Newport 1830-C - Section 4 - Performing Measurements; Introduction; Photodetector Considerations; 4.2.1 Detector Calibration and Accuracy

13
Section 4
Performing Measurements
4.1 Introduction
This section contains detailed information on how to make various optical
power measurements with the 1830-C.
4.2 Photodetector Considerations
This section describes detector and attenuator characteristics, optical and
electrical considerations, and environmental influences on optical measure-
ments. In general, the accuracy of measurement with the 1830-C is limited
by the calibration accuracy of the detector calibration. Making accurate
measurements of optical power is however, also dependent upon properly
setting up the 1830-C, controlling temperature and illumination conditions,
and understanding the factors that affect power measurement.
4.2.1 Detector Calibration and Accuracy
Newport Corporation calibrates its detectors using secondary standards
directly traceable to the United States National Institute of Science and
Technology (NIST). The details and accuracy of the calibration procedure
vary with each detector model but a detailed description of the calibration
results is supplied with each individually calibrated detector.
In general, detector calibration accuracy ranges from 2% to 7% in absolute
terms and varies with wavelength. Each detector will have some variation
in the response over different sections of its surface. Therefore, for the
most reproducible measurements, light should illuminate the detector as
uniformly as possible over 80% of the detector’s active area.
CAUTION
Avoid focusing a light source onto the detector surface.
Inaccurate readings and possible detector damage may result.
Consult your detector manual for information on detector
saturation or damage thresholds.
NIST traceability requires that detectors be re-calibrated on one year
intervals. As individual detector responses change with time, especially in
the ultraviolet spectral range, re-calibration is necessary to assure confi-
dence in the accuracy of the measurement. The same detector should
always be used for measurements which are to be directly compared, in
order to obtain reproducible results.