Yttrium Iron Garnet-gadolinium Gallium Garnet Research Articles

Temperature controlled magnon–photon coupling in a YIG/GGG-superconducting cavity coupled system

To explore potential applications in classical and quantum information transfer, the hybrid systems between yttrium iron garnet (YIG) and cavities have been extensively studied, and four coupling regimes have been defined based on the relative strength between the coupling strength and dissipation rate of each subsystem. Achieving the control of magnon–photon coupling between nano-thick YIG films and cavities remains to be explored. We experimentally measure the microwave transmission spectra of a nano-thick yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) film coupled to a superconducting cavity at different temperatures. The dissipation rate of the superconducting cavity increases significantly with decreasing temperature, which is influenced by the temperature-dependent magnetic susceptibility of the GGG substrate. Accompanied by the temperature-dependent magnon dissipation rate, a continuous transformation of the coupled system in strong coupling, Purcell and weak coupling regimes is achieved.

A Compact and Low-Loss Tunable Bandpass Filter Using YIG/GGG Film Structures

A compact and low-loss magnetically tunable bandpass filter (BPF) is presented in this letter. The yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) film structure is regarded as a resonator excited by a stepped terminal short-circuited stripline, and additional metal rings are plated on the other side of the RO4350 substrate. Two YIG/GGG film structures placed in parallel are directly coupled. This structure enhances the RF magnetic field, reduces filter loss, and suppresses parasitic response. The filter design and geometrical parameter optimization are first carried out using CST Studio Suite. When the magnetic field changes from 1820 to 7420 Oe, the filter is tuned from 5 to 19 GHz, with a 3-dB bandwidth (BW) of 62–107 MHz, insertion loss (IL) of less than 2 dB, and parasitic response suppression of about 20 dB over the entire tuning range (TR).

Magnetoelastic Waves in Submicron Yttrium–Iron Garnet Films Manufactured by Means of Ion-Beam Sputtering onto Gadolinium–Gallium Garnet Substrates

A series of equidistant oscillations have been revealed in the transmission spectrum and dispersion law of Damon–Eshbach surface magnetostatic waves (SMSWs) propagating in submicron (200-nm) yttrium–iron garnet (YIG) films manufactured by means of ion-beam sputtering onto gadolinium–gallium garnet (GGG) substrates. These oscillations correspond to the excitation of magnetoelastic waves in the YIG–GGG structure at frequencies of resonant interaction between the surface magnetostatic waves and the elastic shear modes of the wave-guiding YIG–GGG structure. The obtained results show that the studied YIG films are characterized by an efficient magnetoelastic coupling between their spin and elastic subsystems and the matching of acoustic impedances at the YIG–GGG interface, thus providing the possibility to consider the ion-beam sputtering of YIG films onto GGG substrates as a promising technology for the creation of magnonic and straintronic devices.

A Tunable X-Band Band-Pass Filter Module Using YIG/GGG Layer on RT/Duroid Substrate

A tunable X-band band-pass filter (BPF) module that consists of an 8-12-GHz passive BPF and a pair of tunable band-stop filters (BSFs) using yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) layers on RT/Duroid substrate is reported. The passive BPF and the tunable BSFs were first designed, simulated, and optimized using AWR Microwave Office Simulator. The tunable X-band BPF module was then constructed and simulated under 2-D bias magnetic fields with Ansoft HFSS software suite. The measured passband of the passive BPF was 7.8-11.8 GHz, with the center frequency at 9.8 GHz and the 3-dB bandwidth of 4.8 GHz. With the sets of bias magnetic fields at 1,700 and 2,360 Oe; 2,570 and 3,180 Oe; and 1,725 and 3,180 Oe applied on the pair of BSFs, tuning for the passband of the BPF module toward the high end, the low end, and the center was accomplished with the center frequency at 11.5, 7.9 and 9.8 GHz, the 3-dB bandwidths of 1.0, 1.1, and 1.2 GHz, and the tuning ranges of 3.4, 4.0, and 3.6 GHz, respectively. A good agreement between the simulation and experimental results was achieved.

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.

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.

Recent Advances in Magnetostatic Waves-Based Integrated Magnetooptic Bragg Cell Modulators in Yig-Ggg Waveguides

AbstractThe most recent advances in the integration architecture and diffraction efficiency of magnetostatic wave (MSW)-based guided-wave magnetooptic (MO) Bragg cell modulators in yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) waveguides are reported. A curved ion-milled hybrid waveguide lens pair has been integrated with a MO Bragg cell modulator in a taper waveguide with dimensions of 6.0x16.0mm2 to facilitate the collimation and focusing functions. An enhancement in the Bragg diffraction efficiency by two-to six-fold has been accomplished using a non-uniform bias magnetic field. An oscillator-based MO Bragg cell modulator has also been constructed and has provided a Bragg diffraction efficiency which is higher by a factor of two to four than that of a conventional delayline-based modulator.

High efficiency guided-wave magnetooptic Bragg cell modulator using nonuniform bias magnetic field

A technique for large enhancement of the diffraction efficiency of a guided-wave magnetooptic (MO) Bragg cell modulator using a nonuniform bias magnetic field in bismuth-doped yttrium iron garnet-gadolinium gallium garnet waveguide is reported. Since the velocity of propagation of the magnetostatic forward volume wave (MSFVW) varies with the bias magnetic field, a bias magnetic field of proper spatial distribution will modify its wave front and, thus, create a lensing effect upon the MSFVW. This lensing effect in turn reduces the angular beam spread of the MSFVW, and results in a higher MO Bragg diffraction efficiency. The experimental data obtained for the cases with uniform and nonuniform bias magnetic fields at the carrier center frequency range of 2.0–3.5 GHz have demonstrated a diffraction efficiency enhancement by two to six times. A diffraction efficiency as high as 70% has also been accomplished. Furthermore, the measured frequency responses indicate that the nonuniform bias magnetic field has had only a mild effect on the bandwidth of the MO Bragg cell modulator.

Integrated magnetooptic Bragg cell modulator in yttrium iron garnet-gadolinium gallium garnet taper waveguide and applications

An integrated magnetooptic (MO) device which consists of an ion-milled collimation-focusing lens pair and a guided-wave MO Bragg cell modulator in a yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) taper waveguide substrate with dimensions of 6.0/spl times/16.0 mm/sup 2/ has been realized for the first time. Performance characteristics of the waveguide lenses including the focal spot size, sidelobe level and throughput, and that of the integrated MO Bragg cell modulator using the magnetostatic forward volume wave (MSFVW) at X-band carrier frequency including the bandwidth, diffraction efficiency, dynamic range, and frequency resolution have been measured at the optical wavelength of 1.303 /spl mu/m. Scanning of the focused diffracted light beam by varying the carrier frequency of the MSFVW and RF spectral analysis by simultaneous application of multiple microwave frequencies have been demonstrated.

Integrated acoustooptic and magnetooptic devices for optical information processing

Acoustooptic (AO) Bragg interactions between guided optical waves and surface acoustic waves (SAW's) and the resulting AO Bragg cell modulators have evolved in integrated AO technology in recent years. A variety of hybrid multichannel integrated AO device modules including power and interferometric RF spectrum analyzers, space switches, tunable filters, frequency shifters and modulators, analog algebraic processors, programmable correlators and other multichannel device modules have been realized in common LiNbO/sub 3/ substrate up to 1.0/spl times/3.7 cm/sup 2/ in maximum size. The prospects for realization of their counterparts in monolithic integrated format in a common substrate of InGaAsP material system are also significantly enhanced recently. These AO device modules have shown a high degree of modularity and suggested applications in optical information processing and communications. In the meantime, the magnetooptic (MO) Bragg interactions between guided optical waves and magnetostatic waves (MSWs) in yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) waveguides have resulted in miniaturized MO Bragg cell modulators in analogy with the guided-wave AO Bragg cell modulators. Most recently the performance of such MO Bragg cell modulators has been significantly improved and the modulators have been integrated with ion-milled waveguide lenses to realize hybrid integrated MO device modules, and have been utilized to demonstrate a number of novel applications. In this paper, a review of some of these integrated AO and MO device modules and applications together with some unpublished new results are presented.

Spectral-domain analysis of dispersion characteristics of open coupled microstrip lines on YIG/GGG structures

This paper is to study coupled microstrip lines on layered yttrium iron garnet/gadolinium gallium garnet (YIG/GGG) structures. The problem is formulated using the spectral-domain technique, and the spectral Galerkin's method is utilized to compute the dispersion characteristics. Numerical results are presented for various values of structural and physical parameters such as widths of strips, thicknesses of YIG and GGG, separation between the strips, and applied DC magnetic field.

Wideband electronically tunable integrated magneto-optic frequency shifter at X band

A new wideband integrated optical frequency shifter that utilizes noncollinear guided-wave magneto-optic (MO) Bragg diffraction from magnetostatic-forward-volume waves (MSFVW) in a bismuth-doped yttrium-iron-garnet/gadolinium-gallium-garnet (YIG/GGG) waveguide, 6×10 mm2 in size, is reported. Constancy in the output angle of the frequency-shifted light beam, irrespective of the amount of frequency shift, is facilitated by synchronous tuning of the carrier frequency of the MSFVW and the bias magnetic field using an electronic synchronizer. The device operating at the optical wavelength of 1.302 μm and the carrier frequency centered at X band has demonstrated desirable characteristics including large frequency shift, very large tunable bandwidth, large dynamic range, and fast tuning speed. Specifically, bandwidths of 1.61 and 2.35 GHz and dynamic ranges of 35 and 32 dB at the center carrier frequencies of 6.035 and 11.025 GHz, respectively, and a tuning speed of 50 μs have been accomplished.

Permanent magnet-based guided-wave magnetooptic Bragg cell modules

Compact magnetostatic forward volume wave-based guided-wave magnetooptic (MO) Bragg cell modules have been realized by utilizing a pair of small samarium-cobalt permanent magnets together with a pair of current-carrying coils. A highly uniform DC magnetic field, has been obtained in the air gap where yttrium iron garnet-gadolinium gallium garnet (YIG-GdGG) waveguide samples are inserted. A tunable DC magnetic field as large as 2446 Oe corresponding to a tunable carrier frequency band of 6.85 GHz has been achieved. The resulting MO Bragg cell modules, at the optical wavelength of 1.303 mu m, with carrier frequencies ranging from 2.0 to 12.0 GHz have provided performance characteristics comparable to those obtained by using a bulk electromagnet. Compact MO Bragg cell modules have potential applications, such as scanning, switching of light beams, and real-time processing of wide-band microwave signals without requiring frequency down-conversion.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

RF MAGNETIZATION OF MAGNETOSTATIC FORWARD VOLUME WAVE IN A YIG-GGG LAYERED STRUCTURE WITH APPLICATION TO DESIGN OF HIGH-PERFORMANCE GUIDED-WAVE MAGNETOOPTIC BRAGG CELLS

Explicit expressions for the RF magnetization of magnetostatic forward volume waves (MSFVW) generated by a microstrip line transducer in a Yttrium Iron Garnet-Gadolinium Gallium Garnet (YIG-GGG) layered structure sandwiched between two finite ground planes have been derived for the first time. The behavior of the RF magnetization as a function of various physical and geometrical parameters and its influence on the design of high-performance guided-wave magnetooptic (MO) Bragg Cells are studied in detail. The effects of DC bias magnetic field and geometrical parameters on the RF magnetization and thus the MO Bragg diffraction or mode-conversion efficiency and the bandwidth are presented in plots generated using a computer. A good agreement between computed and experimental results has been obtained.

Magnetostatic backward volume wave-base-guided-wave magnetooptic Bragg cells and application to wide-band light beam scanning

The realization of high-performance magnetostatic backward volume wave (MSBVW)-based magnetooptic (MO) Bragg cells in pure and bismuth-doped yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) waveguides is discussed, and the demonstration of wide-angle light beam scattering using such MO Bragg cells is reported. The MSBVW-based MO Bragg cells have been shown to possess the following advantages over the magnetostatic forward volume wave (MSFVW)-based counterparts: (1) the center frequency of the former is higher by some 4.9 GHz at the same DC magnetic field; (2) the first passband in which the MO Bragg cells commonly operate is located at the high-frequency end for the former, but at the low-frequency end for the latter; and (3) the Bragg diffraction or mode-conversion efficiency of the MSBVW-based MO Bragg cells can be significantly higher than that of the MSFVW-based counterparts.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Ion-milled lenses and lens arrays in yttrium iron garnet-gadolinium gallium garnet waveguides

Waveguide lenses have been formed for the first time in yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) waveguides by using ion milling. Hybrid-type single lenses, lens arrays, and collimation-Fourier-transform lens pairs fabricated have shown good efficiency and near-diffraction-limited focal spot sizes. These waveguide lenses should facilitate realization of magnetostatic wave based integrated magneto-optic device modules for applications in communications and signal processing.

X-band magneto-optic Bragg cells using bismuth-doped yttrium iron garnet waveguides

Guided-wave magneto-optic Bragg cells at X-band microwave frequencies using magnetostatic forward volume waves (MSFVWs) in bismuth-doped yttrium iron garnet-gadolinium gallium garnet (Bi-doped YIG-GGG) waveguides are reported for the first time. Performance figures that have been obtained at an optical wavelength of 1.303 μm include a center frequency tuning range of 3.7–12.0 GHz, a diffraction efficiency of 12% at the magnetostatic wave power of 56 mW, a linear dynamic range &amp;gt;40 dB, and a −3 dB magneto-optic bandwidth of 150 MHz. These results represent a significant improvement over those obtained previously with the Bragg cells using pure YIG-GGG waveguides. Maximum scan angle of 6° and 5.3° were also measured, respectively, by tuning the rf frequency ∼10.0 GHz at a fixed dc magnetic field of 3660 Oe and by varying the dc magnetic field ∼3660 Oe at a fixed rf frequency of 10.0 GHz. A frequency resolution of 30 MHz was measured with rf spectral analysis experiments carried out at 12 GHz. Finally, a Faraday rotation coefficient as large as −2313°/cm was measured for the Bi-doped YIG-GGG waveguides.

Wideband scanning of a guided-light beam and spectrum analysis using magnetostatic waves in an yttrium iron garnet-gadolinium gallium garnet waveguide

Wideband scanning of a light beam through the use of magnetostatic waves has been accomplished for the first time. Specifically, a guided-light beam at a wavelength of 1.317 μm in an yttrium iron garnet-gadolinium gallium garnet waveguide was Bragg diffracted by magnetostatic forward volume waves (MSFVWs) operating at a frequency range of 2–7 GHz. Wideband scanning of the light beam was accomplished simply by changing the frequency of the MSFVW continuously from center frequencies of 2.5 and 6.0 GHz while keeping the dc magnetic field fixed or by continuously tuning the dc magnetic field while keeping the frequency of the MSFVW fixed at the center frequencies. A large number of resolvable scan spot positions were obtained in both cases. The resulting wideband magneto-optic Bragg cell or light beam scanner was also used to perform spectral analysis of wideband rf signals at a center frequency of 3.2 GHz. Potential advantages of the magneto-optic Bragg cell and scanner over the existing acousto-optic counterparts also identified.

GHz bandwidth magneto-optic interaction in yttrium iron garnet-gadolinium gallium garnet waveguide using magnetostatic forward volume waves

Very large bandwidth noncollinear coplanar magneto-optic interaction with magnetostatic forward volume waves in an yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) waveguide is reported for the first time. Bandwidths of 0.78 and 1.03 GHz centered, respectively, at the carrier frequencies of 2.5 and 6.0 GHz, and TM0 -TE0 mode-conversion efficiencies of 0.54 and 0.50% have been achieved at the optical wavelength of 1.317 μm using a single microstrip transducer and homogeneous dc magnetic fields of 2200 and 3500 Oe. A summary of related coupled-mode analysis is also presented.

Noncollinear coplanar magneto-optic interaction of guided optical wave and magnetostatic surface waves in yttrium iron garnet-gadolinium gallium garnet waveguides

Wideband noncollinear coplanar guided-wave magneto-optic diffraction and mode conversion by magnetostatic surface waves at multigigahertz (3–7 GHz) carrier frequencies in yttrium iron garnet-gadolinium gallium garnet waveguides have been observed and measured in detail for the first time. Interaction configuration, physical mechanisms, summary of a theoretical treatment, and some experimental results obtained at 1.152 μm optical wavelength are presented. This noncollinear coplanar magneto-optic interaction configuration should result in a number of integrated optic devices for wideband communications and signal processing applications at electronically tunable microwave carrier frequencies. The potential advantages of the resulting magneto-optic devices over the existing acousto-optic devices are also discussed.