Philip Russel

Max-Planck Institute for the Science of Light

Keeping a tight focus on matter

Photonic crystal fibre (PCF) allows remarkable control of the propagation of guided light in structures with both hollow and solid glass cores. It has introduced a new theme to photonics – the guidance of light, in a low-loss single mode, in a microscopic hollow channel. This represents one of the most exciting opportunities in recent years, for it allows one to extend the depth of focus of a lens to km lengths – in empty space. This result, combined with the ability to control the group velocity dispersion over a wide range, has led to the highly efficient generation of tunable ultra-short deep-UV pulses in Ar gas and low threshold stimulated Raman scattering in hydrogen. It also has wide-reaching consequences for photochemistry and the laser guidance and propulsion of small particles. Solid-core PCFs have permitted efficient generation of broad-band supercontinuum light and a whole range of devices based on nonlinear optoacoustics. These are just a some examples of the many areas where PCFs have enlarged the "sphere of the possible" in fiber optics.

Eric Mazur

Area Dean of Applied Physics
Balkanski Professor of Physics
and Applied Physics

Harvard University

Nonlinear optics at the nanoscale

We explore nonlinear optical phenomena at the nanoscale by launching femtosecond laser pulses into long silica nanowires. Using evanescent coupling between wires we demonstrate a number of nanophotonic devices. At high intensity the nanowires produce a strong supercontinuum over short interaction lengths (less than 20 mm) and at a very low energy threshold (about 1 nJ),  making them ideal sources of coherent white-light for nanophotonic applications. The spectral broadening reveals an optimal fiber diameter to enhance nonlinear effects with minimal dispersion. We also present a device that permits a number of all-optical logic operations with femtosecond laser pulses in the nanojoule range.

David J. Richardson

Optoelectronics Research Centre (ORC)

University of Southampton

Emerging Fibre Technology for Next Generation Telecommunication Networks

Driven by the relentless 40% per annum growth rate in internet data, it is already apparent that the next generation of telecommunication networks will need to be radically different from previous implementations, coherent detection along with powerful digital signal processing will be deployed to maximise the available capacity of each fiber strand within the network. However, applied in isolation these techniques will only delay the inevitable "capacity crunch" by a few years due to limitations in the capacity of conventional single mode fibre imposed by optical nonlinearity and the EDFA bandwidth. Without radical innovation in the basic internet infrastructure future internet growth is likely to be severely constrained. Research into new transmission techniques and associated fibres and amplifiers is therefore now urgently required.

In this presentation I shall review and discuss some of the potential technological options (most exploiting some form of spatial division multiplexing) and consider their potential and viability of these from a capacity, practicality and power handling perspective. Other potential applications of the technology beyond communications will be discussed.

Xingde Li

PhD, Department of Biomedical Engineering

Johns Hopkins University

Translational Fiber-optic Endomicroscopy Technologies

The past 20 years have witnessed rapid developments of high-resolution optical imaging technologies, such as multiphoton fluorescence microscopy, harmonics generation microscopy, and optical coherence tomography (OCT). These technologies are noninvasive in nature, and can potentially function in a form of "optical biopsy" for clinical diagnosis and surgical guidance, with the resolution approaching that of standard histology but without the need for tissue removal. Clinical translation of these technologies for in vivo applications, however, requires ultracompact and flexible probes that can access internal organs. This presentation will discuss our recent developments of ultrathin endomicroscopy technologies that literally miniaturize a bench-top scanning laser microscope down to a flexible, all-fiber-optic, scanning probe of an ~2-2.5mm diameter. The technology involves vertical integration of novel optical fibers, high-performance micro-optics, and inexpensive MEMS technologies. The endomicroscope is capable of performing two-photon fluorescence and second harmonic generation microscopy of biological tissues with the imaging performance approaching standard microscopy. Preliminary results from cancer imaging with the endomicroscope will be presented. In addition, fiber-optic endomicroscopy technologies for OCT applications will also be discussed.

Xi-Cheng Zhang

Director
Center for THz Research
School of Science

Rensselaer Polytechnic Institute, USA

Terahertz wave air photonics

Since the early 90s, the technology of THz time domain spectroscopy has been largely applied to measurements of semiconductors, electro-optic crystals, and selected chemical, biological and explosive materials. However, the majority of these measurements are linear transmissions or reflection measurements. Here I will highlight THz wave sensing and imaging science, technology, and its applications with an emphasis on spectroscopic and imaging capabilities. The most recent results of using air (and selected gases) as the emitter and sensor material for both generation and detection of broadband THz waves will also be reported. Air, especially ionized air (plasma), has been used to generate intense peak THz waves (THz field > 1.5 MV/cm) with a broadband spectrum (10% bandwidth from 0.1 THz to 46 THz).

We have developed THz radiation-enhanced-emission-of-fluorescence (REEF) and THz-enhanced acoustic (TEA) techniques. By "seeing" the fluorescence, or "hearing" the sound, coherent detection of THz waves at standoff distance is feasible.

Kazuo Hotate

Department of Electrical Engineering and Information Systems
Graduate School of Engineering

The University of Tokyo

Distributed Fiber Sensing Technology: Currents and Challenges

In this talk, distributed fiber sensing technologies are explained, showing principles and applications.  Time domain technologies have been developed, at first, as ways to analyze the distributed information along the fiber.  For example, in distributed strain measurement through the nature of Brillouin scattering, basic systems showed limitation in spatial resolution of about 1m.  However, novel phenomena and new systems have recently been proposed, and the resolution has been much improved.  Optical correlation domain techniques, in which interference of continuous lightwaves is manipulated to obtain the distributed information, have already realized superior performances, such as 1.6 mm spatial resolution and 1 kHz sampling rate, in the fiber Brillouin distributed strain sensing.  Applications, such as aircraft health monitoring, have also been demonstrated.  Recently, "Brillouin dynamic grating" in a polarization maintaining fiber has been studied, and created various novel applications, including simultaneous distributed measurement of strain and temperature.  With the correlation domain technique, other schemes, such as multiplexing systems for long-length FBG distributed sensors, have also been developed.

Jorge Ojeda-Castañeda

University of Guanajuato, Mexico

Phase-Space tools for designing novel imaging devices

In applied optics, often one is faced with a trade-off between two functions that are a Fourier transform pair. Phase-space representations are useful for an insightful analysis of the limitations, as well as for designing methods that somehow overcome this trade-off. We discuss the use of certain complex amplitude masks that reduce the impact of focus errors on the modulation transfer function (MTF). And based on the space-time analogy, we show that a similar procedure can be usefully exploited for correcting residual time aberrations in temporal lenses.