Linearisation of optical micro-sources for communications

Would you like to play a part in the future of optical transmission for high-speed communications? This PhD will play a key role, focusing on performance and energy efficiency, with a particular focus on encouraging the emergence of optical solutions with low carbon costs and low dependence on rare materials.
The field of non-coherent optical communications on LEDs has been booming in recent years, notably due to the advantages that GaN and organic microLEDs can bring in terms of high data rate ([1-2],, energy efficiency and hybrid integration for recent and varied applications such as LiFi, communications on fibre (data centres, etc.) or on waveguide (chip-to-chip). However, on one hand these sources require delicate optimisation of the waveform parameters due to their multi-factorial and complex frequency behaviour, and on the other hand they impose non-linearities and memory effects that limit performance and can be similar to the phenomena introduced by power amplifiers in conventional RF systems, albeit with their own specific features. Over the last ten years or so, studies have attempted to compensate for these non-linearities by using models with different trade-offs between complexity and modelling accuracy, with validations on commercial macro-LEDs. In addition, microLEDs such as those developed at the CEA ( have recently come to the fore in certain areas of research, thanks to their high bandwidth and high integration, but with specific HF behaviour and memory effects increased by a modulation band exceeding one gigahertz.
The thesis will first study solutions for optimising the configuration of multicarrier waveforms based on the specific characteristics of optical microsources (inverse dependence of efficiency and bandwidth on polarisation). Secondly, non-linearity compensation algorithms will be implemented on this type of optical source in an attempt to improve transmission rates or distances, based on complexity/performance trade-offs. Hardware validations of the digital solutions developed will be carried out on micro-sources implemented in instrumented transmission benches, enabling a real-time demonstration of the innovations produced during the thesis.
You will be part of a dynamic team working on a wide range of research topics relating to signal processing, protocols and implementation platforms. We are looking for a candidate with a background in digital communications, signal processing and optoelectronics, who is genuinely motivated to work on a multidisciplinary subject (waveforms, algorithms, modelling, simulations and hardware implementation).
We will offer you a unique research environment dedicated to ambitious projects that address today's major societal challenges, experience at the cutting edge of innovation (strong potential for industrial development) and exceptional experimental resources, leading to real career opportunities in R&D at the end of your thesis.
Come and join us, develop your skills and acquire new ones! To apply, please email your CV directly to

[1] M. N. Munshi, L. Maret, B. Racine, A. P. A. Fischer, M. Chakaroun and N. Loganathan, "2.85-Gb/s Organic Light Communication With a 459-MHz Micro-OLED," in IEEE Photonics Technology Letters, vol. 35, no. 24, pp. 1399-1402, 15 Dec.15, 2023, doi: 10.1109/LPT.2023.3327612.
[2] L. Maret et al., « Ultra-High Speed Optical Wireless Communications with gallium-nitride microLED », Photonics West, SPIE OPTO, Light-Emiting Devices, Materials and Application 2021

Exploring the Future of Satellite Communications: Dual-Band Electronically Reconfigurable Flat Lens Antennas with Ultra-Wide Scan Range

CEA Leti offers a PhD topic to develop new electronically scanning antennas for efficient data transmission in satellite communications (Satcom). Novel efficient electronically scanning antennas are essential for future satellite communications (Satcom). Electronically reconfigurable flat lens antennas, also known as transmitarrays, are a promising architecture to achieve high scanning performance. Each element of the flat lens introduces an optimized phase shift on the impinging wave emitted by a primary source, to steer and shape the radiation pattern. The phase profile over the lens can be dynamically modified by adding reconfigurable devices in the cells, such as switches (e.g. pin diodes) or varactors. Compared to phased arrays, these antennas attain high-gain beam-steering with a significantly lower power consumption and architectural complexity.
The Ph.D. work aims to propose and experimentally demonstrate novel concepts and design methods for wideband/multi-band electronically beam-steering flat lens antennas. The main research goals are:
. Study of new approaches for designing unit cells with broad radiation patterns, stable performance under oblique incidence and wideband/multiband operation.
. Electrically thin subwavelength cells and Huygens’ radiating elements will be investigated to tailor the angular and frequency response of the cell.
. Novel design solutions to enable a fine electronic control of the phase shift introduced by the cells. Multilayer cells comprising either pin diodes or varactors, or a combination of both, will be analyzed. The trade-offs between phase resolution, bandwidth, power consumption, number of reconfigurable devices and bias lines, will be studied.
. Development of dedicated synthesis procedures to enable the independent control and shaping of the radiation pattern at two or multiple frequencies.
. Experimental demonstration of high-gain dual-band fixed-beam and electronically 2-D beam-steering prototypes achieving extremely wide scan ranges (±60° or greater). The demonstratators will be optimized to work in typical Satcom bands (e.g. around 20 GHz and 30 GHz).