Reflective-focused laser differential interferometer

This paper presents the design of a novel variation of a focused laser differential interferometer (FLDI), to our knowledge, called a reflective FLDI (R-FLDI). R-FLDI is shown to provide improved versatility compared to a traditional FLDI instrument-the use of a reflective surface enables a wider range of measurement locations while only requiring one optical access point. Various benchtop configurations of traditional FLDI and R-FLDI instruments were used to probe the exit of a sonic jet translated along the beam propagation axis. Results from these experiments demonstrated that the R-FLDI instrument retained the advantages of a traditional FLDI setup while offering enhanced versatility and maintaining performance within acceptable ranges.