Supercontinuum generation with spiral fibers

In previous posts (Stacking the spiral, magic of equiangular spirals, my research) I have talked about the properties of spiral PCF focusing especially on the modal properties which gives us dispersion tunability as well as great confinement (hence large non-linearity). This has applications for Supercontinuum Generation (SCG) and Second Harmonic Generation (see another paper).

In this post I talk a little about studying SCG in the Equiangular Spiral PCF (ES-PCF) with numerical simulation (see the paper).

To begin with we used the Finite Element Method (FEM) to design and optimize the ES-PCF. We changed the spiral properties and ran simulations to get a design with very low dispersion (the total dispersion from 1.5 μm – 2.3 μm, varies very little, in the range of ±4 ps/nm/km. In addition, the ES – PCF exhibits three ZDWs at 1.52, 1.88 and 2.22μm which can make multi – wavelength pumping possible).

The next big step was to simulate SCG by solving the Generalised Non Linear Schrodinger Equation (GNLSE) using a split-step Fourier method. This allows us to look at how the SCg evolves in the ES-PCF as a function of a) pump power b) fiber length c) pumping at different wavelengths. We found that for the pump wavelength at 1557 nm and average pump power of 11.2 mW, SCG bandwidth > 3 µm (970 nm – 4100 nm) at 40 dB below the peak spectral power. In the same fiber, at pump wavelength 1930nm and average pump power of 12mW the SC bandwidth was more than 2 octaves (1300 nm – 3700 nm).

The paper can be accessed here.

The importance of this paper is on more than 1 count:

1. It shows a fiber design that has flat dispersion over a very large wavelength range: 1800nm
2. This fiber has the potential of multi wavelength pumping for SCG.
3. The sueprcontinuum generated is broadband and flat, at much lower pumping powers than reported in several studies
4. Through numerical simulation we can help design and characterize optical components, reducing time and money in the fabrication cycle.

I feel that when experimental and theoretical work goes hand in hand the gains are far more than the sum of the individual parts!
So I would be really happy to work with an experimental group on this!


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