arXiv subjects

G. Ducournau

Publications and source records attributed to G. Ducournau.

4 recordsLinked to original sources

arXiv2026

Circuit-Level Design, Modeling, and On-Wafer Characterization of a Coplanar THz Optoelectronic Mixer

We report the design, modeling, and on-wafer characterization of a photoconductive heterodyne mixer implemented as a true terahertz monolithic integrated circuit (TMIC). Unlike previous photoconductive heterodyne demonstrations, the proposed circuit is characterized using RF integrated circuit metrics including input return loss, RF/IF isolation, broadband impedance matching, and conversion loss. The mixer combines a microcavity photoconductor with a broadband coplanar matching network incorporating a Ti shunt resistor, an RF DC-blocking MIM capacitor, and an RF/IF decoupling capacitor. A circuit-level model including both the photoconductor and the distributed CPW accesses is developed and validated. The passive circuit is experimentally characterized up to 500 GHz using on-wafer VNA measurements and accurately reproduced by simulation. Under illumination, the model predicts an input reflection coefficient below -10 dB up to 215 GHz and better than -6.5 dB up to 500 GHz. Measured and simulated conversion losses agree within +/-1 dB over the entire 1-500 GHz range. Conversion loss varies from 22.5-25.5 dB below 320 GHz and 26-34 dB up to 500 GHz. The proposed TMIC demonstrates broadband operation and provides a validated circuit design methodology for future integrated THz photonic mixers.

physics.app-ph↗

arXiv2025

Room-temperature, continuous-wave Terahertz generation in free-space with an intersubband mid-infrared photomixer

We demonstrate a Terahertz photomixer pumped by mid-infrared photons at 10$\mu$m wavelength. The device is based on a dual-antenna architecture, in which a two-dimensional array of mid-infrared patch-antenna resonators is connected to the electrodes of a log-spiral Terahertz antenna. By exploiting intersubband absorption inside an AlGaAs-GaAs multi-quantum-well heterostructure, a photocurrent is coherently generated at the difference frequency between two quantum cascade lasers. The photocurrent drives the antenna electrodes allowing tunable, continuous-wave generation in free-space up to 1 Terahertz at room temperature. By experimentally studying the photomixer frequency response and dark impedance, we demonstrate that the observed power roll-off at high-frequency is limited by the combined effect of the photoexcited carrier's intrinsic lifetime and of the device $RC$ time constant. In the spectral range investigated we obtain, in continuous-wave, mid-infrared $\rightarrow$ Terahertz conversion efficiencies exceeding by orders of magnitude those of unipolar devices exploiting $\chi^{(2)}$ processes.

physics.optics↗

arXiv2022

SOI-based micro-mechanical terahertz detector operating at room-temperature

We present a micro-mechanical terahertz (THz) detector fabricated on a silicon on insulator (SOI) substrate and operating at room-temperature. The device is based on a U-shaped cantilever of micrometric size, on top of which two aluminum half-wave dipole antennas are deposited. This produces an absorption extending over the $\sim 2-3.5$THz frequency range. Due to the different thermal expansion coefficients of silicon and aluminum, the absorbed radiation induces a deformation of the cantilever, which is read out optically using a $1.5μ$m laser diode. By illuminating the detector with an amplitude modulated, 2.5 THz quantum cascade laser, we obtain, at room-temperature and atmospheric pressure, a responsivity of $\sim 1.5 \times 10^{8}$pm/W for the fundamental mechanical bending mode of the cantilever. This yields an noise-equivalent-power of 20 nW/Hz$^{1/2}$ at 2.5THz. Finally, the low mechanical quality factor of the mode grants a broad frequency response of approximately 150kHz bandwidth, with a response time of $\sim 2.5μ$s.

physics.optics↗

arXiv2014

High density THz frequency comb produced by coherent synchrotron radiation

Frequency combs (FC) have radically changed the landscape of frequency metrology and high-resolution spectroscopy investigations extending tremendously the achievable resolution while increasing signal to noise ratio. Initially developed in the visible and near-IR spectral regions, the use of FC has been expanded to mid-IR, extreme ultra-violet and X-ray. Significant effort is presently dedicated to the generation of FC at THz frequencies. One solution based on converting a stabilized optical frequency comb using a photoconductive terahertz emitter, remains hampered by the low available THz power. Another approach is based on active mode locked THz quantum-cascade-lasers providing intense FC over a relatively limited spectral extension. Alternatively, here we show that dense powerful THz FC is generated over one decade of frequency by coherent synchrotron radiation (CSR). In this mode, the entire ring behaves in a similar fashion to a THz resonator wherein electron bunches emit powerful THz pulses quasi-synchronously. This FC presents unprecedented spectral characteristics and opens new perspectives for metrology investigations.

physics.ins-det↗