Normal incidence filters using symmetry-protected modes in dielectric subwavelength gratings.
We investigate narrowband transmission filters based on subwavelength-grating reflectors at normal incidence. Computational results show that the filtering is realized through symmetry-protected mode coupling. The guided mode resonances introduced by the slab layer allow flexible control of the filter frequencies. The quality factor of the filters could exceed 106. Dielectric gratings can be used over the entire range of electromagnetic waves, owing to their scale-invariant operations. Owing to the high refraction index and low index dispersion of semiconductors in the infrared range, these filters can be applied over a broad range from near infrared to terahertz frequencies.
Department of Physics, Harbin Institute of Technology, Harbin 150001, China.
Xuan
X
Cui
Department of Physics, Harbin Institute of Technology, Harbin 150001, China.
Hao
H
Tian
Department of Physics, Harbin Institute of Technology, Harbin 150001, China.
Yan
Y
Du
Department of Physics, Harbin Institute of Technology, Harbin 150001, China.
Guang
G
Shi
Department of Physics, Harbin Institute of Technology, Harbin 150001, China.
Zhongxiang
Z
Zhou