The new LDX-3500B Series Laser Diode Drivers are a family of low noise high stability current sources specifically for precision control of low to high power laser diodes. Three models with a maximum output current range from 200 mA to 6A operate in constant current or constant optical power modes to cover a wide range of laser diode testing and control applications.
Remote instrument operation is available on all LDX-3500B Series Laser Diode Drivers through a USB 2.0 serial interface. All instrument controls and functions are accessible through the serial interface for easy remote programming and control in automated test and control systems where repeatable and accurate test sequencing, measurements, and data handling are required. Installation software available with each instrument in a very easy to read and change format facilitates instrument set up and control in minutes. Through this software, instrument controls are organized similar to the front panel for easy, intuitive instrument remote control and monitoring. Also included is an example L-I application written in C# with the source code for reference. Whether the application is data intensive L-I testing or control in R&D manufacturing testing, remote operation of the LDX-3500B saves time and ensures systematic data collection and instrument operation.
The LDX-3500B Series Laser Diode Drivers are microprocessor controlled instruments. The front panel of the LDX-3500B Series was designed for quick and easy instrument operation and information display. A bright five digit, green LED display is easy to read from a distance, even with laser safety glasses Parameters and instrument modes are grouped without confusing multi-function keys. Informative error indicators such as open circuit, current and power limit let the user resolve set-up and operational problems quickly.
Each LDX-3500B Series Laser Diode Driver was designed as a current source specifically for low to high power laser diodes. Stable, precision low noise current control with a set point accuracy of 0.1% is delivered to the laser during R&D or manufacturing testing including L-I testing, qualification testing or automated testing and control applications.
The LDX-3500B architecture simplifies routine maintenance; calibration of the laser current source can be performed via the front panel or remotely through the USB 2.0 interface, without opening the instrument up or manual adjustments. A calibration mode is entered through unique push button combinations or control commands, and all calibration data is easily entered via the front panel with the adjust knob or commands. Calibration data is automatically stored in on-board non-volatile memory.
The LDX-3500B Series Laser Diode Drivers control the current to the laser diode in one of three modes: Constant current low bandwidth, Constant current high bandwidth, and Constant optical power. The Constant Current, low bandwidth mode offers improved noise performance and is optimized for DC operation. In Constant Current high bandwidth mode, the output stage supports higher modulation frequencies, up to 500 kHz, for dithering the laser current for power and wavelength tuning. For laser protection, the modulation input is implemented as a differential input, allowing the modulation control voltage and laser outputs to use different grounds. The Constant Power mode provides constant optical power operation of your laser diode by using the photocurrent from the laser’s rear facet photodiode or from an external photodiode measuring front facet light in a feedback control loop to the current source for precise and stable optical power control.
The LDX-3500B Series Laser Diode Driver provides multiple laser diode protection features such as independent hardware current limits, slow-start turn-on circuits, and isolated supplies. The output of the drivers are bound by fully independent current limits. A "clamping" circuit topology prevents the limits from being exceeded under any condition including current modulation. An output shorting switch provides a safe method of switching the output on and off during operation while protecting the laser during load/unload or connect/disconnect operations. Also, if the instrument senses an open circuit, the output will immediately shut off followed by the illumination of the appropriate fault indicator. During AC power-up, the laser is protected from current transients by power line filters, double shielded transformers and hardware and firmware turn-on sequencing. When the output is enabled, slow start circuits gradually open shorting FETs allowing current to slowly be diverted to the laser. Transients from normal instrument operation such as output on/off have been thoroughly tested and minimized as well as transients from inadvertent instrument operation (such as mode switching).