Mid-infrared supercontinuum generation using dispersion-engineered Ge(11.5)As(24)Se(64.5) chalcogenide channel waveguide.

M R Karim,B M A Rahman,Govind P Agrawal

doi:10.1364/oe.23.006903

Abstract

We numerically investigate mid-infrared supercontinuum (SC) generation in dispersion-engineered, air-clad, Ge(11.5)As(24)Se(64.5) chalcogenide-glass channel waveguides employing two different materials, Ge(11.5)As(24)Se(64.5) or MgF(2) glass for their lower cladding. We study the effect of waveguide parameters on the bandwidth of the SC at the output of 1-cm-long waveguide. Our results show that output can vary over a wide range depending on its design and the pump wavelength employed. At the pump wavelength of 2 μm the SC never extended beyond 4.5 μm for any of our designs. However, supercontinuum could be extended to beyond 5 μm for a pump wavelength of 3.1 μm. A broadband SC spanning from 2 μm to 6 μm and extending over 1.5 octave could be generated with a moderate peak power of 500 W at a pump wavelength of 3.1 μm using an air-clad, all-chalcogenide, channel waveguide. We show that SC can be extended even further when MgF(2) glass is used for the lower cladding of chalcogenide waveguide. Our numerical simulations produced SC spectra covering the wavelength range 1.8-7.7 μm (> two octaves) by using this geometry. Both ranges exceed the broadest SC bandwidths reported so far. Moreover, we realize it using 3.1 μm pump source and relatively low peak power pulses. By employing the same pump source, we show that SC spectra can cover a wavelength range of 1.8-11 μm (> 2.5 octaves) in a channel waveguide employing MgF(2) glass for its lower cladding with a moderate peak power of 3000 W.

Highlights

Chalcogenide glasses (ChGs) have emerged as promising nonlinear materials having a number of unique properties that makes them attractive for fabricating planar optical waveguides and using them for application such as mid-infrared (MIR) supercontinuum (SC) generation and optical sensing [1]
Interest has grown in designing and optimizing planar waveguides made from Ge11.5As24Se64.5 chalcogenide glass for broadband MIR SC generation with suitably tailored group-velocity dispersion (GVD), including a zero-dispersion wavelength (ZDW) close to the central wavelength of the pump [11, 12]
We have numerically demonstrated MIR SC generation by using dispersion-engineered, airclad, channel waveguides designed and optimized such that they use either Ge11.5As24S64.5 chalcogenide glasses (ChGs) glass or MgF2 glass for its lower cladding material

Summary

Introduction

Chalcogenide glasses (ChGs) have emerged as promising nonlinear materials having a number of unique properties that makes them attractive for fabricating planar optical waveguides and using them for application such as mid-infrared (MIR) supercontinuum (SC) generation and optical sensing [1]. They observed a flat SC extending from 2.5 μm to 7.5 μm in 5-mm-thick bulk sample of Ge11.5As24Se64.5 glass pumped with 150 fs duration pulses with up to 20 MW peak power at a wavelength of 5.3 μm They reported theoretically that SC could be generated beyond 10 μm in a dispersion-engineered all-chalcogenide Ge11.5As24Se64.5 glass rib waveguide pumped with 250 fs duration pulses at a wavelength of 4 μm or longer. As Aeff increases, high pump powers would be required to generate SC in the long-wavelength region, which can cause damage to the ChG waveguides if relatively wider pump pulses are employed [14] For this reason we choose, for our numerical simulation, sub-picosecond pulses of 85 fs (FWHM) duration at a pump wavelength of 3.1 μm with a repetition rate of 160 kHz [45] and with low to moderate peak powers. Our calculated bandwidths are the largest reported so far for SC generated using chalcogenide glass waveguides pumped at a wavelength of 3.1 μm with a moderate peak power of 500 W

Theory

Conclusions