All in One‐Chip, Electrolyte‐Gated Graphene Amplitude Modulator, Saturable Absorber Mirror and Metrological Frequency‐Tuner in the 2–5 THz Range. Issue 22 (14th September 2022)

• Record Type: Journal Article
• Authors: Di Gaspare, Alessandra; Pogna, Eva Arianna Aurelia; Riccardi, Elisa; Sarfraz, Syed Muhammad Abouzar; Scamarcio, Gaetano; Vitiello, Miriam Serena
• Is Part Of: Advanced optical materials. Volume 10:Issue 22(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-09-14
• Subjects: ionic liquid gating -- modulators -- saturable absorbers -- single layer graphene -- terahertz; Optical materials -- Periodicals; Photonics -- Periodicals; 620.11295
• DOI: 10.1002/adom.202200819
• Languages: English
• ISSNs: 2195-1071

Abstract

Abstract: Layered 2D materials display unique optical and electrical properties that can enable manipulation, propagation, and detection of electromagnetic waves over a broad spectral range, with a high level of control, offering the potential to activate different functionalities, by optical or electrical means, in a single chip. Here, a compact optoelectronic device behaving as an amplitude modulator, saturable absorber mirror (SA mirror), and frequency‐tuner is conceived at terahertz (THz) frequencies. It comprises a gate‐tunable single layer graphene (SLG), embedded in a quarter‐wave cavity, operating in the 1–5 THz range. The use of electrolyte ionic liquid gate ensures 40% optical amplitude modulation depth. Z ‐scan self‐mixing interferometry reveals 60% reflectivity modulation, with ≈4.5 W cm −2 saturation intensity. By integrating the modulator/SA mirror with a heterogeneous THz quantum cascade laser frequency comb, in an external cavity configuration, fine‐tuning of the intermode beatnote frequency is also demonstrated. This opens intriguing perspectives for short pulse generation, phase‐locking, frequency tuning/chirping, phase modulation, and metrological referencing, inter alia. Abstract : A gate‐tunable single‐layer graphene embedded in a quarter‐wave cavity behaves as a terahertz (THz) compact amplitude modulator, saturable absorber, and frequency tuner. Electrolyte ionic liquid gating ensures 40% modulation depth and 60% reflectivity modulation with ≈4.5 W cm −2 saturation intensity. Fine‐tuning of the intermode beatnote frequency of a THz quantum cascade laser frequency comb is demonstrated.