ABSTRACT
In this paper, a spatial static polarization modulation interference spectrum technique is proposed, which combines polarimetric spectral intensity modulation (PSIM) technology and spatial heterodyne spectroscopy (SHS), and can obtain the total Stokes parameters of the target light simultaneously. Moreover, there are no moving parts or electronically controlled modulation parts. In this paper, the mathematical model of the modulation process and demodulation process of spatial static polarization modulation interference spectroscopy is deduced, a computer simulation is carried out, the principle prototype is developed, and a verification experiment is carried out. Simulation and experimental results show that the combination of PSIM and SHS can achieve high-precision static synchronous measurement of high spectral resolution, high time resolution, and continuous band complete polarization information.
ABSTRACT
Digital micromirror device (DMD) and spatial heterodyne spectroscopy (SHS) combined modulation interference spectroscopy (DMD-SHS) introduces a DMD for the secondary modulation of interferometric data to achieve a Hadamard transform. DMD-SHS can improve the performance index of the spectrometer in terms of the SNR, dynamic range, and spectral bandwidth, while retaining the advantages of a conventional SHS. The DMD-SHS optical system is more complex than a traditional SHS, which places more demands on the optical system's spatial layout and the optical components' performance. According to the DMD-SHS modulation mechanism, the functions of the main components were analyzed, and their design requirements were determined. Based on the potassium spectra detection, a DMD-SHS experimental device was designed. The potassium lamp and integrating sphere detection experiments demonstrated the detection capability of the DMD-SHS experimental device with a spectral resolution of 0.0327 nm and a spectral range of 763.66â¼771.25n m, which thoroughly verified the feasibility of DMD and SHS combined modulation interference spectroscopy.
ABSTRACT
Microwave photonic sensors are promising for improving sensing resolution and speed of optical sensors. In this paper, a high-sensitivity, high-resolution temperature sensor based on microwave photonic filter (MPF) is proposed and demonstrated. A micro-ring resonator (MRR) based on silicon-on-insulator is used as the sensing probe to convert the wavelength shift caused by temperature change to microwave frequency variation via the MPF system. By analyzing the frequency shift with high-speed and high-resolution monitors, the temperature change can be detected. The MRR is designed with multi-mode ridge waveguides to reduce propagation loss and achieves an ultra-high Q factor of 1.01 × 106. The proposed MPF has a single passband with a narrow bandwidth of 192 MHz. With clear peak-frequency shift, the sensitivity of the MPF-based temperature sensor is measured to be 10.22 GHz/°C. Due to higher sensitivity and ultra-narrow bandwidth of the MPF, the sensing resolution of the proposed temperature sensor is as high as 0.019 °C.
ABSTRACT
Interference data obtained by a spatial heterodyne spectrometer (SHS) is subject to various error factors and suffers from complex phase distortion. Traditional phase correction methods, such as the Amplitude, Merzt, and Forman methods, extract phase distortion in the spectral domain and correct it, which cannot effectively correct spatial phase distortion. Through theoretical derivation and numerical simulation, the spatial phase distortion is firstly determined and corrected in the interference domain. The frequency-dependent phase distortion is then extracted in the spectral domain and corrected. This novel phase distortion correction method named the phase decomposition method was applied to the in-orbit interference data of Greenhouse gases Monitoring Instrument-II (GMI-II). Compared with traditional phase correction methods, the root-mean-square error of the spectrum corrected using the phase decomposition method is reduced by 81.37%.
