Numerical simulation of supercontinuum generation in liquid-filled photonic crystal fibers with a normal flat dispersion profile

A photonic crystal fiber (PCF) filled with commercial index-matching liquids is designed to control the dispersion properties of PCF. Numerical simulation of supercontinuum (SC) generation in these liquid-filled PCFs is then conducted at a temperature of 25 °C. The definition of spectral flatness measure (SFM) is introduced to quantitatively describe the SC flatness. Numerical simulations are performed to study the propagation of femtosecond pulse in the liquid-filled PCFs. Results show that using the index-matching liquids in PCF, the dispersion properties of the PCF can be easily engineered without changing in the geometry. Simulations also show that 50 fs pulses with a center wavelength of 1060 nm generate relatively flat SC spectra in the 25 cm-long PCF with two Oil2-filled rings. With an applied pump power of 24 kW, a flat (SFM=0.9670) spectral bandwidth of 700 nm (900-1400 nm) is achieved. Results further demonstrate that using index-matching liquids to fill the PCF inner ring can exactly control its dispersion properties and generate a flat SC spectrum in the specified wavelength region.