Cover Photograph: Over-100-bit Photonic Crystal Optical-RAM Chip

We are working on large-scale integration of optical-memory (o-RAM) by photonic crystal technology which can break through the limit of size and power consumption in conventional o-RAMs. Here we fabricated a 1.1-mm silicon photonic crystal chip in which over 100 nanocavities were integrated and realized successfully over-100-bit o-RAM operation with low power for the first time (See page 45).

Microscope image of 128 nanocavities integrated in a silicon chip. Lower: Schematic of multi-bit o-RAM action with wavelength division multiplexing.
Principal of o-RAM operation. A bistable memory that holds/switches “0” and “1” states is realized by fast carrier-plasma effect greatly enhanced in a high quality factor nanocavity.
Write and read-out operations of 4-bit random pulses in two different sets of sequential 4 o-RAMs (demonstrated in a similar integrated o-RAM chip in an InP-based photonic crystal).