Acousto-Optic Modulators, Deflectors & Tunable Filters

Acousto-optic modulators (AOMs) control the intensity, frequency or direction of a laser beam using the interaction between sound and light. An applied radio-frequency signal launches an acoustic wave in the crystal, which sets up a diffraction grating that you switch, tune or steer electronically, with no moving parts. Wavelength Optics supplies free-space and fiber-coupled AO devices from 266nm to 10.6μm in single-channel and multi-channel configurations. The range covers modulators, deflectors, frequency shifters and tunable filters, with RF drivers and acoustic absorbers supplied.

Device types and how they work

Free-space and fiber-coupled modulators are generally used outside the laser cavity for amplitude modulation. The RF driver sets the modulation mode. A digital driver gives simple ON/OFF switching. An analog driver gives variable-level intensity control with sinusoidal, square-wave, linear or arbitrary waveforms. The driver usually runs at a fixed frequency. The key parameter is rise/fall time, which sets your achievable modulation bandwidth. Rise/fall time is proportional to the beam diameter inside the crystal, so controlling the incident beam size is how you get a faster response. You can use the same device as a shutter that cycles at a set frequency or as a variable attenuator that dynamically controls transmitted power.

Deflectors (AODF) scan the beam by changing the RF drive frequency. They support random-access positioning, continuous line scanning and sequential point deflection. Response time depends on the crystal, wavelength and beam size. Peak efficiency requires the input beam to be aligned at the Bragg angle. Because alignment is optimal at only one drive frequency, efficiency typically falls off toward the edges of the scan. This trade-off is worth discussing with us early in your design.

Frequency shifters (AOFS) are compact devices built specifically for frequency shifting. Depending on the angle of incidence, the diffracted beam is shifted up or down by the applied RF frequency. You can cascade two or more units to produce sum or difference frequencies. Our AOFS designs use specially angled acoustic absorbers to minimize acoustic reflection and improve efficiency.

Tunable filters (AOTF) are solid-state, electronically addressed, random-access optical passband filters. You can use them to select specific wavelengths from wideband or multiline sources, with electronic control of center wavelength, modulation depth and, in some cases, passband width.

Where AO devices are used

• Laser processing and micromachining: fast ON/OFF shuttering and power control outside the cavity, plus beam deflection for scanning.
• Machine vision and semiconductor inspection: non-mechanical beam steering and intensity control in scanning and illumination systems.
• Spectroscopy and analytical instruments: AOTF wavelength selection from broadband sources, and frequency shifting for heterodyne detection schemes.
• Medical and life-science equipment: variable attenuation and switching of laser sources in imaging and treatment systems.
• Telecommunications and fiber systems: fiber-coupled modulators and frequency shifters for switching and signal-processing setups.

Selecting the right device

The right AOM depends on how your parameters interact. Wavelength drives the choice of crystal. Required speed constrains beam diameter. For deflectors, scan range has to be balanced against efficiency. Fiber type and coupling format matter for fiber-coupled units. Cooling becomes relevant at higher optical or RF power. The specification table on this page lets you filter the catalogue by wavelength, aperture, center frequency, bandwidth, rise time, insertion loss and more. If none of the catalogue parts fits, devices can be customized to your requirements. Send us your laser specifications in as much detail as you can, including wavelength,