Magnetostatic Forward Volume Wave Research Articles

Excitation and Reception of Electromagnetic, Magnetostatic and Spin Waves in Ferrite Films

The paper presents a new universal formulation of electromagnetic fields in microwave ferrite-dielectric waveguiding structures from the given magnetic field distribution of an external source. The solution is derived from the linearized Landau-Lifshits equation using an orthogonality condition for eigenwaves of a magnetization. The magnetization excited in ferrite is obtained in an electrodynamic, magnetostatic or dipole-exchange approximation, depending on the approximation used for eigenwaves. Results are applied for the formulation and the analytical solution of self-consistent electrodynamic problems of an excitation and a reception of waves in ferrite films by transmission lines of an arbitrary type. Numerical calculations are performed for filters and delay lines on the base of symmetric strip-lines using surface and forward volume magnetostatic waves in ferrite films.

Interaction of guided optical waves and magnetostatic forward volume waves in a double-layered waveguide under inclined magnetic field

The noncollinear interaction between the guided optical waves (GOWs) and magnetostatic forward volume waves (MSFVWs) is theoretically studied in a double-layered waveguide under inclined magnetic field. The diffraction efficiency (DE) and the mode-conversion efficiency of GOWs are calculated numerically at the different inclination angles of the field. The results indicate that the double-layered waveguide, in which the top magnetic layer is made of the Bi-doped YIG film, can enhance the DE of GOWs. Under the phase-matching conditions, the DE may be greatly enhanced by using an appropriately inclined magnetic field in the double-layered waveguide. In addition, by varying the inclination angle of the field and the interval of the double-layered waveguide, the magneto-optical (MO) coupling between the GOWs and MSFVWs can be adjusted in the larger range. It is possible to improve the performances of the MO waveguide devices more effectively.

Excitation and Reception of Electromagnetic, Magnetostatic and Spin Waves in Ferrite Films - Abstract

The paper presents a new universal formulation of electromagnetic fields in microwave ferrite-dielectric waveguiding structures from the given magnetic field distribution of an external source. The solution is derived from the linearized Landau-Lifshits equation using an orthogonality condition for eigenwaves of a magnetization. The magnetization excited in ferrite is obtained in an electrodynamic, magnetostatic or dipole-exchange approximation, depending on the approximation used for eigenwaves. Results are applied for the formulation and the analytical solution of self-consistent electrodynamic problems of an excitation and a reception of waves in ferrite films by transmission lines of an arbitrary type. Numerical calculations are performed for filters and delay lines on the base of symmetric strip-lines using surface and forward volume magnetostatic waves in ferrite films.

Nonlinear characteristics of magnetooptic Bragg diffraction in bismuth substituted yttrium iron garnet films

In this article, the nonlinear characteristics of magnetostatic forward volume wave (MSFVW)-based guided-wave magnetooptic Bragg cell modulators in bismuth-substituted yttrium iron garnet-gadolinium gallium garnet waveguides using nonuniform bias magnetic field are reported. First, the dispersion characteristics of the MSFVW under nonuniform bias magnetic field are analyzed, and the explicit expression for its bandwidth is determined. The transmission measurements of the MSFVW show that owing to the nonuniform magnetic field, the bandwidth is significantly increased. Next, the results of noncollinear magnetooptic (MO) Bragg diffraction experiments using the MSFVW in the frequency range from 2.0 to 4.0 GHz are presented. Two types of nonlinear process, namely, the four-magnon decay and modulation instabilities, are observed. However, the MO experiments at the carrier frequency of 2.85, 3.10, and 3.25 GHz suggest that the decay instabilities did not play a significant role in the MO interaction because of the larger degree of phase mismatch induced by the satellite waves generated during the nonlinear processes. We find that despite the presence of the decay instabilities, the MO Bragg diffraction characteristics still comply with that predicted by the coupled-mode theory before the nonlinear processes evolve into the modulation instabilities. Once the four-magnon modulation instabilities set in at the threshold powers, the MO Bragg diffraction will incur a drop in diffraction efficiency by as much as 9%. This feature results from perturbation of the satellite waves of smaller wave numbers induced in the modulation instabilities that lead to the MO phase mismatch. A model is established to describe the combined contributions of the initial MSFVW and the excited satellite waves associated with the modulation instabilities to the MO Bragg diffraction characteristics.

Magnetostatic-wave envelope soliton in microstrip line using YIG-film substrate

In this paper, a dispersion relation of the microstrip line on a yttrium-iron-garnet (YIG)-film substrate has been derived under the approximation of a two-dimensional analysis. The dispersion curve shows the mixed state of quasi-TEM mode and magnetostatic forward volume wave (MSFVW) mode, and these two modes are coupled with each other at gyromagnetic frequency where MSFVW solitons are excited efficiently. Based on the numerical parameters of the calculated dispersion curve, simulation of the soliton form has been carried out by numerically solving the nonlinear Schrodinger equation. The results are compared with the experimental results of MSFVW envelope bright soliton in a microstrip line on YIG-film-gadolinium-gallium-garnet substrate.

Interaction between guided optical waves and magnetostatic waves in bismuth-doped yttrium–iron–garnet waveguide under inclined magnetic fields

The noncollinear interaction between guided optical waves and magnetostatic waves under inclined bias magnetic field is studied in detail. The diffraction efficiency (DE) and the mode-conversion efficiency (MCE) of guided optical waves with magnetostatic forward volume waves in the bismuth-doped yttrium–iron–garnet (Bi-doped YIG) waveguide are calculated numerically. The calculation results indicate that the DE and the MCE are different in physical conception and the DE is not equal to the MCE in magnitude under inclined bias magnetic field. The DE may be greatly increased by using an appropriately inclined bias magnetic field, which has been experimentally confirmed in a pure YIG waveguide. By using an inclined bias magnetic field and the Bi-doped YIG waveguide, under the phase-matching conditions, the maximum DE can come up to 79.5% or more.

Measurements of angular and spatial characteristics of magnetostatic wave beams by an optical guided-wave probe

Optical measurements of the angular and spatial characteristics of magnetostatic forward volume wave (MSFVW) beams propagating both in a linear and in a non-linear regime in yttrium–iron–garnet (YIG) film have been performed. The MSFVW beams were excited by a single-element microstrip transducer, within the microwave frequency range 2–3 GHz. The measurements were conducted with the help of an optical probing technique based on the magneto-optical (MO) interaction between guided optical waves and the MSFVWs in the YIG film. The MO probing system was built on the principle of transverse Bragg diffraction geometry, allowing us to measure the spatial evolution of the partial plane waves making up the MSFVW beam. In the linear regime, the measurements of the longitudinal profiles of the partial waves have shown that the MSFVW attenuation coefficient can increase following a linear law, from 2 to 10 cm −1, as the MSFVW wave number increases from 200 to 2000 cm −1. Also, it was shown that MSFVW beams with different frequencies can be spatially separated at a small distance from the microstrip transducer (≈2 mm) by using a weak non-uniform magnetic bias field with a gradient of ≈30 Oe/cm. In the non-linear regime, there are, at least, three specific levels of the incident microwave power which correspond to different manifestations of non-linearity of the MSFVW beams. At a certain value of the power, the partial plane waves of the beam can periodically change the direction of propagation (we observed a periodic collision of these waves). A small increase of the power level can lead to a spatial-periodic energy exchange between the different groups of the partial plane waves. At high microwave powers, non-linear MSFVW can excite a discrete spectrum of new spin-wave modes, the in-plane wave number of which is less than the wave number of the MSFVW. These non-linearly excited waves exist within a small spatial region situated near the microstrip transducer.

Magnetostatic volume waves in lossy YIG film backed by a metal of finite conductivity

Dispersion relations for magnetostatic volume waves propagation in a yttrium-iron-garnet (YIG) film coated with a thin metal film of finite conductivity have been derived. The real and imaginary parts of the complex wavenumber are found by solving the dispersion relations. The effects of finite conductivity and thickness of the metal on the phase and attenuation constant for both magnetostatic forward volume wave and magnetostatic backward volume wave in lossy YIG film are discussed.

A magnetostatic forward volume wave oscillator-based magneto-optic Bragg cell modulator

A guided-wave magneto-optic (MO) Bragg cell modulator that utilizes a magnetostatic forward volume wave (MSFVW) oscillator through a feedback loop is reported. The carrier frequency of the MSFVW signals involved in the MO interaction is tuned linearly from 2.112 to 3.274 GHz by increasing an external bias magnetic field from 2350 to 2900 Oe. Compared with a conventional delay line-based MO Bragg cell modulator, the oscillator-based MO modulator can provide higher diffraction efficiency by twofold to fourfold owing to reduction of insertion losses in the MSFVW oscillator. Furthermore, such oscillator-type MO modulator can be more easily integrated with other monolithic microwave integrated circuit components.

Nondispersive magnetostatic forward volume wave propagation in a double-layered yttrium–iron–garnet film structure with dielectric spacer

The present article reports a theoretical study of nondispersive magnetostatic forward volume wave (MSFVW) propagation in a double-layered yttrium–iron–garnet (YIG)-film structure consisting of two YIG films separated by a dielectric layer. Numerical computations are presented that show that a significant improvement in bandwidth for nondispersive MSFVW propagation can be obtained in the present separated double-layered YIG-film structure over the previously reported double-layered YIG-film geometry wherein the two YIG films were in direct contact.

Noncollinear Interaction of Guided Optical Waves and Magnetostatic Forward Volume Waves Under Inclined Bias Magnetic Field

Coupled-mode equations for Stokes and anti-Stokes interactions of guided optical waves with magnetostatic forward volume waves under inclined magnetic field are given. Calculation results indicate that, only at normal magnetization, the diffraction efficiency (DE) is equal to the mode-conversion efficiency (MCE) in magnitude; by comparison to the case of normal magnetization, the DE and the MCE can be increased greatly under appropriate inclined magnetic field. For the YIG waveguide used, the DE for the Stokes interaction is much greater than that for the anti-Stokes interaction when the inclined angle|θ| < 25° and the MCE is symmetrical about θ. For the Bi-doped YIG film, the MCE presents a rapid oscillation with θ. The obtained results tally with the experiments.

Magnetostatic forward volume wave soliton in a microstrip line with YIG film substrate

This article considers the envelope soliton of a magnetostatic forward volume wave propagating in a YIG thin-film microstrip line. It is demonstrated theoretically and experimentally that this waveguide works as a device for microwave pulse compression and for short pulse generation. According to the experimental results, an input 35-ns microwave pulse at 3 GHz was compressed to 10 ns. Also, by means of the split-step Fourier method, the mode of soliton propagation is numerically evaluated and compared with the experimental values. From the results, it is found that the YIG thin-film microstrip line has better characteristics than conventional devices, such as trapping of microwave energy in the strip. It is also found that the use of a nonuniform magnetic bias field is extremely effective. © 1999 Scripta Technica, Electron Comm Jpn Pt 2, 82(4): 39–46, 1999

Properties of Magnetostatic Wave Propagating in YIG Waveguide Under Inclined Magnetization

The characteristics of magnetostatic forward volume waves (MSFVWs) propagating in magneto-optical (MO) film waveguide under inclined bias magnetic field are analyaed. The dependences of MSFVW propagation constant and dynamic magnetization related to the MO coupling coefficients on mode number, frequency and inclined bias magnetic field are calculated in detail. It is shown that the greater the MSFVW frequency f and the mode number m as well as the less bias magnetic field Hi and inclination θ, the greater MSFVW propagation constant Ks is; the amplitude of zero-mode MSFVWs is much greater than that of high-mode MSFVWs. In an appropriate frequency range, MSFVW amplitude can be increased under an inclined bias magnetic field, and then the diffraction efficiency of guided optical waves with MSFVWs is improved.

Nonlinear ferromagnetic resonance and foldover in yttrium iron garnet thin films-inadequacy of the classical model

A thin-film resonator structure has been used for quantitative measurements of ferromagnetic resonance foldover and the associated bistable power response for yttrium iron garnet (YIG) thin films. The resonator consisted of a 1-mm by 1-mm-square, 4.9 /spl mu/m-thick epitaxial YIG film on top of a 50 /spl mu/m-wide, 3-mm-long microstrip transducer. A static magnetic field of 3200 Oe was applied perpendicular to the film. Low- order magnetostatic forward volume wave standing modes were excited at low power levels in the -20-dBm range and detected as resonance dips in reflected power versus frequency spectra over the range 4-5 GHz. At powers in the 0- to +15-dBm range, these dips showed foldover and bistable response characteristics for increasing and decreasing frequency or power sweeps. The use of 1-10-/spl mu/s-wide pulses instead of continuous-wave (CW) excitation resulted in the consistent disappearance of the foldover and bistability characteristics. The frequency sweep pulse data at fixed power reproduced the down-sweep CW results, and the pulse data for both increasing and decreasing power at fixed frequency reproduced the increasing-power CW results. A quantitative theoretical analysis demonstrates that observed foldover and bistable response characteristics are much weaker than predicted from the classical precession foldover mechanism proposed by Anderson and Suhl, in which the decrease in the static component of the magnetization drives the response. The up-sweep and down-sweep foldover frequency jumps both occur sooner than predicted by this classical mechanism and the calculated foldover profiles are much more severe than the data show.

Microwave and magnetooptic measurements of nonlinear dispersive magnetostatic waves in a yttrium-iron-garnet-gadolinium-gallium-garnet waveguide

Nonlinear propagation characteristics of magnetostatic surface waves (MSSWs) with carrier frequencies ranging from 0.5 to 7.0 GHz and magnetostatic forward volume waves (MSFVWs) with carrier frequencies ranging from 0.5 to 5.0 GHz in yttrium iron garnet-gadolinium gallium garnet waveguides have been measured in a delay line configuration using both microwave and guided-wave magnetooptic (MO) methods. The latter, involving noncollinear guided-wave MO Bragg interaction, was employed for the first time. For the MSSW, nonlinear characteristics including power limiting, discrete sideband modulation, continuum sideband modulation, and group splitting were observed and measured. Among such nonlinear characteristics, continuum modulation spectrum was observed and measured for the first time. For the MSFVW, nonlinear characteristics including parametric instability and soliton formation were also observed and measured. The MO data obtained by scanning the location of the incident light beam right beneath the input transducer and along the MSW propagation path has shown that the nonlinear characteristics observed were related to propagation and not to electromagnetic to MSW conversion effects at the input. Theoretical estimates are in a fair agreement with the experimental data. Finally, compression of an input pulse of 60 rf cycles (20 ns in width) to an output pulse of 6 rf cycles (2 ns in width) using a 3 GHz MSFVW pulse was also demonstrated.

Experimental investigation of the nonlinear interaction between optical guided waves and magnetostatic forward volume waves in a Bi-YIG film

We have observed experimentally the coupling effects between magnetostatic forward volume waves (MSFVW) and optical guided waves in a bismuth-doped yttrium iron garnet (BGYIG) film, and these effects were demonstrated in a short interaction length (5 mm). The detailed coupling mechanics existing between microwave frequency, high power and optical guided waves are not yet clear. This paper reports on optical-MSFVW interaction from an experimental view point. A microwave frequency range of S-band (2-4 GHz) was used to excite MSFVW in a Bi-YIG film. An optical wave with 1.152 /spl mu/m wavelength was directly injected through the side wall of the Bi-YIG film.

Theory of MSFVW excitation in a YIG film by a finite-length microstrip transducer

A theoretical study of the excitation of magnetostatic forward volume waves (MSFVW's) in a YIG film by a microstrip transducer of finite length is described. Previous studies of the excitation problem have assumed an infinitely long transducer which is a good assumption at the upper end of the MSFVW spectrum but becomes increasingly unacceptable at the lower end of the spectrum where the MSFVW wavelength is comparable to or larger than the transducer lengths used in practice. The present work reports brute-force numerical computations of MSFVW wavefront mapping and power flow generated by finite-length transducers which are in agreement with expectation.

Auto-oscillation thresholds at the main resonance in ferrimagnetic films

The propagation of large-amplitude forward-volume magnetostatic waves (MSW's) is studied in ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ and $[\mathrm{BiLu}{]}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ thin films. The onset of auto-oscillations beyond the second Suhl instability influences the transmission characteristics of a MSW delay line. Global variations in transmitted power over a frequency-power input parameter space are monitored using density plots. There is a shift in the MSW passband with increasing input power that is explained by a decrease in demagnetizing field with an increase in dynamic magnetization. As the input power increases beyond a threshold value, we observe an increase in signal amplitude, heralding the onset of auto-oscillations. Fingers of auto-oscillation spanning an input range of 200 MHz and 10 dB are formed. The locations of these fingers are correlated with the locations of spin-wave resonance notches in the MSW passband. The auto-oscillation thresholds in the vicinity of a spin-wave resonance notch are 4--8 dB lower than elsewhere in the passband. A heuristic model based on a reduced group velocity near a notch can explain the lower threshold values.

Magneto-Static Wave Oscillator-Based Integrated Magneto-Optic Bragg Cell Modulator*

AbstractA novel magnetooptic (MO) Bragg cell modulator that utilizes a magnetostatic forward volume wave (MSFVW) oscillator is presented. The carrier frequency of the MSFVW signals involved in the MO interaction is tuned linearly from 2.112 to 3.274 GHz by increasing an external bias magnetic field from 2350 to 2900 Oe. Compared with a conventional magnetostatic wave (MSW) delay line-based MO Bragg cell modulator, the proposed modulator can provide significantly higher diffraction efficiency owing to reduction of insertion losses in the MSFVW oscillator. Furthermore, the oscillator-type MO modulator can be more easily integrated with other MMIC devices.

THEORY OF GUIDED-WAVE MAGNETOOPTIC BRAGG DIFFRACTION IN YIG-GGG WAVEGUIDE UNDER INCLINED BIAS MAGNETIC FIELD

A theoretical Treatment is presented on the propagation characteristics of magnetostatic forward volume waves and related guided-wave magnetooptic (MO) Bragg diffraction in an YIG-GGG waveguide under an inclined bias magnetic field.It is found that,in contrast to the usual situation of a perpendicular bias magnetic field,an inclined bias magnetic field leads to the modification to the phase matching condition and,as a result of increased Faraday effect etc.,facilitates enhancement of MO Bragg diffraction efficiency.Such an efficiency enhancement enables utilization of low-propagation loss materials such as the pure YIG for construction of viable guided-wave MO Bragg devices.The theoretical predictions are in good agreement with the experimental results.