Yttrium Iron Garnet Rods Research Articles

Mode conversion and separation in magneto-optical photonic crystal waveguide.

We present mode conversion in different magneto-optical photonic crystal (MOPC) waveguides. An odd-mode waveguide (OMW) and an even-mode waveguide (EMW) are designed by adjusting the geometric parameters of the waveguide. These waveguides are constructed by adding a layer of yttrium-iron-garnet (YIG) rods with opposing magnetic fields between an MOPC and an Al2O3 photonic crystal (PC). Due to the coupling effect caused by the middle layer of YIG rods, the OMW (or EMW) only supports an odd (or even) mode within a single-mode frequency range. Simulation results demonstrate that they can convert other modes into odd or even modes, and there is almost no power loss during the conversion. Most importantly, they are robust against backscattering from perfect electric conductors (PECs) and point defects. Based on these properties, we propose a device that can efficiently separate the odd and even modes into different ports. These results offer a novel approach to controlling the transmission modes of waveguides, which facilitates the interconnection of diverse topological magneto-optical waveguides.

Transmission Properties in Plasma Photonic Crystal Controlled by Magnetic Fields

The transmission properties in two-dimensional plasma photonic crystal composed of plasma and yttrium–iron–garnet rods with square lattices are demonstrated under different electron densities and external magnetic fields. The TE and TM modes respond to the permittivity tensor and the permeability tensor produced by the magnetic field. For TM polarization, two distinct attenuation peaks appear in the ranges of 3.4–3.62 GHz and 3.78–4 GHz, induced by the external magnetic fields, and the location of these attenuation peaks can be modulated by modifying the electron densities. For TE polarization, a flat transmission spectrum was obtained in the range of 4–4.6 dB by increasing the electron density to 3×1012 cm−3. Then, a Y-shaped plasma photonic crystal waveguide is designed. The transmission path can be modulated by changing the direction of the external magnetic field. By regulating the electron density, switching the Y-shaped waveguide on and off can be achieved.

Optical waveguide switch through magnetic reflectance wall

We propose a new design to achieve optical waveguide switch. We construct a photonic crystal waveguide with one yttrium iron garnet (YIG) rod array on the two sides of the waveguide. Through the mode analysis, we find in special frequency range a few YIG rods under magnetic field can form the magnetic reflectance wall that blocks the light flow. Removing the magnetic field will delete the reflection wall and let the blocked light to be switched on.

Experimental demonstration of tunable negative phase velocity and negative refraction in a ferromagnetic/ferroelectric composite metamaterial

A tunable left-handed transmission is demonstrated experimentally in a ferromagnetic/ferroelectric composite metamaterial (CMM) consisting of an array of yttrium iron garnet (YIG) rods combined with barium strontium titanate (BST) rods. We observed a passband in the CMM within the overlap of the stop bands of YIG rods alone and BST rods alone. Both measured phase velocity and refractive index of the CMM are shown to be negative at the relevant frequency range. The frequency showing left handedness can be adjusted continuously, dynamically, and reversibly by an applied magnetic field with a sensitive response of 3.5 GHz/kOe.

Magnetically tunable negative permeability metamaterial composed by split ring resonators and ferrite rods

We experimentally demonstrate a tunable negative permeability metamaterial (NPM) at microwave frequencies by introducing yttrium iron garnet (YIG) rods into a periodic array of split ring resonators (SRRs). Different from those tuned by controlling the capacitance of equivalent LC circuit of SRR, this metamaterial is based on a mechanism of magnetically tuning the inductance via the active ambient effective permeability. For magnetic fields from 0 to 2000 Oe and from 3200 to 6000 Oe, the resonance frequencies of the metamaterial can blueshift about 350 MHz and redshift about 315 MHz, respectively. Both shifts are completely continuous and reversible. Correspondingly, the tunable negative permeabilities are widened by about 360 MHz and 200 MHz compared to that without YIG rods.

An improved two-port Magnetoelastic delay line

Abstract-A new form of linearly dispersive microwave delay line is described, in which fine-wire transducers are mounted directly inside a magnetically saturated rod of yttrium iron garnet (YIG), through small diameter holes laser drilled in the rod. The delay Iine operates by utilizing the magnetoelastic interaction between spin waves and elastic waves with frequency dispersion controlled by a special nonlinear axial magnetic field profiie synthesized by an appropriate pole piece geometry. Principal features include: physical separation between the input and output signals; longer delays than in the traditional "single ended" delay line because the waves spend a longer time in the elastic domain; no acoustic reflections at the ends of the rod and good coupling between the antennas and the material. Measurements made on the fist designed YIG delay line of this type are reported. Results agree with theoretical predictions. It has been possible to delay a 10 ns pulse of 1200 ns over the range 3.2-3.4 GHz with an insertion loss of 31 dB.

FREQUENCY CONVERSION OF SPIN WAVES IN PULSED MAGNETIC FIELDS

Pulsed frequency conversion of magnetostatic modes in an axially magnetized 〈100〉 rod of yttrium iron garnet has been observed experimentally. Both upward and downward shifts from 20 MHz to 900 MHz for input frequencies between 1 and 3 GHz have been achieved. Theoretical frequency conversion and power gain are obtained from energy and momentum considerations.

Magnetoelastic Waves in Yttrium Iron Garnet

Magnetoeleastic pulses with variable echo time were observed in a rod of yttrium iron garnet. Data were taken at room temperature in the frequency interval 0.5 to 3.3 Gc/sec with input power in the milliwatt range. At a fixed carrier frequency, pulses were observed for external magnetic fields ranging over several hundred oersted; characteristically the echo time increased with decreasing field. The carrier frequency-magnetic field-echo time behavior can be explained in terms of a θ=0 magnetoelastic disturbance traveling along the rod axis. It is launched at the position where ωc=γHi. The disturbance propagates along the rod axis to the nearer end-face where it is reflected. On arrival back at the launch site, a fraction of the energy is detected and the remainder reflected for another round trip. The process is repeated several times to give rise to a pulse sequence. The experimental results can be understood in terms of a magnetoelastic wave packet with calculated travel time T=∫um−1dz≈∫us−1dz+∫ue−1dz, where the group velocities, u, refer to magnetoelastic, spin, and elastic waves, respectively. Spin-wave loss has been included and gives improved agreement between theory and experiment.

Magnetoelastic Waves in Yttrium Iron Garnet

Magnetoelastic rf pulses with magnetically controlled echo time have been observed in a rod of yttrium iron garnet. Data were taken at room temperature in the frequency interval 0.5 to 3.3 Gc/sec with power input in the milliwatt range. Excitation and detection was accomplished by placing a wire antenna near an optically flat end-face of the rod. A nonuniform internal magnetic field was obtained by applying a steady, uniform external field parallel to the rod axis. The frequency-time-magnetic field characteristics have been measured. The behavior of these pulses can be explained in terms of a magnetoelastic disturbance traveling along the rod axis. It originates at that position along the axis where ωc=γHi. From there the disturbance travels to the nearer polished surface where it is reflected. On arrival back at the launch site a fraction of the energy is detected and the remainder reflected for another round trip. The process is repeated several times to give rise to a pulse sequence.