Abstract
A scheme for controlling the frequency difference of output pulse pair with double frequency shift loops is proposed. The frequency shift system includes two loop elements of 20 and 200 MHz. The first one carries out a single selective positive frequency shift of 1–20 MHz, and the second one can satisfy a single fixed positive frequency shift of 200 MHz. The reverse cascade technology of two acousto-optic crystals is introduced to solve the limitation of the small frequency shift of crystal size. A multichannel synchronization signal completes the time domain control of each acousto-optic modulator. Finally, the frequency shift difference of the output pulse pair ranges of 0–2 GHz, and the frequency shift accuracy is 5 MHz.
Highlights
Since the discovery of light diffraction caused by ultrasound wave [1], researchers have made an in-depth exploration of acousto-optic interaction [2,3,4,5]
They used an acoustooptic effect to modulate the frequency, intensity and propagation direction of optical signal, and design an acousto-optic tunable filter (AOTF) [6,7,8], acousto-optic deflector (AOD) [9,10,11], acousto-optic modulator (AOM) [12,13,14] and other optical devices, which are widely used in optical communication, laser control, spectrum detection and other fields [15,16,17]
When the light is injected into the crystal, the optical signal is affected by the “grating” and produces a diffraction effect
Summary
Since the discovery of light diffraction caused by ultrasound wave [1], researchers have made an in-depth exploration of acousto-optic interaction [2,3,4,5] They used an acoustooptic effect to modulate the frequency, intensity and propagation direction of optical signal, and design an acousto-optic tunable filter (AOTF) [6,7,8], acousto-optic deflector (AOD) [9,10,11], acousto-optic modulator (AOM) [12,13,14] and other optical devices, which are widely used in optical communication, laser control, spectrum detection and other fields [15,16,17]. Li et al [22] completed the small-scale phase-modulation of incident light by using a series structure of two polarization-insensitive AOMs. If the frequencies of two RF drive signals are different, the structure can achieve a small frequency shift of the output light. Under the control of high-precision and low jitter synchronization signal, the maximum output frequency shift difference is 2 GHz, and the frequency shift accuracy reaches 5 MHz
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