Technology for Polarization Measurement

Delay Pulse Generator, DPG 5000

The Delay Pulse Generator 5000 is a precision timing device used in precise timing applications. It has two outputs and a reference input. All precision timing transitions are referenced, or delayed, from the rising edge of the reference input, which must be present in order for the device to operate. If no reference input is present, the device will not output pulses. The device uses a delay table, whose values are entered by the user. The delay range is 50 - 40950 nSec, with resolution of 10 nSec, and can accept up to 12 entries. When the device is not operating, the two outputs present a high impedance output.
Why do you need to use a DPG with a PEM?

The PEM is a resonant device that cycles through polarization states in 15-25 microseconds (for an I/FS50 the frequency is nominally 50 kHz, the period 20µs). For a given device, this frequency and period cannot change. A continuous light source will have its polarization modulated at the PEM frequency. However, a pulsed light source will require timing compatibility such as that provided by the Delay Pulse Generator to synchronize with a PEM in a polarization application set up.

DPG Graph
When is a DPG 5000 needed?

Mostly for pulsed lasers with rep rates slower than 1 MHz

For example:

An 80 MHz pulsed laser is fast enough – approximately 1600 pulses in a PEM cycle - to use a PEM without a timing device.

A 250 kHz laser is not fast enough – it only pulses 5 times per PEM cycle.

A 1 kHz pulsed laser is too slow – it only pulses 1 time in 50 PEM cycles.

What is needed to use the DPG 5000 with a PEM?

The pulsed laser must be capable of being triggered externally. The PEM’s reference signal must be the master.

What type of applications benefit from using a DPG?

For example, you may want to do a circular dichroism experiment. By triggering from the DPG you can set up the experiment so that the laser pulses alternate between left circular and right circular polarization.

Contact us to learn more about Hinds Instruments' Pulse Delay Generator.