Each laser diode driver’s laser current source can be operated in one of three modes:

• Constant current, low bandwidth: optimized for DC operation and offers improved laser protection and lowest noise.
• Constant current, high bandwidth: the output stage supports up to 1MHz modulation frequency for dithering the laser current in power and wavelength tuning applications.
• Constant optical power: provides constant optical power operation of your laser diode by measuring the photocurrent from the laser diode’s rear-facet photodiode or an external photodiode in a feedback control loop to the current source.

Laser diodes are extremely sensitive to electro-static discharge, excessive current levels, current spikes, or transients from power surges or other laboratory equipment. One of the most important features we have implemented into each instrument is the ILX Lightwave proven laser diode protection standards. These standards have led to advanced protection features such as independent hardware current limits, a slow-start ramping technique, and isolated supplies. A "clamping" circuit prevents the limits from being exceeded under any condition including current modulation. An output shorting switch provides a safe method of switching the output on and off during operation while protecting the laser during load/unload or connect/disconnect operations. Also, if the instrument senses an open circuit, the output will immediately shut off followed by the illumination of the appropriate fault indicator. During AC power-up, the laser is protected from current transients by power line filters and double shielded transformers. Transients from normal instrument operation such as output on/off have been thoroughly tested and minimized as well as transients from inadvertent instrument operation (such as mode switching). For more information about these protection features, please see our “Protecting Your Laser Diode" application note.