Proposal for an integrated silicon-photonics terahertz gas detector using photoacoustics

A design and multiphysical model is presented for an on-chip gas sensor that transduces terahertz gas absorption through sound generation into a mechanical motion that can be read out externally. The signal is triply enhanced by designing a structure that functions simultaneously as an optical, an acoustical and a mechanical resonator. The structure is made in high-resistivity silicon and can be fabricated using CMOS and HEMS fabrication technologies. The sensor is a purely passive element, so an external THz source and read-out are required. The chip has a footprint of 3 mm(2). A detection limit of 234 ppb of methanol for a source power of 1 mW and an integration time of 1 ms is predicted. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreemen

Sub-THz Characterisation of Monolayer Graphene

We explore the optical and electrical characteristics of monolayer graphene by using pulsed optoelectronic terahertz time-domain spectroscopy in the frequency range of 325-500 GHz based on fast direct measurements of phase and amplitude. We also show that these parameters can, however, be measured with higher resolution using a free space continuous wave measurement technique associated with a vector network analyzer that offers a good dynamic range. All the scattering parameters (both magnitude and phase) are measured simultaneously. The Nicholson-Ross-Weir method is implemented to extract the monolayer graphene parameters at the aforementioned frequency range

Growth of individual carbon nanotubes on an array of TiN/Ni nanodots patterned by e-beam lithography and defined by dry etching for field emission application

In this paper, we demonstrate a new technique to realize TiN/Ni nanodots array on silicon substrate using e-beam lithography and dry etching techniques. After patterning the Ni nanodisk (7 nm thick, 150 nm in diameter) at perfectly controlled location, individual vertically aligned carbon nanotubes (VACNTs) were grown using plasma-enhanced chemical-vapor deposition (PECVD). In addition, a field emission cathode (1 mm diameter circular emission area) based on a hexagonal array (20μm spacing) of individual VACNTs delivered a high emission current of 4.23 mA for an applied electric field of 22.5V/μm

Low-loss, 1-m long length, hollow-core THz waveguide operating at 1 THz, based on anti-resonant guiding mechanism

International audienceA hollow-core THz waveguide composed of 10 silica capillaries is designed and fabricated. The waveguide based on the anti-resonant guiding mechanism presents a large transmission window (∼>600 GHz) centered at 1 THz, with measured propagation losses below 0.5 dB/m

A 285 GHz sub-harmonic injection locked oscillator in 65nm CMOS technology

A 285 GHz Sub Harmonic Injection Locked Oscillator (SHILO) is presented using a standard 65nm CMOS process. The architecture of this oscillator is based on the differential LC tank with push-push but adapted to obtain a third harmonic oscillation. The output power is -19 dBm at 285 GHz for a dc power of 70 mW. This oscillator offers a measured phase noise of -96.3 dBc/Hz at 10 MHz and -80.5 dBc/Hz at 1 MHz, and a tuning range from 284.2 GHz to 289 GHz. The SHILO can be locked all along the tuning range with an injection signal corresponding to one sixth of the output frequency. The chip size is 921x451 μm2

THz pulses on planar Goubau lines : transmitting, reflecting and coupling topologies

International audienc

Nonequilibrium plasmons in optically excited semiconductors

International audienceAn analysis of the nonequilibrium plasmon spectrum of optically excited semiconductors is presented. It is shown that semiconductors with preexisting carrier populations, due, e.g., to a prepump or doping, may exhibit a rich collective excitation spectrum including additional plasmon modes. If these modes are weakly damped they give rise to an essential acceleration of thermalization processes. It is found that the most favorable conditions for this effect to appear are low temperature and p doping. These theoretical predictions are fully confirmed by results of comprehensive pump-probe experiments on bulk GaAs in the presence of a prepump and in doped samples. Cop. 2000 The American Physical Societ