Reporter:Peter R. Herman
Affiliation: University of Toronto , Canada
Time: At 2:00PM, May 30, 2016
Place: Yizhi Meeting Room

Abstract: The manipulation of femtosecond laser light inside transparent media can be directed on varying interaction pathways of microexplosions, photochemistry, and self-focusing filamentation to open new directions for creating dense memory storage, three-dimensional (3D) optical circuits, 3D microfluidic networks and high-speed scribing tracks. The presentation follows these fundamental interactions towards controlling laser processes in various 3D geometries that enable highly functional and compact devices to form with the benefits of 3D seamless integration in delicate glass fibers through to thin films. 

In one approach, strong nonlinear interactions are demonstrated to align with Fabry-Perot interference fringes and generate narrow nano-length scale plasma zones of 20 to 45 nm thickness that follow the predicted ？/2nfilm fringe spacing in SiNx and SiOx film. Micro-disk explosions are shown to cleave open the film into sub-wavelength internal cavities at single or multiple periodic depths or to eject fractional film segments at controllable depths. This new form of high-resolution patterning is aimed at new directions of writing multilevel micro- or nano-fluidic channels for lab-in-a-film, film coloring, 3D surface patterning, nanofluidics, capacitor trimming, and nano-optic fabrication. This new opportunity holds promise to further improve the functionality of CMOS microelectronics and photonics, photovoltaics, MEMS, LED, lab-on-a-chip devices where thin films are widely deployed during their manufacture.

Femtosceond laser processing is further adapted to write 3D optical circuits within the fiber cladding and present a practical means for coupling light efficiently with the fiber core waveguide. Modification of the core waveguide further enables tuning of the modal properties, enabling multi-mode interferometers to be embedded in-fiber for various applications in power tapping, spectral filtering and polarization tuning. Chemical etching of laser-generated nanogratings are also applied to embed microfluidic channels, micro-optical devices and optical resonator components in arbitrary positions in the fiber.  The laser writing overall provides a flexible integration of fiber-cladding photonics and microfluidics on which to build 3D opto-fluidic microsystems in our common base of optical networks through to compact biomedical probes.  The approach promises to reduce fabrication and packaging costs and to enable highly functional all-fiber microsystems for optical communications, fiber lasers, and sensing.  Examples of integrated approaches in lab-in-a-fiber devices and smart medical catheters are presented.

Biography: Peter R. Herman received the B.Eng. degree (1980) in Engineering Physics at McMaster University.  He earned MASc (1982) and PhD (1986) degrees studying lasers and diatomic spectroscopy in the Physics Department at the University of Toronto that followed with a post-doctoral position at the Institute of Laser Engineering in Osaka University, Japan (1987) to the study of laser-plasma physics and x-ray lasers. He joined the Department of Electrical and Computer Engineering at the University of Toronto in 1988 where he holds a full professor position.  Professor Herman directs a large and collaborative research group that develops and applies laser technology and advanced beam delivery systems to control and harvest laser interactions in new frontiers of 3-D nanofabrication.  Our mantra is: “We begin with light and we end with light devices.” To this end we are inventing new methods for processing internally inside optical materials that carve out highly compact and functional lightwave circuits, microfluidics, optofluidic systems, biophotonic sensors, and smart medical catheters. Our end goals are inventing new manufacturing processes and extending optical device and Lab-on-a-chip concepts towards more compact Lab-in-a-fiber and Lab-in-a-film microsystems. Professor Herman is OSA fellow, holds several patents, spun out one company (FiLaser), and has published over 300 papers in journals and conference proceedings.