PhD thesis offer: Laser fabrication and frequency-comb sources for THz photonics (M/F)

Job Description

Thesis Subject

Frequency-comb lasers are light sources that emit many evenly spaced optical frequencies (“comb lines”) at the same time, rather than a single wavelength. In the time domain, this corresponds to a train of ultrashort, highly regular pulses (or an equivalent phase-locked multimode output). Because the spacing between the lines is extremely stable and precisely defined, frequency combs provide an optical “ruler” that links optical frequencies to radio-frequency (RF) references with exceptional accuracy and coherence.
They are important because they enable a wide range of applications that rely on phase-stable multiwavelength light, including precision spectroscopy and metrology, coherent communications, and low-noise microwave generation. In THz photonics specifically, comb lasers are especially attractive: when two (or more) comb lines are mixed on a high-speed photodiode, their optical beating directly produces a THz signal whose frequency is set by the line spacing (or selected line differences). This makes frequency-comb lasers a compact, tunable, and potentially integrated route to generate coherent THz radiation, while offering clear knobs—optical power per line, coherence, stability, and spectral bandwidth—to optimize the resulting THz performance.
This PhD project aims at developing III-V semiconductor laser sources—especially frequency-comb lasers on InP substrates—and exploiting them for terahertz (THz) generation through optical beating (photomixing). The candidate will work primarily in the IEMN cleanroom, developing and optimizing micro/nanofabrication process flows for laser device realization. A first research axis will focus on the epitaxial growth, fabrication, and characterization of quantum-dot-based and quantum-well-based frequency-comb lasers using active media developed at IEMN (EPIPHY group). The work will include process development, yield and reproducibility improvement, and detailed analysis of optical and electrical device performance.
Once optimized, the laser sources will be integrated with a high-speed photodiode (developed by the Photonics-THz group) to generate THz radiation by photomixing of comb lines. This stage will establish clear links between laser-comb characteristics (spectrum, power, coherence, stability) and the resulting THz performance.

Your Work Environment

The PhD candidate will receive a comprehensive training in IEMN's cleanroom facilities. The cleanroom work will rely on process modules including molecular beam epitaxy (MBE), dielectric deposition (PECVD and/or sputtering), optical lithography, dielectric patterning by RIE, pattern transfer into MBE-grown III–V heterostructures by ICP etching, and metal deposition for electrical contacts. The candidate will use a broad set of characterization techniques to assess process outcomes, material quality, and device performance, including optical microscopy, photoluminescence, scanning electron microscopy (SEM), atomic force microscopy (AFM), x-ray diffraction (XRD), profilometry, and spectroscopic ellipsometry, complemented by optoelectronic characterization of the fabricated devices. Overall, the project supports IEMN research on light-emission technologies, with applications ranging from telecom/datacom laser sources to frequency-comb-enabled THz photonics.

The work will be performed at the Institut d'Electronique de Microélectronique et de Nanotechnologie (IEMN) located in Villeneuve-d'Ascq near Lille in the Hauts-de-France region. IEMN is a research laboratory bringing together 500 people (professors, international researchers, engineers, technicians and students) from the CNRS, the University of Lille, the Polytechnique Hauts de France University and the Centrale Lille and Junia-ISEN engineering schools. The laboratory focuses on micro and nanotechnologies and their applications in the fields of information, communication, transport and health. Our researchers have access to exceptional experimental resources, in particular technological and characterization resources whose capacities and performance are at the highest European level. The IEMN is part of the RENATECH network of major technology centers.

Compensation and benefits

Compensation

2300 € gross monthly

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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