Fiber coupled acoustooptic device
How to realize the function of menu frequency reduction by acousto-optic menu selector
The acoustooptic menu selector is an acoustooptic driver developed for ultra-fast laser applications that integrates synchronization, triggering, frequency division and delay. With the corresponding acoustooptic modulator module, it can realize the functions of frequency reduction and pulse selection for various repetition rate pulse lasers. It has the characteristics of high control accuracy, small size and convenient adjustment, and is the key device for realizing frequency reduction and pulse selection functions of ultra-fast laser system.
1. Principle of acoustooptic modulator
The acoustooptic modulator consists of a device and a driving power supply. The device is composed of an acoustooptic crystal and a matching network. It mainly uses the basic principle of acoustooptic interaction. The RF electrical signal output by the driving power supply is applied to the piezoelectric transducer of the acoustooptic crystal through the impedance matching network. The piezoelectric transducer converts the signal into ultrasonic wave and propagates in the acoustooptic crystal to form a refractive index grating. When the laser passes through at a certain angle, Bragg diffraction occurs, The amplitude modulation function of the optical signal is achieved by modulating the output power of the electrical signal.
2. Menu implementation of high repetition rate signal
The frequency reduction and selection of high-frequency signals is actually a process of selecting useful pulse signals through acoustooptic modulator and filtering other signals.
The switching time of the optical fiber acoustooptic modulator is determined by the repetition frequency of the high-frequency pulse signal
Set the repetition frequency of the laser pulse to f0, then the bottom width of the switch signal of the acoustooptic modulator should be less than 2/f0. The parameter to measure the switch time of the optical fiber acoustooptic modulator is the optical pulse rise time. Therefore, the optical pulse rise time of the optical fiber acoustooptic modulator is 1/f0 from 0-100% of the region length. For example, take the repetition frequency of the optical fiber laser as 40 MHz