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Release: September 27, 2001

NGK Develops The World First SHG Element for High Power, High Performance Blue Lasers(for Reading and Writing of Next Generation Optical Disc Recorders)

NGK Insulators, Ltd. in collaboration with Matsushita Electric Industrial Co., Ltd. has succeeded in development of an SHG, Second Harmonic Generation element for high-power, high-performance blue lasers for the first time in the world. SHG blue lasers, which are mounted on optical heads to be used as laser sources for reading and writing, has potential to realize next generation large capacity optical disc recorders for high-definition images.

Features of the Product

  1. This newly developed SHG element has a ridge structure comprised of a 3 µm (µm= one millionth of a meter) optical waveguide (optical path) in the form of a ridge placed on a single crystal magnesium oxide doped lithium niobate (LN) substrate.
  2. The optical waveguide is processed with high precision on the order of submicrons, and the lithium ions within the LN single crystal are positioned in regular cycles (periodically domain-inverted structure).
  3. When the infrared laser beam passes through the optical waveguide, it is effectively transformed into a blue laser beam.

Performance of the Product

The blue laser incorporating this SHG element achieves a wavelength of 410nm (nm=one billionth of a meter) and an optical output power of 30mW, which is required for next generation large capacity optical disc recorders. (An optical output power of a conventional SHG laser is only 2 mW with a wavelength of 425nm.)

Points of Development

  1. NGK applied expertise in ultra-precision processing technology acquired through its development of optical fiber arrays and optical waveguide for optical communications systems, which were based on its ceramics and single crystal material technologies.
  2. NGK has developed an SHG element with both extraordinary accuracy and excellent reliability by taking advantage of the properties of LN single crystal material and applying its extensive experience in structural design, ultra-precision processing and accurate measurement technologies

Description of Terms

[Blue Laser]
  1. Data on an optical disc is read and written by narrowly focusing a laser beam through an objective lens. Using a laser with a short wavelength light source makes it possible to focus the laser beam more narrowly on the disc, which realizes a higher data recording density, which in turn results in a higher recording capacity for the optical disc.
  2. Current DVDs (recording capacity of 4.7 Gbyte) use red lasers with a wavelength of about 650nm for reading and writing. In contrast, blue lasers have a short wavelength of about 410nm, which allows for a dramatic increase in the data recording density.
  3. The blue lasers that are currently available are gallium nitride (GaN) based semiconductor lasers that directly emit a blue laser beam.
[SHG Laser]
  1. An infrared laser beam emitted from semiconductor laser is shortened to half in wavelength by passing through the optical waveguide in the SHG element. An infrared laser beam with a wavelength of 820 nm is transformed into a blue laser beam with a wavelength of 410 nm.
  2. The advantage of combining a long-life infrared semiconductor laser, whose output power is easy to increase, with an SHG element that can be readily mass-produced, is that it makes it possible to generate a low-noise laser beam.
A photo of SHG element

A photo of SHG element

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