THORLABS ULN15TK User manual

ULN15TK
Ultra-Low-Noise Laser System
User Guide

Ultra-Low-Noise Laser System
Table of Contents
Chapter 1 Safety.........................................................................................................................1
Chapter 2 Description.................................................................................................................2
Chapter 3 Setup..........................................................................................................................3
Chapter 4 Software Communications..........................................................................................6
4.2.1 List of States........................................................................................................................................................ 7
4.2.2 List of Tags........................................................................................................................................................... 8
4.2.3 List of Names....................................................................................................................................................... 9
Chapter 5 Making Safety Interlock Connections ........................................................................11
Chapter 6 General Maintenance ...............................................................................................12
Chapter 7 Specifications ...........................................................................................................13
Chapter 8 Mechanical Drawings................................................................................................15
Chapter 9 Certifications and Compliance...................................................................................16
Chapter 10 Warranty and RMA Information................................................................................17
Chapter 11 Thorlabs Worldwide Contacts ...................................................................................18

Ultra-Low-Noise Laser System Chapter 1: Safety
Rev. A, August 17, 2022 Page 1
Chapter 1 Safety
Explosion Warning
This instrument must not be operated in an explosion endangered environment.
Laser Warning
Avoid Exposure –Radiation Emitted from apertures. Do not look into the laser aperture while the laser
is on. Injury to the eye may result. Laser should not be turned on unless there is an optical fiber
connected to the laser output port. Caution –Use of controls or adjustments or performance of
procedures other than those specified herein may result in hazardous radiation exposure.
Caution
This instrument should be kept clear of environments where liquid spills or condensing
moisture are likely. It is not water resistant. To avoid damage to the instrument, do not expose
it to spray, liquids, or solvents.
Note: This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to
part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference
in a residential installation. This equipment generates, uses and can radiate radio frequency energy and, if not
installed and used in accordance with the instructions, may cause harmful interference to radio communications.
However, there is no guarantee that interference will not occur in a particular installation. If this equipment does
cause harmful interference to radio or television reception, which can be determined by turning the equipment
off and on, the user is encouraged to try to correct the interference by one or more of the following measures:
Reorient or relocate the receiving antenna.—Increase the separation between the equipment and receiver.—
Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.—Consult
the dealer or an experienced radio/TV technician for help.

Ultra-Low-Noise Laser System Chapter 2: Description
Page 2 TTN282198 -D02
Chapter 2 Description
Thorlabs’ ULN15TK is a turnkey, ultra-low-noise (ULN) laser system. The device integrates Thorlabs’ ULN15PC
component in an extended butterfly package with a low-noise driver and temperature stabilization system inside
a benchtop housing. The driver electronics are designed to minimize the current noise such that the specified
narrow linewidth of the ULN15PC laser can be achieved. The drive electronics also includes two temperature
stabilization circuits for the laser chip as well as the Fiber Bragg Grating (FBG). Additionally, the temperature of
the laser case is stabilized through a third temperature stabilization circuit to provide long-term power and
wavelength stability when the system is used in standard laboratory environments. A fiber isolator is integrated
at the output of the laser in order to minimize the impact of any back-reflected light on the laser. The system is
powered using Thorlabs’ DS12 power supply (12 V, 4 A).
The single-frequency operation of the laser as well as its linewidth and noise properties are a function of the
operating conditions (driver current and FBG temperature). Please see the ULN15PC product presentation and
manual for additional details. The ULN15TK turnkey ULN laser system is pre-set to the optimal operating
conditions that minimize the laser linewidth, while providing the highest output power and long-term stability.
The laser is shipped with test data taken at those pre-set operating conditions. An enable push button switch can
enable the laser at a pre-set current level. In applications where modifying the laser operating conditions might
be desired, the laser operating set-points can be adjusted using a command-line interface via USB connection to
the back panel of the instrument. The remote operation via the USB connection also allows turning the laser on
and off, as well as reading the status indicators of the device.
The laser system includes three analog modulation inputs (SMA connectors on the front panel). Two modulation
ports are included for changing the laser current by +/- 10 mA. One of these ports is AC-coupled and can provide
a higher modulation frequency, and the other port is a DC-coupled port with lower modulation frequency. A third
modulation port enables changing the FBG and the chip temperature using an analog voltage. This feature is
turned off by default but can be switched on using a command sent through the USB interface. Please refer to
Section 3.3 of this manual for additional details.
Shipping List
The ULN15TK laser system consists of the following components:
•Ultra-Low-Noise Laser System
•DS12 Power Supply (12 V, 4 A)
•USB-AB-72 USB 2.0 Type-A to Mini-B Cable, 72" (1.83 m) Long
•FBC250 Connector and Bulkhead Cleaner

Ultra-Low-Noise Laser System Chapter 3: Setup
Rev. A, August 17, 2022 Page 3
Chapter 3 Setup
Caution
Prior to using the ULN systems, it is highly recommended to clean the output bulkhead as well as the
connector facets to be connected to the bulkhead. Failure to clean the connectors can result in damage
to the internal connector.
When cleaning the connectors, ensure that the laser is powered off by turning off the push-button
switch. Never inspect optical connectors unless all light sources in your setup have been switched off.
Front and Back Panel Overview
Figure 1 Front and Rear Panels of the ULN15TK Laser System
Laser Enable Push-
Button Switch
Modulation Input
(SMA Female)
Laser Output Port
(PM, FC/APC Bulkhead)
Status Indicator LEDs
USB Connection
(USB Mini-B)
Connector)
RS-485 Connection
(9-Pin Female D-Sub)
Remote Interlock Pin
(2.5 mm Phono Plug, See Chapter 5)
DC Input
(M8 Connector for DS12 Power Supply)

Ultra-Low-Noise Laser System Chapter 3: Setup
Page 4 TTN282198 -D02
Operating the Laser
1. Please consult with your organization’s laser safety officer regarding proper operation of the laser at your
institution.
2. It is highly recommended to secure the laser to an optical table or metal breadboard. This improves heat
dissipation from the laser housing and its long-term thermal stability. The laser housing includes two sets
of mounting holes (4x) designed for Imperial and Metric breadboards.
3. Ensure the interlock pin is fully installed
a
,
b
.
4. Connect the DC power supply (DS12) via the M8 connector on the back panel of the system. The Power
indicator on the front panel should be illuminated.
5. With power supplied, the ULN15TK system will immediately begin stabilizing the laser case temperature.
During laser case temperature stabilization, the Status indicator will blink. The system may require 1 - 2
minutes for basic thermal stability, during which time the laser cannot be turned on. When the laser case
temperature is stabilized, the Status indicator will turn off.
6. Connect any applicable modulation signals to the appropriate SMA modulation ports.
7. Remove the output fiber connector bulkhead cap and connect to the desired instrument using an
PM1550-XP FC/APC fiber patch cable.
8. The Laser is ready to be turned on and can be turned on by toggling the Enable push-button
c
. The Emission
indicator will blink for 5 seconds then remain solid at which point the laser emission is on. The laser
emission is not on during the blinking stage of the Emission indicator. Please note that the laser requires
a 10 minute warm-up time after it has been enabled in order to reach its specified linewidth.
9. Laser emission can be turned off with another toggle of the Enable push-button.
10. At any time, if the ULN15TK system detects a fault, the status indicator will light up solid and the laser will
be shut off.
11. To change the laser operating conditions, connect to the USB mini-B connector to configure settings for
the system. A list of commands and parameters are listed in Chapter 4 Software Communications.
External Modulation Ports
There are three modulation ports located on the front panel of the ULN15TK. Two ports are allocated for
modulating the current of the laser around the current set-point. The AC current modulation port is AC-coupled
and supports modulation frequencies from 2 kHz to 20 MHz. The DC current modulation port is DC-coupled and
supports frequencies from 0 Hz to 5 MHz. For both current modulation ports, an input voltage (-5 V to +5 V)
modulates the current at a rate of 2 mA/V around the current set-point. A third modulation port is included for
modulating the temperature of the laser around its set-point. Either the chip or the FBG temperature can be
controlled through the analog voltage input applied to this port (-5 V to +5 V). This port has a bandwidth of 1 Hz
and is designed for slow modulation of the laser temperature for applications that require locking the laser
frequency. The temperature modulation port is disabled by default and can be enabled to control either the chip
or the FBG temperature through a command sent via the USB or RS-485 connection on the back panel of the laser.
The rate of temperature change versus voltage can also be set through a command. Please see Chapter 5 for
a
An improperly installed interlock pin will not allow the laser to turn on, but will not be indicated as an error by the Error
indicator.
b
If the ULN system is powered on without the interlock pin, it must be power-cycled (unplugged from DC power supply and
reconnected) before the laser can be turned on.
c
For safety, a firm, deliberate button press is required.

Ultra-Low-Noise Laser System Chapter 3: Setup
Rev. A, August 17, 2022 Page 5
details on the commands for setting up the temperature modulation input. All modulation ports have an input
impedance of approximately 1 kOhm.

Ultra-Low-Noise Laser System Chapter 4: Software Communications
Page 6 TTN282198 -D02
Chapter 4 Software Communications
Each device is equipped with an USB mini-B style connector for USB communication with a host device. The device
will enumerate as a Virtual COM port on the host device. For Windows PCs running Windows 10 or later, no special
driver is required. For Windows PCs prior to Windows 10, the driver included as part of the firmware update utility
is required.
All communication queries must be terminated by a single carriage return character (\r) or a combined carriage
return and newline (\r\n). Communications originating from the device will be terminated by one or more
combined carriage return, newline pairs (\r\n). A connected host should not attempt to send additional queries
until a response has been received from the device. Most queries will result in a response within 10ms. Queries
requesting the saving of configuration parameters will result in longer response times.
The commands sent from the USB interface enable the following functions:
•Turning the laser on or off
•Reading status of the laser, and values of the laser temperature set-points
•Adjusting the temperature set-points for the chip and the FBG
•Adjusting the drive current of the laser
•Setting the external temperature modulation port function. The default for this port is to be disabled, but
it can be changed to adjust either the chip or the FBG temperature based on the analog voltage applied
to this port.
In addition to the USB port, a RS-485 port has also been included on the back panel of the system. This port, a 9-
pin D-Sub, can be used with the same command set outlined in this chapter through the RS-485 communication
protocol. Please refer to the last sub-section in this chapter to see the pin-out of the D-Sub connector.
Command/Response Structure
All commands are text based with the basic format as follows:
command [param1 [param2..[paramN]]]
Proper syntax will be specified for each command in the following subsections. Each command will be followed
by a corresponding response with the following format:
Response_code:Response_Text[command_response]
Note that all commands and parameters are lower-case letters.

Ultra-Low-Noise Laser System Chapter 4: Software Communications
Rev. A, August 17, 2022 Page 7
List of Commands
See corresponding subsections for details.
Command
Descriptions
laser [state]
Set the user requested state of the laser.
write_param [tag] [value]
Write a parameter to the device
read_param [tag]
Read a parameter from the device
save_param [tag]
Immediately write a parameter to EEPROM.
read_string [name]
Read a string value from the device
savecfg
Save all parameters on the main and optics boards to non-volatile
memory.
get_clock
Gets the currently set time and date.
update
Places the system into a mode where it can accept firmware updates from
the PC.
reset
Reset the system. Note that this will drop the USB connection.
firmware_version
Read the current firmware version number.
4.2.1 List of States
Corresponding to the ‘laser’ command
Command
Descriptions
on
Set the requested state to on.
When system failures are cleared and interlock indicates OK, the laser till turn on.
When system errors occur or when interlock is lost, the laser is tuned off.
off
Laser is turned off.

Ultra-Low-Noise Laser System Chapter 4: Software Communications
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4.2.2 List of Tags
Corresponding to the ‘write_param,’ ‘read_param,’ and ‘save_param’ commands
Name
Type
Default
Value
Access
Descriptions
Laser Configuration
laser_state
Int.
N/A
R
60 = Laser on
61 = Laser off (Normal)
62 = Laser off because of interlock
63 = Laser off because of one of the
following faults:
• Laser TEC in error mode
• FBG TEC in error mode
• AUX TEC timeout
64 = Laser state is unknown
65 = Laser is starting (flashing LED)
laser.current
Float
0
R/W
Nominal open-loop laser current (A)
laser.case.temperature
Float
N/A
R
Laser case temperature reading in Celsius.
Laser TEC Control System
laser_tec_ctrl.temperature
Float
N/A
R
Laser temperature reading in Celsius.
laser_tec_ctrl.setpoint
Float
25
R/W
Set point for the laser TEC control system.
(deg C)
FBG TEC Control System
fbg_tec_ctrl.temperature
Float
N/A
R
FBG temperature reading in Celsius.
fbg_tec_ctrl.setpoint
Float
25
R/W
Set point for the FBG TEC control system.
(deg C)
External TEC Setpoint Adjustment
tec_adj.select
Int
120
R/W
The selected TEC control on which tec_adj
acts:
120: None
121: Laser TEC
122: FBG TEC
tec_adj.range
Float
1
R/W
The full-scale range of the TEC setpoint
adjustment +/- (deg C)
tec_adj
Float
N/A
R
The active tec setpoint adjustment applied
to the selected TEC (deg C)