High-speed random access laser tuning

We have developed a technique for laser tuning at rates of 100 kHz or more using a pair of acousto-optic modulators. In addition to all-electronic wavelength control, the same modulators also can provide electronically variable Q-switching, cavity length and power stabilization, chirp and linewidth control, and variable output coupling, all at rates far beyond what is possible with conventional mechanically tuned components. Tuning rates of 70 kHz have been demonstrated on a radio-frequency-pumped CO, laser, with random access to over 50 laser lines spanning a 17% range in wavelength and with wavelength discrimination better than 1 part in 1000. A compact tuner and Q-switch has been deployed in a 5-10-kHz pulsed lidar system. The modulators each operate at a fixed Bragg angle, with the acoustic frequency determining the selected wavelength. This arrangement doubles the wavelength resolution without introducing an undesirable frequency shift.