Widefield two laser interferometry

Abstract

A novel system has been developed that can capture the widefield interference pattern generated by interfering two independent and incoherent laser sources. The interferograms are captured using a custom CMOS modulated light camera (MLC) which is capable of demodulating light in the megahertz region. Two stabilised HeNe lasers were constructed in order to keep the optical frequency difference (beat frequency) between the beams within the operational range of the camera. This system is based on previously reported work of an ultrastable heterodyne interferometer [Opt. Express 20, 17722 (2012)]. The system used an electronic feedback system to mix down the heterodyne signal captured at each pixel on the camera to cancel out the effects of time varying piston phase changes observed across the array. In this paper, a similar technique is used to track and negate the effects of beat frequency variations across the two laser pattern. This technique makes it possible to capture the full field interferogram caused by interfering two independent lasers even though the beat frequency is effectively random. As a demonstration of the system's widefield interferogram capture capability, an image of a phase shifting object is taken using a very simple two laser interferometer.

Time and Space Resolved First Order Optical Interference Between Distinguishable Photon Paths

“…If separate lasers are used, the frequency difference varies from shot to shot and so does the fringe pattern [9]. The fringes in most of these experiments with different frequencies have been observed using a streak camera and more recently, with a modulated CMOS camera [10].…”

Introductory Chapter: Optical Interferometry in Interdisciplinary Applications

“…Optical interferometry (OI) involves the superposition of electromagnetic waves to form interference fringes where tiny changes in optical path difference cause significant variation in the intensity pattern of the detected light. The precision and flexibility associated with modern-day interferometric techniques have enabled researchers to apply them to a wide range of applications for solving problems related to science and engineering [1][2][3][4][5][6][7]. In the recent years, applications have become more sophisticated.…”

Observation of two truly independent laser interference made easy

“…From the scientific point of view, a direct imaging of the transient interference pattern in the classical and quantum regime is continuously an area of interest (see e.g. [8][9][10]), although these experiments require sophisticated equipment such as streak cameras or modulated light cameras.…”