Thèse

When shining classical light onto a non-linear medium, intriguing quantum states of light can be generated such as squeezed states, single photon states or complex multiphoton entangled states. In the past years, physicists have proposed to use lattices of highly non-linear resonators to engineer spatial and temporal entanglement between photons [1]. To date, a versatile and scalable experimental platform is still missing in the optical domain, where a great variety of applications are foreseen for quantum science and quantum technology.
Our group at C2N has developed a unique expertise in designing photonic lattices of coupled non-linear semiconductor microcavities. We show, in Fig. 1, some examples of assemblies of coupled microcavities where light emulates the properties of electrons in a benzene molecule or in graphene [2].
The challenge we propose to tackle during this PhD program is to engineer interactions between photons that are strong enough (at the single photon level) to enter the quantum regime. To do so, we will optimize the non-linear medium and produce a new generation of non-linear semiconductor lattices using the state-of-the art nanotechnology tools that are available in the C2N clean room.
The candidate will contribute to the exploration of these new structures by realizing optics experiments under cryogenic conditions (4 K). The goal will be to use advanced optical measurements techniques in order to quantify photon-photon interactions in the cavities
(pump-probe spectroscopy), measure the quantum correlations in trains of photons emitted through the cavity (Hanbury Brown and Twiss experiment) and evidence entanglement (measurement of the spatio-temporal correlations). Analysis of the experimental data will besupported by theoretical modeling developed by the applicant in collaboration with theoretician collaborators through our large network of international collaborators.
We are looking for a candidate with skills and interest in experimental work, as well as solid knowledge in quantum optics and solid state physics.

References:
[1] C. Ciuti, and I. Carusotto, Quantun fluids of light, Rev. Mod. Phys 85, 299 (2013).
[2] A. Amo and J. Bloch, Exciton-polaritons in lattices: A non-linear photonic simulator, C. R.
Phys. 17 (2016).

Thèse

Project context
In spite of the fact, that the strongest emission lines of our Milky Way, such as [NI] (1.46 and 2.46 THz), [CI] (1.9 THz) and [OI] (4.7 THz) etc, lies in the THz/far-infrared region, this region is still largely unexplored due to poor atmospheric transmission and the necessity to observe from space as well as the lack of sensitive receivers. Heterodyne spectroscopy, largely used in astronomy, planetology, Earth science and even in commercial applications, allows the detailed analysis of the incoming signal with excellent spectral resolution.
In a heterodyne receiver the received sky signal is mixed by a mixer with an artificial monochromatic signal created by the local oscillator (LO). These LO and mixer are the heart of a heterodyne receiver and determine its performance. Heterodyne receivers are routinely used up to 350 GHz, but very few mixers and LOs exist at THz frequencies. To open up this observing window it is essential to develop sensitive THz mixers and powerful THz local oscillators.
During the last 15 years, LERMA associated with C2N work together on the design and the realisation of THz mixers and multipliers, based on the GaAs Schottky diodes, in order to build the sensitive THz devices for radioastronomy. Recently, LERMA-C2N developed and fabricated the 300GHz and 600GHz multipliers, as well as the 1.2THz mixer, that are installed on the Submillimeter Wave Instrument (SWI) for the JUICE mission, which will be lanced in 2023 to study Jupiter and its moons. To keep its leading position, LERMA aims to push further the limits of fabrication technology to reach frequencies as high as 5THz.

Objectives
This experimental thesis has the ambition to develop the process allowing the fabrication of high quality, performant and robust Schottky diodes operating up to 5THz. Several proposals of space missions, that require such THz devices, will be submitted soon in order to answer the call for ESA’s Medium-size class missions (M7) for satellites and the call for NASA’s probes.
The candidate will be co-supervised by two research laboratories (LERMA and C2N) and by CNES. For the process development, she/he will work in the advanced clean room of C2N on state-of-the art equipment for micro- and nano-fabrication. The theoretical study, DC and RF measurements as well as the design of future 1.9THz multiplier or 4.7THz mixer will be performed at LERMA. This work will allow the PhD student to acquire a large experience in nano-technology and device fabrication (electron beam lithography, thin metal and dielectric layer deposition, dry etching and other clean room tools), in physics of semi-conductors as well as in
DC and RF characterizations of the microwave circuits.

Candidate
Required education level: Master or equivalent degree in electrical engineering or physics.
Duration: 36 months.
Required background: Physics of solids (semiconductors). Knowledge in nano/microfabrication or in radio wave frequency electronics is welcome. Good knowledge of English is expected.
Deadline to apply: 25th of March 2022
Contact persons :
To apply please send your motivation letter, CV, and recommendation letters (optional) to:
Dr. Lina GATILOVA (LERMA, Observatoire de Paris, Paris), lina.gatilova@obspm.fr

All the candidatures are evaluated. However, due to the large number of applications we receive, we will contact only the
short-listed candidates