THORLABS GSL Series User Manual page 8

GSL Series Gain-Switched Lasers
The key switch controls power to all internal components. When the key switch is turned on, the temperature
stabilization system is activated. There is a 30 - 60 second warm up, during which time the LED indicator light
blinks. When the LED stops blinking, there is an additional four second delay and then laser is enabled. Note there
will not be any optical output until the interlock is satisfied, a trigger signal is supplied, and the pulse width and
repetition rate combination are in an allowed state as show in the table in section 4.7.
Interlock Circuit
The laser is equipped with a phono-type interlock jack located on the back panel. To enable the laser source, a
short circuit must be applied across the terminals of the interlock connector. The shorting device (interlock pin)
installed in all units shipped from Thorlabs performs this function. Leave the shorting device installed unless using
an external safety circuit or other type of remotely controlled switch to enable laser output.
Making use of the Interlock feature requires the appropriate 2.5 mm phono-type plug, which is shown in the left
diagram of Figure 5 and is readily available through most electronics retailers. The plug should be wired to the
external safety circuit or switch and then plugged into the back panel's interlock jack in place of the shorting
device. The electrical specifications of the interlock jack are listed in the following table, and the circuit schematic
describing how the interlock jack is connected inside the laser head is shown in the right diagram of Figure 5.
Parameter
Interlock Switch Requirements
Type of Mating Connector
Open Circuit Voltage
The user's safety circuit must be attached to the phono plug and wired such that the ring and center pin are
shorted when it is safe to enable the laser. The laser will be enabled when connection is closed. If it changes to an
open state, the laser source will turn off.
Figure 5 The interlock circuitry internal to the laser head (right) applies a 5 VDC bias across the ring and
center pin of the phono-type plug (left). An external circuit that shorts the ring and center pin enables
Page 6
Specification
Must be Normally Open Dry Contacts,
Apply no External Voltages to the Interlock Input
2.5 mm Mono Phono Jack
5 VDC
(Center Pin is at 5 VDC, Ring is Ground)
the laser.
Chapter 4: Operation
TTN311232-D02