Birefringence characteristics of squeezed lattice photonic crystal fibers

A numerical model of the photohic crystal fiber (PCF) with triangular lattice, squeezing triangular lattice, square lattice and rectangle lattice is presented for the first time. The concept of squeezing ratio is defined to study the influence of squeezing on the PCF s birefringence characteristics by supercell lattice method. The multi-hold rotation symmetry of photonic crystal fibers can be broke by squeezing the PCF s lattice along a certain direction, which is an important method to make PCF highly birefringent. The simulation results show that squeezing the PCF s lattice with the same airholes in the cladding can result in the high birefringence of PCF. Moreover, the influence of the airhole size on the PCF s birefringence is discussed. The sign of PCF's birefringence can be changed as the air-hole size changes, which is reported for the first time to our knowledge.