An FPGA-based system for real-time locking of a tunable laser at the constantly shifting resonance wavelength of a silicon photonic sensor, ensuring optimal performance of an interferometer.
Interferometry and silicon photonics drive advancements in precision measurement and sensing, with many real-world applications. Interferometers rely on light wave interference for sensitivity, while silicon photonics leverage their light-material interactions for precise detection of environmental changes. This project aims to lock a tunable laser at the resonance wavelength of a silicon photonic sensor in a photoelectric system, enabling an interferometer to detect minor environmental changes. Locking the laser at the resonance wavelength ensures peak transmission and optimal system performance. To achieve this, a hardware-based feedback loop algorithm was developed on an FPGA, leveraging its speed to dynamically adjust the laser’s wavelength using triads of dynamically sampled points on the sensor’s characteristic transmission graph. The challenge lies in the constant shifting of the graph, the system`s noise, and the inherent overhead of software, hence the hardware solution. The algorithm mitigates noise through techniques like averaging and quantization of the transmission. It enhances reactivity with dynamic step size to adapt performance to the shifting peak transmission and the operation point’s relative distance from it. The system demonstrated robust performance in real-world scenarios, effectively locking the maximum transmission and recovering quickly from environmental changes and transmission fluctuations. These results highlight the reliability of the FPGA-based approach for ensuring precise laser control in silicon photonic sensor systems.
