External cavity semiconductor laser and method for detecting mode hopping of a laser

Abstract

The application provides an external cavity semiconductor laser and a laser mode jump detection method, and relates to the technical field of lasers.The external cavity semiconductor laser comprises a laser output mechanism, a wavelength tuning mechanism and a mode jump detection mechanism.The laser output mechanism is used for generating zero-order diffraction light and first-order diffraction light.The wavelength tuning mechanism is used for adjusting the laser output mechanism under the driving of a driving voltage, so that the wavelength of the laser is tuned.The mode jump detection mechanism is used for separating a sampling light of a predetermined proportion from the zero-order diffraction light, determining the output power of the laser based on the sampling light, collecting the output power of the laser and the driving voltage in real time during the tuning process, determining the first derivative of the output power of the laser and the driving voltage according to the collected output power of the laser and the driving voltage, and determining whether a mode jump occurs according to the first derivative of the output power of the laser and the driving voltage.The external cavity semiconductor laser can realize real-time detection of the mode jump state.

Description

Technical Field

[0001] This application relates to the field of laser technology, and in particular to an external cavity semiconductor laser and a laser mode skipping detection method. Background Technology

[0002] Tunable grating external cavity lasers (GTECLs) are widely used in high-resolution spectroscopy, precision measurement, and coherent detection due to their outstanding advantages such as high spectral purity, wide wavelength coverage, compact structure, high conversion efficiency, single-mode output, low cost, and high reliability. However, in practical operation, GTECLs are prone to mode hopping when the wavelength is tuned or environmental conditions change. This mode hopping phenomenon typically manifests as discontinuous changes in output wavelength and output power. During laser operation, mode hopping directly affects the quality and stability of the output laser signal.

[0003] In existing technologies, mode hopping detection typically relies on external high-resolution wavelength meters, Fabry-Perot interferometers, or spectral analysis equipment. These solutions are complex and bulky, hindering the miniaturization and engineering applications of lasers. Summary of the Invention

[0004] In view of this, this application proposes an external cavity semiconductor laser and a laser mode hopping detection method.

[0005] In a first aspect, this application provides an external cavity semiconductor laser, comprising: a laser output mechanism, a wavelength tuning mechanism, and a mode hopping detection mechanism; The laser output mechanism is used to generate zero-order diffracted light as laser output light and to generate first-order diffracted light as external cavity feedback light. The wavelength tuning mechanism is used to adjust the laser output mechanism under the drive of the driving voltage, so as to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light; The mode hopping detection mechanism is used to separate a predetermined proportion of sample light from the zero-order diffracted light, determine the laser output power based on the sample light, collect the laser output power and driving voltage in real time during the tuning process, determine the first derivative of the laser output power and the driving voltage based on the real-time collected laser output power and driving voltage, and determine whether mode hopping has occurred based on the first derivative of the laser output power and the driving voltage.

[0006] In one embodiment, the laser output mechanism includes: a semiconductor laser diode, a collimating optical element, a diffraction grating, and a rotatable mirror; The semiconductor laser diode is used to output the initial beam; The collimating optical element is located in the output optical path of the semiconductor laser diode and is used to collimate the initial beam and output collimated light. The diffraction grating is located in the transmission optical path of the collimated light and is used to disperse the collimated light to output the zero-order diffracted light and the first-order diffracted light; The rotatable mirror is located on the transmission optical path of the first-order diffracted light, and is used to reflect the first-order diffracted light to the diffraction grating, and then reflect it back into the cavity of the semiconductor laser diode through the diffraction grating and the collimating optical element to form an external cavity resonance.

[0007] In one embodiment, the wavelength tuning mechanism includes: a piezoelectric tuning element; The piezoelectric tuning element is used to adjust the orientation of the rotatable mirror under the drive voltage.

[0008] In one embodiment, the mode-hopping detection mechanism includes: a beam splitting component, a photodetector, and a processing unit; The beam splitter is located in the transmission optical path of the zero-order diffracted light and is used to separate a predetermined proportion of sample light from the zero-order diffracted light and project the sample light onto the photodetector. The photodetector is used to receive the sampled light and convert the sampled light into a power electrical signal; The processing unit is connected to the photodetector and is used to determine the laser output power based on the power electrical signal, and to acquire the laser output power and driving voltage in real time during the tuning process. Based on the real-time acquired laser output power and driving voltage, the unit determines the first derivative of the laser output power with respect to the driving voltage, and determines whether mode hopping occurs based on the first derivative of the laser output power with respect to the driving voltage.

[0009] In one embodiment, the beam-splitting component is a beam splitter, a wedge-shaped glass plate, or a transparent optical element with a predetermined reflectivity.

[0010] In one embodiment, the processing unit is further configured to control the driving voltage to gradually increase from low to high in step values, and record the laser output power once every preset time or preset voltage to obtain corresponding data of the driving voltage and the laser output power.

[0011] In one embodiment, the processing unit is further configured to determine that mode hopping has occurred when the first derivative of the laser output power and the driving voltage is greater than a preset smoothing tuning threshold.

[0012] In one embodiment, the sampling ratio of the sampled light is 0.5% to 2% of the zero-order diffraction light power.

[0013] Secondly, this application also provides a laser mode hopping detection method, which is performed based on an external cavity semiconductor laser as described in the first aspect; the laser mode hopping detection method includes: Real-time acquisition of laser output power and drive voltage during the tuning process; The first derivative of the laser output power with respect to the driving voltage is determined based on the real-time acquired laser output power and driving voltage. Whether mode hopping occurs is determined based on the first derivative of the laser output power and the driving voltage.

[0014] In one embodiment, the method further includes: The driving voltage is controlled to increase gradually from low to high in step values, and the laser output power is recorded once every preset time or preset voltage to obtain the corresponding data of the driving voltage and the laser output power.

[0015] The external cavity semiconductor laser proposed in this application has the following advantages over related technologies: 1. The external cavity semiconductor laser of this application outputs zero-order and first-order diffracted light through a laser output mechanism. A wavelength tuning mechanism then tunes the laser wavelength. During tuning, a predetermined proportion of sampled light is separated from the zero-order diffracted light by a mode-hopping detection mechanism to determine the laser output power. The output power and driving voltage are collected in real-time during tuning, and mode hopping is determined by calculating their first derivatives. This eliminates the need for complex and bulky external wavelength detection equipment found in existing technologies. This solves the problem of existing solutions hindering laser miniaturization and engineering applications, achieving a simpler structure and lower cost. Furthermore, because the detection process only samples the zero-order diffracted light, it does not interfere with the external cavity mode selection mechanism formed by the first-order diffracted light, ensuring the laser's original linewidth and tuning performance. Simultaneously, by collecting the output power and driving voltage in real-time during tuning, mode-hopping signals can be captured promptly, enabling real-time detection and early warning of mode-hopping states, ultimately effectively improving the laser's operational stability.

[0016] 2. The laser output mechanism forms a stable external cavity resonant structure through the precise coordination of a semiconductor laser diode, collimating optical element, diffraction grating, and rotatable mirror. The semiconductor laser diode provides a stable initial beam, the collimating optical element ensures beam collimation to guarantee subsequent dispersion effects, the diffraction grating precisely disperses and separates the zero-order output light and the first-order feedback light, and the rotatable mirror realizes the closed-loop reflection of the first-order diffracted light. Together, they construct a highly efficient external cavity resonant structure. This not only continues the core advantages of Littman-Metcalf lasers—narrow linewidth, wide tuning range, and stable output optical axis—but also, due to the clear division of functions among the components and the compact optical path design, facilitates integration with a mode-hopping detection mechanism without adding extra system complexity, thus contributing to the miniaturization and engineering applications of lasers. At the same time, the closed-loop reflection path of the first-order diffracted light does not interfere with the transmission and sampling detection of the zero-order output light, ensuring the independence of output light quality and mode-hopping detection, further supporting the stability and reliability of laser operation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments or related technologies of this application, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of an external cavity semiconductor laser in one embodiment of this application; Figure 2 This is a schematic diagram of the curve of laser output power versus the first derivative of driving voltage when no mode hopping occurs in one embodiment of this application; Figure 3 This is a schematic diagram of the curve of laser output power versus the first derivative of driving voltage when mode hopping occurs in one embodiment of this application; Figure 4 A schematic diagram of the laser output power curve when no mode hopping occurs in one embodiment of this application; Figure 5 A schematic diagram of the laser output power curve when mode hopping occurs in one embodiment of this application; Figure 6 This is a flowchart illustrating a laser mode skipping detection method in one embodiment of this application.

[0019] Explanation of reference numerals in the attached figures: 10-Laser output mechanism, 11-Semiconductor laser diode, 12-Collimating optical element, 13-Diffraction grating, 14-Rotating mirror, 20-Wavelength tuning mechanism, 30-Mode skipping detection mechanism, 31-Beam splitting component, 32-Photodetector, 33-Processing unit. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] In some embodiments, such as Figure 1 As shown, this application provides an external cavity semiconductor laser, which includes a laser output mechanism 10, a wavelength tuning mechanism 20, and a mode hopping detection mechanism 30. It should be noted that the external cavity semiconductor laser of this application can be a modified Littman-Metcalf structure external cavity semiconductor laser.

[0022] The laser output mechanism 10 is used to generate zero-order diffracted light as the laser output light and first-order diffracted light as the external cavity feedback light. The laser output mechanism 10 can output collimated light, which is then dispersed by a diffraction grating 13. The grating decomposes the collimated light into diffracted light of different orders according to the principle of light diffraction. The zero-order diffracted light, due to its concentrated energy and stable propagation direction, is directly selected as the laser output light to meet the core requirements of high-resolution spectroscopy, precision measurement, and other applications. The first-order diffracted light, as the external cavity feedback light, is designed with a corresponding optical path structure to reflect back along the original optical path into the active cavity of the laser output mechanism 10, forming a stable external cavity resonant structure. This resonant mechanism is the core foundation for ensuring the laser's narrow linewidth and wide tuning range.

[0023] The wavelength tuning mechanism 20 is used to adjust the laser output mechanism 10 under the drive voltage, so as to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light. The wavelength tuning mechanism 20 uses the drive voltage as the control signal and achieves precise operation by receiving continuously adjustable or stepped electrical signals, thereby regulating the core optical parameters of the laser output mechanism 10.

[0024] In applications, the propagation path and phase conditions of the first-order diffracted light can be changed by adjusting the optical path length of the external cavity in the laser output mechanism 10, the incident angle of the diffraction grating, or the position of the mirror, causing the wavelength of the feedback light to shift continuously or discretely. The output wavelength of the external cavity semiconductor laser is determined by the resonance condition of the external cavity feedback light. When the wavelength of the feedback light changes, the oscillation mode of the laser will match the new resonance condition, ultimately achieving controllable tuning of the wavelength of the laser output light (zero-order diffracted light). This not only continues the advantage of the wide tuning range of Littman-Metcalf lasers, but also ensures precise and stable tuning response because the adjustment method directly affects the wavelength control of the external cavity feedback light. At the same time, it does not interfere with the transmission of the zero-order output light or the sampling work of the mode-hopping detection mechanism 30, ensuring the stability of the laser's linewidth and output optical axis during tuning, and meeting the requirements of high-resolution spectroscopy, precision measurement, and other scenarios for wavelength tunability and stable performance.

[0025] The mode-hopping detection mechanism 30 is used to separate a predetermined proportion of sample light from the zero-order diffracted light, determine the laser output power based on the sample light, and collect the laser output power and driving voltage in real time during the tuning process. It then determines the first derivative of the laser output power with respect to the driving voltage based on the real-time collected laser output power and driving voltage, and determines whether mode-hopping has occurred based on this first derivative. It should be noted that the sampling ratio of the sample light needs to balance the normal operating requirements of the laser's main output light with the required detection signal strength of the sample light, avoiding excessive loss of the main output light by the sample light or detection errors due to insufficient light intensity. The specific ratio can be selected according to actual needs. For example, the sampling ratio of the sample light can be 0.5% to 2% of the zero-order diffracted light power.

[0026] The mode-hopping detection mechanism 30 separates a sample light with a preset power ratio from the zero-order diffracted light output from the laser output mechanism 10 using an optical beam splitter. The detection mechanism then converts the separated sample light into a photoelectric signal, and through signal amplification, calibration, and other processing steps, calculates the actual output power of the laser based on the preset power ratio between the sample light and the zero-order diffracted light. During the dynamic process of wavelength tuning driven by the wavelength tuning mechanism 20, the mode-hopping detection mechanism 30 synchronously acquires the real-time output power data of the laser and the real-time driving voltage data of the wavelength tuning mechanism 20 at the same timestamp, ensuring the temporal consistency of the two sets of data. Subsequently, the detection mechanism performs numerical differentiation on the continuously acquired driving voltage-output power corresponding data sequence to obtain the real-time first-order derivative value of the laser output power as a function of the driving voltage. This first-order derivative value directly reflects the rate and trend of change of the output power with the adjustment of the driving voltage during the tuning process.

[0027] Based on the inherent characteristics of external cavity semiconductor laser tuning, such as Figure 2As shown, during normal, mode-skipping tuning, the first derivative value (dP / dV) exhibits a stable and continuous change. Figure 3 As shown, when a laser experiences mode hopping, the abrupt change in oscillation mode can trigger discontinuous changes in output power, such as sudden increases or decreases. This leads to significant steps, abrupt changes, sudden increases or decreases, or abnormal fluctuations in the first derivative value. The mode hopping detection mechanism 30 can accurately and in real-time determine whether mode hopping has occurred during laser tuning by identifying these abnormal changes in the first derivative, providing real-time monitoring and judgment criteria for the laser's wavelength tuning process. It should also be noted that in applications, mode hopping can also be determined by whether the laser output power exhibits a significant step-like jump (which can be determined by whether the change value per unit time exceeds a threshold). Figure 4 This is a schematic diagram of the laser output power curve when mode hopping does not occur; the laser output power changes relatively smoothly. Figure 5 This is a schematic diagram of the laser output power curve when mode hopping occurs. Figure 5 A clear step-like jump appeared in the middle.

[0028] The aforementioned external cavity semiconductor laser outputs zero-order and first-order diffracted light through the laser output mechanism 10. Wavelength tuning is then achieved using the wavelength tuning mechanism 20. During tuning, a predetermined proportion of sampled light is separated from the zero-order diffracted light by the mode-hopping detection mechanism 30 to determine the laser output power. The output power and driving voltage are collected in real-time during tuning, and mode hopping is determined by calculating their first derivatives. This eliminates the need for complex and bulky external wavelength detection equipment found in existing technologies. It solves the problem of existing solutions hindering laser miniaturization and engineering applications, achieving a simpler structure and lower cost. Furthermore, because the detection process only samples the zero-order diffracted light, it does not interfere with the external cavity mode selection mechanism composed of the first-order diffracted light, ensuring the laser's original linewidth and tuning performance. Simultaneously, by collecting the output power and driving voltage in real-time during tuning, mode-hopping signals can be captured promptly, enabling real-time detection and early warning of mode-hopping states, ultimately effectively improving the laser's operational stability.

[0029] In some embodiments, such as Figure 1 As shown, the laser output mechanism 10 includes: a semiconductor laser diode 11, a collimating optical element 12, a diffraction grating 13, and a rotatable mirror 14.

[0030] The semiconductor laser diode 11 is used to output the initial beam. The collimating optical element 12 is located in the output optical path of the semiconductor laser diode 11 and is used to collimate the initial beam and output collimated light. The diffraction grating 13 is located in the transmission optical path of the collimated light and is used to disperse the collimated light and output zero-order diffraction light and first-order diffraction light.

[0031] The semiconductor laser diode 11 is the core device for laser generation in the external cavity semiconductor laser. Based on the photoelectric conversion principle of stimulated emission, it generates and emits an initial beam with a certain spatial divergence angle and irregular beam propagation direction under electrical excitation. The collimating optical element 12 can be a special optical shaping element such as an aspherical collimating lens or lens group. It is precisely coaxially set in the output optical path of the semiconductor laser diode 11, matching the propagation path of the initial beam. It can focus and collimate the initial beam with divergent characteristics, cancel the spatial divergence trend of the beam, and output collimated light with consistent propagation direction, regular beam cross-section, and meeting the subsequent dispersion requirements. This provides an incident beam that meets the optical conditions for the precise dispersion of the subsequent diffraction grating 13.

[0032] The diffraction grating 13 is a dispersive optical element with a periodic grating scribe structure. It is arranged in the subsequent transmission optical path of the collimated light. After the collimated light is incident on the grating working surface of the diffraction grating 13 at a preset incident angle, it is dispersed based on the grating diffraction effect. The incident collimated light is separated according to its wavelength characteristics and emitted at different diffraction angles. The diffracted light propagating along the original incident light direction is the zero-order diffracted light, which serves as the final output light of the external cavity semiconductor laser. The first-order diffracted light emitted at a specific diffraction angle serves as the external cavity feedback light. It is transmitted in reverse along the original optical path to the active region of the semiconductor laser diode 11 to form optical feedback, providing key feedback light conditions for the resonant oscillation of the external cavity semiconductor laser.

[0033] The rotatable mirror 14 is located in the transmission optical path of the first-order diffracted light. It is used to reflect the first-order diffracted light to the diffraction grating 13, and then back to the cavity of the semiconductor laser diode 11 through the diffraction grating 13 and the collimating optical element 12 to form an external cavity resonance.

[0034] It is understood that the rotatable mirror 14 is a high-precision optical reflective element with a high-reflectivity coating. It is precisely positioned on the dedicated transmission optical path of the first-order diffracted light emitted from the diffraction grating 13, and the reflective surface forms a matching angle with the incident path of the first-order diffracted light, ensuring that the first-order diffracted light can be efficiently incident on the surface of the mirror. This mirror can directionally reflect the incident first-order diffracted light, reducing light energy loss by utilizing its high reflectivity, and reflecting the first-order diffracted light back to the working surface of the original diffraction grating 13 along a preset optical path. Furthermore, its rotatable characteristic allows for the indirect alteration of the geometric parameters of the feedback optical path by adjusting the reflection angle. The first-order diffracted light, reflected by the rotatable mirror 14, is re-injected into the diffraction grating 13. Based on the grating's reverse diffraction effect, it is re-integrated into a beam propagating along a specific path. This beam then propagates along the reverse optical path of the collimating optical element 12. At this point, the collimating optical element 12 plays a reverse propagation adaptation role, guiding the feedback beam precisely through its own optical channel to avoid optical path deviation. Finally, the feedback beam is reflected back into the cavity of the semiconductor laser diode 11. The feedback light oscillates back and forth in this external cavity and is continuously amplified, satisfying the phase matching and gain conditions of laser oscillation, ultimately enabling the laser to achieve stable external cavity resonant output.

[0035] In this embodiment, the laser output mechanism 10 forms a stable external cavity resonant structure through the precise cooperation of the semiconductor laser diode 11, the collimating optical element 12, the diffraction grating 13, and the rotatable mirror 14. The semiconductor laser diode 11 provides a stable initial beam, the collimating optical element 12 ensures the collimation of the beam to guarantee the subsequent dispersion effect, the diffraction grating 13 accurately disperses and separates the zero-order output light and the first-order feedback light, and the rotatable mirror 14 realizes the closed-loop reflection of the first-order diffracted light. Together, they construct a highly efficient external cavity resonance, which not only continues the core advantages of Littman-Metcalf lasers such as narrow linewidth, wide tuning range, and stable output optical axis, but also facilitates integration with the mode-hopping detection mechanism 30 due to the clear division of functions of each component and the compact optical path design, without adding extra system complexity, thus contributing to the miniaturization and engineering application of the laser. At the same time, the closed-loop reflection path of the first-order diffracted light does not interfere with the transmission and sampling detection of the zero-order output light, ensuring the independence of output light quality and mode-hopping detection, further supporting the stability and reliability of laser operation.

[0036] In some embodiments, the wavelength tuning mechanism 20 includes a piezoelectric tuning element. The piezoelectric tuning element is used to adjust the pose of the rotatable reflector 14 under the drive of a driving voltage.

[0037] Among them, the piezoelectric tuning element is made based on the principle of inverse piezoelectric effect and can be made of functional materials with high-precision electromechanical conversion characteristics such as piezoelectric ceramics and piezoelectric crystals.

[0038] In applications, one end of the piezoelectric tuning element is rigidly coupled to the mounting base or drive shaft of the rotatable reflector 14, while the other end is fixed to the optical platform of the laser, forming a stable and gapless transmission connection to ensure precise transmission of driving force. As a precision drive unit for electromechanical conversion, the piezoelectric tuning element can directly convert the externally input drive voltage into a proportional micromechanical deformation. This deformation features nanometer-level displacement resolution, fast response speed, no mechanical wear, and strong stability, enabling high-precision closed-loop control of the output deformation. Under the dynamic control of the driving voltage, the piezoelectric tuning element will produce controllable expansion or bending deformation. Through the rigid transmission structure, the rotatable mirror 14 will be driven to make small and precise position adjustments around its rotation axis within a preset angle range. The position change of the rotatable mirror 14 will directly adjust the optical path geometry parameters of the external cavity resonant system, so that the propagation phase and incident conditions of the first-order diffracted light reflected back to the diffraction grating 13 after reflection by the mirror will change. Ultimately, the range in which the resonant frequency of the external cavity matches the wavelength of the feedback light will shift. Combined with the dispersion characteristics of the diffraction grating 13, continuous and high-precision tuning of the laser output wavelength can be achieved.

[0039] In some embodiments, such as Figure 1 As shown, the mode hopping detection mechanism 30 includes: a beam splitter 31, a photodetector 32, and a processing unit 33.

[0040] The beam splitter 31 is located in the transmission optical path of the zero-order diffracted light and is used to separate a predetermined proportion of sampled light from the zero-order diffracted light and project the sampled light onto the photodetector 32. The beam splitter 31 can be a beam splitter, a wedge-shaped glass plate, or a transparent optical element with a predetermined reflectivity.

[0041] The photodetector 32 is used to receive the sampled light and convert it into a power electrical signal. The photodetector 32 can be a semiconductor photodetector element such as a photodiode or avalanche photodiode. The effective detection surface of the photodetector 32 is precisely aligned with the optical path of the sampled light projected by the beam splitter 31, and the size of the detection surface matches the spot size of the sampled light, enabling unobstructed and low-loss reception of the directional sampled light projected by the beam splitter 31. Based on the photoelectric effect, the photodetector 32 converts the light energy of the incident sampled light into an electrical signal that is linearly proportional to it; that is, it directly converts the optical signal reflecting the magnitude of the sampled light power into a corresponding power electrical signal. It should be noted that the power electrical signal can be a current signal or a voltage signal.

[0042] The processing unit 33 is connected to the photodetector 32 and is used to determine the laser output power based on the power electrical signal, and to acquire the laser output power and driving voltage in real time during the tuning process. Based on the real-time acquired laser output power and driving voltage, the first derivative of the laser output power and driving voltage is determined, and the first derivative of the laser output power and driving voltage is used to determine whether mode hopping occurs.

[0043] It is understood that the processing unit 33 can achieve a stable connection with the photodetector 32 through a wired communication interface, ensuring delay-free and low-distortion transmission of the power signal. The processing unit 33 can preprocess the power signal output by the photodetector 32, which may include signal filtering, signal amplification, and calibration conversion. During laser wavelength tuning, the processing unit 33 acquires the real-time output power data and real-time drive voltage data of the laser through a synchronous data acquisition channel, and ensures that the acquisition timestamps of the two data streams strictly correspond through a timing synchronization algorithm, avoiding subsequent calculation errors due to timing deviations.

[0044] Subsequently, the processing unit 33 utilizes its built-in numerical calculation algorithm to perform real-time first-order derivative calculations on the continuously acquired discrete data sequence of driving voltage and output power. Through difference calculation and smoothing of adjacent data points, the dynamic first-order derivative value of the output power as a function of the driving voltage is obtained. This value intuitively quantifies the rate and pattern of power change with voltage adjustment during the tuning process. Based on the resonant characteristics of the external cavity semiconductor laser, under normal tuning conditions, the output power and driving voltage exhibit a continuous linear or slowly varying relationship, corresponding to a stable first-order derivative value without significant fluctuations. However, when the laser experiences mode hopping, the abrupt change in the oscillation mode triggers a discontinuous jump in the output power, leading to sudden increases or decreases, abrupt changes, abnormal fluctuations, or extreme values ​​exceeding a preset threshold in the first-order derivative value. The processing unit 33 uses its built-in anomaly detection algorithm to monitor the change in the first-order derivative value in real time. When the above-mentioned abnormal characteristics are detected, it immediately determines that the laser has experienced mode hopping and can output corresponding alarm signals or feedback control signals, providing real-time decision-making basis for the closed-loop control of the laser's wavelength tuning and ensuring the stability and accuracy of the tuning process.

[0045] In some embodiments, the processing unit 33 is further configured to control the driving voltage to gradually increase from low to high in step values, and record the laser output power once every preset time or preset voltage to obtain corresponding data of driving voltage and laser output power.

[0046] For example, a power can be recorded every 0.1 or 0.2V (e.g., 0.1S) to obtain a voltage-power correspondence curve or data.

[0047] It is understood that the processing unit 33 can pre-configure a fixed voltage step value based on the target tuning wavelength range of the laser, the tuning accuracy requirements, and the response characteristics of the piezoelectric tuning element. Then, following the control logic of "low voltage start – gradual increase," it outputs continuous voltage control signals to the driving circuit, driving the piezoelectric tuning element's driving voltage from the initial low voltage state to a smooth and orderly gradual increase of the set step value. This ensures that the orientation of the rotatable reflector 14 is adjusted slowly, avoiding drastic fluctuations in the external cavity optical path due to sudden voltage changes. During the tuning process with the driving voltage gradually increasing, the processing unit 33 uses a built-in timing trigger module or voltage threshold trigger module to control data recording.

[0048] In applications, if a preset time trigger is used, data recording is automatically triggered once at a pre-set fixed time interval. If a preset voltage trigger is used, data recording is triggered whenever the driving voltage rises to a preset voltage node. The two triggering methods can be flexibly selected according to the actual application scenario to ensure the uniformity and effectiveness of data recording. Each time recording is triggered, the processing unit 33 synchronously collects the laser output power data calculated at the current moment and the corresponding real-time driving voltage data, associates and stores the two sets of data to form a complete data sequence corresponding to the driving voltage and laser output power.

[0049] In some embodiments, the processing unit 33 is further configured to determine that mode hopping has occurred when the first derivative of the laser output power and the driving voltage is greater than a preset smoothing tuning threshold.

[0050] For example, the smoothing threshold can be 0.1.

[0051] In the application, a large number of external cavity semiconductor laser smooth tuning calibration experiments are conducted in advance to calibrate and store a preset smooth tuning threshold. This threshold is the maximum critical value that the laser output power and the first derivative of the driving voltage can reach during normal mode-hopping smooth tuning. During laser wavelength tuning, the processing unit 33 continuously and in real-time compares the output power minus the first derivative of the driving voltage, calculated in real time, with the built-in preset smooth tuning threshold. When in a normal smooth tuning state without mode hopping, the laser output power changes continuously and gradually with the driving voltage, and the corresponding first derivative value remains stable within the preset smooth tuning threshold. The processing unit 33 determines that the tuning state is stable. However, when the laser experiences mode hopping due to a sudden change in external cavity resonance conditions, the abrupt change in oscillation mode directly causes a discontinuous and rapid jump in output power, causing the real-time calculated first derivative value to rise sharply and exceed the preset smooth tuning threshold. The processing unit 33 can then determine in real time that the laser has experienced mode hopping at the current tuning moment, thereby achieving real-time detection of mode hopping.

[0052] Based on the same inventive concept, this application also provides a laser mode hopping detection method, which is performed based on an external cavity semiconductor laser as described above. Figure 6 As shown, the laser mode hopping detection method includes the following steps S601 to S603.

[0053] S601: Real-time acquisition of laser output power and drive voltage during the tuning process.

[0054] S602: Determine the first derivative of the laser output power and the driving voltage based on the real-time acquired laser output power and driving voltage.

[0055] S603: Determine whether mode hopping occurs based on the first derivative of the laser output power and the driving voltage.

[0056] In some embodiments, the laser mode skipping detection method further includes the steps of controlling the driving voltage to gradually increase from low to high in step values, and recording the laser output power once every preset time or preset voltage to obtain corresponding data of driving voltage and laser output power.

[0057] It should be noted that the laser mode hopping detection method provided in this application embodiment is based on the same inventive concept as the external cavity semiconductor laser provided in this application embodiment. Therefore, the specific implementation of this embodiment can refer to the implementation of the aforementioned external cavity semiconductor laser, and the repeated parts will not be described again.

[0058] In some embodiments, an electronic device provided in this application includes a processor and a memory; the memory stores a computer program, wherein the computer program, when executed by the processor, implements the laser mode hopping detection method described above.

[0059] Specifically, the processor may include, for example, a general-purpose microprocessor, an instruction set processor and / or an associated chipset and / or a special-purpose microprocessor (e.g., an application-specific integrated circuit (ASIC)), etc. The processor may also include onboard memory for caching purposes. The processor may be a single processing unit or multiple processing units for performing different actions of the method flow according to embodiments of this application.

[0060] Memory can be any medium capable of containing, storing, transmitting, propagating, or transmitting instructions. For example, memory can include, but is not limited to, electrical, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, instruments, or propagation media. Specific examples of memory include: magnetic storage devices such as magnetic tape or hard disk drives (HDDs); optical storage devices such as optical discs (CD-ROMs); and also random access memory (RAM) or flash memory; and / or wired / wireless communication links.

[0061] This application also provides a non-transitory computer storage medium storing a computer program thereon, which, when executed by a processor, implements the laser mode hopping detection method described above. This computer-readable medium may be included in the device / apparatus / system described in the above embodiments; or it may exist independently and not assembled into that device / apparatus / system. The aforementioned computer-readable medium carries one or more programs, which, when executed, implement the method as described in the embodiments of this application.

[0062] According to embodiments of this application, a computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In this application, a computer-readable storage medium may be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In this application, a computer-readable signal medium may include a data signal propagated in baseband or as part of a carrier wave, carrying computer-readable program code. Such propagated data signals may take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. Computer-readable signal media can also be any computer-readable medium other than computer-readable storage media, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the computer-readable medium can be transmitted using any suitable medium, including but not limited to: wireless, wired, optical fiber, radio frequency signals, etc., or any suitable combination thereof.

[0063] It should be noted that the user information (including but not limited to user device information, user personal information, etc.) and data (including but not limited to data used for analysis, data stored, data displayed, etc.) involved in this application are all information and data authorized by the user or fully authorized by all parties, and the collection, use and processing of the relevant data must comply with relevant regulations.

[0064] Those skilled in the art will understand that the features described in the various embodiments of this application can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in this application. In particular, the features described in the various embodiments of this application can be combined and / or combined in various ways without departing from the spirit and teachings of this application. All such combinations and / or combinations fall within the scope of this application. Therefore, the scope of this application should not be limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An external cavity semiconductor laser, characterized in that, include: Laser output mechanism, wavelength tuning mechanism, and mode hopping detection mechanism; The laser output mechanism is used to generate zero-order diffracted light as laser output light and to generate first-order diffracted light as external cavity feedback light. The wavelength tuning mechanism is used to adjust the laser output mechanism under the drive of the driving voltage, so as to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light; The mode hopping detection mechanism is used to separate a predetermined proportion of sample light from the zero-order diffracted light, determine the laser output power based on the sample light, collect the laser output power and driving voltage in real time during the tuning process, determine the first derivative of the laser output power and the driving voltage based on the real-time collected laser output power and driving voltage, and determine whether mode hopping has occurred based on the first derivative of the laser output power and the driving voltage.

2. The external cavity semiconductor laser as described in claim 1, characterized in that, The laser output mechanism includes: a semiconductor laser diode, a collimating optical element, a diffraction grating, and a rotatable mirror; The semiconductor laser diode is used to output the initial beam; The collimating optical element is located in the output optical path of the semiconductor laser diode and is used to collimate the initial beam and output collimated light. The diffraction grating is located in the transmission optical path of the collimated light and is used to disperse the collimated light to output the zero-order diffracted light and the first-order diffracted light; The rotatable mirror is located on the transmission optical path of the first-order diffracted light, and is used to reflect the first-order diffracted light to the diffraction grating, and then reflect it back into the cavity of the semiconductor laser diode through the diffraction grating and the collimating optical element to form an external cavity resonance.

3. The external cavity semiconductor laser as described in claim 2, characterized in that, The wavelength tuning mechanism includes: a piezoelectric tuning element; The piezoelectric tuning element is used to adjust the orientation of the rotatable mirror under the drive voltage.

4. The external cavity semiconductor laser as described in claim 1, characterized in that, The mode-hopping detection mechanism includes: a beam-splitting component, a photodetector, and a processing unit; The beam splitter is located in the transmission optical path of the zero-order diffracted light and is used to separate a predetermined proportion of sample light from the zero-order diffracted light and project the sample light onto the photodetector. The photodetector is used to receive the sampled light and convert the sampled light into a power electrical signal; The processing unit is connected to the photodetector and is used to determine the laser output power based on the power electrical signal, and to acquire the laser output power and driving voltage in real time during the tuning process. Based on the real-time acquired laser output power and driving voltage, the unit determines the first derivative of the laser output power with respect to the driving voltage, and determines whether mode hopping occurs based on the first derivative of the laser output power with respect to the driving voltage.

5. The external cavity semiconductor laser as described in claim 4, characterized in that, The beam-splitting component is a beam splitter, a wedge-shaped glass plate, or a transparent optical element with a predetermined reflectivity.

6. The external cavity semiconductor laser as described in claim 4, characterized in that, The processing unit is also used to control the driving voltage to gradually increase from low to high in step values, and to record the laser output power once every preset time or preset voltage to obtain the corresponding data of the driving voltage and the laser output power.

7. The external cavity semiconductor laser as described in claim 4, characterized in that, The processing unit is also used to determine that mode hopping has occurred when the first derivative of the laser output power and the driving voltage is greater than a preset smoothing tuning threshold.

8. The external cavity semiconductor laser as described in claim 1, characterized in that, The sampling ratio of the sampled light is 0.5% to 2% of the zero-order diffraction light power.

9. A method for detecting mode skipping in a laser, characterized in that, The laser mode hopping detection method is performed based on an external cavity semiconductor laser as described in any one of claims 1 to 8; The laser mode hopping detection method includes: Real-time acquisition of laser output power and drive voltage during the tuning process; The first derivative of the laser output power with respect to the driving voltage is determined based on the real-time acquired laser output power and driving voltage. Whether mode hopping occurs is determined based on the first derivative of the laser output power and the driving voltage.

10. The laser mode hopping detection method as described in claim 9, characterized in that, The method further includes: The driving voltage is controlled to increase gradually from low to high in step values, and the laser output power is recorded once every preset time or preset voltage to obtain the corresponding data of the driving voltage and the laser output power.

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