Tunable laser mode hop suppression system, method and tunable laser
By integrating power detection, displacement detection, and collaborative compensation modules into a tunable laser, the output power and displacement of the laser are monitored and compensated in real time, solving the problem of accuracy in mode hopping detection and improving the stability of the laser during operation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- CENT CHINA OPTOELECTRONICS TECH RES INST (CHINA STATE SHIPBUILDING CORP 717TH RES INST)
- Filing Date
- 2026-06-09
- Publication Date
- 2026-07-07
AI Technical Summary
In existing technologies, mode hopping detection relies on external equipment for manual observation and disassembly, which cannot effectively suppress the mode hopping phenomenon of tunable lasers during operation, thus limiting performance improvement.
By employing a power detection module, a displacement detection module, and a collaborative compensation module, the laser output power and micro-driver displacement are monitored in real time, and the current and voltage compensation coefficients are calculated to achieve accurate identification and suppression of mode hopping.
It enables rapid and accurate mode hopping detection and suppression during laser operation, improves the stability of the laser wavelength tuning process, reduces the probability of false positives and false negatives, and avoids dependence on external equipment.
Smart Images
Figure CN122348413A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of precision optics technology, and in particular to a tunable laser mode hopping suppression system, method, and tunable laser. Background Technology
[0002] Tunable lasers have wide applications in fields such as fiber optic communication, laser interferometry, and spectral analysis. Among them, external cavity semiconductor lasers with Littrow and Littman structures have become a research hotspot due to their advantages such as narrow linewidth and wide tuning range. However, the mode-hopping problem is a key technical challenge that restricts the improvement of tunable laser performance and its large-scale application.
[0003] Currently, mode hopping detection typically relies on manual observation using external high-resolution wavelength meters, Fabry-Perot interferometers, or spectral analysis equipment. After manual assessment, the laser needs to be disassembled for repair and adjustment before mode hopping monitoring and suppression can be performed. This method is suitable for calibrating tunable lasers before they leave the factory, but it is not suitable for suppressing mode hopping during the operation of tunable lasers. Summary of the Invention
[0004] In view of this, this application proposes a mode hopping suppression system, method and tunable laser for tunable lasers.
[0005] In a first aspect, this application provides a tunable laser mode hopping suppression system, comprising: a power detection module, a displacement detection module, and a collaborative compensation module; The power detection module is used to separate a predetermined proportion of sample light from the laser output light and determine the laser output power based on the sample light. The displacement detection module is mounted on the wavelength tuning mechanism and is used to measure the actual driving displacement of the micro-actuator. The collaborative compensation module is used to acquire the laser output power and micro-driver driving voltage during the tuning process. It determines whether mode hopping occurs based on the first derivative of the laser output power and the micro-driver driving voltage. When mode hopping is determined to have occurred, it calculates the deviation between the theoretical displacement driving amount corresponding to the current injection voltage of the micro-driver and the actual driving displacement amount. It determines the compensation coefficients for injection current compensation and injection voltage compensation based on the deviation amount, and adjusts the injection current of the laser diode and the excitation voltage of the micro-driver based on the compensation coefficients for injection current compensation and injection voltage compensation.
[0006] In one embodiment, the collaborative compensation module is further configured to determine the deviation operating condition range in which the deviation amount is located as the target range, determine the optimization range of the injection current compensation coefficient and the injection voltage compensation coefficient according to the target range, perform iterative optimization using a preset optimization algorithm, and determine the optimal compensation coefficient combination according to the mode skipping detection result.
[0007] In one embodiment, the collaborative compensation module is further configured to: determine a large deviation operating condition interval as a target interval when the deviation is greater than a first preset amount; determine a medium deviation operating condition interval as a target interval when the deviation is greater than a second preset amount but less than or equal to the first preset amount; and determine a small deviation operating condition interval as a target interval when the deviation is less than or equal to the second preset amount. Wherein, the lower limit of the injection voltage compensation coefficient corresponding to the large deviation operating condition interval is not less than the upper limit of the injection voltage compensation coefficient corresponding to the medium deviation operating condition interval, the lower limit of the injection voltage compensation coefficient corresponding to the medium deviation operating condition interval is not less than the upper limit of the injection voltage compensation coefficient corresponding to the small deviation operating condition interval, the range of the injection current compensation coefficient corresponding to the small deviation operating condition interval covers the range of the injection current compensation coefficient corresponding to the medium deviation operating condition interval, and the range of the injection current compensation coefficient corresponding to the medium deviation operating condition interval covers the range of the injection current compensation coefficient corresponding to the large deviation operating condition interval.
[0008] In one embodiment, the collaborative compensation module 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.
[0009] In one embodiment, the power detection module includes: a beam splitting unit and a photoelectric detection unit; The beam splitting unit is used to separate a predetermined proportion of sampled light from the output light and project it to the photoelectric detection unit; The photoelectric detection unit is used to generate a detection electrical signal based on the sampled light, and to determine the laser output power based on the detection electrical signal.
[0010] In one embodiment, the displacement detection module includes a displacement sensor disposed on the rotating arm of the wavelength tuning mechanism, the displacement sensor being used to measure the actual driving displacement of the micro-actuator.
[0011] Secondly, this application also provides a method for suppressing mode hopping in a tunable laser, comprising: Obtain the laser output power and micro-driver driving voltage during the tuning process; Whether mode hopping occurs is determined based on the first derivative of the laser output power and the micro-driver driving voltage. When mode hopping is detected, the deviation between the theoretical displacement driving amount corresponding to the current injection voltage of the micro-actuator and the actual driving displacement amount is calculated, and the compensation coefficients for injection current compensation and injection voltage compensation are determined based on the deviation. The injection current of the laser diode and the excitation voltage of the micro-driver are adjusted according to the compensation coefficients of the injection current compensation and injection voltage compensation.
[0012] Thirdly, this application also provides a tunable laser, including: a laser output mechanism, a wavelength tuning mechanism, and a tunable laser mode hopping suppression system as described in the first aspect; 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 micro-driver driving voltage, so as to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light.
[0013] 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.
[0014] In one embodiment, the laser output mechanism includes: a semiconductor laser diode, a collimating optical element, and a rotatable diffraction grating; 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 rotatable diffraction grating is located on the transmission optical path of the collimated light and is used to disperse the collimated light, output the zeroth-order diffracted light and the first-order diffracted light; and reflect the first-order diffracted light, which is then reflected back into the cavity of the semiconductor laser diode through the collimating optical element to form an external cavity resonance.
[0015] The tunable laser mode hopping suppression system of this application has the following advantages over related technologies: 1. The tunable laser mode hopping suppression system of this application includes a power detection module, a displacement detection module, and a collaborative compensation module. The power detection module obtains the laser output power by separating a predetermined proportion of sampled light, ensuring real-time and accurate perception of the laser energy output state. Since the linear relationship between power and voltage is broken when mode hopping occurs, and the first derivative will show a significant anomaly, the collaborative compensation module uses the first derivative of the laser output power and the micro-driver driving voltage as the basis for mode hopping judgment. It can capture the dynamic characteristics of power changing with voltage during tuning. This judgment method can accurately identify instantaneous mode hopping behavior, greatly reduce the probability of false judgment and false omission, and does not require the introduction of external wavelength detection equipment with complex structure and large volume in the prior art. Therefore, mode hopping detection can be realized quickly and accurately during laser operation.
[0016] 2. By directly integrating the displacement detection module into the wavelength tuning mechanism, the actual driving displacement of the micro-actuator can be accurately captured. Based on this, when mode hopping is detected, the collaborative compensation module calculates the deviation between the theoretical and actual driving displacement to directly pinpoint the core cause of mode hopping. Based on this deviation, targeted current and voltage compensation coefficients are derived. On one hand, the displacement deviation is corrected through micro-actuator excitation voltage compensation, resolving the mechanical drive misalignment problem of the tuning mechanism. On the other hand, the laser diode injection current compensation optimizes the energy conditions of the laser, offsetting the mode instability risk caused by the displacement deviation. This bidirectional collaborative compensation method effectively suppresses mode hopping during laser operation, significantly improving the stability of the laser wavelength tuning process. 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 a tunable laser mode hopping suppression system in one embodiment of this application; Figure 2 This is a schematic diagram of the structure of a tunable laser including a tunable laser mode hopping suppression system in one embodiment of this application; Figure 3 This is a schematic diagram of the laser output power and the first derivative of the laser output power with respect to the driving voltage when no mode hopping occurs in one embodiment of this application; Figure 4This is a schematic diagram of the laser output power and the first derivative of the laser output power with respect to the driving voltage when mode hopping occurs in one embodiment of this application; Figure 5 This is a flowchart illustrating a method for suppressing mode hopping in a tunable laser according to an embodiment of this application. Figure 6 This is a schematic diagram of a Littman tunable laser in one embodiment of this application; Figure 7 This is a schematic diagram of the structure of a Littman improved tunable laser in one embodiment of this application; Figure 8 This is a schematic diagram of a Littrow tunable laser in one embodiment of this application.
[0019] Explanation of reference numerals in the attached figures: 10-Tunable laser mode hopping suppression system, 11-Power detection module, 111-Beam splitting unit, 112-Photoelectric detection unit, 12-Displacement detection module, 13-Collaborative compensation module, 20-Laser output mechanism, 21-Semiconductor laser diode, 22-Collimating optical element, 23-Diffraction grating, 24-Rotating mirror, 30-Wavelength tuning mechanism. 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 a tunable laser mode hopping suppression system 10, comprising: a power detection module 11, a displacement detection module 12, and a collaborative compensation module 13. It should be noted that the laser structure using the tunable laser mode hopping suppression system 10 can be as follows: Figure 2 As shown, the laser includes a laser output mechanism 20, a wavelength tuning mechanism 30, and a tunable laser mode hopping suppression system 10. The laser output mechanism 20 generates zero-order diffracted light as the laser output light and generates first-order diffracted light as the external cavity feedback light. The wavelength tuning mechanism 30 adjusts the laser output mechanism 20 under the drive voltage of the micro-driver to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light. The tunable laser mode hopping suppression system 10 detects and suppresses mode hopping during laser operation.
[0022] The power detection module 11 is used to separate a predetermined proportion of sample light from the laser output light and determine the laser output power based on the sample light. The power detection module 11 separates a fixed and preset proportion of sample light from the normally output beam of the laser using optical beam splitting. This beam splitting method ensures that the output power and transmission characteristics of the laser's main optical path are not disturbed, maintaining the normal operation of the laser, while also acquiring a detection light signal that represents the overall output light power characteristics. Subsequently, photoelectric detection, signal conversion, and power conversion processing can be performed based on this sample light to accurately and in real-time determine the current actual output power of the laser, providing real and effective power reference data for monitoring the overall operating status of the laser and subsequent related control operations.
[0023] The displacement detection module 12 is mounted on the wavelength tuning mechanism 30 and is used to measure the actual driving displacement of the micro-actuator. The displacement detection module 12 can directly and accurately measure the actual driving displacement generated by the micro-actuator during wavelength tuning, providing a direct reflection of the micro-actuator's mechanical driving performance and offering accurate and reliable actual displacement detection data to support the monitoring of the laser wavelength tuning mechanism 30's operating status. It should be noted that the micro-actuator adjusts the laser output mechanism 20 under the drive voltage to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light. The micro-actuator uses the drive voltage as a control signal and receives continuously adjustable or stepped electrical signals to achieve precise action, thereby controlling the core optical parameters of the laser output mechanism 20.
[0024] The collaborative compensation module 13 is used to acquire the laser output power and micro-driver driving voltage during the tuning process. It determines whether mode hopping occurs based on the first derivative of the laser output power and the micro-driver driving voltage. When mode hopping is determined to occur, it calculates the deviation between the theoretical displacement driving amount corresponding to the current injection voltage of the micro-driver and the actual driving displacement amount. It determines the compensation coefficients for injection current compensation and injection voltage compensation based on the deviation. It adjusts the injection current of the laser diode and the excitation voltage of the micro-driver based on the compensation coefficients for injection current compensation and injection voltage compensation.
[0025] This includes the ability to store the theoretical driving displacement corresponding to different voltages at the time of manufacture of the micro-driver via a storage module. Based on the inherent characteristics of external cavity semiconductor laser tuning, such as... Figure 3 As shown, during normal, mode-skipping tuning, the first derivative value (dP / dV) exhibits a stable and continuous change. Figure 4As shown, when a laser experiences mode hopping, the abrupt change in the oscillation mode can cause discontinuous changes such as a sudden increase or decrease in output power. This can lead to significant steps, abrupt changes, sudden increases or decreases, or abnormal fluctuations in the first derivative value. By identifying these abnormal changes in the first derivative, it is possible to accurately and in real time determine whether the laser has experienced mode hopping during the tuning process, providing a real-time basis for monitoring and judging mode hopping in the laser's wavelength tuning process.
[0026] In the application, the laser output power data fed back by the power detection module 11 is first collected in real time, and the actual driving voltage signal when the micro-driver is working is obtained, thus constructing a dynamic data correlation reflecting the laser output state and the tuning driving state. Then, by calculating the first derivative of the laser output power and the micro-driver driving voltage, the dynamic relationship between the two is accurately captured. Since the abrupt change in laser mode during mode hopping will break the linear correlation between output power and driving voltage, the first derivative will fluctuate significantly. This serves as the core basis for mode hopping determination, which can effectively determine whether mode hopping should be initiated.
[0027] After confirming mode hopping, the collaborative compensation module 13 calls the actual driven displacement obtained by the displacement detection module 12 and combines it with the theoretical driven displacement corresponding to the current micro-actuator injection voltage. The deviation between the two is calculated quantitatively. This deviation is significantly related to the core cause of mode hopping. Therefore, based on this deviation, a preset algorithm can be used to derive the injection current compensation coefficient and injection voltage compensation coefficient adapted to the current operating condition, ensuring that the compensation strategy accurately matches the actual deviation. Finally, according to the obtained compensation coefficients, the injection current of the laser diode and the excitation voltage of the micro-actuator are synchronously adjusted to suppress mode hopping, thereby ensuring the stability of the laser tuning process.
[0028] The aforementioned tunable laser mode hopping suppression system 10 includes a power detection module 11, a displacement detection module 12, and a collaborative compensation module 13. The power detection module 11 obtains the laser output power by separating a predetermined proportion of sampled light, ensuring real-time and accurate sensing of the laser energy output state. Since the linear relationship between power and voltage is broken when mode hopping occurs, and the first derivative exhibits significant anomalies, the collaborative compensation module 13 uses the first derivative of the laser output power and the micro-driver driving voltage as the basis for mode hopping determination. This captures the dynamic characteristics of power changes with voltage during tuning. This determination method can accurately identify instantaneous mode hopping behavior, significantly reducing the probability of false positives and false negatives, and eliminates the need for complex and bulky external wavelength detection equipment found in existing technologies. Therefore, mode hopping detection can be achieved quickly and accurately during laser operation. By directly placing the displacement detection module 12 within the wavelength tuning mechanism 30, the actual driving displacement of the micro-driver can be accurately captured. Based on this, when mode hopping is detected, the collaborative compensation module 13 can directly locate the core cause of mode hopping by calculating the deviation between the theoretical displacement driving amount and the actual driving displacement amount. Based on this deviation, it can specifically deduce the current and voltage compensation coefficients. On the one hand, it corrects the displacement deviation by compensating the excitation voltage of the micro-actuator, thus solving the problem of mechanical drive misalignment of the tuning mechanism. On the other hand, it optimizes the energy conditions of laser generation by compensating the injection current of the laser diode, thus offsetting the risk of mode instability caused by displacement deviation. This two-way collaborative compensation method can effectively suppress mode hopping that occurs during laser operation and significantly improve the stability of the laser wavelength tuning process.
[0029] In some embodiments, the collaborative compensation module 13 is further configured to determine the deviation condition range in which the deviation amount is located as the target range, determine the optimization range of the injection current compensation coefficient and the injection voltage compensation coefficient according to the target range, perform iterative optimization using a preset optimization algorithm, and determine the optimal combination of compensation coefficients according to the mode jump detection result.
[0030] In application, multiple deviation working condition ranges can be preset. The range division is based on the quantitative analysis results of the impact of different deviation degrees on the mode jump. Different ranges correspond to the compensation strength level required to suppress the mode jump.
[0031] After determining the deviation, the specific interval into which the current deviation falls is identified and designated as the target interval. Then, based on the target interval, the effective optimization range of the injection current compensation coefficient and the injection voltage compensation coefficient is determined. Finally, the system's built-in preset optimization algorithm is invoked (e.g., it can iterate and try with preset step values until the optimal solution is reached). Multiple rounds of iterative optimization are performed within the defined optimization range. During each iteration, data such as laser output power and micro-driver driving voltage are collected synchronously, and mode hopping detection is performed in real time through first-order derivative analysis. Ultimately, the optimal solution is selected from multiple combinations of compensation coefficients generated through iteration, based on whether the mode hopping phenomenon is eliminated and whether the laser output power and wavelength stability are optimal. This ensures that the compensation strategy accurately matches the current deviation condition and achieves both optimal mode hopping suppression and laser operating stability.
[0032] In some embodiments, the collaborative compensation module 13 is further configured to: determine the large deviation operating condition range as the target range when the deviation is greater than a first preset amount; determine the medium deviation operating condition range as the target range when the deviation is greater than a second preset amount but less than or equal to the first preset amount; and determine the small deviation operating condition range as the target range when the deviation is less than or equal to the second preset amount. Wherein, the lower limit of the injection voltage compensation coefficient corresponding to the large deviation operating condition range is not less than the upper limit of the injection voltage compensation coefficient corresponding to the medium deviation operating condition range, the lower limit of the injection voltage compensation coefficient corresponding to the medium deviation operating condition range is not less than the upper limit of the injection voltage compensation coefficient corresponding to the small deviation operating condition range, the range of the injection current compensation coefficient corresponding to the small deviation operating condition range covers the range of the injection current compensation coefficient corresponding to the medium deviation operating condition range, and the range of the injection current compensation coefficient corresponding to the medium deviation operating condition range covers the range of the injection current compensation coefficient corresponding to the large deviation operating condition range.
[0033] In the application, the driver displacement of the laser under factory calibration is read from the storage module and recorded as the reference displacement X_ref (unit: μm). The actual output displacement of the micro-driver drive mechanism is collected in real time by the displacement detection module 12 and recorded as the current actual displacement X_act. The displacement deviation Δδ is calculated by the following formula: Δδ=|(X_act-X_ref)| / X_ref×100%.
[0034] The compensation strategy is selected based on the deviation. The compensation method involves simultaneously measuring and compensating the laser diode injection current and the micro-driver injection voltage. Compensation coefficients for injection current and injection voltage are selected based on the deviation Δδ. Upon receiving instructions from the collaborative compensation module 13, the excitation voltage of the micro-driver is multiplied by a corresponding coefficient 'a' to obtain the compensation voltage. This compensation voltage is then superimposed on the original excitation voltage to form the final driving voltage of the micro-driver. Wavelength tuning and mode hopping compensation are achieved by adjusting the external cavity length. Upon receiving instructions from the collaborative compensation module 13, an excitation current 'i', where 'i=b*I', is added to the injection current 'I' of the laser diode.
[0035] Compensation strategy: The displacement deviation Δδ is compared with a preset threshold. Based on the range of the deviation, the optimization range of the micro-driver voltage excitation coefficient a and the laser diode current excitation coefficient b is determined. Then, the optimal combination of compensation coefficients is determined by traversal optimization, binary search optimization, and other optimization algorithms until mode skipping is eliminated. The specific strategy is divided into the following three cases: large deviation condition, medium deviation condition, and small deviation condition.
[0036] Large deviation condition (Δδ>10%): The root cause of mode hopping is determined to be aging, hysteresis, creep, or mechanical structural deformation of the micro-actuator (piezoelectric ceramic). In this case, the system adopts a strategy mainly based on micro-actuator excitation compensation, with the micro-actuator voltage excitation coefficient 'a' ranging from 10% to 20%, and the laser diode excitation current coefficient 'b' ranging from -5% to 5%.
[0037] Medium deviation condition (10%≥Δδ>5%): It is determined that the contributions of structural factors and current factors are equal. At this time, the system adopts a balanced compensation strategy, and sets the range of the micro-driver voltage excitation coefficient a to 5% to 10%, and the range of the laser diode excitation current coefficient b to -10% to 10%.
[0038] Small deviation condition (5%≥Δδ): The root cause of mode skipping is mainly determined to be current source fluctuation, laser diode aging, or temperature change. In this case, the system adopts a strategy mainly based on current compensation, setting the range of the micro-driver voltage excitation coefficient a to 0% to 5%, and the range of the laser diode excitation current coefficient b to -15% to 15%.
[0039] In some embodiments, the collaborative compensation module 13 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.
[0040] For example, the smoothing threshold can be 0.1.
[0041] In the application, a large number of external cavity semiconductor laser smooth tuning calibration experiments are conducted beforehand to calibrate and store a preset smooth tuning threshold. This threshold represents the maximum critical value that the laser output power and the first derivative of the driving voltage can reach during normal, mode-hopping-free smooth tuning. During laser wavelength tuning, the first derivative value of the output power minus the driving voltage, calculated in real time, is continuously and in real-time compared with this built-in preset smooth tuning threshold. When in a normal, mode-hopping-free smooth tuning state, 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, indicating a stable tuning state. 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 surge dramatically and exceed the preset smooth tuning threshold. This allows for real-time detection of mode hopping at the current tuning moment.
[0042] In some embodiments, the power detection module 11 includes a beam splitting unit 111 and a photoelectric detection unit 112.
[0043] The beam splitting unit 111 is used to separate a predetermined proportion of sample light from the output light and project it to the photoelectric detection unit 112. The photoelectric detection unit 112 is used to generate a detection electrical signal based on the sample light and determine the laser output power based on the detection electrical signal.
[0044] The power detection module 11 can be integrated inside the laser, the beam splitting unit 111 can include at least one beam splitter, and the photoelectric detection unit 112 can include a photodiode (PD) and a power measurement circuit.
[0045] It is understandable that each unit works in sequence according to the optical path and signal processing. The beam splitting unit 111, located on the laser output optical path, can stably separate a predetermined proportion of sampled light from the laser output beam without affecting normal transmission. This sampled light is then projected onto the photoelectric detection unit 112. The photoelectric detection unit 112 performs photoelectric conversion processing on the received sampled light, converting the optical signal into a continuous and collectable detection electrical signal, thereby achieving effective conversion from optical to electrical signals. Subsequently, based on the detection electrical signal, combined with the photoelectric conversion correspondence and calibration parameters, calculations and analyses are performed to accurately calculate and provide real-time feedback on the actual output power of the laser.
[0046] In some embodiments, the displacement detection module 12 includes a displacement sensor disposed on the rotating arm of the wavelength tuning mechanism 30, the displacement sensor being used to measure the actual driving displacement of the micro-actuator.
[0047] Based on the same inventive concept, such as Figure 5As shown, this application also provides a method for suppressing mode hopping in a tunable laser, including the following steps S501 to S504.
[0048] S501: Acquires the laser output power and micro-driver drive voltage during the tuning process.
[0049] S502: Determine whether mode hopping occurs based on the first derivative of the laser output power and the micro-driver driving voltage.
[0050] S503: When mode hopping is detected, calculate the deviation between the theoretical displacement driving amount corresponding to the current injection voltage of the micro-actuator and the actual driving displacement amount, and determine the compensation coefficients for injection current compensation and injection voltage compensation based on the deviation.
[0051] S504: Adjust the injection current of the laser diode and the excitation voltage of the micro-driver according to the compensation coefficients of injection current compensation and injection voltage compensation.
[0052] It should be noted that the tunable laser mode hopping suppression method provided in this application embodiment and the tunable laser mode hopping suppression system provided in this application embodiment are based on the same inventive concept. Therefore, the specific implementation of this embodiment can refer to the implementation of the aforementioned tunable laser mode hopping suppression method, and the repeated parts will not be described again.
[0053] In some embodiments, such as Figure 2 As shown, this application also provides a tunable laser, including: a laser output mechanism 20, a wavelength tuning mechanism 30, and a tunable laser mode hopping suppression system 10 as described in any of the above embodiments.
[0054] The laser output mechanism 20 is used to generate zero-order diffracted light as laser output light and to generate first-order diffracted light as external cavity feedback light.
[0055] The wavelength tuning mechanism 30 is used to adjust the laser output mechanism 20 under the drive of the micro-driver driving voltage, so as to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light.
[0056] The laser output mechanism 20 can output collimated light. The collimated light is dispersed by a diffraction grating 23, which decomposes the collimated light into diffracted light of different orders based on the principle of light diffraction. The zeroth-order diffracted light, due to its concentrated energy and stable propagation direction, is directly selected as the laser's 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 reflected back along the original optical path into the active cavity of the laser output mechanism 20 through appropriate optical path design, 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.
[0057] The wavelength tuning mechanism 30 can change the propagation path and phase conditions of the first-order diffracted light by adjusting the optical path length of the external cavity in the laser output mechanism 20, the incident angle of the diffraction grating 23, or the position of the mirror, so that the wavelength of the feedback light is continuously or discretely shifted. The output wavelength of the external cavity semiconductor laser is determined by the resonance conditions 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 conditions, and finally the controllable tuning of the wavelength of the laser output light (zero-order diffracted light) is realized.
[0058] It is understood that the laser output mechanism 20 can generate diffracted beams of different orders through diffraction, stably outputting zero-order diffracted light as the effective output light of the laser, and generating first-order diffracted light as the external cavity feedback light, providing a feedback basis for the resonant operation of the laser. The wavelength tuning mechanism 30 can complete precise action adjustment under the action of the micro-driver driving voltage, and perform linkage control on the working state of the laser output mechanism 20. By changing the transmission conditions and wavelength characteristics of the external cavity feedback light in real time, the continuous tuning of the laser output wavelength is achieved. At the same time, relying on the matching mode skipping suppression system, various parameters of the tuning process are monitored in real time and dynamically compensated and corrected to ensure the smooth operation of the wavelength tuning process.
[0059] It should be noted that when a tunable laser uses a Littman structure, the laser structure can be as follows: Figure 6 As shown, the power detection module 11 includes the beam splitter and PD (photodiode) shown in the figure, the displacement detection module 12 includes a displacement sensor, and the collaborative compensation module 13 includes a processing unit. Similarly, when the tunable laser adopts the Littman improved structure, the laser structure can be as follows: Figure 7 As shown; when a tunable laser uses a Littrow structure, the laser structure can be as follows: Figure 8 As shown.
[0060] In some embodiments, corresponding to Littman structure lasers, such as Figure 2 , Figure 6 and Figure 7 As shown, the laser output mechanism 20 includes: a semiconductor laser diode 21, a collimating optical element 22, a diffraction grating 23, and a rotatable mirror 24.
[0061] The semiconductor laser diode 21 is used to output an initial beam. The collimating optical element 22 is located in the output optical path of the semiconductor laser diode 21 and is used to collimate the initial beam and output collimated light. The diffraction grating 23 is located in the transmission optical path of the collimated light and is used to disperse the collimated light and output the zeroth-order diffracted light and the first-order diffracted light.
[0062] The rotatable mirror 24 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 23, and then reflect it back to the cavity of the semiconductor laser diode 21 through the diffraction grating 23 and the collimating optical element 22 to form an external cavity resonance.
[0063] Among them, the semiconductor laser diode 21 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 22 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 21 and matches 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, so as to provide an incident beam that meets the optical conditions for the precise dispersion of the subsequent diffraction grating 23.
[0064] The diffraction grating 23 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 23 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 21 to form optical feedback, providing key feedback light conditions for the resonant oscillation of the external cavity semiconductor laser.
[0065] The rotatable mirror 24 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 23, and then reflect it back into the cavity of the semiconductor laser diode 21 through the diffraction grating 23 and the collimating optical element 22 to form an external cavity resonance.
[0066] It is understood that the rotatable mirror 24 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 23, 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, using its high reflectivity to reduce light energy loss, and reflect the first-order diffracted light back to the working surface of the original diffraction grating 23 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 24, is re-injected into the diffraction grating 23. 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 22. At this point, the collimating optical element 22 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 21. 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.
[0067] In some embodiments, corresponding to the Littrow structure, such as Figure 8 As shown, the laser output mechanism includes: a semiconductor laser diode, a collimating optical element, and a rotatable diffraction grating.
[0068] The semiconductor laser diode is used to output an 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 rotatable diffraction grating is located in the transmission optical path of the collimated light and is used to disperse the collimated light, outputting the zeroth-order diffracted light and the first-order diffracted light; and reflects the first-order diffracted light, which is then reflected back into the cavity of the semiconductor laser diode through the collimating optical element to form an external cavity resonance.
[0069] It is understandable that the difference between the Littrow structure and the aforementioned Littman structure laser lies in the rotatable diffraction grating. The Littrow structure laser can directly adjust the diffraction grating, thereby directly reflecting the first-order diffracted light through the diffraction grating, which is then reflected back into the cavity of the semiconductor laser diode by the collimating optical element to form an external cavity resonance.
[0070] In some embodiments, such as Figure 2 As shown, the wavelength tuning mechanism 30 includes a piezoelectric tuning element. The piezoelectric tuning element is used to adjust the pose of the rotatable mirror 24 or the rotatable diffraction grating under the drive voltage.
[0071] 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.
[0072] In applications, taking a Littman structure laser as an example, one end of the piezoelectric tuning element is rigidly coupled to the mounting base or drive shaft of the rotatable reflector 24, 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 driving 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 24 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 24 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 23 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 23, continuous and high-precision tuning of the laser output wavelength can be achieved.
[0073] 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 above-described tunable laser mode hopping suppression method.
[0074] This application also provides a non-transitory computer storage medium storing a computer program thereon, which, when executed by a processor, implements the above-described tunable laser mode hopping suppression method. 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.
[0075] 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.
[0076] 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. A mode hopping suppression system for a tunable laser, characterized in that, include: Power detection module, displacement detection module, and collaborative compensation module; The power detection module is used to separate a predetermined proportion of sample light from the laser output light and determine the laser output power based on the sample light. The displacement detection module is mounted on the wavelength tuning mechanism and is used to measure the actual driving displacement of the micro-actuator. The collaborative compensation module is used to acquire the laser output power and micro-driver driving voltage during the tuning process. It determines whether mode hopping occurs based on the first derivative of the laser output power and the micro-driver driving voltage. When mode hopping is determined to have occurred, it calculates the deviation between the theoretical displacement driving amount corresponding to the current injection voltage of the micro-driver and the actual driving displacement amount. It determines the compensation coefficients for injection current compensation and injection voltage compensation based on the deviation amount, and adjusts the injection current of the laser diode and the excitation voltage of the micro-driver based on the compensation coefficients for injection current compensation and injection voltage compensation.
2. The tunable laser mode hopping suppression system as described in claim 1, characterized in that, The collaborative compensation module is also used to determine the deviation condition range in which the deviation amount is located as the target range, determine the optimization range of the injection current compensation coefficient and the injection voltage compensation coefficient according to the target range, perform iterative optimization using a preset optimization algorithm, and determine the optimal combination of compensation coefficients based on the mode jump detection results.
3. The tunable laser mode hopping suppression system as described in claim 2, characterized in that, The collaborative compensation module is further configured to: determine the large deviation operating condition range as the target range when the deviation is greater than a first preset value; determine the medium deviation operating condition range as the target range when the deviation is greater than a second preset value but less than or equal to the first preset value; and determine the small deviation operating condition range as the target range when the deviation is less than or equal to the second preset value. Wherein, the lower limit of the injection voltage compensation coefficient corresponding to the large deviation operating condition range is not less than the upper limit of the injection voltage compensation coefficient corresponding to the medium deviation operating condition range, the lower limit of the injection voltage compensation coefficient corresponding to the medium deviation operating condition range is not less than the upper limit of the injection voltage compensation coefficient corresponding to the small deviation operating condition range, the range of the injection current compensation coefficient corresponding to the small deviation operating condition range covers the range of the injection current compensation coefficient corresponding to the medium deviation operating condition range, and the range of the injection current compensation coefficient corresponding to the medium deviation operating condition range covers the range of the injection current compensation coefficient corresponding to the large deviation operating condition range.
4. The tunable laser mode hopping suppression system as described in claim 1, characterized in that, The collaborative compensation module 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.
5. The tunable laser mode hopping suppression system as described in claim 1, characterized in that, The power detection module includes: a beam splitting unit and a photoelectric detection unit; The beam splitting unit is used to separate a predetermined proportion of sampled light from the output light and project it to the photoelectric detection unit; The photoelectric detection unit is used to generate a detection electrical signal based on the sampled light, and to determine the laser output power based on the detection electrical signal.
6. The tunable laser mode hopping suppression system as described in claim 1, characterized in that, The displacement detection module includes a displacement sensor, which is mounted on the rotating arm of the wavelength tuning mechanism and is used to measure the actual driving displacement of the micro-actuator.
7. A method for suppressing mode hopping in a tunable laser, characterized in that, include: Obtain the laser output power and micro-driver driving voltage during the tuning process; Whether mode hopping occurs is determined based on the first derivative of the laser output power and the micro-driver driving voltage. When mode hopping is detected, the deviation between the theoretical displacement driving amount corresponding to the current injection voltage of the micro-actuator and the actual driving displacement amount is calculated, and the compensation coefficients for injection current compensation and injection voltage compensation are determined based on the deviation. The injection current of the laser diode and the excitation voltage of the micro-driver are adjusted according to the compensation coefficients of the injection current compensation and injection voltage compensation.
8. A tunable laser, characterized in that, include: A laser output mechanism, a wavelength tuning mechanism, and a tunable laser mode hopping suppression system as described in any one of claims 1 to 6; 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 micro-driver driving voltage, so as to achieve laser wavelength tuning by changing the wavelength of the external cavity feedback light.
9. The tunable laser as described in claim 8, 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.
10. The tunable laser as claimed in claim 8, characterized in that, The laser output mechanism includes: a semiconductor laser diode, a collimating optical element, and a rotatable diffraction grating; 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 rotatable diffraction grating is located on the transmission optical path of the collimated light and is used to disperse the collimated light, output the zeroth-order diffracted light and the first-order diffracted light; and reflect the first-order diffracted light, which is then reflected back into the cavity of the semiconductor laser diode through the collimating optical element to form an external cavity resonance.