Dual f-p enhanced cavity for boosting power gain multiplication

Abstract

This invention discloses a dual F-P enhancement cavity for improving power gain. The dual F-P enhancement cavity includes a laser unit, a dual F-P enhancement cavity unit, a resonance condition locking unit, and a frequency locking unit. The laser unit generates and modulates laser light, and the modulated laser light is matched with the spatial mode of the dual F-P enhancement cavity unit before being input into the dual F-P enhancement cavity unit. The dual F-P enhancement cavity unit includes F-P cavity 1 and F-P cavity 2. The resonance condition locking unit adjusts the phase relationship of the incident laser light in F-P cavity 1 and F-P cavity 2 to satisfy the resonance condition of the dual F-P enhancement cavity, thereby improving the power gain. The frequency locking unit detects the cavity mode signal of the dual F-P enhancement cavity unit and demodulates it to obtain an error signal reflecting the deviation between the laser frequency and the resonance frequency of the dual F-P enhancement cavity, and adjusts the output frequency of the laser to achieve frequency locking. This invention can significantly improve the laser power intensity in F-P cavity 1.

Description

Technical Field

[0001] This invention belongs to the field of laser spectroscopy technology and relates to a dual FP enhancement cavity for improving power gain. Background Technology

[0002] Spectroscopic detection technology, with its advantages of high sensitivity, rapid response, and no need for sample consumption, has become one of the mainstream methods for trace gas detection. Gas detection sensitivity is directly proportional to the excitation light power; therefore, increasing the laser power is key to optimizing system detection performance. Resonant cavity enhancement technology is one of the commonly used gas spectral enhancement techniques. When the resonance condition is met, the laser will form constructive interference within the resonant cavity, thereby accumulating high laser power.

[0003] Power gain is a key performance indicator for resonant cavities, and current research mainly focuses on improving this factor by employing ultra-high reflectivity cavity mirrors. While V-shaped cavity structures can achieve optical feedback frequency locking, they introduce additional optical losses, limiting the accumulation of laser power within the cavity. Compared to V-shaped cavities, FP cavities can achieve higher power gain. However, the reduced reflectivity of the input mirror in FP cavities negatively impacts the maximum power gain, resulting in a narrower tunable range. Furthermore, due to limitations imposed by material absorption and scattering, the reflectivity of the cavity mirrors faces an insurmountable upper limit, thus creating a bottleneck for improving the power gain of resonant cavities.

[0004] Therefore, it is necessary to study a novel resonant cavity structure with a high power gain. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a dual FP enhancement cavity for increasing power gain. The FP cavity 1 and FP cavity 2 are composed of three coaxially parallel high-reflectivity mirrors. By adjusting the phase relationship of the incident laser in FP cavity 1 and FP cavity 2, the laser power intensity in FP cavity 1 can be significantly increased.

[0006] The present invention adopts the following technical solution.

[0007] The first aspect of the present invention provides a dual FP enhancement cavity for improving power gain, wherein the dual FP enhancement cavity includes a laser unit, a dual FP enhancement cavity unit, a resonance condition locking unit, and a frequency locking unit; The laser unit is used to generate and modulate laser light, and the modulated laser light is matched with the spatial pattern of the dual FP enhancement cavity unit and then input into the dual FP enhancement cavity unit. The dual FP enhancement cavity unit includes FP cavity 1 and FP cavity 2, which are used to reflect the incident laser. The resonance condition locking unit is used to collect the reflected light intensity of the dual FP enhancement cavity unit in real time and compare it with the reference reflected light intensity under the resonance condition to obtain the deviation signal. Based on the deviation signal, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the resonance condition of the dual FP enhancement cavity to improve the power gain. The frequency locking unit is used to detect the cavity mode signal of the dual FP enhancement cavity unit and demodulate it to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. The output frequency of the laser in the laser unit is adjusted according to the error signal to achieve frequency locking.

[0008] Preferably, the laser unit includes a laser, an electro-optic modulator, and a lens group; The laser is used to generate a single-frequency laser. The electro-optic modulator is used to generate phase modulation sidebands and modulate the laser light generated by the laser. The lens group is used to match the spatial pattern of the modulated laser and the dual FP intensifier cavity unit before inputting it into the dual FP intensifier cavity unit.

[0009] Preferably, the lens group is an achromatic lens group, which is mounted on a multi-axis displacement stage. By precisely controlling the output beam, the modulated laser spot emitted by the fiber laser is made to coincide with the fundamental mode waist spot of the dual FP enhancement cavity unit.

[0010] Preferably, matching the modulated laser with the spatial mode of the dual FP enhancement cavity unit includes: Spatial mode matching is performed on the modulated laser incident on the dual FP enhancement cavity unit so that the modulated laser matches the fundamental mode of FP cavity 1; and spatial mode matching is also performed on the laser that is reflected by the high-reflectivity mirror M3 in the dual FP enhancement cavity unit and then incident on FP cavity 1 again so that it also matches the fundamental mode of FP cavity 1.

[0011] Preferably, the dual FP enhancement cavity unit includes three high-reflectivity mirrors M1, M2 and M3 placed coaxially and parallel; Among them, high-reflection lenses M1 and M2 form FP cavity 1, and high-reflection lenses M2 and M3 form FP cavity 2; The incident laser propagates in a loop within FP cavity 1 and FP cavity 2. When the resonant condition of the dual FP enhanced cavity is met, high laser power is accumulated in FP cavity 1.

[0012] Preferably, the three high-reflectivity lenses M1, M2 and M3 are mounted on a multi-axis high-stability frame, and annular piezoelectric ceramics are attached to the back of the lenses. Under the drive of a high-voltage signal, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the dual FP enhanced cavity resonance condition.

[0013] Preferably, the dual FP-enhanced cavity resonance condition is the phase condition when the ratio of the forward propagation optical field in FP cavity 1 to the forward propagation optical field of the conventional FP cavity reaches its maximum value, wherein the ratio of the forward propagation optical field in FP cavity 1 to the forward propagation optical field of the conventional FP cavity is:

[0014] in, This represents the light reflectivity of the cavity mirror. This represents the light transmittance of the endoscope. and These represent the phases of the laser as it travels back and forth once within FP cavity 1 and FP cavity 2, respectively.

[0015] Preferably, the resonant condition of the dual FP enhanced cavity is: ,

[0016] in, , It is an integer. and These represent the phases of the laser as it travels back and forth once within FP cavity 1 and FP cavity 2, respectively.

[0017] Preferably, the frequency locking unit includes a photodetector, a frequency locking module, and a feedback controller; The photodetector is used to detect the cavity mode signal of the dual FP enhanced cavity; The frequency locking module is used to demodulate and filter the cavity mode signal to generate an error signal that reflects the deviation between the laser frequency and the resonant frequency of the dual FP enhanced cavity. The feedback controller is used to adjust the output frequency of the laser in the laser unit according to the error signal.

[0018] Preferably, the process by which the frequency locking module demodulates and filters the cavity mode signal to generate an error signal is as follows: First, a sinusoidal modulation signal is applied to the electro-optic modulator in the laser unit to create a modulation sideband; Secondly, based on the modulation sideband, the cavity mode signal is demodulated using an internally generated signal with the same frequency as the sinusoidal modulation signal, and redundant signal components are filtered out by a low-pass filter to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. The error signal is:

[0019]

[0020] in, This represents the reflection function of the optical field in a dual-FP cavity. Indicates the incident laser angular frequency. and Indicates the free spectral path of FP cavity 1 and FP cavity 2. for The complex conjugate, The modulation frequency of the phase modulation sideband generated by the electro-optic modulator. This represents the light reflectivity of the cavity mirror.

[0021] Preferably, the feedback controller includes a fast controller and a slow controller. The error signal is dynamically PID-regulated by the fast controller and the slow controller and applied to the acousto-optic modulator and piezoelectric ceramic inside the laser to adjust the laser output frequency.

[0022] Preferably, the outer cavity of the dual FP enhanced cavity is made of Invar steel, and the cavity is wrapped with a temperature control layer to stabilize the temperature within a set range, and a graded temperature control system is used for dynamic compensation and adjustment.

[0023] Preferably, the relative positions of the incident laser and the dual FP enhancement cavity are precisely adjusted according to the cavity mode signal of the dual FP enhancement cavity unit to ensure that no high-order mode signal is generated and to improve the coupling efficiency of the incident laser.

[0024] A second aspect of the present invention provides a method for operating the dual FP enhancement cavity, comprising: The laser unit generates and modulates laser light, and then inputs the modulated laser light into the dual FP enhancement cavity unit after matching the spatial mode of the dual FP enhancement cavity unit. The dual FP enhancement cavity unit reflects the incident laser. The resonance condition locking unit collects the intensity of the reflected light from the dual FP enhancement cavity unit in real time and compares it with the reference reflected light intensity under the resonance condition to obtain the deviation signal. Based on the deviation signal, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the resonance condition of the dual FP enhancement cavity to improve the power gain. The frequency locking unit detects the cavity mode signal of the dual FP enhancement cavity unit and demodulates it to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. Based on the error signal, the output frequency of the laser in the laser unit is adjusted to achieve frequency locking.

[0025] A third aspect of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0026] A fourth aspect of the present invention relates to a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0027] Compared with the prior art, the beneficial effects of the present invention include at least the following: This invention relates to a novel dual-FP enhancement cavity structure, consisting of three coaxially parallel high-reflectivity mirrors forming FP cavity 1 and FP cavity 2. The power gain can be increased by adjusting the phase relationship of the incident laser within FP cavity 1 and FP cavity 2, when the resonance condition (the phase of the laser during one round trip within FP cavity 1) is met. The phase of one round trip within FP cavity 2 When the power gain is up to 4 times that of a conventional FP cavity, its power gain is at most 4 times that of a conventional FP cavity.

[0028] The novel enhancement cavity structure with high power gain proposed in this invention avoids the dependence on ultra-high reflectivity cavity mirrors used in existing resonant cavity enhancement technologies to improve power gain. This structure is expected to break through the current power gain limit of resonant cavities. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the dual FP enhancement cavity structure used in this invention to improve power gain.

[0030] Figure 2 This is the error signal for the dual FP enhancement cavity. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0032] Embodiment 1 of the present invention provides a dual FP enhancement cavity for improving power gain, such as Figure 1 As shown, the dual FP enhancement cavity includes a laser unit, a dual FP enhancement cavity unit, a resonance condition locking unit, and a frequency locking unit; the units are interconnected through optical / electronic control to achieve signal transmission and feedback control, forming a closed-loop resonant cavity power enhancement system.

[0033] The laser unit is used to generate and modulate laser light, and the modulated laser light is matched with the spatial pattern of the dual FP enhancement cavity unit and then input into the dual FP enhancement cavity unit. More preferably, the laser unit includes a laser, an electro-optic modulator, and a lens group; The laser is used to generate a single-frequency laser. The electro-optic modulator is used to generate phase modulation sidebands and modulate the laser light generated by the laser. The lens group is used to match the spatial pattern of the modulated laser and the dual FP intensifier cavity unit before inputting it into the dual FP intensifier cavity unit.

[0034] The lens group is an achromatic lens group, which is mounted on a multi-axis displacement stage. By precisely controlling the output beam, the modulated laser spot emitted by the fiber laser is made to coincide with the waist spot of the fundamental mode of the dual FP enhancement cavity unit.

[0035] The process of matching the modulated laser with the spatial pattern of the dual FP enhanced cavity unit includes: Spatial mode matching is performed on the modulated laser incident on the dual FP enhancement cavity unit so that the modulated laser matches the fundamental mode of FP cavity 1; and spatial mode matching is also performed on the laser that is reflected by the high-reflectivity mirror M3 in the dual FP enhancement cavity unit and then incident on FP cavity 1 again so that it also matches the fundamental mode of FP cavity 1.

[0036] That is, the first spatial mode matching between the modulated laser and FP cavity 1, and the second spatial mode matching between the laser reflected by the high-reflectivity mirror M3 and FP cavity 1.

[0037] A conventional FP cavity requires a single spatial mode matching between the incident laser and the FP cavity, while a dual FP cavity requires two spatial mode matching processes. The dual FP cavity accumulates laser power only in FP cavity 1. In addition to the spatial mode matching between the incident laser and FP cavity 1, the laser reflected by cavity mirror 3 (high reflectivity mirror M3) also needs to be spatially matched with FP cavity 1.

[0038] Specifically, the laser unit includes a 532 nm single-frequency fiber laser, an electro-optic modulator, and a lens group. The fiber laser has a linewidth of 8 kHz and an initial laser power of 50 mW; within the 10 Hz-10 MHz range, the root mean square of the output power is less than 0.04%, and the output power exhibits good stability.

[0039] The electro-optic modulator is a resonant electro-optic modulator, which requires ensuring that the polarization state of the incident laser is consistent with that of the wedge-angle crystal modulator to maximize phase modulation efficiency. High-frequency modulation can avoid the influence of low-frequency noise; in this embodiment, the modulation frequency is 20 MHz. While ensuring laser frequency stabilization, appropriately reducing the modulation depth can increase the power gain of the resonant cavity; in this embodiment, the modulation depth is 0.2.

[0040] The lens group is used to achieve spatial mode matching between the laser beam and the dual FP enhancement cavity. In this embodiment, a pair of achromatic lenses with a focal length of 80 cm is used. The lens group is mounted on a multi-axis displacement stage, which can precisely control the output beam to achieve the overlap between the laser spot emitted by the fiber laser and the fundamental mode waist spot of the dual FP enhancement cavity.

[0041] The dual FP enhancement cavity unit includes FP cavity 1 and FP cavity 2. The power gain can be increased by adjusting the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 so that the phase relationship satisfies the dual FP enhancement cavity resonance condition. The resonance condition locking unit is used to maintain the resonance condition of the dual FP cavities. It compares the real-time acquired reflected light intensity with the reference (based on the reflected light intensity under the resonance condition) to obtain the deviation signal, and then uses the deviation signal to control the phase relationship between FP cavity 1 and FP cavity 2. Specifically, the dual FP enhancement cavity unit includes FP cavity 1 and FP cavity 2 to reflect the incident laser; the resonance condition locking unit collects the intensity of the reflected light from the dual FP enhancement cavity unit in real time and compares it with the reference reflected light intensity under the resonance condition to obtain a deviation signal. Based on the deviation signal, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the resonance condition of the dual FP enhancement cavity to improve the power gain.

[0042] More preferably, the dual FP enhancement cavity unit includes three high-reflectivity mirrors M1, M2 and M3 placed coaxially and parallel; Among them, high-reflection lenses M1 and M2 form FP cavity 1, and high-reflection lenses M2 and M3 form FP cavity 2; The incident laser propagates in a loop within FP cavity 1 and FP cavity 2. When the resonant condition of the dual FP enhanced cavity is met, high laser power is accumulated in FP cavity 1.

[0043] The three high-reflectivity lenses M1, M2 and M3 are mounted on a multi-axis high-stability frame. Annular piezoelectric ceramics are attached to the back of the lenses. Under high-voltage signal drive, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the dual FP enhanced cavity resonance condition.

[0044] Specifically, a high-voltage signal drives a ring-shaped piezoelectric ceramic, and by controlling the ring-shaped piezoelectric ceramic, the length of FP cavity 2 is changed, thereby changing the relative phase relationship between FP cavity 1 and FP cavity 2.

[0045] The dual FP-enhanced cavity resonance condition is the phase condition when the ratio of the forward propagation optical field in FP cavity 1 to the forward propagation optical field of the conventional FP cavity reaches its maximum value. The ratio of the forward propagation optical field in FP cavity 1 to the forward propagation optical field of the conventional FP cavity is:

[0046] in, This represents the light reflectivity of the cavity mirror. This represents the light transmittance of the endoscope. and These represent the phases of the laser as it travels back and forth once within FP cavity 1 and FP cavity 2, respectively.

[0047] The resonant condition for the dual FP enhanced cavity is: ,

[0048] in, , It is an integer. and These represent the phases of the laser as it travels back and forth once within FP cavity 1 and FP cavity 2, respectively.

[0049] The resonant condition locking unit includes a photodetector, a phase locking module, and a feedback controller; The photodetector is used to detect the intensity of reflected light from the dual FP enhancement cavity; The phase-locking module is used to compare the real-time reflected light intensity with the reflected light intensity under resonance conditions to obtain a deviation signal; The feedback controller is used to adjust the piezoelectric ceramic of the cavity mirror 3 according to the deviation signal. Specifically, the resonance condition locking unit generates a high-voltage drive signal according to the deviation signal, which acts on the annular piezoelectric ceramic of the high-reflectivity mirror M3. By changing the length of the FP cavity 2, the relative phase relationship between the FP cavity 1 and the FP cavity 2 is adjusted so that the phase relationship satisfies the resonance condition of the dual FP enhanced cavity, thereby increasing the power gain.

[0050] The frequency locking unit is used to detect the cavity mode signal of the dual FP enhancement cavity unit and demodulate it to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. The output frequency of the laser in the laser unit is adjusted according to the error signal to achieve frequency locking.

[0051] Specifically, the dual FP enhancement cavity unit consists of three high-reflectivity mirrors (M1, M2, and M3), forming FP cavity 1 and FP cavity 2 respectively. FP cavity 1 is 25 cm long, FP cavity 2 is 2 cm long, and the overall length of the dual FP enhancement cavity is 27 cm.

[0052] At the 532 nm wavelength, the reflectivity of the three high-reflectivity lenses is 99.9%, and the lens diameter is 25.4 cm.

[0053] To eliminate the effects of temperature changes and stress on the high-reflectivity lenses, three high-reflectivity lenses are mounted on a multi-axis high-stability frame to improve the stability of the cavity. Ring-shaped piezoelectric ceramics are attached to the back of the lenses, allowing for phase adjustment of the laser in FP cavity 1 and FP cavity 2 under high-voltage signal drive.

[0054] The outer cavity of the dual FP reinforced cavity is made of Invar steel, with a coefficient of thermal expansion of approximately 1-1.8×10⁻⁶. -6 With a temperature change of 1℃, the deformation is less than 0.5 μm. The cavity is wrapped with a temperature control layer to stabilize the temperature in the range of 25 ± 0.1 ℃, with a temperature fluctuation of ≤ ±0.05 ℃, and a graded temperature control system is used for dynamic compensation and adjustment.

[0055] Observe the cavity mode signal of the dual FP enhancement cavity during the scanning process, and precisely adjust the relative position of the incident laser and the dual FP enhancement cavity to ensure that no higher-order mode signal is generated (at which point the power gain of the dual FP enhancement cavity is optimal), thereby improving the coupling efficiency of the incident laser.

[0056] More preferably, the frequency locking unit includes a photodetector, a frequency locking module, and a feedback controller; The photodetector is used to detect the cavity mode signal of the dual FP enhanced cavity; The frequency locking module is used to demodulate and filter the cavity mode signal to generate an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhanced cavity. The process is as follows: First, a sinusoidal modulation signal is applied to the electro-optic modulator in the laser unit to create a modulation sideband; Secondly, based on the modulation sideband, the cavity mode signal is demodulated using an internally generated signal with the same frequency as the sinusoidal modulation signal, and redundant signal components are filtered out by a low-pass filter to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. The normalized error signal of the dual FP cavity is expressed as:

[0057]

[0058] in, This represents the reflection function of the optical field in a dual-FP cavity. Indicates the incident laser angular frequency. and Indicates the free spectral path of FP cavity 1 and FP cavity 2. for The complex conjugate, The modulation frequency of the phase modulation sideband generated by the electro-optic modulator. This represents the light reflectivity of the cavity mirror.

[0059] The feedback controller is used to adjust the output frequency of the laser in the laser unit according to the error signal.

[0060] The feedback controller includes a fast controller and a slow controller. The error signal is dynamically PID-regulated by the fast controller and the slow controller and applied to the acousto-optic modulator and piezoelectric ceramic inside the laser to adjust the laser output frequency.

[0061] More preferably, the outer cavity of the dual FP enhanced cavity is made of Invar steel, and the cavity is wrapped with a temperature control layer to stabilize the temperature within a set range, and a graded temperature control system is used for dynamic compensation and adjustment.

[0062] Observe the cavity mode signal of the dual FP enhancement cavity unit during the scanning process, and precisely adjust the relative position of the incident laser and the dual FP enhancement cavity according to the cavity mode signal to ensure that no high-order mode signal is generated (at this time, the power gain of the dual FP enhancement cavity is optimal) and improve the coupling efficiency of the incident laser.

[0063] Specifically, the frequency locking unit includes a photodetector, a frequency locking module, and a feedback controller. The photodetector is used to detect the reflected signal from the dual FP enhancement cavity, and the detector bandwidth is 50 MHz.

[0064] The frequency locking module first applies a 20 MHz sinusoidal modulation signal to the electro-optic modulator to create a modulation sideband. Next, the frequency locking module acquires the reflected signal to be demodulated and demodulates it using an internally generated 20 MHz same-frequency signal. Then, it filters out excess signal components using a low-pass filter (cutoff frequency of 1 MHz) to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency, such as... Figure 2 As shown.

[0065] The error signal, through dynamic PID control of a fast and slow controller, acts on the acousto-optic modulator and piezoelectric ceramic inside the laser to adjust the laser's output frequency. The piezoelectric ceramic has a tuning range of 10-15 GHz, a tuning bandwidth of 10 kHz, and a resolution of less than 1 kHz; the acousto-optic modulator has a tuning range of ±3-5 MHz, a tuning bandwidth of 500 kHz, and a resolution of less than 100 Hz. By employing a combination of slow and fast feedback to adjust the laser's output frequency, the resonant state of the incident laser and the dual FP enhancement cavities can be maintained.

[0066] Within a single laser scanning cycle, only one cavity mode signal is controlled to exist during the scanning cycle, ensuring that the cavity mode signal appears in the middle of the scanning cycle. In the locked state, the power fluctuation of the dual FP enhancement cavity is less than 3%.

[0067] Power gain of the resonant cavity The calculation formula is: ; in, This refers to the internal power of the resonant cavity. The incident power of the resonant cavity is denoted as .

[0068] Tests showed that under an incident laser power of 50 mW, the laser power intensity in FP cavity 1 was approximately 200 W, and the power gain of the dual FP enhancement cavity was approximately 4000 times, reaching the power gain of an FP cavity composed of ultra-high reflectivity lenses (above 0.9999).

[0069] Under the same parameters, the laser power intensity in a conventional FP cavity is approximately 65 W, with a power gain of approximately 1300 times. The power gain of a dual FP enhancement cavity is more than three times that of a conventional FP cavity.

[0070] Therefore, this invention proposes a novel resonant cavity structure with high power gain, avoiding the dependence of current high power gain on ultra-high reflectivity cavity mirrors, and is expected to break through the power gain limit of resonant cavities.

[0071] Embodiment 2 of the present invention provides an operating method for a dual FP enhancement cavity for improving power gain, including starting the laser unit to generate a phase-modulated single-frequency laser; adjusting the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 to satisfy the dual FP enhancement cavity resonance condition; and starting the frequency locking unit to lock the incident laser with the dual FP enhancement cavities, accumulating high-power laser in FP cavity 1, as detailed below: The laser unit generates and modulates laser light, and then inputs the modulated laser light into the dual FP enhancement cavity unit after matching the spatial mode of the dual FP enhancement cavity unit. In this embodiment, the laser unit includes a laser, an electro-optic modulator, and a lens group. The laser is used to generate a single-frequency laser; the electro-optic modulator is used to generate phase modulation sidebands; and the lens group is used to achieve spatial mode matching between the incident laser and the dual FP enhancement cavity.

[0072] The laser emitted from the laser, along the spatial optical path, includes, in sequence, an electro-optic modulator, a lens group, and a dual FP enhancement cavity.

[0073] The spatial pattern matching requires that the incident laser and the FP cavity 1 be spatially matched, and that the laser reflected by the high-reflectivity mirror M3 be spatially matched with the FP cavity 1.

[0074] The dual FP enhancement cavity unit reflects the incident laser. The resonance condition locking unit obtains the deviation signal by comparing the real-time collected reflected light intensity with the reference (based on the reflected light intensity under resonance conditions). The deviation signal is then used to adjust the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 so that the phase relationship satisfies the dual FP enhancement cavity resonance condition, thereby improving the power gain. In this embodiment, the dual FP enhancement cavity unit includes three coaxially parallel high-reflectivity mirrors (M1, M2 and M3). High-reflectivity mirrors M1 and M2 form FP cavity 1, and high-reflectivity mirrors M2 and M3 form FP cavity 2. The laser circulates in FP cavity 1 and FP cavity 2. When the dual FP enhancement cavity resonance condition is met, high laser power will accumulate in the cavity.

[0075] The derivation of the dual FP enhanced cavity resonance condition is as follows. The ratio of the forward propagation optical field in FP cavity 1 to the forward propagation optical field of a conventional FP cavity is defined as follows: ,but It can be represented as: (1) in, This represents the light reflectivity of each cavity mirror. This indicates the light transmittance of each cavity mirror. and These represent the phases of the laser as it travels back and forth once within FP cavity 1 and FP cavity 2, respectively.

[0076] when , ( , When (integer), Take the maximum value This is defined as the double FP enhanced cavity resonance condition.

[0077] For a dual-FP enhancement cavity composed of high-reflectivity cavity mirrors Therefore, the optical field amplitude in FP cavity 1 is twice that of a traditional FP cavity; the laser power is proportional to the square of the optical field amplitude, and the laser power in FP cavity 1 is four times that of a traditional FP cavity.

[0078] When the dual FP-enhanced cavity resonance condition is met, the incident laser and FP cavity 1 satisfy the constructive interference condition, and FP cavity 2 satisfy the destructive interference condition, and the laser power accumulates only in FP cavity 1.

[0079] The frequency locking unit detects the cavity mode signal of the dual FP enhancement cavity unit and demodulates it to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. Based on the error signal, the output frequency of the laser in the laser unit is adjusted to achieve frequency locking.

[0080] In this embodiment, the frequency locking unit includes a photodetector, a frequency locking module, and a feedback controller. The photodetector is used to detect the cavity mode signal of the dual FP enhancement cavity; the frequency locking module demodulates and filters the reflected signal to generate an error signal; and the feedback controller is used to adjust the output frequency of the laser.

[0081] The frequency locking unit is based on PDH frequency locking technology, and the error signal of the dual FP enhancement cavity is a standard dispersive error signal.

[0082] Embodiment 3 of the present invention provides a terminal, including a processor and a storage medium; the storage medium is used to store instructions; the processor is used to perform operations according to the instructions to execute the steps of the method.

[0083] Embodiment 4 of the present invention provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the steps of the method.

[0084] Compared with the prior art, the beneficial effects of the present invention include at least the following: The present invention is a novel resonant cavity structure consisting of three coaxially parallel high-reflectivity mirrors forming FP cavity 1 and FP cavity 2. By adjusting the phase relationship of the incident laser in FP cavity 1 and FP cavity 2, the power gain can be increased. When the resonance condition is met, its power gain is up to 4 times that of the traditional FP cavity.

[0085] The novel enhancement cavity structure with high power gain proposed in this invention avoids the dependence on ultra-high reflectivity cavity mirrors used in existing resonant cavity enhancement technologies to improve power gain. This structure is expected to break through the current power gain limit of resonant cavities.

[0086] This disclosure can be a system, method, and / or computer program product. A computer program product may include a computer-readable storage medium having computer-readable program instructions loaded thereon for causing a processor to implement various aspects of this disclosure.

[0087] Computer-readable storage media can be tangible devices capable of holding and storing instructions for use by an instruction execution device. Computer-readable storage media can be, for example—but not limited to—electrical storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of computer-readable storage media include: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable compact disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, such as punch cards or recessed protrusions storing instructions thereon, and any suitable combination of the foregoing. The computer-readable storage media used herein are not to be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., light pulses through fiber optic cables), or electrical signals transmitted through wires.

[0088] The computer-readable program instructions described herein can be downloaded from computer-readable storage media to various computing / processing devices, or downloaded via a network, such as the Internet, local area network, wide area network, and / or wireless network, to an external computer or external storage device. The network may include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. A network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards them to the computer-readable storage media in the respective computing / processing device.

[0089] Computer program instructions used to perform the operations of this disclosure may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, status setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, etc., and conventional procedural programming languages ​​such as the "C" language or similar programming languages. The computer-readable program instructions may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In cases involving a remote computer, the remote computer may be connected to the user's computer via any type of network—including a local area network (LAN) or a wide area network (WAN)—or may be connected to an external computer (e.g., via the Internet using an Internet service provider). In some embodiments, electronic circuitry, such as programmable logic circuitry, field-programmable gate arrays (FPGAs), or programmable logic arrays (PLAs), is personalized by utilizing the status information of the computer-readable program instructions to implement various aspects of this disclosure.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A dual F-P enhanced cavity for boosting power gain multiplication, characterized in that, The dual FP enhancement cavity includes a laser unit, a dual FP enhancement cavity unit, a resonance condition locking unit, and a frequency locking unit; The laser unit is used to generate and modulate laser light, and the modulated laser light is matched with the spatial pattern of the dual FP enhancement cavity unit and then input into the dual FP enhancement cavity unit. The dual FP enhancement cavity unit includes FP cavity 1 and FP cavity 2, which are used to reflect the incident laser. The resonance condition locking unit is used to collect the reflected light intensity of the dual FP enhancement cavity unit in real time and compare it with the reference reflected light intensity under the resonance condition to obtain the deviation signal. Based on the deviation signal, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the resonance condition of the dual FP enhancement cavity to improve the power gain. The frequency locking unit is used to detect the cavity mode signal of the dual FP enhancement cavity unit and demodulate it to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. The output frequency of the laser in the laser unit is adjusted according to the error signal to achieve frequency locking.

2. The dual FP enhancement cavity for increasing power gain as described in claim 1, characterized in that: The laser unit includes a laser, an electro-optic modulator, and a lens group; The laser is used to generate a single-frequency laser. The electro-optic modulator is used to generate phase modulation sidebands and modulate the laser light generated by the laser. The lens group is used to match the spatial pattern of the modulated laser and the dual FP intensifier cavity unit before inputting it into the dual FP intensifier cavity unit.

3. A dual FP enhancement cavity for increasing power gain as described in claim 2, characterized in that: The lens group is an achromatic lens group, which is mounted on a multi-axis displacement stage. By precisely controlling the output beam, the modulated laser spot emitted by the fiber laser is made to coincide with the waist spot of the fundamental mode of the dual FP enhancement cavity unit.

4. A dual FP enhancement cavity for increasing power gain as described in claim 1, characterized in that: The process of matching the modulated laser with the spatial pattern of the dual FP enhanced cavity unit includes: Spatial mode matching is performed on the modulated laser incident on the dual FP enhancement cavity unit so that the modulated laser matches the fundamental mode of FP cavity 1; and spatial mode matching is also performed on the laser that is reflected by the high-reflectivity mirror M3 in the dual FP enhancement cavity unit and then incident on FP cavity 1 again so that it also matches the fundamental mode of FP cavity 1.

5. A dual FP enhancement cavity for increasing power gain as described in claim 1, characterized in that: The dual FP enhancement cavity unit includes three high-reflectivity mirrors M1, M2 and M3 placed coaxially and in parallel. Among them, high-reflection lenses M1 and M2 form FP cavity 1, and high-reflection lenses M2 and M3 form FP cavity 2; The incident laser propagates in a loop within FP cavity 1 and FP cavity 2. When the resonant condition of the dual FP enhanced cavity is met, high laser power is accumulated in FP cavity 1.

6. A dual FP enhancement cavity for increasing power gain as described in claim 5, characterized in that: The three high-reflectivity lenses M1, M2 and M3 are mounted on a multi-axis high-stability frame. Annular piezoelectric ceramics are attached to the back of the lenses. Under high-voltage signal drive, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the dual FP enhanced cavity resonance condition.

7. A dual FP enhancement cavity for increasing power gain according to claim 1, characterized in that: The dual FP-enhanced cavity resonance condition is the phase condition when the ratio of the forward propagation optical field in FP cavity 1 to the forward propagation optical field of the conventional FP cavity reaches its maximum value. The ratio of the forward propagation optical field in FP cavity 1 to the forward propagation optical field of the conventional FP cavity is: in, This represents the light reflectivity of the cavity mirror. This represents the light transmittance of the endoscope. and These represent the phases of the laser as it travels back and forth once within FP cavity 1 and FP cavity 2, respectively.

8. A dual FP enhancement cavity for increasing power gain as described in claim 1 or 7, characterized in that: The resonant condition for the dual FP enhanced cavity is: ， in, , It is an integer. and These represent the phases of the laser as it travels back and forth once within FP cavity 1 and FP cavity 2, respectively.

9. A dual FP enhancement cavity for increasing power gain according to claim 1, characterized in that: The frequency locking unit includes a photodetector, a frequency locking module, and a feedback controller; The photodetector is used to detect the cavity mode signal of the dual FP enhanced cavity; The frequency locking module is used to demodulate and filter the cavity mode signal to generate an error signal that reflects the deviation between the laser frequency and the resonant frequency of the dual FP enhanced cavity. The feedback controller is used to adjust the output frequency of the laser in the laser unit according to the error signal.

10. A dual FP enhancement cavity for increasing power gain according to claim 9, characterized in that: The process by which the frequency locking module demodulates and filters the cavity mode signal to generate an error signal is as follows: First, a sinusoidal modulation signal is applied to the electro-optic modulator in the laser unit to create a modulation sideband; Secondly, based on the modulation sideband, the cavity mode signal is demodulated using an internally generated signal with the same frequency as the sinusoidal modulation signal, and redundant signal components are filtered out by a low-pass filter to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. The error signal is: in, This represents the reflection function of the optical field in a dual-FP cavity. Indicates the incident laser angular frequency. and Indicates the free spectral path of FP cavity 1 and FP cavity 2. for The complex conjugate, The modulation frequency of the phase modulation sideband generated by the electro-optic modulator. This represents the light reflectivity of the cavity mirror.

11. A dual FP enhancement cavity for increasing power gain as described in claim 9, characterized in that: The feedback controller includes a fast controller and a slow controller. The error signal is dynamically PID-regulated by the fast controller and the slow controller and applied to the acousto-optic modulator and piezoelectric ceramic inside the laser to adjust the laser output frequency.

12. A dual FP enhancement cavity for increasing power gain according to claim 1, characterized in that: The outer cavity of the dual FP enhanced cavity is made of Invar steel, and the cavity is wrapped with a temperature control layer to stabilize the temperature within the set range. A graded temperature control system is used for dynamic compensation and adjustment.

13. A dual FP enhancement cavity for increasing power gain according to claim 1, characterized in that: The relative positions of the incident laser and the dual FP enhancement cavity are precisely adjusted according to the cavity mode signal of the dual FP enhancement cavity unit to ensure that no high-order mode signal is generated and improve the coupling efficiency of the incident laser.

14. A method of operating a dual F-P enhanced cavity for boosting the power gain multiplier according to any one of claims 1-13, characterized in that, include: The laser unit generates and modulates laser light, and then inputs the modulated laser light into the dual FP enhancement cavity unit after matching the spatial mode of the dual FP enhancement cavity unit. The dual FP enhancement cavity unit reflects the incident laser. The resonance condition locking unit collects the intensity of the reflected light from the dual FP enhancement cavity unit in real time and compares it with the reference reflected light intensity under the resonance condition to obtain the deviation signal. Based on the deviation signal, the phase relationship of the incident laser in FP cavity 1 and FP cavity 2 is adjusted so that the phase relationship satisfies the resonance condition of the dual FP enhancement cavity to improve the power gain. The frequency locking unit detects the cavity mode signal of the dual FP enhancement cavity unit and demodulates it to obtain an error signal reflecting the deviation between the laser frequency and the resonant frequency of the dual FP enhancement cavity. Based on the error signal, the output frequency of the laser in the laser unit is adjusted to achieve frequency locking.

15. A terminal, comprising a processor and a storage medium; characterized in that: The storage medium is used to store instructions; The processor is configured to operate according to the instructions to perform the steps of the method according to claim 14.

16. A computer readable storage medium having stored thereon a computer program, characterized in that When the program is executed by the processor, it implements the steps of the method of claim 14.

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