Category : Optics (components, coatings, instruments and systems) > Optical instrumentation, systems and accessories

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"Polariser is a very useful component in material analysis from the UV-Visible to the far infrared. Molecules that change their dipole moment during their molecular vibration can absorb electromagnetic radiation. The electric moment (transition moment) caused by the vibration is a vector quantity that will only interact with electromagnetic radiation component acting in the same direction. No change in absorbance spectrum is observed when polarised radiation interacts with substances with random molecules such as gases, liquids or amorphous solids. This is because these molecules do not show any preferred orientation of transition moment. The same is true in the opposite sense if single crystals, oriented poly-crystalline or polymer materials interact with non-polarised light.

Differences in absorbance spectrum occur only when oriented samples are analysed with plane polarised light. Important information such as crystal structure, material type and dichroism, among others, can be deduced.

Applications of polarisers include beam splitters and beam attenuators, coupling devices in mid-ir and long wavelength lasers. They are also used in microscopy, plasma diagnostics, thermal imaging systems, navigation control systems, astronomy, and analysis of materials such as polymers and semiconductors.

Light can be polarised in a variety of ways. These include birefringent materials such as calcite, wiregrid (free standing or deposited on transmitting substrate), dielectric coated plates, Brewster angle plates or stretched polymer thin films.

Wire-grid polarisers
A fine array of parallel conducting wires whose period is smaller compared to the wavelength of incident radiation will transmit one polarisation and reflect the other. The component of the radiation whose electric vector is perpendicular to the direction of the wires and induces current in the wires will be transmitted and the parallel vector reflected. Medway Optics' polarisers are produced by holographic method (i.e. laser interferometry) or mechanically ruled. These polarisers do not suffer from beam displacement, are not affected by diverging or converging beam, have wide acceptance angle without degradation of performance and portable."

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