Real-time imaging of grating formation in LiNbO3:Fe using Mach-Zehnder interferometer

Abstract

A setup for observing formation of light-induced diffraction grating in LiNbO 3 : Fe in real time is presented. The utilization of this setup allows monitoring the temporal dependence of the diffraction efficiencies of several diffraction orders and observing the temporal evolution of the grating by means of the Mach-Zehnder optical interferometer at the same time. The part of the setup responsible for imaging of the space-time distribution of the refractive index changes in a crystal is advantageous to those making long-period gratings in various photorefractive materials because of easy and direct readout of both the grating spacing and the amplitude of the refractive index modulation. These two parameters are well controlled, and the recording of the grating can be stopped after desired values are reached.

Lithium Niobate-Based Integrated Photonics Utilizing Photorefractive Effect

“…The existence of the recorded grating can be proved by diffraction of an extra light beam of a different wavelength (e.g. red line of He-Ne laser) as was the wavelength of the recording beams or by putting the crystal into one arm of Mach-Zehnder interferometer, for example, or both [18]. As the grating is represented by a region of spatially modulated refractive index, it behaves like a phase object and can be imaged by means of an interferometer.…”