The format wars will continue but there is still hope exists for the traitional CD.
A research team at Harvard University has developed a technique that could help to significantly boost the capacity of conventional optical discs.They’ve fabricated a nano antenna–built directly onto an inexpensive, off-the-shelf laser–that focuses light to a much smaller spot size than is possible with even the best traditional lenses, potentially enabling more bits to be written onto an optical disc.
The storage capacity increases as the wavelength of the light used to write(burn) the data decreases, normal CDs are written using light of wavelength of about 780 nm(Nanometers).DVDs use 650 nanometers, and boht HD-DVDs and Blu-ray discs use 405 nanometers. Wavelengths shorter than 405 nanometers would require light sources far too expensive for consumer electronics.The problem is that conventional lenses can only focus light to half their wavelength, a physical barrier called the diffraction limit. The Harvard researchers sidestepped this limit, however, by abandoning traditional optics in favor of nano-optical techniques. “We can get around the wavelength limitation by using an antenna,” says Ken Crozier, assistant professor of electrical engineering at Harvard.
The team of Crozier, Federico Capasso, professor of applied physics at the university, and graduate students Eric Kort and Ertugrul Cubukcu designed the optical antenna to focus light from a commercial laser (with a wavelength of 830 nanometers) to a spot size of 40 nanometers. With this resolution, “you’d be able to pack more than three terabytes [3,000 gigabytes] worth of data onto something the size of a CD,” Crozier estimates. That’s enough to hold more than 300 feature-length movies. By comparison, a dual-layer HD-DVD or Blu-ray disc can hold 30 gigabytes or 50 gigabytes, respectively.
The antenna is consisting of two nano rods coated with Gold , which is separated by a gap of 30 nanometers.Still the technology is not ready for use in consumer electronic devices, They’re also exploring alternatives to the gold metal that currently coats their nano rods. Silver, for instance, could focus light more efficiently than gold at the wavelengths used by the consumer electronics industry.