  The significant advancements in integrated photonics have enabled high-speed
and energy efficient systems for various applications from data communications
and high-performance computing, to medical diagnosis, sensing and ranging.
However, data storage in these systems has been dominated by electronic
memories which necessitates signal conversion between optical and electrical as
well as analog and digital domains, and data movement between processor and
memory that reduce the speed and energy efficiency. To date, a scalable optical
memory with optical control has remained an open problem. Here we report an
integrated photonic set-reset latch as a fundamental optical static memory unit
based on universal optical logic gates. While the proposed memory is compatible
with different photonic platforms, its functionality is demonstrated on a
programmable silicon photonic chip as a proof of concept. Optical set, reset,
and complementary outputs, scalability to a large number of memory units via
the independent latch supply light, and compatibility with different photonic
platforms enable more efficient and lower latency optical processing systems.
