Author : Yann Tanguy
Release : 2005
Genre : Semiconductor lasers
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Modal Properties of Semiconductor Lasers - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Modal Properties of Semiconductor Lasers write by Yann Tanguy. This book was released on 2005. Modal Properties of Semiconductor Lasers available in PDF, EPUB and Kindle. The importance of semiconductor lasers has grown steadily over the years, these devices being now essential in a wide range of fields. This includes optical reading and writing of stored data, light source for optical fibres in telecommunications, medical applications, laser printing {u2026} There is an ever expanding need for higher output power and higher brightness from semiconductor devices. This can be achieved with various approaches. Unstable resonators use cavity designs with curved mirrors to yield a highly divergent beam, and counteract the self-focusing tendency of the light in laser materials. These resonators also increase the transverse mode discrimination. Both characteristics improve the beam quality, and make these devices attractive for fibre coupling applications, such as transfer of data for telecommunications. Different cavity geometries with an internal beam waist were tested, and did not display the same behaviour. In some cases we observed a displacement of the beam waist due to thermal lensing, which is not desired for fibre coupling schemes. With modelling and experimental investigations we explained this phenomenon, and proposed some cavity designs to alleviate this problem. The effect of optical feedback in lasers is a common cause of beam deterioration. Feedback on self-pulsing devices is still an important area to explore and comprehend, as this affects applications (such as optical data storage) requiring self-pulsing output powers. Some of the unstable resonators displayed self-pulsing dynamics, and the indluence of optical feedback was analysed, first experimentally, andd then theoretically with a model based on Lang-Kobayashi equations. The appearance of perturbations in the optical intensity is suggested to be linked with transition between limit cycles. The properties of semiconductor materials can also improve the beam quality. Intense research is currently focusing on Quantum Dot (QD) materials, containing nanostructures as small as 10nm which provide a nearly quantised optical gain for lasing action. Many improvements and specific characteristics are expected from these QD devices, particularly an improvement of the spatio-temporal stability of the beam. The transverse modes of broad are QD devices were experimentally examined, and dynamic instabilities characterised. The temperature profile was found to be beneficial to the transverse mode stability. In narrow wave-guide devices, simultaneous lasing in both the low and high energy levels was investigated. Simulations explained the observed decay of the low energy level lasing with increasing current. And strong antiphase dynamics were recorded between the high and low level output powers, at relatively low frequencies (below 50 M H z). Finally, interactions between longitudinal Fabry-Perot modes displayed some interesting and complex features. The output power dynamics were found to be chaotic, and the modal coupling via homogeneous broadening resulted in the appearance of frequency synchronisation. And cross-correlation measurements between modes exhibited a modal switching sequence from blue to red wavelengths, which appear to differ from periodic antiphase dynamics reported for quantum well lasers.