  We report a novel technique for launching broadband laser light into
liquid-filled hollow-core photonic crystal fiber (HC-PCF). It uniquely offers
self-alignment and self-stabilization via optomechanical trapping of a fused
silica nanospike, fabricated by thermally tapering and chemically etching a
single mode fiber into a tip diameter of 350 nm. We show that a trapping laser,
delivering ~300 mW at 1064 nm, can be used to optically align and stably
maintain the nanospike at the core center. Once this is done, a broadband
supercontinuum beam (~575 to 1064 nm) can be efficiently and close to
achromatically launched in the HC-PCF. The system is robust against liquid-flow
in either direction inside the HC-PCF and the Fresnel back-reflections are
reduced to negligible levels compared to free-space launching or butt-coupling.
The results are of potential relevance for any application where the efficient
delivery of broadband light into liquid-core waveguides is desired.
