Semiconductor Ring Lasers

[摘要] Miniature rib ring waveguide and pill-box laser structures as small as 12 mum in diameter were investigated. Output stripe waveguides were coupled to the rings via Y-junctions. Optical properties of the component structures were analysed using the finite difference method. The original waveguides were defined in GaAs/AlGaAs heterostructure materials by reactive ion etching through the pattern of the guide contacts with the connected bonding pads. The fabrication was then simplified by embedding the etched guides in polyimide and overcoating with a gold bonding layer. Temperature stable ohmic contacts were designed to improve the stability of the devices. Material designed with a localised gain region quantum well and an additional coupled passive guide provided single mode operation even for the broad area devices. The performance of the rib ring laser structures was comparable to that of similar size straight lasers. Standard structures defined by optical lithography in DH and QW materials lased successfully. E-beam defined devices with successively narrower ribs down to 0.4mum, and shorter ring cavities down to 12mum in diameter, increased the optical loss. This resulted in increased threshold density up to 220kA/cm2 for ring lasers made of DH material, and a lack of lasing for small structures made of QW material, where the relation is more critical. The QW devices showed evidence of both first and second quantised state operation. This type of ring laser structure is suitable for use as a light source in monolithic, integrated optics, although absorption loss due to the gold bonding layer must be eliminated to reduce threshold current of the devices.

[发布机构] University:University of Glasgow

[关键词] Electrical engineering