Design of one-dimensional magnetophotonic crystals operating at visible wavelengths

In this paper, a proposal for designing the one-dimensional magnetophotonic crystals operating at visible wavelengths is presented. To this aim, a binary all-dielectric periodic structure is considered with quarter wavelength optical thicknesses condition. However, the Bi:YIG as a magneto-optical defect layer with two different optical thicknesses of λ0/ 2 and 4λ0 is utilized. Using the 4 × 4 transfer matrix method the defect mode properties of the considered structures are investigated regarding the different period numbers and various magneto-optical defect layer positions. Analyzing the transmittance, Faraday rotation and absorption coefficient of these structures for the 720 nm visible light, the optimum structures are proposed for both cases of magneto-optical defect layer thicknesses. These structures may have potential applications in designing the miniaturized magneto-optical devices such as magneto-optical sensors and isolators and integrated photonic elements

The effect of optical dispersion on magneto-optical responses of single-cavity and dual-cavity magnetophotonic crystals at near infrared wavelengths

In this paper the magneto-optical responses of single-cavity and dual-cavity type one-dimensional magnetophotonic crystals have been investigated considering the constituent layers optical dispersion in near infrared region. The 4 × 4 transfer matrix method has been utilized for calculations and analysis. The obtained results revealed that the resonance transmittance mode is split into two separated modes for specific repetition numbers. These modes are shifted toward the center of photonic band gap regarding the stronger dispersion relations, in both single- and dual-cavity structures. But the amounts of the shifts and their fine behavior are strongly dependent on the type of the structure. We believe that the results of the present work would be practically helpful to precisely design the miniaturized magneto-optical elements in micro- and nano-scale

Terahertz Vibrational Fingerprints Detection of Molecules with Particularly Designed Graphene Biosensors

In this research, an arc I-shaped graphene sensing structure with multi-resonance characteristics is proposed for the simultaneous detection of vibrational fingerprints with spectral separation in the terahertz range. The resonant frequencies of the sensor can be dynamically tuned by changing the gate voltage applied to the graphene arrays. The two vibrational fingerprints of lactose molecules (0.53 THz and 1.37 THz) in the transmission spectrum can be enhanced simultaneously by strictly optimizing the geometrical parameters of the sensor. More importantly, these two resonant frequencies can be tuned precisely to coincide with the two standard resonances of the lactose molecule. The physical mechanism of the sensor is revealed by inspection of the electric field intensity distribution, and the advantage of the sensor, which is its ability to operate at a wide range of incident angles, has been demonstrated. The sensing performance of the structure as a refractive index sensor has also been studied. Finally, a double arc I-shaped graphene sensor is further designed to overcome the polarization sensitivity, which demonstrates excellent molecular detection performance under different polarization conditions. This study may serve as a reference for designing graphene biosensors for molecular detection