PULSED LASER DIODE DRIVERS

What is a Pulsed Laser Diode Driver?

Pulsed drivers are specialty current sources that offer pulse repetition rates in the range of single shot up to roughly 500 MHz. They are designed to deliver constant current levels from 10's of milliamps up to 100's of amps. They are constant current sources which are designed and optimized to produce clean current pulses at a user-set amplitude and at a user-set pulse repetition interval and/or pulse width. A "clean" pulse is usually defined in terms of its lack of overshoot and a low amount of noise on the pulse. They are almost always square wave / TTL pulses. In the laser diode industry, analog modulation usually refers to sinusoidal wave forms in the 100's of kHz range, and "pulsed" usually refers to square wave TTL pulses. They are often chosen on the shortest (most narrow) pulse width that they can deliver to the laser.

Their output to the laser is defined by the current amplitude and the pulse time base parameters. They typically have over-voltage clamping and usually have an anolog current limit to protect the laser. The output current amplitude and the pulsing time parameters are often the only parameters that you can set and adjust. Many times, the pulse time paramaters are pre-set and dthe manufacturer and you need to order a specific pulse width and rep. rate. You will typically not see an adjustment for output voltage. Manufacturers specify the voltage in terms of the total range that the pulser can handle. It's known as the compliance voltage. This is the available range of output voltage of a constant current source to the load. It is the total amount of voltage a current source will reach as it attempts to produce the desired current. Some of the well know manufacturers include Alphanov, Analog Modules, PicoLAS and Newport.

Choosing the best model for your application can be very time consuming. The fast pulse driver market for lasers is highly fragmented and controlled by a handful of companies. We put together a guide which will hopefully provide you with a basic understanding of the most important factors to consider when making your choice and a list of the top manufacturers of pulse drivers: How to Select a Pulsed Laser Diode Driver for your Application »

Important Spectral Emission Considerations when Choosing the Pulse Width:

When choosing a pulsed current source for your laser, it is important to keep in mind the response time of the type of laser diode you intend to pulse. For example, with fiber Bragg grating stabilized lasers (FBG), there is an inherint time period (lag) required for the laser to lock onto its Bragg locking element. This locking is almost immediate for a DFB or DBR, but it often requires more than 100 nanoseconds for an FBG based laser. When pulsing a Grating stabilized laser diode, the first nanosecond produces a broad emission spectrum as if there were no Bragg grating present. Some suppliers such as Lumics offer an intermediate solution that offers the Bragg closer to the chip which reduces this locking time lag to a few nanoseconds.