This is the thermal image of a quantum cascade (QC) laser in action -- i.e., lasing. The small bright spot inside the circular window is the laser light. QC laser light is generally invisible to the eye due its emission wavelength, so it is quite fascinating to see it through a thermal camera. The laser is mounted on a cryostat heat sink and held under vacuum using a cryostat holder with a window from which the laser mount is visible. This measurement was taken at -193 C and inside the round window everything is blue except for the bright spot of the laser light.