Femtosecond lasers create 3D midair plasma displays you can touch (2015)

State of the Technology / “What Happened?”

• Original work is from 2015; multiple commenters note the absence of follow‑up or products.
• Consensus leaning toward “went nowhere” for consumer use, largely due to cost, complexity, and safety.
• Some speculate the technology may continue in military or classified contexts, citing later patents and related weapon research.

Cost, Size, and Engineering Constraints

• Femtosecond lasers used in labs and medicine are described as very expensive (hundreds of thousands of dollars) and physically large, often filling optical benches.
• Systems need complex optics (prisms, diffraction gratings, pulse stretching/compression), not just a simple compact “projector.”
• Practical, cheap, solid‑state versions are imagined but not known to exist in the thread.
• Beam scanning requires galvos and dynamic focusing; maintaining enough intensity for air breakdown at distance is described as technically hard.

Safety and Health Concerns

• Core issue: the device creates actual plasma in air. It can burn skin and potentially damage eyes; videos show visible fingertip burns.
• Commenters compare risk to fireworks more than to conventional displays.
• Eye safety is a major worry: powerful, unconfined IR lasers that can ionize air are seen as unacceptable for public or consumer spaces.
• Discussion branches into real-world experiences of laser- and light-induced retinal damage and the difficulty of noticing it early.

Noise, Ozone, and Byproducts

• Measurements cited around ~77 dB at very close range; considered tolerable but unpleasant, with noise scaling with brightness/resolution.
• Some wonder about use as a sound source.
• Concerns raised about ozone and NOx generation in air plasmas; exact levels remain unclear.

Military and Weaponization Angle

• Related research includes plasma-based decoys, area-denial concepts, “set to stun” nonlethal weapons, and “screaming balls of plasma” for psychological operations.
• Several commenters suggest this risk/benefit profile makes more sense for defense than for displays.

Comparison to Other Exotic Display Tech

• Thread recalls past “holographic” or volumetric systems (water-vapor projection, field emission displays, transflective LCDs, lenticular 3D, commercial volumetric units like Voxon).
• Pattern noted: many visually striking demo technologies fail to become practical, especially when 2D displays already serve most needs safely and cheaply.