Direct determination of 2D Momentum Space from 2D Spatial Coherence of Light using a Modified Michelson Interferometer

Abstract: Momentum space distributions of photons coming out of any light emitting materials/devices provide critical information about its underlying physical origin. Conventional methods of determining such properties impose specific instrumentational difficulties for probing samples kept within a low temperature cryostat. There were past studies to measure one dimensional (1D) coherence function which could then be used for extracting momentum space information as well as reports of measurements of just two dimensional (2D) coherence function. However, all of those are associated with additional experimental complexities. So, here we propose a simpler, modified Michelson interferometer based optical setup kept at room temperature outside the cryostat to initially measure the 2D coherence function of emitted light, which can then be used to directly estimate the 2D in-plane momentum space distribution by calculating its fast Fourier transform. We will also discuss how this experimental method can overcome instrumentational difficulties encountered in past studies.