Magneto-Optical storage using solid immersion lenses (Left) allows focusing of the laser beam on a much smaller area, allowing much higher data densities.
Patterned Media (Right), a surface with billions of small hills on which bits would be recorded. This is done to isolate the magnetic fields from one another, preventing interference from the magnetic patterns of other bits. While current storage technologies require 500 to 1000 grains for each bit, a patterned media disk may only require seven to eight grains per bit. This could allow up to ten terabits per square inch. However the technology does not exist to create media with small enough hills, they need to be eight nanometers but the current lithographic process can only produce them 80 nanometers.
Holographic crystal allows data storage in three dimensions, holograms record not only light but also it's direction. Because holograms are created using a reference beam to generate an image, several different data records can be stored in the same location using a slightly different reference beam. This should give a very high storage to area ratio of 1 terabyte per cubic cm.
Data Storage is an interesting area of computing which often yields the most breathtaking changes, it continues to improve with no sign of slowing down, just imagine the data storage technology in 10 years.
Punch Cards and Valves
The Hard Disk Drive
The Floppy Disk
The Compact Disk