20mA - 4A Laser Diode Drivers

Modes
With the laser diode controllers of the LDC200C series, laser diodes can be driven in constant current (CC) or constant power (CP) mode. All laser diode and photodiode configuration types are supported. The laser diode is always driven with respect to ground. In comparison to driver designs that require a floating ground, this grounded operation of the laser diode offers advantages regarding noise, transient suppression, and stability.

Constant Current
In CC mode, the current to the laser is held precisely at the prescribed level. This mode is used when the lowest noise and highest response speed is required. Most applications in this mode require stabilizing the temperature as well. We offer two lines of temperature controllers, a 12 W TEC or a 40 W TEC.

Constant Power
In CP mode, the internal photodiode integrated into most laser diode packages is used to actively stabilize the laser's output power, which is adjusted by a feedback circuit. An adjustment of the full scale photodiode current in CP mode is provided in order to compensate for the differences in the photodiode currents between different laser diodes.

Controller Use
Intuitive User-Friendly Operation
Independent of the selected operating mode, the 5-digit LED display current, or laser limit, can show the laser current, the photodiode monitor current, or laser current limit. It can also display the optical power (in mW). The power readout can be calibrated to the responsivity of the monitor photodiode by adjusting a front panel trim potentiometer.

Benefits
In many applications, the aforementioned benefits eliminate the need for a separate optical power meter. Available for use at the rear of the unit are: a modulation input for laser current or power, and a control output proportional to the laser current.

Protection Features
Current Limit
A precisely adjustable current limit ensures that the maximum laser current cannot be exceeded. Thorlabs has intentionally provided limited access to this feature to prevent accidental adjustment. An attempt to increase the laser drive current above the pre-set limit will result in a visible and short audible indicator. Even when utilizing the external modulation feature, the current limit set-point cannot be exceeded.

Current Source
If the connection between the current source and laser diode is interrupted, the current source automatically switches off the current output. The open current circuit condition is indicated by the LED "OPEN" and a short acoustic warning. The separate laser ON key switches the laser current on and off. When switched off, an electronic switch within the LDC200C short circuits the laser diode for added protection. After being switched on, a soft start ensures a slow increase of the laser current without voltage peaks. Even in the case of line failure, the laser current remains transient-free. Voltage peaks on the AC line are effectively suppressed by electrical filters, shielding of the transformer, and careful grounding of the chassis.

Features
Extremely Low Noise (LDC201CU 0.2 μA)
5-Digit Display With 10 μA Resolution
Analog Control Input and Output
Reliable Laser Diode Protection
Operates With All Polarities of Laser Diode and Photodiode
Seven Models With Laser Current Ranges From 20mA to 4A
The laser diode controllers in the LDC200C series all provide features that ensure outstanding performance. There are seven models with different current ranges, each configured to provide optimal performance for their particular application. Please refer to the Specs tab and the Selection Guide tab for an overview of the products.