Visible to near-infrared continuum generation in a water-core photonic crystal fiber

Abstract

Photonic crystal fibers (PCFs) are optical fibers whose core is surrounded by a regular matrix of holes that is responsible for light confinement and guidance. These waveguides have found numerous potential applications, many of which are based upon the high efficiency with which nonlinearity‐driven spectral broadening (supercontinuum generation) is obtained in solid‐core PCFs. Another asset of PCFs is that their structure can be filled with liquids or gases, which then efficiently interact with the guided light. The possibility of obtaining supercontinuum generation in a PCF whose core is filled with highly nonlinear liquids has been recently theoretically studied. The insertion of liquids in PCFs introduces a new degree of freedom with which the efficiency of nonlinear effects can be maximized. Here, we experimentally demonstrate the generation of a supercontinuum spectrum in a PCF whose hollow core was selectively filled with distilled water and which is pumped near water's zero dispersion wavelength. A ∼500‐nm‐wide spectrum (measured at −20 dB) was obtained with 60 fs pulses of 1.5 MW peak power, which is ∼5 times as wide as the spectrum obtained in a classical (bulk) water continuum generation setup with a ∼40 times higher peak power.