Optical fibre sapphire

Alternatively, it is possible to install fibre optic probes directly in the main stream in-line while the IR spectrophotometer remains remotely in a low vibration laboratory environment. In-line analysers, which do not remove any sample from the line, have the minimum possible lag time and do not change the sample physically or chemically from its nature in the process. Recently, bundles of 500 /xm optic fibres have been developed for the 5000-900 cm (2000-11,000 nm region), which permit transmission of IR energy over distances of several metres. Lowry et al. [76] have evaluated fibre-optic cables that might prove useful in FTIR remote sampling applications. The various optical fibres (chalcogenide, silver halide, heavy metal fluoride or sapphire) differ in their spectral window [77]. Due to the thermal stability and the spectral window, sapphire fibres are considered suitable for in-line characterisation of polymer melts in a production line (e.g. in an extruder head) as an alternative to discontinu-ously operating conventional off-line transmission IR spectroscopy of polymer films [78]. 

Spherical ball lenses have been used as collimators in fibre optic connectors. Sapphire spheres with a high refractive power are industrially produced in a wide range of diameters (Sandoz SA, Cugy, Switzerland Rubis Precis, Charquemont, France). Light emitted from a fibre can be focused with this lens type onto the sample site (Figure 12A). Rol found a maximal performance when the ratio of the back surface distance to the fibre and the radius of the... 

More recently a new technique has started to be implemented, involving the use of optical fibre thermometry This Involves the use of a single crystal sapphire rod coated at its tip with a thin film of a precious metal... 

Our experimental setup of the 2D-CARS microscope is shown in Fig. 5.4h [32], The 70-fs output from the Ti sapphire oscillator was split into two beams. One of the beams was introduced into a photonic crystal fiber (Crystal Fibre, Femtowhite 800) to generate a coherent supercontinuum. Then, the continuum was conditioned with an 800 nm long-pass filter. The other beam was spectrally narrowed by the custom-made laser line filter (Optical Coatings Japan, Av = 14 cm FWHM). The obtained two beams were introduced collinearly into the microscope objective lens. The chirping of the broadband pump beam was carefully avoided so that the CARS signals are obtained in a wide spectral region. The broadband CARS emission in back-reflected direction was analyzed by the CCD spectrometer. 

Figure 3.44. A fibre-optic probe with air cooling and a sapphire window suitable for use in a reactive extruder or other rugged environment. After Hansen and Khettry (1994).

Figure 9.17 The principle of a spectrophotometer fitted with an immersion probe. Monochromatic light issuing from a spectrophotometer is guided towards an immersion cell and then returned to the detector. The route is confined by a fibre optic. Left transmission probe. Right ATR probe the sapphire prism has a refraction index greater than that of the solution. The schematic shows three reflections of the beam and its penetration into the solution (see explanation in Chapter 10, Section 10.9.3).

An instrument for optical biopsy of bones based on a diode laser and a single TCSPC channel is described in [151, 152]. Other instruments use a tuneable synchronously pumped dye laser and a Ti Sapphire laser [414]. The lasers are switched into a single source fibre by a fibre switch. A single TCSPC channel records the diffusely reflected light and a reference signal split off from the source fibre. 

Fig. 3. Composite loss spectra for some common IR fibre optics ZBLAN fluoride glass SC sapphire, chalcogenide glass, PC AgBrCl, and hollow glass waveguide plot reproduced from Harrington, 2010.

The determination of the composition of ethylene-propylene copolymers at a temp, of200C by means of an IR fibre-optic sensor based on sapphire fibres was studied. LDPE and PP were also investigated. Data are presented on spectra of LDPE and PP at 200C obtained using the sensor, CH3/CH2 ratio after curve fitting versus C2 content, ratio of absorbance at 2950 and 2852/cm versus C2 content and calibration graph of multivariate calibration. 31 refs. 

IR process control systems have also been used to determine the chemical composition of copolymers and polymer blends (PP/PE, PC/PBT/PET, PC/ABS, EVA) and to control PET, PA6 and EPDM polymerisation processes (end-group determination, etc.) [70, 92]. Partial least squares (PLS) analysis of ATR-FTIR absorbance spectra has provided an accurate, precise, rapid and cost effective method both for off-line and on-line compositional analysis at production sites of EO/FO copolymers in the range of 0-10 wt.% co-polymerised ethylene sites [104]. Proper examination of the statistics underlying the PLS model is essential in providing a robust calibration model. Gotz et al. [80] showed that the composition of ethylene/propylene copolymers could be determined at 200°C by means of an IR sapphire fibre-optic sensor. Similarly, monomer residuals and additives in polymer melts may be determined. 

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