Nanoscale grating traps infrared light for smaller photonic devices
The molybdenum diselenide structure reportedly confines infrared light in a 40nm-thick layer.
The team, led by the Faculty of Physics at the University of Warsaw, Poland, has created the sub-wavelength grating, which consists of closely spaced parallel strips that interact with light.
The researchers explain that because molybdenum diselenide has a higher refractive index, it slows light more strongly – this enables a thinner structure that traps light efficiently.
Conventional gratings made from silicon or gallium-based materials normally need to measure several hundred nanometres thick to effectively trap light.
The material is also said to show strong nonlinear optical behaviour. By concentrating infrared light inside the grating, it enhances third harmonic generation – a process that converts three infrared photons into one higher-frequency visible blue photon – by more than 1,500 times, compared with a flat layer of the same material.
The film was grown using molecular beam epitaxy, producing uniform layers across several square inches, which could make the approach practical for future photonic integrated circuits.
