CN-121994382-A - Fabry-Perot Luo Qiangya force detector based on ultra-stable laser and detection method

CN121994382ACN 121994382 ACN121994382 ACN 121994382ACN-121994382-A

Abstract

The invention discloses a Fabry-Perot Luo Qiangya force detector based on an ultrastable laser and a detection method, wherein the ultrastable laser, an electro-optical modulator, a polarization beam splitter and an FP cavity sensor are sequentially arranged along the propagation direction of an optical path; the FP cavity sensor is configured to generate cavity length change by external pressure of an FP cavity, reflect or transmit optical signals containing laser frequency and cavity resonance frequency mismatch, reflect the optical signals into the detector through the polarization beam splitter, convert the optical signals into electric signals through the detector, receive the electric signals and modulation signals of the electro-optical modulator through the mixer, mix the electric signals and modulation signals of the electro-optical modulator, demodulate and extract PDH error signals, and the PDH error signals are used for resolving the laser frequency and the cavity resonance frequency mismatch and calculating to obtain external pressure values. The invention can obviously improve the resolution and stability of pressure measurement.

Inventors

CAI MINGLEI
ZHOU FAN
CAO MINGMING
GUO WEIXUAN

Assignees

华翊博奥(北京)量子科技有限公司

Dates

Publication Date: 20260508
Application Date: 20251028

Claims (7)

1. The Fabry-Perot Luo Qiangya force detector based on the ultra-stable laser is characterized by comprising the ultra-stable laser, an electro-optical modulator, a polarization beam splitter and an FP cavity sensor which are sequentially arranged along the propagation direction of an optical path; The FP cavity sensor is configured to generate cavity length change under external pressure of an FP cavity, and reflect or transmit an optical signal containing the mismatch between the laser frequency and the cavity resonance frequency, wherein the optical signal is reflected by the polarization beam splitter and enters a detector; The mixer receives the electric signal and the modulation signal of the electro-optical modulator, mixes the two paths of signals, demodulates and extracts a PDH error signal, and the PDH error signal is used for resolving the mismatch between the laser frequency and the cavity resonance frequency and calculating to obtain an external pressure value.
2. The Fabry-Perot Luo Qiangya force detector based on the ultra-stable laser is characterized by further comprising a 1/4 wave plate, wherein the ultra-stable laser emits linearly polarized light, the linearly polarized light is sequentially transmitted to an FP cavity sensor through an electro-optical modulator, a polarization beam splitter and the 1/4 wave plate, and the light signal reflected or transmitted by the FP cavity sensor is projected to the polarization beam splitter again through the 1/4 wave plate and reflected to the detector through the polarization beam splitter.
3. The ultra-stable laser-based fabry-perot Luo Qiangya force detector according to claim 1, further comprising a signal source for generating an original signal source signal for driving an electro-optical modulator as the modulation signal, wherein the original signal source signal is subjected to phase adjustment by an adjustable phase shifter, and then is input to a mixer as a reference signal to be mixed with the electric signal output by the detector, and a PDH error signal is demodulated and extracted.
4. A fabry-perot Luo Qiangya force probe based on a hyperstable laser as claimed in claim 1 wherein the frequency noise power spectral density of the hyperstable laser is below 0.01Hz 2 /Hz at a 1kHz offset frequency.
5. A fabry-perot Luo Qiangya force detection method based on a fabry-perot Luo Qiangya force detector of an ultrastable laser according to any one of claims 1 to 4, comprising the steps of: s1, sampling a PDH error signal output by a mixer in real time, wherein a voltage value V err of the PDH error signal is in a direct proportion relation with the difference delta f between the ultra-stable laser frequency and the FP cavity eigenfrequency, and acquiring a real-time calculated value of the difference delta f between the ultra-stable laser frequency and the FP cavity eigenfrequency; s2, calculating and obtaining real-time variation of equivalent cavity length of the FP cavity through a real-time calculated value of delta f; And S3, calculating and acquiring the pressure real-time variation of the FP cavity through the equivalent cavity length real-time variation of the FP cavity.
6. The ultra-stable laser based fabry-perot Luo Qiangya force detector according to claim 5, wherein the difference Δf between the ultra-stable laser frequency and the FP cavity eigenfrequency comprises a frequency change Δf L of the ultra-stable laser itself and an eigenfrequency change Δf c of the FP cavity due to an external pressure change, wherein Δf L <<Δf c .
7. The ultra-stable laser-based fabry-perot Luo Qiangya force detector according to claim 1, wherein the formula for obtaining the real-time variation of the equivalent cavity length of the FP cavity by calculating the real-time calculated value of Δf in S2 is: wherein f is the laser center frequency of the ultra-stable laser, deltaL is the equivalent cavity length real-time variable quantity of the FP cavity, and L is the initial cavity length of the FP cavity.

Description

Fabry-Perot Luo Qiangya force detector based on ultra-stable laser and detection method Technical Field The invention relates to the technical field of measurement, in particular to a Fabry-Perot Luo Qiangya force detector based on an ultra-stable laser and a detection method. Background The Fabry-Perot (FP) cavity sensor has been widely used in the fields of barometric pressure measurement, underwater sound detection, etc. because of its simple structure, high sensitivity, easy miniaturization and integration. Typical FP cavity hydrophones or barometers operate on the principle of optical resonance in that when ambient pressure is applied to the FP cavity, the physical or equivalent optical length of the cavity changes, causing the resonant wavelength thereof to shift. By detecting this wavelength change, the magnitude of the applied pressure can be reversed. In the prior art, a broadband light source is typically used to illuminate the FP cavity and a spectrometer is used to monitor formants in the transmission or reflection spectrum in real time. When the pressure causes the FP cavity equivalent cavity length L eff to change, the wavelength λ satisfying the resonance condition nλ=2l eff moves with it (where N is an integer). And the pressure change information can be obtained by analyzing the drift delta lambda of the resonance wavelength and combining the calibrated sensitivity coefficient. However, this conventional detection method based on spectral scanning has a significant performance bottleneck. The pressure resolution is mainly limited by the wavelength resolution capability of the spectrometer. The wavelength resolution of the current common commercial spectrometer is about 0.01 nm, and high-end equipment can reach the order of 1 pm (0.001 nm). For an FP cavity sensor operating at a wavelength around 1550 nm, if its cavity strain sensitivity epsilon = Δλ/λ is 103101 In the range of/MPa, the corresponding wavelength sensitivity is 1.55nm/MPa to 155nm/MPa. Under this condition, the pressure resolution achieved by using a conventional spectrometer is only on the order of 10kPa to 100Pa, and even with a high-end spectrometer, the detection limit of 1Pa or less can be achieved under the optimal condition. In addition, the spectrum scanning mode has slow response speed and complex data processing, and is difficult to meet the requirements of high-dynamic and high-precision real-time monitoring. Particularly in underwater acoustic detection applications, the ocean background noise level can be as low as tens of micro-pascals (μpa) magnitude (e.g., zero order sea state), where the Noise Equivalent Pressure (NEP) of a conventional FP-cavity sensor is much higher, which is not effective in capturing weak acoustic signals. Therefore, there is a need for a fabry-perot Luo Qiangya force detector and method that can significantly improve the resolution and stability of pressure measurements. Disclosure of Invention In view of the above, the invention provides a fabry-perot Luo Qiangya force detector based on an ultrastable laser and a detection method thereof, which effectively combine the PDH technology with the ultrastable laser to realize high-sensitivity pressure demodulation. And establishing a quantitative relation between the PDH error signal and the cavity length change caused by pressure, and realizing high signal-to-noise ratio extraction of the weak pressure signal by utilizing the extremely low frequency noise characteristic of the ultra-stable laser. In order to achieve the above purpose, the present invention adopts the following technical scheme: The invention firstly provides a Fabry-Perot Luo Qiangya force detector based on an ultrastable laser, which comprises the ultrastable laser, an electro-optical modulator, a polarization beam splitter and an FP cavity sensor which are sequentially arranged along the propagation direction of an optical path; The FP cavity sensor is configured to generate cavity length change under external pressure of an FP cavity, and reflect or transmit an optical signal containing the mismatch between the laser frequency and the cavity resonance frequency, wherein the optical signal is reflected by the polarization beam splitter and enters a detector; The mixer receives the electric signal and the modulation signal of the electro-optical modulator, mixes the two paths of signals, demodulates and extracts a PDH error signal, and the PDH error signal is used for resolving the mismatch between the laser frequency and the cavity resonance frequency and calculating to obtain an external pressure value. Preferably, the device also comprises a 1/4 wave plate; the ultra-stable laser emits linearly polarized light, the linearly polarized light is transmitted to the FP cavity sensor through the electro-optical modulator, the polarizing beam splitter and the 1/4 wave plate in sequence, and the light signal reflected or transmitted by the FP cavity sensor is projected to the pol