Holographic focusing elements implemented on the basis of the bearing polymer film with the thickness several times smaller than the operating wavelengthrepresent an advantageous alternative to classic lenses and focusing mirrors due to minor weight and size parameters, simple production technology and significant focusing capacities. While being in some way an analogue of phase diffraction optical elements on the basis of structures with a changable surface profile, such focusing elements are merely flat, for which the required phase variation along the surface is ensured by corresponding change of the topology of metal-coated micropattern subwave cells. Correct choice of the micropattern allows to focus the radiation beam in an area of arbitrarily complex shape.
Such focusing elements can be used in any quazi-optical systems of millimeter/submillimeter frequency range for example for even focusing of incident radiation in receiving openings of several detectors simultaneously.
All optical elements are produced on the basis of multi-layered frequency-selective surfaces - thin planar metal-coated microstructures with cells of special geometric shape, the topology of which defines the frequency properties of the element. Frequency-selective surfaces are resonant electrodynamic structures operated in the mode, in which the resonance frequency is below the point of excitation of high-order diffraction harmonics. This approach allows to create optical elements with unique properties unachievable or hard-hitting within the frames of traditional optics.
|Central frequency of focusing||0.05 to 0.7 THz|
|Diffractive efficiency (for reflective elements)||80 to 95%|
|Relative width of the band||20 %|
|Focal lenght||от 40 до 300 мм|
|Beam aperture diameter||30 to 70 mm|
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