Missions

Context:
Nonlinear (NL) optical phenomena play an important role in the fields of bioimaging, sensing, communications, and in the design of new laser-pumped coherent light sources. In the mid-infrared (MIR) spectral range, recent work on NL frequency generation has exploited intersubband transitions in III–V quantum heterostructures coupled to photonic microcavities or metamaterials [1,2]. This approach eliminates the phase-matching constraints present in waveguide architectures, while allowing enhancement of the NL signal through the microcavity effect.

Objectives:
In this project, we propose unipolar NL devices coupled to entirely new types of microcavities, enabling the exploitation not only of microcavity effects but also of collective electronic effects that appear at very high carrier densities. This additional degree of freedom has been neglected until now, even though a recently developed quantum theory for NL phenomena in this regime predicts improvements of several orders of magnitude in device performance compared to the current state of the art — both in terms of conversion efficiency and quantum yield [3].

Building on this new understanding, the main goals of the project are to demonstrate coherent sources (1) in the MIR range (λ ≈ 4–6 µm) and (2) in the terahertz range (λ ≈ 100–200 µm), exploiting respectively second-harmonic generation and difference-frequency generation. The targeted efficiencies exceed by several orders of magnitude those achieved so far by NL sources based on microcavities [2].
[1] Q. Lin et al. Optica 10, 1700, (2023)
[2] M. Hakl et al. ACS Photon. 8, 464–471 (2021).
[3] Lin et al. arXiv:2501.06091v2 (accepted for publication -APL Photon. March 2025)

Activities

- Electromagnetic design of microcavities using finite element simulation codes.
Main objective: to obtain a predictive model for optimizing light–matter coupling as a function of the microcavity array geometry and doping level.
- Fabrication of microcavity arrays in a cleanroom, following a well-established process flow within the team [1,2].
- Optical characterization of the microcavities using a Fourier-transform spectrometer, with illumination from (1) a broadband thermal source, (2) a pair of quantum cascade lasers, and (3) a pulsed source generating a train of MIR pulses with a temporal duration of ~150 fs. Main objective: determination of the nonlinear (NL) response.
[1] Q. Lin et al. Real-time, chirped-pulse heterodyne detection at room temperature with 100 GHz 3-dB-bandwidth mid-infrared quantum-well photodetectors, Optica 10, 1700–1708 (2023)
[2] Q. Lin et al. Room-temperature, continuous-wave terahertz generation in free-space with an intersubband mid-infrared photomixer, APL Photonics 10, 046102 (2025)

Skills

• Motivated, independent, and rigorous candidate, capable of taking initiative and contributing new ideas.
• Ability to work effectively as part of a team.
• Strong background in electromagnetism, optoelectronics, and quantum mechanics.
• Experience with electromagnetic finite element simulation codes.
• Solid experimental experience in mid-infrared and THz optics (Fourier-transform spectroscopy, lasers, nonlinear generation).
• Strong experience in micro- and nanofabrication of III–V semiconductor–based devices.
• Good command of written and spoken English.
• Strong writing skills (report and article preparation).

Work Context

The work will take place within the framework of an ANR-funded project, in collaboration with the ESPCI–PSL Laboratory. The research will be carried out in tandem with another postdoctoral researcher, within the THz-Photonics group at the IEMN laboratory. The group has long-standing experience in the design and fabrication of optoelectronic devices spanning the THz to MIR ranges, and is fully equipped for MBE growth, device fabrication, and characterization of the components developed in this project.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

Des déplacements de courte durée en France et à l'étranger sont à prévoir.

Additional Information

Short trips within France and abroad are to be expected.