Spatiospectral transformation of noncollimated light beams diffracted by ultrasound in birefringent crystals

Abstract

Spatiospectral structure of wave phase matching in birefringent crystals has a strong dependence on the geometry of the acousto-optic interaction and incident light spectrum. This dependence defines details of light beam profile transformation. It is especially important for imaging applications related to a large angular aperture and a wide spectral bandwidth of the incident light. In this paper, we demonstrate accurate three-dimensional plotting of a light transmission pattern without small birefringence approximation. The rather complicated shape of the phase-matching locus in the spatiospectral domain inevitably leads to residual spatially nonuniform chromatic aberrations in the spectral image. Theoretical consideration and computational modeling are confirmed by the experiments on Bragg diffraction in paratellurite crystal. The results are especially important for the development of acousto-optical imaging devices and laser beam shaping technologies.

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.…”

Multi-wavelength off-axis digital holographic microscopy with broadly tunable low-coherent sources: theory, performance and limitations

“…The main equation for AO diffraction may be derived from the Bragg condition k d = k i ± q, where q, k i and k d are the wavevectors of sound, incident and diffracted light, respectively. The widely used AOTFs for visible and near-infrared light utilize the non-collinear anisotropic AO interaction in paratellurite (TeO 2 ) crystal because of its high diffraction efficiency and the ability to separate filtered and unfiltered beams by polarization [34][35][36][37][38][39][40][46][47][48][49]. In this case, the phasematching condition may be illustrated by the wavevector diagram (figure 4(a)), where the wavenumbers of incident and diffracted light beams are k o (λ) = 2πn o (λ) /λ and k e (λ) = 2πn e (λ) /λ, n o and n e are the refractive indices for ordinary and extraordinary polarized waves.…”

The Calibration Methods of Geometric Parameters of Crystal for Mid-Infrared Acousto-Optic Tunable Filter-Based Imaging Systems Design

“…The main equations describing AO interaction may be derived from the laws of the conservation of energy and momentum for photons and a phonon [ 36 ]: where , , and are the frequencies and wavevectors of sound, incident light, and diffracted light. The sign “ ” corresponds to the absorption of the phonon, and the sign “ ” corresponds to its stimulated birth.…”