New design for on-chip integrated photonic circuits proposed

The rapid development of broadband communication networks has led to a high demand for large-scale integration of photonic devices. Integrated photonic circuits (IPCs) are ideally made from silicon platforms with complementary metal-oxide-semiconductor (CMOS) technology. The speed of data processing is currently limited by the transmission speed of connectors in these devices.

The current state of technology in the field was reviewed and new types of on-chip IPCs that would use heterostructures involving hexagonal boron nitride (hBN) as an insulator combined with other two-dimensional (2D) materials were proposed. The authors reviewed a variety of applications involving 2D materials and layers of hBN, nano-lasers, LEDs, optical modulators and photodetectors, as well as full IPCs.

An example of the proposed use of hBN in an optical modulator is shown in the accompanying figure. The system involves a three-layer heterostructure within an hBN disk cavity. The heterostructure consists of a dielectric layer of aluminum oxide sandwiched between two graphene layers. Since the graphene layers are integrated in the middle of the cavity, they receive a larger wave guide optical energy density than they would if integrated on the cavity surface. The modulator is connected to silicon-based transistors through metal connectors on the silicon chip. This design should lead to practical applications of IPCs.

Other hBN-based designs are proposed in this work for a variety of devices, including laser diodes and photodetectors. Optical devices can, in principle, be linked by hBN optical waveguides to form on-chip IPCs. Practical realization, though, requires the ability to grow large area transition metal dichalcogenides and hBN on a silicon platform, so further research is needed.

Source: “On-chip integrated photonic circuits based on two-dimensional materials and hexagonal boron nitride as the optical confinement layer,” by Tianhua Ren and Kian Ping Loh, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5096195 .