The generation of stable trains of ultrashort (femtosecond to picosecond), terahertz-frequency radiation pulses with large instantaneous intensities is an underlying requirement for the investigation of light–matter interactions for metrology and ultrahigh-speed communications. In solid-state electrically pumped lasers, the primary route to generate short pulses is through passive mode-locking; however, this has not yet been achieved in the terahertz range, defining one of the longest standing goals over the past two decades. In fact, the realization of passive mode-locking has long been assumed to be inherently hindered by the fast recovery times associated with the intersubband gain of terahertz lasers. Here we demonstrate a self-starting miniaturized short pulse terahertz laser, exploiting an original device architecture that includes the surface patterning of multilayer-graphene saturable absorbers distributed along the entire cavity of a double-metal semiconductor 2.30–3.55 THz wire laser. Self-starting pulsed emission with 4.0-ps-long pulses is demonstrated in a compact, all-electronic, all-passive and inexpensive configuration.
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This work was supported by the European Research Council through the ERC Consolidator Grant (681379) SPRINT (MSV), FET Open project EXTREME IR (944735) (MSV, SSD), Quantera Project QATACOMB (MSV, SSD, CJ), ERC GSYNCOR (ACF), HETERO2D (ACF), EIC CHARM (ACF), the French National Research Agency (ANR-18-CE24-0013-02 - ‘TERASEL’) (SD), and the EPSRC (UK) programme grant ‘HyperTerahertz’ (EP/P021859/1) (EHL, LL, AGD), EP/L016087/1, EP/K01711X/1, EP/K017144/1, EP/N010345/1, EP/V000055/1 (ACF) and Graphene Flagship (MSV, ACF).
The authors declare no competing interests.
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Supplementary Figs. 1–4 and Supplementary Discussion 1–4, which is broken down as follows: (1) flowchart of the fabrication process; (2) measurement of the refractive index in MLG; (3) DGSA-QCL with different cavity dimensions and MLG thickness; and (4) micro-Raman characterization.
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Riccardi, E., Pistore, V., Kang, S. et al. Short pulse generation from a graphene-coupled passively mode-locked terahertz laser. Nat. Photon. 17, 607–614 (2023). https://doi.org/10.1038/s41566-023-01195-z