Imprinted diffractive optics for terahertz radiation

Abstract

Terahertz diffractive optic elements have been fabricated in polypropylene by imprinting with a silicon master. A silicon master is created with eight phase levels for high diffraction efficiency and etched using inductively coupled plasma reactive ion etching. This technique enables the rapid replication of complex optical structures in a high transmission material. Excellent replication of multilevel high efficiency Fresnel lenses is shown. The resulting lenses were tested with a 2 THz quantum cascade laser. The signal strength at the focus was 70 times the base signal strength.

Tutorial: Terahertz beamforming, from concepts to realizations

“…In another work, the negative shape of a stepped-lens structure was etched into silicon, and this was used in a stamp-like manner to imprint a stepped-phase focusing structure into a commonly used terahertz transparent polymer known as polypropylene. 101 This material has lower refractive index than silicon and hence exhibits better matching to free-space at the cost of increased physical thickness. This resulted in a device that was 3 mm thick.…”

Optically controlled terahertz beam steering and imaging

“…Particularly, the use of lasers and components designed for the telecom wavelengths around 1.5 μm are promising for inexpensive and compact THz spectrometers [8]. Avenues to produce low-cost THz optics are also being explored [9,10].…”

Terahertz beam focusing based on plasmonic waveguide scattering

“…1,2 Recently, several attempts have been reported to fabricate thin THz lenses based on Fresnel zone plates or using metamaterials. [3][4][5][6] Even though the thickness of each lens could thus be reduced, the entire THz system remains bulky as long as the system relies on free-space propagation paths between the lenses.…”