Resonant optical tunneling-induced enhancement of the photonic spin Hall effect

Abstract

Due to the quantum analogy with optics, the resonant optical tunneling effect (ROTE) has been proposed to investigate both the fundamental physics and the practical applications of optical switches and liquid refractive index sensors. In this paper, the ROTE is used to enhance the spin Hall effect (SHE) of transmitted light. It is demonstrated that sandwiching a layer of a highrefractiveindex medium (boron nitride crystal) between two lowrefractiveindex layers (silica) can effectively enhance the photonic SHE due to the increased refractive index gradient and an enhanced evanescent field near the interface between silica and boron nitride. A maximum transverse shift of the horizontal polarization state in the ROTE structure of about 22.25 µm has been obtained, which is at least three orders of magnitude greater than the transverse shift in the frustrated total internal reflection structure. Moreover, the SHE can be manipulated by controlling the component materials and the thickness of the ROTE structure. These findings open the possibility for future applications of photonic SHE in precision metrology and spinbased photonics.

Limitations of the transmitted photonic spin Hall effect through layered structure

“…Formally, these two formulae are closest to the expressions in Ref. [10] and Ref. [23], except that the last term of the denominator is , ⋅ , * rather than (…”

“…6 of Ref. [10], except the thickness of the boron nitride (BN). Figs.6(a), (b) and (c) show the transmission ratios, phase differences and transverse shifts varying with the incident angle for different thicknesses of the BN.…”

“…Thus, to promote its application, exploring enhanced photonic SHE has become especially necessary. In recent years, numerous measures focusing on various resonant structural designs to enhance the photonic SHE have been proposed, including surface plasmon resonance (SPR) 7 and long range SPR excitation structures 8 , photon tunneling 9 and resonant optical tunneling effect (ROTE) structures 10 , frustrating total internal reflection (FTIR) structures 11 , bound states in the continuum (BICs) structures 12 , graphene/MoS 2 heterostructures 13 , metasurfaces 14 , etc. On the other hand, various unconventional materials have also been proposed to enhance the SHE, including epsilon-near-zero (ENZ) materials 15 , anisotropic ENZ 16 and lossy ENZ 17 , hyperbolic metamaterials 18,19 , anisotropic metamaterials 20 , graphene [21][22][23] and black phosphorus 24 , polymers 25 , topological insulators 26 , and so on.…”

“…Besides, it is known that the Fresnel transmission coefficients play a vital role on the photonic SHE. In many works, the authors made efforts to improve the Fresnel transmission ratio to increase the spatial splitting 10,15,23,30 . Another question then arises: Does an increase in the ratio of the Fresnel transmission coefficients really lead to an increase of the transverse shift?…”

Spin Hall Effect of Light with Near‐Unity Efficiency in the Microwave

“…The enhancement of SHEL in most of the previous proposals and demonstrations has relied on small transmission/reflection coefficients, which in turn yield extremely low efficiency. [ 28,30,31,36–40 ] A system that supports a large transverse shift with high efficiency has remained elusive. It is contrast to studies on other spin–orbit associated phenomena, which have paid much attention on efficiency.…”