High-intensity, blue LEDs have attracted interest because of their wide applications. Dicing method using tightly focused ultra-fast laser beam inside the sapphire substrate is one of the remarkable processing method in terms of high yield and LED performance. In this paper, we would like to introduce the polarization controlled laser processing technique in which laser beam is focused tightly inside the sapphire substrate. The morphology of a cut line can be controlled by changing the direction of laser polarization to an orientation at of the substrate. We, moreover, found that the crack inside the sapphire substrate can be elongated by using the double pulse train for 20 % larger than the single pulse when the pulse interval was 20 nsec. The crack was fabricated effectively by shorter pulse interval.
We present the fabrication of microstructures for photonic and micro-/opto-fluidic applications using femtosecond
laser 3D direct writing technique in zirconium-based sol-gel hybrid resist. The advantages and mechanism of
photo-polymerization of this new material under fs-pulsed laser exposure are discussed. We suggest and achieve a
novel method to fabricate free-standing and movable photonic microstructures, which exhibit much less distortion
than the conventional structures attached to substrates, especially when made at close to the photopolymerization
threshold. Fabrication of free-movable structures allows us to quantitatively study the shrinkage of photoresist
and to improve the resolution. It also contributes to tuning the stop band position of photonic crystals to
shorter wavelength. Furthermore, the demonstrated freely-movable property makes it possible to laser trap and
manipulate photonic microstructures and have potential application in optofluidics and bio-applications.
We demonstrate laser manipulation of different nematic and smectic liquid crystal droplets in heavy water. Peculiarities of laser trapping and manipulation depending on the molecular structure of liquid crystal are discussed. Possibility of molecular reordering inside the tweezed droplet is demonstrated. This phenomenon can be used to induce the birefringence and to manipulate droplets, which have a small birefringence, e.g., a radial droplet of negligible birefringence can be turned into a birefringent one at high laser trapping power. This is a demonstration of the optical nonlinear effect being responsible for a micro-mechanical phenomenon such as spinning of the droplet in a circularly polarized laser tweezers. Three-photon absorption of MBAPB dye at 1064 nm wavelength is demonstrated inside the liquid crystal droplet at comparatively low ~60 MW/cm2 intensity.
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