Abstract
We present an experimental comparison of photoacoustic responsivities of common highly absorbing carbon-based materials. The comparison was carried out with parameters relevant for photoacoustic power detectors and Fourier-transform infrared (FTIR) spectroscopy: we covered a broad wavelength range from the visible red to far infrared (633 nm to 25 μm) and the regime of low acoustic frequencies (< 1 kHz). The investigated materials include a candle soot-based coating, a black paint coating and two different carbon nanotube coatings. Of these, the low-cost soot absorber produced clearly the highest photoacoustic response over the entire measurement range.
Highlights
In addition to its many applications in spectroscopy [1,2,3,4] and im aging [5,6], the photoacoustic (PA) effect is useful for electromagnetic power detection due to its wavelength independency and high detection sensitivity
In order to cancel out instrumental effects, all measurements were compared against the best-performing absorber, which in our case turned out to be the one based on candle soot
Most of the tested absorbers – two carbon nanotube (CNT) absorbers and a Nextel-painted absorber – have nearly 100 % emissivities (Table 1) and look black when observed by naked eye
Summary
In addition to its many applications in spectroscopy [1,2,3,4] and im aging [5,6], the photoacoustic (PA) effect is useful for electromagnetic power detection due to its wavelength independency and high detection sensitivity. The broad and uniform spectral responsivity is important for general-purpose power detectors and from the metrological point of view: Traceable power measurements in the infrared and THz regions benefit from the possi bility of transferring the calibration to the visible wavelength region, where a more accurate responsivity scale is available [13] Another example of an application that requires an optically broadband absorber is Fourier Transform Infrared (FTIR) spectroscopy, where photoacoustic detection is often used due to its background free nature, broad wave length coverage and large dynamic range. As far as we know, comparisons of photoacoustic properties of absorber materials for conditions relevant in optical power detection and FTIR measurements are yet to be re ported The cantileverenhanced photoacoustic method has already led to some of the best detection sensitivities in photoacoustic trace-gas spectroscopy [3,4,21], and it has the potential to significantly advance optical power detector development as well
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