Since the beginning of this project in November 2020, an important part of the work has been dedicated to setting the scene before the real scientific effort could be made. This includes the recruitment of two PhD students and one post-doctoral researcher. In the mist of the covid crisis which was still having a significant impact in 2020-2021, the process was unfortunately slower than usual and the whole team was only up and running by September 2021. This initial delay was however not a loss as we have exploited it to purchase the important pieces of equipment necessary for our project, including a new optical table, two high-performance tunable lasers, a real-time large bandwidth electrical spectrum analyser and a large bandwidth arbitrary waveform generator. With the complete team and available equipment, it was then possible to kick off the scientific work both experimentally and theoretically.
For the latter, we started simulating a multi-mode rate equation model that we then expanded to include up to 4 different wavelengths, (modulated) optical injection and phase-controlled optical feedback to match the characteristics of our experimental system. Though simulations were also used to confirm a good agreement with experimental results, we primarily focused on the effect of optical feedback and the constraint on laser and feedback parameters to achieve good control of the laser multi-wavelength emission. Thus, we used random sampling techniques to explore the system behaviour in a comprehensive way despite the large number of parameters. We are now processing these data to extract a clear set of constraints to achieve good control of the laser. In a next step, we will verify that these constraints scale well when additional modes are considered.
Experimentally, taking advantage of the multi-wavelength lasers already available in the lab, we performed a detailed characterization of their emission properties and behaviour. This was obviously a very important step to a have a clear baseline for further investigations. We then started investigating their response to optical injection, i.e. their behaviour when coherent light from another laser is sent to the device. Afterwards, we were then ready to add a modulation to the optical injection which led to two research breakthroughs detailed in the next section, namely the demonstration of spectral multiplication and wavelength conversion capability.
Finally, we also prepared several new laser designs and sent them for manufacturing to our partner foundry platform. At this stage, we are unfortunately still waiting to receive these new devices.
