A mid-IR amplifier consisting of a tapered chalcogenide fiber coupled to an Er 3+ -doped chalcogenide microsphere has been optimized via a particle swarm optimization (PSO) approach. More precisely, a dedicated three-dimensional numerical model, based on the coupled mode theory and solving the rate equations, has been integrated with the PSO procedure. The rate equations have included the main transitions among the erbium energy levels, the amplified spontaneous emission, and the most important secondary transitions pertaining to the ion-ion interactions. The PSO has allowed the optimal choice of the microsphere and fiber radius, taper angle, and fiber-microsphere gap in order to maximize the amplifier gain. The taper angle and the fiber-microsphere gap have been optimized to efficiently inject into the microsphere both the pump and the signal beams and to improve their spatial overlapping with the rare-earth-doped region. The employment of the PSO approach shows different attractive features, especially when many parameters have to be optimized. The numerical results demonstrate the effectiveness of the proposed approach for the design of amplifying systems. The PSO-based optimization approach has allowed the design of a microsphere-based amplifying system more efficient than a similar device designed by using a deterministic optimization method. In fact, the amplifier designed via the PSO exhibits a simulated gain G=33.7 dB , which is higher than the gain G=6.9 dB of the amplifier designed via the deterministic method.
Capillary Electrophoresis Doping (CED) technique is proposed for the new doping technique of the functional molecules into the hybrid materials. Organic-inorganic hybrid films or waveguides are fabricated on the cathode and the capillary tube bridge is made between the hybrid materials and the anode solution bath. The capillary and the anode bath are filled with the solution of the functional molecules and DC voltage is applied between cathode electrode and the anode one. The functional molecules (ions) move along the electric field, and their doping into the hybrid materials
can be attained by the control of the capillary position and the electric current through the circuit. In this study, siloxane based hybrid films and waveguides are prepared, and the doping of organic laser dyes, Rhodamine6G and Cresyl violet are demonstrated using SiO<sub>2</sub> glass capillaries. It is shown that CED technique has a great potential to fabricate the multifunctional optical devices in which various different functional chemicals are contained.
Optically-assisted magnetic recording (OAMR) can solve fundamental problems concerning thermal fluctuation and write capability in magnetic recording, and it is regarded as the key technology in achieving density exceeding 1 Tbit/in<sup>2</sup>. OAMR is classified into magnetic dominant recording and optical dominant recording, and differences with respect to the recording method and effect between them are described. Magnetic dominant recording was conducted on longitudinal synthetic ferrimagnetic media to prove the fundamental effectiveness. Both SNR and overwritability without thermal erasure were assured. A theoretical estimation in optical dominant recording suggests that OAMR enables 10 times density compared with conventional magnetic recording. Butted grating should provide good optical characteristics as the heating element for optical dominant recording, and it also has compatibility with the conventional magnetic head for integration.