external cavity grating is provided with a Bragg grating structure corresponding to the outgoing light of the active gain chip, and the Bragg grating structure selects the mode.

[0010] Preferably, the grating reflectivity of the distributed Bragg grating is ≥90%, and the adjustable range of the reflectivity of the silicon-based silicon dioxide external cavity grating is 30%-80%.

[0011] Preferably, the active gain chip adopts a quantum well structure, which can increase the light-emitting efficiency and improve the carrier coincidence efficiency.

[0012] Preferably, the outgoing end and the current injection end of the active gain chip are both provided with an antireflection film, which reduces the interference of the F-P cavity surface on the mode selection.

[0013] Preferably, the silicon-based silicon dioxide external cavity grating is prepared based on a silicon-based silicon dioxide waveguide.

[0014] Preferably, the silicon-based silicon dioxide waveguide is subjected to hydrogen loading treatment, and a Bragg grating structure is formed by using ultraviolet lithography technology. The Bragg grating structure acts as a mode selection device of an external cavity, and cooperates with the Bragg grating on the single-end adjustable laser to form a mode selection.

[0015] Compared with the prior art, the utility model has the advantages that:

[0016] 1. Wavelength control precision: through the vernier effect of the distributed Bragg grating and the external cavity grating, combined with current injection tuning, high-precision fine tuning of the center wavelength is realized, the required narrow linewidth center wavelength is met, the center wavelength consistency and mass production consistency correction are improved.

[0017] 2. Easy to mass production: the silicon-based silicon dioxide external cavity grating adopts mature ultraviolet lithography process, the hydrogen loading cost is low, and it is compatible with the semiconductor manufacturing platform, the lithography cost is reduced, and the production yield is improved.

[0018] 3. High reliability and stability: the isolator effectively suppresses optical feedback, hydrogen loading treatment enhances the long-term stability of the silicon-based silicon dioxide external cavity grating, and the quantum well structure guarantees the mode stability under high power output; the silicon-based material has good thermal stability.

[0019] 4. High-efficiency coupling: the end face coupling design of the integrated microlens and the silicon-based waveguide significantly improves the light field matching efficiency of the external cavity and the active chip, and has low insertion loss.

[0020] The utility model realizes precise fine tuning of the center wavelength through the efficient coupling of the quantum well active gain chip and the silicon-based silicon dioxide external cavity grating, and combines the vernier effect, simultaneously utilizes the large-scale processing advantage of the silicon-based platform, reduces the cost and improves the reliability. ACCURACY

[0021] In order to more clearly illustrate the technical scheme in the embodiments of the utility model or the prior art, the drawings needed to be used in the embodiment or the prior art description will be briefly introduced below, and obviously, the drawings in the following description are only some embodiments of the utility model, and those skilled in the art can also obtain other drawings according to these drawings without creating creative labor.

[0022] Figure 1 It is the structural schematic diagram of the utility model.

[0023] Figure 2 It is Figure 1 It is the structural diagram of the active gain chip.

[0024] Figure 3 It is the wavelength tuning principle schematic diagram of the utility model.

[0025] In the figure, 1 is the active gain chip, 2 is the focusing lens, 3 is the isolator, 4 is the silicon dioxide external cavity grating, 11 is the antireflection coating, 13 is the grating region electrode, 14 is the gain region electrode, 15 is the negative electrode, and 16 is the distributed Bragg grating. Detailed Implementation

[0026] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0027] like Figure 1 As shown, a silicon-based silicon dioxide grating precision tuned external cavity narrow linewidth laser includes an active gain chip 1 and a silicon-based silicon dioxide external cavity grating 4. The active gain chip 1 is a single-ended adjustable laser. The emitted light from the active gain chip 1 corresponds to the grating structure of the silicon-based silicon dioxide external cavity grating 4 to form a resonant cavity.

[0028] like Figure 2 As shown, the active gain chip 1 adopts a quantum well structure, which can increase luminous efficiency and improve carrier recombination efficiency. A high-reflectivity distributed Bragg grating 16 is formed at one end of the active gain chip 1 through a docking growth process, and antireflection films 11 are deposited at both ends, with a reflectivity ≤2%. The docked-grown distributed Bragg grating 16 serves as a wavelength-selective cavity surface, reflecting wavelengths within a narrow characteristic band. The antireflection film 11 reduces interference from the FP cavity surface on mode selection. The lower part of the active gain chip 1 has a negative electrode 15 for the grating region and the active region, while the upper part has a grating region electrode 13 and a gain region electrode 14. The grating region electrode 13 and the gain region electrode 14 are connected to the positive electrode of the laser driver, respectively. The negative electrode 15 is a common electrode connected to the negative electrode of the laser driver. Current injection into the grating region changes the carrier concentration, thereby altering the effective refractive index of the distributed Bragg grating 16 and thus changing the reflected wavelength for mode selection.

[0029] A coupling unit is arranged between the active gain chip 1 and the silicon-based silica outer cavity grating 4, the coupling unit comprises a focusing lens 2 and an isolator 3, the centers of the focusing lens 2 and the isolator 3 are on the same horizontal line with the outgoing light of the active gain chip 1. The focusing lens 2 is located on the side of the active gain chip 1 without the distributed Bragg grating 16, and is used for collimating and focusing the outgoing light to the isolator 3. The isolator 3 is used for preventing the outer cavity reflected light from feeding back to the active gain chip 1, avoiding mode instability, and coupling to the silicon-based silica outer cavity grating 4 after the isolator 3. The model of the isolator 3 is SMT55C2MK117D, and the wavelength is 1550±20nm.

[0030] The silicon-based silica outer cavity grating 4 is prepared based on a silicon-based silica waveguide. After hydrogen loading treatment, a periodic refractive index modulated Bragg grating structure is formed by using ultraviolet lithography technology, and the center wavelength and reflectivity are adjusted by controlling the grating period and number. The center wavelength is related to the effective refractive index of the waveguide and the Bragg period, and λ=2Λneff, wherein Λ is the grating period of the Bragg wavelength, and neff is the effective refractive index of the grating. The longer the period is, the higher the reflectivity is. The reflectivity range is adjustable from 30% to 80%. The Bragg grating structure is arranged in the middle of the silicon-based silica outer cavity grating 4. The Bragg grating structure acts as a mode selector of the outer cavity, and cooperates with the Bragg grating on the single-end DBR to form mode selection by reflecting a narrow band wavelength. Only the wavelength satisfying the reflection of the two Bragg gratings can resonate and output light.

[0031] The preparation method of the utility model discloses the following steps:

[0032] Step 1: preparing the active gain chip 1 of quantum well structure: the DBR grating layer, i.e. the distributed Bragg grating 16, is grown by metal organic chemical vapor deposition (MOCVD) on one end of the active gain chip 1, the grating reflectivity is greater than or equal to 90%, and AR antireflection film 11 is coated on the end faces of both ends, and the reflectivity is less than or equal to 2%.

[0033] Step 2: preparing the silicon-based silica outer cavity grating 4: hydrogen loading treatment is carried out on the silicon-based silica waveguide, the hydrogen loading is 80°13Mpa, the time is 3 days, and the photosensitivity is improved; ultraviolet holographic lithography technology is used to expose the surface of the silicon-based silica waveguide to form a Bragg grating structure with a center wavelength period, the period number N is controlled to be 100, and the reflectivity is 50%.

[0034] Step 3: encapsulation integration, fixing the active gain chip 1 to the base, bonding the focusing lens 2 and the isolator 3 in sequence on the side without the distributed Bragg grating 16, using ultraviolet curing glue to paste the focusing lens 2 and the isolator 3 on the base plate, aligning the output end of the isolator 3 and the input end of the silicon-based silica external cavity grating 4 through a high-precision coupling device to realize light field coupling. The high-precision coupling device is a built six-dimensional adjustment frame, through an adjustment arm, holding the external cavity grating, and through adjusting the six-dimensional adjustment frame to accurately couple with the light output by the lens.

[0035] Step 4: wavelength tuning, applying current injection (0-50mA) at the DBR grating end of the active gain chip 1, using the refractive index change caused by carrier injection to form a vernier effect with the wavelength of the Bragg grating structure of the silicon-based silica external cavity grating 4, and realizing fine tuning of the center wavelength (tuning range≥1nm, accuracy≤0.1pm).

[0036] Figure 3 It is a schematic diagram of wavelength tuning principle, which illustrates the vernier effect of the DBR grating and the silicon-based silica external cavity grating 4 and the adjustment mechanism of the current injection on the center wavelength. The red one is the reflection spectrum of the silicon-based silica external cavity grating 4, and the black one is the reflection spectrum of the DBR grating. The intersection of the reflection spectrum of the silicon-based silica external cavity grating 4 and the reflection spectrum of the distributed Bragg grating 16 is the middle position, which is the lasing wavelength. With the DBR grating current injection, the reflection spectrum of the distributed Bragg grating 16 moves to the left to get the reflection spectrum 18, and the lasing wavelength also changes, that is, the center wavelength of the lasing wavelength moves from 42 to 43, which can be accurately controlled to achieve the required accurate center wavelength.

[0037] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A silicon-based silicon-oxide grating precisely-tuned external-cavity narrow-line-width laser, characterized in that, The active gain chip (1) and the silicon-based silica external cavity grating (4) are included, the active gain chip (1) is a single-ended adjustable laser, and the outgoing light of the active gain chip (1) corresponds to the silicon-based silica external cavity grating (4) to form a resonant cavity.

2. The silicon-based silicon-oxide grating precisely tunable external-cavity narrow-line-width laser of claim 1, wherein, A distributed Bragg grating (16) is arranged on the side of the active gain chip (1) away from the outgoing light, and the distributed Bragg grating (16) is used as a wavelength selection cavity surface and changes the effective refractive index by overcurrent injection to select a mode.

3. The silicon-based silicon-oxide grating precisely tunable external-cavity narrow-line-width laser of claim 2, wherein, A coupling unit is arranged between the active gain chip (1) and the silicon-based silica external cavity grating (4), and the coupling unit is arranged on the outgoing light of the active gain chip (1).

4. The silicon-based silicon-oxide grating precisely tunable external-cavity narrow-line-width laser of claim 3, wherein, The coupling unit includes a focusing lens (2) and an isolator (3) arranged in sequence, the focusing lens (2) is arranged on the outgoing light side of the active gain chip (1), the centers of the focusing lens (2) and the isolator (3) are on the same horizontal line as the center of the outgoing light of the active gain chip (1), and the output end of the isolator (3) corresponds to the input end of the silicon-based silica external cavity grating (4).

5. The silicon-based silicon-oxide grating precisely tunable external cavity narrow line-width laser of any one of claims 2-4, wherein, The silicon-based silica external cavity grating (4) is provided with a Bragg grating structure corresponding to the outgoing light of the active gain chip (1).

6. The silicon-based silicon-oxide grating precisely tunable external-cavity narrow-line-width laser of claim 5, wherein, The grating reflectivity of the distributed Bragg grating (16) is greater than or equal to 90%, and the adjustable range of the reflectivity of the silicon-based silica external cavity grating (4) is 30%-80%.

7. The silicon-based silicon-oxide grating precisely tunable external-cavity narrow-line-width laser of claim 6, wherein, The active gain chip (1) adopts a quantum well structure.

8. The silicon-based silicon-oxide grating precise tuning external cavity narrow line width laser according to claim 6 or 7, characterized in that, The outgoing end and the current injection end of the active gain chip (1) are both provided with an anti-reflection film (11).

9. The silicon-based silicon-oxide grating precise tuning external cavity narrow line-width laser of claim 8, wherein, The silicon-based silica external cavity grating (4) is prepared based on a silicon-based silica waveguide.

10. The silicon-based silicon-oxide grating precise tuning external cavity narrow line-width laser of claim 9, wherein, The silicon-based silica waveguide is subjected to hydrogen loading treatment, and a Bragg grating structure is formed by using ultraviolet lithography technology.

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