Biopolymer photonics

We are revisiting biopolymers in a high-tech context. Specifically, silk fibroin extracted from silkworm cocoons is a unique biopolymer that combines biocompatibility, implantability, along with excellent optical properties. We study the use of silk as an optical material for applications in biomedical engineering, photonics and nanophotonics. Silk can be nanopatterned with features smaller than 100 nm. This allows manufacturing of structures  such as (among others) holographic gratings, phase masks, beam diffusers and photonic crystals out of a pure protein film. The properties of silk allow these devices to be "biologically activated" offering new opportunities for sensing and biophotonic components. 

Nonlinear optics in optical fibers and photonic crystal fibers

Use of high intensity pulses in optical fibers provides a rich array of physical effects because of the highly nonlinear interaction between the light and the bulk constituent of the optical waveguide.

With single mode fibers, we want to investigate the scientific and technological basis for new schemes of highly secure fiber-optic based information transfer that exploits the nonlinear optical interaction between short laser pulses and matter. This regime is easily accessed by using femtosecond laser pulses in optical fibers. Among these ideas is the realization of system prototypes that use the inherently irreproducible physical properties of the optical conduit (i.e the fiber properties)used to transmit information.

A new class of fibers which manipulates light in unconventional ways has inspired a renaissance in fiber optics allowing unprecedented control on nonlinear effects, and on wavelength. These fibers are generally called photonic crystal fibers (PCFs). These unique waveguides have equally unique nonlinear behavior which manifests itself in a more dramatic way compared to conventional fiber. Furthermore, these fibers can guide light either in a solid or in a hollow core.

These new fibers have spawned a variety of applications such as supercontinuum generation from pulsed laser sources, wavelength conversion and soliton propagation; hollow core devices such as gas-laser Raman cells, particle and atom guidance; soliton formation with ultra high energy fs pulses; optical fibre sensors; intra-fibre devices; high power fibre lasers; compact solid-state pump lasers for nonlinear PCF devices; laser machining; sources for optical coherence tomography; non-silica glass PCFs for infrared transmission; and frequency metrology.

Particular interest is paid to research in mid-IR PCF, and is short PCF SC generation.

Biological imaging with nonlinear optics

We adapt ultrafast optical physics and apply the methods of nonlinear optics to imaging problems. Specific research presently pursued involves the application of adaptive feedback techniques to optimize and enhance nonlinear imaging in biological samples.

We rely on our expertise in femtosecond coherent control for enhancement of the nonlinear interaction. We are also applying our supercontinuum sources to medical imaging issues such as strategies for SC-based diffuse imaging approaches of scattering tissue.

Optofluidics

Merging the fields of microfluidics and optics has recently given rise to exciting developments in scientific and analytical approaches where light properties can be controlled by fluids and fluid flow.

We are varying the properties of photonic crystal fibers and photonic crystal by controlled introduction of fluids and biological compounds for use as sensors and active optofluidic components. We are also using siloxane rapid prototyping of optofluidic devices to serve as the basis for optical studies of physiologically relevant microflows.

Ultrafast laser interaction with biological tissues

We are bringing together optical physics and bioengineering by performing a preliminary yet systematic study  of the interplay between tightly focused, high-energy femtosecond laser pulses and engineered biological surfaces.  From a general point of view, these preliminary experiments will provide an indication on how to use lasers to cleave biological tissues while addressing the more specific goal of selective interaction with biological samples at the cellular level.    In fact, it is possible to focus laser radiation to spot sizes that are as small as a few micrometers in diameter.  These dimensions are commensurate  both with the typical sizes of cells (which range from the tens to the hundreds of microns) and with the cell nuclei.

Research News