Search Results (25)

An intensity-demodulated fiber-optic magnetometer is proposed and experimentally investigated, which is fabricated via fusion splicing a segment of photonic crystal fiber (PCF) between single-mode fibers (SMFs), with the cladding air holes of PCF filled with magnetic fluid. Using the magneto-optical properties of the magnetic fluid, the transmission spectrum is changed with an external magnetic field. Based on the intensity variations in the transmission spectrum, the magnetic field is detected, and a sensitivity of 0.238 dB/mT is obtained at 1550.03 nm with the length of PCF 5.5 cm. By converting light signals into electrical signals, a sensitivity of 0.003 V/mT is achieved. The fiber-optic magnetometer possesses the advantages of simple fabrication, compact/robust structure, and low cost. Full article

The phenomena of magneto-optical polarization rotation and circular magnetic dichroism are well known in the Faraday configuration. We present another effect, an odd magneto-optical linear dichroism, arising in nanostructures with polarization-dependent mode Q-factors and magneto-optical components. It reveals itself as the magneto-optical modulation of light intensity for the two opposite magnetization directions in the Faraday configuration. The effect was demonstrated on a magnetophotonic crystal with a cavity mode, the polarization-dependent Q-factor of which is due to oblique incidence. For a polarization angle of 60° (or 120°) and an angle of incidence around 60°, the magneto-optical intensity modulation maximizes and reaches 6%. Full article

We investigate how an external magnetic field with an arbitrary direction affects the photonic band of a superlattice structure composed of alternating dielectric and magneto-optical plasma layers. By considering that the superlattice is electrodynamically anisotropic in the presence of an external magnetic field, we derive the dispersion equations; we show that the photonic spectrum of this superlattice loses its degeneracy and splits into two branches due to the external magnetic field. Interestingly, our results indicate that a superlattice that was previously wholly photo-isolating can become entirely photo-conducting, regardless of the direction of the external magnetic field applied. These results could be helpful to design and build new optical diode-like devices. Full article

In this paper, a terahertz circulator based on a magneto photonic crystal slab is envisaged. The triangular lattice photonic crystals with a line defect waveguide were constructed on an Al₂O₃ ceramic slab. Two cylindrical ferrites and two copper-clad plates in the junction of the Y-shaped wave-guide worked as a magneto-optical cavity resonator to approve the nonreciprocal function. In the working frequency range, 0.212–0.238 THz, the isolation of the circulator was better than 20 dB, and the insertion loss was better than 1 dB. The designed circulator based on the magneto photonic crystal slab experienced low loss and a wide bandwidth that satisfied its use in the THz application. Full article

We theoretically and numerically investigate magnetophotonic microresonators formed by a magnetic layer sandwiched between two reflective multilayers with different layer arrangements. Quasicrystals with the Fibonacci layer sequence and aperiodic structures with the Thue–Morse sequence are all compared to the conventional photonic crystal Bragg microresonators. The magneto-optical spectral properties of such magnetophotonic structures are completely different from each other and from a uniform magnetic film. In multilayered structures of various order types, microresonator modes are excited. The feature of multilayered structures with arrangements different from a periodic one is that they support the excitation of the multiple microresonator modes in a limited visible and near-infrared spectral range. The wavelengths of the two microresonator modes in a regular photonic crystal differ by more than one octave. This feature of the quasi-crystalline and aperiodic microresonators is important for applications in devices based on the Faraday effect. Full article

The magnetic nanomaterial Mn₃Si₂Te₆ is a promising option for spin-dependent electronic and magneto-optoelectronic devices. However, its application in nonlinear optics remains fanciful. Here, we demonstrate a pulsed Er-doped fiber laser (EDFL) based on a novel quasi-2D Mn₃Si₂Te₆ saturable absorber (SA) with low pump power at 1.5 μm. The high-quality Mn₃Si₂Te₆ crystals were synthesized by the self-flux method, and the ultrathin Mn₃Si₂Te₆ nanoflakes were prepared by a simple mechanical exfoliation procedure. To the best of our knowledge, this is the first time laser pulses have been generated using quasi-2D Mn₃Si₂Te₆. A stable pulsed laser at 1562 nm with a low threshold pump power of 60 mW was produced by integrating the Mn₃Si₂Te₆ SA into an EDFL cavity. The maximum power of the output pulse is 783 μW. The repetition rate can vary from 24.16 to 44.44 kHz, with corresponding pulse durations of 5.64 to 3.41 µs. Our results indicate that the quasi-2D Mn₃Si₂Te₆ is a promising material for application in ultrafast photonics. Full article

In this work, graphene oxide@Fe₃O₄ (GO@Fe₃O₄) two-dimensional magnetically oriented nanocomposites were prepared through the co-precipitation approach using graphene oxide as the carrier and FeCl₃·6H₂O and FeSO₄·7H₂O as iron sources. The samples were characterized and tested by X-ray diffraction, a transmission electron microscope, Fourier-transform infrared spectroscopy, a vibrating-specimen magnetometer, a polarized optical microscope, an optical microscope, etc. The effects of material ratios and reaction conditions on the coating effects of Fe₃O₄ on the GO surface were investigated. The stable GO@Fe₃O₄ sol system was studied and constructed, and the optical properties of the GO@Fe₃O₄ sol were revealed. The results demonstrated the GO@Fe₃O₄ two-dimensional nanocomposites uniformly coated with Fe₃O₄ nanoparticles were successfully prepared. The GO@Fe₃O₄ two-dimensional nanocomposites exhibited superparamagnetic properties at room temperature, whose coercive force was 0. The stable GO@Fe₃O₄ sol system could be obtained by maintaining 1 < pH < 1.5. The GO@Fe₃O₄ sol showed magneto-orientation properties, liquid crystalline properties, and photonic crystal properties under the influence of the external magnetic field. The strength and direction of the magnetic field and the solid content of the GO@ Fe₃O₄ sol could regulate the aforementioned properties. The results suggest that GO@Fe₃O₄ two-dimensional magnetically oriented nanocomposites have potential applications in photonic switches, gas barriers, and display devices. Full article

Glassy nanocomposites containing Yb³⁺/Er³⁺-doped GdF₃ and LiGdF₄ nanocrystals have been prepared by controlled crystallization of the xerogel and the structural, up-conversion luminescence, and magnetic properties were analyzed and discussed. Structural and morphological analysis showed uniform distribution of both GdF₃ and LiGdF₄ nanocrystals (tens of nm size), embedded in silica glass matrix as the result of thermal decomposition of the trifluoracetates, revealed as a strong exothermic peak at about 300 °C; the Li-ions co-doping showed a strong influence on the GdF₃ and LiGdF₄ nanocrystalline fraction. The energy dispersive spectrometry mapping showed Gd, F and Yb, Er within the nanocrystals but not in the silica glass matrix. X-ray diffraction pattern analysis indicated the crystalline lattice distortion consistent with the Yb/Er incorporation in both fluoride nanocrystals. The “green” ((²H_11/2, ⁴S_3/2) →⁴I_15/2) and “red” (⁴F_9/2→⁴I_15/2) up-conversion luminescences at 525, 545, and 660 nm observed under 980 nm laser light pumping were assigned to the Er³⁺ ions deexcitation through a two-photon process. The magnetic properties of the nanocomposite are strongly temperature dependent. The magnetization hysteresis loops show a ferromagnetic behavior at low temperatures (5K) related to the rare-earth ions contribution and the saturation magnetization of 39 emu/g. At 300 K a paramagnetic behavior was observed that was ascribed to the non-interacting localized nature of the magnetic moment of the rare-earth ions. Hence, such novel, multifunctional magnetic and optical materials can allow the intertwining between magnetism and photonics and might offer new opportunities for new magneto-optical device development. Full article

This paper proposed and investigated a sensor that could simultaneously measure temperature and magnetic fields. The key component of this sensor was a photonic crystal fiber with a length of only 1 cm, whose air holes were arranged in a circular lattice symmetry. In order to increase the birefringence of the fiber, we introduced well-designed point defects into the photonic lattice. The deficient pores were filled with a magneto-fluidic material (MF) that sensed temperature and magnetic fields through changes in its refractive index. The outer layer of the fiber cladding was coated with a thin film of Indium tin oxide (ITO), which was in direct contact with ethanol. The surface plasmon resonance created by ITO was used to achieve dual-parameter demodulation and solve the cross-sensitivity problem. The photonic crystal fiber and other optical components made up a Sagnac interferometer, which was used to measure the transmission spectrum of the Sagnac interference. At the same time, the loss spectrum due to the surface plasmon resonance was measured. The variation in temperature and magnetic field was directly related to the shift in the resonance wavelengths of the transmission and loss spectra, thus enabling simultaneous dual-parameter measurements. We investigated the sensing performance of the sensor numerically. The results showed a wavelength sensitivity of 7.6 nm/°C and 0.75 nm/mT, with a resolution of 1.316 × 10⁻³ °C and 1.333 × 10⁻³ mT for temperature and magnetic field, respectively. Compared with other sensors, the key component of the proposed sensor is only 1 cm in length, which makes it compact and easy to manufacture. The geometric parameters, such as the position and radius of the pores, are less likely to deviate from the ideal values, which helps to reduce the impact of manufacturing tolerances on the sensing performance. Full article

We designed magneto-electro-elastic piezoelectric, electromagnetic (EM) metamaterials (MEEPEM) by using a square lattice of the periodic arrays of conducting wires, piezoelectric photonic crystal (PPC), and split-ring resonators (SRRs). We analyzed the mechanism for multi-field coupling in MEEPEM. The magnetic field of the EM wave excites an attractive Ampère force in SRRs, which periodically compress MEEPEM, and this can create electric polarization due to the piezoelectric effect. The electric field of the EM wave can excite a longitudinal superlattice vibration in the PPC, which can also create electric polarization. The electric polarization can couple to the electric field of the periodic arrays of conducting wires. The coupled electric field will couple to the EM wave. These interactions result in multi-field coupling in MEEPEM. The coupling creates a type of polariton, called multi-field coupling polaritons, corresponding to a photonic band gap, namely, the multi-field coupling photonic band gap. We calculated the dielectric functions, the reflection coefficients, and the effective magnetic permeability of MEEPEM. By using them, we analyzed the transmission properties of EM waves in the MEEPEM. We analyzed the possibility of MEEPEM as left-handed metamaterials and zero refractive index material. Full article

We have studied the transmission properties of odd/even one-way modes and their reversible conversion in a double-channel waveguide consisting of two magneto-optical photonic crystals (MOPCs) sandwiched with Al₂O₃ PC. There exist two pairs of even and odd modes, i.e., M1(even)/M2(odd) or M3(odd)/M4(even) modes, for the double-channel waveguides with one- or two-stranded coupling layer of Al₂O₃ rods, respectively. Among them, the M1, M2, and M3 modes are caused by the weak coupling strength of two sub-waveguides, while the M4 mode results from the strong coupling effect and supports dispersionless slow-light propagation. Furthermore, we realize the reversible conversion between odd and even modes (i.e., between M1 and M2 modes, or M3 and M4 modes) in the one- or two-stranded structure, respectively, by adjusting the length and position of the perfect electric conductor (PEC) defect properly to cause the desired significant phase delay along the upper and lower equivalent transmission paths. Additionally, we find that the robustness of the M1 even mode is poor because of extra excitations of counter-propagation modes near the right Brillouin boundary, while the other three modes have extremely strong robustness against PEC defects and their one-way transmittances are nearly 100%. These results hold promise for many fields, such as slow-light modulation and the design of topological devices. Full article

Colloidal crystals (CCs) are periodic arrays of monodisperse microparticles. Such CCs are very attractive as they can be potentially applicable as versatile photonic devices such as reflective displays, sensors, lasers, and so forth. In this article, we describe a promising methodology for synthesizing monodisperse magnetite microparticles whose diameters are controllable in the range of 100–200 nm only by adjusting the base concentration of the reaction solution. Moreover, monodisperse magnetite microparticles in aqueous suspensions spontaneously form the CC structures under an external magnetic field, leading to the appearance of Bragg reflection colors. The reflection peak can be blue-shifted from 730 nm to 570 nm by the increase in the external magnetic field from 28 mT to 220 mT. Moreover, the reflection properties of CCs in suspension depend on the microparticle concentration in suspension and the diameter of the magnetite microparticles. Both fine-control of microparticle diameter and investigation of magneto-optical properties of CCs would contribute to the technological developments in full-color reflective displays and sensors by utilizing these monodisperse magnetite microparticles. Full article

A three-port circulator for optical communication systems comprising a photonic crystal slab made of a magneto-optical material in which an magnetizing element is not required to keep its magnetic domains aligned is suggested for the first time. By maximizing the incorporation of europium to its molecular formula, the magneto-optical material can remain in the saturated magnetic state even in the absence of an external DC magnetic field. Two- and three-dimensional simulations of the device performed with full-wave electromagnetic solvers based on the finite element method demonstrate that, at the 1550 nm wavelength, the insertion loss, isolation, and reflection levels are equal to or better than −1 dB, −14 dB, and −20 dB, respectively. Since its operation does not require an electromagnet or a permanent magnet, the suggested circulator is much more compact, being able to reach footprints in the range of three orders of magnitude smaller, when compared to other circulator designs referred to in the literature and the presented results can be useful for the design of other nonreciprocal devices with reduced dimensions for optical communication systems. Full article

Search for new types of efficient magnetoplasmonic structures that combine high transparency with strong magneto-optical (MO) activity is an actual problem. Here, we demonstrate that composite heterostructures based on thin perfectly-arranged opal films and a perforated cobalt nanolayer meet these requirements. Anomalous transmission appears due to periodic perforation of Co consistent with the regular set of voids between opal spheres, while resonantly enhanced MO response involves the effects of surface plasmon-polariton (SPP) excitation at opal/Co interface or those associated with photonic band gap (PBG) in opal photonic crrystals. We observed the enhancement of the MO effect of up to 0.6% in the spectral vicinity of the SPP excitation, and several times less strong effect close to the PBG, while the combined appearance of PBG and SPP decreases the resultant MO response. Observed resonant magneto-optical properties of opal/Co heterostructures show that they can be treated as functional self-assembled magnetoplasmonic crystals with resonantly enhanced and controllable MO effect. Full article

We propose an all-dielectric magneto-photonic crystal with a hybrid magneto-optical response that allows for the simultaneous measurements of the surface and bulk refractive index of the analyzed substance. The approach is based on two different spectral features of the magneto-optical response corresponding to the resonances in p- and s-polarizations of the incident light. Angular spectra of p-polarized light have a step-like behavior near the total internal reflection angle which position is sensitive to the bulk refractive index. S-polarized light excites the TE-polarized optical Tamm surface mode localized in a submicron region near the photonic crystal surface and is sensitive to the refractive index of the near-surface analyte. We propose to measure a hybrid magneto-optical intensity modulation of p-polarized light obtained by switching the magnetic field between the transverse and polar configurations. The transversal component of the external magnetic field is responsible for the magneto-optical resonance near total internal reflection conditions, and the polar component reveals the resonance of the Tamm surface mode. Therefore, both surface- and bulk-associated features are present in the magneto-optical spectra of the p-polarized light. Full article