A high-speed tunable wavelength narrow linewidth external cavity laser

Abstract

The application relates to the technical field of semiconductor lasers, in particular to a high-speed wavelength-tunable narrow-line-width external cavity laser, which comprises an InP gain chip optical waveguide, the left end face of the InP gain chip optical waveguide is coated with an optical high-reflection film, and the right end face is coated with a first optical antireflection film; further comprising a lithium niobate waveguide, the left end face of the lithium niobate waveguide is coated with a second optical antireflection film, and the right end face is coated with a third optical antireflection film; a lithium niobate thin-film Bragg grating waveguide is arranged on the upper end face of the lithium niobate waveguide, a SiO2 layer is arranged below the lithium niobate thin-film Bragg grating waveguide, and a Si substrate is arranged below the SiO2 layer; the right end face of the InP gain chip optical waveguide is aligned and attached to the left end face of the lithium niobate waveguide, forming an external cavity structure; and a voltage control unit is further arranged on the upper end face of the lithium niobate waveguide. The application realizes 0.8 kHz line width, 50 nm tuning range and M2<1.2 beam quality through 1-3 cm super-long grating and mode matching optimization, and has the advantages of mu s level response speed of the device.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor lasers, in particular to a high-speed wavelength-tunable narrow-linewidth external cavity laser. BACKGROUND

[0002] An electro-optically tunable semiconductor laser is a semiconductor laser device that realizes continuous wavelength tuning based on the electro-optic effect. The core principle is to change the refractive index of the semiconductor material or the resonant cavity parameters by applying an external electric field, thereby adjusting the output laser wavelength. This type of laser usually adopts an external cavity structure, combined with electrically controlled gratings, micro-electro-mechanical systems (MEMS) or integrated waveguides, etc. Tuning elements can realize rapid wavelength switching in tens to hundreds of nanometers. Compared with the traditional mechanical tuning method, electro-optical tuning has the advantages of fast response speed (up to nanoseconds), high tuning accuracy (sub-pico meter level) and strong stability.

[0003] Limitations of the prior art:

[0004] Temperature-tuned laser: slow response speed, poor wavelength stability (temperature drift > 0.1 nm / ℃).

[0005] Mechanical tuning laser: large volume, high cost, difficult to integrate;

[0006] DFB laser: the line width limit is about 100 kHz, which cannot meet the emerging needs of quantum communication (<1 kHz), long-distance laser radar (<2 kHz) and the like. SUMMARY

[0007] The purpose of the present application is to provide a high-speed wavelength-tunable narrow-linewidth external cavity laser to solve the problems raised in the background art.

[0008] To achieve the above purpose, the present application provides the following technical scheme, a high-speed wavelength-tunable narrow-linewidth external cavity laser, comprising:

[0009] An InP gain chip optical waveguide with a wavelength of 1530-1630 nm, the left end face of which is coated with an optical high-reflection film, and the right end face of which is coated with a first optical antireflection film; the bottom of the InP gain chip optical waveguide is provided with an InP substrate;

[0010] Further comprising a lithium niobate waveguide with a length L wg =1-3cm, and a period A=220-230nm, the left end face of the lithium niobate waveguide is coated with a second optical antireflection film, and the right end face of the lithium niobate waveguide is coated with a third optical antireflection film; a lithium niobate thin film Bragg grating waveguide is arranged on the upper end face of the lithium niobate waveguide, a SiO2 layer is arranged below the lithium niobate thin film Bragg grating waveguide, and a Si substrate is arranged below the SiO2 layer;

[0011] The right end surface of the InP gain chip optical waveguide is aligned and attached to the left end surface of the lithium niobate waveguide to form an external cavity structure, and the total length of the external cavity is L cavity =L wg +L chip (L chip =500-1000μm);

[0012] The upper end surface of the lithium niobate waveguide is also provided with a voltage control unit, which includes a metal electrode + and a metal electrode -, which are arranged on the front and back sides of the lithium niobate thin film Bragg grating waveguide in sequence.

[0013] Further, the lithium niobate waveguide has a length L wg =2cm, and a period Λ=225nm.

[0014] Further, the lithium niobate thin film Bragg grating waveguide has a ridge structure with a width of 3-5μm and a height of 2-3μm.

[0015] Further, the lithium niobate thin film Bragg grating waveguide has a ridge structure with a width of 4μm and a height of 3μm.

[0016] Further, the InP gain chip optical waveguide is provided with a back light electric detector chip on the side of the optical high reflection film, and the back light electric detector chip is connected with a PID feedback module; the back light electric detector chip controlled by PID collects feedback signals of output voltage in real time, compares them with a set target value to generate error signals, quickly responds to error amplitudes through a proportional (P) link, eliminates steady-state deviations through an integral (I) link, predicts voltage fluctuation trends through a differential (D) link, and comprehensively adjusts control quantities to stabilize the output voltage at the target value; the metal electrode +, the metal electrode -, and the back light electric detector chip controlled by PID are electrically connected to realize wavelength closed-loop control.

[0017] Further, the laser has a line width ≤1kHz and a wavelength tuning range of 50nm-100nm.

[0018] The manufacturing method of the high-speed tunable wavelength narrow line width external cavity laser includes the following specific steps:

[0019] S1, a ridge waveguide on a lithium niobate waveguide is manufactured by proton exchange method, Δn=0.05, and an electron beam lithography defines a Bragg grating with a period accuracy of ±1nm;

[0020] S2, Cr / Au electrodes are evaporated on the lithium niobate waveguide with a thickness of 200nm;

[0021] S3, an InP gain chip optical waveguide is aligned and attached to the lithium niobate waveguide with an accuracy of ±1μm, a TEC temperature control module is integrated, and the temperature stability is ±0.01℃.

[0022] Further, the high-speed tunable wavelength narrow linewidth external cavity laser is applied to the fields of optical communication, quantum key distribution and precise spectrum measurement.

[0023] The application provides a high-speed tunable wavelength narrow linewidth external cavity laser, and has the following beneficial effects:

[0024] 1. Super-long Bragg grating design:

[0025] The lithium niobate thin film optical waveguide technology is adopted, the grating length L wg =1-3cm (300um for a traditional DFB), according to Δλ∝1 / L, the linewidth is compressed to 0.8kHz.

[0026] 2. Double-end anti-reflection film optimization:

[0027] The reflectivity of the first optical anti-reflection film, the second optical anti-reflection film and the third optical anti-reflection film on the end face of the InP gain chip optical waveguide and the lithium niobate waveguide is less than 0.1%, the out-of-cavity loss is less than 0.5dB, and the optical field coupling efficiency is greater than 95%;

[0028] 3. External cavity mode matching:

[0029] The ridge waveguide has a width of 3-5um and a height of 2-3um, and single-mode output (M²<1.2) is realized;

[0030] 4. Tuning principle:

[0031] When a voltage of 0-10V is applied, the lithium niobate refractive index change Δn≈10 -3 , the Bragg wavelength (Δλ_B=2Δn・Λ) and the effective cavity length of the external cavity (ΔL=Δn・L wg ) are synchronously adjusted, and wide-range tuning (Δλ≥50nm) is realized. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a front view of the application;

[0033] Figure 2 It is a top view of the application.

[0034] In the figure: 1, InP gain chip optical waveguide; 11, InP substrate; 12, optical high-reflection film; 13, first optical anti-reflection film; 2, lithium niobate waveguide; 21, second optical anti-reflection film; 22, third optical anti-reflection film; 23, Si substrate; 24, SiO2 layer; 25, lithium niobate thin film Bragg grating waveguide; 3, voltage control unit; 31, metal electrode +; 32, metal electrode -; 33, back light electric detector chip. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application.

[0036] Bragg wavelength tuning amount:

[0037] Δλ B =2(r 33 ·E·n eff ³ / 2)·Λ

[0038] (E is electric field intensity, r 33 =30.8pm / V, n eff =2.2-2.3)

[0039] External cavity linewidth formula:

[0040] Δλ=λ² / (2π·L cavity =·Δλ_B)

[0041] (L cavity =1.5-4cm, Δλ_B=0.1-0.3nm)

[0042] Embodiment 1

[0043] As shown in Figure 1 and Figure 2 , in this embodiment, a high-speed tunable wavelength narrow linewidth external cavity laser includes:

[0044] An InP gain chip optical waveguide 1 emits a wavelength of 1530-1630nm, and the left end face is coated with an optical high reflection film 12, and the right end face is coated with a first optical antireflection film 13; the bottom of the InP gain chip optical waveguide 1 is provided with an InP substrate 11;

[0045] Further comprising a lithium niobate waveguide 2, length L wg =1cm, period Λ=220nm, the left end face of the lithium niobate waveguide 2 is coated with a second optical antireflection film 21, and the right end face of the lithium niobate waveguide 2 is coated with a third optical antireflection film 22; the upper end face of the lithium niobate waveguide 2 is provided with a lithium niobate thin film Bragg grating waveguide 25, the lower side of the lithium niobate thin film Bragg grating waveguide 25 is provided with a SiO2 layer 24, and the lower side of the SiO2 layer 24 is provided with a Si substrate 23;

[0046] The right end face of the InP gain chip optical waveguide 1 is aligned and attached to the left end face of the lithium niobate waveguide 2 to form an external cavity structure, and the total length of the external cavity L cavity =L wg +L chip (L chip =500-1000μm);

[0047] The upper end face of the lithium niobate waveguide 2 is also provided with a voltage control unit 3, which includes a metal electrode +31 and a metal electrode -32, which are arranged in front and back of the lithium niobate thin film Bragg grating waveguide 25 in turn;

[0048] Further, the lithium niobate thin film Bragg grating waveguide 25 is a ridge structure with a width of 3μm and a height of 2μm;

[0049] Further, the InP gain chip optical waveguide 1 is provided with a back light electric detector chip 33 on the side of the optical high reflection film 12, and the back light electric detector chip 33 is connected with a PID feedback module; the back light electric detector chip 33 controlled by PID collects feedback signals of output voltage in real time, compares with the set target value to generate error signals, quickly responds to error amplitude through the proportional (P) link, eliminates steady-state deviation through the integral (I) link, predicts voltage fluctuation trend through the differential (D) link, and comprehensively adjusts the control amount to make the output voltage stable at the target value; the metal electrode +31, the metal electrode -32 and the back light electric detector chip 33 controlled by PID are electrically connected to realize wavelength closed-loop control;

[0050] Further, the laser linewidth is ≤1kHz, and the wavelength tuning range is 50nm-100nm;

[0051] The manufacturing method of the high-speed tunable wavelength narrow-linewidth external cavity laser, and the specific steps are as follows:

[0052] S1, a proton exchange method is used to manufacture a ridge waveguide on the lithium niobate waveguide 2, Δn=0.05, and an electron beam lithography is used to define a Bragg grating with a period accuracy of ±1nm;

[0053] S2, Cr / Au electrodes are evaporated on the lithium niobate waveguide 2 with a thickness of 200nm;

[0054] S3, the InP gain chip optical waveguide 1 is aligned and attached to the lithium niobate waveguide 2 with an accuracy of ±1μm, a TEC temperature control module is integrated, and the temperature stability is ±0.01℃;

[0055] Further, the high-speed tunable wavelength narrow-linewidth external cavity laser is applied in the fields of optical communication, quantum key distribution and precise spectrum measurement.

[0056] Embodiment 2

[0057] A high-speed tunable wavelength narrow-linewidth external cavity laser, comprising:

[0058] InP gain chip optical waveguide 1, the left end face is coated with optical high reflection film 12, the right end face is coated with first optical antireflection film 13; the bottom of the InP gain chip optical waveguide 1 is provided with InP substrate 11;

[0059] Further comprising lithium niobate waveguide 2, length L wg =3cm, period Λ=230nm, the left end face of the lithium niobate waveguide 2 is coated with second optical antireflection film 21, the right end face of the lithium niobate waveguide 2 is coated with third optical antireflection film 22; the upper end face of the lithium niobate waveguide 2 is provided with lithium niobate thin film Bragg grating waveguide 25, the lower side of the lithium niobate thin film Bragg grating waveguide 25 is provided with SiO2 layer 24, the lower side of the SiO2 layer 24 is provided with Si substrate 23;

[0060] The right end face of the InP gain chip optical waveguide 1 is aligned and adhered to the left end face of the lithium niobate waveguide 2 to form an external cavity structure, and the total length of the external cavity is L cavity =L wg +L chip (L chip =500-1000μm);

[0061] The upper end face of the lithium niobate waveguide 2 is further provided with voltage control unit 3, the voltage control unit 3 includes metal electrode +31 and metal electrode -32, the metal electrode +31 and the metal electrode -32 are sequentially arranged on the front and back sides of the lithium niobate thin film Bragg grating waveguide 25;

[0062] Further, the lithium niobate thin film Bragg grating waveguide 25 is in a ridge structure, with a width of 5μm and a height of 3μm;

[0063] Further, the InP gain chip optical waveguide 1 is provided with back light electric detector chip 33 on the side of the optical high reflection film 12, and the back light electric detector chip 33 is connected with PID feedback module; the back light electric detector chip 33 controlled by PID collects feedback signals of output voltage in real time, compares with set target value to generate error signals, quickly responds to error amplitude through proportional (P) link, eliminates steady-state deviation through integral (I) link, predicts voltage fluctuation trend through differential (D) link, and comprehensively adjusts control amount to stabilize output voltage at target value; the metal electrode +31, the metal electrode -32 and the back light electric detector chip 33 controlled by PID are electrically connected to realize wavelength closed-loop control;

[0064] Further, the laser has a line width ≤1kHz and a wavelength tuning range of 50nm-100nm;

[0065] The manufacturing method of the high-speed tunable wavelength narrow line width external cavity laser, and the specific steps are as follows:

[0066] S1, ridge waveguide on lithium niobate waveguide 2 is made by proton exchange method, Δn = 0.05, electron beam lithography defines Bragg grating, period accuracy ± 1 nm;

[0067] S2, Cr / Au electrode is evaporated on lithium niobate waveguide 2, thickness 200 nm;

[0068] S3, InP gain chip optical waveguide 1 is aligned and attached to lithium niobate waveguide 2, accuracy ± 1 μm, integrated TEC temperature control module, temperature stability ± 0.01 ℃;

[0069] Further, the application of the high-speed tunable wavelength narrow linewidth external cavity laser in the field of optical communication, quantum key distribution and precise spectral measurement.

[0070] Embodiment 3

[0071] A high-speed tunable wavelength narrow linewidth external cavity laser, comprising:

[0072] InP gain chip optical waveguide 1, emitting wavelength 1530-1630 nm, left end face coated with optical high reflection film 12, right end face coated with first optical antireflection film 13; the bottom of the InP gain chip optical waveguide 1 is provided with InP substrate 11;

[0073] Further comprising lithium niobate waveguide 2, length L wg =2cm, period Λ=225nm, the left end face of the lithium niobate waveguide 2 is coated with a second optical antireflection film 21, and the right end face of the lithium niobate waveguide 2 is coated with a third optical antireflection film 22; the upper end face of the lithium niobate waveguide 2 is provided with a lithium niobate thin film Bragg grating waveguide 25, the lithium niobate thin film Bragg grating waveguide 25 is provided below with a SiO2 layer 24, and the SiO2 layer 24 is provided below with a Si substrate 23;

[0074] The right end face of the InP gain chip optical waveguide 1 is aligned and attached to the left end face of the lithium niobate waveguide 2, forming an external cavity structure, and the total length of the external cavity is L cavity =L wg +L chip (L chip =500-1000 μm);

[0075] The upper end face of the lithium niobate waveguide 2 is further provided with a voltage control unit 3, the voltage control unit 3 comprises a metal electrode +31 and a metal electrode -32, and the metal electrode +31 and the metal electrode -32 are sequentially arranged on the front and back sides of the lithium niobate thin film Bragg grating waveguide 25;

[0076] Further, the lithium niobate thin film Bragg grating waveguide 25 is in a ridge structure, with a width of 4 μm and a height of 3 μm;

[0077] Further, the optical high-reflection film 12 side of the InP gain chip optical waveguide 1 is provided with a back light electric detector chip 33, and the back light electric detector chip 33 is connected with a PID feedback module; the back light electric detector chip 33 controlled by PID collects the feedback signal of the output voltage in real time, compares it with the set target value to generate an error signal, quickly responds to the error amplitude through the proportional (P) link, eliminates the steady-state deviation through the integral (I) link, predicts the voltage fluctuation trend through the differential (D) link, and comprehensively adjusts the control amount to make the output voltage stable at the target value; the metal electrode + 31, the metal electrode - 32 and the back light electric detector chip 33 controlled by PID are electrically connected to realize wavelength closed-loop control;

[0078] Further, the laser linewidth is ≤1 kHz, and the wavelength tuning range is 50 nm-100 nm;

[0079] The manufacturing method of the high-speed tunable wavelength narrow-linewidth external cavity laser, and the specific steps are as follows:

[0080] S1, a ridge waveguide on a lithium niobate waveguide 2 is made by a proton exchange method, Δn=0.05, and a Bragg grating is defined by electron beam lithography with a period accuracy of ±1 nm;

[0081] S2, Cr / Au electrodes are deposited on the lithium niobate waveguide 2 with a thickness of 200 nm;

[0082] S3, the InP gain chip optical waveguide 1 is aligned and attached to the lithium niobate waveguide 2 with an accuracy of ±1 μm, a TEC temperature control module is integrated, and the temperature stability is ±0.01℃;

[0083] Further, the high-speed tunable wavelength narrow-linewidth external cavity laser is applied in the fields of optical communication, quantum key distribution and precise spectral measurement.

[0084] The performance of the laser is tested:

[0085] Linewidth: 3dB linewidth of 1 kHz is measured by heterodyne interference method (traditional DFB is 100 kHz);

[0086] Tuning range: when the voltage is 0-10V, the wavelength is tuned from 1540nm to 1590nm (Δλ=50nm);

[0087] Power stability: the output power fluctuation is <0.1dB after continuous work for 24 hours.

[0088] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A high-speed tunable wavelength narrow linewidth external cavity laser, characterized in that, It comprises: The InP gain chip optical waveguide (1) has a left end face coated with an optical high-reflection film (12) and a right end face coated with a first optical anti-reflection film (13); the bottom of the InP gain chip optical waveguide (1) is provided with an InP substrate (11); Also included is a lithium niobate waveguide (2), length L wg =1-3cm, period Λ=220-230nm, the left end face of the lithium niobate waveguide (2) is coated with a second optical antireflection film (21), the right end face of the lithium niobate waveguide (2) is coated with a third optical antireflection film (22); the upper end face of the lithium niobate waveguide (2) is provided with a lithium niobate thin film Bragg grating waveguide (25), the lithium niobate thin film Bragg grating waveguide (25) is provided below with a SiO2 layer (24), the SiO2 layer (24) is provided below with a Si substrate (23); The right end surface of the InP gain chip optical waveguide (1) is aligned and attached to the left end surface of the lithium niobate waveguide (2), forming an external cavity structure, and the total length of the external cavity L cavity = L wg + L chip ; wherein L chip = 500-1000 μm; The upper end face of the lithium niobate waveguide (2) is further provided with a voltage control unit (3), the voltage control unit (3) comprises a metal electrode + (31) and a metal electrode - (32), the metal electrode + (31) and the metal electrode - (32) are arranged on the front and back sides of the lithium niobate thin film Bragg grating waveguide (25) in sequence; The lithium niobate waveguide (2) has a length L wg = 2 cm, a period A = 225 nm; The high-speed tunable wavelength narrow linewidth external cavity laser has a linewidth of less than 1 kHz and a wavelength tuning range of 50 nm-100 nm; The manufacturing method of the high-speed tunable wavelength narrow linewidth external cavity laser comprises the following specific steps: S1, a proton exchange method is used to manufacture a ridge waveguide on the lithium niobate waveguide (2), Δn=0.05, and an electron beam lithography is used to define a Bragg grating with a period accuracy of ±1 nm; S2, Cr / Au electrodes are evaporated on the lithium niobate waveguide (2) with a thickness of 200 nm; S3, the InP gain chip optical waveguide (1) is aligned and attached to the lithium niobate waveguide (2) with an accuracy of ±1 μm, a TEC temperature control module is integrated, and the temperature stability is ±0.01 ℃.

2. The high-speed tunable wavelength narrow linewidth external cavity laser of claim 1, wherein: The lithium niobate thin film Bragg grating waveguide (25) has a ridge structure with a width of 3-5 μm and a height of 2-3 μm.

3. The high-speed tunable wavelength narrow-linewidth external cavity laser of claim 2, wherein: The lithium niobate thin film Bragg grating waveguide (25) has a ridge structure with a width of 4 μm and a height of 3 μm.

4. The high-speed tunable wavelength narrow-linewidth external cavity laser of claim 3, wherein: The InP gain chip optical waveguide (1) is provided with a back light electric detector chip (33) on the side of the optical high-reflection film (12), and the back light electric detector chip (33) is connected with a PID feedback module.

5. The high-speed tunable wavelength narrow linewidth external cavity laser according to any one of claims 1-4 is applied in the fields of optical communication, quantum key distribution and precise spectrum measurement.

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