Adjustable wavelength external cavity laser based on metal grating PZT film

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a wavelength-adjustable external cavity laser based on a metal grating PZT film, which comprises a laser gain chip. The PZT thin film optical waveguide is arranged on the left side of the laser gain chip and abuts against the left end face of the laser gain chip; the HR high reflection film is plated on the left end face of the PZT thin film optical waveguide; the AR anti-reflection film is plated on the right end surface of the laser gain chip; the TEC temperature control module is arranged at the bottom of the laser gain chip and the PZT thin film optical waveguide; the PZT thin film optical waveguide comprises a Si substrate, a SiO2 bottom layer is arranged on the upper end face of the Si substrate, a PZT thin film is arranged in the middle of the upper end face of the SiO2 bottom layer, a metal grating is etched on the upper end face of the PZT thin film, a SiO2 wrapping layer is arranged on the metal grating, a positive electrode is plated on the upper end face of the SiO2 wrapping layer, and a negative electrode is plated on the lower end face of the Si substrate. The invention has the following beneficial effects: 1, the advantages of the PZT film optical waveguide; and 2, the end face of the light path is jointed and linked.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, specifically to a tunable wavelength external cavity laser based on a metal grating PZT thin film. Background Technology

[0002] The 1550nm band has become a core band in optical communication and high-end detection fields due to its low fiber transmission loss and strong resistance to electromagnetic interference. Currently, 1550nm tunable lasers face the following technical bottlenecks, hindering their performance improvement and large-scale application:

[0003] 1. The 1550nm laser gain layer requires extremely high substrate lattice matching. The lattice mismatch between GaAs substrates and InGaAsP exceeds 3%, resulting in a reduction of carrier recombination efficiency by more than 25% and optical absorption loss ≥0.8dB / mm, which cannot meet the high-performance requirements. In contrast, the lattice matching between InP substrates and InGaAsP is ≤0.1%, making it the only suitable substrate for this band. However, existing lasers based on InP substrates mostly adopt a cavity distributed feedback (DFB) sandwich grating structure, requiring photolithography accuracy of ±5nm and etching depth error ≤10nm, resulting in extremely high process complexity and a yield generally below 50%.

[0004] 2. Traditional external cavity optical systems consist of multiple components such as mirrors and lenses, making optical path alignment difficult, reducing resistance to vibration interference, and resulting in coupling losses between components ≥3dB. Furthermore, existing lasers mostly use lithium niobate as the piezoelectric control material, with a piezoelectric coefficient of only 20-30pC / N. The cost per square centimeter is approximately 8-10 times that of lead zirconate titanate (PZT) films, and it exhibits strong temperature sensitivity; for every 10°C change in temperature, the 1550nm wavelength shifts by 0.3-0.5nm, making its stability far from meeting the requirements of high-precision applications.

[0005] 3. In some technologies, the connection between gratings, optical waveguides and gain chips often relies on complex coupling components, which not only increases the size of the device, but also leads to increased optical loss.

[0006] In optical module applications, lithium niobate and lead zirconate titanate (PZT) films each have their own characteristics. The advantages of lithium niobate and PZT films are as follows:

[0007] 1. PZT thin films exhibit significant advantages in electro-optic coefficients, with a Pockels coefficient exceeding 100 pm / V, more than three times that of thin-film lithium niobate. This means that at the same voltage, PZT thin films can achieve more efficient optical modulation, reducing the driving voltage and improving modulation efficiency. For example, the modulation efficiency of the fabricated Mach-Zehnder electro-optic modulator reaches 1.3 V·cm, and the modulation efficiency of the micro-ring modulator is 0.56 V·cm. In contrast, the electro-optic coefficient of lithium niobate is relatively low; for example, the electro-optic coefficient of ordinary lithium niobate is r0. 33With a modulation efficiency of approximately 31 pm / V, thin-film lithium niobate still falls short of PZT thin film in improving modulation efficiency. In optical module applications that pursue high-speed, low-energy-consumption optical modulation, PZT thin film has a greater advantage.

[0008] 2. PZT thin films have significant advantages in cost and fabrication process. Their film formation process is simple, allowing for the deposition and growth of large-size, high-quality crystalline thin films on silicon oxide through methods such as chemical liquid phase deposition or magnetron sputtering. They also offer strong CMOS compatibility, facilitating low-cost, large-scale production. In contrast, lithium niobate, especially thin-film lithium niobate, has a complex fabrication technology. The "smart cutting" technology for thin-film lithium niobate requires high-energy ion implantation to form a "pre-cut layer," demanding extremely high energy precision. Subsequent precise annealing is also necessary to repair lattice damage, resulting in substantial equipment investment and high costs, limiting its large-scale application. PZT thin films are more competitive in the cost-sensitive optical module market.

[0009] 3. Lithium niobate (LNiO) exhibits excellent performance in terms of optical loss and integration compatibility. The LNiO single-crystal thin-film structure reduces light propagation loss, making it suitable for high-performance optoelectronic devices. It can also be integrated with silicon-based optoelectronic devices via bonding technology. Compared to silicon and indium phosphide modulators, thin-film LNiO modulators offer the advantage of low insertion loss. While PZT thin films are not definitively inferior to LNiO in terms of optical loss, their integration compatibility is currently less mature. In optical module applications with stringent optical loss requirements and high integration demands, LNiO has a greater advantage.

[0010] 4. Lithium niobate has a higher level of application maturity. Due to its excellent properties, lithium niobate crystals have long been a core material for photonic chips, widely used in high-speed electro-optic modulators, integrated optics, and quantum optics. Thin-film lithium niobate has also been used in products such as 800G optical modules. For example, Jinan Jingzheng launched an 8-inch optical-grade lithium niobate thin film, which New Easun applied to its 800Gbps optical module. PZT thin film is relatively new in optical module applications. Although it has great potential, its market application scope and maturity are not as high as lithium niobate. In the optical module market, which prioritizes technological maturity and stability, lithium niobate is initially more widely accepted. However, with the development of PZT thin film technology, its applications are expected to gradually expand.

[0011] In summary, PZT thin films have great potential and advantages, especially in scenarios with high requirements for cost and modulation efficiency; while lithium niobate is more favored in scenarios that pursue low optical loss and mature applications.

[0012] Therefore, if the optical path end face of the metal grating, PZT thin film waveguide and InP gain chip can be bonded together, the coupling loss can be greatly reduced and the laser output efficiency can be improved. Summary of the Invention

[0013] This invention provides a tunable wavelength external cavity laser based on a metal grating PZT thin film to solve the problems mentioned in the background art.

[0014] A tunable wavelength external cavity laser based on a metal grating PZT thin film, comprising:

[0015] Laser gain chip;

[0016] A PZT thin-film optical waveguide is disposed on the left side of the laser gain chip and abuts against the left end face of the laser gain chip;

[0017] A high-reflectivity HR film is deposited on the left end face of the PZT thin-film optical waveguide;

[0018] An AR anti-reflective film is deposited on the right end face of the laser gain chip;

[0019] The TEC temperature control module is located at the bottom of the laser gain chip and the PZT thin film optical waveguide;

[0020] The PZT thin-film optical waveguide includes a Si substrate, a SiO2 underlayer disposed on the upper surface of the Si substrate, a PZT thin film disposed in the middle of the upper surface of the SiO2 underlayer, a metal grating etched on the upper surface of the PZT thin film, a SiO2 cladding disposed on the metal grating, a positive electrode deposited on the rear part of the upper surface of the SiO2 underlayer, and a negative electrode deposited on the front part of the upper surface of the SiO2 underlayer.

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

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

[0023] As a preferred embodiment of the above technical solution, the laser gain chip is an n-type InP single crystal wafer, cut into a substrate with a thickness of 100-150μm.

[0024] As a preferred embodiment of the above technical solution, the laser gain chip is an n-type InP single crystal wafer, cut into a 120μm thick substrate.

[0025] As a preferred embodiment of the above technical solution, the reflectivity of the HR high-reflectivity film is ≥95%.

[0026] As a preferred embodiment of the above technical solution, the reflectivity of the AR anti-reflection film is ≤0.08%.

[0027] This invention provides a tunable wavelength external cavity laser based on a metal grating PZT thin film, which has the following advantages:

[0028] 1. Advantages of PZT thin film optical waveguides

[0029] Ultra-high piezoelectric coefficient, superior tuning precision: The piezoelectric coefficient of PZT thin film is 250-550 pC / N, which is 8-18 times that of lithium niobate. Under 80V driving voltage, PZT thin film optical waveguide can generate an elongation of 3-5μm, enabling grating period fine-tuning precision to reach the 0.05nm level, ensuring linewidth fluctuation ≤0.5KHz when tuning at 1550nm wavelength, providing stable guarantee for ultra-narrow linewidth output.

[0030] Temperature sensitivity is controllable, and the superposition tuning range is wider: the temperature change rate of the refractive index of PZT thin films is 8×10⁻⁶. -6 / ℃, for every 10℃ change in temperature, the wavelength shift at 1550nm is only 0.1-0.2nm, while that of lithium niobate is 0.3-0.5nm. With TEC temperature control, the drift can be further controlled to within 0.06nm.

[0031] Superimposed tuning capability: Achieves basic tuning of 1550nm±15nm under 0-120V voltage drive, and with temperature fine-tuning of 20℃-40℃, the tuning range is further extended by ±3nm, with a total tuning range of 1550nm±18nm, meeting the needs of multi-channel optical communication.

[0032] Low cost and suitable for mass production: The raw material cost of PZT thin film is about 1 / 10 of that of lithium niobate, and the equipment investment of the radio frequency magnetron sputtering preparation process is only 1 / 6 of that of lithium niobate single crystal growth equipment; in InP substrate-based lasers, the cost of PZT thin film optical waveguide accounts for ≤4%, and the overall device cost is reduced by 45%-55%, making it suitable for large-scale mass production.

[0033] 2. Advantages of optical path end face bonding connection

[0034] Low coupling loss and high output efficiency: The laser gain chip is bonded to the optical path end face of the PZT thin film waveguide, with a light matching accuracy of ±1μm, coupling loss ≤0.5dB, and laser output efficiency improved by ≥25%, while avoiding the increase in size and cost of traditional coupling components.

[0035] Compact structure and strong anti-interference: The integrated end-face bonding structure eliminates the need for external cavity components such as reflectors and lenses, reducing the overall device size by 40% compared to traditional external cavity structures; and under vibration environments of 10-500Hz, the wavelength fluctuation is ≤0.03nm, with better stability than traditional external cavity structures, making it suitable for complex application scenarios.

[0036] Sufficient filtering and easy achievement of ultra-narrow linewidth: The length of PZT thin film optical waveguide is 10-50mm, which is much larger than the internal cavity DFB grating ≤5mm. The light absorption rate is ≤0.01dB / mm, which can effectively filter out stray light and redundant modes, break through the 100KHz linewidth limitation of internal cavity DFB, and achieve ultra-narrow linewidth output below 3KHz. The minimum linewidth can reach 1.2KHz. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of the present invention;

[0038] Figure 2 This is a left view of the PZT thin-film optical waveguide in this invention;

[0039] Figure 3 This is a top view showing the positional relationship between the laser gain chip and the PZT thin-film optical waveguide in this invention.

[0040] In the figure: 1. Laser gain chip; 2. PZT thin film optical waveguide; 21. Si substrate; 22. SiO2 bottom layer; 23. PZT thin film; 24. Metal grating; 25. SiO2 cladding; 26. Positive electrode; 27. Negative electrode; 3. HR high reflectivity film; 4. AR antireflective film; 5. TEC temperature control module. Detailed Implementation

[0041] 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.

[0042] Example 1

[0043] A tunable wavelength external cavity laser based on a metal grating PZT thin film, comprising:

[0044] Laser gain chip 1 is made of n-type InP single crystal wafer, cut into a 100μm thick substrate. An InGaAsP quantum well gain layer is grown on the substrate using MOCVD or MBE technology, with a well width of 7nm, a barrier width of 14nm, and a period of 8 layers. The emission wavelength of the laser gain chip is 1530nm.

[0045] The PZT thin-film optical waveguide 2 is disposed on the left side of the laser gain chip 1 and abuts against the left end face of the laser gain chip 1.

[0046] HR high reflectivity film 3 is deposited on the left end face of the PZT thin film optical waveguide 2, and the reflectivity of the HR high reflectivity film 3 is ≥95%.

[0047] An AR anti-reflective film 4 is deposited on the right end face of the laser gain chip 1. The reflectivity of the AR anti-reflective film 4 is ≤0.08%, which reduces end face reflection loss.

[0048] The TEC temperature control module 5 is located at the bottom of the laser gain chip 1 and the PZT thin film optical waveguide 2. It is attached to the bottom surface of the PZT thin film optical waveguide 2 with thermal grease. The cooling power is ≥5W. It works with the PID temperature control algorithm to achieve temperature control with an accuracy of ±0.05℃, which is used to compensate for the temperature sensitivity of the PZT thin film optical waveguide 2.

[0049] The PZT thin film optical waveguide 2 includes a Si substrate 21, a SiO2 underlayer 22 disposed on the upper surface of the Si substrate 21, a PZT thin film 23 disposed in the middle of the upper surface of the SiO2 underlayer 22, a metal grating 24 etched on the upper surface of the PZT thin film 23, a SiO2 cladding layer 25 disposed on the metal grating 24, a positive electrode 26 deposited on the rear part of the upper surface of the SiO2 underlayer 22, and a negative electrode 27 deposited on the front part of the upper surface of the SiO2 underlayer 22.

[0050] Example 2

[0051] A tunable wavelength external cavity laser based on a metal grating PZT thin film, comprising:

[0052] Laser gain chip 1 is made of n-type InP single crystal wafer, cut into a 120μm thick substrate. An InGaAsP quantum well gain layer is grown on the substrate using MOCVD or MBE technology, with a well width of 8nm, a barrier width of 15nm, and a period of 10 layers. The emission wavelength of the laser gain chip is 1550nm.

[0053] The PZT thin-film optical waveguide 2 is disposed on the left side of the laser gain chip 1 and abuts against the left end face of the laser gain chip 1.

[0054] The HR high-reflectivity film 3 is deposited on the left end face of the PZT thin film optical waveguide 2.

[0055] An AR anti-reflective film 4 is deposited on the right end face of the laser gain chip 1. The reflectivity of the AR anti-reflective film 4 is ≤0.08%, which reduces end face reflection loss.

[0056] The TEC temperature control module 5 is located at the bottom of the laser gain chip 1 and the PZT thin film optical waveguide 2. It is attached to the bottom surface of the PZT thin film optical waveguide 2 with thermal grease. The cooling power is ≥5W. It works with the PID temperature control algorithm to achieve temperature control with an accuracy of ±0.05℃, which is used to compensate for the temperature sensitivity of the PZT thin film optical waveguide 2.

[0057] The PZT thin film optical waveguide 2 includes a Si substrate 21, a SiO2 underlayer 22 disposed on the upper surface of the Si substrate 21, a PZT thin film 23 disposed in the middle of the upper surface of the SiO2 underlayer 22, a metal grating 24 etched on the upper surface of the PZT thin film 23, a SiO2 cladding layer 25 disposed on the metal grating 24, a positive electrode 26 deposited on the rear part of the upper surface of the SiO2 underlayer 22, and a negative electrode 27 deposited on the front part of the upper surface of the SiO2 underlayer 22.

[0058] Example 3

[0059] A tunable wavelength external cavity laser based on a metal grating PZT thin film, comprising:

[0060] Laser gain chip 1 is made of n-type InP single crystal wafer, cut into a 150μm thick substrate. An InGaAsP quantum well gain layer is grown on the substrate using MOCVD or MBE technology, with a well width of 9nm, a barrier width of 16nm, and a period of 12 layers. The emission wavelength of the laser gain chip is 1610nm.

[0061] The PZT thin-film optical waveguide 2 is disposed on the left side of the laser gain chip 1 and abuts against the left end face of the laser gain chip 1.

[0062] The HR high-reflectivity film 3 is deposited on the left end face of the PZT thin film optical waveguide 2.

[0063] An AR anti-reflective film 4 is deposited on the right end face of the laser gain chip 1. The reflectivity of the AR anti-reflective film 4 is ≤0.08%, which reduces end face reflection loss.

[0064] The TEC temperature control module 5 is located at the bottom of the laser gain chip 1 and the PZT thin film optical waveguide 2. It is attached to the bottom surface of the PZT thin film optical waveguide 2 with thermal grease. The cooling power is ≥5W. It works with the PID temperature control algorithm to achieve temperature control with an accuracy of ±0.05℃, which is used to compensate for the temperature sensitivity of the PZT thin film optical waveguide 2.

[0065] The PZT thin film optical waveguide 2 includes a Si substrate 21, a SiO2 underlayer 22 disposed on the upper surface of the Si substrate 21, a PZT thin film 23 disposed in the middle of the upper surface of the SiO2 underlayer 22, a metal grating 24 etched on the upper surface of the PZT thin film 23, a SiO2 cladding layer 25 disposed on the metal grating 24, a positive electrode 26 deposited on the rear part of the upper surface of the SiO2 underlayer 22, and a negative electrode 27 deposited on the front part of the upper surface of the SiO2 underlayer 22.

[0066] 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 tunable wavelength external cavity laser based on a metal grating PZT thin film, characterized in that: include, Laser gain chip (1); The PZT thin film optical waveguide (2) is disposed on the left side of the laser gain chip (1) and abuts against the left end face of the laser gain chip (1). HR high reflectivity film (3) is deposited on the left end face of the PZT thin film waveguide (2); AR anti-reflective film (4) is deposited on the right end face of the laser gain chip (1); The TEC temperature control module (5) is located at the bottom of the laser gain chip (1) and the PZT thin film optical waveguide (2); The PZT thin film optical waveguide (2) includes a Si substrate (21), a SiO2 underlayer (22) is disposed on the upper surface of the Si substrate (21), a PZT thin film (23) is disposed in the middle of the upper surface of the SiO2 underlayer (22), a metal grating (24) is etched on the upper surface of the PZT thin film (23), a SiO2 cladding (25) is disposed on the metal grating (24), a positive electrode (26) is deposited on the rear part of the upper surface of the SiO2 underlayer (22), and a negative electrode (27) is deposited on the front part of the upper surface of the SiO2 underlayer (22).

2. The tunable wavelength external cavity laser based on a metal grating PZT thin film according to claim 1, characterized in that: The laser gain chip (1) emits wavelengths of 1530-1610nm.

3. A tunable wavelength external cavity laser based on a metal grating PZT thin film according to claim 2, characterized in that: The laser gain chip (1) emits at a wavelength of 1550nm.

4. A tunable wavelength external cavity laser based on a metal grating PZT thin film according to claim 1, characterized in that: The laser gain chip (1) is an n-type InP single crystal wafer, cut into a 100-150μm thick substrate.

5. A tunable wavelength external cavity laser based on a metal grating PZT thin film according to claim 4, characterized in that: The laser gain chip (1) is an n-type InP single crystal wafer, cut into a 120μm thick substrate.

6. A tunable wavelength external cavity laser based on a metal grating PZT thin film according to claim 1, characterized in that: The reflectivity of the HR high-reflectivity film (3) is ≥95%.

7. A tunable wavelength external cavity laser based on a metal grating PZT thin film according to claim 1, characterized in that: The reflectivity of the AR anti-reflective film (4) is ≤0.08%.

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