THORLABS LDC340 User manual

Operation Manual
Thorlabs Blueline™ Series
Laser diode controller
LDC340 (-IEEE)
2006

Version: 2.23
Date: 20.06.2006
Copyright©2006, Thorlabs GmbH, Germany

Contents Page
1General Information 1
1.1 At a Glance 1
1.2 Safety 4
1.3 Ordering codes and Accessories 6
2Getting Started 7
2.1 Unpacking 7
2.2 Preparation 7
2.3 Operating elements 8
2.3.1 Front panel 8
2.3.2 Rear panel 9
2.4 First operation 10
3Operating the LDC340 11
3.1 Presettings 11
3.1.1 DIP switch for “wake up“ preset 11
3.1.2 Setting the limit of the laser current ILD LIM 13
3.1.3 Setting the limit of the monitor diode current IPD LIM 13
3.1.4 Adjusting the power display of an internal monitor diode 14
3.2 Connecting components 15
3.2.1 Pin assignment of the output jack 15
3.2.2 Using the interlock input 16
3.2.3 Connecting the monitor diode 17
3.2.4 Laser voltage measurement 18
3.2.5 Temperature window protection input (WIN IN) 19
3.3 Display 19
3.4 Main setting knob 20
3.5 Mode Select 20
3.6 Display select 21
3.7 Analog modulation input 21
3.8 Analog output 22
3.9 Setup of polarities and bias voltage 22
3.9.1 Polarity of the Laser diode (LD POL) 22
3.9.2 Polarity of the internal monitor diode (PD POL) 23
3.9.3 Bias voltage of the monitor diode (PD BIAS) 23
3.9.4 Adjusting the bias voltage of the monitor diode 24
3.10 Laser current ON/OFF (LD ON) 25
3.11 CP gain 26
4Communicating with a control computer (LDC340-IEEE) 27
4.1 General remarks 27

4.2 IEEE488 Interface 28
4.2.1 Interface specifications (IEEE 488 subsets) 28
4.2.2 Setting up the Interface 29
4.2.3 Connecting the Instrument 31
4.2.4 IEEE488 bus commands 32
4.3 Before Programming 34
4.3.1 Nomenclature 34
4.3.2 Program and response messages 34
4.3.3 Data format 35
4.4 Common commands and queries 36
4.4.1 Identification query 36
4.4.2 Reset 36
4.4.3 Self-test query 36
4.4.4 Set Operation-complete bit 36
4.4.5 Operation-complete query 37
4.4.6 Wait 37
4.4.7 Event-Status-Enable-Register (ESE) 37
4.4.8 Query Standard-Event-Status-Register (ESR) 37
4.4.9 Service-Request-Enable-Register (SRE) 38
4.4.10 Query Status-Byte-Register (STB) 38
4.5 System command group 39
4.5.1 Answer mode 39
4.5.2 Error-LED mode 39
4.5.3 Querying the error queue 40
4.5.4 Oversampling rate 40
4.6 Status command group 41
4.6.1 Query Device-Error-Condition-Register (DEC) 41
4.6.2 Query Device-Error-Event-Register (DEE) 41
4.6.3 Device-Error-Event-Enable-Register (EDE) 41
4.7 LDC340 specific commands 42
4.7.1 Operation mode (MODE) 42
4.7.2 Laser diode polarity (LDPOL) 42
4.7.3 Photo diode polarity (PDPOL) 43
4.7.4 Photo diode range (PDRANGE) 43
4.7.5 Switching the bias voltage on and off (PDBIA) 44
4.7.6 Switching the output on and off (LASER) 45
4.7.7 Reading the laser diode hardware limit (LIMCP) 45
4.7.8 Laser diode current (ILD) 46
4.7.9 Monitor diode current (IMD) 47

4.7.10 Calibrating a photo diode (CALPD) 48
4.7.11 Optical power (POPT) 49
4.7.12 Reading the optical power from the display (POPTP) 50
4.7.13 Reading the laser diode voltage (VLD) 50
4.7.14 Reading the bias voltage (VBIAS) 50
4.7.15 Reading the monitor diode limit current (LIMMP) 51
4.7.16 Reading the internal photo diode current (IPDI) 51
4.7.17 Reading the external photo diode current (IPDE) 51
4.8 Error messages of the LDC340-IEEE 52
4.8.1 General errors 52
4.8.2 LDC340 operation error messages 55
4.9 Status reporting 57
4.9.1 Standard event status register (ESR) 59
4.9.2 Standard event status enable register (ESE) 59
4.9.3 Status byte register (STB) 60
4.9.4 Service request enable register (SRE) 60
4.9.5 Reading the STB by detecting SRQ 61
4.9.6 Reading the STB by *STB? command 61
4.9.7 Reading the STB by serial poll 61
4.9.8 Device error condition register (DEC) 62
4.9.9 Device error event register (DEE) 63
4.9.10 Device error event enable register (EDE) 63
4.10 Hints for setting up control programs 64
5Maintenance and repair 67
5.1 Maintenance 67
5.2 Selecting the line voltage 68
5.3 Exchanging the line fuse 68
5.4 Exchange of internal fuses 70
5.5 Troubleshooting 71
6Appendix 73
6.1 Warranty 73
6.2 Certifications and compliances 74
6.3 Technical data 76
6.4 Thorlabs “End of Life” policy (WEEE) 79
6.4.1 Waste treatment on your own responsibility 79
6.4.2 Ecological background 80
6.5 List of acronyms 81
6.6 List of figures 82
6.7 Addresses 83

We aim to develop and produce the best solution for your application in the
field of optical measurement technique. To help us to come up to your
expectations and develop our products permanently we need your ideas and
suggestions. Therefore, please let us know about possible criticism or ideas.
We and our international partners are looking forward to hearing from you.
Thorlabs GmbH
This part of the instruction manual contains specific information on how to operate a
laser diode controller LDC340. A general description is followed by explanations of
how to operate the unit manually. You will also find the information about remote
control of the LDC340-IEEE via the IEEE 488 computer interface.
Attention
This manual contains “WARNINGS” and “ATTENTION” label in this
form, to indicate dangers for persons or possible damage of equip-
ment.
Please read these advises carefully!
NOTE
This manual also contains “NOTES” and “HINTS” written in this form.

1.1 At a Glance
LDC340 / Page 1
1 General Information
1.1 At a Glance
The LDC340 is a compact laser driver with optional IEEE488.2 interface for driving
laser diodes up to 4A laser current.
The LDC340 especially excels in:
•Very low noise
•Two current ranges
•The universal possibilities of connecting components
•The operating comfort of its compact construction
•Extensive protections for the laser diode
•The possibility to drive two lasers in series at the same time
•Two independent monitor diode inputs
•CW mode with modulation input up to 50 kHz
•Interlock for automatic switch-off by an external control signal (e.g. cooling loop
monitoring)
•LabVIEW®- and LabWindows/CVI®instrument drivers.
The laser diodes can be operated in constant current as well as in constant power
mode.
In remote operation (LDC340-IEEE only) all settings except the limits and 2
calibration values can be done from the PC.

1.1 At a Glance
LDC340 / Page 2
A wide variety of protection features protect the laser diode from damage.
These features are:
•Key-operated power switch
Prevents unauthorized switching on of the laser diode.
•Softstart
The switch on delay of the softstart function protects the laser diode against
undesired peaks.
•Limit for the injection current (hardware limit)
A manually adjustable current limit limits the maximum allowed laser current. The
limit value can be set with a 25-turn potentiometer on the front panel.
•Interlock
The interlock input enables to realize several protection functions simultaneously.
•Safety lock to prevent unintentional use
•Cable damage monitoring
•An external emergency switch may be connected
•Application of external automatic protection equipment, e.g. for the temperature of
cooling water
•ON/OFF LED of the laser diode
The laser can only be operated with the interlock input being closed.
(Refer to chapter 3.2.2, “Using the interlock input“ starting on page 16)
•Contact protection of the laser diode (open circuit)
If the line to the laser is interrupted even for a short time during operation an
emergency switch off is immediately released.
•Electronic short-circuit switch for the laser diode
With the current module switched off an electronic switch will shortcircuit the laser
diode so that no voltage is applied to the laser contacts.
•Control LED for laser current being active
When the laser current is switched on an LED in the switch LD ON lights up.

1.1 At a Glance
LDC340 / Page 3
•Temperature-window protection of the laser diode
Operation in the specified temperature range. (Only in combination with a Thorlabs
GmbH TED 350)
•Over-temperature protection
The LDC340 has an automatic over-temperature protection in case that the allowed
internal operating temperature should be exceeded. In this case the output will switch
off and after temperature decay of about 10 °C the output current of the LDC340 can
be switched on again.
•Defined states after switch-on
When switching on the LDC340 with the mains switch the laser current output is
always switched off. The LDC340 will always wake up in a mode that can be selected
with a DIP switch at the rear.
•Mains filter
Protection against line failure or transients.
•Line failure monitoring
In case of line failure/line interruption the LDC340 will wake up anew as if it has been
switched on. So the laser output remains switched off.

1.2 Safety
LDC340 / Page 4
1.2 Safety
Attention 
All statements regarding safety of operation and technical data in
this instruction manual will only apply when the unit is operated
correctly.
Before applying power to your LDC340 system, make sure that the
protective conductor of the 3 conductor mains power cord is cor-
rectly connected to the protective earth contact of the socket outlet!
Improper grounding can cause electric shock with damages to your
health or even death!
Also make sure that your line voltage agrees with the voltage indi-
cated by the switch setting on the back of the unit and that the right
fuse has been inserted!
Only with written consent from Thorlabs GmbH Munich changes to
single components may be carried out or components not supplied
by Thorlabs GmbH be used.
This precision device is only dispatchable if duly packed into the
complete original packaging including the plastic form parts. If
necessary, ask for a replacement package.
The LDC340 must not be operated in explosion endangered environ-
ments!

1.2 Safety
LDC340 / Page 5
Attention 
Laser modules can deliver up to several 100mW of (maybe) invisible
laser radiation!
When operated incorrectly, this can cause severe damage to your
eyes and health!
Be sure to pay strict attention to the safety recommendations of the
appropriate laser safety class!
This laser safety class is marked on your external laser source used.
Attention 
Mobile telephones, handy phones or other radio transmitters are not
to be used within the range of three meters of this unit since the
electromagnetic field intensity may then exceed the maximum
allowed disturbance values according to EN 50 082-1.

1.3 Ordering codes and Accessories
LDC340 / Page 6
1.3 Ordering codes and Accessories
Ordering-code Short description
LDC340 Laser diode controller, current range 0 ... 4 A / 6 V
LDC340-IEEE Laser diode controller, current range 0 ... 4 A / 6 V
with IEEE488 interface
laser diode mounts for different laser diode packages:
TCLDM9 Temperature controlled laser diode mount for 3- and 4-pin
TO18-packages (9 mm CD, 5.6 mm CD)
LDM21 Miniature sized temperature controlled laser diode mount for 3-
and 4-pin TO18-packages (9 mm CD, 5.6 mm CD)
LM14S2 laser diode mount for laser modules in a 14-pin butterfly-package
(programmable pinning)
Shielded cable:
CAB400 Cable to connect the laser diode controller LDC340 to a Laser
Diode Mount

2.1 Unpacking
LDC340 / Page 7
2 Getting Started
2.1 Unpacking
Inspect the shipping container for damage.
If the shipping container seems to be damaged, keep it until you have inspected the
contents and you have inspected the LDC340 mechanically and electrically.
Verify that you have received the following items:
1 LDC340
1 power cord, connector according to ordering country
1 operation manual
1 CD with drivers and software (LDC340-IEEE only)
1 Connection cable CAB400
2.2 Preparation
Prior to starting operating the LDC340, check if the line voltage indicated on the
mains voltage selector agrees with your local supply and if the appropriate fuse is
inserted. (To change the line voltage see 5.2)
Connect the unit to the line with the provided mains cable. Turn the unit on by means
of the mains switch.
Via the 4mm banana jack of the chassis ground the external optical build-up can be
connected to ground potential, if required.

2.3 Operating elements
LDC340 / Page 8
2.3 Operating elements
2.3.1 Front panel
Figure 1 Operating elements at the front panel
Line Key operated power switch, ON / Standby
Interface Change between remote and local
LED Display 4 ½ digit display
Mode Select operation mode
Adjust Main tuning knob
Setup Set diode polarities and bias voltage
Display Select the value to be displayed
Control Modulation in (max. ± 10 V) /
Analog out (max. ± 10 V) BNC-jacks
I
I
Remote / Local
Mains control
switch
Modulation Input Analog Output Display Selection Setup Main Setting
Knob
Laser ON / OFF
Mode select
Display

2.3 Operating elements
LDC340 / Page 9
2.3.2 Rear panel
Figure 2 Operating elements at the rear panel
The rear panel of the laser diode controller LDC340 contains the mains connector
with fuse, the output jack (9pin D-SUB), the external monitor diode input (BNC), the
temperature window protection input (BNC) as well as the preset DIP switch bank
and the PD gain control potentiometer.
If the LDC340 is equipped with the IEEE488.2 interface ( LDC340-IEEE) there is an
additional DIP switch bank to set the IEEE 488 device address. You will also find the
24pin IEEE488 jack.
Input for external monitor diode Fan Temp. win. protection input
IN
IEEE 488 Interface jack Mains voltage selector
Mains jack with fuse
DIP switch for interface configuration
DIP switch for “wake up“ preset
CP gain
Laser diode output
PD ext. (AG)
15V/5mA max
1
55
3
7
8
6
9
2
4
LED, Interl.
Interl. GND
LD GND
LD C (AG)
LD A (CG)
LD VC
LD VA
PD GND
PD
LDOUT CP
GAIN
2
3
4
5
7
8
PD int/ext
or I low/hi
const. I/P
LD CG/AG
1PDCG/AG
BIASoff/on
ILD off/on
IPD hi/low
WIN IN
TTL, 5V max
INTERFACE
IEEE 488
ON OFF1
8
TO AVOID ELECTRIC
SHOCK THE POWER CORD
PROTECTIVE GROUNDING
CONDUCTOR MUST BE
CONNECTED TO GROUND.
NO OPERATOR
SERVICEABLE
COMPONENTS INSIDE.
DO NOT REMOVE COVERS.
REFER SERVICING TO
QUALIFIED PERSONNEL.
Serial No.
LINE
50/60 Hz 125 VA I max FUSE
100 V
115 V
230 V
+15%
-10%
+15%
-10%
+15%
-10%
1.2 A
1.1 A
0.5 A
T2 A
T2 A
T1 A
Fuse Type IEC 5 x 20 mm
TEKTRONIX MUNICH GmbH
MADE INGERMANY
®

2.4 First operation
LDC340 / Page 10
2.4 First operation
Attention
Prior to switching on your LDC340 please check if the line voltage
set with the voltage selector at the rear panel corresponds to your
mains voltage!
Turn the unit on by means of the line switch.
Via the 4mm banana jack of the chassis ground the external optical build-up can be
connected to ground potential, if required. The ground pin of the laser diode is
internally connected to chassis ground.
After switching on the unit, the LED display must get visible. If no display is shown
please check line voltage and line fuse.
By using the display selection keys you can select the desired value to be displayed
at any time.
The LDC340 is immediately ready to use after turning on. The rated accuracy is
reached, however, after a warming-up time of approx. 10 minutes.

3.1 Presettings
LDC340 / Page 11
3 Operating the LDC340
3.1 Presettings
3.1.1 DIP switch for “wake up“ preset
By means of these 8 switches several preset functions define in which mode the
LDC340 will wake up when switched on.
SW1 and SW2 define the mode the LDC340 wakes up:
Mode SW1 SW2
const. current low range up up
const. current high range down up
const. power (internal PD) up down
const. power (external PD) down down
SW3 defines the polarity of the laser diode
LD polarity SW3
CG up
AG down
SW4 defines the polarity of the monitor diode
PD polarity SW4
CG up
AG down

3.1 Presettings
LDC340 / Page 12
SW5 defines if the bias voltage is automatically switched on when switching on the
LDC340
bias voltage SW5
off up
auto on down
Attention 
Before activating this function make sure that the monitor diode
polarity is set correctly when switching on
(SW4 must be set correctly).
If the photodiode is forward biased with a voltage a current will flow
through it that could damage or even destroy it.
SW6 not used
SW7 defines if the laser current (!) is switched on automatically if the LDC340 is
switched on (option).
laser current SW7
off up
auto on down
NOTE
This is an option that has to be ordered explicitly. This option can be
retrofitted.

3.1 Presettings
LDC340 / Page 13
SW8 defines the range of the monitor diode current
Depending on the type of monitor current and the power range you are working in
your monitor diode will deliver a monitor current in a wide range. Therefore the
LDC340 provides two monitor current ranges:
IPD range SW8
high up
low down
3.1.2 Setting the limit of the laser current ILD LIM
To protect the laser diode the maximum possible current at the output of the LDC340
can be limited.
This hardware limit is set by the 25-turn potentiometer marked ADJ located next to
the LED ILD LIM at the front of the LDC340. The hardware limit is displayed
continuously on the display if the display ILD LIM is selected.
3.1.3 Setting the limit of the monitor diode current IPD LIM
To protect the laser diode the maximum possible optical output power can be limited.
Therefore a maximum monitor diode current can be set.
This maximum monitor current is set with the 25-turn potentiometer marked ADJ
located next to the LED IPD LIM at the front of the LDC340. The maximum monitor
current is displayed continuously on the display if the display IPD LIM is selected.
Attention 
The monitor diode current limit has a slow reaction time so you
might see overshoots in some special cases. This overshoots are
limited by the laser diode current limit according 3.1.2.

3.1 Presettings
LDC340 / Page 14
3.1.4 Adjusting the power display of an internal monitor diode
The optical power can be displayed if the display PLD is selected.
Therefore the monitor current is translated into power display that can be calibrated
with the 25-turn potentiometer marked CAL located next to the LED PLD at the front of
the LDC340.
The position of the potentiometer determines which monitor current corresponds to
which optical power.
NOTE
This is the description of how to calibrate the power display in local mode
using the display of the LDC340. When using the IEEE488 interface the
calibration of the optical power is done completely different. The CAL
potentiometer does not affect the value measured via interface.
(Refer to chapter 4, “Communicating with a control computer“ on page 27)
Adjustment
During the whole procedure the laser remains switched off.
First select the operating mode P and the display IPD at the LDC340.
Then take the maximum optical output power and the corresponding monitor current
from the datasheet of the laser diode. Sometimes you must calculate one value using
the monitor diode efficiency (parameter η).
Now set the pre-set value for the monitor current to this value.
Finally switch to the display PLD so that the power belonging to the set monitor diode
is shown. Use the potentiometer CAL next to the LED PLD to adjust this display to the
corresponding value of the output power.