title: Amplification of resonant field enhancement by plasmonic lattice coupling in metallic slit arrays.
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.
authors.affiliation: DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Pernille
authors.initials: P
authors.lastname: Klarskov
authors.affiliation: DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Abebe T
authors.initials: AT
authors.lastname: Tarekegne
authors.affiliation: DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Iwaszczuk
authors.affiliation: Institute of Optics, University of Rochester, Rochester, NY 14627-0186, United States of America.
authors.forename: X-C
authors.initials: XC
authors.lastname: Zhang
authors.affiliation: DTU Fotonik - Department of Photonics Engineering, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
authors.forename: Peter Uhd
authors.initials: PU
authors.lastname: Jepsen