CMOS Integrated Readout and Control Circuits for Closed-Loop Bio-Photonic Systems

CMOS biosensors integrated with visible-light photonics offer a promising route toward compact, highly sensitive, label-free platforms for the detection and stimulation of biological targets. Integrated photonics provides a powerful biosensing technology that translates changes in biological samples into measurable optical signals through molecular interactions at the sensor surface. As such, it is a key enabling technology for real-time, label-free biological sensing.

CMOS integrated circuits (ICs) constitute an attractive platform for interfacing with integrated photonic devices. They enable high-sensitivity photodetection, low-noise analogue signal processing, mixed-signal control, and dense multi-channel integration within compact and power-efficient systems. However, the intrinsic sensitivity of a photonic sensing element does not automatically translate into high system-level sensitivity. Overall performance is jointly limited by challenges arising in both the photonic and CMOS domains. On the CMOS side, small optical perturbations must be converted into electrical signals and accurately resolved in the presence of photodetector shot noise, large DC photocurrents, transistor thermal and flicker noise, limited dynamic range, circuit offsets and mismatches, and electromagnetic interference. The electronic interface must therefore provide high sensitivity, low input-referred noise, wide dynamic range, low power consumption, and accurate multi-channel readout. On the photonic side, performance can be degraded by fabrication tolerances, wavelength and intensity fluctuations of the optical source, optical losses, thermal drift, device mismatch, and environmental variations. These effects require continuous monitoring, tuning, and stabilisation of the photonic subsystem. Consequently, the CMOS circuitry must not only perform signal acquisition but also provide the sensing, calibration, and control functions required to maintain optimal photonic operation. Achieving high system-level biosensing performance therefore requires a holistic co-design approach encompassing both the photonic devices and the CMOS readout and control electronics.

This PhD project will focus on the development of high-sensitivity analogue and mixed-signal CMOS readout and closed-loop control circuits for visible-light photonic biosensor systems. The CMOS research will be carried out in close collaboration with the development of a complementary self-monitoring and self-stabilising photonic platform. On the photonics side, collaborating researchers will design and realise visible-light photonic devices, including integrated light sources or laser interfaces, sensing structures, optical monitoring elements, and photonic tuning mechanisms. These photonic components will provide both the sensing functionality and the actuation mechanisms required for electronic feedback and stabilisation.

The ultimate objective is to integrate the CMOS readout and control IC with a visible-light silicon-photonic platform to realise a unified closed-loop biosensing system. The photonic subsystem will perform sensing and monitoring, while the CMOS subsystem will provide photodetection, signal processing, calibration, and feedback control. The resulting self-monitoring and self-stabilising platform aims to maintain high sensitivity under varying operating conditions. Beyond biosensing, the developed CMOS-photonic architectures are also relevant to applications such as optogenetics, wavefront-shaping imaging, and programmable photonics.

Skills and background:

• Master's degree (or equivalent) in Electrical Engineering, Microelectronics, Electronics Engineering, or a related field.
• Strong knowledge of analog and mixed-signal integrated circuit design.
• Experience with IC design and simulation tools (Cadence Virtuoso, Spectre, etc.).
• Good understanding of transistor-level design, analog building blocks, and mixed-signal architectures.
• Experience with MATLAB and/or Python for modelling and simulation.
• Familiarity with ASIC verification and laboratory characterization is a plus.
• Experience with PCB design and measurement instrumentation is a plus.
• Strong analytical skills and enthusiasm for hands-on circuit design and experimental research.