Design of solid core photonic bandgap fibers for visible supercontinuum generation

Vincent Pureur,John M Dudley

doi:10.1016/j.optcom.2010.11.037

Abstract

We present a numerical study of two dimensional solid core photonic bandgap fiber design criteria for their particular application to blue/visible supercontinuum generation. By exploiting their strong frequency-dependent dispersion when compared to index guiding micro-structured fibers, we highlight the design of solid core photonic bandgap fibers to fulfill group index matching conditions between the first ejected optical soliton and the trapped dispersive wave generated in the visible wavelength range. We study how these matching conditions depend on the opto-geometrical parameters of the micro-structured cladding, and we use frequency-domain numerical simulations to determine the expected supercontinuum spectral characteristics for selected cases. We investigate design criteria to generate short wavelengths by pumping in such photonic bandgap fibers in different pulse duration regimes and we identify a novel class of short wavelength (blue/visible) supercontinuum generation in the 3rd bandgap of a typical structure by pumping into the 2nd bandgap through a high attenuation spectral region.

Highlights

The generation of broadband supercontinuum spectra has attracted much interest over the last decade since the advent of photonic crystal fiber (PCF) [1–5]
One approach that has been extensively studied is the mechanism whereby a dispersive wave (DW) generated in the normal group velocity dispersion (GVD) regime is trapped by a soliton propagating in the infrared in the anomalous GVD regime such that there is enhanced frequency shifting to shorter wavelengths [7–10]
In order to achieve this, group index matching conditions must be fulfilled between the dispersive wave and the soliton, and this effect has been observed experimentally in the visible range in index guiding PCFs both in the picosecond and CW pumping regime pumping around 1060–1080 nm [11–13]

Summary

Introduction

The generation of broadband supercontinuum spectra has attracted much interest over the last decade since the advent of photonic crystal fiber (PCF) [1–5]. Wavelength component generation in PCF, one way is to decrease water absorption around 1.38 μm from typically 600 dB/km to about 90 dB/km by reducing surface contamination during the fabrication process through chemical cleaning [14] Another way is to modify the group index curve of the fundamental core guided mode by tailoring the geometry of the photonic crystal cladding and the core size and by keeping the zero dispersion wavelength (ZDW) close enough to the pump. Motivated by recent numerical studies showing energy transfer between two different transmission bands across a spectral region of high attenuation [17], we simulate trapped dispersive wave generation in the blue edge of the 3rd bandgap of a typical structure by pumping into the anomalous GVD regime of the 2nd transmission band in order to highlight the potential of PBG fibers to generate blue/ visible components

Solid core photonic bandgap fibers: group index matching

Group index curve optimization and supercontinuum generation

Varying Δn

Discussion

Energy transfer across different PBG orders

Conclusion