Study On Fiber Lasers And Mid-infrared Semiconductor Lasers And Their Sensing Applications

The laser sensing technology has achieved lots of developement in the recent years due to its advantages such as simple structure, high stability, high sensitivity, and strong durability and so on. One of the laser sensors, the fiber laser sensor, is more and more used in many applications such as acoustic detecting and structure monitoring due to its high signal-noise ratio and narrow linewidth. In this thesis, the mechanism and fabrication of the fiber grating laser are introduced. The fiber grating laser sensor based on the beat frequency demodulation technology is also studied. The performance of mid-infrared semiconductor lasers such as the fabrication of quantum cascade laser (QCL) and the farfield of interband cascade laser (ICL) are also investigated. The major results are summarized as follows:(1) The theory of the fiber Bragg grating and the mechanism of the fiber laser are introduced. The coupled-mode theory (CMT) and transfer matrix method (TMM) are used to simulate the light transmission in the fiber grating. The fabrication of a fiber grating laser by using the phase mask is introduced in detail. In the end, the double-wavelength fiber laser based on the equivalent phase shift (EPS) technology is introduced.(2) The multi-wavelength fiber laser sensor based on the beat frequency demodulation technology is analyzed. By applying different pump powers, its optical spectra and the frequency-strain responses are investigated, which show the four wave mixing (FWM) effect in the fiber laser sensor. In addition, based on the beat frequency demodulation technology, the fiber ring multi-longitudinal-mode laser temperature sensor is also proposed. The measured temperature is as high as1000℃and the sensitivity is8.48kHz/℃@1480.5MHz.(3) The basic principle of QCL is introduced in this thesis. The process of the QCL is illustrated, including the grating fabrication, the ridge etch, the insulation layer growth, the metal contact fabrication, and the cleavage, mounting, wire-bonding and so on.(4) The principle and the characterization method of the ICL, such as the spectra and the I-V-P measurement, are introduced in this thesis. Based on the simulation and experiment results, it is demostrated that along the ridge-width direction, the commonly adopted center metal contact configuration leads to an undesirable double-lobe far-field pattern associated with the first-order lateral mode in the plasmon waveguide IC lasers; while with two metal contacts placed near the edges of the ridge, a more desirable, less divergent single-lobed beam is exhibited in the far-field profiles.