A hexagonal boron nitride super self-collimator for optical asymmetric transmission in the visible region

The two-dimensional (2D) hexagonal boron nitride (hBN) has been considered as a promising platform for quantum computing and information processing, due to the possibility in the generation of optically stable, ultra bright quantum emitters in the visible region. In the meantime, integrable optical asymmetric transmission devices are necessary for functional quantum computing chips. In this study, we theoretically demonstrate an optical asymmetric transmission device working in the visible region based on a monolith 2D hBN super self collimator. To maximize the self-collimation effect on improving the efficiency of the forward transmission, we not only design the photonic crystal structure with strong self-collimation characteristic, but also engineer the shape of the device. It is shown that by combining the two factors, the super self-collimation effect allows achieving a forward transmittance of up to 0.77. In the meantime, the structure effectively suppresses the backward transmission (down to 0.05) based on the directional bandgap, which results in a contrast ratio of up to 0.95 in the visible wavelength range of 590 nm-632 nm. More importantly, it is shown that by using the super self-collimation effect, the propagation efficiency inside the structure can be as high as 0.99 with minimum loss. Our results open up new possibilities in designing new nanophotonic devices based on 2D hBN for quantum computing and information processing. ABSTRACT The two-dimensional (2D) hexagonal boron nitride (hBN) has been considered as a promising platform for quantum computing and information processing, due to the possibility in the generation of optically stable, ultra bright quantum emitters in the visible region. In the meantime, integrable optical asymmetric transmission devices are necessary for functional quantum computing chips. In this study, we theoretically demonstrate an optical asymmetric transmission device working in the visible region based on a monolith 2D hBN super self collimator. To maximize the self-collimation effect on improving the efficiency of the forward transmission, we not only design the photonic crystal structure with strong self-collimation characteristic, but also engineer the shape of the device. It is shown that by combining the two factors, the super self-collimation effect allows achieving a forward transmittance of up to 0.77. In the meantime, the structure effectively suppresses the backward transmission (down to 0.05) based on the directional bandgap, which results in a contrast ratio of up to 0.95 in the visible wavelength range of 590 nm-632 nm. More importantly, it is shown that by using the super self-collimation effect, the propagation efficiency inside the structure can be as high as 0.99 with minimum loss. Our results open up new possibilities in designing new nanophotonic devices based on 2D hBN for quantum computing and information processing.