Abstract
Nonlinear spectroscopic investigation in the terahertz (THz) range requires significant field strength of the light fields. It is still a challenge to obtain the required field strengths in free space from table-top laser systems at sufficiently high repetition rates to enable quantitative nonlinear spectroscopy. It is well known that local enhancement of the THz field can be obtained for instance in narrow apertures in metallic films. Here we show by simulation, analytical modelling and experiment that the achievable field enhancement in a two-dimensional array of slits with micrometer dimensions in a metallic film can be increased by at least 60% compared to the enhancement in an isolated slit. The additional enhancement is obtained by optimized plasmonic coupling between the lattice modes and the resonance of the individual slits. Our results indicate a viable route to sensitive schemes for THz spectroscopy with slit arrays manufactured by standard UV photolithography, with local field strengths in the multi-ten-MV/cm range at kHz repetition rates, and tens of kV/cm at oscillator repetition rates.
Highlights
Lattice modes in a periodic array of resonant structures can couple to the resonance of the structures itself[19,20]
We demonstrate how rectangular slit apertures with transmission resonance frequencies in the low THz range, arranged periodically in a metallic film, can be designed so that the lattice modes constructively interfere with the slit resonance leading to a field enhancement inside the slit which is up to 60% larger than of an isolated slit of the same dimensions
We have investigated the influence on the coupling between the resonance of micro-slits in a metallic film, arranged in a periodic array so that energy can be coupled to lattice modes of the array
Summary
EOT occurs when the impedance is matched through a resonant aperture[29,30]. The resonant length of a half-wavelength dipole antenna is defined as the length where the reactance (imaginary part of the impedance Zin =Rin +iXin) is zero. In a periodic array of holes in a thin metal film the transmission is influenced by coupling between the field transmitted through the individual apertures and SPP-mediated lattice modes. In this situation, EOT can be observed both at the slit aperture resonance and at the additional lattice mode resonances[23]. Because of the higher refractive index, the frequency-dependent transmission of the field will be mainly influenced by the SPP waves on the metal-substrate interface. SPP modes along the metal interface can interfere constructively with the enhanced field in the neighboring apertures. This offers the possibility of additional field enhancement in the apertures of the array and to further increase of the extraordinary transmission through the array[19] compared to that in an isolated aperture where the SPP-coupled energy is lost
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
