R.W. Eason

Nanodroplets deposited in microarrays by femtosecond Ti:sapphire laser-induced forward transfer

The authors present the deposition of nanoscale droplets of Cr using femtosecond Ti:sapphire laser-induced forward transfer. Deposits around 300nm in diameter, significantly smaller than any previously reported, are obtained from a 30nm thick source film. Deposit size, morphology, and adhesion to a receiver substrate as functions of applied laser fluence are investigated. The authors show that deposits can be obtained from previously irradiated areas of the source material film with negligible loss of deposition quality, allowing subspot size period microarrays to be produced without the need to move the source film.

Analysis of mutually incoherent beam coupling in BaTiO 3

When two mutually incoherent light beams are used as simultaneous inputs to a crystal of BaTiO(3), a spontaneously generated loop of light is created that provides a coupling mechanism between the two input beams, resulting in two phase-conjugate outputs. This behavior is discussed, and the phase-conjugate reflectivities are presented as a function of the ratio of input-beam intensities. A simple theory is developed to describe this phenomenon, and the predictions are compared with experimental data.

Microstructuring of lithium niobate using differential etch-rate between inverted and non-inverted ferroelectric domains

Single crystal samples of lithium niobate have been spatially patterned with photoresist, and subsequently domain inverted using electric field poling, to produce a range of two dimensional spatial domain structures. Differential etching has subsequently been carried out using mixtures of hydrofluoric and nitric acids, at a range of temperatures between room temperature and the boiling point. The structures produced show very smooth, well defined, deep features, which have a range of applications in optical ridge waveguides, alignment structures, V-grooves, and micro-tips. Details are given of the fabrication procedures, and examples of structures are shown.

Impurity enhanced self-pumped phase conjugation in the near infrared in 'blue' BaTiO3

Abstract Photorefractive self-pumped phase-conjugation is examined at near-infrared wavelengths using doped ‘blue’ BaTiO 3 , and reflectivities are reported as high as 76% between 720 nm and 1004 nm due, as is believed, to a backward stimulated photorefractive scattering mechanism. Data also suggests that it is possible to stabilise the phase-conjugate reflectivity by vibrating the crystal.

Growth of KNbO3 thin films on MgO by pulsed laser deposition

Crystalline and stoichiometric KNbO3 thin films have been grown on (100) oriented MgO substrates by pulsed laser deposition technique. Electron microprobe analysis and Rutherford backscattering spectroscopy of the films show a progressive loss of K with increasing substrate‐target distance. To compensate for this K loss the ceramic KNbO3 targets were enriched with K2CO3 powder, pressed at room temperature, and sintered at 650 °C. For a substrate‐target distance of 6 cm, targets with [K]/[Nb] molar ratio=2.85 yield stoichiometric KNbO3 films. A partial oxygen pressure of 2×10−2 mbar was optimum for growing transparent films. Films grown between 650 and 700 °C show the KNbO3 crystalline phase with its (110) axis preferentially oriented perpendicular to the surface of the substrate. At these temperatures KNbO3 diffusion into the MgO substrate is observed. Films grown from KNbO3 single crystal targets only contain a Mg4Nb2O9 crystalline layer.

Laser operation of an Nd:Gd3Ga5O12 thin‐film optical waveguide fabricated by pulsed laser deposition

We report the laser operation of a thin-film waveguide structure grown by the pulsed laser deposition technique. A 2.7-µm-thick crystalline film of neodymium doped Gd3Ga5O12 (Nd:GGG) lases at a wavelength centered at 1.06µm when pumped by a Ti:sapphire laser at 808 nm.

TI:SAPPHIRE PLANAR WAVEGUIDE LASER GROWN BY PULSED LASER DEPOSITION

We document the lasing performance of a waveguiding layer of Ti:sapphire, of ~12-mum thickness, grown by pulsed laser deposition from a 0.12-wt.% Ti(2)O(3) Ti:sapphire single-crystal target onto an undoped z-cut sapphire substrate. Lasing around 800 nm is observed when the waveguide layer is pumped by an argon-ion laser running on all-blue-green lines, with an absorbed power threshold of 0.56 W, with high-reflectivity (R>98%) mirrors. With a 5% pump duty cycle and a T=35% output coupler, a slope efficiency of 26% with respect to absorbed power is obtained, giving quasi-cw output powers in excess of 350 mW.

Surface domain engineering in congruent lithium niobate single crystals: A route to submicron periodic poling

We describe a technique for surface domain engineering in congruent lithium niobate single crystals. The method is based on conventional electric-field poling, but involves an intentional overpoling step that inverts all the material apart from a thin surface region directly below the patterned photoresist. The surface poled structures show good domain uniformity, and the technique has so far been applied to produce domain periods as small as ∼1 μm. The technique is fully compatible with nonlinear optical integrated devices based on waveguide structures.

Bistability and noncommutative behavior of multiple-beam self-pulsing and self-pumping in BaTiO 3

Two mutually incoherent beams from a multilongitudinal-mode Ar(+) laser have been used as simultaneous inputs to a self-pumped barium titanate crystal. With one beam positioned for self-pumping and the other for self-pulsing, the overall output behavior is seen to have two stable states that depend on the previous history of single-beam selfpumping or self-pulsing. During one of these output states, a spontaneously generated continuous loop of light is seen in the crystal, providing a coupling mechanism between the two mutually incoherent beams.

Direct ultraviolet writing of channel waveguides in congruent lithium niobate single crystals

We report the fabrication of optical channel waveguides in congruent lithium niobate single crystals by direct writing with continuous-wave ultraviolet frequency-doubled Ar+ laser radiation (244 nm). The properties and performance of such waveguides are investigated, and first results are presented.