| Summary: | 博士 === 國立交通大學 === 電子物理系所 === 101 === Recently, the semiconductor multiple-quantum-wells (MQWs) structure is extensively used in the semiconductor lasers owing to the characteristics like versatile emission wavelength, lower laser threshold and excellent performance under room temperature operation. It is also applied as a promising saturable absorber in the diode-pumped passively Q-switched solid-state laser. Compared to the doped crystal saturable absorber, the MQWs absorber has lower non-saturable loss and allows the shorter cavity length. According to these characteristics, the MQWs structure has the potential to be designed simultaneously as a saturable absorber and an active medium in the intra-cavity pumped solid-state lasers. Besides, the many-body effect of the high density electron-hole plasma (EHP) under this quasi-2D confinement structure is also an interesting issue. Therefore, the contents of this dissertation are organized to be three parts. At the first part we investigate the many-body effect of the high density EHP in the quasi-2D confined MQWs structure. The room temperature spontaneous emission of the renormalized bandgap is observed under the designation of high confinement energy and periodically aligned gain structure. The temperature dependent luminescence features such as photoluminescence (PL) spectrum and the integrated PL intensity are discussed and the threshold excitation intensity of the luminescence of renormalized band-edge is shown to be exponentially increased with increasing temperature. As a result we have confirmed that the periodically aligned MQWs structure is beneficial to the observation of room temperature many-body state emission
In the second part, an AlGaInAs MQWs structure is designed to be the gain chip of a high repetition rate and high peak power 1220 nm optically-pumped semiconductor laser (OPSL). By using an Yb-doped master oscillator fiber amplifier as the pump source, the output performance could be optimized with the free controlled pump conditions such as pump repetition rates and pulse durations. Then the same pump laser is used to excite the high repetition rate and high peak power AlGaInAs MQW OPSL at the communication and eye-safe spectral region of 1520 nm. By capillary bonding the highly transparent and thermal conductive single crystal diamond heat spreader to the gain chip, the thermal roll-over effect was eased at high average pump power under high repetition rate operation. The optimized repetition rate was raised from 30 to 200 kHz and the maximum average output power was scaled to be 4.7 times higher. When operated at as high as 500 kHz, the maximum average power of 2.32 W and peak power of 170 W were obtained.
At the end of this dissertation an AlGaInAs MQW structure is used simultaneously as the saturable absorber (SA) and wavelength-converted component in the Nd:GdVO4 laser. It is fabricated to accommodate the pump level of 1064 nm and the emission level of 1530 nm in the quantum well region. The upper state is served as the nonlinear saturable absorption device at 1064 nm and the lower state is served as the active medium at 1530 nm with additional couple-cavity in the Nd:GdVO4 laser. This configuration combines the advantages of the self-Q-switched lasers, pulse-pumped solid state lasers and the semiconductor MQW structures. Because there is no need of additional electronic drivers for passively Q-switches and the shorter action lengths of the MQWs compared to the bulk crystal SAs and nonlinear crystals, the device configuration could be simplified and cavity length is shortened, respectively. According to these characteristics and the capillary bonding technique in second part, this laser system has potential to be served as a low cost, simple and monolithic passively Q-switched microchip laser with broad achievable spectral range.
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