Acousto-Optic Modulators are used for fast laser beam switching and for precise wavelength tuning of a laser light. AOM's modulating crystal has it's own vibration frequency window. If one wants to shift laser light frequency for amount from outside of the window, one must use two or more AOMs in series. For example, a tuning of the wavelength is often accomplished by using two modulators with frequency difference between them equal to the desired detuning of the original laser beam. Frequencies of these crystals must fall within their active range. Adding to the frequency of the laser light the frequency of first modulator and subtracting the frequency of the second one results in the laser beam with desired wavelength.
Our device guaranties the precise and very stable frequency difference between modulating crystals, so the detuning of laser light is also stable. We could achieve this goal by means of digital frequency synthesis in every driver with common clock source driving and synchronizing all generators.
The set-up of generators driving the modulators is based on the direct digital synthesis (DDS) technique. It consists of USB interface card, clock card and generator cards. Generators can work independently or in sync, with well defined (programmed) phase relationship between them. Each one of them provides both analog and digital amplitude modulations.
All the set-up, once programmed, can work in the real-time mode or can be driven by the PC via USB and external digital inputs.
The software controlling the device is delivered for various operating systems, together with source codes, thus allowing for user customization.
