ТеО2 blanks for Acousto-Optical Modulators

Elent A offers TeO2 blanks for acousto-optical Modulators (AOM) – TeO2 crystals cut, oriented, polished and in case of customer request coated.

Typical offered sizes are

  • 9 mm (110) х 10 mm (1-10) х16 mm (001)
  • 11 mm (110) х 12 mm (1-10) х 19 mm (001)
  • 14 mm (110) x 13 mm (1-10) x 20 mm (001)
  • 16 mm (110) x 17,5 mm (1-10) x 32 mm (001)
  • 18 mm (110) x 14 mm (1-10) x17 mm (001)
ТеО<sub>2</sub> blanks for acousto optical modulators 5

But we are not limited by standard sizes, we also can offer ТеО2 crystals produced according to your specific requirements.

For your information please find below some technical information that probably can be useful for you. Also in case of any additional question please don’t hesitate contact us.

Acousto-optic modulator (AOM) is a device which can be used for controlling the power, frequency or spatial direction of a laser beam with an electrical drive signal.

Acousto-optic modulators find many applications:

  • Q switching of solid-state lasers. The AOM, called Q-switch, serves to block the laser resonator before the pulse is generated. In most cases, the zero-order (not diffracted) beam is used under lasing conditions, and the AOM is turned on when lasing should be prohibited.
  • AOMs for cavity dumping of solid-state lasers, generating either nanosecond or ultra-short pulses.
  • AOM as a pulse picker for reducing the pulse repetition rate of a pulse train, e.g. in order to allow for subsequent amplification of pulses to high pulse energies.
  • In laser printers and other devices, an AOM can be used for modulating the power of a laser beam. The modulation may be continuous or digital (on/off).

Main Acousto-optic modulation principles
AOM is based on the acousto-optic effect, i.e. the modification of the refractive index by the oscillating mechanical pressure of a sound wave.

TeO 2 Blanks for Acousto-Optical Modulators 1

The acousto-optic interaction has also been used to modulate light. In order to match the Bragg condition over the modulator bandwidth, the acoustic beam should be made narrow, as in the case of deflectors. Unlike the case of deflectors, however, the optical beam should also have a divergence approximately equal to that of the acoustic beam, so that the carrier and the sidebands in the diffracted light will mix collinearly at the detector to give the intensity modulation. The actual value of the divergence ratio depends on the tradeoff between desired efficiency and modulation bandwidth. AOM can broaden the dimension of the diffracted beam with respect to the incident beam because of the finite sound field depth L (transducer length) and the oblique propagation angle needed for maximum diffraction in the Bragg regime.

TeO 2 Blanks for Acousto-Optical Modulators 2

In practice it is appeared by the crystal (and transducer) length variation to select the best compromise to solve targeted matters.

One more variant – using focusing optics to divergent optical beam. Diffraction geometry of a focused-beam AOM is shown below:

TeO 2 Blanks for Acousto-Optical Modulators 3

The focused-beam-type AOM has certain disadvantages. The diffraction spread associated with the narrow optical beam tends to lower the diffraction efficiency. More importantly, the focusing of the incident beam results in a high peak intensity that can cause optical damage for even relatively low laser power levels. For these reasons, it is desirable to open up the optical aperture. Due to the basic issue of acoustic transit time, the temporal bandwidth of the wide-beam AOM will be severely degraded. In certain applications, such as the laser display system, it is possible to use a much broader optical beam in the modulator than that which would be allowed by the transit time limitation.

Reference list:

  1. Xu J and Stroud R 1992 Acousto-Optic Devices (New York:Wiley)
  3. Goutzoulis A and Pape D 1994 Design and Fabrication of Acousto-Optic Devices (New York: Dekker)