February 9, 1998 (TOKYO) -- Nichia Chemical Industries Ltd. and Matsushita Electric Industrial Co., Ltd. plan to begin sampling blue-violet lasers at the end of 1998.

The lasers are expected to be put into practical in the 21st century in post-VTR products.

A blue-violet laser has a 410nm wavelength, shorter than that of the prevailing red laser. It is a long-awaited product for consumer electronics manufacturers.

It allows a 2.5-times increase in data storage density of current digital video disks (DVDs) and will support new DVD media with a storage capacity of 15GB per side. The next-generation DVD products, which will offer high-quality video and long recordings, could potentially kick analog VTRs out of the market in one stroke.

Post-VTR Products to Debut in 2000

The development of blue-violet lasers will put next-generation DVD products on the market in 2000 or 2001. These products will be marketed at the culmination of emerging digital satellite broadcasting and terrestrial digital TV broadcasting.

Targeting the replacement of analog VTRs with the new products, makers will market rewritable DVDs at first. Sony Corp., for example, will put household disk recorders on the market toward 2000. The company is aiming for a DVD that can record video for more than three hours.

A storage capacity of 15GB is sufficient for recording a two-hour movie with a quality close to high-definition television (HDTV). It also offers 6 hours of recording with quality close to current TV sets. A long-duration recording mode, which decreases bit rates in real time, will enable the DVD media to record for about 20 hours.

The next-generation DVD products reportedly will be easy to use. Unlike current VTRs, rewinding is unnecessary, and playback can be started using a push button after confirming the list of contents through displayed icons.

Blue-Violet Laser and SHG Laser Compete

There are two kinds of technology to make blue-violet lasers. (See table.) Nichia Chemical is using a gallium-nitride (GaN) system to develop a blue-violet semiconductor laser, while Matsushita is urging a second harmonics generation (SHG) laser. SHG is a technology to halve the wavelength of an infrared laser using a wave guide device.

At this stage of development, both lasers cannot satisfy users' requirements perfectly as a light source for rewritable optical disk drives, so both companies need to improve their technology before sampling products at the end of 1998.

Technical bottlenecks that are equally challenging are an increase of laser output with increased ranges of operating temperatures and a stable supply of the products.

Since a semiconductor laser decreases its operating life as its operating temperatures or output increase, it is difficult to satisfy these conflicting needs at the same time. The maximum laser outputs confirmed at present are 2mW for Nichia's semiconductor laser and 10mW for Matsushita's SHG laser.

Both companies will complete lasers having an output ranging from 20mW to 30mW, which is sufficient to rewrite DVD media, according to the companies' officials.

Nichia Chemical will try further to enhance the quality of its GaN-system crystal and decrease its threshold current density from 1.5KA/cm³ to 1KA/cm³ to solve the problems. The company is confident about solving these problems because the materials of the GaN-system, unlike materials of a gallium-arsenide (GaAs) system, have a characteristic of suppressing the growth of crystal defects, which in turn is harmful to the operating life of a laser.

Matsushita said it has a prospect to solve its technical problems using an infrared semiconductor laser for its laser oscillation.

Costs of both products will not exceed 1,000 yen (US$8.10) at the time of mass production. The SHG laser requires a wave guide device, which implies that cost reduction is not easy. However, Matsushita intends to decrease the total cost of a pick-up by integrating various functions into the wave guide devices.

Still, several problems may remain because each of the blue-violet lasers will be supplied by a single maker. Other makers are far behind schedule in developing a blue laser. If an exclusive supply system continues, problems, such as lack of quantity assurance, tardy cost reduction efforts and lack of considerations for specific needs of DVD drive makers, will occur.

DVD Disk Shares Benefit of Development

Following the development of the blue-violet lasers, the development of new-generation DVDs with a storage capacity of 15GB is progressing. Companies, such as Sony, Pioneer Electronics Corp. and Matsushita, have started competing with technical proposals to firm up future standards for the next-generation DVDs.

To obtain a storage capacity of 15GB, the storage density of the next-generation DVDs must be about 3.2 times that of current DVDs. However, the replacement of the light source with the blue-violet laser improves only about 2.5 times. The remaining 30-40 percent must depend on the introduction of a new technology that can increase the storage density of the optical disks.

Compatibility with current CDs and DVDs also will be necessary. Part of the current write-once optical disks and double-layer disks cannot be read by blue-violet lasers. Technology to install blue-violet, near-infrared and red-light sources cost effectively may become necessary in the future.

Table: Comparison of the two blue-violet lasers Characteristics currently obtained and targeted by the end of 1998 are shown. yes: a sufficient characteristic as a light source of optical disk drives, no: a characteristic to be improved, cost: estimated cost at a stage of the full pervasion of the new generation DVDs. Nichia's blue-violet laser Matsushita's SHG laser Existing End of 1998 Existing End of 1998 Wavelength (nm) 410 410 425 425 Output (mW) no : 2 yes : 20 to 30 no : 10 yes : 20 to 30 Operating temperature (degree centigrade) no : unconfirmed yes : -10 to +60 no : 0 to +50 yes : -10 to +60 Volume (mm3) yes : 120 yes : 120 yes :117 yes : 117 Optical noise *1 no *3 yes *4 yes yes Aspect ratio yes : 4 yes : 4 yes : 2 yes : 1 Cost - yes *5 - yes *6 Supplier *2 no no no no