Study On Supercontinuum And Entangled Photon-Pairs Generation In Photonic Crystal Fiber

This dissertation covers both the SuperContinuum(SC) and Entangled photon-pairs generation in Photonic crystal fiber (PCF). As PCF has several advantages such as adjustability of zero-dispersion wavelength in a large region and high nonlinear coefficient, we use it to generate SC and correlated photon-pairs instead of conventional fiber.Due to the fact that SuperContinuum (SC) has ability to generate multi-wavelength-channel pulse source, SC generation at regime close to 1.55μm has the potential to be an important application to dense wavelength-division-multiplexed(DWDM) optical networks. In addition, study on physical processes underlie the SC generation is also a very meaningful theoretical work.Entangled photon pairs are very important resources in quantum key distribution (QKD) system. Four-wave-mixing (FWM) in optical fiber is a promising candidate for a quantum correlated photon-pairs source, because photons generated from such sources can be coupled into transmission fiber very efficiently. AS mentioned above, a photon-pair source at the 1.55-μm band is especially important for long-distance QKD system over optical fiber networks.The research works in the dissertation are summarized as follows:We demonstrate SuperContinuum (SC) generation of a normal-dispersion photonic crystal fiber (PCF) using picosecond pulse excitation. In experimental analyses, a 237-nm broadband infrared continuum was generated pumped at 1550nm (normal dispersion regime) by 1.6-ps pulses from an erbium-doped fiber laser. In addition, we conducted the numerical analyses of SC based on generalized nonlinear Schrodinger equation. The results have been applied to investigating the dominant physical processes underlie the generation of the SC generation. We conclude that dispersion, self-phase modulation (SPM), four-wave-mixing (FWM) and Raman scattering are the determinant of SC generation rather than fission of soliton in normal-dispersion PCF.We demonstrate a high quality and high counting rate source of correlated photon pairs through four-wave-mixing (FWM) by pumping a 40m dispersion-flattened photonic crystal fiber (PCF). Using 1550nm pump pulses, we detected correlated signal (1545nm) and idler (1555nm) photons at a rate of 1.43 kHz with a coincidence/accidental coincidence (C/A) contrast of 8. Such a system can be used as the source of quantum key distribution system with a bit error rate 6%.