Designing and Measuring Novel Van der Waals Semiconductor Photonic Devices

Abstract

Semiconductor photonic devices enable efficient optical communication using light for fast transmission and detection of information. Conventional photonic devices primarily use group III-V semiconductors. However, these devices have limited integrability with silicon-based circuits, are bulky, and it is challenging to engineer their fundamental properties. Van der Waals (vdW) semiconductors are good candidates for the next generation of devices because they are atomically thin and feature strong emission, making them easy to integrate and efficient. Furthermore, they enable engineering of optical, electrical, and structural properties through formation of heterostructures and moir'{e} superlattices.

We design and create novel photonic devices by leveraging the optical tunability of vdW semiconductors. Our transferrable distributed Bragg reflector (DBR) cavity has a high quality factor, can strongly couple with vdW materials, and constructed using cavity fabrication methods that are robust and reliable. The DBR cavity coupled with hexagonal boron nitride (hBN) encapsulated monolayer MoSe$_{2}$ forms strongly coupled exciton-polaritons.

To further study photonic devices with vdW heterobilayers, we design and create the first WSe$_{2}$/MoSe$_{2}$ heterostructure laser and perform rigorous power dependence and first-order spatial coherence measurements to ensure lasing. The device shows a non-linear increase of the output intensity, linewidth narrowing, and a formation of extended spatial coherence, signifying lasing. Lastly, we study electrically controlled and cavity coupled WS$_{2}$}/MoSe$_{2}$ hybrid excitons to better understand the exciton-cavity coupling mechanism. Together, this improved understanding of vdW cavities and heterostructures sets the stage for designable photonic technologies and allows exploration of novel physics.