Ultrafast pulse generation from QCLs
European Union’s Horizon 2020 research and innovation programme


Ultrafast and intense light pulse generation is an underpinning technology that enables numerous applications across the physical, chemical and biological sciences. Although, there have been impressive developments in semiconductor based devices for pulse generation in the optical range, there is a lack of such advances for the terahertz (THz) frequency range, despite proven applications in imaging, metrology and non-destructive testing.

In the ULTRAQCL project we will breakthrough this technological gap, using innovative and novel semiconductor concepts for the generation of intense and short THz pulses. Using THz quantum cascade lasers (QCLs) as a foundational device and their unique ultrafast properties, we will achieve pulse generation that is radically beyond the state-of-the-art. The ULTRAQCL project will implement original schemes and apply them to key applications highlighting the potential of ultrafast QCLs as ubiquitous technology for the THz range. These applications will include gas sensing with unprecedented sensitivity and quantum optics for advanced communication systems.

In Focus

Fermi level pinning at the Dirac point in epitaxial multilayer graphene

A paper on evidence of Fermi level pinning at the Dirac point in epitaxial multilayer graphene has has been published in Physical Review B by the group at CNRS-LPA. The authors investigated the temperature-dependent conductivity of epitaxial multilayer graphene using THz time domain spectroscopy and show evidence that the Fermi level in quasi-neutral graphene layers is pinned at the Dirac point by mid-gap states. The authors demonstrated that the scattering mechanisms result from the interplay between mid-gap states, which dominate in the vicinity of the Dirac point, and short-range potentials that govern at higher energies (>8 meV). These results highlight the potential of multilayer epitaxial graphene for probing low-energy Dirac (...)

Frequency and amplitude modulation of ultra-compact terahertz quantum cascade lasers using an integrated avalanche diode oscillator

A paper on self modulation of QCLs has been published in Scientific Reports by the group at CNR. The authors show a compact architecture to induce both frequency and amplitude self-modulation in a THz QCL. By engineering a microwave avalanche oscillator into the laser cavity, which provides a 10 GHz self-modulation of the bias current and output power, we demonstrate multimode laser emission centered around 3 THz, with distinct multiple sidebands. The resulting microwave amplitude and frequency self-modulation of THz QCLs opens up intriguing perspectives, for engineering integrated self-mode-locked THz lasers, with impact in fields such as nano- and ultrafast photonics and optical metrology. The full publication can be accessed (...)

Improving the output beam of Terahertz QCLs

The CNRS-LPA partner has demonstrated, in a new publication in Optics Express, a simple method to engineer the beam profile of a Terahertz QCLs. The far-field emission metal-metal QCLs is controlled in directionality and form through planar horn-type shape structures, whilst conserving a broad spectral response. The structures produce a gradual change in the high modal confinement of the waveguides and permit an improved far-field emission profile and resulting in a four-fold increase in the emitted output power. Full details can be found here

New types of photoconductive antennas

A new type of photoconductive antenna has been realised that eliminates the ’echo’ signals that typically originate from substrate reflections. These new devices will be of use to the time resolved study of the QCL emission. Full details of the work can be found here

Kick-off meeting

The ULTRAQCL project has started! The kick-off meeting for the ULTRAQCL project took place at the Centre Culturel Irlandais in Paris on 29th Nov 2015

Publication on short pulse generation from THz QCLs

A paper on generating short pulses from QCLs has been published in Optica by the group at CNRS-LPA. The authors bring new insights into the QCL modelocking and show, contrary to popular believe, that the ‘active microwave’ modulation is the key parameter that determines the pulse duration rather than the QCL bandwidth or ultrafast dynamics. This will now impact the future direction of the ULTRAQCL project. The full publication can be accessed here




Dr Sukhdeep Dhillon is a CNRS researcher in charge of the QCL activity at LPA and is the coordinator of the ULTRAQCL proposal.

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