431 research outputs found
Microfabrication of Three-Dimensional Structures in Polymer and Glass by Femtosecond Pulses
We report three-dimensional laser microfabrication, which enables
microstructuring of materials on the scale of 0.2-1 micrometers. The two
different types of microfabrication demonstrated and discussed in this work are
based on holographic recording, and light-induced damage in transparent
dielectric materials. Both techniques use nonlinear optical excitation of
materials by ultrashort laser pulses (duration < 1 ps).Comment: This is a proceedings paper of bi-lateral Conf. (Republics of China &
Lithuania) on Optoelectronics and Magnetic Materials, Taipei, May 25-26,
2002.
Femtosecond laser microfabricated devices for biophotonic applications
Femtosecond Laser DirectWriting has emerged as a key enabling technology
for realising miniaturised biophotonic applications offering clear advantages
over competing soft-lithography, ion-exchange and sol-gel based fabrication
techniques. Waveguide writing and selective etching with three-dimensional
design flexibility allows the development of innovative and unprecedented
optofluidic architectures using this technology. The work embodied in this
thesis focuses on utilising the advantages offered by direct laser writing in
fabricating integrated miniaturised devices tailored for biological analysis.
The first application presented customised the selective etching phenomenon
in fused silica by tailoring the femtosecond pulse properties during the writing
process. A device with an embedded network of microchannels with a
significant difference in aspect-ratio was fabricated, which was subsequently
applied in achieving the high-throughput label-free sorting of mammalian
cells based on cytoskeletal deformability. Analysis on the device output cell
population revealed minimal effect of the device on cell viability.
The second application incorporated an embedded microchannel in fused
silica with a monolithically integrated near-infrared optical waveguide. This
optofluidic device implemented the thermally sensitive emission spectrum
of semiconductor nanocrystals in undertaking remote thermometry of the
localised microchannel environment illuminated by the waveguide. Aspects
relating to changing the wavelength of illumination from the waveguide were
analysed. The effect of incorporating carbon nanotubes as efficient heaters
within the microchannel was investigated. Spatio-thermal imaging of the
microchannel illuminated by the waveguide revealed the thermal effects to
extend over distances appreciably longer than the waveguide cross-section.
On the material side of direct laser writing, ultra-high selective etching is
demonstrated in the well-known laser crystal Nd:YAG. This work presents
Nd:YAG as a material with the potential to develop next-generation optofluidic
devices
Implementation of nearly single-mode second harmonic generation by using a femtosecond laser written waveguiding structure in KTiOPO4 nonlinear crystal
We propose a hybrid photonic structure to realize guided-wave second harmonic generation (SHG) from near-infrared (NIR at 1064 nm) to visible (green light at 532 nm) wavelength with nearly single-mode output. The periodically arrayed tracks have been produced in KTiOPO4 nonlinear crystal by femtosecond laser writing, which enable efficient light field confinement with cladding-like refractive index distributions. Particularly, the track-cladding surrounded central region is free of any tracks, which serves as waveguiding cores. With designed core diameters, the structures could enable single-mode propagation at selected wavelength regime on purpose. In this work, the hybrid structure contains a larger-input core section and a connected smaller-output core section, which in principle supports nearly single mode for either fundamental pump beam or second harmonic beam in the input and output channel, respectively. Based on this hybrid structure we implement nearly single-mode SHG at 532 nm, and comparable normalized conversion efficiency (1.1%/W/cm) in the continuous-wave (CW) regime is obtained with respect to that (1.2%/W/cm) of multimode SHG from a single large-core channel structure. This work paves the way to realize mode profile controlling for selected wavelength by using laser-written arrayed tracks.The work is supported by the National Natural Science Foundation of China (61775120); Junta de Castilla y León (Project SA046U16) and MINECO (FIS2013-44174-P, FIS2015-71933-REDT)
High-throughput three-dimensional lithographic microfabrication
A 3D lithographic microfabrication process has been developed that is high throughput, scalable, and capable of producing arbitrary patterns. It offers the possibility for industrial scale manufacturing of 3D microdevices such as photonic crystals, tissue engineering scaffolds, and microfluidics chips. This method is based on depth-resolved wide-field illumination by temporally focusing femtosecond light pulses. We characterized the axial resolution of this technique, and the result is consistent with the theoretical prediction. As proof-of-concept experiments, we demonstrated photobleaching of 3D resolved patterns in a fluorescent medium and fabricating 3D microstructures with SU-8 photoresist.Deshpande Center for Technological Innovation (Massachusetts Institute of Technology. School of Engineering)Singapore-MIT Alliance for Research and Technology (SMART
Nanoscale local modification of PMMA refractive index by tip-enhanced femtosecond pulsed laser irradiation
Investigation techniques based on tip-enhanced optical effects, capable to
yield spatial resolutions down to nanometers level, have enabled a wide palette
of important discoveries over the past twenty years. Recently, their underlying
optical setups are beginning to emerge as useful tools to modify and manipulate
matter with nanoscale spatial resolution. We try to contribute to these efforts
by reporting a method that we found viable to modify the surface refractive
index of polymethyl methacrylate (PMMA), an acrylic polymer material. The
changes in the refractive index are accomplished by focusing a femtosecond
pulsed near-infrared laser beam on the apex of a metalized nano-sized tip,
traditionally used in scanning probe microscopy (SPM) applications. The adopted
illumination strategy yields circular-shaped modifications of the refractive
index occurring at the surface of the PMMA sample, exhibiting a lateral size
<200 nm, under 790 nm illumination, representing a four-fold increase in
precision compared to the current state-of-the-art. The light intensity
enhancement effects taking place at the tip apex makes possible achieving
refractive index changes at low laser pulse energies (<0.5 nJ), which
represents two orders of magnitude advantage over the current state-of-the art.
The presented nanoimprinting method is very flexible, as it can be used with
different power levels and can potentially be operated with other materials.
Besides enabling modifications of the refractive index with high lateral
resolution, this method can pave the way towards other important applications
such the fabrication of photonic crystal lattices or surface waveguides
Direct femtosecond laser writing of 3D photonic structures in rare-earth doped lithium niobate = escritura directa mediante láser de femtosegundos de estructuras fotónicas 3D en niobato de litio dopado con iones de tierras raras
Tesis doctoral inédita. Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de FÃsica de Materiales. Fecha de lectura: 18-12-200
- …