Low-Noise Laser Diode Driver with Dual-Channel Temperature Controllers

Features

• Low-Noise Drive Current up to 1 A
• Two Integrated 3.5 A TEC Controllers
• AC Current Modulation up to 20 MHz
• DC Current and Temperature Modulation
• Operation via USB 2.0, RS-232, Ethernet and Touchscreen Front Panel

Click to Enlarge
Figure 1.1  The LNC31 laser diode driver used with a ULN15PC ultra-low-noise laser diode mounted in a LM14TS active mount. 

Thorlabs' LNC31 low-noise laser diode driver is a low-noise benchtop driver, designed to drive high-performance lasers such as Thorlabs' ULN butterfly lasers and other laser diodes that are sensitive to electrical current noise (e.g., our DBR or DFB diodes). Inspired by the design used in our ULN13TK and ULN15TK turn-key lasers, it combines a low-noise laser current driver with two independent thermoelectric cooler (TEC) controllers in a compact benchtop unit featuring a large, intuitive touchscreen interface. A fanless, passively cooled design helps eliminate mechanical vibrations and minimizes electrical noise, offering cleaner performance than typical active-cooled drivers. For optimal performance in noise-sensitive applications, the LNC31 driver is designed to be used with Thorlabs’ LM14TS active butterfly mount (see Figure 1.1), which provides case temperature stabilization for a reduced noise floor and further enhances optical stability.

The LNC31 driver’s laser driver delivers up to 1 A of low-noise current with excellent stability. It supports both cathode-grounded and floating diode configurations and offers both DC- and AC-coupled current modulation, with AC modulation bandwidth up to 20 MHz. One TEC channel also supports external temperature modulation, enabling wavelength tuning via temperature adjustment for laser locking applications. See the Specs tab for more information.

Both TEC controllers operate independently and can each supply up to 3.5 A, allowing precise temperature stabilization of the laser chip and a secondary thermal load such as the fiber Bragg grating (FBG) in ULN lasers. See the Graphs tab for more information on the noise characteristics of this laser diode driver.

Operation
In addition to the physical controls and touch screen on the front panel, the LNC31 driver includes USB, RS-232, and Ethernet interfaces for remote control using serial commands for integration into automated systems. When the LNC31 driver receives a valid serial command via either USB, Ethernet, or RS-232 interface, the device will enter “Remote Operation” mode and the touch screen & other physical controls on the front panel will become inactive. For driver software, as well as programming reference guides for full list of commands, please see the Software tab. A USB-A-79 USB 2.0 Type-A to Type-B Cable is included with the driver. A 9-Pin female D-sub connector is included on the back panel of the system for laser diode connection, and a CAB400 current controller cable is included with the driver. Each device has two 15-Pin female D-sub connectors for TEC connections, and two CAB420-15 temperature controller cables are included. A 9-Pin female D-sub connector is also included on the back panel of the system for RS-232 communication protocol. Please refer to the Pin Diagrams tab for the pin assignment of the 9-pin D-sub connectors and 15-pin D-sub connectors, and the Shipping List tab for a complete list of items included with the driver.

Applications

Lasers with inherently narrow linewidth and low noise require a driver current with minimal current noise to reach their specified optical performance. The LNC31 is recommended for any application where minimizing the laser linewidth (and therefore, maximizing the coherence length) and its intensity noise is desired. Examples of such applications include optical sensing, generating optical carriers for RF-over-fiber or coherent optical communication systems. Additionally, narrow linewidth performance is needed in applications involving optical cavities, for example in pumping micro-ring resonators to generate frequency combs.

With its low-noise drive current, high-speed modulation capability, and precise thermal control, the LNC31 driver is ideal for applications such as vapor cell and cavity locking, neutral atom and ion-based quantum computing, Rydberg atom experiments, atomic cooling, and wavemeter stabilization. The laser diode driver can be combined with our DBR butterfly laser diodes and an LM14TS active mount for atomic cooling of rubidium (Item # DBR780PN, tuned to the Rb D₂ transition, or Item # DBR795PN, tuned to the Rb D₁ transition) or cesium (Item # DBR852PN).

This laser diode driver can be used with our saturated absorption spectroscopy system, as well as our dichroic atomic vapor spectroscopy kit. This driver is ideally suited for frequency locking a laser by splitting the output into counter-propagating pump and probe beams through a vapor reference cell. This technique allows for locking to narrow hyperfine transitions, known as Lamb dips, within the broader Doppler-broadened absorption profile, providing sharp error signals for laser frequency stabilization. By combining these lasers with modulation and feedback electronics, such as the DSC1 Digital Servo Controller and the PDB210A Balanced Photodetector, one can achieve robust, long-term frequency locking to the atomic transitions - an essential requirement for applications such as atomic clocks, laser cooling, and quantum sensing.

Thorlabs also offers low-noise turnkey 1310 nm and 1550 nm systems, as well as 780 and 795 nm turnkey systems targeting rubidium transitions, which integrate butterfly lasers with a low-noise driver and temperature stabilization inside of a benchtop housing.

Figures 3.1 and 3.2 represent the typical performance of the LNC31 laser diode driver, compared with the mount and laser driven by a LDC210C controller, and our low-noise turnkey ULN15TK laser system.

Click to Enlarge
Click Here for Data
Figure 3.1 Example frequency noise data of a ULN15PC laser in a LM14TS active mount, driven by the LNC31 laser diode driver, compared with the mount and laser driven by a LDC210C controller, and a low-noise turnkey ULN15TK laser system. Using an LDC210C to drive the laser requires two separate TEC drivers, such as TED200C temperature controller.

Click to Enlarge
Figure 3.2  The typical relative intensity noise (RIN) of a ULN15PC laser in a LM14TS active mount, driven by the LNC31 laser diode driver, compared with the mount and laser driven by a LDC210C controller, and a low-noise turnkey ULN15TK laser system. Using an LDC210C to drive the laser requires two separate TEC drivers, such as TED200C temperature controller.

Figure 3.3 represents electrical current noise and the relative intensity noise (RIN) for this low-noise laser diode driver.

Click to Enlarge
Figure 3.3  Example electrical current noise data for a ULN15PC laser in a LM14TS active mount, driven by the LNC31 laser diode driver. The integrated electrical current noise is 0.1 µA RMS over 10 Hz - 1 MHz.

Firmware

Version 1.1.2

Click the button to visit the LNC31 software page.

The Software button links to firmware, utilities, and support documentation for Thorlabs' LNC31 Laser Diode Driver.

The software download page also offers programming reference notes for interfacing with compatible controllers using SCPI. Please see the Programmer's Reference tab on the software download page for more information and download links.

Firmware Update Tool
The Firmware Update Tool allows for updating the firmware of our LNC31 laser diode drivers with a Windows PC. The software requires a computer running the Windows^® 10 operating system or higher.

Custom Control via SCPI Commands
The laser diode driver Programmer's Reference lists commands that can also be used to control the laser diode driver. The commands can be sent from a computer running the Windows^® 10 operating system or higher to the USB, Ethernet, or RS-232 port. Descriptions of each command are included in the Programmer's Reference.