Application Note: Laserdiode-Connections

Related Products: All PicoLAS short pulse driver

The connection of the laser diode to any of the PicoLAS short pulse drivers is very critical. A wrong connection, the wrong decision about the connection cable etc. will result in slow rise times. This application note shows the measured effects of different connections to the laser diode in respect to the rise times.

The used driver is a LDP-V 50-100.
The parasitic stray inductive behavior is the most important influence of the cables. Due to the skin effect, copper thickness is not relevant for short pulses.

Connection type

Current

Setup image

Current risetime


1

A short immediately at the output of the driver with a low impedance ribbon. Make sure that this is recommended in the manual.

Same values can be achieved with a diode connected directly to the unit.

The output graph of the current from the LDP-V driver, when the output is directly shorted or a laserdiode is mounted correct. The risetime is not effected the full performance is reached.
A high precission laserdriver with a shorted output and a laserdiode directly attached to the driver to show how this effects the performance of the driver.

approx. 3,5ns


2

Laser diode with self made stripline.
Length: 100 mm

The output graph of the current from the LDP-V driver, when a a flat cable is shorting the output. The risetime is a bit longer than usual.
A high precission laserdriver with a flat cable shorting the output of the driver to show how this cable type effects the performance of the driver.

approx. 7ns


3

A laser diode with long legs.

The output graph of the current from the LDP-V driver, when a laserdiode with long legs is connected to the output. The first risetime is longer than usual.
To our LDP-V laserdriver is a Laserdiode connected horizontal to the output with long legs.

approx. 12ns


4

Laser diode with round litz wires.
Length: 100 mm

The
A high precission laserdriver with a red twisted litz wire shorting the output of the driver to show how this cable type effects the performance of the driver.

> 130ns