The model LDC-3700B Series Laser Diode Controllers conveniently offer both laser diode current and temperature control in the same instrument. Each unit is a dual-range current source offering 16 W TEC and 200/500 mA current. Each controller offers a low noise, highly stable current source operating in one of three modes: constant current, high bandwidth or constant optical power. Mode 1 is optimized for DC operation, supports external modulation and offers improved laser protection and noise performance. In Mode 2, the output stage supports higher frequency, external modulation with control circuitry optimized for high bandwidth operation of up to 1 MHz. Mode 3 supports constant optical power operation, using photodiode input current as the control setpoint.