The photonic bandgap and localization in photonic crystals can be effectively modulated by energetic ion beams owing to the induced modification of the thickness and refractive indices of the materials. In this work, the modulation of photonic bandgap and defect modes in 1D all‐dielectric photonic crystals is investigated theoretically and experimentally by using carbon (C5+) ion irradiation. It is found that the photonic bandgap and defect mode have a remarkable hypsochromic shift under the C5+ ion irradiation. The degree of the blueshift mainly depends on the reduction of the material thickness that is nearly proportional to the fluences of C5+ ions. The blueshift of the band edges and defect modes shows a step‐like behavior from transparency to opacification (near‐zero transmittance or high reflectance) or a converse trend. The work paves a new way to tailor the photonic crystals toward the development of novel devices with tunable specific wavelengths and wavebands.
In this study, we theoretically and experimentally investigated the perfect optical absorptance of a photonic heterostructure composed of a truncated all-dielectric photonic crystal (PC) and a thick metal film in the visible regions. The three simulated structures could achieve narrow-band perfect optical absorption at wavelengths of 500 nm, 600 nm, and 700 nm, respectively. Based on the measured experimental results, the three experimental structures achieved over 90% absorption at wavelengths of 489 nm, 604 nm, and 675 nm, respectively. The experimental results agreed well with the theoretical values. According to electromagnetic field intensity distributions at the absorption wavelengths, the physical mechanism of perfect absorption was derived from the optical Tamm state (OTS). The structure was simple, and the absorption characteristics were not significantly affected by the thickness of the thick metal layer, which creates convenience in the preparation of the structure. In general, the proposed perfect absorbers have exciting prospects in solar energy, optical sensor technology, and other related fields.
We theoretically and experimentally investigate the angle-dependent omnidirectional photonic bandgap (PBG) in one-dimensional photonic crystals (PCs) comprising hyperbolic metamaterials (HMMs) for TM polarization, which is different from blue-shifted PBG in conventional all-dielectric photonic crystals. The frequency range of PBG increases when the incident angles increase, owing to the red-shift and blue-shift of the long-wavelength and short-wavelength band edges, respectively. The red-shifted band edge originates from the phase-variation compensation mechanism between the HMMs and dielectric material. The experimental values are in good agreement with the simulation results. These nanostructures are ideal for fabricating photonic devices such as omnidirectional reflectors.
This paper presents dual-band high-gain subwavelength cavity antennas with artificial magnetic conductor (AMC) metamaterial microstructures. We developed an AMC metamaterial plate that can be equivalent to mu-negative metamaterials (MNMs) at two frequencies using periodic microstructure unit cells. A cavity antenna was constructed using the dual-band AMC metamaterial plate as the covering layer and utilizing a feed patch antenna with slot loading as the radiation source. The antenna was fabricated with a printed circuit board (PCB) process and measured in an anechoic chamber. The |S11| of the antenna was −26.8 dB and −23.2 dB at 3.75 GHz and 5.66 GHz, respectively, and the realized gain was 15.2 dBi and 18.8 dBi at two resonant frequencies. The thickness of the cavity, a sub-wavelength thickness cavity, was 15 mm, less than one fifth of the long resonant wavelength and less than one third of the short resonant wavelength. This new antenna has the advantages of low profile, light weight, dual-frequency capability, high gain, and easy processing.
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