Rare-earth and Bi-substituted iron garnet thin film materials exhibit strong potential for application in various fields of science and frontier optical technologies. Bi-substituted iron garnets possess extraordinary optical and MO properties and are still considered as the best MO functional materials for various emerging integrated optics and photonics applications. However, these MO garnet materials are rarely seen in practical photonics use due to their high optical losses in the visible spectral region. In this paper, we report on the physical properties and magneto-optic behaviour of high-performance RF sputtered highly bismuth-substituted iron garnet and garnet-oxide nanocomposite films of generic composition type (Bi,&#x2009;Dy/Lu)<sub  >3</sub>(Fe,&#x2009;Ga/Al)<sub  >5</sub>O<sub  >12</sub>. Our newly synthesized garnet materials form high-quality nanocrystalline thin film layers which demonstrate excellent optical and MO properties suitable for a wide range of applications in integrated optics and photonics.

Mohammad Nur-E-Alam

Mikhail Vasiliev

Kamal Alameh

Viacheslav Kotov

Physical Properties and Behaviour of Highly Bi-Substituted Magneto-Optic Garnets for Applications in Integrated Optics and Photonics

We developed a small and compact system of diode lasers, which can be inserted into the lower tools of a bending press. The parts of the system allow easy plug and play operation and can be installed for any bending length. The diode laser, which is based on 200&#x2009;W laser bars on microchannel cooler, allows the heating of sheet metals in the forming zone shortly before and during the bending process. There is no unnecessary heating of other parts of the bending equipment, no wear of the tool, and, if properly done, no damage of the surface of the metal. The power per bending length is 16&#x2009;kW/m.

F. Bammer

D. Schu&#x000F6;cker

T. Schumi

B. Holzinger

G. Humenberger

A Diode-Laser-System for Laser-Assisted Bending of Brittle Materials

Electrostatic levitation combined with laser heating is becoming a mature technique that has been used for several fundamental and applied studies in fluid and materials sciences (synthesis, property determination, solidification studies, atomic dynamic studies, etc.). This is attributable to the numerous processing conditions (containerless, wide heating temperature range, cooling rates, atmospheric compositions, etc.) that levitation and radiative heating offer, as well as to the variety of diagnostics tools that can be used. In this paper, we describe the facility, highlighting the combined advantages of electrostatic levitation and laser processing. The various capabilities of the facility are discussed and are exemplified with the measurements of the density of selected iron-nickel alloys taken over the liquid phase.

Paul-Fran&#xE7;ois Paradis

Takehiko Ishikawa

Yuki Watanabe

Junpei Okada

Hybrid Processing Combining Electrostatic Levitation and Laser Heating: Application to Terrestrial Analogues of Asteroid Materials

The finite-difference time-domain (FDTD) algorithm has been used in simulation-based designs of many optical devices, but it fails to reproduce high-Q whispering gallery modes (WGMs). On the other hand, the nonstandard (NS) FDTD algorithm can accurately compute WGMs and can be used to make simulation-based designs of WGM devices. Wavelength splitters using the coupled resonator optical waveguides (CROWs) based on WGM couplings have recently attracted attention because they are potentially ultracompact. In this paper, we design a CROW wavelength splitter using NS FDTD simulations and demonstrate high interchannel extinction ratios of over 20&#x2009;dB.

Naoki Okada

James B. Cole

Shigeki Yamada

Kensuke Ogawa

Yoshifumi Katayama

Nonstandard FDTD Simulation-Based Design of CROW Wavelength Splitters

A method for measuring frequencies of the terahertz (THz) radiation emitted by the antenna mounted on the photoconductive (PC) device is presented. Two laser beams with slightly different frequencies irradiate the PC device, producing a beat current of 1&#x2009;THz in the photocurrent. A microwave signal is applied to the antenna electrode. The frequency of the THz wave is measured using the homodyne detection of the optical beat with the high-order harmonics of the microwave. It is being investigated that the high-order harmonics are produced by the PC device owing to its nonlinearity. Periodic peaks generated by the homodyne detection were observed in the photocurrent, as the microwave was swept from 16 to 20&#x2009;GHz with a power of &#x2212;40&#x2009;dBm. Using the peak frequencies, the THz-wave frequency was determined to be <svg style="vertical-align:-0.97874pt;width:78.987503px;" id="M1" height="10.8125" version="1.1" viewBox="0 0 78.987503 10.8125" width="78.987503"  xmlns="http://www.w3.org/2000/svg">
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			<text transform="matrix(1,0,0,-1,-71.95,64.37)">
				<tspan style="font-size: 11.21px; " x="0" y="0">1</tspan>
				<tspan style="font-size: 11.21px; " x="5.6040001" y="0">0</tspan>
				<tspan style="font-size: 11.21px; " x="11.208" y="0">3</tspan>
				<tspan style="font-size: 11.21px; " x="16.812" y="0">0</tspan>
				<tspan style="font-size: 11.21px; " x="22.416" y="0">.</tspan>
				<tspan style="font-size: 11.21px; " x="25.218" y="0">3</tspan>
				<tspan style="font-size: 11.21px; " x="33.310177" y="0">±</tspan>
				<tspan style="font-size: 11.21px; " x="43.475834" y="0">3</tspan>
				<tspan style="font-size: 11.21px; " x="49.07983" y="0">.</tspan>
				<tspan style="font-size: 11.21px; " x="51.881832" y="0">7</tspan>
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		</g>
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</svg>&#x2009;GHz. The measurement error is estimated to be less than 0.43&#x2009;GHz. The proposed method realizes a compact frequency meter in the THz region.

Kengo Murasawa

Koki Sato

Takehiko Hidaka

Measurement of Terahertz Optical-Beat Frequency Using High-Order Harmonics of Microwave in a Photoconductive Device

We consider application of the discrete Fourier transform-spread
orthogonal frequency-division multiplexing (DFT-spread OFDM) technique to high-speed fiber optic communications. The DFT-spread OFDM is a form of single-carrier technique that possesses almost all advantages of the multicarrier OFDM technique (such as high spectral efficiency, flexible bandwidth allocation, low sampling rate, and low-complexity equalization). In particular, we consider the optical DFT-spread OFDM system with polarization division multiplexing (PDM) that employs a tone-by-tone linear minimum mean square error (MMSE) equalizer. We show that such a system offers a much lower peak-to-average power ratio (PAPR) performance as well as better bit error rate (BER) performance compared with the optical
OFDM system that employs amplitude clipping.

Fanggang Wang

Xiaodong Wang

Coherent Optical DFT-Spread OFDM

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Advances in Optical Technologies