We report on a technique for precise hole drilling in optical fibers using tightly focused femtosecond laser pulses. This direct laser writing approach makes it possible to minimize the amount of waveguide material for uncompromised mechanical performance of the fiber. The proof-of-the-principle of the fiber integration into a microfluidic chip is demonstrated. We show that fabricated holes in the waveguides can be used for measurement of absorption coefficient and refractive index changes at 1x10-3 refractive index units and 2 cm-1 for refractive index and absorption changes, respectively. Simple design and integration possibility of laser-fabricated waveguide sensors is prospective for optofluidic applications.
Ripples on silicon have been fabricated by femtosecond laser ablation to minimize Si removal and to achieve a flat (not a groove-like) coverage of extended millimeter size areas for nano-/micro-fluidic applications. Such flat ripple-covered regions were found to control flow and wetting properties of water. Depending on orientation of ripples the flow speed of a 1 µl water droplet can be changed from 1.6 to 9.1 mm/s. Gold-coated ripples on sapphire are demonstrated as an excellent SERS substrate with more than one order-of-magnitude larger sensitivity and superior reproducibility a,.., compared to the commercial SER.S substrates; SERS signal on the ripples was more than 15 times higher and more than 2 times more uniform as compared to Klarite substrate at
633 mn excitation wavelength. It was shown that ripples can also be fabricated on thin transparent conducting
indium tin oxide (ITO) coatings of 45 mn thickness. The electrical resistance can be controlled by orientation and area fraction of ripples. Applications on miniaturized heaters for incubation and micro-chemistry chambers on lab-on-chip and electrowetting are discussed along with potential applications in orientational flows, self-assembly of micro-chips, and sensing.
We present a set of practical rules critical for designing and building a modern nanotechnology laboratory, focused
on photonic applications in a cleanroom environment. We show the impacts on time, cost and quality of early
design decisions and its importance on achieving the final fully functional laboratory. Best practice examples are
presented for setting up a modern laboratory/facility, following analysis of the time, cost and quality constraints.
The case study presented is the engineering and architectural solution of the nanofabrication cleanroom facility
in the Advanced Technology Centre at Swinburne University of Technology, Australia. Set of practical rules is
established for the cost and time efficient set up of the nanotechnology facilities for the research and development.
We present two realizations of a highly sensitive platform useful in environmental sensing and diagnostics - a
Fabry-Perot (FP) interferometer - (i) a pair of semi-transparent mirrors integrated into a microfluidic channel
and (ii) a silicon membrane of sub-micrometer thickness. Simple way to make microfluidic channels by (i)
hot-embossing into a sheet of technical grade PMMA and (ii) double-sided tape fixed glass with Au-coated
mirrors are presented. By changing the thickness of the Au coating, the roughness and porosity of mirror surface
is controlled. In turn, this provides a method to tune finesse of the FP cavity to monitor solutions flowwing
between the FP-mirrors. In case of silicon, the FP cavity is formed by coating two sides of a Si-membrane. These
two different approaches to harness a high sensitivity of the FP interferometry are proposed: changes of FP cavity
caused by materials in the channel can be monitored, while the coated membrane is used to monitor the effects
which are induced by membrane's ambiance. The finesse of the FP cavity is optimized for the maximum spectral
sensitivity at the cost of transmitted light intensity in case of microfluidic channel and silicon membrane. Via
optimization of the finesse (in the range 2-5) and overall transmission of a FP-pair (20-60%) practical solutions
are proposed for spectral sensing of (i) refractive index and mechanical channel width's changes in a microfluidic
channel as well as (ii) temperature changes of membrane's environment. Asymmetric thickness of the FP mirrors
can be used to optimize sensitivity.
The year 2007 witnessed the experimental realization of extraordinary laser beams termed Airy and parabolic
beams. Surprisingly, these beams are immune to diffraction and in addition exhibit transverse acceleration while
propagating. This peculiar property of both Airy and parabolic beams facilitates the clearance of both microparticles
and cells from a region in a sample chamber through particle/cell transport along curved trajectories. We
term this concept "Optically mediated particle clearing" (OMPC) and, alternatively, "Optical redistribution"
(OR) in the presence of a microfluidic environment, where particles and cells are propelled over micrometersized
walls. Intuitively, Airy and parabolic beams act as a form of micrometer-sized "snowblower" attracting
microparticles or cells at the bottom of a sample chamber to blow them in an arc to another region of the sample.
In this work, we discuss the performance and limitations of OMPC and OR which are currently based on a single
Airy beam optionally fed by a single parabolic beam. A possible strategy to massively enhance the performance
of OMPC and OR is based on large arrays of Airy beams. We demonstrate the first experimental realization of
such arrays.
Femtosecond laser pulses with energy of 0.9 nJ per pulse and a 80 MHz repetition rate at a wavelength of 750 nm were used to fabricate straight microchannels in a PMMA substrate. The size and shape of the microchannels can be controlled by changing the fabrication parameters of speed, the number of fabrication repeats and delay in-between fabrication repeats. It has been proposed that the absorption of energy in the focal region modifies the density of the polymer matrix, which after annealing the sample above the glass transition temperature results in the formation of the microchannels. Diffusion of heat through the substrate is a uniform process which has the effect of creating symmetrically shaped channels. This fabrication method is expected to have applications in the fabrication of
microstructures or microfluidic devices in polymer substrates.
A continuous wave laser beam of an infrared wavelength at 800 nm is used for two-photon excitation in a photobleaching polymer for 3D bits data storage. We successfully demonstrate the recording and reading of multiple layers of data bits up to a depth of 100 micrometers within a thick photobleaching polymer. The achievable 3D bit density may be up to 3.5 Tbits/cm3 if a variable tube length can be implemented into the recording and reading processes.
KEYWORDS: Absorption, Polymers, 3D optical data storage, Optical storage, Data storage, Photorefractive polymers, Ultraviolet radiation, Objectives, 3D image processing, Multilayers
Multi-layered (or three-dimensional) optical memories have increasingly become a field of interest of interest in the development of a high density optical data storage devices. Systems that utilise multiple layer recording can achieve recording densities from 100 to 10,000 times higher than conventional optical data storage devices.
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