Off-Axis Integrated Cavity Spectrum Fitting With RF Noise Modeling
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Solution Overview
Problem
The broadened spectral line caused by radio frequency noise in off-axis integrated cavity systems leads to fitting errors and reduced measurement accuracy in Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS) systems, as conventional methods fail to suppress the noise effectively and explain its disturbance mechanism.
Innovation Solution
A method and device for fitting a spectrum in an off-axis integrated cavity disturbed by radio frequency noise, involving setting a single mode output light field, converting radio frequency white noise disturbance to phase disturbance, and constructing a forward fitting model using spectral absorption coefficients to accurately fit the broadened absorption spectral line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radio frequency white noise is injected into the laser current to suppress cavity mode noise, then the cavity mode noise is reduced, but the spectral absorption line is broadened causing fitting errors
Solution Approach 1:
The patent changes the parameter of the spectral absorption line shape by introducing a new function form that incorporates the broadening effect caused by radio frequency noise. Instead of using a conventional Lorentzian or Gaussian profile, the patent uses a modified function that includes an additional parameter to account for the noise-induced broadening, allowing accurate fitting even when the line shape is distorted.
Solution Approach 2:
The patent converts the harmful broadening effect of radio frequency noise into a beneficial feature by explicitly modeling it in the fitting function. The noise-induced broadening, which was previously considered a disturbance to be eliminated, is now incorporated as a known parameter in the spectral fitting process, allowing the system to compensate for its effects and maintain measurement accuracy.
2Device complexity
If conventional linear function is used to fit the broadened spectral line, then the fitting process is simple, but the fitting error increases due to the broadened line shape
Solution Approach 1:
The patent introduces additional parameters to the fitting model to capture the broadening characteristics. The new function form includes parameters that specifically describe the noise-induced broadening, allowing the model to adapt to the actual spectral line shape while maintaining reasonable computational complexity through analytical solutions where possible.
3Reliability
If fully off-axis configuration is used, then the cavity mode noise is minimized, but residual cavity mode noise remains affecting measurement accuracy
Solution Approach 1:
The patent accepts the residual cavity mode noise as an inevitable characteristic of off-axis operation and converts it into a manageable parameter. By explicitly modeling the noise characteristics in the fitting function, the system can compensate for the residual noise effects, transforming what was previously a fundamental limitation into a correctable disturbance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method and device improve measurement accuracy by reducing system fitting errors and achieving precise fitting of the broadened absorption spectral line, enhancing the performance of OA-ICOS systems.
Implementation Method 1
a phenomenon of random fluctuations in a laser phase will occur when laser emits into an optical resonant cavity off axis, so as to generate optical cavity mode noise
Implementation Method 2
injected radio frequency white noise (1 to 1500 MHz) after being subjected to 30 MHz low-pass filtering into a laser current to broaden a laser linewidth to reduce the cavity mode noise
Implementation Method 3
Off-axis integrated cavity output spectroscopy is a high-sensitivity gas detection technology suitable for atmospheric trace gas detection
Data Source
AI summary
This application relates to a method and a device for fitting a spectrum in an off-axis integrated cavity disturbed by radio frequency noise. The method includes: setting a single mode output light field of a laser; obtaining a maximum cutoff frequency and a power spectral density of radio frequency white noise generated by a radio frequency noise source, and converting a disturbance of the radio frequency white noise in electricity to a phase disturbance of the light field to obtain a converted power spectral density; determining a laser power spectrum according to the set light field, and the maximum cutoff frequency and the converted power spectral density of the radio frequency white noise; obtaining a length and a cavity mirror reflectivity of an off-axis integrated cavity system, and an initial light intensity and a real-time light intensity when the off-axis integrated cavity system runs; and constructing a forward fitting model.