PCAOM is Poly-Chromatic Acousto-Optic Modulator.

POLYCHROMATIC ACOUSTO-OPTIC MODULATOR PCAOM:

A normal AO modulator is designed to modulate only one wavelength of laser light as the Bragg angle must be changed for any other wavelengths of light. A special class of modulators has been developed to modulate multi-wavelength or white light lasers. These modulators are known generally as Acousto-Optic Tunable Filters or by the light show industry, as Poly-Chromatic Acousto-Optic Modulators, and is based on the work of I. C. Chang using Tellurium Dioxide (TeO2) crystals in the slow shear mode. The wavelength tuning curve for these modulators are shown in figure.

The angle between the diffracted beams for the different wavelengths is 2.5 degrees for a normal TeO2 device. By designing a small prism to compensate for the angular variation, and by taking advantage of the dispersion property, the net angular deviation of the different wavelengths diffracted is reduced to .002 degrees. Since this is within the normal beam divergence of the laser beam, the output can be considered to be co-linear. This allows one PCAOM modulator to be used in the light show industry to modulate the multi-wavelength lasers instead of using several different modulators,one for each wavelength.

PCAOM ist the abbreviation for Polychromatic Acousto-Optic Modulator. Unlike an AOM (acousto-optic modulator), which can only deflect a single wavelength, the PCAOM is able to deflect several different wavelengths at the same time. PCAOMs were used for laser shows of gas laser systems in order to control blanking and color (fading) behaviour.

The number of channels of a PCAOM specifies the possible frequencies and thus the number of possible wavelengths. A PCAOM allowed high-speed electronic blanking, intensity control and color selection of a multi-color laser beam of a mixed gas laser (white light, purelight)

The PCAOM makes multiple parallel independent electrodes in the acousto-optic medium. It produces independent driving signals. It has multiple parallel ultrasonic signals in the acousto-optic medium .

An expanded laser beam can interact with each ultrasonic signal at the same time to produce the diffracted light array.

Gooch and Housego Polychromatic Acousto-Optic Modulators (PCAOM)

Polychromatic acousto-optic modulators are a special configuration of an AOTF. The relationship with acoustic wave frequency and diffraction angle causes diffraction of different wavelengths at different diffraction angles. A goal of the PCAOM is to maintain all the diffracted wavelength collinearity on the same beam path as they exit the crystal. Consistent batch-to-batch material quality and strict manufacturing processes insure this on a routine base. The high modulation rae of the diffracted beam also distinguishes the PCAOM. Optimizing drive power, beam collinearity, wavelength range, diffraction efficiency and acceptance angle can yield video bandwidths of a few megahertz ideally suiting them for laser displays and other dynamic phenomena visualization.