TERAULTRA · Terahertz Ultra-Short Pulses from Self-Induced Transparency Modelocked Quantum Cascade Lasers
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2016-03-01 → 2018-02-28
- EU contribution
- €195,455
- Participants
- 1
- Scheme
- MSCA-IF-EF-ST
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Results in brief
Terahertz Ultra-Short Pulses from Self-Induced Transparency Modelocked Quantum Cascade Lasers
The terahertz (THz) frequency range lies between microwaves and visible radiation in the electromagnetic spectrum. This relatively unexplored region of the spectrum is attracting significant interest internationally due to its ability to discriminate samples chemically, to identify differences in physical structure, and to penetrate non-polar materials. However, it lacks a compact semiconductor source of ultrashort THz pulses, suitable for applications including ultrafast spectroscopy for materials analysis, and THz frequency comb generation with applications for trace gas sensing and atmospheric science. Although the quantum cascade laser (QCL) is a promising compact semiconductor source of THz radiation, its success in creating ultrashort pulses is limited due to the inherent fast gain recovery time. The exciting possibility has been proposed of exploiting the phenomenon of self-induced transparency (SIT) for passive laser modelocking, in which the pulse duration is mediated through the process of Rabi-flopping. The aim of the TERAULTRA project was to explore, for the first time, the feasibility of generating ultrashort THz pulses from QCLs by exploiting SIT phenomenon. In working towards this goal, this project aimed to explore, both theoretically and experimentally, the underlying phenomenon of Rabi-flopping and SIT in quantum heterostructures and QCLs in the THz frequency range. The project also aimed to explore alternative approaches to achieving broadband emission in THz QCLs such as using cascaded two-photon emissions. The TERAULTRA project: demonstrated, for the first time, SIT effects in quantum heterostructures at THz frequencies; designed, experimentally investigated and optimised THz QCL heterostructures for SIT-modelocking and short pulse generation; and proposed and designed the first two-photon emitting THz QCLs.
Data: CORDIS, © European Union
Project objective
The terahertz (THz) frequency range in the electromagnetic spectrum lacks a compact semiconductor source of ultra-short pulses, suitable for applications including ultrafast spectroscopy, atmospheric science and stable THz frequency comb generation. Although the quantum cascade laser (QCL) is a promising compact semiconductor THz source, its success in creating ultra-short pulses is limited due to the inherent fast gain recovery time. There have been demonstrations of short pulse (>1 ps) generation from THz QCLs based on active modelocking, although the stability of the pulses is limited. Crucially, there has been no demonstration of passive modelocking of QCLs to date, which in principle can create pulses much shorter than 1 ps.The goals of the proposed TERAULTRA research are to break through this technological challenge, and create THz ultra-short pulses of <1 ps from QCLs using self-induced transparency (SIT) effects. Recently, it has been proposed that QCLs are the ideal tool to realize SIT mediated modelocking owing to their relatively long inter-subband coherence times, and, importantly, the possibility of interleaving gain and absorbing media with engineered dipole moments. While the gain medium produces gain, the absorbing medium absorbs the resonant light, suppressing the growth of the continuous waves, thereby creating short pulses. We will design THz QCLs with coupled gain and absorbing media that can initiate modelocking using SIT effects, for the first time. By simulating the gain recovery and dephasing times, dipole moments, and gain and absorption parameters, the stability of the modelocked pulses will be determined and understood theoretically. We will then demonstrate experimentally the first modelocked laser exploiting the SIT effect, based on a THz QCL with interleaved gain and absorbing media in the growth direction as well as based on independently-controlled two-section waveguide cavities, leading to pulse widths <1 ps.
Original text from CORDIS.
Participants
- UNIVERSITY OF LEEDS · LeedsCoordinatorUnited Kingdom
Links
- View on CORDIS
- DOI: 10.3030/703912
- https://engineering.leeds.ac.uk/staff/753/Dr_Muhammad_Anisuzzaman_Talukder
Data: CORDIS, © European Union