Browsing by Subject "Semiconductor lasers."

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    Fabrication and characterization of semiconductor double quantum well diode lasers
    (1998) Sağol, Bülent Erol
    In this thesis, semiconductor double quantum well, Fabry-Perot and half ring hisers were fabricated, and these devices were operated and characterized at room temperature. The lasers were fabricated using GaAs/AlGaAs double quantum well wafers, and processed in order to produce 4^m wide, l/im-4/im high mesas for optical confinement. This mesa isolation was done by means of wet and dry etching techniques. Fabrication of Fabry-Perot lasers was completed after Si02 insulation, p-contact and n-contact metalizations, thinning, and dicing. Similar fabrication techniques were applied to produce ring lasers coupled to Fabry-Perot cavities, with various diameters ranging from 50 to 1400//m. Device characterization was done by means of photoluminescence, currentvoltage, current-power measurements, and electroluminescence. Photoluminescence was used for checking the lasing wavelength. Current-voltage and current-power measurements were done to investigate the serial resistances, threshold currents, and differential quantum efficiencies of the fabricated devices with various cavity lengths. From these measurements, the threshold current densities, the internal quantum efficiencies, and the internal net optical losses were obtained. Finally, electroluminescence was used to obtain the lasing spectra, and from this, the free spectral range of the Fabry-Perot and ring lasers were measured.
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    Gain measurements via spontaneous emission in quantum well semiconductor lasers
    (1996) Azfar, Talal
    111 this work ail analysis of gain in single c|iianliini well last'rs as a riinction of sonu' of llu'ir o|)(M’alioiial paranu'l('rs is earrii'd oiil. I^'irsl, a 1 li('or('liea.l inodi'l of gain is |)resent('d. 'riuMi two diderent nudliods of gain iiK'asiir('in('nt, wliieli iis(' the spontaneous emission IVom the iaec't and the nnamplified s[)ontan('ons ('mission from the top of the ridg(', arc' discussed. Indirication procc'sses of lasers to racilitate tJie colh'clion of unampliiic'd spontaiK'ous ('mission are ch'tailed. R('S|)onse of the gain sp('ctrum to chang('s in inject('d cnrr('nt (h'lisity and temperature are measur('d and iinderstood in terms of hand Idling, hand gap renormalization and tenpx'rature d('pendenc(' of tlu' handgap. (!ain sainration above threshold is v('ri(ied and s|)atial variations in spontaiu'ons ('mission in lh(' longitiidnal and hiteral directions are observed.