  The recent development of devices based on novel nonlinear materials like
chalcogenides (ChGs), silicon (Si) and other semi-conductors has revolutionized
the field of nonlinear photonics [1,2,3]. Among the nonlinear effects observed
in these materials, four-wave mixing (FWM) is the process that finds the most
applications including wavelength conversion [4], optical regeneration [5,6],
optical delay [7], time-domain demultiplexing[8], temporal cloaking[9] and
negative refraction[10]. Although FWM has been observed in several media
including chalcogenides [11,12,13,14], silicon[15, 16], bismuth [17] and silica
[18,19], there is a continued quest for devices that realize efficient and
broadband FWM while offering compactness, low-power consumption and
compatibility with optical fibers. Here, we demonstrate the fabrication of 10
cm long polymer cladded chalcogenide (As2Se3) microwires to realize FWM-led sub
watt threshold (70-370 mW) wavelength conversion with a 12 dB bandwidth as
broad as 190 nm, and conversion efficiency as high as 21 dB. This represents a
3-30 \times increase in bandwidth and 30-50 dB improvement in conversion
efficiency over previous demonstrations in tapered and microstructured
chalcogenide fibers [11,13,14]. These properties, combined with low loss (< 4
dB), ease of fabrication, and the transparency of As2Se3 from near to mid
infrared regions (1 15 \mum) [20] make this device a promising building block
for lasers, optical instrumentation and optical communication devices.
