An all-optical demultiplexing of 40-Gb/s DPSK OTDM channels by using Raman-amplifier-soliton-compressor (RASC) flexible control-window is demonstrated. In comparison with other scheme, the function of RASC is not only as a control gate controller but also to amplify the signal with picosecond width-tunable output signal. Error free operation was achieved for the proposed all-optical 1:4 demultiplexer over all time demultiplexed 10 Gb/s return-to-zero (RZ)-differential phase-shift keying (DPSK) signals with less than 2-dB power penalties at 10(-9) bit-error-rate (BER). The experimental results show that this scheme is expected to be scalable toward higher bit-rates.

We investigated the performance of random dye lasers based on metal-fluorophore distance to study the effect of plasmonics through localized surface plasmons. The silver nanoparticles were coated with various silica thicknesses and mixed with Rhodamine 6G in methanol solution to provide gain to the system. The samples were pumped by a Q-Switched Nd:YAG green laser with nanosecond-pulsewidth and the emission light was collected by a spectrometer. The overlapping of extinction spectra of silver nanoparticles/silver-coated silica nanoparticles with the absorption and/or fluorescence of Rhodamine 6G indicates the localized surface plasmon effects. Increasing the metal-fluorophore distance decreases the localized surface plasmon effects result in increase of lasing threshold and decrease of emission peak intensity.

A random laser is an optical device that depends on multiple light scattering and gain to provide the feedback mechanism and light amplification respectively. A random laser is different with a regular laser where the regular laser needs a cavity for the feedback mechanism. Multiple light scattering can be considered detrimental in the regular laser but in the random laser, multiple light scattering can increase the path length of light in the active medium. This article studies the operation principles and characteristics of random lasers including the history and applications of the lasers. The theories of light scattering and light amplification are properly explained, followed by a discussion on characteristics of random lasers in terms of random laser emission, emission linewidth and coherence. Furthermore, the unique characteristics of random lasers can contribute to many applications leading to promising element for the future medical and biosensing development.