Awards & Achievements
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Dr Shahraam Afshar Vahid

Telephone	+61 8 8313 5312
Position	Research Fellow
Email	shahraam.afshar@adelaide.edu.au
Fax	+61 8 8313 4380
Building	Physics Building
Floor/Room	G 22
Campus	North Terrace
Org Unit	Physics (School of Chemistry and Physics)

To link to this page, please use the following URL:
http://www.adelaide.edu.au/directory/shahraam.afshar

Awards & Achievements

The birth of a new discovery:

THE WORLD IS MORE NONLINEAR THAN WE THINK!!?

Read below to find out why

How did it happen:

The Standard theory of nonlinear pulse propagation in optical waveguides [1] is based on weak guidance approximation.
This theory, call it here; Scalar Nolinear Pulse Propagation (SNPP), provides good approximation to describe nonlinear processes in waveguides with low refractive index contrast (between core and cladding) and large dimensions (compared to wavelength).
SNPP, however, fails to provide an accurate picture of nonlinear processes in High index, Subwavelength Waveguides (HIS-WG) with inhomogenous structures.
- Examples of HIS-WG:

We developed a general theory; vectorial Nonlinear Pulse Propagation (VNPP), which is able to describe nonlinear processes in all waveguide, especially in HIS-WG [7,3].
One important prediction of VNPP: HIS-WG have much higher nonlinear coefficent, gamma, in the subwavelength regime compared to nthat predicted by SNPP. See here
We could not find any experimental results (by begining of 2009) that allows us to confirm the prediction of VNPP. See here
So, we decided to fabricate a subwavelength core fibre (sub 1550 nm) ourselves. Having a wonderful glass and fibre fabrication expert (Dr. Heike Ebendorff-Heidepriem), we fabricated few subwavelength core bismuth fibres.

Using these fibres with the core diameter ranging 460 nm to 550 nm, we measured their nonlinear coefficients, gamma. These values were the world record nonlinearity (at the time). Comparing these values with the predictions of VNPP and SNPP, confirmed the VNPP model. The report of this study was published as: "Small core optical waveguides are more nonlinear than expected: experimental confirmation" in Optics Letters in November 2009.

Well, this proved that:

THE WORLD IS MORE NONLINEAR THAN WE THINK !

Well, the new discovery is being recognised by the world:

Read the report in the Research Highlight section of Nature Photonics: "Beyond expectations"

Read the report (January 2010) in Photonics Spectra Magazine: "Pushing light to new limits".

Read the report in Optics and Photonics News, the monthly magazine of Optical Society of America (February 2010 issue): "Testing a New Model for Tiny Fiber Cores"

To learn more about the new VNPP theory, read our contributed chapter (chapter 11) in the new published book: "Supercontinuum Generation in Optical Fibers"

Publications

Professional Interests

Nonlinear optics in waveguides, especially in microstructured optical fibres
Design and development of nonlinear photonics devices
Photonics band gap fibres
THz waveguides
Sening using microstructured optical fibres

Files

Entry last updated: Saturday, 5 Jun 2010

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