THORLABS LDM21 User manual

LDM21
5.6 mm/9 mm
Laser Diode Mount
User Guide

Table of Contents
Chapter 1Warning Symbol Definitions ........................................... 1
Chapter 2Description ........................................................................ 2
Chapter 3Setup .................................................................................. 3
3.1.LaserInstallation...........................................................3
3.2.5.6mmAdapter.............................................................5
3.3.4‐PinLaserDiodes.........................................................5
3.4.LaserControllerConnections..........................................5
3.5.TECControllerConnections............................................6
3.6.ThermistorData............................................................7
3.7.MountingOtherAccessories..........................................9
Chapter 4Operation ......................................................................... 10
4.1.SafeOperatingArea....................................................10
4.2.MaintainingtheLDM21...............................................11
Chapter 5Troubleshooting ............................................................. 12
Chapter 6Specifications ................................................................. 13
Chapter 7Mechanical Drawing ....................................................... 14
Chapter 8Regulatory ....................................................................... 15
8.1.WasteTreatmentisYourOwnResponsibility...............15
8.2.EcologicalBackground.................................................15
Chapter 9Thorlabs Worldwide Contacts....................................... 16

LDM21 Chapter 1: Warning Symbol Definitions
Page 1 Rev K, September 11, 2018
Chapter 1 Warning Symbol Definitions
Below is a list of warning symbols you may encounter in this manual or on your
device.
Symbol Description
Direct Current
Alternating Current
Both Direct and Alternating Current
Earth Ground Terminal
Protective Conductor Terminal
Frame or Chassis Terminal
Equipotentiality
On (Supply)
Off (Supply)
In Position of a Bi-Stable Push Control
Out Position of a Bi-Stable Push Control
Caution: Risk of Electric Shock
Caution: Hot Surface
Caution: Risk of Danger
Warning: Laser Radiation
Caution: Spinning Blades May Cause Harm

LDM21 Chapter 2: Description
TTN013394-D02 Page 2
Chapter 2 Description
The LDM21 is a temperature-controlled laser diode mount. When used with
Thorlabs LDC Series Laser Controllers and TED Series TEC Controllers, a laser
diode can be operated with precise temperature control for wavelength and
power stability. A four pin socket accepts all 9mm and 5.6mm laser diodes. Easy
to use polarity switches allow the laser mount to be configured for all possible
laser pin assignments.
The LDM21 was designed with features that allow it to be easily incorporated into
complex systems. The front of the LDM21 has a 1.035"-40 thread to accept a
wide variety of Thorlabs SM1 1.0" optics mounts and accessories. Also standard
with the mount are 4-40 tapped holes on 30 mm centers for mounting any
number of Thorlabs cage assembly products. There is also a #8-32 tapped hole
on the bottom surface to allow the unit to be post mounted.
The LDM21 uses a thermo-electric cooler (TEC) to precisely regulate the
operating temperature of a laser diode. Temperature sensing is accomplished
using an integrated thermistor and AD592 solid state temperature sensor. The
Thorlabs TED200 supports these sensors.
NOTE: The LDM21 is intended for laser diodes requiring low input power and
operating across a limited temperature range. Its primary function is to maintain
the laser diode case temperature at a constant temperature ideally at 25 °C in a
typical laboratory ambient environment (20 to 30 °C). Please refer to the Safe
Operating Area chart in this manual to ensure that the LDM21 is used within its
capabilities.
Figure 1 Inside View of LDM21 and Included Components

LDM21 Chapter 3: Setup
Page 3 Rev K, September 11, 2018
Chapter 3 Setup
3.1. Laser Installation
1. Unpack the laser mount and remove the four 2-56 socket-head screws
from the front cover using a 5/64" hex driver (provided).
2. Remove the two Phillips head 2-56 screws from the laser-mounting
flange and remove the flange.
3. Determine the laser pin configuration from the laser diode
manufacturer’s data sheets and set the LD (Laser Diode) and PD
(Photodiode) switches located on the inside of the unit according to
Figure 2.
Figure 2 Polarity Switch Settings
LD
Style A
Style B
Style C
Style D
AG CG
PD
CG AG
LD
AG CG
PD
CG AG
LD
AG CG
PD
CG AG
LD
AG CG
PD
CG AG
Case
LD PD
LD PD
LD PD
LD PD
Case
Case
Case

LDM21 Chapter 3: Setup
TTN013394-D02 Page 4
1. The four sockets comprising the laser diode connector are through-hole
type sockets with a blind clearance of 0.48” measured from the front
face of the copper cold plate. It is not necessary to trim the laser diode
leads prior to mounting into this connector unless they are longer than
0.48”.
2. The laser connector is located close enough to the front face of the
copper cold plate to allow easy installation of short-leaded lasers. The
clearance area around the LD and PD sockets is sufficient to prevent
the pins from contacting the cold plate.
3. Most laser diodes are three pins with the case tied to one of the laser
pins and also to one of the photodiode pins. The other laser and
photodiode pins will be isolated from the case. The LDM21 was
designed to operate the laser case at ground potential, therefore this
common pin will be inserted into either the 12 o’clock or the 6 o’clock
position of the laser connector. Locate the isolated laser pin and insert it
in the 3 o’clock position. The isolated photodiode should now be in the 9
o’clock position. Refer to Fig. 3. (Orient the mount with the PD polarity
switch above the LD socket).
4. The LDM21 Mount is also compatible with style E and style H laser
diodes, which do not have a photodiode; they have only a laser diode
and a ground pin. They can therefore be set up the same as style A (LD
Anode Ground) or style B (LD Cathode Ground) respectively.
5. Replace the laser mounting flange and the cover. Install both screws
through the mounting flange and loosely into the mount. Carefully
tighten each screw a little bit at a time until the flange is just snug. Do
not over-tighten either screw- the flange should sit slightly above the
cold plate. Reinstall the cover using the four 2-56 cap head screws
provided.
Figure 3 LD and PD Orientation
G
G
LDPD

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:

LDM21 Chapter 3: Setup
TTN013394-D02 Page 6
Pin Signal Description
1 Interlock
(LDC Specific)
This pin is the input to the Interlock Circuits. When using
Thorlabs LDCs, no external circuitry is required.
2 Photodiode
Cathode
This pin is connected to the 9 o’clock pin on the laser
socket when the PD Polarity Switch is set to AG (Anode
Grounded). It is attached to ground and the 12 o’clock and
6 o’clock pins on the laser socket when the PD Polarity
Switch is set to CG (Cathode Grounded).
3 Laser Ground
(Case)
This pin is connected to the 12 o’clock and 6 o’clock pins
on the laser socket and corresponds to the settings of the
LD and PD polarity switches. i.e., if the LD and PD
switches are set to AG, then this pin grounds the Anodes
of the laser and photo diode.
4 Photodiode
Anode
This pin is connected to the 9 o’clock pin on the laser
socket with the PD Polarity Switch is set to CG (Cathode
Grounded). It is attached to ground and the 12 o’clock and
6 o’clock pins on the laser socket when the PD Polarity
Switch is set to AG (Anode Grounded).
5 Interlock Return This pin is the return side of the Interlock circuitry. Pin 1
and 5 are shorted internally in the LDM21.
6 N/A
7 Laser Diode
Cathode
This pin is connected to the 3 o’clock pin on the laser
socket when the LD Polarity Switch is set to AG (Anode
Grounded). Otherwise, it is floating.
8 Laser Diode
Anode
This pin is connected to the 3 o’clock pin on the laser
socket when the LD Polarity Switch is set to CG (Cathode
Grounded). Otherwise it is floating.
9 N/A
3.5. TEC Controller Connections
Using the Thorlabs TED Series TEC Controllers:
 The LDM21 is best used with Thorlabs TED200 or related TEC
Controllers. The TED series are shipped with a mating DB9 cable that
plugs directly into the controller and laser mount. Using the cable
supplied with the TED, the controller cannot be connected incorrectly.
Simply connect the cable included with the TED to the Laser Mount and
to the controller.
Using a third-party TEC 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 to the
right for laser connections.

LDM21 Chapter 3: Setup
Page 7 Rev K, September 11, 2018
TEC Connector Pin Function
3.6. Thermistor Data
Figure 4 Thermistor Curve and Data
Pin Signal Description
1 N/A
2 +Thermistor The 10 kΩ @ 25 °C NTC thermistor (provided for
temperature feedback).
3 -Thermistor The thermistor return pin
4 +TEC This pin is connected to the positive terminal of the TEC
element.
5 -TEC (-) This pin is connected to the negativeterminal of the TEC
element.
6 N/A
7 AD592 (-)
The negative terminal of the AD592 temperature
transducer. When using Thorlabs TEDs, no external
circuitry is required. To use this device with third party
controllers, it must be properly biased. Refer to Analog
Devices AD592 Data for applications information.
8 N/A
9 AD592 (+) The positive terminal of the AD592

LDM21 Chapter 3: Setup
TTN013394-D02 Page 8
Theoretical Resistance Values
The relationship between resistance and temperature can also be calculated
using the following equations:
Where A, B, C, D, A
1,
B
1,
C
1,
and D
1
are constant values that depend on the
material; see table below for values. R
ref
is the resistance value at a reference
temperature, which is room temperature in this case. T is the temperature in K.
Constants Value Unit
A -14.6337 -
B 4791.842 K
C -115334 K2
D
3.730535E+06
K3
A1
3.354016E-03
-
B1
2.569850E-04
K-1
C1
2.620131E-06
K-2
D1
6.383091E-08
K-3
T0
298.15
K
Rref
10000
Ω
Resistance (Ω) °C
15895 15
15153 16
14451 17
13785 18
13155 19
12558 20
11991 21
11454 22
10944 23
10460 24
10000 25
Resistance (Ω) °C
9563 26
9149 27
8755 28
8380 29
8023 30
7684 31
7362 32
7055 33
6762 34
6484 35

LDM21 Chapter 3: Setup
Page 9 Rev K, September 11, 2018
3.7. Mounting Other Accessories
The LDM21 includes a SM1 threaded hole centered on the laser for mounting
Thorlabs SM1-series optics mounts. This is most often used for mounting
aspheric collimating optics available separately from Thorlabs.
Also included are four 4-40 tapped holes mounted on 30 mm centers for
attaching our cage assembly products. Using the combination of the SM1
threaded mount and the cage assemblies’ products, a wide variety of optical
systems can be easily assembled from off-the-shelf products.

LDM21 Chapter 4: Operation
TTN013394-D02 Page 10
Chapter 4 Operation
 With the laser mounted and the laser and temperature controller
connected, the LDM21 is ready to operate. Please refer to the operating
instructions for the laser and temperature controller for specific
operating instructions.
 When operating at low temperatures in high humidity climates, the laser
mount may develop internal condensation. If this occurs, turn the laser
off, open the case, and allow the mount to dry off completely before re-
using.
 When using a collimiating optic in the 1" threaded mount, the lens may
be positioned slightly laterally by loosening the four 2-56 screws on the
cover and shifting the cover plate manually.
4.1. Safe Operating Area
The LDM21 is intended to be operated at a fixed temperature set-point of 25 °C
but can be operated as low as 20 °C as long as the input power to the laser
diode (input current x LD voltage) does not exceed the values specified in the
Safe Operating Area curve as a function of ambient temperature. It is not
recommended that the LDM21 be driven with more than 600 mW of input power,
set to a temperature below 20 °C, or operated in an ambient temperature above
35 °C. Operating the LDM21 outside of the safe operating area will result in
thermal runaway of the cooling system which will damage the laser diode
mounted in the unit.
Additionally, the 2 W maximum cooling capacity includes the power dissipated by
the TEC element in addition to the input power of the laser diode. Careful
monitoring of the TEC power (TEC Current x TEC Voltage) along with the
parameters of the SOA curve will further ensure that the system is operating
within its capabilities.

LDM21 Chapter 4: Operation
Page 11 Rev K, September 11, 2018
4.2. Maintaining the LDM21
There are no serviceable parts in the LDM21. The housing may be cleaned by
wiping with a soft damp cloth. If you suspect a problem with your LDM21, please
call Thorlabs Technical Support, and an engineer will be happy to assist you.
0
100
200
300
400
500
600
700
20 22 24 26 28 30 32 34 36 38 40
LD Input Power (mW)
Ambient Temperature (°C)
LDM21 Safe Operating Conditions
25 °C Set Point
20 °C Set Point
Safe Operating Area

LDM21 Chapter 5: Troubleshooting
TTN013394-D02 Page 12
Chapter 5 Troubleshooting
1. Laser Driver will not enable.
 If you are using our laser and TEC controllers with our LDM21
mount, make sure that both cables are fully inserted into their DB9
connectors.
2. Laser wavelength or power is unstable even though the TEC controller
shows a stable temperature.
 Make sure that your laser diode is fully inserted into the LDM21
laser socket and that its body is in full contact with the copper cold
plate.
 Make sure that that the appropriate mounting flange is installed
over your laser. There are two different flanges; one specifically for
5.6 mm diodes and one for 9 mm diodes.
3. The LDC series laser driver indicates an “Open Circuit” alarm when I try
to enable the laser.
 The LD and PD polarity switch settings are incorrect. Refer to Fig. 1
and the data sheet for your specific laser diode to ensure the
proper settings. The LD polarity switch setting on your LDM21 must
also match the LD polarity switch on the rear panel of your LDC
series laser diode controller.
 The laser diode is installed into the wrong pins on the laser diode
socket. Refer to Fig. 2 (see page 5) for the correct orientation of the
laser diode pins and compare this to the data sheet for your laser
diode.
4. My laser diode does not have an integrated photodiode. How does it get
installed, and how do the polarity switches get set?
 If your laser diode has one of its two active leads common to the
case of the laser, that lead must be connected to one of the “G”
sockets on the laser diode connector (refer to Fig. 2, page 5) while
the other pin is connected to the “LD” socket in the 3 o’clock
position. Depending on the pin orientation of your laser, you might
be using either the “G” socket at 12 o’clock or the “G” socket at 6
o’clock. Refer to your laser diode data for pin orientation. If your
cathode pin is common to the body of your laser diode, set the LD
polarity switch to “CG”. If your Anode pin is common to the body of
your laser diode, set the LD polarity switch to “AG”. The setting for
the PD polarity switch is irrelevant.
If you still have problems or questions regarding the operation of your LDM21,
please contact Thorlabs Tech Support.

LDM21 Chapter 6: Specifications
Page 13 Rev K, September 11, 2018
Chapter 6 Specifications
1 See Safe Operating Area on page 11 for more information
Item # LDM21
General
Size 1.75" x 1.75" x 1.47"
Weight 3 oz
Accessory Mounting 1.035"-40 Thread for SM1 Series Optics Mounts
4-40 x 30 mm Tapped Holes for Cage Assembly Products
Miscellaneous 8-32 and M4 Threaded Mounting Holes
Laser Specifications
Lasers Supported 5.6 mm and 9 mm
Max Laser Current 500 mA1
Max Laser Input
Power 600 mW1
Laser Pin All LD Packages, Switch Selectable
Configurations Selectable
Laser Polarity Select Slide Switches
Laser Interface DB9 Female
TEC Specifications
Max TEC Current 2.5 A
Max TEC Voltage 1.8 V
TEC Heating/
Cooling Capacity 2 W
Typical Temperature Range (LD dependent)
Temp Sensor 1
Thermistor
10 KΩ ± 3%, NTC
Beta = 3977 K ± 0.75 %
Temp Sensor 2
Analog Devices AD592 1 µA/ K
TEC Interface DB9 Male

LDM21 Chapter 7: Mechanical Drawing
TTN013394-D02 Page 14
Chapter 7 Mechanical Drawing
Figure 5 Mechanical Drawing of the LDM21
1.75
1.75
0.88
0.88
30MM CAGE ASSEMBLY
MOUNTING HOLES
(#4-40) 4 PLACES
0.88
0.12
TEC CONNECTION
MALE DB9
1.66
0.88
0.12
LASER DIODE CONNECTION
FEMALE DB9
0.88
0.12
0.99
#8-32 MOUNTING HOLE
4 PLACES
SM1 (1.035-40)
SERIES THREAD

LDM21 Chapter 8: Regulatory
Page 15 Rev K, September 11, 2018
Chapter 8 Regulatory
As required by the WEEE (Waste Electrical and Electronic Equipment Directive)
of the European Community and the corresponding national laws, Thorlabs offers
all end users in the EC the possibility to return “end of life” units without incurring
disposal charges.
This offer is valid for Thorlabs electrical and electronic equipment:
Sold after August 13, 2005
Marked correspondingly with the crossed out
“wheelie bin” logo (see right)
Sold to a company or institute within the EC
Currently owned by a company or institute
within the EC
Still complete, not disassembled and not
contaminated
As the WEEE directive applies to self contained
operational electrical and electronic products, this end of
life take back service does not refer to other Thorlabs products, such as:
Pure OEM products, that means assemblies to be built into a unit by the
user (e.g. OEM laser driver cards)
Components
Mechanics and optics
Left over parts of units disassembled by the user (PCB’s, housings etc.).
If you wish to return a Thorlabs unit for waste recovery, please contact Thorlabs
or your nearest dealer for further information.
8.1. Waste Treatment is Your Own Responsibility
If you do not return an “end of life” unit to Thorlabs, you must hand it to a
company specialized in waste recovery. Do not dispose of the unit in a litter bin
or at a public waste disposal site.
8.2. Ecological Background
It is well known that WEEE pollutes the environment by releasing toxic products
during decomposition. The aim of the European RoHS directive is to reduce the
content of toxic substances in electronic products in the future.
The intent of the WEEE directive is to enforce the recycling of WEEE. A
controlled recycling of end of life products will thereby avoid negative impacts on
the environment.
Wheelie Bin Logo

LDM21 Chapter 9: Thorlabs Worldwide Contacts
TTN013394-D02 Page 16
Chapter 9Thorlabs Worldwide Contacts
For technical support or sales inquiries, please visit us at
www.thorlabs.com/contact for our most up-to-date contact information.
USA, Canada, and South America
Thorlabs, Inc.
sa[email protected]le
[email protected]
Europe
Thorlabs GmbH
[email protected]
France
Thorlabs SASSA
[email protected]
Japan
Thorlabs Japan, Inc.
[email protected]
UK and Ireland
Thorlabs Ltd.
[email protected]
[email protected]
Scandinavia
Thorlabs Sweden AB
[email protected]
Brazil
Thorlabs Vendas de Fotônicos Ltda.
[email protected]
China
Thorlabs China
[email protected]

www.thorlabs.com