THORLABS LDM21, User Manual

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LDM21 Chapter 3: Setup
Page 5 Rev K, September 11, 2018
3.2. 5.6 mm Adapter
By default, the LDM21 is designed to be used with standard 9 mm laser diode
packages. The mount can be used with a standard 5.6 mm using the included
adapter, which can be found in the small brown envelope marked “Accessories”
on the outside. Included in this envelope is the 9 mm mounting plate and the
imperial to metric mounting adapter.
3.3. 4-Pin Laser Diodes
The LDM21 also supports 4-pin laser diodes. Insert the laser into the 4-pin
socket and note which laser pin is in the 3 o’clock position (laser anode or
cathode). Also note which photodiode pin is in the 9 o’clock position (anode or
cathode). The mount will tie the laser and photodiode pins located at 12 o’clock
and 6 o’clock together and also to ground. By noting which polarity pins are
inserted into the socket, you can convert the 4-pin layout to one of the 3-pin
layouts in Figure 2 on page 3 above. Set the LD and PD polarity switches
accordingly.
3.4. Laser Controller Connections
Using the Thorlabs LDC/ITC Series Laser Controllers:

The LDM21 is compatible with all Thorlabs LDC LD controllers and ITC
series combination controllers (LD and TEC). Appropriate cables with
DB9 connectors are included with Thorlabs controllers and ensure that
the controllers cannot be connected incorrectly. Additionally, these
controllers have built-in protection circuitry that protects the laser when
not in use.

The nomenclature for the Laser Diode polarity switch on the LDC/ITC
driver and the LDM21 are consistent with each other. For example, if
the laser polarity on the dirver is set to “AG” (anode grounded), then the
LD polarity switch on the LDM21 should also be set to AG, and so forth.

The nomenclature for the Photo Diode polarity switch on the
LDC40xx/80xx and ITC series drivers and the LDM21 is as follows: The
photodiode polarity switch on the LDM21 must always be set to “CG”.
The photodiode polarity should be set with the internal Laser controller
switch only. For more information on how to set Polarity settings on the
Laser controller, please refer to the appropriate Laser Controller
manual.
Using a third-party laser controller:

When using a third-party controller, a custom cable will have to be made
to properly interface to the laser mount. Please refer to the table on the
next page for laser connections: