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.

A waveform graph displaying current changes over time, with sharp overshooting transitions and stable sections. The scale is in millivolts.
Close-up of two identical circuit boards, the top output is shorted with copper. The bottom one has a laserdiode attached.

approx. 3,5ns


2

Laser diode with self made stripline.

Length: 100 mm

A blue waveform graph displaying current changes over time, with sharp transitions and a stable baseline.
A circuit board with multiple components and a long, flexible flat copper strip attached to short the output.

approx. 7ns


3

A laser diode with long legs.

A waveform graph displaying current changes over time, with semi sharp transitions and a stable baseline.
A close-up of a circuit board featuring electronic components, including capacitors and a small Laserdiode attached to the output.

A laser diode with long legs.


4

Laser diode with round litz wires.

Length: 100 mm

A waveform graph displaying a current signal over time, showing a gradual decay followed by a rapid incline.
A close-up of a circuit board with several components and a twisted red wire attached to the output.

> > 130ns