Diffuse reflecting material for integrating cavity spectroscopy, including ring-down spectroscopy

Abstract

We report the development of a diffuse reflecting material with measured reflectivity values as high as 0.99919 at 532 nm and 0.99686 at 266 nm. This material is a high-purity fumed silica, or quartz powder, with particle sizes on the order of 40 nm. We demonstrate that this material can be used to produce surfaces with nearly Lambertian behavior, which in turn can be used to form the inner walls of high-reflectivity integrating cavities. Light reflecting off such a surface penetrates into the material. This means there will be an effective "wall time" for each reflection off the walls in an integrating cavity. We measure this wall time and show that it can be on the order of several picoseconds. Finally, we introduce a technique for absorption spectroscopy in an integrating cavity based on cavity ring-down spectroscopy. We call this technique integrating cavity ring-down spectroscopy.

Integrating cavity based gas cells: a multibeam compensation scheme for pathlength variation

“…For measurements with a photodetector, the total exit flux at the photodetector, Φ d is defined as [16]:…”

“…Furthermore to carry out inspection for potential pathlength changes, the sensor has to be removed from its location for cleaning and drying. Another approach worth noting is measurement of the temporal decay in a pulsed system [16]. Here the stability of measurement of the decay constant (101 ± 1ns) was demonstrated for a cylindrical diffuse cavity (5.72cm height and diameter).This technique, though it provides immunity to intensity fluctuations, requires high bandwidth (GHz) electronics which can limit the attainable precision.…”

The Dawn of Quantum Biophotonics

“…A new material has now been developed that has a diffuse reflectivity up to 99.92 % [43]; this is sufficient to make ICRDS a reality. It opens up a plethora of exciting new applications with tremendous impact in, for example, the biomedical area where highly accurate absorption spectra of living cells, tissue samples, liquids, etc., can now be obtained, even when the absorption is very weak compared to scattering in the sample.…”

Enhanced optical coupling and Raman scattering via microscopic interface engineering

“…Some of these techniques include stimulated Raman scattering, 10,11 coherent anti-Stokes Raman scattering, 8,12 and surface enhanced Raman scattering. 13 Other methods use integrating cavities 14,15 to increase the interaction time and region of the laser light within the sample, thereby enhancing signal and sensitivity.…”

“…35,36 The elastic scattering of light can be used to increase the optical path length, and interaction time, of light with molecules within a material. 37,38 For instance, using highly scattering materials as the walls of an integrating cavity 15 has lead to more sensitive detection of fluorescent markers in fluids. 14 Furthermore, adding small amounts of scattering materials to a transparent fluid has also shown some degree of a)…”