Temperature Dependence of Vertical Cavity Surface Emitting Lasers

The first picture shows the Helium cryostat in which the VCSEL sample is placed before undergoing cooling. The insert, extends all the way down the cryostat holding the laser under test and allows for electrical connections to be carried within the cryostat.

To maintain the a low level of heat loss within the cryostat, liquid Nitrogen within the cryostat is kept behind a high-vacuum created by the combination of a rotary and diffusion pump system.

With the device at the bottom of the cryostat, the quartz windows allow the light to be transmitted via free-space optics to measuring equipment. In this case, a GaAs water cooled photomultiplier.

The windows also allow the device to be pumped by a light emitted from a pump source laser. Depending on the band-gap of the material, we can use different lasers to inject carriers into the device.

Schematic diagram showing the major elements of the temperature dependence experiment.