THz Diffractive Optical Elements

Download THz Diffractive Optical Elements Datasheet (PDF, 119 KB)

Beam handling is required in  many THz applications. Currently it is carried out by parabolic mirrors and refractive optics.  However diffractive optics opens up new, basically different opportunities of beam handling since it allows realizing spatial transformation of THz beam.

To satisfy needs in diffractive optics for THz range we have developed calculation methods and manufacturing technology of the following diffractive optical elements (DOE):

  • THz Fresnel Lenses

THz Fresnel lenses
  • THz Beam Dividers

THz beam divider
Commom Specification: 


  Parameters
  Type of DOE
  THz Fresnel lens 
  THz beam divider
  Material   HRFZ-Si   HRFZ-Si
  Mechanical diameter, mm   to 55   to 55
  Optical diameter, mm   to 50   to 50
  Thickness, mm   1   1
  Operating wavelength range, µm   60-250   60-250
  Diffraction efficiency*, %   40   80
  Coating   two-side antireflection   two-side antireflection
*Diffraction efficiency is the ratio of the diffracted light intensity, of a given order, to the incident light intensity.

Developed DOEs have two-level relief. Currently we are working at  technology of DOE manufacturing with four- and eight-level relief. Multilevel relief will increase diffraction efficiency up to 96%.

THz Fresnel Lenses
Fresnel lens is the simplest diffractive element for focusing monochromatic beam.  It has no spherical aberrations in comparison with refractive lenses.
There are two focal lengths of diffractive lens: the main one and the secondary one. Diffraction efficiency of the main focus I1/I is 40% and of the secondary one I2/I is <3.6% that has been confirmed experimentally**. Optical characteristics have been investigated using free electron laser, radiation has been detected by  matrix microbolometer.
It's possible to produce the lenses with focal length from 100 mm and more. Focal length tolerance is 5%.
Dimension of Airy disk can be calculated using the following equation: X=1.22*λ*F/D, where  λ - operating wavelength, F -    focal length, and  D -  optical diameter.

THz_Frensel_lens

THz Beam Dividers
Beam divider transforms incident beam into spatially spaced several beams with specified power distribution.
Diffraction efficiency of the operating orders (+1 and -1) is 40(+/-2)% and of other orders  <5%. Value of the angle between operating beams can be from 20deg to 80deg.

ТГц делитель луча

Diffractive optical elements are manufactured upon request.

For quotation and delivery please fill in our request form.

__________________________

** B. A. Knyazev, Yu. Yu. Choporova, V. V. Gerasimov, M. G. Vlasenko, V. S. Pavelyev, B. O. Volodkin , A. N. Agafonov , K. N. Tukmakov,  A. K. Kaveev , G. I. Kropotov , E. V. Tsygankova , M. F. Stupak , I. G. Palchikova, Study of Diffractive Optical Elements Using High-Power Radiation of Novosibirsk Terahertz Free Electron Laser, Proceedings of  IRMMW-THz 2012