Conventional lasers typically comprise of simple resonators with a well-defined comb of modes. Coupling many resonators together to form larger complex cavities provides a way to engineer the spatial and spectral distribution of modes, which can be leveraged to develop sensitive and controllable on-chip light sources, for use in signal processing, optical communication and optical computing.

In this talk I will discuss our work on network random lasers [1-3], which are made from an interconnected network of active photonic waveguides. The network lasers exhibit a rich multi-modal spectrum arising from structural disorder, which is highly sensitive to the pump illumination pattern due to nonlinear mode competition. We exploit this high sensitivity to control the lasing spectrum of the network laser by optimising the pump profile and for image classification, where the pump pattern is predicted from the lasing spectrum.

The network approach for a lasing cavity offers the flexibility to engineer modes via the network topology. I will discuss the design of a semiconductor network laser and the realisation of on-chip network lasers, which are fabricated on bonded Indium Phosphide (InP). These lasers have low lasing thresholds with good emission stability under prolonged pumping, which is essential for practical applications.

[1] Gaio, M. et al. A nanophotonic laser on a graph. Nat. Comm. 10, 226 (2019).
[2] Saxena, D. et al. Sensitivity and spectral control of network lasers. Nat. Comm. 13, 6493 (2022).
[3] Saxena, D. et al. Designed semiconductor network random lasers. Submitted (2024).