Photonic Crystal and Quantum Dot Technologies for Ultra-small and Ultra-fast All-optical Flip-flop

Nano-photonic technologies of GaAs-based two-dimensional photonic crystal (2DPC) slab waveguides and InAs quantum dots (QDs) are reviewed for symmetric Mach-Zehnder type, ultra-small and ultra-fast all-optical switch (PC-SMZ) and optical flip-flop device (PC-FF). In the 1st phase of this work, ultra-fast (~ps) and ultra-low energy (~100 fJ) switching has been demonstrated using the PC-SMZ chip with 600 μm × 300 μm in size. In the 2nd phase, the concept of the PC-FF based on the dual PC-SMZs for providing a latch function has been proposed for a future ultra-fast optical digital processor. One of the priority subjects is to establish a new design method, i.e., topology optimization method of the 2DPC waveguide with wide/flat bandwidth, high transmittance and low reflectivity. Another one is to develop a selective-area-MBE growth technique with a metal-mask method for high-density and highly uniform InAs QDs with different absorption wavelengths in different areas.