Study context :

Photonic Integrated Circuits (PICs) are fast‐growing for very high data rate applications. Long distance optical
communication and the emerging data centers are quite pioneering in the progress of these technologies and
particularly on silicon platform. Systems such as Analog Radio‐over‐Fiber (A‐RoF) benefit from technological
progress in optical communications and could gain a great advantage from silicon PICs. The challenge of the
communication is now to miniaturize the photonic system as it has been done earlier for the electronic system
owing to the development of the microelectronic technology. Nowadays, this objective is based on the
development of the PIC whose forecasts for the years 2021‐2030 announce an average annual growth rate of
20.5%. III‐V technology now accounts for 81.8% of the PIC market share, while only 16% of the PIC market is
carried by Silicon technology. In order to follow the objective: smaller and cheaper, the design of photonic
integrated circuits on silicon for telecom and for home area network applications is a good challenge, its margin
progress in terms of market share being significant. However, today this mature PICs technology is optimized for
digital communications and not optimized for analog‐photonic communications. Thus, the building blocks of
silicon photonic components for A‐RoF systems concern optical waveguides, intensity and phase modulators,
optical filters and hybrid III‐V Silicon laser sources and photodiodes. The future A‐RoF system and more precisely,
each of the building block, has to be redesigned and optimized to fit in the 6G fronthaul architectures for an
enhanced mobility at a higher data rate, and also for LiFi communications. We will focus in this thesis on the
hybrid III‐V laser on silicon platform where the photonic integrated technology will bring a cost‐effective solution.

The main activity of ESYCOM lab linked to the subject is the development of advanced models based on physical
parameters of all the Analog-Radio over Fiber (A-RoF) blocks to increase the data rate and to reduce complexity,
consumption and cost. The targeted applications concern telecommunication for cities and buildings (outdoor and
indoor environments) to build the new generation architectures.

PhD subject :

This PhD position deals with the modelling of the optical source for optical communication architectures in integrated
photonic technologies. The hybrid laser is designed at III-V Lab and fabricated at III-V Lab for the lasing region and
CEA-Leti for the hybrid integration [1], [2], [3]. Because this hybrid source is a major element in a A-RoF system, it
will be fundamental to understand the requirements based on the laser characteristics to respect the high data bit
rate of A-RoF architectures. As phase modulation link requires laser diode with narrow linewidth, the technological
process of the III-V laser on silicone platform will be investigated to determine the main limitations of the light
coupling between the two technologies (III-V to Si).

The laser model will be developed from the rate equations of carriers/photons dynamics and the light coupling from
the gain medium (III-V medium) to the silicon cavity. The mode profile and confinement, optical losses, optical  filters and reflectors will be also considered. These parameters will be considered through advanced modeling
considering electromagnetic simulation coupled to rate equations. Once the laser model will be developed, the
critical technological limits will be strongly analysed and optimized in order to reduce the future RUN of such hybrid
photonic devices during their development.

Objectives of the thesis :

This thesis focuses on the study of Silicon-based laser sources for A-RoF architectures and the mainly objective
concerns the development of an advanced physical model. The PhD student will contribute to this modeling to
accelerate the design of new future hybrid laser reducing the steps of technological RUN. The different key points
are:

• Theoretical consideration of hybrid laser diode realized at CEA-Leti on silicon platform.
• Understanding of A-RoF architectures, telecommunication applications and PICs technology.
• Development of advanced models of this component combining an equivalent circuit models [5] and
  numerical methods.
• Characterization of hybrid lasers to validate the developed model.
• Simulation and characterization of simple A-RoF system build on PICs to evaluate link performances with an
  advanced complex waveform.

Candidate profile :

Applicants should follow a MSc degree related to electronics, microwaves and photonics or applied physics. Skills in
optoelectronics and integrated components are beneficial. Experience and knowledge on CAD software, Maltlab,
C/C++ programming language, Electromagnetic software will be strongly appreciated.

Contacts and application :

Send a CV and a cover letter to:
Catherine Algani: catherine.algani@lecnam.net (Full Professor, Esycom-Le Cnam)
Anne-Laure Billabert: anne-laure.billabert@lecnam.net (Full Professor, Esycom-Le Cnam)
Salim Faci: salim.faci@lecnam.net (Associate Professor, Esycom-Le Cnam)

Esycom sort description :

Esycom Lab has a strong expertise in the following engineering fields: communication systems, sensors and
Microsystems. This expertise matches the labs project entitled Communication systems and sensors for the city, the
environment and people . Six research areas are developed: antennas and propagation, architectures, microwave
photonic devices, microsystem analysis, medical sensors, energy harvesting. Three well-equipped platforms are
dedicated to the characterization of the developed components and systems. Esycom Lab is labeled CNRS.