Abstract
We demonstrate supercontinuum generation in unspliced as well as in integrated CS(2)-filled capillary fibers at different pump wavelengths of 1030 nm, 1510 nm, and 1685 nm. A novel method for splicing a liquid-filled capillary fiber to a standard single-mode optical fiber is presented. This method is based on mechanical splicing using a direct-laser written polymer ferrule using a femtosecond two-photon polymerization process. We maintain mostly single-mode operation despite the multi-mode capability of the liquid-filled capillaries. The generated supercontinua exhibit a spectral width of over 1200 nm and 1000 nm for core diameters of 5 μm and 10 μm, respectively. This is an increase of more than 50 percent compared to previously reported values in the literature due to improved dispersion properties of the capillaries.
Highlights
Optical fibers confine light in a very small area over a long interaction length
To overcome the limitation of a standard silica fiber with moderate nonlinear refractive index and strong material absorption above 2.4 μm, fibers filled with highly nonlinear liquids have recently come into focus [3,4,5,6,7,8]
They offer striking possibilities in the field of optofluidics because of a 100 times larger nonlinear refractive index compared to fused silica [9] and a high transmission range up to 12 μm with few absorption peaks in the mid-IR spectral region [10], which is crucial for extending supercontinua far into the mid-IR
Summary
Optical fibers confine light in a very small area over a long interaction length. For that reason fibers are especially suited for enhancement of nonlinear effects such as supercontinuum generation [1]. A different intriguing approach developed by Xiao et al [7] is based on mechanical splicing a capillary fiber to a standard telecom fiber by using a large diameter tapered capillary as sleeve In this case, difficulties can arise from trapped air that can penetrate into the liquid-filled core when both fibers are spliced together which leads to significant propagation losses. We present a novel approach for an integrated liquid-filled fiber device which is based on mechanical splicing with the help of femtosecond two-photon direct laser writing of a polymer ferrule. The splicing process is highly reproducible due to the high accuracy of direct laser writing This method is suited for generating supercontinuum in liquid-filled capillaries that are not exclusively single-mode by maintaining mostly the fundamental mode of the spliced single-mode fiber due to the accurate mutual alignment. Afterwards, the fabrication process of the integrated liquid-filled device based on mechanical splicing is described, followed by the experimental supercontinua of the integrated capillaries
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