Premium
Tunable, Grating‐Gated, Graphene‐On‐Polyimide Terahertz Modulators
Author(s) -
Di Gaspare Alessandra,
Pogna Eva Arianna Aurelia,
Salemi Luca,
Balci Osman,
Cadore Alisson Ronieri,
Shinde Sachin Maruti,
Li Lianhe,
Franco Cinzia,
Davies Alexander Giles,
Linfield Edmund Harold,
Ferrari Andrea Carlo,
Scamarcio Gaetano,
Vitiello Miriam Serena
Publication year - 2021
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.202008039
Subject(s) - materials science , terahertz radiation , optoelectronics , quantum cascade laser , graphene , optics , optical modulator , grating , phase modulation , nanotechnology , physics , phase noise
An electrically switchable graphene terahertz (THz) modulator with a tunable‐by‐design optical bandwidth is presented and it is exploited to compensate the cavity dispersion of a quantum cascade laser (QCL). Electrostatic gating is achieved by a metal grating used as a gate electrode, with an HfO 2 /AlO x gate dielectric on top. This is patterned on a polyimide layer, which acts as a quarter wave resonance cavity, coupled with an Au reflector underneath. The authors achieve 90% modulation depth of the intensity, combined with a 20 kHz electrical bandwidth in the 1.9–2.7 THz range. The modulator is then integrated with a multimode THz QCL. By adjusting the modulator operational bandwidth, the authors demonstrate that the graphene modulator can partially compensate the QCL cavity dispersion, resulting in an integrated laser behaving as a stable frequency comb over 35% of the operational range, with 98 equidistant optical modes and a spectral coverage ~1.2 THz. This paves the way for applications in the terahertz, such as tunable transformation‐optics devices, active photonic components, adaptive and quantum optics, and metrological tools for spectroscopy at THz frequencies.