Transverse propagation of ultraviolet and infrared femtosecond laser pulses in photonic crystal fibers

Abstract

We studied the influence of angular orientation of a photonic crystal fiber (PCF) on optical power that reaches the fiber core during femtosecond grating inscription at 267nm and 800nm. In our numerical study we considered two types of PCFs: three PCF designs with a standard hexagonal lattice and one highly birefringent PCF with three rows of air holes. A dedicated figure of merit, the Transverse Coupling Efficiency (TCE), is used throughout the paper to estimate the influence of the PCF cladding on laser power that reaches the core region. We found that at an inscription laser wavelength of 800nm and for a high filling factor hexagonal lattice PCF, the TCE can reach 1.4. This means that the microstructure can actually help deliver higher power to the core region of the PCF than what can be achieved with a conventional step-index fiber of similar diameter. For a highly birefringent PCF even higher TCE values (up to 2.8) can be achieved for a wide range of orientations. © 2012 Photonics Society of Poland.