THORLABS LD1100 User manual

LD1100, EK1101, EK1102
Constant Power Laser Driver
User Guide

LD1100
Page 1 Rev M, November 13, 2014
Table of Contents
Chapter 1 Warning Symbol Definitions........................................................ 2
Chapter 2 Safety............................................................................................. 3
Chapter 3 Description.................................................................................... 4
Chapter 4 Setup.............................................................................................. 6
4.1. Setting the LD1100 Feedback Gain for a Given Monitor Photocurrent ......... 6
4.2. DC Power Supply Connection ......................................................................... 8
4.3. Laser Diode Connection................................................................................... 8
4.3.1. Laser Anode –Photodiode Cathode Common...................................... 8
4.3.2. Laser Cathode –Photodiode Cathode Common................................... 8
4.3.3. Four Pin Laser Diodes.......................................................................... 9
4.4. Accessories ...................................................................................................... 9
Chapter 5 Operation..................................................................................... 10
5.1. Laser Output Adjust........................................................................................10
5.2. ON / OFF Control .............................................................................................10
5.3. Monitoring the Laser Operating Current........................................................10
Chapter 6 Feedback Circuit Operation....................................................... 11
Chapter 7 EB1100 Evaluation Board, EK1101 & EK1102 Evaluation Kits 13
7.1. Initial Setup......................................................................................................13
7.2. DC Power Supply Connections ......................................................................14
7.3. Power Switch Connection...............................................................................14
7.4. Laser Diode Connections................................................................................14
7.4.1. EK1101: Laser Anode –Photodiode Cathode Common.......................15
7.4.2. EK1102: Laser Cathode –Photodiode Cathode Common....................15
7.5. Setting the EK1101/EK1102 Feedback Gain for a Given Monitor Current....15
7.6. Customizing the Feedback Gain.....................................................................15
7.7. EK1101 and EK1102 Operation.......................................................................16
7.8. Monitoring the Laser Operating Current........................................................17
7.9. Troubleshooting the EK1101 and EK1102......................................................17
Chapter 8 Troubleshooting.......................................................................... 18
8.1. Laser Output Too Low.....................................................................................18
8.2. Laser Output Control Too Sensitive...............................................................18
Chapter 9 Specifications.............................................................................. 19
Chapter 10 Regulatory................................................................................... 21
Chapter 11 Thorlabs Worldwide Contacts ................................................... 22

LD1100 Chapter 1: Warning Symbol Definitions
Page 2
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

LD1100
Page 3 Rev M, November 13, 2014
Chapter 2 Safety
The LD1100 has been designed to provide many hours of trouble-free
performance. To ensure proper operation, be sure follow these instructions:
CAUTION
A grounded wrist strap should always be worn when handling laser diodes to
prevent electrostatic damage to the laser.
CAUTION
When installing the LD1100, sound, high-quality solder joints must be used. A
cold solder joint or blobs of solder may cause intermittent connections or
shorts that can damage the laser and the driver.
CAUTION
When setting the laser output levels and the gain of the LD1100, be sure to
use the actual performance for the diode you have in hand. Many
manufacturers’ data sheets and brochures specify typical and maximum
values and are meant to only be used as a guideline.
Where provided, use the actual performance data supplied with the diode.
This is usually found on the outside of the diode wrapper or provided on a
separate data sheet. If in doubt, please call a Thorlabs engineer and we will be
happy to assist you.

LD1100 Chapter 3: Description
Page 4
Chapter 3 Description
The LD1100 is a constant-power laser driver module. Its features include an on-
board 12-turn trim pot for continuous laser output adjustment, pin-programmable
feedback gain, ON/OFF control input, and a current monitor output for observing
the laser drive current. Measuring only 1x 1.5, the LD1100 is a compact
module which can be embedded into a custom design. All input and output
signals are provided on a 12-pin SIP connector which allows simple integration
into a printed circuit design.
The LD1100 can drive lasers up to 250 mA in a constant-power mode. It uses the
internal monitor photodiode for a feedback signal into a proportional-integral
feedback loop to stabilize the output power to within 0.01%. To accommodate a
wide range of laser diodes, the feedback gain can be set by jumpering any
combination of the 5 gain setting resistor pins to the power supply common. This
allows lasers with monitor currents over a range from 5 µA to 5 mA to be used
with a single driver.
The LD1100 supports the following two laser pin configurations:
Figure 1 Laser Packages Supported
LD
PD
LD
PD

LD1100
Page 5 Rev M, November 13, 2014
Figure 2 LD1100 Pinouts
Pin
Signal
Description
1
+V
Circuit Power, 8 to 12VDC, 250mA, NOTE: Internally tied to Laser
Diode Anode, the laser anode must be isolated from the power supply
COM.
2
COM
Circuit ground
3
VREF
Internal 2.5 V reference
4
PDA
Photodiode Anode
5
LDA
Laser Diode Anode [internally tied to +V (pin 1)]
6
LDC
Laser Diode Cathode
7
RA
When tied to common puts a 100 kin parallel with 249 kinternal gain
res.
8
RB
When tied to common puts a 33.2 kin parallel with 249 kinternal
gain res.
9
RC
When tied to common puts a 10 kin parallel with 249 kinternal gain
res.
10
RD
When tied to common puts a 3.32 kin parallel with 249 kinternal
gain res.
11
RE
When tied to common puts a 1 kin parallel with 249 kinternal gain
res.
12
ILD
Laser Diode Current Monitor (10 mV/mA)

LD1100 Chapter 4: Setup
Page 6
Chapter 4 Setup
WARNING
Laser Diodes are extremely static sensitive and can be easily damaged by
mishandling. Always use a grounded wrist strap and work on an anti-static
mat when handling lasers.
4.1. Setting the LD1100 Feedback Gain for a Given Monitor
Photocurrent
The LD1100 has a pin-programmable feedback gain to accommodate a wide
range of laser monitor photodiode currents. It is important that this gain be
matched to the specific laser so that the LD1100 operates properly. Please refer
to Figure 1 for identifying LD1100 features. For a detailed description of the
feedback circuit as well as instructions on fully optimizing the gain, refer to
Appendix.
1. Determine the monitor photodiode feedback current for your laser. This
is usually given in the laser manufacturer‟s data sheet.
2. Using Figure 3, look up the resistor combination that matches the
photodiode current. If an exact match is not found, select the
combination that yields the next hightest feedback current.
3. Read across Figure 3 to identify the gain resistors that need to be
enabled. The resistors that have an “ON” in their respective column
need to be enabled by connecting their pin to the power supply common
(J1 pin 2). The resistors that are labeled “OFF” should not be connected
to any other pin.
Example:
Laser is a CQL806/D (Iop = 70 mA, Imon = 400 µA). Looking up Table1, the
closest monitor current to that is 770 µA which is set by jumpering RD to the
power supply common and leaving RA-RC, & RE open.
In this example, the maximum feedback current of 770 µA occurs when the
output adjust pot is turned up to the full 12 turns. However, this particular laser
reaches a maximum output at 400 µA which occurs at an output adjust pot
setting proportionately lower then 12 turns (400 µA / 770 µA * 12 turns = 6¼
turns). If you turn the output adjust above this point you will overdrive the laser
and cause pre-mature laser failure.
WARNING
When using the on-board gain settings, it is possible to overdrive the laser if
the output adjust pot is turned completely up. This may be avoided by
precisely matching the gain to your laser (see Chapter 6 for more details).

LD1100
Page 7 Rev M, November 13, 2014
Max Imon
(mA)
RA
100 k
RB
33 k
RC
10 k
RD
3.3 k
RE
1 k
0.010
OFF
OFF
OFF
OFF
OFF
0.035
ON
OFF
OFF
OFF
OFF
0.085
OFF
ON
OFF
OFF
OFF
0.110
ON
ON
OFF
OFF
OFF
0.260
OFF
OFF
ON
OFF
OFF
0.285
ON
OFF
ON
OFF
OFF
0.335
OFF
ON
ON
OFF
OFF
0.360
ON
ON
ON
OFF
OFF
0.767
OFF
OFF
OFF
ON
OFF
0.792
ON
OFF
OFF
ON
OFF
0.843
OFF
ON
OFF
ON
OFF
0.868
ON
ON
OFF
ON
OFF
1.017
OFF
OFF
ON
ON
OFF
1.042
ON
OFF
ON
ON
OFF
1.093
OFF
ON
ON
ON
OFF
1.118
ON
ON
ON
ON
OFF
2.510
OFF
OFF
OFF
OFF
ON
2.535
ON
OFF
OFF
OFF
ON
2.585
OFF
ON
OFF
OFF
ON
2.610
ON
ON
OFF
OFF
ON
2.760
OFF
OFF
ON
OFF
ON
2.785
ON
OFF
ON
OFF
ON
2.835
OFF
ON
ON
OFF
ON
2.860
ON
ON
ON
OFF
ON
3.267
OFF
OFF
OFF
ON
ON
3.292
ON
OFF
OFF
ON
ON
3.343
OFF
ON
OFF
ON
ON
3.368
ON
ON
OFF
ON
ON
3.517
OFF
OFF
ON
ON
ON
3.542
ON
OFF
ON
ON
ON
3.593
OFF
ON
ON
ON
ON
3.62
ON
ON
ON
ON
ON
Figure 3 Feedback Gain Resistor Settings

LD1100 Chapter 4: Setup
Page 8
4.2. DC Power Supply Connection
A high-quality DC power supply with good turn-on and turn-off transient
suppression will offer the best performance and protection for your laser. Avoid
using switching supplies which typically have higher transient noise that can
couple into the laser output as well as unregulated DC supplies. The LD1100 can
also be operated off a battery. The usable lifetime of the battery will be limited to
the laser operating current and the battery capacity.
Connect the „+‟ terminal of the power supply to J1 pin 1. Connect the power
supply common to J1 pin 2.
Note: The output compliance voltage is determined by the power supply voltage
and the laser operating voltage and current and can be determined as follows:
   󰇛 󰇜
Where: VCC is thepower supply voltage, VFis the laser forward voltage, and ILD
is the laser operating current.
4.3. Laser Diode Connection
The LD1100 supports four laser pin configurations (see Figure 2). We
recommend using 24 AWG wire from the LD1100 output pins to the laser and
keeping the overall wire length to a minimum (1 m max.). Twist the three leads
from the driver to the laser to minimize pick-up. If a socket is to be used for the
laser, make sure it is a high-quality socket with high-retention force pin sockets
(i.e. Thorlabs P/N S8060 (9 mm lasers) or S7060 (5.6 mm lasers).
4.3.1. Laser Anode –Photodiode Cathode Common
This configuration is used for most visible laser diodes.
Laser Pin
J1 Pin
PDA
4
LDA / PDC
5
LDC
6
4.3.2. Laser Cathode –Photodiode Cathode Common
This configuration is used for near IR laser diodes.
Laser Pin
J1 Pin
PDA
4
LDA
5
LDC / PDC
6

LD1100
Page 9 Rev M, November 13, 2014
4.3.3. Four Pin Laser Diodes
Four pin laser diodes may be connected to match one of the configurations in
4.3.1 or 4.3.2.
4.4. Accessories
Thorlabs offers evaluation boards as well as pre-assembled kits for the LD1100
to make set up and testing even easier. Please refer to Chapter 7 for setup and
operation of the EB1100, EK1101, EK1102.

LD1100 Chapter 5: Operation
Page 10
Chapter 5 Operation
5.1. Laser Output Adjust
After following the setup procedure in Section 4, the LD1100 should be ready to
start driving your laser. Please read and use the following steps to operate the
laser:
1. Before turning the laser on for the first time, turn the output adjustment
pot down to the minimum setting by turning the adjustment screw
counter-clockwise 12 full turns (this control does not have a mechanical
stop but by turning it 12 turns assures the pot is at its minimum value).
2. Turn the DC power supply on, at this point you may see a very slight
emission from the laser (particularly for lasers with low monitor currents)
but it should be well below the lasing threshold.
3. Slowly turn the output adjustment pot clockwise until the output starts to
increase. Use a calibrated power meter to precisely set the optical
output power. Once the output adjustment has been set, it should not
need any further adjustment unless you wish to change the output
power.
5.2. ON / OFF Control
The LD1100 has an external ON / OFF control (J1, pin 3) which allows the laser
output to be set to a reduced level. This function is activated by pulling this pin to
0V using either a mechanical switch or a transistor (open-drain FET or open-
collector bipolar). This pin is internally pulled up to VCC through a 2 K resistor
and must be allowed to float when the laser is operating. The normal voltage on
this pin with the laser operating is 2.5 V.
5.3. Monitoring the Laser Operating Current
The laser operating current can be monitored by measuring the voltage on J1 pin
12. This pin has an output of 10 mV/mA (i.e. J1-12 = 550 mV, laser is operating
at 55 mA). Use only a high input impedance device (greater than 1 K) to avoid
excessive load of the LD1100 output circuit.

LD1100
Page 11 Rev M, November 13, 2014
Chapter 6 Feedback Circuit Operation
The LD1100 uses a proportional-integral type (PI) feedback circuit to maintain an
extremely stable laser output. The laser power is stabilized by varying the laser
drive current in response to the monitor photodiode feedback to maintain a
constant output power. This compensates for changes in the laser efficiency due
to thermal and aging effects.
The feedback circuit converts the monitor photodiode current to a voltage which
is compared to an adjustable internal reference to generate the control signal for
the laser drive current. A decrease in the photodiode current is sensed as a
reduction in the output power and the feedback loop will try to compensate by
increasing the drive current to the laser. Likewise, if the photodiode current
increases, the feedback loop will reduce the laser drive current to maintain a
constant output power.
The LD1100 uses an adjustable 2.5V reference to establish the laser output
power. The monitor photodiode current is converted to a voltage through a bank
of programmable parallel resistors (see Figure 4) and compared to the internal
reference. The programmable resistor bank support a wide range of laser
monitor currents. It is important to select the right combination of resistors for
proper operation. Ideally, the effective resistance of the parallel combination of
resistors should be:
Reff = 2.5V / IMON
Where IMON is the monitor photodiode current.
Figure 4 Feedback Loop Functional Diagram

LD1100 Chapter 6: Feedback Circuit Operation
Page 12
The effective resistance is easily calculated by:
  
󰇡
            󰇢
Use only resistor values that are jumpered to the supply common in the equation
above.
Since it is not possible to match every possible monitor current with the 5
available resistors, a compromise must be made. Figure 3 in Chapter 4 provides
a convenient list of all 32 possible resistor combinations. Note that with all five
resistors open, the LD1100 still has a 249 K resistor (R6) in the feedback loop.
This was set so that the feedback loop will safely saturate before the laser is
overdriven for most lasers (assuming the output control is turned down before
powering up).
For critical applications, it is possible to set the feedback gain precisely with an
external resistance tied to one of the gain setting pins. For these cases, add the
external resistance to the resistance of the pin used.

LD1100
Page 13 Rev M, November 13, 2014
Chapter 7 EB1100 Evaluation Board, EK1101 &
EK1102 Evaluation Kits
Thorlabs offers two options to make setup and operation of the LD1100 Laser
Driver easier. The EB1100 is an evaluation printed circuit board that the user can
install the LD1100 onto and connect to the laser and power supply using
components supplied by the user. The EB1100 requires some assembly and
wiring prior to using the LD1100.
The EK1101 and EK1102 are complete evaluation kits which include the LD1100
Laser Driver, the EB1100 Evaluation Board, a 6-position DIP switch for selecting
the photo diode feedback gain, a 9V transistor battery connector for the power
source, and miscellaneous components. In addition, the EK1101 and EK1102
come pre-assembled. The EK1101 is configured for the Laser Anode - Photo
Diode Cathode Common package, where as the EK1102 is configured for the
Laser Cathode - Photo Diode Cathode Common package.
7.1. Initial Setup
The EK1101 and EK1102 come pre-assembled. There is only one connection
that needs to be made to begin operating these units; the DC input power. This
will be described in the next sections.
The EB1100 consists of only the evaluation printed circuit board. The LD1100 is
purchased separately. Also, the user must provide any needed components and
the required assembly of the PCB.
WARNING
As with all quality electronic equipment, the LD1100 requires high-quality
soldered connections to the printed circuit board and the accompanying
wiring harnesses. A poor solder joint on the LD1100 connection to the
EB1100 or in any of the wiring harnesses or components can result in an
intermittent connection that will lead to permanent damage to the laser.
Thorlabs does not warrant against any losses caused by poor soldering
practices. Be sure to check the quality of all solder joints before turning on
the LD1100 power source.

LD1100 Chapter 7: EB1100 Evaluation Board, EK1101 & EK1102 Evaluation Kits
Page 14
7.2. DC Power Supply Connections
A high quality DC power supply with good turn-on and turn-off transient
suppression will offer the best performance and protection for your laser. Avoid
using switching power supplies which typically have higher transient noise as
well as unregulated power supplies. The EK1101 and EK1102 can also be
operated off a battery. The useable lifetime of the battery will be limited to the
laser operating current and the battery capacity.
The EK1101 and EK1102 kits provide a 9V battery connector to supply
power to the circuit. Connect the red (+) wire to the pin labeled “+V” and
connect the black (-) wire to the pin labeled “COM”.
If a DC power supply is preferred, connect the positive lead to the pin
labeled “+V” and the negative lead (power supply return) to the pin
labeled “COM”. Adjust the DC power supply to a voltage between +8
and +12 volts before connecting to the evaluation board to prevent any
damage to the circuit.
7.3. Power Switch Connection
The EK1101 and EK1102 each have a slide switch that switches the power to the
LD1100. Before turning on the power to the laser, make sure that the feedback
gain settings are correct and the adjustment potentiometer on the LD1100 is
turned to its lowest setting (12 turns counter clockwise).
EB1100 Users: the ON / OFF position on the EB1100 can be used with a single
pole, single throw switch. Power to the LD1100 is provided when pin 1 of this
connector is jumpered to pin 2.
7.4. Laser Diode Connections
The EK1101 and EK1102 kits are provided with a laser diode socket assembly to
connect the laser diode to the circuit. The wiring diagram for the socket assembly
is shown in figure 2. The EK1100 series supports two laser pin configurations.
Figure 5 Laser Socket Wiring Harness

LD1100
Page 15 Rev M, November 13, 2014
7.4.1. EK1101: Laser Anode –Photodiode Cathode Common
This configuration is used for most visible laser diodes.
Laser Pin
J1 Pin (on EB100)
Wire Color
PDA
PD_A
Green
LDA / PDC
LD_A
Red
LDC
LD_C
Yellow
7.4.2. EK1102: Laser Cathode –Photodiode Cathode Common
This configuration is used for many near IR laser diodes.
Laser Pin
J1 Pin (on EB100)
Wire Color
PDA
PD_A
Green
LDA
LD_A
Yellow
LDC / PDC
LD_C
Red
WARNING
The LD1100 places the laser anode and cathode at a voltage above gorund.
The laser mount should be electrically isolated form the power supply used to
operate the EB1100. For best results use a floating power supply that has
outputs isolated from the AC ground to run the EB1100 and connect the laser
mout to a suitable earth ground to improve ESD protection.
7.5. Setting the EK1101/EK1102 Feedback Gain for a Given
Monitor Current
The EK1101 and EK1102 have a dip switch programmable feedback gain to
accommodate a wide range of laser monitor photo diode currents. Please refer to
Chapter 4 (Setup) to determine the feedback gain. The gain can now be set by
turning on the proper dip switches.
For EB1100 users: the gain may be permanently selected by installing a jumper
in place of the switch positions that are designated in the ON position in Figure 3.
7.6. Customizing the Feedback Gain
For critical applications, it is possible to set the feedback gain precisely by
calculating an external resistance (REXT) and placing it on the evaluation board.
Note: REXT is added to the 1 kresistance of RE. The sum of RE and REXT is in
parallel with the internal 249 kresistor. Use the equation below to calculate the
required value of REXT.
LD
PD
LD
PD

LD1100 Chapter 7: EB1100 Evaluation Board, EK1101 & EK1102 Evaluation Kits
Page 16
To operate in this mode, all of the dip switches should be in the off
position.
  

   
Where: Reff is the desired feedback gain. Reff can be calculated from the
maximum photo diode monitor current for the laser as follows:
 

WARNING
When calculating the desired operating points of laser diodes, it is important
that you use the actual performance data for the diode you have in hand.
Many manufacturer’s data sheets and brochures specify typical and
maximum values and are meant to only be used as a guideline.
Where provided, use the actual performance data supplied with the diode.
This is usually found on the outside of the diode wrapper or provided on a
separate data sheet. If in doubt, please call a Thorlabs engineer and we will be
happy to assist you.
7.7. EK1101 and EK1102 Operation
The EK1101 or EK1102 must first be set up properly. Please refer to the
preceding sections and follow each step completely before attempting to operate
a laser.
1. Attach the laser socket to the laser diode. See the note on isolating the
laser mount.
2. Adjust the Power ADJ trim pot 12 turns counter-clockwise to set the
output power to the minimum level.
3. Verify the gain settings are correctly set for your laser.
4. Turn the power swithch on. At this point it is normal for some light to
emit from the diode but it should be well below the lasing threshold.
5. Using a calibrated power meter to monitor the laser output power,
slowly adjust the POWER ADJ trim pot to reach the desired operating
power of the laser. We recommend that the power meter surface be
tilted slightly (approximately 2 degrees) to avoid reflecting the laser light
directly back into the laser, which can lead to errors in setting the laser
power.

LD1100
Page 17 Rev M, November 13, 2014
7.8. Monitoring the Laser Operating Current
The laser operating current can be monitored by measuring the voltage on J1 pin
1 (ILD) of the evaluation board. This pin has an output of 10 mV/mA.
7.9. Troubleshooting the EK1101 and EK1102
The EK1101 and EK1102 are fairly simple device to set up and operate and
should provide many hours of trouble-free operation. Should you encounter any
problems with the EK1101 or EK1102 during operation we recommend checking
the following:
1. Check that the gain settings match the monitor photo diode current of
your laser. Be sure to use the actual performance data for your specific
laser.
2. Check that the laser socket pin connections match the pinouts of your
laser.
3. Check that all solder joints are clean and of high quality. Cold solder
joints or blobs of solder can cause shorts and intermittent connections.
4. Check that the power supply voltage is between 8 and 12 V. If using a
battery, replace with a new battery.
5. Check that the power switch is ON.
If you still experience problems, please call Thorlabs and an engineer will be
happy to assist you.

LD1100 Chapter 8: Troubleshooting
Page 18
Chapter 8 Troubleshooting
Once it is set up, the LD1100 should be easy to operate and provide many hours
of use. In case you experience any problems, we‟ve included a few checks to
help in troubleshooting the problem. If you have any questions, please call the
factory and a Thorlabs engineer will be happy to assist you.
8.1. Laser Output Too Low
1. Check that the appropriate gain setting is used for your laser (refer to
Chapter 4).
2. Check the output adjust pot. Turning it clockwise should increase the
laser output power.
3. Make sure pin J1-3 is floating high and not pulled to ground.
4. Check that DC power supply (should be 8 to 12 VDC).
5. Check the laser for possible damage. A typical healthy laser should
have a homogeneous elliptical output beam whereas a damaged laser
usually has low output power, a diffused output beam, and sometimes
dark striations through the main lobe.
8.2. Laser Output Control Too Sensitive
1. Check that the appropriate gain setting is used for your laser (refer to
Chapter 4).

LD1100
Page 19 Rev M, November 13, 2014
Chapter 9 Specifications
Performance Specifications
Operating Mode
Constant-Power (Photodiode Feedback)
Output Current
0 –250 mA
Output Control
12-Turn Potentiometer (On-Board)
Output Stability
<0.01%
Output Noise
0.1 µA (RMS)
Feedback Gain
On-Board, Pin-Programmable, Also Externally Configurable
Monitor Current Range
5 µA –5 mA
Operating Voltage
8 to 12 VDC
Quiescent Current
9 mA
Dimensions
1x 1.5, 12 Pin SIP Package
ESD Protection
100 ms Slow Start