Optical Windows

Optical windows of highly purified magnesium fluoride which transmit light from the vacuum ultraviolet (140 nm) into the infrared (7) are recommended for use as ultraviolet optical components for use in space exploration. 

Liquids and solutions can be measured in special cells that have optical windows at right angles, or they can be contained in capillary tubes or small vials. The latter are... 

In the earliest SFG experiments [Tadjeddine, 2000 Guyot-Sionnest et al., 1987 Hunt et al., 1987 Zhu et al., 1987], a first-generation data acquisition method was used, and, because of the limited signal-to-noise ratios, IR attenuation by the electrolyte solution was a substantial handicap. So, in earlier SFG studies, as in IRAS studies, measurements were performed with the electrode pressed directly against the optical window [Baldelli et al., 1999 Dederichs et al., 2000]. With the in-contact geometry, the electrolyte was a thin film of uncertain and variable depth, probably of the order of 1 p.m. However, the thin nonuniform electrolyte layers can strongly distort the potential/coverage relationship and hinder the ability to study fast kinetics. 

The necessary thin-layer configuration was obtained by pressing the electrode against the optical window. Different cell constructions have been used. Fig. 1.6 shows a cell similar to one used by Seki et al. [32], The micrometer screw attached to the working electrode allows a reproducible adjustment of electrode-window distances. 

The IR microscopy sampling technique is the ultimate sampling technique since only one particle is required for analysis. Due to the restrictions of diffraction effects, typically, the particles of interest must be greater in size than 10 x 10 /xm. Once the sample of interest is placed upon an IR optical window,... 

The electrochemical cell used in our laboratory has been fully described elsewhere (5). The cell body is made of chemically inert Kel-F and the electrode is mounted on a piston so that its surface can be pushed to the optical window, to a spacing of the order of 1-3 microns, in order to minimize the signal from the bulk electrolyte. For Raman scattering spectroscopy the window is of flat fused quartz, and the exciting laser beam is incident at about 60°. The scattered light is collected off-normal, but the geometry is not critical for SERS due to the high sensitivity. Details on the SERS measurements in our laboratory have been reported previously (6,7). 

Figure 4 Graph of absorption coefficient versus wavelength of light. The optical window is denoted by the red box.

The term optical window denotes the spectral range where a low absorption by chro-mophores allow for significant penetration of light. 

Polymer currency with an inserted multilayer polymer optical window... 

Make optical window in polymer currency of an unusual shape... 

Insert an optical window with burnouts to change colors... 

Mistlberger G, Chojnacki P, Klimant I (2008) Magnetic sensor particles an optimized magnetic separator with an optical window. J Phys D Appl Phys 41 085003(1)-085003(9)... 

Figure 1.5. Noninvasive sensing of glucose. Within the optical window (650 nm-1300 nm), lifetime-based sensing by fluoresence is possible through the human skin.

Optics Issues relative to hygroscopic optics and the need to pay attention to mirror mounts relative to vibration and/or thermal effects have already been addressed. Zinc selenide is an important alternative material, especially when antireflection (AR) coated. If potassium bromide absolutely has to be used for its lower transmission range (down to 400 cm ) then a protective coating such as Parylene must be used. Most process analyzers use protective windows between the spectrometer and the sample interface. If used, back reflections from the window surfaces into the interferometer must be avoided because these will cause photometric errors. Such reflection can be eliminated by wedging or tilting the optical windows, relative to the beam path. 

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