Band Edge Effects and Normal Mode Propagation in Waveguide Magnetophotonic Crystals (original) (raw)
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Journal of Physics: Conference Series, 2019
In this work, a polarization-independent waveguide based on magnetic photonic crystal (MPC) with a triangular lattice of air holes in Yttrium Iron Garnet (YIG) slab grown on alumina (Al2O3) substrate is proposed, where both TE-like and TM-like periodic band gaps overlap. YIG is well known for its attracting magneto-optical (MO) properties and used to produce a coupling between the TE and TM modes. Thus, a nonreciprocal effect can be obtained by applying an external magnetic field parallel to the direction of propagation. At 1550 nm, the complete photonic band gap is simulated and optimized using the three dimensional plane-wave expansion method. The aim of this study is to enhance Faraday rotation (FR) while maintaining a low modal birefringence. A numerical analysis in function of magnetic gyration (g) has been reported, using the BeamProp software. The results reveal a proportional relation between FR, Δ n and g, such for g = 0.5, a large FR of 26.11×104 °/cm with Δ n = 7×10−6. Th...
Polarization degeneracy at Bragg reflectance in magnetized photonic crystals
Physical Review B, 2009
A study is presented of the band structure in one-dimensional photonic crystals with anisotropic and gyrotropic layers. It is predicted that magnetization of the structure in a direction normal to the plane of the layers causes the formation of an additional band gap of a new type. The phenomenon is caused by the Bragg resonance between harmonics of different polarization and stems from the hybridization of these harmonics. Though the application of a magnetic field generally results in degeneracy lifting, in anisotropic magnetophotonic crystals a magnetic field may actually induce polarization-degenerate Bragg reflections. Moreover, while in a nonmagnetized photonic crystal, the Bloch waves of different polarization may have noncoincident band edges, the band gaps predicted herewith are shared by the Bloch waves of any polarization. This allows the design of polarization-independent optical tuning devices. Thus the formation of these band gaps enables the magnetic control of arbitrarily polarized light.
Proceedings of Spie the International Society For Optical Engineering, 2008
We present a study of polarization rotation enhancement in birefringent magneto-optic photonic crystal waveguides and provide theoretical and experimental support for a novel type of photonic bandgap. The coupling between counter-propagating elliptically birefringent local normal modes of different order results in the formation of partially overlapping bandgaps and selective suppression of Bloch state propagation near the band edges. We use a bilayer unit cell stack model with an alternating system of birefringent states in adjacent layers. A magnetically tunable and large polarization rotation of the allowed Bloch modes near the band edges is computed theoretically and observed experimentally.
Magneto-optical properties of photonic crystals
Journal of the Optical Society of America B, 2005
Magneto-optical properties of photonic crystals (or bandgap materials) have been examined with respect to their possible applications for the control of electromagnetic radiation in integrated-optics devices. Theoretical studies of one-dimensional photonic crystals were conducted on the basis of the transfer-matrix method. For investigation of two-and three-dimensional photonic crystals we propose the original theoretical approach based on perturbation theory. Magneto-optical Faraday and Voigt effects have been studied near extremum points of photonic bands where their significant enhancement takes place. On the basis of the theory elaborated some experimental results are discussed. Experimentally obtained Faraday-rotation-angle-frequency dependence shows good agreement with our theoretical analysis.
Physical Review B, 2011
This study examines photonic stop band reconfiguration upon magnetization reversal in multimode elliptically birefringent Bragg filter waveguides. Magnetization reversal in longitudinally magnetized magneto-optic waveguides affects the character of the local orthogonal elliptically polarized normal modes, impacting the filter's stop band configuration. Unlike the standard case of circular birefringence in magneto-optic media, opposite helicity states do not transform into each other upon magnetization reversal for a given propagation direction. Rather, helicity reversals yield new and different normal modes with perpendicularly oriented semimajor axes, corresponding to a north-south mirror reflection through the equatorial plane of the Poincaré sphere. For asymmetric contradirectional coupling between different-order waveguide modes in multimode magnetophotonic crystals, this symmetry breaking, namely, the obliteration of normal modes upon magnetization reversal, allows for strongly reconfigured stop bands, through the hybridization of the elliptically polarized states. The effect of Bloch mode reconfiguration on the stop band spectral profile contributes to the magnetic response of the filter. In such elliptically birefringent media, input polarization helicity reversal also becomes a powerful tool for optical transmittance control. Both magnetization and helicity reversals can thus serve as useful tools for the fabrication of on-chip magnetophotonic crystal switches.
Photonic Fiber and Crystal Devices: Advances in Materials and Innovations in Device Applications II, 2008
We present a study of polarization rotation enhancement in birefringent magneto-optic photonic crystal waveguides and provide theoretical and experimental support for a novel type of photonic bandgap. The coupling between counter-propagating elliptically birefringent local normal modes of different order results in the formation of partially overlapping bandgaps and selective suppression of Bloch state propagation near the band edges. We use a bilayer unit cell stack model with an alternating system of birefringent states in adjacent layers. A magnetically tunable and large polarization rotation of the allowed Bloch modes near the band edges is computed theoretically and observed experimentally.
2007
An analysis is presented of wave-vector dispersion in elliptically birefringent stratified magneto-optic media having one-dimensional periodicity. It is found that local normal-mode polarization-state differences between adjacent layers lead to mode coupling and impact the wave-vector dispersion and the character of the Bloch states of the system. This coupling produces extra terms in the dispersion relation not present in uniform circularly birefringent magneto-optic stratified media. Normal mode coupling lifts the degeneracy at frequency band cross-over points under certain conditions and induces a magnetization-dependent optical band gap. This study examines the conditions for band gap formation in the system. It shows that such a frequency-split can be characterized by a simple coupling parameter that depends on the relation between polarization states of local normal modes in adjacent layers. The character of the Bloch states and conditions for maximizing the strength of the band splitting in these systems are analyzed.
Journal of the Optical Society of America B, 2008
An analysis is presented of wave-vector dispersion in elliptically birefringent stratified magneto-optic media having one-dimensional periodicity. It is found that local normal-mode polarization-state differences between adjacent layers lead to mode coupling and impact the wave-vector dispersion and the character of the Bloch states of the system. This coupling produces extra terms in the dispersion relation not present in uniform circularly birefringent magneto-optic stratified media. Normal mode coupling lifts the degeneracy at frequency band cross-over points under certain conditions and induces a magnetization-dependent optical band gap. This study examines the conditions for band gap formation in the system. It shows that such a frequency-split can be characterized by a simple coupling parameter that depends on the relation between polarization states of local normal modes in adjacent layers. The character of the Bloch states and conditions for maximizing the strength of the band splitting in these systems are analyzed.
Journal of Magnetism and Magnetic Materials, 2010
Control of magnetization is central to the performance of magneto-optical switches and isolators. Photonic crystal technology on these devices can yield significant improvements in polarization rotation efficiency and an overall reduction in device dimensions. The optical response and field reversal characteristics of resonant magneto-optic polarization rotators fabricated on chip are presented herein and analyzed by micromagnetic simulation. By introducing domain-strip structures into the resonant cavity of Bragg gratings formed on magnetic garnet films, a bi-stable magnetic state is demonstrated and the enhancement of characteristic saturation field is studied. Domain closure loops between the strips affect the hysteresis response in the resonant cavity. Large magneto-optic rotations exceeding 451 are produced near resonance between 1500 and 1580 nm in the stop-bands, although the presence of linear birefringence in these gyrotropic waveguides strongly suppresses the Faraday rotation outside the stop-bands and degrades the linearity of the output polarization.
Enhancement of the Faraday and Other Magneto-Optical Effects in Magnetophotonic Crystals
Springer Series in Materials Science, 2013
It is shown that for existent natural materials the Faraday rotation is far below the theoretical limit [Steel et al. in J. Lightwave Technol. 18:1297, 2000]. Under this condition the value of the Faraday rotation is primarily determined by the Q-factor, while the low group velocity value, multipass traveling and energy concentration in magneto-optical material play a secondary role. A comparative analysis of the efficiency of different schemes employing defect modes, Tamm surface states, the Borrmann effect and plasmon resonance is presented.