Ali A. Said

Fabrication of high-aspect ratio, micro-fluidic channels and tunnels using femtosecond laser pulses and chemical etching.

We present novel results obtained in the fabrication of high-aspect ratio micro-fluidic microstructures chemically etched from fused silica substrates locally exposed to femtosecond laser radiation. A volume sampling method to generate three-dimensional patterns is proposed and a systematic SEM-based analysis of the microstructure is presented. The results obtained gives new insights toward a better understanding of the femtosecond laser interaction with fused silica glass (a-SiO(2)).

Microfluidic sorting system based on optical waveguide integration and diode laser bar trapping

Effective methods for manipulating, isolating and sorting cells and particles are essential for the development of microfluidic-based life science research and diagnostic platforms. We demonstrate an integrated optical platform for cell and particle sorting in microfluidic structures. Fluorescent-dyed particles are excited using an integrated optical waveguide network within micro-channels. A diode-bar optical trapping scheme guides the particles across the waveguide/micro-channel structures and selectively sorts particles based upon their fluorescent signature. This integrated detection and separation approach streamlines microfluidic cell sorting and minimizes the optical and feedback complexity commonly associated with extant platforms.

Integrating optics and micro-mechanics in a single substrate: a step toward monolithic integration in fused silica.

We present a novel optical sensor concept that merges integrated optics and micro-mechanics in a monolithic substrate. This concept pushes microsystems integration and defines a new class of monolithic optical microsystems where only optical signals are processed. As an illustration, we present a high-precision, monolithic, glass-based, micro-displacement sensor. Our displacement sensor is made out of a single piece of glass through a two-step process based on femtosecond laser illumination followed by chemical etching.

Scanning thermal microscopy and Raman analysis of bulk fused silica exposed to low-energy femtosecond laser pulses

Low energy femtosecond laser pulses locally increase the refractive index and the hydro-fluoric acid etching rate of fused silica. These phenomena form the basis of a direct-write method to fabricate integrated glass devices that are of particular interest for optofluidics and optomechanical applications. Yet the underlying physical mechanism behind these effects remains elusive, especially the role of the laser polarization. Using Scanning Thermal Microscope and Raman spectrometer we observe in laser affected zones, a localized sharp decrease of the thermal conductivity correlated with an increased presence of low-number SiO(2) cycles. In addition, we find that a high correlation exists between the amount of structural changes and the decrease of thermal conductivity. Furthermore, sub-wavelength periodic patterns are detected for high peak power exposures. Finally, our findings indicate that, to date, the localized densification induced by femtosecond laser pulses remains well below the theoretical value achievable in mechanically densified silica.

Nanoindentation and birefringence measurements on fused silica specimen exposed to low-energy femtosecond pulses

Femtosecond laser pulses used in a regime below the ablation threshold have two noticeable effects on Fused Silica (a-SiO2): they locally increase the material refractive index and modify its HF etching selectivity. The nature of the structural changes induced by femtosecond laser pulses in fused silica is not fully understood. In this paper, we report on nanoindentation and birefringence measurements on fused silica exposed to low-energy femtosecond laser pulses. Our findings further back the hypothesis of localized densification effect even at low energy regime.

Thermal conductivity contrast measurement of fused silica exposed to low-energy femtosecond laser pulses

Femtosecond laser irradiation has various noticeable effects on fused silica. Of particular interest, pulses with energy levels below the ablation threshold can locally increase the refractive index and the material etching selectivity to hydrofluoric acid. The mechanism responsible for these effects is not yet fully understood. In this letter, the authors report on local thermal conductivity mapping of laser-affected zones. It is found that these zones exhibit a lower thermal conductivity at room temperature.

Monolithic optofluidic ring resonator lasers created by femtosecond laser nanofabrication

We designed, fabricated, and characterized a monolithically integrated optofluidic ring resonator laser that is mechanically, thermally, and chemically robust. The entire device, including the ring resonator channel and sample delivery microfluidics, was created in a block of fused-silica glass using a 3-dimensional femtosecond laser writing process. The gain medium, composed of Rhodamine 6G (R6G) dissolved in quinoline, was flowed through the ring resonator. Lasing was achieved at a pump threshold of approximately 15 μJ mm(-2). Detailed analysis shows that the Q-factor of the optofluidic ring resonator is 3.3 × 10(4), which is limited by both solvent absorption and scattering loss. In particular, a Q-factor resulting from the scattering loss can be as high as 4.2 × 10(4), suggesting the feasibility of using a femtosecond laser to create high quality optical cavities.

Monolithic Three-Dimensional Integration of Micro-Fluidic Channels and Optical Waveguides in Fused Silica

This paper presents dramatic improvements in the micro-fabrication of three-dimensional microfluidic channels and high-aspect ratio tunnels within the bulk of a fused silica substrate. We also report the fabrication of optical waveguides within the same substrate, which is a major step towards the integration of sensing capabilities within microfluidic networks. This integrated device, which combines both fluidic channels and optical waveguides, opens new opportunities in bio- and chemical sensing. The flexibility of the improved manufacturing process offers substantial new design capabilities, especially for single channel probing and massively parallel processing and sensing.

Manufacturing of high quality integrated optical components by laser direct-write

The index of refraction of most glasses can be permanently changed by exposure to femtosecond laser pulses. This effect can be quite strong, allowing for the fabrication of various two-dimensional or three-dimensional light guiding structures. Passive optical waveguides, splitters, couplers, and long period gratings, have been manufactured using this femtosecond direct-write technique. Active waveguides have also been produced with this method.We describe recent work at Translume in femtosecond direct write to produce waveguide-based devices characterized by low insertion loss and low birefringence. Performance data, including optical characteristic and environmental test reliability, is presented.The index of refraction of most glasses can be permanently changed by exposure to femtosecond laser pulses. This effect can be quite strong, allowing for the fabrication of various two-dimensional or three-dimensional light guiding structures. Passive optical waveguides, splitters, couplers, and long period gratings, have been manufactured using this femtosecond direct-write technique. Active waveguides have also been produced with this method.We describe recent work at Translume in femtosecond direct write to produce waveguide-based devices characterized by low insertion loss and low birefringence. Performance data, including optical characteristic and environmental test reliability, is presented.

MICRO-MIRROR STEERING OF DIODE ARRAY BEAMS

Femtosecond laser processing is well known for precise ablation of materials with insignificant heat effects. With commercially available power of a few watts, femtosecond lasers are suited for micromachining applications. However, as innovations and hybrid processes are developed, the field of femtosecond laser applications advances and broadens.Femtosecond laser processing is well known for precise ablation of materials with insignificant heat effects. With commercially available power of a few watts, femtosecond lasers are suited for micromachining applications. However, as innovations and hybrid processes are developed, the field of femtosecond laser applications advances and broadens.