Author : Gary Michael Smith
Release : 1996
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Kind : eBook
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Book Synopsis Single Frequency Semiconductor Lasers by : Gary Michael Smith

Download or read book Single Frequency Semiconductor Lasers written by Gary Michael Smith. This book was released on 1996. Available in PDF, EPUB and Kindle. Book excerpt: Single frequency semiconductor lasers are of interest for communication systems and spectroscopy. In communications, narrow linewidth is desirable to minimize dispersion effects and low cross-talk multiple wavelength channels on a single fiber. For GaAs-based lasers, the interest in narrow linewidth sources comes from the spectroscopy community that desires a light source that can be tuned to very narrow absorption spectra of various materials. For both of these applications, narrow linewidth, wavelength tunable semiconductor lasers are well-suited. This thesis describes the development of a single epitaxial growth ridge waveguide distributed Bragg reflector (RW-DBR) laser. These lasers exhibit low thresholds, fairly high slope efficiencies, and single frequency operation with very narrow linewidth. The fabrication requires only a single epitaxial growth of a standard laser structure and then an anisotropic etch to transfer a grating pattern from the top surface of the laser into the epitaxial layers. The initial RW-DBR lasers fabricated by this method had symmetric cladding layers with a thickness of 1.2 $mu$m, which required etch depths of over 1 $mu$m in order to couple adequately to the optical mode. This required a highly anisotropic etch and limited the device design to third-order gratings. However, fairly good device performance was demonstrated with these symmetric cladding RW-DBR lasers. To relax the constraints on the grating etch, an asymmetric cladding separate confinement heterostructure (AC-SCH) laser was developed. The AC-SCH design reduces the thickness of the top cladding layer, which results in shallower depths for the grating etch and allows the fabrication of more efficient second-order DBR gratings. The incorporation of the AC-SCH into the RW-DBR laser reduces the threshold current, increases the efficiency, and decreases the spectral linewidth.