Dr. Saifollah Rasouli, Mr. Mohammad Yeganeh,
Volume 7, Issue 2 (International Journal of Optics and Photonics (IJOP) Vol 7, No 2, Summer-Fall 2013)
Abstract
One of the solutions of the Helmholtz equation is the vortex beams. In the recent decades, production and applications of these types of beams have found serious attentions. Determination of the vortex beam topological charge and its sign are very important issues. Odd number of reflections of the vortex beam changes its vorticity. In this paper, we have used a q-plate to generate a vortex beam from a plane wave of a He-Ne laser beam and a two-channel moiré based wavefront sensor is used to measure wavefront gradient of the vortex beam. In two different arrangements the vortex beam experience odd and even number of reflections, respectively, and from the moiré pattern deformations the topological charge of the vortex beam and its sign are determined.
Dr Saifollah Rasouli, Shamsedin Esmaeili, Dr Farhab Sobouti,
Volume 10, Issue 1 (International Journal of Optics and Photonics (IJOP) Vol 10, No 1, Winter-Spring 2016)
Abstract
We have built a vertical seismometer that works based on the moiré technique. One grating is attached to the suspended mass and one to the frame of the instrument. The two gratings are in relative motion, and the resulting moiré pattern magnifies this motion. The intensity of a light beam passing through the moving moiré fringes changes with time, and a light detecting system converts this power fluctuation into a voltage signal. From this voltage signal the time series of ground motion is obtained. We investigated the performance of the instrument theoretically, as well as experimentally. Our instrument can measure the amplitude of oscillation through moiré magnification. It is free from EM environmental noise, has adjustable sensitivity and dynamic range, and has simple and straightforward design. Furthermore, we introduce a novel way of data acquisition from moving moiré patterns.
