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Determination of parameters is presented in the modeling of Tm-doped fiber lasers. The thesis chooses parameters, numerical simulation to examine the performance of the laser system for different pump schemes and cavity parameters. Their impacts on the laser performance are discussed.

Photoacoustic spectroscopy (PAS) is a sensitive spectroscopic technique for trace gas sensing. As a key component of a PA sensor system, the cell constant of the cylindrical PA cell has been simulated for optimizing geometric design, and the acoustic pressure distribution and frequency response of the first longitudinal and radial modes are analyzed by using a self‐established algorithm model. According to the theoretical simulation, a resonant PAS sensor system was finally designed and evaluated at the first longitudinal mode for trace water vapor detection. Highly sensitive wavelength modulation spectroscopy and second harmonic detection technique was combined with PAS detection method for enhancing sensitivity. Allan deviation analysis indicates that a detection limit of 2 ppm for H2O could be achieved at an optimal integration time of 200 s, corresponding to a normalized noise equivalent absorption coefficient of 2.59×10−9W⋅cm−1Hz−1/2.

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