We describe the fabrication of a Mach-Zehnder optical modulator in LiNbO 3 by femtosecond laser micromachining, which is composed of optical waveguides inscripted by a femtosecond laser and embedded microelectrodes subsequently fabricated using femtosecond laser ablation and selective electroless plating. A half-wave voltage close to 19 V is achieved at a wavelength of 632.8 nm with an interaction length of 2.6 mm. This simple and cost-effective technique opens up new opportunities for fabricating integrated electro-optic devices. © 2008 Optical Society of America OCIS codes: 130.0250, 140.3390, 230.2090 Lithium niobate ͑LiNbO 3 ͒ is one of the most widely used nonlinear optic materials in integrated optics owing to its excellent nonlinear optical and electrooptic (EO) properties. Integrated EO devices based on waveguiding structures such as optical switches [1] and modulators [2,3] have gained significant attention. Conventionally, the waveguide fabrication is based on titanium diffusion or proton exchange, which permits fabrication of channel waveguides only close to the surface [4]. Recently, it has been demonstrated that buried optical waveguides in LiNbO 3 can be fabricated by femtosecond laser inscription [5], which opens the possibility to write 3D optical circuits in the crystal. Various fabrication parameters have been optimized by several groups [6][7][8], such as wavelength, repetition rate, polarization, pulse width, pulse energy, focusing geometry, and scanning speed. To realize integrated EO devices, it is further crucial to design and fabricate microelectrodes, which are usually obtained by use of lithographic methods. However, owing to the inherently planar nature of the lithographic process, this technique is limited in its capability to produce 3D structures. Furthermore, because the optical waveguides fabricated by femtosecond laser inscription usually are deeply buried in the crystal, the conventional surface electrodes give rise to weak EO interaction. As a simple and costeffective technique, laser-induced selective electroless deposition has been widely investigated, because it does not require fabrication steps involved in the traditional lithographic technique, such as deposition of thin layers of metals, pattern etching, and so on [9,10]. Recently, we developed a technique for selective metallization in LiNbO 3 using femtosecond-laser ablation and femtosecond-laser-assisted selective electroless plating, which allows for fabricating microelectrodes deeply embedded in LiNbO 3 [11]. In this Letter, we report the integration of embedded microelectrodes and optical waveguides in LiNbO 3 using a femtosecond laser. Based on this technique, a Mach-Zehnder interferometer (MZI) EO modulator in an x-cut LiNbO 3 crystal is demonstrated.For the fabrication of waveguides and electrodes, a Ti:sapphire laser system (Legend USP, Coherent Inc.) with an operation wavelength of 800 nm, a pulse width of ϳ40 fs, and a repetition rate of 1 KHz was used. Commercially available MgO-doped x-cut LiNbO 3 crystals...

The isolation and characterization of three novel triterpene glycosides 1-3 from the medicinal plant Ardisia japonica (Myrsinaceae) are described. The compounds are characterized by a branched oligosaccharide chain, composed of four sugar units. The oligosaccharide structures were determined by 1H-1H correlation spectroscopy (COSY, HOHAHA, ROESY) and 1H-13C heteronuclear correlation (HETCOR) nmr experiments. The aglycone moieties are the oleane-type triterpenes cyclamiretin A for 1 and the new 13,28-epoxy-30,30-dimethoxyolean-3 beta, 16 alpha-diol and 3 beta, 16 alpha-dihydroxy-13,28-epoxyolean-29-oic acid for 2 and 3, respectively.

Five new diterpenes, trigonochinenes A-E (1-5), and two known ones, 3,4- seco-sonderianol (6) and 3,4- seco-sonderianic acid (7), were isolated from the aerial part of Trigonostemon chinensis. Compounds 1-4 possess a rare 3,4-seco-cleistanthanic skeleton, and compound 5 is a highly aromatized tetranorditerpene. Structures of these compounds were elucidated by spectroscopic analysis. The antimicrobial activities of compounds 1-7 were evaluated against a panel of bacteria and fungi.

The physical mechanisms between residual strength and crack characteristic of ceramics after water-quenching are studied by statistically measuring the cracks in ceramic sheet. The result herein reveals that in the joint action of long crack length and density, the residual strength is maintained at the same level within a temperature range above the critical thermal shock temperature difference (ΔT C ). The result presented herein forms a further comprehension to the ceramics behaviors of and the theoretical approaches to thermal shock.