LDT-5900 controllers provide the finest balance of features for today’s temperature control needs in laser diode and component testing. In addition to wide temperature control range and uncompromising stability, these instruments combine a fully digital PID feedback loop with a precision 24-bit measurement system for the utmost capability in temperature control and measurement. Control and display temperature from -50°C to 250°C while delivering a low-noise, bipolar current (up to 10A) to the thermo-electric module. This unique temperature control topology offers fast settling time and temperature stability better than 0.005°C - ideal for laser diode applications requiring highly stable wavelength and optical power. Additional features like four-wire voltage and sensor measurements and an AC resistance measurement make these instruments perfect for characterizing TE modules during laser module development, testing, or assembly. Input and output triggers, standard GPIB control, and an auto-tune algorithm all work to accelerate and simplify test automation.

The above figure figure shows that the threshold current and differential responsivity of a laser diode are strongly affected by the laser’s temperature. The laser threshold will increase exponentially with temperature as exp(T/T0), where T is the laser temperature and T0 is the “characteristic temperature” of the laser (typically between 60 to 150°C). T0 is a measure of the temperature sensitivity of the device with higher values implying that the device is more thermally stable. T0 is an important laser diode characteristic and is commonly extracted from multiple L-I curves. Changes in temperature also affect the bandgap of the semiconductor junction and therefore, the peak wavelength of the gain profile. This results in a linear relationship between temperature and the center wavelength of the laser diode (see above figure) with typical temperature tuning coefficients of 0.3 nm/°C. As a result, a temperature controller plays a key role in determining the laser wavelength. Please see Fundamentals of Laser Diode Control for additional information.

In addition to precision temperature control, the LDT-5900 Series provides four-wire voltage and sensor measurement for the most accurate characterization of laser diode module power consumption and reliable measurements. Independent heating and cooling current limits help achieve the fastest settling times, while protecting your device under all instrument modes. If your application requires checking the integrity of the TE device before and after installation into a module or device, there is no need for a separate instrument. The LDT-5900 Series provides an AC resistance measurement mode that outputs a low level AC current to the device under test and calculates its corresponding resistance.

These LDT-5900 Series come standard with a high speed GPIB remote interface as well as RS-232 serial communication capability. For quick instrument response without a command program, a TTL trigger-in function steps the instrument through a preprogrammed series of temperature setpoints. A trigger-out signal indicates when the set point has been reached.