Improved Spectral Responsivity Scales at the NPL, 400 nm to 20 μm

Abstract

Two spectral responsivity scales have been established at the National Physical Laboratory, UK. High quantum efficiency silicon photodiodes have been used to establish a continuous spectral responsivity scale for the spectral region 400 nm to 920 nm. The scale can be disseminated by the NPL with an uncertainty of f 0 , l YO. Pyroelectric detectors fitted with a reflecting hemispherical cavity have been used to establish a spectral responsivity scale for the spectral region 1 pm to 20 pm. This scale has an uncertainty of less than f l,6 YO.

Development and evaluation of a novel large-area single-pixel QWIP for infrared radiometry

“…For fundamental optical measurement applications (for example, spectral responsivity standards [5]) it is normal (and sufficient) to use a single element detector, the expense and complication of using imaging arrays is therefore not required. Some QWIPs are made from layers of GaAs/Al x Ga 1-x As material which can be mass grown on large substrate wafers.…”

Establishing a high-accuracy spectral response scale in the near infrared with digital filters

“…A description of a calibration procedure for infrared standard detectors based on a relative calibration to a spectrally invariant thermal detector and then absolute calibration at a few wavelengths is given by several groups. [2][3][4] As pointed out in Refs. 2-4, the disadvantage of the thermal detectors is their signal-to-noise ratio when they are used in a narrow-bandwidth double-monochromator setup at room temperature, which limits the accuracy achievable by this method.…”

“…The relative spectral response of the InGaAs detectors was measured with the CPD purchased from National Physical Laboratory, UK, as a spectrally invariant detector. 2 This detector has an active element with a platinum black coating inside an aluminum reflective hemisphere. The CPD needs a preamplifier, a chopper, and a lock-in amplifier to give a dc-equivalent signal.…”

A comparison of the performance of a photovoltaic HgCdTe detector with that of large area single pixel QWIPs for infrared radiometric applications

“…QWIPs [4] are now well established for use in state-of-the-art cooled thermal imaging systems. For fundamental optical measurement applications, for example infrared spectral responsivity standards [5], it is normal (and sufficient) to use a single element detector [1]. Some QWIPs are made from layers of GaAs/Al x Ga 1Àx As which can be mass grown on large substrate wafers.…”