Refractive element

Several years ago the concept of near-surface imaging was introduced(l,2). The critical step that imparts the etch selectivity by introduction of refractive elements is termed gas-phase functionalization and involves the selective reaction... 

Solid-state conductivity (chemiresistance) sensors Dielectrometric sensors Dielectric sensors Absorptivity elements Index of refraction elements... 

Another approach that has been adopted in the IC industry for mitigating the effects of aberration, particularly chromatic aberration, is line narrowing of the incident radiation. The basis of this approach derives from the realization that an illumination radiation with extremely narrow spectral bandwidth is associated with very low chromatic aberration, obviating the need for color correction of the refractive elements associated with such a system. The required degree of spectral purity increases with increasing NA. For instance, KrF (248-nm) exposure systems with NA 0.7 require spectral bandwidth on the order of a picometer... 

The same group has also presented an alternative way to couple acoustic energy into a microfluidic chip using a flat transducer and a refractive element placed on top of the chip. This setup is used in combination with dielectrophoretic (DEP) forces with an outlook to combined manipulation of bioparticles or individual cells using the two forces simultaneously. 

Common to refractive elements in both wavelength ranges is the problem of chromatic aberration. Therefore, mirror optics is usually applied in particular in the mid-lR. Reflecting coatings applied to a surface for operation in the visible and near-infrared ranges can be silver, aluminum, chromium. 

A successM variant of this principle where the OPD is introduced by rotating a refractive element has been designed by Mold and Tlimer of PerkinElmer Ltd. [24,25]. When tested in comparison with several other tilt-compensated interferometers, this instrument had better resistance to the effects of tilt and shear than that of any other instrument tested. For example, the modulation efficiency of this interferometer in the near infrared did not change by more than 0.1% when the temperature was changed by more than 5°C [26]. This instrument has one fairly important disadvantage, however, in that it is far more expensive instrument to build than competitive designs and has not been introduced commercially. 

Over the next one hundred years the essential nature of IR radiation was slowly established, electrical methods of measurement were developed and a number of materials such as rock salt were found to be largely transparent to it and thus useful as refracting elements. Interest was mainly directed to the physics of the subject, with little attention given to any possibilities for application to chemistry. 

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