One-way edge modes in a photonic crystal of semiconductor at terahertz frequencies

Lingjuan He,Yun You,Linfang Shen,Xiaohua Deng,Tianbao Yu,Qian Shen,Jie Xu

doi:10.1038/s41598-018-26395-4

Lingjuan He, Yun You + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-26395-4

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Abstract

Electromagnetic edge mode in a photonic crystal (PhC), which is a square array of semiconductor rods in air, is theoretically investigated for terahertz frequencies. In the PhC, gyroelectric anisotropy is introduced in the semiconductor rods by applying an external magnetic field and consequently, a degeneracy point, at which two dispersion surfaces intersect, is lifted and a new band gap is created. The edge mode sustained by the PhC possesses the character of one-way propagation, and it even can be immune to backscattering at large defect on the wavelength scale and 90° sharp bend. The properties of the one-way mode are closely dependent on the cladding layer structure of the PhC.

Highlights

One-way electromagnetic (EM) edge modes were first proposed by Raghu and Haldan as analogues of quantum Hall edge states[1,2,3]
As the frequencies of band gaps in a photonic crystal (PhC) generally scale as the inverse of the lattice constant[7], the frequency range of one-way EM edge mode in PhCs can be flexibly tailored by properly choosing the lattice constant
The slope of the dispersion curve is always positive, the edge mode only propagate forward. This one-way edge mode covers a region larger than the PhC band gap, which is created by the external magnetic field

Summary

Physical Model

The photonic crystal under our consideration consists of a square array of semiconductor rods in air, as shown in the inset of Fig. 1(a). The slope of the dispersion curve is always positive, the edge mode only propagate forward This one-way edge mode covers a (frequency) region larger than the PhC band gap, which is created by the external magnetic field. Dissipation in the InSb rods, as shown, where the solid and dotted lines correspond to the electric-field amplitudes on the central line of the air layer for the cases without and with obstacle, respectively. The material losses can be compensated by introducing optical gain[27,28]

Influence of the Cladding Layer

Conclusion

Findings

Additional Information