Unidirectional propagation of the Bloch surface wave excited by the spinning magnetic dipole in two-dimensional photonic crystal slab

Abstract

The photonic spin Hall effect (PSHE) can be realized in a photonic crystal (PC) slab, that is, the unidirectional Bloch surface wave can propagate along the surface of the PC slab under the excitation of elliptical polarized magnetic dipole. It is further proved that PSHE is caused by the interference of the component surface waves excited by the different components of the incident light, which is the so called component wave interference (CWI) theory. In addition, we also find that the spin of the surface wave oscillates periodically in space, and the oscillation period is a unit cell. In a unit cell, the average spin keeps the spin orbit locked. The results show that the spin separation can also be modulated by the position and the polarization state of the magnetic dipole.

Photonic spin Hall effect with high coupling efficiency in the combined structure of periodic dielectric waveguides and photonic crystal waveguide

“…From the view of CWI theory [13][14][15][16], the total field induced by the magnetic dipolar source in our configuration can be divided into two component fields, namely H x induced field and H y induced field. Figure 4 shows the E z field distribution excited by different source components, (a) for H x , (b) for H y .…”

“…Figure 1(b) shows the TM mode energy band structure of the PC calculated by plane wave expansion method [15] and figure 1(c) shows the dispersion relation of the PDW calculated by the FDTD scheme proposed as [21].The frequency and the wave vector are expressed as dimensionless ratios ωa/2π c and ka/2π respectively. According to figure 1(b), the first band gap is around 0.294 − 0.434 (ωa/2πc).…”

“…The most popular theoretical explanation for the mechanism of PSHE, proposed by Bliokh et al views the spin of the incident beam as the key factor of PSHE, which determines the exact photonic edge state to be excited and the exact direction the surface wave propagates along just like its QSHE counterpart [2,3,12]. More recently, a new interpretation called component wave interference (CWI) theory shows an alternative view, regarding the unidirectional propagation as the consequence of the interference between the spatial odd and even modes excited by different components of the incident beam [13][14][15][16]. This theory provides us with a direct and simple approach to analyze and manipulate PSHE, which we shall elaborate in detail in our later discussion.…”

Tunable propagation of waveguide mode by incident spin states in multi-channel metal waveguide

“…It shows important application prospects in the fields of optical communication, optical chip, optical device and so on. Analogous to the electric spin Hall effect (SHE), which characterizes the spin-dependent transport of electrons, the photonic counterparts is called photonic SHEs, this extraordinary effect offers the possibility to control the light flow by an elliptically polarized source [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. It is generally believed that spin-dependent unidirectional propagation and radiation have been attributed to the spin-momentum locking, the scattered light should have the same spin with that of incident beam, and then the propagation direction of scattered light can be determined according to the chirality.…”

“…In fact, the origin of the unidirectionality caused by spinmomentum locking is not accurate: because the system may participate in the exchange of angular momentum, when the incident light is scattered, the spin of the scattered light is not necessarily the same as that of the incident light. Recently, we propose the component wave interference (CWI) theory to reveal the origin of the unidirectionality [17][18][19][20], which is applicable not only to surface wave, but also to waveguide modes. Here, by considering the symmetry of the field excited by the composite electric and magnetic dipoles and using CWI theory, we provide a convenient and feasible method for realizing the selective propagation of light in multi-channel metal structures.…”