Archive for the ‘microstructure’ category

The world is more nonlinear than we think

October 16, 2009

A team of scientists from the Institute for Photonics and Advance Sensing (IPAS) led by Dr. Shahraam Afshar have recently shown that optical fibres are more optically nonlinear than it was thought before. Through a fundamental study of optical nonlinear processes in optical fibres, Shahraam Afshar and his team have shown that the standard theories of nonlinear optical processes in waveguides have serious limitations when it comes to waveguides with sub-wavelength structures (nano-scale structures) made from high refractive index materials.

Theoretical simulation of a fibre mode

Theoretical simulation of a fibre mode

By developing a new and general theory of nonlinear optical processes, they have not only addressed these limitations but have also predicted new processes or effects that could have not been observed with the standard theories. The most important prediction of the new theory is that the light can be confined within an area twice smaller than fundamentally thought to be the minimum area. This results in higher light intensity, which in turn leads to higher nonlinearity of optical waveguides, which is described through a parameter called effective nonlinear coefficient.

gVsDiam

Variation in the nonliear coefficent as a function of core diameter as perdicted by the different models. SM: Standard Model, ASM: , VNSE: , VNSE ORTH:

Afshar’s new theory predicts that the effective nonlinear coefficient of optical waveguides, can be factor 2 or more higher than what is expected according to the standard theory. Such prediction greatly affects the design and performance of nonlinear photonic devices. Utilizing the fabrication facility of IPAS, a newly formed institute led by Pro. Tanya Monro, the team has recently been successful to fabricate the world’s smallest core fibre with record nonlinear coefficient. Using these fibres Afshar’s team has recently confirmed experimentally the prediction of their new theory. The results of these fundamental theoretical and experimental breakthroughs have been published in prestigious journals and attracted a lot of interest among the experts in the field.

Experimental confirmation of the change in nonlinearity as a function of core diameter, as predicted by the new model.

Experimental confirmation of the change in nonlinearity as a function of core diameter, as predicted by the new model.

The IPAS institute of the University of Adelaide has become a pioneer in establishing that:

The world is more nonlinear than we think

References

(1) S. Afshar V. and T. M. Monro, “ A full vectorial model for pulse propagation in emerging waveguides with subwavelength structurespart I:Kerr nonlinearity, ” Optics Express 17, 2298–2318 (2009).

(2) M. D. Turner, T. M. Monro and S. Afshar V., “ A full vectorial model for pulse propagation in emerging waveguides with subwavelength structures part II: Stimulated Raman Scattering, ” Optics Express 17, 11565–11581 (2009).

(3) S. Afshar V., W. Zhang and T. M. Monro, “ Experimental confirmation of a generalized definition of the effective nonlinear coefficient in emerging waveguides with subwavelength structures” CThBB6, CLEO Conference, Baltimore, USA (2009).

(4) T. M. Monro, W. Zhang, H. Ebendorff-Heiperiem, and S. Afshar V., “Emerging Nonlinear Optical Fibers: Revised Fundamentals, Fabrication and Access to Extreme Nonlinearity”, IEEE Journal of Quantum Electronics, Nov. Issue (2009)

(5) S. Afshar V., W. Zhang, H. Ebendorff-Heiperiem, and T. M. Monro, “Small core optical waveguides are more nonlinear than expected; Experimental confirmation”, Optics Letters, Accepted for publication.

Book Chapter:
(6) S. Afshar V., M. D. Turner and T. M. Monro, “Nonlinear optics in emerging waveguides: revised fundamentals and implications” in Supercontinuum Generation in Optical Fibers, edited by J. M.
Dudlley and J. R. Taylor, Cambridge University Press, under publication

Exciting seminar by Phillip Russel

April 3, 2009

The CoEP is pleased to announce that it will be hosting a seminar on Thursday the 9th of April given by Prof Phillip Russel. This event is a free public lecture and all are welcome.

Prof Russell is considered a ‘godfather’ of microstructured optical fibre research worldwide, and is known for giving quite insightful talks.

Currently he serves as the Director of the newly founded Max-Planck Institute for the Science of Light and Professor of Physics at the University of Erlangen-Nuremberg, Germany.  He obtained his PhD (1979) degree at the University of Oxford and has subsequently held positions in France, Germany, the USA and the UK.  He specializes in the behaviour of light in periodically structured materials and waveguides, and was the founder of BlazePhotonics Ltd (2001 to 2004) whose aim was the exploitation of photonic crystal fibre. Prof Russell is a Fellow of the Royal Society and the Optical Society of America and has won several international awards for his research.

The details of the talk are are given below, followed by the abstract.

Location: Kerr Grant theatre, Physics building, University of Adelaide.

Time: 6pm

Glass cages for catching light

In its most common form, photonic crystal fibre (PCF) consists of a hair-thin thread of glass with a ‘cage’ of tiny hollow channels running along its length. This periodic lattice makes it possible to guide light in new ways, for example, to cage it inside an empty core. In such a hollow-core PCF one is able for the first time to eliminate the diffraction of light over km distances in empty space. By filling the core with gases, nonlinear gas-laser interactions can be enhanced by seven orders of magnitude in the best low-loss PCFs. Hollow-core PCF can also be used, for example, to laser-guide small particles, molecules or atoms along a curved path. In PCFs with micron-sized solid-glass cores, the chromatic dispersion can be radically altered, which has led to a revolution in the brightness of broad-band white-light sources. The most recent example of such  supercontinuum” sources is nearly six orders of magnitude brighter than an incandescent lamp, yielding up to 10 mW/nm spectral intensity at visible and near IR wavelengths. The lattice of hollow channels also gives rise to phononic band gaps and families of multi-GHz guided acoustic modes, which themselves interact strongly with light, creating unusual forward and backward Brillouin spectra. By filling the hollow channels with metals such as silver or gold, one can explore plasmon resonances in arrays of parallel nanowires. Through its unique and varied characteristics, PCF is creating many new opportunities in diverse areas of fundamental and applied research.


New paper published in Optics Express

October 23, 2008

Kris, Shahraam and Tanya recently had a paper published in Optics Express. You can find the Optics Infobase abstract and full-text .pdf link here.

Citation: K. J. Rowland, S. Afshar V., and T. M. Monro, “Bandgaps and antiresonances in integrated-ARROWs and Bragg fibers; a simple model,” Opt. Express 16, 17935-17951 (2008)

NewsFlash – new positions available!

June 27, 2008

Six Postdoctoral Fellowships and one Technician positions have just been advertised. More information HERE.

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Six Postdoctoral positions

June 27, 2008

A rare opportunity to join our vibrant team at a time of rapid expansion. Apply for a Postdoctoral Fellowship for your chance to engage in cutting edge interdisciplinary science with real world applications.

Details at adelaide.edu.au/jobs

Technician

June 27, 2008

We are seeking a skilled Technical Support Officer to be involved in installing, operating, maintaining and upgrading a range of specialised equipment for use in the fabrication of optical fibres.

Details at adelaide.edu.au/jobs