The Noniinear Properties Of Micro-Structure Optical Fiber And Its Functional Devices

According the aims of the national 973 project"The basic studies of photoelectron functional device based on Micro-structure fiber(MF)": (1) opening out the mechanisms of MF tuning and high nolinearity, (2) manufacturing sots of communication photoelectron functional device based on MF, (3) manufacturing integrated photoelectron functional device based on MF, we theoretically and experimentally investigated the nonlinearity properties of the MF and the MF based functional devices. The chief contents and the innovating results are summed up as follows:(1) We investigated the wave guiding properties of MF and found that the modal cutoff profile of the Ge-doped MF shift to the low d/Λside in contrast to the pure silica MF. Moreover, we proposed that the nonlinear coefficient can be enhanced more than three orders when we tapered the Yb3+-doped MF, but there is a optimal tapering waist for a fixed structure MF and the normalized tapering length have to be longer than 30μm so that the nonlinear coefficient be enhanced to maximum. Finally, we found that the large anomalous dispersion(near 300nm/ps/km) down to short wavelength(700nm) can be achieved for the small air-hole pitch(Λ~λ) and large air hole MF.(2) We discussed the effect of the irregular structure to the properties of MF and found that the larger nonlinear coefficient of the ideal MF is, the nonlinear property is more prone to be degraded by the irregular structure, and the irregular structure make the dispersion fluctuate around the ideal value. Furthermore, random disorder air holes is more prone to make the distributions of nonlinear coefficient and dispersion dispersive than the nonuniformity. Finally, the nonlinear coefficient is more sensitive to larger pitch and smaller diameter of air holes, but the structure is benefit for holding dispersion.(3) We investigated the modal properties of MF and found that the mount and the coupling efficiency of each mode lie on the structure parameters of MF when the field incident from single mode fiber, the coupling efficiencies of the fundamental mode and the high order modes, respectively, reach the maximum and the minimum when the modal field diameter of the MF and SMF are matching. Furthermore, we found that the modes with full waveguiding symmetry have the combinated symmetry and they are degenerated, the modes only have combinated symmetry are nondegenerated. Finally, we found the multimode interference(MMI) phenomena in the MF, and the properties of the MMI lie on the structure parameters.(4) We investigated the properties of the MF grating and found the conditions for high order modes being excited in MF Bragg graging: (1) the MF supports the higher inner cladding modes guiding, (2)the higher inner cladding modes fulfill the phase matching condition. (3)coupling coefficientκi>> 0,namely, the electronic field of backward higher order inner cladding modes overlap with that of the forward fundamental mode in the grating region. And the diameter of the sensitive core of the MF not only affects the wavelength but also affects the amplitude of each resonant peak.(5) We investigated the MF based all optical switching and proposed that all optical switch can be realized when the high nonlinear photonic crystal fiber(HN-PCF) and the bidirectional pumped Er3+ doped fiber amplifier are inserted in a Sagnac loop. We theoretically deduced that the switching power is proportional to the product of the amplifier gain and MF nonlinear coefficient,so we can enhance the amplifier gain and MF nonlinear coefficient to decrease the switching power. In our experiment, the switching power of 40mW were obtained, and transmission of the signal is cosine proportional to the peak power of the control light. All the results of the experiment are in good agreement with that of the theory.(6) We experimentally investigated the MF based wavelength conversion and found that the phase matching condition can be fulfilled when wavelength of signal is near to that of the pump and the zero dispersion wavelength is far away from tuning range of the pump light, which breakthrough the confine of the zero dispersion to four wave mixing(FWM) and make the FWM based wavelength conversion more flexible. In our experiment, the maximum conversion efficiencies of -11.23dB and -11.45dB, 3dB conversion bandwidths of 78.6nm and 38.06nm for coherent and incoherent signal lights are achieved in a 20m-long HN-PCF, respectively.