GE's technology differs in subtle yet important ways that could broaden its appeal significantly. While both versions use lasers to record data, InPhase's technology encodes information using thousands of overlapping 3-D patterns known as pages, each containing 1.4 million bits. These pages are about one millimeter long and 0.8 millimeters wide, and a single disc can contain as many as 1.7 million pages. They are recorded through the whole depth of the media, and can coexist in the same physical space. The InPhase disc reader simply reads a specific page by viewing the disc from a different angle. However, this calls for sophisticated recording and reading optics.

In the GE version, each hologram measures 0.3 micrometers by 5 micrometers and represents a single bit of information. They are patterned across a disc in a way that resembles the patterns on the surface of a regular CD or DVD, and they're arrayed in a plane, with multiple planes layered throughout the body of the disc. The company's current prototypes have 21 layers, but Lawrence says that the goal is to achieve between 50 and 100 layers, or one terabyte of data storage.

The way that GE's holograms are arranged across a disc means that playback machines will be able to play older media, Lawrence adds: "Our technology uses formats similar to those in existing optical media but does it in the entire volume of the disc in many, many 'virtual layers'. These discs will be very similar to the DVD or Blu-ray discs but are much higher capacity."

GE is talking to several electronics companies about creating playback machines, and it wants the technology to fit well with existing disc-manufacturing techniques. While the InPhase version sandwiches its special optical recording media inside another type of plastic, the GE discs are made from a polycarbonate that can be processed with conventional manufacturing methods. The material can be melted, injected into a mold, and cooled to form a disc, the same way that today's optical media are made.

InPhase claims to be unconcerned about competition from GE, arguing that each company is targeting a different market segment. "I think that's a great design goal for GE," Rancis says. "But for our particular customer base, none of those people have material on DVDs. We are only doing high-end customers."