Lp Shi

Ultrafast-laser-induced parallel phase-change nanolithography

A phase-change nanolithography technique is developed to fabricate up to millions of two-/three-dimensional nanostructures (∼50nm) over a large area at a high speed by combining femtosecond laser, microlens array, and wet etching process. Near-field scanning optical microscopy, electrical force microscopy, and atomic force microscopy were used to characterize optical and electrical properties of crystalline and amorphous states, respectively. Different reactions of both amorphous and crystalline areas in phase-change film to alkaline solution are demonstrated. Multiphoton absorption and ultrashort pulse contribute to nanostructure generation. This method opens up a route for nanodevice fabrication with phase-change material.

Direct femtosecond laser nanopatterning of glass substrate by particle-assisted near-field enhancement

Direct femtosecond laser nanopatterning of glass substrate by particle-assisted near-field enhancement was demonstrated in this letter. The nanostructure was characterized by field-emission scanning electron microscopy and atomic force microscopy. No cracks were found on the glass surface. The hole size were measured from 200∼300nm. When laser fluence is close to the damage threshold, a trihole structure was observed. Nonlinear multiphoton absorption and near-field enhancement were the mechanisms of the nanofeature formation. Calculations based on particle-on-surface theory were carried out. The suggested method has potential applications in the nanolithography of a transparent glass substrate for nanostructure device fabrication.

Ultrafast phase transitions in Ge1Sb2Te4 films induced by femtosecond laser beam

Ultrafast phase transitions triggered by single femtosecond laser pulse in Ge1Sb2Te4 films were investigated. By proper control of the film thickness, ultrafast crystalline and amorphous phase transformations have been achieved in Ge1Sb2Te4 films. These utlrafast phase transitions were confirmed by reflectivity change and x-ray diffraction measurement.

Femtosecond laser irradiation for functional micro-/nanostructure fabrication

Femtosecond laser is a unique processing tool to make micro-/nanostructures on heat sensitive bio-polymer film & glass substrate, to create 3D structures inside glass, to achieve 20-nm nanostructuring and large-area THz, micro-mold and micro-device patterning.

Domain inversion in ion-exchanged KLN waveguides

Ferroelectric local domain inversion was found in Rb + /Ba 2+ ion-exchanged KLN waveguides for the first time. The inversion layer formed only near the @ c surface. The domain inversion shape was found to a rectangle. To explain the mechanism of the domain inversion phenomenon, a space-charge field model was proposed.

Design and fabrication of segmented waveguides in KTiOPO/sub 4/ substrates

High power blue light generated by quasi phase matched (QPM) second harmonic generation (SHG) techniques is very attractive for high density optical storage. KTiOPO/sub 4/ (abbreviated as KTP) is one of the most important materials used in QPM SHG. Since 1987 many kinds of waveguides and devices have been demonstrated in KTP substrates. However there still remains some technique problems, for example, the control of the duty cycle of the segmented waveguides as well as cracking of the waveguides. On the other hand the photolithography process used for fabrication of KTP segmented waveguides has not been reported. In this paper we report on the experimental results of segmented optical waveguides fabricated in KTP substrates.