Membrane quantum well lasers and tantalum pentoxide optical waveguides

Abstract

This thesis investigates two different optical technologies, membrane quantum well lasers and tantalum pentoxide rib waveguides and resonators. The former technology is explored as a potential coherent light source and amplifier for photonic integrated circuits. The latter technology is studied with the aim of exploiting the material’s high nonlinear properties to generate Kerr frequency combs for various applications such as optical telecommunications and remote sensing.Membrane quantum well lasers are semiconductor edge emitting laser devices, where stimulated emission occurs in the quantum well regions and is enhanced due to the strong waveguiding effect. The laser is optically pumped while in contact with a silicon carbide or silicon dioxide on silicon wafer as part of the heatsinking system. Oxidised silicon is of great interest due to the fact that many wafers are silicon based. Here I demonstrate the device’s lasing performance such us output power, spectral tunability, single and multiple laser cavity operation using imaging and pump beam shaping techniques. Phase locked laser arrays were particularly investigated with respect to their mutual phase relationship on a silicon dioxide substrate.Models were developed to simulate waveguiding inside the membrane quantum well lasers and therefore, the display the guided transverse electric and magnetic modes to extract information such as effective and group refractive index and free spectral range between the laser’s longitudinal modes. An attempt was also made to simulate laser arrays based on gain – guiding. Tantalum pentoxide rib waveguides and micro – ring and racetrack resonators were fabricated inside a cleanroom via photolithography and electron beam lithography for comparison. Transmission spectra were acquired from the structures to calculate optical losses, quality factors, resonant probe wavelengths in the vicinity of 1.55 μm, linewidth full – width at half – maximum, free spectral ranges and resonator finesse. Despite quality factors being of the order of 10^5, no Kerr frequency combs were observed.Models were developed to simulate waveguiding in tantalum pentoxide linear waveguides and resonators, from which effective refractive indices and effective areas were extracted after sweeping the probe wavelength. A numerical model was created and introduces the propagation mode parameters to generate Kerr frequency combs.<br/