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Title: Efficient, high performance photonic devices for optical fibre communications and related applications
Author: Sayid, Sayid Ally
ISNI:       0000 0004 2723 3947
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2012
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We find that 1.55 μm InGaAlAs quantum well lasers the temperature sensitivity of threshold current, Jth is due to non-radiative Auger recombination accounting for ~80% of Jth at room temperature (RT). The breakpoint temperature, TB is 140+-5K above which Auger recombination dominates. The characteristics temperature, To(Ith)=70+-2K at RT. The differential internal quantum efficiency above threshold, ni, is ~80±10% at 20°C remaining stable up to 80°C. In contrast, the internal optical loss ai , increases from 14±4 cm-1 at 20°C to 24±4 cm-1 at 80°C, consistent with inter-valence band absorption (IVBA). The modal gain peak for InGaAlAs quantum well (QW) lasers was found to be 14±2 cm-1 increasing to 52±2 cm-1 when injected current density was 1.06 kAcm-2 and 1.8 kAcm-2 respectively. In 1.55 μm InAs/InP (100) quantum dot lasers Jth and its radiative component, Jrad are measured as a function of temperature. Jrad is relatively temperature insensitive, however, Jth increases significantly with temperature leading to To=72±2K over the range 220-290K. Non-radiative recombination accounts for up to 94% of Jth at T=293K. Jth decreases with increasing hydrostatic pressure by 35% over 8kbar causing an increase in To from 72±2K to 88±2K. The results indicate that non-radiative Auger recombination determines temperature behaviour of these devices under normal operating conditions. The modal gain peak for InAs/InP quantum dot (QD) lasers was found to be 12±4 cm-1 increasing to 30 cm-1 when injected current density was 570 Acm-2 and 720 Acm-2 respectively. A multi-section single pass technique has been developed that allows the measurement of a modal gain spectrum from a Fabry-Perot laser. InGaAsP and InGaAlAs intermixed quantum wells (IQWs) used in Mach-Zehnder modulator (MZM) were investigated. For InGaAsP IQWs the absorption edge was found to be 0.877 eV (1413 nm) while in the InGaAlAs IQWs the absorption edge was found to be 0.925 eV (1370 nm) which translate to wavelength detuning of 117 nm and 160 nm for an operating wavelength at 1530 nm respectively. InGaAlAs IQWs exhibited sharp absorption edge over the range of the applied bias. It was found that using InGaAlAs or InGaAsP IQWs for wavelength detuning of ≤160 nm is not suitable for MZM application, because induced refractive index change is at minimum and would require higher reverse bias to obtain sufficient phase shift to modulate the signal. The exciton energy peak shift for InGaAsP IQWs was found to be 32 meV for applied bias range 0V to -6V, while for InGaAlAs IQWs was found to be 16 meV for applied bias range 0V to -6V.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available