ТеО2 for Acousto-Optfic Application

ТеО<sub>2</sub> Blanks for Acousto-Optical Deflectors
ТеО<sub>2</sub> blanks for Acousto-Optical Modulators
ТеО<sub>2</sub> blanks for AO Tunable Filters

ТеО2 material, thanks to specific properties, is considered as the best material for Acousto-Optical (AO) application, especially AO Deflectors, AO Modulators and AO Tunable filters. We hope that some technical information given below will help you to define what kind of ТеО2 you need for your particular purposes and our technical specialists are always open for discussions.

We now consider the diffraction of light by acoustic waves in an optically transparent medium in which the acoustic wave is excited. An optical beam is incident onto the cell and travels through the acoustic beam. Via the elasto-optical effect, the travelling acoustic wave sets up a spatial modulation of the refractive index that, under proper conditions, will diffract the incident beam into one or more directions.
The AO interaction can be viewed as a parametric process where the incident optical wave mixes with the acoustic wave to generate a number of polarization waves. The polarization waves in turn generate new optical waves at various diffraction orders.

ТеО2 Acousto-optical Application 1
But the most interesting particular case is Bragg diffraction.
In the Bragg limit, only the first-order diffracted light grows to a finite amplitude.
ТеО2 Acousto-optical Application 2
Wave vector diagram of Bragg diffraction in an optically anisotropic medium such as a birefringent crystal (ТеО2) is shown below.
ТеО2 Acousto-optical Application 3

Significant diffraction of light occurs only when the exact momentum matching is met.

In the general case of AO interaction in an anisotropic medium, the magnitudes of the wave vectors are given by:


where Λ=V/f  is the acoustic wavelength, and V and f are the velocity and frequency of the acoustic wave.
In general, the refractive indices of the incident and diffracted light beams are different.
As an example, consider the Bragg diffraction in a positive uni-axial crystal.
From the wave vector diagram shown in the above figure and using the law of cosines one obtains:

One of the main parameters is diffraction efficiency that is given by

where Pa is the acoustic power, H is the acoustic beam height, ρ is the mass density, V is the acoustic wave velocity, and  is a material figure of merit.

The diffraction efficiency is thus linearly proportional to acoustic power.
ТеО2 crystal has extremely high AO-efficiency (М2 = 793 х 10-18 s3/g and up with defined geometry interaction) that allows to use Paratellurite for low acoustic power with out decreasing diffractive efficiency in comparison with other materials.
As acoustic power increases, the diffraction efficiency saturates and approaches 100 percent.
Thus in the Bragg regime, complete depletion of the incident light is obtainable.
These features give possibility efficiently design all types of AO-devices with technical characteristics permitting, particularly, refuse from high-power cooling systems as well as construct a number of unique AO-devices, for instance, AOTF with high aperture to process images of multichannel devices.

Reference list:

  1. Xu J and Stroud R 1992 Acousto-Optic Devices (New York:Wiley)
  2. Handbook of optics. CHAPTER 12 ACOUSTO-OPTIC DEVICES AND APPLICATIONS I. C. Chang
  3. Goutzoulis A and Pape D 1994 Design and Fabrication of Acousto-Optic Devices (New York: Dekker)