The Gooch & Housego, Florida LLCMode Locker Driver utilizes a crystal oscillator with extremely low phase noise to generate the necessary, frequency stable, RF power to drive the Gooch & Housego Mode Locker Modulator. The Mode Locker Driver also temperature tunes the Mode Locker Modulator's transducer resonance to the frequency of the RF crystal oscillator automatically. If desired, the temperature control can be operated under manual control. The Mode Locker Driver output frequency is one half the resonate frequency of the laser cavity. The Mode Locker Driver front panel meter provides relative forward and reflected RF power readings and the thermistor provides temperature information, which is used to monitor the Mode Locker Modulator. The automatic temperature tuning controller monitors the reflected RF power from the Mode Locker Modulator and adjust the temperature until the reflected power is at a minimum. This is the null or resonance of the Mode Locker Modulator, where the standing wave is setup in the optical crystal. This standing wave acts as a shutter that forces the longitudinal modes of the laser to maintain a fixed phase relationship. These modes are separated by a frequency F = C/2L. L = laser cavity length. C = speed of light. "Mode locking" of the laser, is accomplished by adjusting the laser cavity length, so that the round trip time of the laser light is matched to the twice the drive frequency of the Mode Locker Modulator at resonance. Because each laser is unique, NEOS Technologies manufactures each Mode locker / Driver as matched pairs and tuned to match the customers requested resonate cavity length