External cavity laser and apparatus

Abstract

The invention belongs to the field of lasers, and particularly discloses an external cavity laser and equipment, the external cavity laser comprises a gain chip, an external resonant cavity and a coupling module, the gain chip and the external resonant cavity are coupled through the coupling module, the external resonant cavity comprises a waveguide structure, an optical grating and a phase change material layer, and the optical grating is arranged on the waveguide structure. The grating is arranged on the waveguide structure, the phase change material layer is arranged on the surface of the grating in a stacked mode and comprises a plane portion and a protruding portion which are connected with each other, and the protruding portion is filled in a groove of the grating. Therefore, the external cavity laser can reduce the energy consumption while realizing the rapid tuning of the wavelength.

Description

Technical Field

[0001] The present application belongs to the field of lasers, and specifically relates to an external cavity laser and equipment. Background Art

[0002] With the expansion of the application of narrow linewidth lasers that can be quickly and continuously modulated, such as long-distance laser sensing, precise ranging, continuous wave tuning (FMCW) laser radar, optical atomic clocks, quantum technology, etc., the demand for lasers that can be quickly modulated is increasing. Compared with solid-state, optical fiber and other lasers, semiconductor lasers have a simple structure and a small size. Semiconductor lasers based on external cavities not only compress the linewidth but also have the function of tuning, and their application prospects are relatively broad. However, the coupling loss caused by the integration method between semiconductor devices may affect the speed of laser tuning. Therefore, how to reduce the coupling loss and thus improve the accuracy of external cavity lasers still needs further research. Summary of the invention

[0003] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present application proposes an external cavity laser and a device with fast wavelength tunability, low device loss or low power consumption.

[0004] In the first aspect of the present application, an external cavity laser is proposed, comprising a gain chip, an external resonant cavity and a coupling module, wherein the gain chip and the external resonant cavity are coupled and connected via the coupling module, wherein the external resonant cavity comprises a waveguide structure, a grating and a phase change material layer, wherein the grating is arranged on the waveguide structure, and the phase change material layer is stacked on the surface of the grating and comprises a planar portion and a convex portion connected to each other, and the convex portion is filled in the groove of the grating. Thus, the external cavity laser can tune the wavelength quickly and accurately, and has low power consumption and a wide range of applications.

[0005] In some embodiments, the phase change material includes germanium antimony selenide tellurium. Thus, fast and stable multi-level state tuning can be achieved, thereby improving the applicable range and accuracy of the external cavity laser.

[0006] In some embodiments, the grating includes a Bragg grating, thereby selecting the wavelength of the incident light, further compressing the line width, and then gaining light of a specific wavelength.

[0007] In some embodiments, the grating period of the grating is 350 nm to 359 nm, which is beneficial to reduce the loss of the grating and improve the effective refractive index of the grating.

[0008] In some embodiments, the duty cycle of the grating is 50%.

[0009] In some embodiments, the depth of the grating is 40 nm to 50 nm.

[0010] The grating parameters being within the above range are beneficial to improving the coupling coefficient of the grating and achieving the maximum Bragg reflectivity.

[0011] In some embodiments, the thickness of the planar portion is 10 nm to 15 nm, thereby making the phase change material deposited more uniformly, thereby achieving rapid wavelength tuning.

[0012] In some embodiments, the material of the waveguide structure includes SiN. This can enable the external cavity laser to have the ability to withstand high voltage, reduce the overall loss of the external cavity laser, and thus reduce the threshold voltage of laser emission.

[0013] In some embodiments, the thickness of the waveguide structure is 300 nm to 600 nm.

[0014] In some embodiments, the width of the waveguide structure is 800 nm to 1000 nm.

[0015] The thickness and width of the waveguide structure being within the above range is beneficial to improving the effective refractive index of the waveguide, thereby achieving rapid wavelength tuning.

[0016] In some embodiments, the coupling module includes a photon wire bonding structure, thereby reducing the mode profile mismatch between the gain chip and the waveguide, thereby reducing the loss caused by coupling, and further improving the wavelength tuning accuracy of the external cavity laser.

[0017] In some embodiments, the gain chip includes an active region, and the material of the active region includes InGaAsP, thereby absorbing and emitting light more efficiently.

[0018] The second aspect of the present application provides a device, comprising the external cavity laser described in the first aspect of the present application, thereby facilitating improving the overall operating efficiency of the device.

[0019] In some embodiments, the device includes at least one of an optical fiber sensor, an optical communication device, a laser radar, and a high-resolution spectrometer. Therefore, the external cavity laser has a wide range of uses and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a front view of a structural schematic diagram of an embodiment of the present application.

[0021] Figure 2 It is a top view of a structural schematic diagram of an embodiment of the present application.

[0022] Figure 3 It is a side view of a structural schematic diagram of an embodiment of the present application.

[0023] Figure 4 It is a partially enlarged view of the grating of an embodiment of the present application.

[0024] Figure 5 1 is a top view of a PWB photon wire bonding structure according to an embodiment of the present application.

[0025] Figure 6 It is a front view of a PWB photon wire bonding structure according to an embodiment of the present application.

[0026] Reference numerals:

[0027] 1-gain chip; 2-external resonant cavity; 3-coupling module; 4-waveguide structure; 5-grating; 6-phase change material layer; 7-indium phosphide substrate; 8-N-doped region; 9-active region; 10-P-doped region; 11-electrode; 12-high reflective coating; 13-anti-reflective mirror coating; 14-SiO2 substrate; 15-PWB; 16-first waveguide; 17-second waveguide. DETAILED DESCRIPTION

[0028] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, but cannot be understood as limiting the present application.

[0029] In a first aspect, the present application proposes an external cavity laser, referring to Figure 1 The external cavity laser comprises a gain chip 1, an external resonant cavity 2 and a coupling module 3, wherein the gain chip and the external resonant cavity are coupled and connected via the coupling module, wherein the external resonant cavity comprises a waveguide structure 4, a grating 5 and a phase change material layer 6, wherein the grating is arranged on the waveguide structure, and the phase change material layer is stacked on the surface of the grating and comprises a planar portion and a convex portion connected to each other, wherein the convex portion is filled in the groove of the grating (refer to Figure 4 ). In addition, the top view of the external cavity laser can be referred to Figure 2 , side view can refer to Figure 3 .

[0030] The present application integrates phase change material and grating together, and changes its phase state within nanoseconds by applying voltage to the phase change material. Since the effective refractive index of different phases of the phase change material is very different, the effective refractive index of the grating can be adjusted after integration with the grating. The reflection wavelength of the grating is directly related to the effective refractive index of the grating. Rapidly changing the effective refractive index of the phase change material is equivalent to rapidly changing the effective refractive index of the grating, so rapid wavelength tuning can be achieved. In terms of the setting of the phase change material, the present application fills the grating groove with phase change material and then covers it with a layer of phase change material to avoid the problem of uneven groove filling due to the deposition process, thereby further improving the stability and accuracy of the external cavity laser.

[0031] It should be noted that, refer to Figure 1 , the common gain chip mainly includes substrate 7, N-doped region 8, active region 9, P-doped region 10 and electrode 11. The specific selection of the gain chip is not limited and can be flexibly set according to specific needs. In the present application, the material of the active region is selected as indium gallium arsenic phosphide (InGaAsP). InGaAsP has the characteristics of a direct bandgap semiconductor, can effectively absorb and emit light, and it has a good lattice match with the indium phosphide (InP) substrate, which makes them conveniently integrated on the same platform to form a composite material structure. After a certain voltage is applied to the gain chip, the particle inversion will be realized in its internal active region, promoting the recombination of carriers and holes. In the process of recombination, energy is released in the form of photons. These photons will excite more photons during the resonance of the resonant cavity. When the gain can make up for the loss in the cavity, the laser can be emitted.

[0032] In some embodiments, the phase change material includes germanium antimony selenium tellurium (GSST). Among them, there are many types of phase change materials, and there are currently two mainstream ones: transition metal oxides and sulfur phase change materials. Due to the thermal sensitivity and volatility of transition metal oxides, this application selects non-volatile materials such as sulfur phase change materials to be combined with external cavity lasers. There are many types and quantities of sulfur phase change materials. The phase switching time, thermal expansion coefficient, crystallization temperature, melting temperature, refractive index of each phase, etc. between each material are different. It is a difficult problem to select a suitable material to ensure its stable and fast tuning of the laser wavelength. The phase change material GSST can achieve fast and stable multi-level state tuning due to its fast phase switching speed, large difference in refractive index between crystalline and amorphous states, high crystallization temperature, and small extinction coefficient between crystalline and amorphous states, making it possible for the laser to quickly and accurately tune the wavelength, and its non-volatility allows it to adapt to a variety of harsh environments without affecting the normal use of the laser, thereby improving the applicable range and accuracy of the external cavity laser.

[0033] In some embodiments, the grating includes a Bragg grating, which can be directly etched on the waveguide structure. Among them, the Bragg grating is a reflective grating, and its working principle is that the forward-transmitting guided mode and the reverse-transmitting guided mode generate energy coupling in the grating area to form a reflected wave of a specific wavelength. In the present application, the waveguide is made into a Bragg grating form to select the incident light, further compress the line width, and then gain the light of a specific wavelength.

[0034] In some embodiments, the grating period of the grating is 350nm to 359nm, for example, 350nm, 351nm, 352nm, 353nm, 354nm, 355nm, 356nm, 357nm, 358nm or 359nm. It can be understood that different wavelengths can be obtained by adjusting the grating period. If a wavelength of 1310nm is required, a grating period of 303nm is corresponding; if a wavelength of 1550nm is required, a grating period of 359nm is corresponding. This is conducive to reducing the loss of the grating and improving the effective refractive index of the grating.

[0035] In some embodiments, the duty cycle of the grating is 50%. The grating duty cycle refers to the ratio of the transparent area to the opaque area in the grating. In the process of making the grating, different grating duty cycles can be obtained by setting the width and spacing of the transparent area and the opaque area.

[0036] In some embodiments, the depth of the grating is 40 nm to 50 nm, for example, it can be 40 nm, 41 nm, 42 nm, 43 nm, 44 nm, 45 nm, 46 nm, 47 nm, 48 nm, 49 nm or 50 nm.

[0037] The grating parameters being within the above range are beneficial to improving the coupling coefficient of the grating and achieving the maximum Bragg reflectivity at a wavelength of 1550nm.

[0038] In some embodiments, the thickness of the planar portion is 10nm to 15nm, for example, 10nm, 11nm, 12nm, 13nm, 14nm or 15nm, etc. In the present application, after the phase change material is filled inside the groove of the grating, a layer of phase change material is deposited on the surface, and by applying a specific voltage, the phase change material is made to achieve rapid conversion between the amorphous state and the crystalline state, and the difference in refractive index and extinction coefficient between the crystalline state and the amorphous state is used to change the overall effective refractive index of the waveguide, so that the Bragg wavelength changes, thereby achieving rapid wavelength tuning.

[0039] In some embodiments, the material of the waveguide structure includes SiN. Due to its wide bandgap characteristics, the SiN waveguide has the ability to withstand high voltages, and its low loss characteristics can reduce the overall loss of the external cavity laser, thereby reducing the threshold voltage of laser emission.

[0040] In some embodiments, the thickness of the waveguide structure is 300 nm to 600 nm, for example, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm or 600 nm.

[0041] In some embodiments, the width of the waveguide structure is 800 nm to 1000 nm, for example, 800 nm, 850 nm, 900 nm, 950 nm or 1000 nm.

[0042] The thickness and width of the waveguide structure being within the above range is beneficial to improving the effective refractive index of the waveguide, thereby achieving rapid wavelength tuning.

[0043] In some embodiments, the coupling module includes a photon wire bonding structure. The specific structural diagram can be referred to Figure 5 and Figure 6 Among them, the photon wire bonding technology controls high-energy pulsed light beams to cause multi-photon polymerization of photoresist at specific locations to form three-dimensional polymer waveguides. These waveguides completely confine light inside to achieve efficient and low-loss transmission of optical signals between different photonic devices or chips.

[0044] The external cavity laser of the present application has at least the following beneficial effects:

[0045] 1. The wavelength tuning speed has been optimized: Thanks to the ns-level phase switching speed of the phase change material, the wavelength of the external cavity laser can be tuned in a very short time, making it applicable to occasions where fast tuning is required.

[0046] 2. Reduced device loss: Thanks to the use of SiN waveguide and GSST phase change material, the coupling loss and transmission loss of the device have been reduced to a certain extent, reducing the required threshold current and helping to achieve low power consumption.

[0047] 3. Lower power consumption: Compared with the traditional design of applying a large voltage on the waveguide to achieve wavelength tuning, the laser using phase change materials can achieve the change of material phase at a voltage of about 2V, saving energy.

[0048] The second aspect of the present application provides a device, comprising the external cavity laser described in the first aspect of the present application, thereby facilitating improving the overall operating efficiency of the device.

[0049] In some embodiments, the device includes at least one of an optical fiber sensor, an optical communication device, a laser radar, and a high-resolution spectrometer. Therefore, the external cavity laser has a wide range of uses and has broad application prospects.

[0050] Specifically, the external cavity laser can be used in the following fields:

[0051] 1. Grating sensing field:

[0052] Fiber optic sensors are easily affected by environmental noise and electromagnetic interference in practical applications, so higher requirements are placed on anti-interference. External cavity lasers can effectively suppress noise during measurement by adopting appropriate coupling and packaging technologies, thereby enhancing the anti-interference ability of fiber optic sensors. The phase change process of phase change materials can achieve wavelength tuning of the laser, thus improving the measurement accuracy of the sensor.

[0053] 2. High-speed optical communication field

[0054] With the growth of applications such as cloud computing, the Internet of Things, and video streaming, the demand for data transmission continues to rise. There are new requirements for the bandwidth of fiber-optic communication technology. External cavity lasers can achieve wavelength division multiplexing and improve bandwidth utilization by combining optical elements such as gratings. Phase change materials can solve the problem of limited spectrum resources by tuning wavelengths.

[0055] 3. LiDAR

[0056] LiDAR is a technology that uses laser beams to measure distance, and is widely used in autonomous driving, terrain mapping, construction, agriculture, and environmental monitoring. The FMCW mode in LiDAR usually uses a tunable laser as a light source to output a frequency-modulated optical signal, and the external cavity laser based on phase change materials can achieve ns-level fast tunability of wavelength through phase change materials to improve the three-dimensional recognition capability of LiDAR. In addition, fast tuning can improve the frequency response of the signal and reduce measurement delays, thereby improving the accuracy and performance of the system. This has a very broad application prospect in vehicle-mounted LiDAR.

[0057] 4. High-resolution spectroscopy

[0058] When performing high-resolution spectral analysis, background noise and environmental interference may cause signal distortion, so there are extremely high requirements for signal accuracy and reliability. The external cavity laser, due to its unique appearance design, helps to reduce the noise level and improve the clarity of the signal, thereby improving the quality of spectral data. Phase change materials can achieve the needs of high-resolution spectroscopy measurement in different wavelength ranges.

[0059] In summary, wavelength-tunable external cavity lasers combined with phase change materials have broad application prospects in multiple technical fields such as fiber optic sensing, high-speed optical communication, lidar, and high-resolution spectroscopy. With the continuous development and innovation of technology, these application fields will continue to expand and deepen.

[0060] Example 1

[0061] The external cavity laser is an improvement on the common laser (specifically, the ECDL-795). The external cavity laser includes a gain chip and an external resonant cavity. The gain chip and the external resonant cavity are connected by a coupling module (i.e., PWB photon wire bonding technology). The external resonant cavity is combined with the phase change material GSST. A Bragg grating (grating period 359nm, duty cycle 50%, etching depth 50nm) is directly etched on a SiN waveguide (thickness 600nm, width 1μm). GSST is filled in the grooves of the grating, and then a 15nm thick layer of GSST is covered on top. For the specific structural diagram, please refer to Figure 1 .

[0062] Comparative Example 1

[0063] Same as Example 1, except that there is no phase change material, and the specific model is ECDL-795.

[0064] The embodiment 1 (external cavity laser combined with phase change material) provided by the present application is compared with comparative example 1. The work done by the present application is to tune the effective refractive index of the grating so that its reflective wavelength changes. The addition of phase change material can improve the change speed and change stability. Specifically, the phase change material and the grating are integrated together, and the phase state is changed within the ns level by applying voltage to the phase change material. Because the effective refractive index between different phases of the phase change material is very different, the effective refractive index of the grating can be adjusted after integration with the grating. The reflection wavelength of the grating is directly related to the effective refractive index of the grating. Rapidly changing the effective refractive index of the phase change material is equivalent to rapidly changing the effective refractive index of the grating, so it can be used to achieve rapid wavelength tuning. However, for an ordinary grating without integrated phase change material, its effective refractive index will not be changed, so the reflected wavelength is fixed and cannot achieve wavelength tuning. Therefore, the external cavity laser combined with phase change material provided by the present application has a faster wavelength tuning capability, and the coupling and propagation losses of the laser are also smaller.

[0065] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0066] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. An external cavity laser, characterized in that: It includes a gain chip, an external resonant cavity and a coupling module, wherein the gain chip and the external resonant cavity are coupled and connected via the coupling module, wherein: The external resonant cavity comprises a waveguide structure, a grating and a phase change material layer, wherein the grating is arranged on the waveguide structure, the phase change material layer is stacked on the surface of the grating and comprises a planar portion and a convex portion connected to each other, and the convex portion is filled in the groove of the grating.

2. The external cavity laser according to claim 1, characterized in that: The phase change material includes germanium, antimony, selenium and tellurium.

3. The external cavity laser according to claim 1, characterized in that: The grating comprises a Bragg grating.

4. The external cavity laser according to claim 1, characterized in that: The grating satisfies at least one of the following conditions: The grating period of the grating is 350nm to 359nm; The duty cycle of the grating is 50%; The depth of the grating is 40nm-50nm.

5. The external cavity laser according to claim 1, characterized in that: The thickness of the planar portion is 10 nm to 15 nm.

6. The external cavity laser according to claim 1, characterized in that: The waveguide structure satisfies at least one of the following conditions: The material of the waveguide structure includes SiN; The thickness of the waveguide structure is 300nm to 600nm; The width of the waveguide structure is 800nm-1000nm.

7. The external cavity laser according to claim 1, characterized in that: The coupling module includes a photonic wire bonding structure.

8. The external cavity laser according to claim 1, characterized in that: The gain chip includes an active region, and the material of the active region includes indium gallium arsenic phosphide.

9. A device, characterized in that: An external cavity laser comprising any one of claims 1 to 8.

10. The device according to claim 9, characterized in that Includes at least one of a fiber optic sensor, an optical communication device, a laser radar, and a high-resolution spectrometer.

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