Understand the spectral characteristics of a laser detector

This technical note explains how to understand the spectral characteristics of a Gentec-EO detector. In this text, you will find, among others, a clear definition for calibrated spectral range, range of available wavelengths and spectral range.


Calibrated Spectral Range
(contained in the range of available wavelengths)

The calibrated spectral range is the range of wavelengths that is NIST or NRC traceable and to which a calibration uncertainty (%) is specified. Absolute measurement is thus possible ONLY in that range. Wavelengths outside this range are NOT calibrated and thus it is no tpossible to specify a calibration uncertainty. However, the spectral response of most absorbers (MB, H) is very flat from 2 μm to 20 μm.

Range of Available Wavelengths In Monitor
(contained in spectral range)

The range of available wavelengths contains the wavelengths that one can select in his monitor prior to a measurement. Generally, a traceable calibrated sensitivity saved in the EEPROM of the detector is applied for each of them. There are three exceptions to this rule. The first exception is the CO2 (10.6 μm) wavelength. It can be calibrated upon request. If a detector is not calibrated at this wavelength, a typical value is provided. The second exception is below 248 nm. For historical reasons, these wavelengths are still available in a monitor and are still present in the PWC (Personal Wavelength Correction Certificate), but are not traceable anymore. The third exception is above 2.5 μm. For these wavelengths, a typical sensitivity is used but it is not traceable.



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