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This paper reviews our recent activities on nanophotonics based on a photonic crystal (PC)/quantum dot (QD)-combined structure for an all-optical device and a metal/semiconductor composite structure using surface plasmon (SP) and negative refractive index material (NIM). The former structure contributes to an ultrafast signal processing component by virtue of new PC design and QD selective-area-growth...
Nano-photonic structures/materials such as surface plasmon and negative-index material as well as quantum dots (QD) and photonic crystals (PCs) are discussed from potentials for new photonic devices and technologies. PC slab waveguides and QDs were developed for key photonic devices such as ultra-small and ultrafast symmetrical Mach-Zehnder (SMZ)-type all-optical switch (PC-SMZ) and an optical flip-flop...
A photonic crystal (PC)-based symmetric Mach-Zehnder type all-optical switch (PC-SMZ), previously operated by single pump pulse alone, has been operated newly by a multiple-pump pulse train corresponding to a repetition frequency of 40 GHz at pulse energy as low as 10 fJ. The device involves quantum dots (QDs) in two parallel PC arms as optical nonlinear media and functions as a time-differential...
A photonic crystal- and quantum dot-based all-optical flip-flop switch (PC-FF) capable of synchronizing with high frequency clock was fabricated for a future optical digital signal processing device with high-speed capability of 40 Gb/s and beyond. Nanostructures constructing the PC-FF exhibit excellent characteristics and suggest successful optical FF demonstration.
The phase shift of signal pulse due to carrier excitation in quantum dots (QDs) induced by repetition control pulses is measured by two-color pump/probe measurements to investigate the effects of repetition frequency on the switch operation.The result suggests the possibility of beyond 40 GHz repetitive switch operations in photonic-crystal-based Mach-Zehnder (PC-SMZ) by using QDs with faster decay...
Topology optimization method has been applied to design the waveguide bends in the air-bridge type two-dimensional photonic crystal slab. We demonstrated that the optimized bends show good performance, comparable to the straight waveguide.
A metal-mask (MM) method for selective-area-growth (SAG) of self-assembled InAs quantum dots (QDs) on a GaAs substrate was developed for applications of ultra-small and ultra-fast all optical devices based on a combination of QD and photonic crystal waveguides (PC-WGs). Successful SAG of QDs with high density and high optical quality comparable to conventional InAs-QDs grown without the MM was confirmed...
Numerical and experimental studies on the photonic crystal waveguide intersection based on the topology optimization design method are reported and the effectiveness is shown by achieving high transmission spectra with low crosstalk for the straightforward beam-propagation line.
A two-dimensional photonic crystal (2DPC) slab waveguide-based symmetric Mach-Zehnder type all-optical switch (PC-SMZ) is promising for a future ultra-fast photonic network system. An ultra-fast (~ps) and ultra-low energy (~100 fJ) switching has already been demonstrated as the 1st phase. The 2nd phase is to create a PC-SMZ-based ultra-fast photonic logical switch with a latch function for an ultra-fast...
One of the exciting features of photonic crystals is that light may travel at very low group velocities at specific optical frequencies. In photonic crystal waveguides, such low group velocities are also possible. We have studied the propagation of femtosecond pulses in these waveguides, with a phase-sensitive and time-resolved near-field microscope. With this microscope, we visualized the pulses...
We have studied the dispersion of femtosecond pulses in a photonic crystal waveguide. We found that slow propagating pulses were asymmetrically broadened, due to higher order dispersion. With decreasing group velocity, the asymmetry increased.
Simulation, fabrication, characterization of two-dimensional photonic crystals and fabrication of nanoprobe-assisted site-controlled quantum dots for large optical non-linearity are presented for photonic crystal and quantum dot-based ultra-small and ultra-fast all optical switches
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