Keithley offers complete pulsed power measurement solution for testing laser diodes

August 20, 2002 --Keithley Instruments today introduced an integrating sphere photodetector (Model 2520INT), that together with the company's pulsed laser diode test system (Model 2520) offer the industry's only complete pulsed source and measure solution for light-current-voltage (LIV) testing. Combined their capabilities can produce high accuracy measurements of laser diode optical power at the wafer, bar, or chip level, prior to their integration into complete, temperature-controlled laser diode modules.

The Model 2520INT utilizes a 1-inch sphere with a germanium detector to give a wide operating range of telecommunications wavelengths, maximize ease of setup and integration, and achieve low-level power measurement. The device offers production test engineers the flexibility to test devices earlier in the production process, so non-compliant devices can be detected before they are packaged, reducing the manufacturer's investment in defective products. It also shortens testing time by offering an SMA fiber tap to allow measured light to be sent to another instrument simultaneously for additional optical measurements. The 2520INT's design simplifies integration into both production and lab environments.

Markets and applications
The Model 2520INT/2520 combination can be used for LIV production testing of 980-nm and 1480-nm erbium-doped fiber amplifier pump lasers, Raman amplifiers, laser diodes, and vertical-cavity surface-emitting lasers.

By their design, integrating spheres naturally attenuate a laser diode's output power, so that the power level at any point on the sphere surface is far less than the power of a beam that falls directly on the detector. The Model 2520INT's highly reflective Spectralon interior surface scatters, reflects, and diffuses the light output from the device under test uniformly over the interior surface of the sphere, with minimal absorption loss. This diffusion automatically attenuates the level of power visible to the built-in detector, and permits testing much higher power devices without damaging the detector.

Keithley developed the Model 2520INT to address the challenges specific to pulse testing laser diodes, which include short pulse periods and fast rise times. Many optical power detectors are hampered by long rise times, so they can only measure a portion of the laser diode's light output. The 2520INT's provides the high-speed response needed to handle pulse widths as short as 500 ns, and operating wavelength ranges of 700-nm to 1700-nm. It can measure outputs of up to 7 W, depending on wavelength. Calibration constants are provided in printed form and on diskette for easy programming of test systems.

The Model 2520INT-1-GE integrating sphere is priced at $5995. Delivery is expected this month. Options include the Model 2520 pulsed laser diode test system, and the Model 7078-TRX low-noise Triax cable. For more information visit Keithley's Web site at www.keithley.com.