Simple Simultaneous Modulation for Red, Green, and Blue Laser Lights Using Surface-Acoustic-Wave-Driven Acoustooptic Modulator

An acoustooptic modulator (AOM) driven by a surface acoustic wave (SAW), in which laser light of the three primary colors, red, green, and blue (RGB), can be modulated by the same modulator at the same driving frequency, was investigated. To suppress the light power leaked to the outside of the waveguide, a waveguide-type AOM with a 3.5-\mbox{$\mu$m}-deep waveguide was fabricated. The RGB laser lights were modulated with the diffraction efficiencies of 73--85% and a driving SAW power of less than 0.2 W at the same driving frequency of 245.5 MHz. By combining the AOM module, laser sources, WDM couplers, and fiber delay lines, a simple simultaneous modulation for RGB laser lights was proposed and constructed. On the basis of the designed properties, the switching time of the output signal from the constructed system equipped with the AOM with the three-finger-pair interdigital transducer (IDT) was demonstrated to be 28 ns.