Physics Chat
Vertical Cavity Surface Emitting Laser (VCSEL) device and material characterisation
Speaker: Curtis Hentschel (Peter M. Smowton's group)
Date: Thursday 20 October 2022
Time: 14:00
Venue: Queen's building WX3.07 with zoom live streaming
Vertical cavity surface emitting lasers (VCSEL) are a type of semiconductor laser where optical emission is from the surface of the wafer (as opposed to the edge for in-plane devices). The typical VCSEL structure consists of active layers that have been sandwiched by epitaxially grown distributed Bragg reflector (DBR) layers, to form a vertical cavity with a high quality factor. There may also be a thin high Al concentration AlGaAs layer in close proximity to the active layers, which when oxidised, forms an aperture that provides optical and current confinement. In the 1st part, I will present the measured device performance of VCSELs that have been designed for use in miniaturised atomic clocks (MAC). The impact of the oxide aperture dimensions on device characteristics such as the optical power, wavelength, single-mode performance and divergence angle will be discussed. In the 2nd part, I will present gain measurements performed directly on VCSEL material using a stripe-length method variant known as the segmented contact technique. The stripe length method is an in-plane technique, and I will discuss how the measured optical gain in the in-plane direction relate to the vertical direction.