The scientific community has witnessed the tremendous expansion of research on layered (i.e., two-dimensional, 2D) materials, with an increasing recent focus on photonics applications. Layered materials are particularly exciting for manipulating light (tunable optical properties) in the confined geometry of photonic integrated circuits. Key material properties include strong and controllable light-matter interaction and limited optical loss.
Layered and two-dimensional materials, such as graphene, transition metal dichalcogenides, and hexagonal boron nitride, have unique optical properties that can be exploited for integrated photonics. These materials can modulate light by changing their refractive index, absorption, or emission in response to external stimuli, such as electric fields, strain, or temperature. Moreover, they can be integrated with conventional photonic platforms, such as silicon or silicon nitride, to create hybrid devices with enhanced functionality and performance. Refractive uses of layered and two-dimensional materials for integrated photonics, focus on modulators, switches, sensors, lasers, and nonlinear optics.
Layered materials feature tunable optical properties, promising phases for electro-optics, and a panoply of polymorphs that suggest a rich design space for highly nonperturbative photonic integrated devices based on phase-change functionality.
All of these features are manifested in materials with a bandgap above the photonics-relevant near-infrared (NIR) spectral band (∼ 0.5–1 eV), meaning that they can be harnessed in refractive (i.e., nonabsorptive) applications.