Laser Boosts Blu-ray Disc Storage to 1TB

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Sony Corp. and Tohoku University have developed an ultrafast blue-violet (405 nm) semiconductor laser with high-intensity optical pulses capable of using two-photon absorption. The laser's 100-W output is more than 100 times higher than that of conventional blue-violet lasers, which are used in the creation of Blu-ray discs. Such discs made with the new laser could hold about 20 times more information, or about 1 TB of optical data. Currently, Blu-ray discs hold 25 GB of data, with dual-layer versions capable of storing 50 GB.

Beam emitted by the blue-violet ultrafast pulsed semiconductor laser. (Arrow is pointing to the semiconductor optical amplifier)

The all-semiconductor laser is capable of generating optical pulses in the ultrafast duration of 3 ps, with ultrahigh-output peak power of 100 W and repetition frequency of 1 GHz.

Although there have been ultrahigh-output laser devices combining solid-state lasers and a second-harmonic generation unit for high functionality and high-value leading-edge chemical research applications in the past, the light source box itself was bulky, and a specialist technician was required to ensure the stable operation of the laser. There are high expectations that this newly developed semiconductor laser system, which incorporates semiconductor diodes, can have a much wider range of future applications. For instance, this technology enables the size of components such as the light source box to be drastically reduced.

The newly developed blue-violet semiconductor laser (r) and the newly developed semiconductor optical amplifier.

This newly developed light source is capable of using the nonlinear optical process two-photon absorption, which occurs only as a result of high-intensity optical pulses. When light from the laser beam is concentrated on the lens, it creates chemical and thermal changes in the vicinity of the lens focus spot, which is narrower than even the diameter of the focus spot of the lens itself. It is anticipated that application of these properties will be possible in a wide range of fields, such as 3-D nanofabrication of inorganic/organic materials in the order of nanometers, and next-generation large-capacity optical disc storage.

Sony tested the principles for applying this technology in next-generation large-capacity optical disc storage by creating void marks with a diameter of approximately 300 nm at intervals of 3 µm on the interior of plastic material and successfully read these marks with the laser beam.

These experimental results have been achieved through integration of Tohoku University’s fundamental technology on ultrashort-pulse lasers (Tohoku University is promoting a joint research program for industry-academic collaboration based on materials and devices) and Sony’s fundamental technology on semiconductor laser diodes.

Tohoku University and Sony will continue to work together to further develop the fundamental technology for even higher output and multifunctionality, while developing practical applications and making these systems even more stable and compact.

These research findings were published in the journal Applied Physics Letters.

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Published: July 2010
1TB capacityall-semiconductor laser picosecond pulse sourceAsia-PacificBlue-RayBlue-Violet LaserJapanLaser Beamlensesnano-fabricationoptical disc storageoptical pulsesOpticsResearch & Technologysecond harmonic generationsemiconductor diodessemiconductor laserssolid-state lasersSony Tohoku Universitythermal changestwo-photon absorbtionultrashort pulsed lasersLasers

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