2/26/2023 0 Comments Thermacam Researcher Serial NumberTransmission properties such as attenuation characteristics, modal transmission and the influence of launch conditions of hollow silica waveguides are of interest. HSW gas cells are particularly advantageous in applications where only small volumes are available and/or where fast response times are required. This has increased rapidly in recent years since the advent of quantum cascade lasers (QCLs), which also have operating wavelengths within this region. The spectral correspondence of HSW with the region of the electromagnetic spectrum associated with the strongest absorptions of many atmospheric gas species, known as the ‘molecular fingerprint region’, means that there has been significant interest in them for use as spectroscopic gas cells. 1 with radial thickness values of waveguides supplied by Polymicro Technologies TM. A schematic showing the construction of a typical HSW is shown in Fig. The total thickness of the silver/silver halide coating is usually around 1 μm, with the halide layer ranging from 20 to 80 % of this. This improves reflectivity by more than an order of magnitude, depending on the wavelength and the thickness of the halide layer. They are coated internally with a layer of silver which is then exposed to a halogen, which converts the silver surface to a silver halide. Hollow silica waveguides (HSWs) consist of a silica tube with bore diameters ranging from about 250 μm up to around 1000 μm. The research was driven in part by the need to guide high-power beams from CO 2 lasers operating at a wavelength of 10.6 μm for high precision cutting applications. Hollow waveguides were developed in the 1970s for transmitting infrared radiation at a time when researchers were keen to develop alternatives to chalcogenide-based IR fibres, which exhibit high losses and are brittle. Assessment of mode population is made by investigating the spatial frequency content of images recorded at the waveguide output using Fourier transform techniques. The results show that quasi-single-mode transmission is achievable under certain conditions although guided single-mode transmission in coiled waveguides requires a smaller bore diameter-to-wavelength ratio than is currently available. The thermal imaging camera allowed for more detailed images than could be obtained with a conventionally used beam profiler. Experimental verification of theoretical predictions is achieved using a thermal imaging camera to monitor output intensity distributions from waveguides under a range of conditions. We show that the bore diameter, coiling and launch conditions have an impact on the number of supported modes in the waveguide. In this paper, the transmission characteristics of hollow silica waveguides with bore diameters of 3 μm are investigated using a 7.8-μm quantum cascade laser system.
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