Background: 

Satellite instruments have now been deployed for the spectroscopic analysis of planet atmospheres in particular to further our understanding of their chemical composition as well as global circulation models. On Earth, Aura’s Microwave Limb Sounders-MLS has flown radio receivers for frequencies up to 2.5 THz to measure Earth’s stratosphere (Ozone). Today ESA is considering direct observations of atomic oxygen, the hydroxyl radical, carbon monoxide and nitrous oxide in the upper atmosphere requiring receivers that operate up to 4.7 THz (KEYSTONE). Similarly, THz heterodyne receivers have been built at lower frequencies to measure water and carbon monoxide emissions from comets (Microwave Imager for the Rosetta Orbiter-MIRO at 557 GHz); or Jupiter and its Icy moon’s atmospheres and surfaces (JUICE-SWI) with two channels working at 0.6 and 1.2 THz (mainly using the transitions of water and methane as wind tracers). 

These heterodyne front-end instruments are based on III-V THz Schottky technology for both the detector (mixer) and its local oscillator source (frequency multiplier chain), today available respectively up to 2 THz and 1 THz (state-of-the-art demonstrated recently at JPL, USA, ongoing work at LIRA, France). In particular, these front-ends can operate at room temperature, with a relative bandwidth reaching 20 % and a spectral resolution of 10^7 across an instantaneous spectrum of up to tens of GHz (IF).  Therefore, they offer unprecedented opportunities to study at the same time wind dynamics, abundancy of atmospheric contents and surface temperatures of the planets, comets and planet atmospheres.

During the last 15 years, the THERA group at LIRA (former GEMO group at LERMA) in association with the clean room at C2N, has developed a manufacturing process for Schottky diodes, and was the main contributor to the detectors of the Submillimeter Wave Instrument (SWI) for ESA’s JUICE mission launched in 2023. The mixers, fabricated with this process, define the world’s state-of-the-art at 600GHz and 1.2 THz, and, in the case of the latter, are qualified for space operation (TRL8), which is a strong asset for future space science missions (MADNESS for Mars, KEYSTONE for Earth) in France. 

With this success, maturity, and recent investments in Europe, we intend to go one step further and miniaturize Terahertz heterodyne instruments on one hand to allow the construction of arrays receivers and compact multichannel solutions, on the other hand to make them competitive for nanosatellites. Current instruments are still using single pixels per frequency band, in addition they require a complex bias scheme for their local oscillator tuning, and are order of magnitude away from a volume compactness required in focal plane arrays.

Project: 

The mixer and frequency multipliers are built with the THz Schottky technology that feature sub-micron anode size Schottky junctions (diodes) integrated in few-millimeters-long MMICs. Currently, every MMIC is then integrated and packaged in a separated mechanical block. The mixer block plus its LO multiplication chain (one block per multiplication element) are connected together through waveguide interfaces, which use a large volume of typically 20x10x3 cm3 for the front-end receiver only. This makes it difficult to consider more than a single receiver pixel per band and is still much too bulky compared to what is required for focal plane arrays. In addition, the receiver performance suffers from losses at the interfaces between elements, highly critical at THz frequencies. 

This thesis has the ambition to develop new integration paradigms for Schottky-based heterodyne instruments at terahertz frequencies, with special attention to minimize the transmission line losses and excess noises, so that only the junctions limit the system performances.  Those paradigms will aim also to drastically reduce the front-end volume, in order to make it attractive for multi-band and/or multi-focal elements configurations.  The recruited student will first carry out a thorough literature review of existing packaging and interfacing solutions used in high frequency hybrid technology low-noise systems. The different elements influencing the performances will be analyzed. New technological approaches will be explored such as integrating the front-end receiver in a unique compact mechanical block, fabricated either by traditional mechanical cutting, or by Silicon etching and the technical limits will be identified. The study will also encompass RF designs of new MMICs, with harmonics simulations, to enhance the performances through lower loss interfaces of the MMICs and their neighbouring stages (such as LNAs, thermal breaks, ESD and filter protection circuits). The theoretical study, design and RF measurements of the novel THz front-ends will be performed at LIRA under the supervision of Dr. Jeanne Treuttel and Dr. Yan Delorme.

=================

For more Information about the topics and the co-financial partner (found by the lab!); contact Directeur de thèse - yan.delorme@obspm.fr

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online before March 13th, 2026 Midnight Paris time!