Introduction
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Calibration process
High-speed detector measurements

High-speed optical and Electrical measurements
Lasre power and energy calibrations
General measurements
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Welcome to the National Institute of Standard and Technology Optoelectronics Division.
Calibration Services - Calibration process
CALIBRATION PROCESS

In the C Series Calorimeter shown in the schematic and photo below, light is collected in a cylindrical trap blackened on the inside to absorb the light. The temperature rise from the absorbed light, or from electrical power dissipated in resistive coils, is measured with thermocouples.
C-Series Calorimeter schematic.
The C-Series Calorimeter

The Q Series Calorimeter
The K Series Calorimeter
A Cryogenic Radiometer
A BB Calorimeter
Comparisons between these standards and a customer's detector or power meter are usually made using a wedged beamsplitter as shown below. Collimated light from a laser striking the beamsplitter is reflected and refracted into many beams. The power in each beam, relative to the input beam, can be calculated from Fresnel's equations or measured directly using calibrated power meters. In calibration, the standard is usually placed in the zero-order (principal transmitted beam, and the instrument under test in one of the reflected or other transmitted beams Ratios as small as 10-6 can be obtained.
Wedged Beamsplitter schematic
Optical Trap Detectors

In some cases, it is necessary or useful to calibrate a customer's instrument against a transfer standard. Several detector designs have been developed for this purpose. Generally they involve some form of optical trap to assure that all incident light is absorbed in one or more detector elements. Several of these detectors are shown above.