External cavity laser capable of being quickly tuned
By adopting lead zirconate titanate material and vernier microring resonator structure, rapid tuning of external cavity laser is achieved, solving the problems of slow tuning speed, high power consumption and poor stability in the existing technology, and realizing efficient and low-cost laser output.
Patent Information
- Application Number
- CN202510717233.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-30
- Publication Date
- 2025-09-26
AI Technical Summary
Existing tunable external cavity lasers are difficult to simultaneously meet the comprehensive requirements of high speed, large range, low power consumption and high stability. The tuning mechanism mostly relies on thermo-optical or carrier injection effects, which leads to complex thermal management and multi-chip coupling processes, limiting large-scale integration and commercial mass production.
Using lead zirconate titanate material and a vernier microring resonator structure, fast tuning is achieved through the electro-optical effect. Combined with the non-volatile characteristics and pre-calibration function of the lead zirconate titanate material, the process is simplified and stability is improved.
It achieves fast and wide range laser tuning, outputs high power and high side mode suppression ratio, has simple process, compact structure, low cost and high performance, is suitable for CMOS compatibility and has low loss.
Smart Images
Figure CN120709816A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the field of semiconductor lasers, in particular to a rapidly tunable external cavity laser. Background Art
[0002] When it comes to optical network upgrades, increasing the number of optical wavelengths in an optical communication system is one of the most effective and cost-effective ways to expand capacity. Wavelength division multiplexing (WDM) has proven to be the most successful technology for optical communication backbone networks over the past two decades and has been widely deployed in metropolitan area networks. Optical access networks are facing increasing demands for higher communication speeds and capacity. Among various optical access technology solutions, WDM-PON offers outstanding advantages, including high system communication capacity, high fiber utilization, long transmission distances, and low latency. It also facilitates the integration of optical access networks and wireless networks, improving network resource utilization. From the perspective of optical switching, tunable lasers are a key tool for enhancing network flexibility. In ROADM and OXC applications, they can leverage dynamic wavelength characteristics, allowing wavelengths to be added or removed from a network segment to dynamically configure network resources to meet service changes. They can also be used to achieve dynamic recovery from optical network failures, serve as network spare parts to reduce costs, and even be used to implement wavelength routing and optical packet switching.
[0003] Despite significant progress in related research, existing tunable external cavity lasers still struggle to simultaneously meet the combined requirements of high speed, wide range, low power consumption, and high stability. Their tuning mechanisms often rely on thermo-optical or carrier injection effects, which are limited by heat capacity or carrier recombination lifetime, making it difficult to break through the microsecond tuning bottleneck. To maintain wavelength stability and suppress mode transitions, continuous heating and complex temperature control are typically required, leading to a significant increase in power consumption and a burden on thermal management. Furthermore, the multi-chip coupling and packaging process of the gain chip and passive waveguide is complex and extremely sensitive to assembly accuracy, environmental vibration, and thermal drift, limiting large-scale integration and commercial mass production.
[0004] It can be seen that there is still a need to develop a new type of external cavity laser with compact structure, fast tuning response, low power consumption and stable mode to meet the urgent needs of future high-speed optical communications and integrated photonic systems. Summary of the Invention
[0005] In response to the problems existing in the background technology, the present invention proposes a rapidly tunable external cavity laser, which realizes rapid tuning of the output laser wavelength by utilizing the special properties of lead zirconate titanate material.
[0006] In the rapidly tunable external cavity laser proposed in the present invention, by adopting pre-calibrated lead zirconate titanate material and a vernier microring resonator structure, rapid and wide-range tuning can be achieved, and high-power and high side-mode suppression ratio laser output can be realized, with the advantages of simple process and compact structure.
[0007] The technical solution adopted in the present invention is:
[0008] The present invention comprises a first gain chip and a second lead zirconate titanate chip, wherein the second lead zirconate titanate chip comprises an end face coupler, a phase shifter, an optical switch structure and a vernier resonator structure;
[0009] The first gain chip is optically coupled to one end of the end coupler of the second lead zirconate titanate chip. The other end of the end coupler is connected to one end of the vernier resonator structure through a phase shifter and an optical switch structure. The other end of the vernier resonator structure is connected to the output waveguide, and the laser is output through the output waveguide.
[0010] Laser light is input into the second chip and passes through a phase-shift region. This phase-shift region adjusts the refractive index of the waveguide through the electro-optic effect of materials including, but not limited to, lead zirconate titanate, thereby adjusting the phase of the resulting optical resonator. After passing through the phase-shift region, the laser light enters an optical switch structure. The optical switch structure includes, but is not limited to, a series connection of direct couplers (DCs), adiabatic couplers (ADCs), and multi-mode interferometers (MMIs). For example, using a direct coupler (DC) as an example, metal electrodes are attached to both sides of the two optical waveguides connecting the two direct couplers (DCs). The refractive index of the waveguides is adjusted through the electro-optic effect of materials including, but not limited to, lead zirconate titanate, thereby changing the splitting ratio of the optical switch structure and adjusting the power of the output laser light. After passing through the optical switch structure, the laser light enters the vernier resonator structure.
[0011] The first gain chip generates an original light beam with multiple wavelengths, which is incident on the end coupler in sequence, then adjusted in wavelength by the phase shifter, and then transmitted and reflected by the optical switch structure. Part of the reflected light beam returns to the phase shifter, then returns to the first gain chip through the end coupler, reflects in the first gain chip, and then re-incident to the end coupler, and then continuously propagates back and forth between the first gain chip and the optical switch structure; the other part of the transmitted light beam is incident on the vernier resonator structure, which outputs the light beam at the resonant wavelength.
[0012] The first gain chip, the end face coupler, the phase shifter, the optical switch structure and the vernier resonator structure form the laser optical resonance for light beam propagation.
[0013] Each part in the second lead zirconate titanate chip adopts an optical waveguide structure, and the core layer in the optical waveguide structure adopts lead zirconate titanate material.
[0014] The electro-optic effect of the lead zirconate titanate material changes the waveguide refractive index through the Pockels Effect, thereby changing the phase of the laser optical resonator.
[0015] The first gain chip and the lead zirconate titanate second chip are end-face coupled and connected, and the end-face coupled connection adopts a structure including but not limited to a tapered gradient, and the laser output end of the lead zirconate titanate second chip adopts end-face coupling, vertical coupling, etc.
[0016] The optical waveguide structure includes a first silicon substrate and a waveguide lower cladding layer of silica, a core ridge waveguide and a waveguide upper cladding layer of silica stacked on the first silicon substrate from bottom to top, wherein the waveguide upper cladding layer is coated on the core ridge waveguide; the core ridge waveguide is made of lead zirconate titanate material.
[0017] A metal electrode is further arranged on the core ridge waveguide, and the waveguide upper cladding layer covers the core ridge waveguide and the metal electrode.
[0018] The end face coupler adopts but is not limited to a tapered gradient structure;
[0019] The phase shifter adopts a straight waveguide structure;
[0020] The optical switch structure is realized by, but not limited to, using a direct coupler (DC), an adiabatic coupler (ADC), a multi-mode interferometer (MMI) and the like in series;
[0021] The vernier resonator structure adopts but is not limited to cascaded microring resonators, sampled gratings and other structures.
[0022] The vernier resonator structure includes but is not limited to being formed by cascading two microrings with different FSRs, thereby achieving a larger FSR effect through the vernier effect, and then combining the tuning of the phase shift region and the electrodes of the vernier microresonator structure region to achieve high-speed and large-range tuning.
[0023] The present invention has the following beneficial effects:
[0024] The present invention combines the strong electro-optical effect of lead zirconate titanate material to achieve large-scale and high-speed laser tuning, and achieves high-quality, high-power, and narrow-linewidth output lasers through optimized end couplers and optical switch structures.
[0025] The present invention introduces lead zirconate titanate material and utilizes its non-volatile characteristics to achieve pre-calibration of the microring resonator structure, which has the advantage of large process tolerance.
[0026] The present invention realizes a rapidly tunable external cavity laser structure, which can achieve rapid and wide-range tuning and realize high-power, high side mode suppression ratio laser output. It has the advantages of simple process and compact structure, and is CMOS compatible, low cost, high performance, low loss, and great potential. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 It is a structural schematic diagram of the present invention.
[0028] Figure 2 Schematic diagram of an optical waveguide and metal electrode with an asymmetric cross section according to the present invention.
[0029] Figure 3 This is a modulation curve diagram of the lead zirconate titanate material used in the present invention.
[0030] Figure 4 The graph is a graph showing the change in resonant wavelength of a microring resonator made of the lead zirconate titanate material used in the present invention as a function of voltage. DETAILED DESCRIPTION
[0031] The present invention will be further described below with reference to the accompanying drawings and examples.
[0032] like Figure 1 As shown, the external cavity laser includes a first gain chip 1a and a second lead zirconate titanate chip. The gain chip is a single-sided, strongly reflective SOA with an inclined emission angle. The second lead zirconate titanate chip includes an end coupler 1b, a phase shifter 1c, an optical switch structure 1d, and a vernier resonator structure 1e. The first gain chip 1a is optically coupled to one end of the end coupler 1b of the second lead zirconate titanate chip. The other end of the end coupler 1b is connected to one end of the vernier resonator structure 1e through the phase shifter 1c and the optical switch structure 1d. The other end of the vernier resonator structure 1d is connected to the output waveguide, through which the laser is output. The output waveguide serves as the laser output end of the second lead zirconate titanate chip.
[0033] The first gain chip 1a generates an original light beam with multiple wavelengths, which is incident on the second lead zirconate titanate chip in turn through the end coupler 1b. The wavelength is then adjusted by the phase shifter 1c, and then transmitted through the optical switch structure 1d. The transmitted light enters the vernier resonator structure 1e, and the resonant wavelength is reflected back to the optical switch structure 1d by the vernier resonator. It is then reflected back to the first gain chip 1a through the end coupler 1b, forming the optical FP cavity of the laser, and then competing to produce the laser lasing wavelength in the gain chip 1a.
[0034] The first gain chip 1a, the end coupler 1b, the phase shifter 1c, the optical switch structure 1d, and the vernier resonator structure 1e constitute a laser optical resonator for light beam propagation.
[0035] The phase shifter 1c adjusts the wavelength of the light beam passing through it by adjusting the refractive index of its own waveguide.
[0036] Each part of the end face coupler 1b, phase shifter 1c, optical switch structure 1d and vernier resonator structure 1e in the second lead zirconate titanate chip adopts an optical waveguide structure, and the core layer in the optical waveguide structure adopts lead zirconate titanate material.
[0037] In the present invention, lead zirconate titanate (PZT) material is prepared on a silicon dioxide (SiO2) / silicon (Si) substrate by a low-temperature Sol-Gel spin coating process, and has good crystal orientation, consistent film thickness control, and excellent electro-optical modulation performance.
[0038] Specifically, the lead zirconate titanate material is prepared by the following method:
[0039] S1. Spread the PZT precursor solution evenly on the substrate surface by spin coating and pre-bake on a hot plate at 250°C to remove organic components.
[0040] S2. Anneal the film to 450°C in an oxygen environment using a rapid thermal annealing (RTA) process and keep the temperature for one hour to form a perovskite phase structure with a high degree of crystallinity.
[0041] S3, repeating the above steps S1 and S2 to perform spin coating and annealing processes multiple times to reach the target film thickness, thereby preparing a lead zirconate titanate thin film.
[0042] The resulting lead zirconate titanate thin film exhibits low surface roughness and excellent thickness uniformity, which is beneficial for enhancing the electro-optical effect. The PZT thin film preparation process of the present invention has the capability of large-scale on-chip integration, facilitating integration with silicon photonic platforms or other photonic integration platforms, and has broad application prospects.
[0043] like Figure 3 As shown, the prepared lead zirconate titanate material has a strong electro-optical effect. It can be seen from the figure that the maximum modulation efficiency can reach about 100pm / V, which provides convenient conditions for high-speed tuning of external cavity lasers.
[0044] like Figure 4 As shown, the strong electro-optical effect of lead zirconate titanate material is also reflected in the FP resonant cavity made of it. It can be seen from the figure that after polarization, its resonance peak changes significantly with voltage, and the modulation efficiency is very high, which can achieve high-speed and large-scale resonance peak tuning. This can also be used in the micro-ring resonance peak structure described in the present invention to achieve large-scale tuning.
[0045] The refractive index of the waveguide is modified by the electro-optical properties of the lead zirconate titanate material, thereby changing the phase of the laser optical resonator. Specifically, its refractive index is adjusted through the electro-optic effect.
[0046] For the phase shifter, the phase of the laser optical resonator made of the first gain chip and the second lead zirconate titanate chip is adjusted.
[0047] The first gain chip and the second lead zirconate titanate chip are end-face coupled and connected. The end-face coupled connection adopts structures including but not limited to tapered gradient, and the laser output end of the second lead zirconate titanate chip adopts end-face coupling, vertical coupling, etc.
[0048] like Figure 2 As shown, the optical waveguide structure includes a first silicon substrate 102 and a waveguide lower cladding silica 100, a core ridge waveguide 101 and a waveguide upper cladding silica 100 stacked on the first silicon substrate 102 from bottom to top. The waveguide upper cladding 100 is coated on the core ridge waveguide 101 and the metal electrode 103; the core ridge waveguide 101 is made of lead zirconate titanate material.
[0049] A metal electrode 103 may be further disposed on the core ridge waveguide 101 , and the waveguide upper cladding layer 100 covers the core ridge waveguide 101 and the metal electrode 103 .
[0050] In the second lead zirconate titanate chip, except for the end face coupler 1b, the other phase shifters 1c, the optical switch structure 1d and the vernier resonator structure 1e all have metal electrodes, while the end face coupler 1b does not have a metal electrode.
[0051] In a specific implementation, the end face coupler 1b adopts but is not limited to a tapered structure; the phase shifter 1c adopts a straight waveguide structure; the optical switch structure 1d adopts but is not limited to a direct coupler DC, an adiabatic coupler ADC, a multi-mode interferometer MMI, etc. in series;
[0052] The vernier resonator structure 1d adopts but is not limited to cascaded microring resonators, sampled gratings, etc. Specifically, the cascaded resonator structure includes but is not limited to cascaded microrings or sampled gratings with different free spectral ranges.
[0053] The vernier resonator structure is implemented by two micro-rings or sampling grating structures with different free spectral ranges (FSRs), including but not limited to two. Specifically, the FSRs of the two micro-rings with different FSRs are FSR1 and FSR2, respectively. The FSR of the spectrum output through the vernier effect is FSR vernier , the specific calculation formula is as follows:
[0054]
[0055] Combining a vernier resonator structure, an optical switch structure, a phase shifter, and the high-speed electro-optical tuning of ferroelectric materials enables wide-range, high-speed laser tuning and high-power laser output. Laser light output from the vernier resonator structure can be transferred to subsequent devices through methods including, but not limited to, end-face coupling and vertical coupling.
[0056] The embodiments of the present invention and the comparative examples are as follows:
[0057] Example 1
[0058] This embodiment uses lead zirconate titanate (PZT) thin film as the external cavity tuning medium, integrates the gain chip with the vernier resonator structure, utilizes the high electro-optic coefficient of PZT to achieve large-scale rapid tuning, and utilizes low loss to achieve high power output.
[0059] Comparative Example 1 (Thermo-optical tuning structure)
[0060] In this comparative example, the tuning unit is replaced with a traditional Si3N4 waveguide-metal heater structure, where the tuning mechanism relies entirely on the thermo-optical effect. While it can cover a similar wavelength range, the switching speed is significantly slower due to thermal capacity limitations, and continuous power supply and heating are required to stabilize the wavelength, resulting in significantly increased power consumption and heat dissipation. In the event of a power outage or temperature control failure, the wavelength is prone to significant drift.
[0061] Comparative Example 2 (Thin Film Lithium Niobate Tuning Structure)
[0062] This comparative example uses a thin-film lithium niobate (TFLN) dual-ring filter, achieving electro-optical tuning via the Pockels effect. Limited by the electro-optic coefficient and device structure, the wavelength tunable range is narrow. While faster than thermo-optic solutions, the switching speed lags behind PZT solutions. Furthermore, a DC bias is required to maintain the operating point, leading to electrical drift and long-term stability issues. Furthermore, the high drive voltage increases the complexity of the peripheral drive and packaging.
[0063] Summary: Compared with the two comparative structures, the embodiment of the present invention achieves faster wavelength switching, lower continuous power consumption, a wider adjustable range and superior long-term stability by leveraging the efficient electro-optical tuning and non-volatile memory effect of PZT, fully demonstrating the comprehensive advantages of PZT-integrated external cavity lasers in high-speed reconfigurable optical networks and precision optical systems.
[0064] It can be seen from this implementation that the present invention achieves high output laser power and fast tuning speed while having high device integration and reducing device size and process complexity.
[0065] The above embodiments are used to illustrate the present invention rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.
Claims
1. A rapidly tunable external cavity laser, characterized in that: It comprises a first gain chip (1a) and a lead zirconate titanate second chip, wherein the lead zirconate titanate second chip comprises an end face coupler (1b), a phase shifter (1c), an optical switch structure (1d) and a vernier resonator structure (1e); The first gain chip (1a) is optically coupled to one end of an end coupler (1b) of a second lead zirconate titanate chip, the other end of the end coupler (1b) is sequentially connected to one end of a vernier resonator structure (1e) via a phase shifter (1c) and an optical switch structure (1d), and the other end of the vernier resonator structure (1d) is connected to an output waveguide, and laser light is outputted through the output waveguide.
2. The rapidly tunable external cavity laser according to claim 1, characterized in that: An original light beam with multiple wavelengths is generated in the first gain chip (1a), incident on the end coupler (1b) in sequence, then adjusted in wavelength by the phase shifter (1c), and then transmitted and reflected by the optical switch structure (1d). A portion of the reflected light beam returns to the phase shifter (1c), then returns to the first gain chip (1a) through the end coupler (1b), is reflected in the first gain chip (1a), and then re-incident on the end coupler (1b), thereby continuously propagating back and forth between the first gain chip (1a) and the optical switch structure (1d); another portion of the transmitted light beam is incident on the vernier resonator structure (1e), and the vernier resonator structure (1e) outputs a light beam at the resonant wavelength.
3. The rapidly tunable external cavity laser according to claim 1, characterized in that: The first gain chip (1a), the end face coupler (1b), the phase shifter (1c), the optical switch structure (1d), and the vernier resonator structure (1e) form a laser optical resonance for light beam propagation.
4. The rapidly tunable external cavity laser according to claim 1, characterized in that: Each part in the second lead zirconate titanate chip adopts an optical waveguide structure, and the core layer in the optical waveguide structure adopts lead zirconate titanate material.
5. The rapidly tunable external cavity laser according to claim 4, characterized in that: The electro-optic effect of lead zirconate titanate material is used to change the waveguide refractive index, thereby changing the phase of the laser optical resonator.
6. The rapidly tunable external cavity laser according to claim 1, characterized in that: The first gain chip and the lead zirconate titanate second chip are end-face coupled and connected, and the end-face coupled connection adopts a structure including but not limited to a tapered gradient, and the laser output end of the lead zirconate titanate second chip adopts end-face coupling, vertical coupling, etc.
7. The rapidly tunable external cavity laser according to claim 1, characterized in that: The optical waveguide structure comprises a first silicon substrate (102) and a waveguide lower cladding silicon dioxide (100), a core ridge waveguide (101) and a waveguide upper cladding silicon dioxide (100) stacked sequentially on the first silicon substrate (102) from bottom to top, wherein the waveguide upper cladding (100) is coated on the core ridge waveguide (101); the core ridge waveguide (101) is made of lead zirconate titanate material.
8. The rapidly tunable external cavity laser according to claim 1, characterized in that: A metal electrode (103) is further provided on the core ridge waveguide (101), and a waveguide upper cladding layer (100) covers the core ridge waveguide (101) and the metal electrode (103).
9. The rapidly tunable external cavity laser according to claim 1, characterized in that: The end face coupler (1b) adopts but is not limited to a tapered gradient structure; The phase shifter (1c) adopts a straight waveguide structure; The optical switch structure (1d) is realized by, but not limited to, using a direct coupler (DC), an adiabatic coupler (ADC), a multi-mode interferometer (MMI) and the like in series; The vernier resonator structure (1d) adopts but is not limited to structures such as cascaded microring resonators and sampled gratings.