Doppler effect on nanopatterning with nonlinear laser lithography

[No abstract available

Portable Microfluidic Integrated Plasmonic Platform for Pathogen Detection

Timely detection of infectious agents is critical in early diagnosis and treatment of infectious diseases. Conventional pathogen detection methods, such as enzyme linked immunosorbent assay (ELISA), culturing or polymerase chain reaction (PCR) require long assay times, and complex and expensive instruments, which are not adaptable to point-of-care (POC) needs at resource-constrained as well as primary care settings. Therefore, there is an unmet need to develop simple, rapid, and accurate methods for detection of pathogens at the POC. Here, we present a portable, multiplex, inexpensive microfluidic-integrated surface plasmon resonance (SPR) platform that detects and quantifies bacteria, i.e., Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) rapidly. The platform presented reliable capture and detection of E. coli at concentrations ranging from ∼105 to 3.2 × 107 CFUs/mL in phosphate buffered saline (PBS) and peritoneal dialysis (PD) fluid. The multiplexing and specificity capability of the platform was also tested with S. aureus samples. The presented platform technology could potentially be applicable to capture and detect other pathogens at the POC and primary care settings. © 2015, Nature Publishing Group. All rights reserved

Femtosecond laser written waveguides deep inside silicon

Photonic devices that can guide, transfer, or modulate light are highly desired in electronics and integrated silicon (Si) photonics. Here, we demonstrate for the first time, to the best of our knowledge, the creation of optical waveguides deep inside Si using femtosecond pulses at a central wavelength of 1.5 μm. To this end, we use 350 fs long, 2 μJ pulses with a repetition rate of 250 kHz from an Er-doped fiber laser, which we focused inside Si to create permanent modifications of the crystal. The position of the beam is accurately controlled with pump-probe imaging during fabrication. Waveguides that were 5.5 mm in length and 20 μm in diameter were created by scanning the focal position along the beam propagation axis. The fabricated waveguides were characterized with a continuous-wave laser operating at 1.5 μm. The refractive index change inside the waveguide was measured with optical shadowgraphy, yielding a value of 6 × 10−4, and by direct light coupling and far-field imaging, yielding a value of 3.5 × 10−4. The formation mechanism of the modification is discussed. © 2017 Optical Society of America

Rich complex behaviour of self-assembled nanoparticles far from equilibrium

A profoundly fundamental question at the interface between physics and biology remains open: what are the minimum requirements for emergence of complex behaviour from nonliving systems? Here, we address this question and report complex behaviour of tens to thousands of colloidal nanoparticles in a system designed to be as plain as possible: the system is driven far from equilibrium by ultrafast laser pulses that create spatiotemporal temperature gradients, inducing Marangoni flow that drags particles towards aggregation; strong Brownian motion, used as source of fluctuations, opposes aggregation. Nonlinear feedback mechanisms naturally arise between flow, aggregate and Brownian motion, allowing fast external control with minimal intervention. Consequently, complex behaviour, analogous to those seen in living organisms, emerges, whereby aggregates can self-sustain, self-regulate, self-replicate, self-heal and can be transferred from one location to another, all within seconds. Aggregates can comprise only one pattern or bifurcated patterns can coexist, compete, endure or perish. © The Author(s) 2017

Optical waveguides written deep inside silicon by Femtosecond Laser

[No abstract available

Laser-slicing of silicon with 3D nonlinear laser lithography

Recently, we have showed a direct laser writing method that exploits nonlinear interactions to form subsurface modifications in silicon. Here, we use the technique to demonstrate laser-slicing of silicon and its applications

In-chip microstructures and photonic devices fabricated by nonlinear laser lithography deep inside silicon

Silicon is an excellent material for microelectronics and integrated photonics 1-3, with untapped potential for mid-infrared optics 4 . Despite broad recognition of the importance of the third dimension 5,6, current lithography methods do not allow the fabrication of photonic devices and functional microelements directly inside silicon chips. Even relatively simple curved geometries cannot be realized with techniques like reactive ion etching. Embedded optical elements 7, electronic devices and better electronic-photonic integration are lacking 8 . Here, we demonstrate laser-based fabrication of complex 3D structures deep inside silicon using 1-μm-sized dots and rod-like structures of adjustable length as basic building blocks. The laser-modified Si has an optical index different to that in unmodified parts, enabling the creation of numerous photonic devices. Optionally, these parts can be chemically etched to produce desired 3D shapes. We exemplify a plethora of subsurface - that is, 'in-chip' - microstructures for microfluidic cooling of chips, vias, micro-electro-mechanical systems, photovoltaic applications and photonic devices that match or surpass corresponding state-of-the-art device performances. © 2017 The Author(s)

Ultrafast laser micro-nano structuring of transparent materials with high aspect ratio

Ultrafast lasers are ideal tools to process transparent materials because they spatially confine the deposition of laser energy within the material's bulk via nonlinear photoionization processes. Nonlinear propagation and filamentation were initially regarded as deleterious effects. But in the last decade, they turned out to be benefits to control energy deposition over long distances. These effects create very high aspect ratio structures which have found a number of important applications, particularly for glass separation with non-ablative techniques. This chapter reviews the developments of in-volume ultrafast laser processing of transparent materials. We discuss the basic physics of the processes, characterization means, filamentation of Gaussian and Bessel beams and provide an overview of present applications