Optical Phased Arrays

Cloaking/Weapon technologies

Optical Phased Arrays are cloaking/weapons technologies relying on phased optics operating (in baseline optical) EM range to achieve various effects. OPA's can generate lasers on macroscopic scales or hide an object in a given spectrum of EM (omnidirectional cloak). OPAs are part of the Phased Array technologies. 
OPAs are layers of electrical oscillators and antennas placed on an surface in a distance comparable to the mimicked EM's wavelength. Through calculated firing patterns and timings, OPAs can mimic point like light sources that appear to be behind or in front of the OPA layer for an outer observer (by mimicking the divergence of said pointlike source through interference patterns). However, damaged or non-short distance oscillators can cause visual "glitches" around damaged areas or the edges.
Weapon OPAs instead focus convergent beams of EM, and thus can act as great yield weapons (dependent on individual oscillator distances and area of the mesh).
OPAs are extensively used from megastructures to miniature drones, making it one of the technologies that are used in all areas of life and in all sizes. It should be noted however that cloaking OPAs require computation, and thus, two types are known of it.
Bicameral OPAs use an off-site computation hub or a central, similarly cloaked unit to carry out computations and collect telemetry which keeps them updated. These OPAs can have a very small size and can conserve their thermal profile, but are subject to jamming and signal detection.
Traditional OPAs rely on-on site computation, and thus, rely on no outer signal. However, these OPAs have a minimum size for obvious reasons and can lose their thermal profile.
Weapon-OPAs are for instance found on the surface of megastructures, capable of acting as mid-to-high yield Dyson-weapons or as a simple radiative area. Smaller, specialised ones are found on interstellar warships, usually used as point defence and ionising lasers to feed an Entanglement Drive for instance.
OPAs need to be EMP shielded, which might limit their potential. Most OPAs lack significant shielding for obvious reasons and thus are not usable in high-B field environments for instance.

Utility

OPAs can and often are used to create 3d omnidirectional holograms, although AR implants or visCortex biohacks offer a far cleaner image and cheaper alternative.
OPAs are also used in some omnigeneral manufacturing methods as laser sources.
Transcendental OPAs had been at least once used to hide stars destroyed by Transcendental starkillers.

"The transhuman drops his OPA cloaks, and jumps as its armour turns into a New Sun, focused on the drones ahead. Weapon ports turn and point defence fires, but not even subminds can defy Newton and the transhuman lives for another few hours before the Heavens screams in EM and the crust melts."

Access & Availability

OPAs higly range in quality and power output, and from nearbaseline realms to Transcendents everyone uses them, albeit cloaking is usually achieved in space via metamaterials instead.

Complexity

OPAs are not as complex as other cloaking tech, but even primitive ones require understanding of ideal and phased array optics, photonics, nanotech manufacturing and a sufficiently advanced computing hardware to manufacture.
Transcendental OPAs seem to rely on sub-atomic EM generation methods and are only apparently understood by submind-deities.

Discovery

Working, mid-wavelength OPAs were made as early as in the 2010s, albeit these were flat and limited in wavelength and oscillator pacing.
NAS, NEU, NR and MSI aircraft carriers were equipped by microwave-to-red arrays by the time of the East War, albeit were only used once (on the Indian Front).
NAS and EMU entertainment system use OPAs as low-resolution holograms by the 2050s.
Full OPA cloaking in baseline range (both EM and Rayleigh limit) is achieved in the late 2070's and is used by the AU in the 2080's.