Abstract-Compact and ultra-efficient broadband plasmonic terahertz field detector

Yannick Salamin, Ileana-Cristina Benea-Chelmus, Yuriy Fedoryshyn, Wolfgang Heni, Delwin L. Elder, Larry R. Dalton, Jérôme Faist,  Juerg Leuthold

https://www.nature.com/articles/s41467-019-13490-x

Terahertz sources and detectors have enabled numerous new applications from medical to communications. Yet, most efficient terahertz detection schemes rely on complex free-space optics and typically require high-power lasers as local oscillators. Here, we demonstrate a fiber-coupled, monolithic plasmonic terahertz field detector on a silicon-photonics platform featuring a detection bandwidth of 2.5 THz with a 65 dB dynamical range. The terahertz wave is measured through its nonlinear mixing with an optical probe pulse with an average power of only 63 nW. The high efficiency of the scheme relies on the extreme confinement of the terahertz field to a small volume of 10−8(λTHz/2)3. Additionally, on-chip guided plasmonic probe beams sample the terahertz signal efficiently in this volume. The approach results in an extremely short interaction length of only 5 μm, which eliminates the need for phase matching and shows the highest conversion efficiency per unit length up to date.

Abstract-Intensity autocorrelation measurements of frequency combs in the terahertz range

Ileana-Cristina Benea-Chelmus, Markus Rösch, Giacomo Scalari, Mattias Beck, and Jérôme Faist

https://journals.aps.org/pra/abstract/10.1103/PhysRevA.96.033821

We report on direct measurements of the emission character of quantum cascade laser based frequency combs, using intensity autocorrelation. Our implementation is based on fast electro-optic sampling, with a detection spectral bandwidth matching the emission bandwidth of the comb laser, around 2.5 THz. We find the output of these frequency combs to be continuous even in the locked regime, but accompanied by a strong intensity modulation. Moreover, with our record temporal resolution of only few hundreds of femtoseconds, we can resolve correlated intensity modulation occurring on time scales as short as the gain recovery time, about 4 ps. By direct comparison with pulsed terahertz light originating from a photoconductive emitter, we demonstrate the peculiar emission pattern of these lasers. The measurement technique is self-referenced and ultrafast, and requires no reconstruction. It will be of significant importance in future measurements of ultrashort pulses from quantum cascade lasers.

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Abstract-SUB-CYCLE MEASUREMENT OF INTENSITY CORRELATIONS IN THE TERAHERTZ RANGE

Ileana-Cristina Benea-Chelmus, Giacomo Scalari, Mattias Beck, Jerome Faist

http://www.mathpubs.com/detail/1512.02198v1/Sub-cycle-measurement-of-intensity-correlations-in-the-Terahertz-range

The Terahertz frequency range bears intriguing opportunities, beyond very advanced applications in spectroscopy and matter control. Peculiar quantum phenomena are predicted to lead to light emission by non-trivial mechanisms. Typically, such emission mechanisms are unraveled by temporal correlation measurements of photon arrival times, as demonstrated in their pioneering work by Hanbury Brown and Twiss. So far, the Terahertz range misses an experimental implementation of such technique with very good temporal properties and high sensitivity. In this paper, we propose a room-temperature scheme to measure photon correlations at THz frequencies based on electro-optic sampling. The temporal resolution of 146 fs is faster than one cycle of oscillation and the sensitivity is so far limited to ~1500 photons. With this technique, we measure the photon statistics of a THz quantum cascade laser. The proposed measurement scheme allows, in principle, the measurement of ultrahigh bandwidth photons and paves the way towards THz quantum optics.