Programmable Focused Laser Differential Interferometer with a Spatial Light Modulator As a Dynamic Diffractive Optical Element.

A spatial light modulator (SLM) is incorporated into a focused laser differential interferometer (FLDI) to generate a nonlinear array of beams, and this setup is used to measure the power spectral density of a Mach-1.5, underexpanded jet of air. The results are compared with measurements from a 1-point FLDI to assess the feasibility of using SLMs in FLDI to serve as dynamic diffractive elements for generating beam arrays of any shape. The spectra comparison illustrates that spatial light modulated-FLDI (SLM-FLDI) detects similar spectral profiles to that of 1-point FLDI, especially dominant frequencies in the jet. SLM-FLDI could provide a useful expansion of FLDI capabilities.