Tsutomu Okamoto

TM‐TE optical‐mode conversion induced by a transversely propagating magnetostatic wave in a (BiLu)3Fe5O12 film

Highly Bi‐substituted garnet films (BiLu)3Fe5O12 (Bi=0.89/f.u.) have been grown on (111)‐oriented Gd3Ga5O12 substrates by liquid‐phase epitaxy with only Bi2O3 as a flux. The specific Faraday rotation θF attains −0.14 deg/μm at 1.3 μm. Guided‐optical‐wave propagation loss of 0.6 dB/cm at 1.3 μm is obtained by doping an appropriate amount of MgO in the melt. Magnetostatic backward volume wave (MSBVW) is launched efficiently into the film as expected from the measured small ferromagnetic resonance linewidth of 0.7 Oe, whereas magnetostatic surface wave and magnetostatic forward volume wave are subject to the severe attenuation due to their coupling to spin‐wave modes. The interaction between guided optical wave and MSBVW is investigated in a transverse configuration where the input optical wave passes almost orthogonal to MSBVW. The TM‐TE optical‐mode conversion induced by MSBVW is observed over the frequency range of 3.5–7.5 GHz. Its efficiency, as high as 47%/0.8 W at 4 GHz, is obtained for the interaction...

A 0.5-4.0-GHz Tunable Bandpass Filter Using YIG Film Grown by LPE

A tunable bandpass filter using YIG film grown by liquid phase epitaxy (LPE) has been developed. Taking advantage of the very low resonance frequency in the perpendicular resonance of YIG film, an operation frequency of 0.5 GHz has been achieved. In order to make this filter operate up to 4.0 GHz, a new technique for multioctave tuning has been developed and applied to the filter. Over the wide tuning range from 0.5 GHz to 4.0 GHz, low insertion loss and high spurious suppression have been achieved. The performance of this filter satisfies the requirements for use as a tracking preselector in a microwave spectrum analyzer.

Reduction of optical absorption at a wavelength of around 0.8 μm in LPE garnet (TmBiCa)3(FeGaPt)5O12

Liquid-phase epitaxy (LPE) garnet films (TmBiCa)3(FeGaPt)5O12 have been grown using only Bi2O3 as the flux so that the film containing Bi gives high specific Faraday rotation. The film does not contain Pb, which may affect optical absorption. The optical absorption coefficientα at 810 nm has been effectively reduced by doping Ca in the melt. Our data show that a minimum level ofα and of the anisotropy constantKu and also the maximum of the electrical resistivityϱ are achieved when Ca2+ replaces Fe2+. Fe2+ results from Pt4+ incorporation in the film due to a Bi2O3 flux attack on a Pt crucible. Using a compensated film,α of 58 cm−1 and a figure of merit of 9deg/dB were obtained.

A 13-GHz YIG-film tuned oscillator for VSAT applications

A description is given of 13-GHz tunable oscillator using YIG film grown by liquid-phase epitaxy. A very low phase noise of -90 dBc/Hz at 10 kHz from the carrier was achieved over the entire tuning range of 500 MHz. The design criteria for the YIG disk resonator and the biasing condition of GaAs FET needed to achieve the low phase noise and avoid high-power instability are discussed. The tuning characteristic and the oscillator performance over temperature is presented. The output power of the oscillator was over 6.6 dBm without using the output buffer amplifier. The variation of the output power over the tuning range from 13 GHz to 13.5 GHz was less than 0.3 dB, and the hysteresis of the oscillation frequency was less than 1 MHz. The temperature drift was 10 MHz from -30 degrees C to +60 degrees C. The excellent linear tuning characteristic of this oscillator makes it ideal for use as a frequency-agile synthesized local oscillator in a very small aperture terminal (VSAT).<<ETX>>

A 0.5-4.0 GHz Tunable Bandpass Filter Using YIG Film Grown by LPE

A tunable bandpass filter using YIG film grown by LPE has been developed. Over the wide tuning range from 0.5 GHz to 4.0 GHz, low insertion loss and high spurious suppression have been achieved. The performance of this filter satisfies the requirements for use as a tracking preselector in a microwave spectrum analyzer.

Recent progress in the quality of KTiOPO4 and Beta-BaB2O4 crystals used for the miniature integrated green SHG laser and 1.5W of cw 266-nm generation

High power deep ultraviolet (UV) radiation has attracted much attention in areas of photolithography, micro fabrication and material processing as well as ultra high density optical disk mastering. We report progress in quality of (beta) -BaB2O4 (BBO) which is essential in obtaining 1.5 W of cw UV generation from the BBO resonant ring cavity out of 3 W of green input power from a diode pumped Nd:YAG laser. Progress in KTiOPO4 (KTP) and its potential applications are also reviewed.

Magnetocrystalline anisotropy and magnetostriction of FeRuGaSi single crystals: SOFMAX

The magnetocrystalline anisotropy constant, K1 and the magnetostriction constants, λ100 and λ111 for recently found soft magnetic FeGaSi and FeRuGaSi alloys were determined in the composition region, 0–8 at. % Ru, 5–15 at. % Ga, 10–22 at. % Si, and bal. Fe. The Ru 4–8 at. %‐added FeRuGaSi alloys have the intersectional points, where λ100, λ111, and K1 simultaneously become zero, at the compositions around Fe67Ru4Ga11Si18 and Fe65Ru8Ga8Si19 (at. %), whereas in the FeGaSi alloy the K1=0 line and the two zero magnetostrictive lines are apart from one another.

Suppression of the photoconductivity of Bi12GeO20 and its application to electro-optic light valve

Spectral dependence of the conductivity of doped Bi12GeO20 crystals were measured at room temperature under the illumination of a constant power density. It was found that the photoconductivity of Bi12GeO20 could be highly suppressed by simultaneous doping of Ga and Ca, which keeps the dark conductivity at a low level. The doped Bi12GeO20 crystals were applied to an electron beam addressed electro-optic light valve. Real-time TV display was accomplished by the light valve built in a sealed-off tube.

Reliability of Czochralski-grown B-BaB2O4 (BBO) devices

We report the first operation of more than 1000 hours of continuous wave (CW) 100-mW output at 266 nm which was frequency-quadrupled from a Nd:YAG or a Nd:YVO4 laser. We used a Czochralski (Cz)-grown (beta) -BaB2O4 (BBO) crystal device to double a 532-nm wave in an external ring cavity. The round trip cavity loss increasing rate was 7.6 X 10-5 percent/hour at a 266-nm power density of 270 W/cm2. The UV range optical transmission loss of the Cz-grown crystal was evaluated. The optical loss of the Cz-grown crystal for e-ray at 266 nm was improved to 2 percent/cm, which was half of the crystal grown by the top seeded solution growth (TSSG) method. The degradation rate, (delta) p equals (dP4w(t)/dt)/P4w(0), was also evaluated in 30 MW/cm2 of 266-nm generation from a Q-switched Nd:YAG laser. The (delta) p of Cz-crystal was typically 0.1 percent/hour, which was one order of magnitude lower than that of the TSSG- crystals. The fabrication process was also improved. Our system with the crystal device can be put to practical use in the areas of photolithography, material processing and ultra high-density optical disk mastering.

Progress in all-solid-state deep-ultraviolet coherent light sources

High power deep ultraviolet (UV) radiation has attracted much attention in areas such as photo-lithography, micro fabrication, material processing and ultra high density optical disk mastering. We report progress in improving the quality of Czochralski-grown (beta) -BaB2O4 (BBO) which is essential for generating high average output power in the deep ultraviolet regime. We obtained 1.5 W of cw 266 nm output using an external resonant doubler, 1.3 W of 213 nm output from a flashlamp pumped Q-switched Nd:YAG laser and more than 0.4 W of 213 nm radiation from a commercial 6 W diode-pumped high repetition rate Q-switched Nd:YAG laser using our melt-grown BBO crystals for the nonlinear frequency conversion. Using the cw 266 nm output speckle-free 0.25 micrometers photolithography and micro-fabrication was demonstrated.