Wang Zhuyuan

Three-Photon Absorption and Upconversion Fluorescence Properties of Series 1,3,4-Oxadiazole Derivatives

A newly synthesized 1,3,4-oxadiazole derivatives have been studied using a femtosecond Ti:sapphire laser system. The series molecules present strong three-photon absorption and frequency upconversion fluorescence at wavelengths from 1205nm to 1575nm. Furthermore, there is no proportional relationship between three-photon absorption cross sections and the chemical structure transformation from monomer, dimer to trimer. Effective charge-transfer distance by π-conjugation bonds may be the contributing factor. In the experimental design, the far-field intensity distribution of femtosecond laser beam has been taken into account. We give the optimized analytical solution of nonlinear transmission in a three-photon absorption (3PA) process when the incident beam has a Gaussian transverse spatial profile.

Behaviour of a wideband double-pass discrete Raman amplifier with simultaneous reflection of signals and multi-pump

The behaviour of a high efficient double-pass discrete Raman amplifier with 80nm bandwidth was studied theoretically and experimentally. In this Raman amplifier, by using a one-end gilt fibre as the broadband reflector, signals and multi-pump are simultaneously reflected to propagate through the gain fibre for a second time in the opposite direction of the input. An increase in net gain of more than 150% has been achieved compared with that in the typical co-pumped Raman amplifier. The advantages of this new configuration have been studied by comparing with the currently existing Raman amplifier configurations. Also, the influencing factors for the gain increase have been analysed, including the pump-to-pump Raman interactions and the length of gain fibre.