Optical path adjusting method and device based on saturated absorption spectrum and PSD feedback

Abstract

According to the light path adjusting method based on the saturated absorption spectrum and the PSD feedback, a detection light signal is received through a PSD position detector in a miniaturized and integrated semiconductor laser with saturated absorption spectrum frequency stabilization, a scanning signal instruction is issued through an upper computer, at the moment, a saturated absorption peak appears in the detection light signal, and the detection light signal is sent to the upper computer; after the upper computer receives an absorption peak signal, the voltage is adjusted, the angle of the piezoelectric deflecting mirror is further adjusted, light path alignment is adjusted in real time, light path alignment can be compensated in real time through a PSD signal in the frequency locking process, the frequency locking stability is improved, and the saturated absorption effect is enhanced. The application requirement for real-time compensation of light path alignment when a frequency stabilization system light path needs to be set up in the frequency stabilization process of a semiconductor laser is effectively met.

Description

Technical Field

[0001] This invention relates to the field of laser technology, specifically to an optical path adjustment method and apparatus based on saturated absorption spectrum and PSD feedback. Background Technology

[0002] Semiconductor lasers, due to their advantages of small size, high efficiency, and low cost, are widely used in precision measurement fields such as laser spectroscopy, atomic and molecular physics, and quantum frequency standards. External cavity semiconductor lasers can narrow their linewidth to below 1 MHz through grating feedback, but they still exhibit slow drift and mode hopping phenomena, requiring active frequency stabilization using atomic absorption spectra as a reference. Traditional frequency stabilization schemes generate an error signal by comparing the deviation between the laser frequency and the atomic saturation absorption peak. This error signal is then fed back by a PID controller to adjust the injection current and piezoelectric ceramic (PZT), achieving frequency locking.

[0003] However, the stability of the saturated absorption spectrum is highly dependent on the optical path alignment accuracy: the probe light must interact precisely with the atomic swarm in the atomic gas cell at zero velocity to produce a high signal-to-noise ratio saturated absorption peak. Existing frequency stabilization systems mostly use fixed mechanical structures for their optical paths, which are susceptible to environmental interference such as temperature changes and mechanical vibrations, leading to optical path offset. This manifests in several ways: First, absorption peak signal attenuation. Optical path offset reduces the efficiency of the interaction between the probe light and atoms, decreasing the amplitude and broadening the linewidth of the saturated absorption peak, thus reducing the stability of the frequency reference. Second, error signal distortion. Offset causes the absorption peak center frequency to drift, resulting in deviations in the adjustment signals fed back to the PZT and current, exacerbating the risk of laser mode hopping. Third, low system integration. The system relies on large optical platforms and manual alignment, making it difficult to meet the needs of miniaturized devices for dynamic optical path compensation.

[0004] Traditional ECDL frequency stabilization only focuses on frequency error feedback, neglecting real-time compensation for optical path alignment. This results in optical path misalignment becoming a key bottleneck limiting stability during frequency locking. Therefore, developing an integrated solution that uses a PSD to monitor the optical path alignment status in real time, combined with dynamic adjustment by a piezoelectric deflector, is of great significance for improving the frequency stabilization accuracy and environmental adaptability of semiconductor lasers. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention proposes an optical path adjustment method based on saturated absorption spectrum and PSD feedback to solve the frequency stabilization accuracy problem caused by the need to build a frequency stabilization system optical path during the frequency stabilization process of existing semiconductor lasers.

[0006] To achieve the above objectives, the invention provides an optical path adjustment method based on saturated absorption spectrum and PSD feedback, comprising the following steps: S1. A position detector detects saturated and absorbed light signals; S2. A host computer sends a scanning signal; S3. The host computer reads the absorption peak of the position detector signal; S4. The voltage is adjusted according to the absorption peak; S5. The piezoelectric ceramic deforms according to the adjusted voltage; S6. The deformation of the piezoelectric ceramic causes a change in the position of the deflection lens; S7. Optical path adjustment is achieved by changing the lens position.

[0007] Preferably, the wavelength range of the optical signal detected by the position detector is 400-1100nm.

[0008] Preferably, in step S4, the range of the adjusted voltage is 0-100V, and the adjustment accuracy is 0.1V.

[0009] Preferably, the maximum deformation of the piezoelectric ceramic is 50 μm.

[0010] Preferably, in step S6, the deflecting lens is a convex lens with a focal length range of 3-8mm.

[0011] An optical path adjustment device based on PSD signals, applied to a miniaturized semiconductor laser, includes: a position detector for performing step S1 to detect saturated and absorbed light signals; a host computer for performing steps S2-S4, sending scanning signals, reading the absorption peak of the PSD signal, and adjusting the voltage according to the absorption peak; a piezoelectric ceramic driver for performing step S5, deforming according to the adjusted voltage; and a lens assembly for performing steps S6-S7, changing the position of the piezoelectric ceramic to achieve optical path adjustment through deformation.

[0012] Preferably, the lens assembly further includes a lens bracket, and the piezoelectric ceramic is fixedly connected to the lens bracket.

[0013] Preferably, the miniaturized semiconductor laser further includes at least: a first polarizing beam splitter, a second polarizing beam splitter, an atomic gas cell, a deflector, and a high-reflection mirror; the first polarizing beam splitter is used to generate a saturated absorption light signal, the saturated absorption light signal is split into a probe light signal and a pump light signal by the second polarizing beam splitter, and the probe light signal continuously passes through the atomic gas cell, the high-reflection mirror, the atomic gas cell, the deflector, and the atomic gas cell to form a Z-shaped optical path.

[0014] Preferably, the miniaturized semiconductor laser further includes at least: the semiconductor laser also includes a first waveplate; the light passing through the isolator passes successively through the first waveplate and the first polarizing beam splitter; the polarization direction of the light is adjusted by adjusting the angle of the first waveplate, thereby adjusting the component ratio of transmitted P light and reflected S light, wherein the transmitted P light serves as the output light signal and the reflected S light serves as the saturated absorption light signal.

[0015] This invention proposes a miniaturized, integrated semiconductor laser with saturable absorption spectrum frequency stabilization. The laser receives a probe light signal via a PSD position detector and a scanning signal command is sent from a host computer. At this point, a saturable absorption peak appears in the probe light signal. Upon receiving the absorption peak signal, the host computer adjusts the voltage, thereby adjusting the angle of the piezoelectric deflector to achieve real-time optical path alignment adjustment. During frequency locking, the PSD signal can compensate for optical path alignment in real time, improving frequency locking stability and enhancing the saturable absorption effect. This effectively solves the application requirement of real-time optical path alignment compensation in the optical path of a frequency stabilization system during the frequency stabilization process of semiconductor lasers. Attached Figure Description

[0016] Figure 1 A schematic diagram of the optical path structure of a miniaturized semiconductor laser provided by the present invention; Figure 2 A schematic diagram of the back structure of a ceramic substrate for a miniaturized semiconductor laser provided by the present invention; Figure 3 A schematic diagram of the optical path structure of another miniaturized semiconductor laser provided by the present invention; Figure 4 This invention provides another real-time optical path adjustment process for a miniaturized semiconductor laser. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 Figure 1 This is a schematic diagram of the optical path structure of a miniaturized semiconductor laser. The semiconductor laser includes a light source 101, a collimating lens 102, a grating 103, an isolator 104, a first waveplate 105, a first polarizing beam splitter 106, a first reflecting mirror 107, a second waveplate 108, a second polarizing beam splitter 109, a second reflecting mirror 110, a third reflecting mirror 111, a fourth reflecting mirror 112, a fifth reflecting mirror 113, a third polarizing beam splitter 114, a right-angle prism 115, and an atomic gas cell 116.

[0019] In this embodiment, the light source 101 is a semiconductor light source, and the wavelength of the semiconductor light source is determined according to the material composition of the atomic gas chamber. For example, the wavelengths of rubidium atoms are 780nm and 795nm, and the wavelengths of cesium atoms are 852nm and 894nm.

[0020] In this embodiment, both the first waveplate 105 and the second waveplate 108 are half-waveplates.

[0021] In this embodiment, the first beam splitter 104, the second beam splitter 108, and the third beam splitter 114 are all 50:50 beam splitters.

[0022] In this embodiment, the first reflector 107, the second reflector 110, the third reflector 111, the fourth reflector 112, and the fifth reflector 113 are all the same in size and material.

[0023] In this embodiment, the emitted light from the light source 101 sequentially passes through a collimating lens 102, a grating 103, an isolator 104, a first waveplate 105, and a first polarizing beam splitter 106. The collimating lens 102 converts the emitted light from the light source into a quasi-parallel beam. The quasi-parallel beam is frequency-selected by the grating 103, and the frequency-selected light is then suppressed by the isolator 104 to prevent reflected light from interfering with the laser output or even damaging the laser. The light passing through the isolator 104 then passes through the first waveplate 105 and the first polarizing beam splitter 106. By adjusting the angle of the first waveplate 105, the polarization direction of the light is adjusted, thereby adjusting the proportion of transmitted P-light and reflected S-light components, achieving the first distribution of optical power. The high-power transmitted P-light serves as the output light signal, and the low-power reflected S-light serves as the saturated absorption light signal.

[0024] The saturated absorbed light signal passes sequentially through the first reflecting mirror 107, the second waveplate 108, and the second polarizing beam splitter 109. The light signal after passing through the second polarizing beam splitter is split into two paths. The angle of the second waveplate 108 is adjusted to regulate the polarization direction of the light, thereby adjusting the proportion of transmitted P-light and reflected S-light components, achieving a second distribution of light power. The light signal after passing through the second polarizing beam splitter is then divided into a probe light signal and a pump light signal.

[0025] The probe light passes through atomic gas cell 116, second reflector 110, atomic gas cell 116, third reflector 111, atomic gas cell 116, and atomic gas cell 116 in succession. The probe light is P-beam. The probe light transmitted through the third polarizing beam splitter 114 hits the internal reflection right angle prism 115 and is finally refracted onto the photodetector 117 of the semiconductor laser.

[0026] The pump light, which is an S-beam, passes through the fourth reflector 112 and the fifth reflector 113 in succession. After being reflected by the third polarizing beam splitter 114, it collidees with the probe light in the atomic gas chamber 116. It can be understood that after being reflected by the third polarizing beam splitter 114, the pump light passes through the atomic gas chamber 116, the third reflector 110, the atomic gas chamber 116, and the second reflector 111 in sequence to form a Z-shaped optical path. The direction of the pump light is opposite to that of the probe light. In the atomic gas chamber 116, the pump light and the probe light collide. Through the principle of saturated absorption, the pump light excites specific velocity group atoms that resonate with the laser. The population of these excited atoms decreases in the ground state and increases in the excited state.

[0027] Since the pump light has consumed atoms of a specific velocity group, the absorption of the probe light on these atoms is weakened. The signal received by the photodetector 117 is amplified by the transimpedance amplifier circuit to form a voltage signal. This signal is adjusted by the error feedback circuit to keep the laser frequency locked at the atomic resonance frequency, so that the residual frequency fluctuation is reduced to a stable output at a specific frequency, thus achieving saturated absorption frequency stabilization.

[0028] Figure 2 This invention provides a schematic diagram of the back structure of a ceramic substrate for a miniaturized semiconductor laser, as shown below. Figure 2 As shown, the back of the ceramic substrate of the semiconductor laser is provided with a photodetector 117, a thermistor 118, and a heating coil 119. The combination of the thermistor 118 and the heating coil 119 can heat the atomic gas cell, enhance the activity of the atoms to enhance the frequency stabilization effect, and enhance the saturation absorption effect by folding the optical path (taking a Z-shaped one as an example). Under space-constrained conditions, the frequency stabilization effect is enhanced. Compared with the existing saturation absorption laser, the volume is greatly reduced while ensuring frequency locking stability.

[0029] The front side of the ceramic substrate is provided with a collimating lens 102, a grating 103, an isolator 104, a first wave plate 105, a first polarizing beam splitter 106, a first reflecting mirror 107, a second wave plate 108, a second polarizing beam splitter 109, a second reflecting mirror 110, a third reflecting mirror 111, a fourth reflecting mirror 112, a fifth reflecting mirror 113, a third polarizing beam splitter 114, a right-angle prism 115, and an atomic gas cell 116.

[0030] This embodiment employs a miniaturized, integrated saturable absorption spectrum-stabilized semiconductor laser, using a zigzag optical path (taking a Z-shaped design as an example) as the saturable absorption optical path to enhance the stability of saturable absorption frequency locking within a limited space. By integrating the saturable absorption frequency locking optical path internally to the light source, the overall system size is significantly reduced. This effectively solves the problems of space constraints, structural complexity, and high cost associated with building a frequency stabilization system optical path during semiconductor laser frequency stabilization. It is suitable for high-precision measurement applications requiring space constraints, portability, and on-site deployment.

[0031] Example 2 Figure 3 This invention provides a schematic diagram of the optical path structure of another miniaturized semiconductor laser. The semiconductor laser includes a light source 101, a collimating lens 102, a grating 103, an isolator 104, a first waveplate 105, a first polarizing beam splitter 106, a first high-reflection mirror 107, a second waveplate 108, a second polarizing beam splitter 109, a deflecting mirror 110, a second high-reflection mirror 111, a third high-reflection mirror 112, a fourth first high-reflection mirror 113, a third polarizing beam splitter 114, a position detector 115, an atomic gas cell 116, and a host computer 117. This embodiment adds a host computer 117 to the first embodiment. After receiving the absorption peak signal, the host computer 117 adjusts the voltage to correspondingly lengthen or shorten the piezoelectric ceramic, thereby adjusting the angle of the deflecting mirror 110 to achieve real-time adjustment of the optical path alignment and enhance the saturated absorption effect.

[0032] In this embodiment, the wavelength range of the optical signal detected by the position detector 115 is 400-1100nm, and the position detector sensor 115 is a two-dimensional PSD with a resolution of not less than 0.01mm.

[0033] In this embodiment, the range of voltage adjustment by the host computer is 0-100V, and the adjustment accuracy is 0.1V.

[0034] In this embodiment, the maximum deformation of the piezoelectric ceramic is 50 μm.

[0035] In this embodiment, the deflecting mirror 110 is a convex lens with a focal length range of 3-8mm.

[0036] Figure 4 The present invention provides another real-time optical path adjustment process for a miniaturized semiconductor laser, which is based on closed-loop control of optical path adjustment using a position detector (PSD): First, the PSD detects saturated and absorbed light signals. After the host computer sends a scanning signal, it reads the absorption peak of the PSD and adjusts the voltage according to the absorption peak to drive the piezoelectric ceramic to deform, thereby changing the position of the lens and finally completing the optical path adjustment.

[0037] This process is a closed-loop control flow for optical path adjustment based on a PSD (Position Sensitive Detector). The specific steps are as follows: 401. Signal Detection: The PSD detects saturated and absorbed light signals, serving as the initial input for system feedback. 402. Command Issuance: The host computer sends a scan signal to the lower-level module, initiating the optical path adjustment control flow. 403. Signal Reading: The host computer reads the signal absorption peak output by the PSD. This absorption peak reflects the characteristic position or intensity distribution of the light signal in the current optical path. 404. Voltage Adjustment: Based on the read absorption peak parameters (such as position and intensity), the host computer calculates and adjusts the output voltage to drive the subsequent actuator. 405. Piezoelectric Ceramic Deformation: The adjusted voltage is applied to the piezoelectric ceramic, causing it to undergo corresponding mechanical deformation (inverse piezoelectric effect) according to the voltage change. In step 405, a magnetostrictive material can also be selected. Under the influence of current, a magnetic field is generated, causing the magnetostrictive rod to deform, fulfilling applications requiring long strokes and high thrust. Step 405 can also utilize an electrostatic comb structure, employing electrostatic attraction to change the comb tooth spacing under voltage. The stationary comb teeth remain stationary while the movable comb teeth move, generating precise thrust. Thanks to the development of MEMS technology, the comb structure has excellent application prospects in future miniaturization. On silicon-based MEMS, photolithography is used to deposit metal pads on the structure, significantly reducing the device size. For the three adjustment methods, each modulation method has its advantages and disadvantages, depending on the application scenario. For current laser products, piezoelectric ceramic control offers certain advantages in control precision. 406. Lens Position Change: The deformation of the piezoelectric ceramic causes a change in the position or orientation of the lens device, thereby adjusting the lens parameters in the optical path (such as focal length, optical axis alignment, etc.). 407. Optical Path Adjustment Completed: By changing the lens position, dynamic adjustment of the entire optical path is achieved, enabling the optical signal to achieve the expected transmission or focusing effect, forming a complete closed-loop control.

[0038] This embodiment also provides an optical path adjustment device based on PSD signals, comprising: a position detector for performing step 401 to detect saturated and absorbed light signals; a host computer for performing steps 402-404, sending scanning signals, reading the absorption peak of the PSD signal, and adjusting the voltage according to the absorption peak; a piezoelectric ceramic driver for performing step 405, deforming according to the adjusted voltage; and a lens assembly for performing steps 406-407, changing the position through the deformation of the piezoelectric ceramic to achieve optical path adjustment.

[0039] The aforementioned optical path adjustment device is applied to a miniaturized semiconductor laser as described in Embodiment 1. This miniaturized semiconductor laser further includes at least: a first polarizing beam splitter, a second polarizing beam splitter, an atomic gas cell, a deflector, and a high-reflection mirror. The first polarizing beam splitter generates a saturated absorption light signal. This saturated absorption light signal is split into a probe light signal and a pump light signal by the second polarizing beam splitter. The probe light signal continuously passes through the atomic gas cell, the high-reflection mirror, the atomic gas cell, the deflector, and the atomic gas cell to form a Z-shaped optical path. The miniaturized semiconductor laser also includes at least: a first waveplate; light passing through the isolator passes sequentially through the first waveplate and the first polarizing beam splitter; the polarization direction of the light is adjusted by adjusting the angle of the first waveplate, thereby adjusting the component ratio of transmitted P-light and reflected S-light. The transmitted P-light serves as the output light signal, and the reflected S-light serves as the saturated absorption light signal.

[0040] In this embodiment, the position detector sensor is a two-dimensional PSD with a resolution of not less than 0.01 mm. The lens assembly also includes a lens bracket. The piezoelectric ceramic is fixedly connected to the lens bracket, and the piezoelectric ceramic drives the lens position adjustment through the lens bracket.

[0041] In this embodiment, the pressure point ceramic can also be a magnetostrictive material. Using Galfenol, the magnetostrictive material is easy to integrate. The magnetostrictive material is indirectly driven by a magnetic field driven by an electromagnetic coil, with the magnetic field generated by voltage-controlled current. To precisely control the deformation of the magnetostrictive material, it needs to be filled into a cylindrical metal structure. The magnetic field generated by voltage-controlled current drives the magnetostrictive material to produce a specific deformation along the axial direction.

[0042] In this embodiment, the pressure point ceramic can also be an electrostatic comb structure. Under the action of voltage, an attractive force is generated between the electrodes to drive the structural displacement and adjust the lens. Electrostatic comb structures are mostly made using MEMS technology, which is small in size and has good linearity. They have certain advantages in the field of precision measurement and control and have a great driving effect on the development of high-precision control. The high precision generated by the comb structure also means that the range of thrust generated is small, which is suitable for fine-tuning processes.

[0043] This invention proposes a miniaturized integrated semiconductor laser with saturated absorption spectrum frequency stabilization. The laser receives a probe light signal through a PSD position detector and sends a scanning signal command through a host computer. At this time, the probe light signal will show a saturated absorption peak. After receiving the absorption peak signal, the host computer adjusts the voltage to make the piezoelectric ceramic correspondingly elongate or shorten, thereby adjusting the angle of the piezoelectric deflection mirror, realizing real-time adjustment of the optical path alignment and enhancing the saturated absorption effect.

[0044] This invention proposes a miniaturized, integrated semiconductor laser with saturable absorption spectrum frequency stabilization. During frequency locking, it can compensate for optical path alignment in real time via PSD signals, improving frequency locking stability. This effectively solves the application requirement of real-time optical path alignment compensation in the optical path of a frequency stabilization system during the frequency stabilization process of semiconductor lasers. It is suitable for high-precision measurement fields where space is limited, portability is required, and on-site deployment is necessary.

[0045] It should be noted that the technical features in the above embodiments can be combined arbitrarily, and the resulting technical solutions all fall within the protection scope of this application. Furthermore, in this document, terms such as "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for adjusting the optical path based on saturated absorption spectrum and position detector feedback, characterized in that, Includes the following steps: S1. The position detector detects saturated and absorbed light signals; S2. The host computer sends a scanning signal; S3. The host computer reads the absorption peak of the position detector signal; S4. Adjust the voltage according to the absorption peak; S5. The piezoelectric ceramic deforms according to the adjusted voltage; S6. The deformation of the piezoelectric ceramic causes a change in the position of the deflection lens; S7. The optical path is adjusted by changing the position of the lens.

2. The method according to claim 1, characterized in that, In step S1, the wavelength range of the optical signal detected by the position detector is 400-1100nm.

3. The method according to claim 1, characterized in that, In step S4, the range of the adjusted voltage is 0-100V, and the adjustment accuracy is 0.1V.

4. The method according to claim 1, characterized in that, In step S5, the maximum deformation of the piezoelectric ceramic is 50 μm.

5. The method according to claim 1, characterized in that, In step S6, the deflecting lens is a convex lens with a focal length range of 3-8mm.

6. An optical path adjustment device based on a PSD signal, the device being applied to a miniaturized semiconductor laser, characterized in that, include: A position detector is used to perform step S1 to detect saturated and absorbed light signals; The host computer is used to execute steps S2-S4, send out scanning signals, read the absorption peak of the PSD signal, and adjust the voltage according to the absorption peak; A piezoelectric ceramic actuator is used to perform step S5, which causes deformation according to the regulated voltage; The lens assembly is used to perform steps S6-S7, changing its position by deforming the piezoelectric ceramic to achieve optical path adjustment.

7. The apparatus according to claim 6, characterized in that, The lens assembly also includes a lens bracket, and the piezoelectric ceramic is fixedly connected to the lens bracket.

8. The apparatus according to claim 6, characterized in that, The miniaturized semiconductor laser further includes at least: a first polarizing beam splitter, a second polarizing beam splitter, an atomic gas cell, a deflecting mirror, and a high-reflection mirror; the first polarizing beam splitter is used to generate a saturated absorption light signal, the saturated absorption light signal is split into a probe light signal and a pump light signal by the second polarizing beam splitter, and the probe light signal continuously passes through the atomic gas cell, the high-reflection mirror, the atomic gas cell, the deflecting mirror, and the atomic gas cell to form a Z-shaped optical path.

9. The apparatus according to claim 8, characterized in that, The miniaturized semiconductor laser further includes at least: the semiconductor laser also includes a first waveplate; the light passing through the isolator passes successively through the first waveplate and the first polarizing beam splitter; the polarization direction of the light is adjusted by adjusting the angle of the first waveplate, thereby adjusting the component ratio of transmitted P light and reflected S light, wherein the transmitted P light serves as the output light signal and the reflected S light serves as the saturated absorption light signal.

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