Integrated electro-optic lens/scanner in a LiTaO3 single crystal

We report what we believe to be the first stand-alone integrated electro-optic lens and scanner fabricated on a single crystal of Z-cut LiTaO(3). The independently controlled lens and scanner components consist of lithographically defined domain-inverted regions extending through the thickness of the crystal. A lens power of 0.233 cm(-1) kV(-1) and a deflection angle of 12.68 mrad kV(-1) were observed at the output of the device.     

Near-IR tunable laser with an integrated LiTaO3 electro-optic deflector

We report the successful demonstration of a near-IR tunable laser (1525.4-1558.2 nm) that uses an integrated LiTaO3 deflector in combination with a reflection grating as an electronically tunable filter. The electro-optic deflector is a unique integrated optical device and consists of a horn-shaped array of electro-optic prisms in series. The almost 33 nm of tuning covers a wavelength region of high interest to the communications industry (1527-1550 nm).     

Two-Dimensional Electric-Field Vector Measurement by a LiTaO(3) electro-optic probe tip

An electro-optic probe tip that is made from LiTaO crystal to make tangentially two-dimensional electric-field (E-field) vector measurements is presented. We combine a new electro-optic modulation technique and a conventional one to resolve the two E-field components. The new modulation effect on the optical probing beam is caused by rotation of the principal axis the electro-optic crystal, which is proportional to the E-field. Inasmuch as there is no free charge involved in the axis rotation, rotation modulation of the axis can be as fast as conventional modulation. The principles are carefully derived, and an experimental system constructed, to measure two-dimensional E-field vectors on a test pattern. The results are in good agreement with those obtained with commercial software for electromagnetic simulation. The sensitivities of two tangential E-field components are 76 (mV/cm)/ radicalHz and 0.8 (V/cm)/ radicalHz, respectively. The root-mean-square error of an E-field directional measurement is 1.5 degrees .     

Planar LiTaO(3) waveguides fabricated by proton exchange in concentrated and diluted pyrophosphoric acid with annealing

Annealed proton-exchanged z-cut LiTaO(3) planar waveguides fabricated with pyrophosphoric acid have been characterized. For proton exchange, the extraordinary index increase Δ n(e) ranged from 0.0119 to 0.0141, depending on the exchange temperature. The effective diffusion coefficient D(e) ranged from 0.1325 μm(2)/h at 240°C to 0.545 μm(2)/h at 280 °C. Single-mode propagation losses were α = 0.7 dB/cm. Compared with benzoic acid, pyrophosphoric acid produces waveguides with a higher Δ n(e) and a lower propagation loss. For proton exchange in lithium phosphate-diluted pyrophosphoric acid, a lower Δ n(e) was obtained, but D(e) and propagation losses were not reduced. After proton exchange, the waveguides were annealed. The surface index initially increased, peaked, and then decreased. The waveguide depth d and the surface index n(s) were measured at regular intervals. Figures and empirical formulas relating the waveguide depth d and the surface index increase Δ n(s) to the anneal time, anneal temperatures, and the waveguide depth after proton exchange are given. An example is given in which, the desired waveguide parameters d and Δ n(s), the fabrication conditions could be calculated with the previously derived formulas. Propagation losses decreased to 0.4 dB/cm after prolonged annealing.     

First-order quasi-phase-matched second-harmonic generation in a LiTaO(3) waveguide

We achieved improvement in conversion efficiency in a first-order quasi-phase-matched second-harmonic generation device that uses a LiTaO(3) waveguide by experimentally characterizing the device process and the performances. Efficient overlaps among propagation light modes and the first-order periodically domain-inverted region are gained in a strongly confined waveguide fabricated by use of proton exchange annealed by a quick heat treatment. A blue-light power of 22 mW is obtained for a conversion efficiency of 18% by using a Ti:Al(2)O(3) laser. The observed FWHM temperature and wavelength acceptance bandwidths for second-harmonic generation power are 2.5 °C and 0.13 nm, respectively. Using this device with antireflection coating on the input and output facets of the waveguide, we generate 1.3 mW of blue light for a conversion efficiency of 4% by direct diode-laser doubling.     

Extraordinary-mode refractive-index change produced by the linear electro-optic effect in LiNbO(3) and reverse-poled LiNbO(3)

To examine aspects of an integrated photonic electric-field sensor, we calculate electro-optically induced refractive-index change in regular and reverse-poled LiNbO(3). Specifically, for y-propagating extraordinary modes, we determine how index change depends on electric-field magnitude and direction. To accomplish this, changes in index-ellipsoid shape and orientation are found by the use of a numerical eigenvalue procedure to diagonalize the impermeability tensor; then, refractive index is calculated by the use of a vector reference-frame transformation and a small perturbation approximation. A general formula is inferred from calculations for specific field directions. Electro-optic coefficients for reversepoled LiNbO(3) are obtained by application of a tensor reference-frame transformation to those of LiNbO(3). The index-calculation procedure has utility beyond the problem that is considered.     

Nickel aluminide (Ni3Al) fabricated by reactive infiltration

Nickel aluminide Ni₃Al in the single phase form, with grain size 10 m, porosity 5%, tensile strength 425 MPa, modulus 92 GPa and ductility 9.5% at room temperature, was fabricated by reactive infiltration at 800 °C of liquid aluminium into a porous preform containing 78 vol % nickel and made by sintering 3–7 m size nickel particles. Without sintering, the preform contained 58 vol % nickel and reactive infiltration resulted in an aluminium-matrix NiAl₃ particle ( 50 m size) composite and extensive growth of Ni-Al needles from the preform to the excess liquid aluminium around the preform.     

Rugate filters fabricated by a radio frequency magnetron sputtering system by use of an optical in situ monitoring technique

We propose, for the first time to our knowledge, a new feedback fabrication technique for rugate filters with sinusoidal refractive index distribution. The technique uses an in situ optical monitoring system, in contrast to conventional techniques for rugate filters that are based on time control, which is generally unsuitable for accurate fabrication of a continuous index distribution. We employed a-SiOx:H thin film as the material for the rugate filters because its refractive index can be successively controlled. Using the proposed technique and material, we fabricated near-infrared rugate minus filters having multiple and continuous refractive index distributions. The experimental and calculated spectra were well correlated as a result of applying the proposed feedback fabrication technique.     

Accurate measurements of the acoustical physical constants of LiNbO (3) and LiTaO(3) single crystals

The acoustical physical constants (elastic constant, piezoelectric constant, dielectric constant, and density) of commercial surface acoustic wave (SAW)-grade LiNbO(3) and LiTaO(3) single crystals were determined by measuring the bulk acoustic wave velocities, dielectric constants, and densities of many plate specimens prepared from the ingots. The maximum probable error in each constant was examined by considering the dependence of each constant on the measured acoustic velocities. By comparing the measured values of longitudinal velocities that were not used to determine the constants with the calculated values using the previously mentioned constants, we found that the differences between the measured and calculated values were 1 m/s or less for both LiNbO(3) and LiTaO(3) crystals. These results suggest that the acoustical physical constants determined in this paper can give the values of bulk acoustic wave velocities with four significant digits.     

Covalent micropatterning of poly(dimethylsiloxane) by photografting through a mask

A new photografting method to micropattern a covalent surface modification on poly(dimethylsiloxane) (PDMS) provides advantages in simplicity and efficiency. To accomplish the entire process on the benchtop, the PDMS was initially treated with benzophenone dissolved in a water/acetone mixture. This process permitted limited diffusion of the photoinitiator into the PDMS surface. Polymerization of acrylic acid was initiated by exposure of the benzophenone-implanted PDMS to UV radiation through a photomask with a thin aqueous layer of acrylic acid sandwiched between the PDMS and photomask. This procedure resulted in patterned poly(acrylic acid) (PAA) on the PDMS surface. In the modified regions, PAA and PDMS formed an interpenetrating polymer network extending 50 microm into the PDMS with an X-Y spatial resolution of 5 microm. The carboxyl groups of the PAA graft could be derivatized to covalently bond other molecules to the patterned PAA. Two bioanalytical applications of this micropatterned surface were demonstrated: (1) a guide for cell attachment and growth and (2) a substrate for immunoassays. 3T3 cells were shown to selectively localize to modified surface regions where they could be cultured for up to 7 days. Additionally, the micropatterned surface was used to immobilize either protein A or antibody for heterogeneous immunoassays.     

Microlenses fabricated by ultraviolet excimer laser irradiation of poly(methyl methacrylate) followed by styrene diffusion

A new technique of microlens array fabrication based on the use of excimer laser radiation is described. Poly(methyl methacrylate) (PMMA) substrates are treated with many low-energy KrF laser pulses and exposed to styrene vapor. The irradiated material swells, producing spherical microlenses that are stabilized by UV polymerization. The chemistry of this process and the optical quality of the lenses are discussed.     

In situ monitoring of microfracture during plasma spray coating by laser AE technique

Atmosphere plasma spray coating materials include many pores and lamellar boundaries formed by flattened particles during spraying process although high reliability are required in ceramic coatings for turbines. These boundaries become an origin of the microcracks and following crack growth. As it is known that spraying parameters strongly affect the microstructure and strength of coating, it is expected to establish in situ monitoring technique for coating process. However, there is a limit to apply the existing non-destructive evaluation techniques to real-time monitoring at elevated temperature. We have investigated a non-contact measuring system to detect acoustic emission (AE) signals due to microfractures using a laser interferometer, and applied this technique for understanding microfracture process of ceramic coating at elevated temperature. In this paper, we evaluated the effect of several spraying parameters on the initiation and growth process of microcrack by detecting AE signals during coating process using a non-contact laser AE technique.     

In situ monitoring of microfracture during plasma spray coating by laser AE technique

Atmosphere plasma spray coating materials include many pores and lamellar boundaries formed by flattened particles during spraying process although high reliability are required in ceramic coatings for turbines. These boundaries become an origin of the microcracks and following crack growth. As it is known that spraying parameters strongly affect the microstructure and strength of coating, it is expected to establish in situ monitoring technique for coating process. However, there is a limit to apply the existing non-destructive evaluation techniques to real-time monitoring at elevated temperature. We have investigated a non-contact measuring system to detect acoustic emission (AE) signals due to microfractures using a laser interferometer, and applied this technique for understanding microfracture process of ceramic coating at elevated temperature. In this paper, we evaluated the effect of several spraying parameters on the initiation and growth process of microcrack by detecting AE signals during coating process using a non-contact laser AE technique.     

Evaluation and selection of LiNbO(3) and LiTaO(3) substrates for SAW devices by the LFB ultrasonic material characterization system

This paper demonstrates the evaluation and selection of commercially available LiNbO(3) and LiTaO(3) single crystals and wafers for surface acoustic wave (SAW) devices using the line-focus-beam ultrasonic material characterization (LFB-UMC) system. This system enables measuring leaky-SAW (LSAW) propagation characteristics precisely and efficiently for a number of specimens. The wafers are prepared from the top, middle, and bottom parts of four 128 degrees YX LiNbO(3) and seven X-112 degrees Y LiTaO(3) single crystals. For both series of crystals, the measured LSAW velocities increase from top to bottom in the crystals and with the increasing crystal growth number. The velocity changes for all wafers are 0.036% for 128 degrees YX LiNbO(3) and 0.035% for X-112 degrees Y LiTaO(3), corresponding to changes of 0.038 mol% and 0.075 mol% in Li(2)O concentration, respectively. Moreover, the inhomogeneity in the first X-112 degrees Y LiTaO(3) single crystal caused by some undesirable wafer fabrication processes can be detected precisely, although it is difficult for the conventional methods to obtain such information.     

Growth of highly oriented LiTaO3 thin film on Si with amorphous SiO2 buffer layer by pulsed laser deposition

High-quality single-phase, c-axis textured LiTaO₃ thin films have been deposited on Si(100) substrate with amorphous SiO₂ buffer layer for optic waveguide application by pulsed laser deposition under optimized conditions of 30 Pa oxygen pressure and 650 °C. The amorphous SiO₂ buffer layer with a thickness of 100 nm was coated on the Si(100) by thermal oxidation at 1000 °C. Li-enriched LiTaO₃ ceramic target was used during the deposition. In order to study the influence of oxygen pressure on the orientation, crystallinity and morphology, different oxygen pressures (10 Pa, 20 Pa, 30 Pa and 40 Pa) were used. X-ray diffraction (XRD) results showed that LiTaO₃ thin films exhibited highly c-axis orientation under 30 Pa. It was observed by scanning electron microscopy (SEM) that the as-grown film in the optimal conditions was characterized by a dense and homogeneous surface without cracks, and the average grain size was in the order of 25 nm.     

Multispecies in situ monitoring of a static internal combustion engine by near-infrared diode laser sensors

A multispecies near-infrared diode laser spectrometer has been constructed for measurements of carbon monoxide, carbon dioxide, and methane directly in the exhaust of a static internal combustion engine. A wavelength modulation-division multiplexing scheme was implemented for the two distributed feedback diode lasers. Gas concentration variations were observed for changes in operating conditions such as increasing and decreasing the throttle, adjusting the air-fuel ratio, and engine start-up.     

大型立式罐容量计量中三维激光扫描方法研究

针对传统立式罐容量计量方法存在工作效率低、自动化程度低、劳动强度大、安全隐患大等缺点,提出一种基于三维激光扫描技术的大型立式罐容量计量方法。通过运用"三角形面积积分法"和"截面积高度积分法",计算出立式罐不同液位高度对应的容积值。并设计试验比对系统,选取一个6000m3的油罐作为研究对象进行内测试验,结果表明三维激光扫描方法具有良好的重现性,以传统几何测量法的结果作为参考,验证该方法的有效性,并且能够显著提高检定效率;选取一个5000m3的油罐作为研究对象进行外测试验,结果表明该方法在不规则罐容量准确计量、罐体的变形和不规则监测等方面具有独特的优势。     

In situ monitoring of thermally cycled metal matrix composites by neutron diffraction and laser extensometry

A novel stroboscopic neutron diffraction data collection system has been developed. In combination with scanning laser extensometry this has been used to investigate the thermal cycling behaviour of SiC short fibre reinforced Al matrix composites. Three-dimensional unit cell finite element models have been produced, incorporating matrix deformation both by creep and plasticity. Comparison of the experimental results with model predictions has allowed conclusions to be drawn about the deformation processes which dominate at different parts of the thermal cycle.