Gaussian beam diffraction by two-dimensional refractive index modulation for high diffraction efficiency and large deflection angle

Abstract

The propagation of Gaussian beams is analyzed for an acousto-optic deflector by varying the refractive index in two-dimensions with a row of phased array piezoelectric transducers. Inhomogeneous domains of phase grating are produced by operating the transducers at different phase shifts, resulting in two-dimensional index modulation of periodic and sinc function profiles. Also different phase shifts provide a mechanism to steer the grating lobe in various directions and, therefore, the incident angle of the laser beam on the grating plane is automatically modified without moving the beam. Additionally, the acoustic frequency can be varied to achieve the Bragg condition for the new incident angle of the laser beam so that the diffraction efficiency of the deflector is maximized. The Gaussian beam is expressed in terms of planes and the second order coupled mode theory is implemented to analyze the diffraction of the beam. The diffraction efficiency is found to be nearly unity for optimal operating parameters of the acousto-optic device.

Optical image processing using acousto-optic modulators as programmable volume holograms: a review [Invited]

“…The use of AOMs operating in the Bragg regime for 2D image processing was pioneered by Xia et al [8] , and the research is built on the concept of acousto-optic transfer functions first introduced by Poon and Chatterjee [31] . The concept of transfer functions has also been used for the investigation of beam shaping and beam distortion in thick gratings [16][17][18]32] .…”

“…(17). Indeed, the conversion from a Gaussian laser beam into flattop profiles has been investigated using the transfer function of the first-order beam, which has many important applications such as laser fusion, laser printing, and optical data processing [15][16][17][18][19]32] . Figure 8 shows an example of flattop profile shaping of a Gaussian laser beam upon Bragg diffraction for the first-order diffracted beam in the far field.…”

“…Davis and Nowak performed operations similar to those obtained with both the fractional Hilbert transform and fraction derivative spatial-filtering operations [14] . Along the line of image processing by acousto-optic Bragg processing, beam shaping has been investigated [15][16][17][18][19] . The use of anisoptropic Bragg diffraction to perform image edge extraction was first, to the best of our knowledge, demonstrated by Voloshinov et al in 2002 [20] .…”

Simulation and in vivo investigation of light-emitting diode, near infrared Gaussian beam profiles

“…In this regard, the scattering factor used in this study is Lipovenoes containing higher anisotropy factor than intralipid. 53 The employed Lipovenoes10% solution was diluted with deionized water to a low concentration of 0.288% which was obtained experimentally.…”

“…27,51,52 In order to be conducted the scanning process, a liquid phantom with a scattering medium made of diluted Lipovenoes10% was used. 53 In the first step of this study, another approach which was also applied to compare the performance of the two proposed light beam profiles was the simulation of a vessel in the phantom having the role of the veins in the brain tissue. It was simulated so that an aqueous Indian ink suspension is pulsated in the vessel in different depths within the scattering medium.…”