A modified Mach-Zehnder inferometer for the study of coherence of laser

Abstract

The coherence property of the laser light is an important aspect for the understanding of the optical physics. A modified geometry of the Mach-Zender interferometer has been proposed for measurement of the coherence of the laser. The geometry of the mirrors has been arranged in such a way that the reversible shear interferometer and the Michelson interferometer, both the types of the interferometers are set-up in a single geometry. Using this interferometer, the spatial and the temporal coherence of the laser beam can be measured .The interferometer is simple in design and is useful in the computer assisted visual learning of the coherence at the college and university level education and teaching in optics. Keywords Interferometry,Coherence , Optics SummaryThe coherence property of the laser light is important in understanding of the laser /optics and its various applications in holography etc. The reversible shear interferometer1 provides the measurement of the spatial coherence and the Michelson interferometer measures the temporal coherence of the laser. The conventional young slit method for spatial coherence measurement is not suitable for large diameter laser beams and it also requires multiple measurements. In this paper, a modified geometry of Mach Zender interferometer has been reported which can be used for the spatial coherence in a single measurement as well as for the temporal coherence measurement of the laser beam. The interferometer can be easily used in the large diameter laser beams .The schematic of the interferometer has been shown in the figure-1. Its mirror geometry is similar to the Mach Zender interferometer, the W1 and W2 are two wedges at 450 and mirror M3 is mounted on the translation stage. The incident laser beam is split at wedge W1 and recombine at wegde W2. The one part of the laser beam propagating in the path W1!M1!M2!W2 and the other beam propagating along the path W1!W2!M3!W2, both the beams combine at wedge W2. C is the compensating plate. The wavefront from the earlier path is inverted along a line of folding.

Mach-Zehnder-based measurement of light emitting diodes temporal coherence

“…1, to experimentally measure the temporal coherence of so-called non-coherent sources, such as LEDs. Different configurations of Mach-Zehnder interferometer have been used to measure the coherence degree of light sources such as lasers, [20][21][22], but we apply it to non-coherent sources for the first time. The Mach Zehnder interferometer offers more robustness and portability than other kinds of interferometers.…”