Memory needs of digital processing and computing has been
formed so far around the idiosyncrasy of electronic RAM. Between
types of electronic memories, static RAMs have been
the preferred choice for performance-sensitive applications, implementing
cache memories on the processor chips of HPCS.
Multiple single static RAM cells arranged in rows and columns
form what is widely known as a RAM bank structure. A typical
two dimensional (2D) arrangement of 4 4 static RAM
bank is shown in Fig. 1(a), where 16 separate single RAM cells
are independently controlled and each row can store a 4-bit
word. Shared among the RAM cells of a single row, the “Word”
signal grants simultaneous access for Read or Write operation
according to the logical value of the corresponding signal.
The most basic element in electronic RAM bank structures
for static memory design has been the 6-transistor (6T) RAM
cell [6], the layout of which is shown in Fig. 1(b). It consists
of two pass gates for access control and two cross-coupled inverters
with two possible states. Although it has been widely
used in electronic cache memories, its speed performance imposes
the major limit to the overall system processing speed.
To overcome the long foreseen “Memory Wall”, research
has shifted focus on developing all optical RAM alternatives
based on ultra-fast bistable latching and memory elements.
Optical Set-Reset (SR) Flip-Flop (FF) operation has already
been reported, often based on two coupled ring lasers in a
master–slave configuration [7] or the bistability between the
clockwise and counterclockwise lasing direction of a microdisk
laser [8]. An All Optical Flip-Flop (AOFF) employing two coupled
SOA-XGM switches that avoids the long time constants to
settle lasing operation was also presented in [9]. Other FF implementations
are based on two Mach Zehnder Interferometers
in a master-slave configuration [10] or in a packaged and hybrid
integrated form [11]. The adjustment of the lasing threshold in