We study graphene on a photonic crystal operating in the terahertz (THz) spectral range. We show that the absorption of graphene becomes a modulated function of frequency and can be enhanced by more than three times at specific frequency values, depending on the parameters of the system. The problem of a semi-infinite photonic crystal is also solved.

Enhancing the absorption of graphene in the terahertz range

Optical bistable and multistable phenomena in aperiodic multilayer structures with graphene

Wavelength-adjustable dual-band absorber has a potential impact on photonic circuits. While such devices are designed based on complicated structures, the use of a 2-D high-absorber MoS2 monolayer can alternatively simplify their design to a 1-D periodic structure. This article proposes photonic crystals with two defects as DMD to achieve dual narrowband defect modes, with M and D assumed to be the MoS2 and SiO2 layers, respectively. Thickness modulation, defect position, incident angle, and polarization of lights are investigated to find their impact on the absorption, wavelength, quality factor, full width half maximum (FWHM), depth of valley, and peak-to-peak distance of dual narrowband defect modes. This article shows that the wavelength of dual defect modes can be adjusted by the variation of distance of two defects with an absorption greater than 90%. The thickness of the D layer affects the depth of valley and wavelength of the defect modes while it has no influence on the peak-to-peak distance. Moreover, an increase in the incident angle leads to a systematic blueshift of the defect modes. The response of such structures can be systematically adjusted via various parameters to design dual narrowband wavelengths for application in photodetectors and photoluminescence and other optoelectronic devices.

Design of Wavelength-Adjustable Dual-Narrowband Absorber by Photonic Crystals With Two Defects Containing MoS 2 Monolayer

A defective Thue–Morse quasi-photonic crystal containing molybdenum disulfide (MoS2) is suggested to construct an ultra-narrowband multiple resonant absorber in the visible range. Multiple high absorption peaks can be achieved by altering the design of the proposed structure in different ways such as changing the generation number or the symmetry with respect to defect. Two structures are introduced, which create more than seven absorption peaks higher than 40% and one of the peaks about 100%. Defect modes' wavelength can be tuned to show the blue shift by incident angles and the polarization of light. Our optimal structures are useful for applications in multiplex filters and multiple channel sensors due to their high amount and narrowband absorption peaks and can show nearly perfect absorption.

Ultra-narrowband wavelength adjustable multichannel near perfect absorber in Thue–Morse defective quasi-photonic crystals embedded with MoS2 monolayer

A new route to designing a one-dimensional multiperiodic photonic crystal with adjustable photonic band gap and enhanced electric field localization

In recent years, two-dimensional materials such as MoS2 monolayers have attracted a lot of attention due to their high absorption. This study proposes the use of MoS2 monolayers as part of the defect in Fibonacci and Thue-Morse defective quasiphotonic crystals (DQPCs) to create an adjustable defect mode with relatively high absorption. The wavelength adjustability of the defect mode is investigated by parameters such as generation number, periodicity, and type of sequence used in DQPCs. The results revealed that using DQPCs can help enhance absorption and enables the adjustment of the defect mode as its generation number changes. Moreover, a Fibonacci DQPC generally requires much fewer layers in comparison to a Thue-Morse DQPC. To conclude, it is possible to achieve a wavelength-adjustable absorption of more than 90% with a Fibonacci DQPC.

Saeedeh Mohammadi

Papers

Approaching the nearly perfect and wavelength-adjustable absorption of MoS2 monolayer using defective quasi photonic crystals