Adiabatic compression of terahertz waves using metal flares

Abstract

Coupling into tapered metal parallel plate waveguides using a focused terahertz beam Appl. Phys. Lett. 101, 041109 (2012) Sub-terahertz spectroscopic system using a continuous-wave broad-area laser diode and a spatial filter

High Resolution Waveguide Terahertz Time-Domain Spectroscopy

“…In this wavelength range the geometry would be comparable to a horn antenna. Machined tapers [68] or metal flares [20] are used. The latter ones even offer a superior coupling ratio compared to the silicon lens optics and were already applied for high-resolution spectroscopy of polycrystalline molecular films [44].…”

“…A potential solution is to use waveguide geometries which define and guide the beam of sub-ps THz pulses. Here the design of the waveguide can be optimized to control specific properties such as coupling efficiency [18], propagation losses [19], dispersion [20] and modal profile [21]. Even focusing waveguides can be designed [22] to confine THz radiation to well below the diffraction limit [23,24].…”

Highly sensitive terahertz measurement of layer thickness using a two-cylinder waveguide sensor

“…Waveguide geometries based on slowly varying metal surfaces have recently attracted interest in the THz range. [8][9][10][11][12][13] Using these results, we propose and demonstrate improved thin film sensing of plastic coatings.…”

“…This approach combines our previous work on THz wave compression using metal flares 12 and the sensing capabilities of THz surface waveguides. 13 The experimental layout, schematically shown in Fig.…”

Flare coupled metal parallel-plate waveguides for high resolution terahertz time-domain spectroscopy

“…As we have shown recently, curved flares made out of metal shim can be efficiently used to couple THz radiation. 13 In the quasioptical approach, the metal surfaces would just reflect the THz waves. But, if the changes in the beam extent are introduced adiabatically, 14 which denotes slowly with respect to the wavelength, the reflection losses can be minimized and propagation in the forward direction is maintained.…”