SRS LDC500 Laser Diode Controller

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Introducing the Stanford Research Systems LDC500 Series Laser Diode Controllers highly stable, low-noise current sources, with integrated temperature controllers all at very affordable prices. The SRS LDC500 series have an intuitive user interface, and many first time users will be able to operate the instrument without having to crack open the manual (although we do recommend reading the manual). Unlike competitive models, the LDC500 series controllers have dedicated front-panel displays for parameter entry. You don’t have to sacrifice monitoring temperature or current to simply change an instrument setting you have a separate two-line, blue alpha-numeric display for that. In addition, bright 5-digit green LED displays constantly monitor current and temperature, and are large enough to easily read from anywhere in the lab.

Laser Diode Protection
Multiple laser diode protection features, including slow start turn-on, adjustable current limits, and adjustable compliance voltage, keep your laser diodes safe when unexpected events occur. Fast clamping and shut down provide extra protection against intermittent contact with the laser. Combined, these features provide trouble-free, safe control of your laser diode.

Linear Power Supplies
Independent linear power supplies are used for the laser diode controller and the temperature controller. The supplies are designed with a magnetically shielded toroidal transformer, and provide ultra-clean, stable isolated power.

Computer Control
Remote operation of the LDC500 series is supported with GPIB, RS-232 and Ethernet interfaces. All instrument functions can be controlled and read over any of the interfaces. Up to nine complete instrument configurations can be saved in non-volatile RAM and recalled at any time.

Stable Laser Diode Controller
To ensure a stable optical output from your laser diode, the LDC500 series LD controller was designed to deliver noise-free, precision operation. It’s accurate to ±0.01 %, noise is less than 2 µA rms, and it meets a drift specification of 10 ppm/°C.

Two modes of operation are available for the laser diode current source: constant current mode (CC) programs the source to a precise DC amplitude. Alternatively, the constant optical power mode (CP) servos the current source to maintain a constant signal on a monitor photodiode. Both control modes allow you to add an external modulation signal, with adjustable bandwidth up to 1.2 MHz (in CC mode) or 10 kHz (in CP mode).

A unique feature of the LDC500 series is Dynamic “Bumpless” Transfer between CC and CP modes. This feature means you don’t have to shut down your laser to switch modes — simply press the Current/Power button.

Another convenient feature that the LDC500 series offers is a fully programmable photodiode bias voltage. You can set the bias between 0 and 5 V from the front panel, or remotely using one of the computer interfaces.

The LDC500 series integrated 36 W temperature controller lets you adjust temperature with 0.001 ºC resolution, and measure temperature with 0.01 ºC accuracy (with a calibrated sensor). It maintains a typical stability of 0.0005 ºC/ºC with respect to room temperature, and has a very wide temperature control range.

The TEC controller also has two modes of operation: constant temperature mode (CT) controls the TEC current to maintain a fixed temperature (or raw sensor value), while constant current mode (CC) operates the TEC at a fixed current. Thermistor, RTD and IC sensors are all supported.

The LDC500 series has an auto-tuning feature which automatically optimizes the PID loop parameters of the controller. Of course, full manual control is provided too. Dynamic transfer between CT and CC modes for the TEC is also easy — just press the Temp/Current button.

Thermal Stability
Temperature fluctuations in a typical laboratory environment can often exceed several degrees Celsius over the course of a day. Small temperature changes can mean significant current changes in your laser diode if your controller is not up to the task.

The LDC500 and LDC501 has a temperature coefficient of 10 ppm/°C, which is a factor of five better than competing models, making it the ideal controller for precision laser diode experiments.

The temperature performance of the LDC500 series. Over a 24 hour period, the ambient temperature change in the laboratory exceeds two degrees Celsius. Note that the output current deviation of the LDC after warm-up is stable to better than ±10 ppm.