Blu-Ray (BD) a new generation of video, which supports a clear standard, HD video recording, without loss of image quality. The creation of this technology, and Sony to develop a blue violet semiconductor laser capable of providing the necessary density recording on optical disk. Blue violet laser used in light emitting DINARD equipment within the wavelength 400nm - 410nm. This allows the short wavelength of the data to be recorded and played in the high density. The main feature of the KD technology is its ability to store more data five times in the 12 cm optical disk system according to the red laser DVD.
What is a Semiconductor Laser?
Apart from semiconductor lasers, including solid-state laser based on ruby, glass and other materials, gas lasers, the helium, neon, argon and other gases, and pigment-based liquid laser semiconductor laser is relatively simple structures in comparison to other types. The laser emits light when an electric current to the pn junction of a compound semiconductor. Sony Semiconductor lasers began in 1984, with metal-organic chemical vapor deposition (MOCVD) method for growing crystals. This advance paved the way for the subsequent adoption of music CDs and MDs.
Figure 1 shows the structure of a blue-violet semiconductor lasers. Semiconductors are used in species after the manner in which electrons are given. An N-type semiconductor or excess electrons possess an abundance of electrons, while the P-type semiconductors or hole has a surplus of electron-hole to accept. LED light in the intersection where these two materials together with the cathode, with the P-type anode and the N-type.
A semiconductor laser must not only light but also to maintain a stable wavelength of light required for a particular purpose. This is achieved by sandwiching a MQW light-emitting layer between the P-and N-type semiconductor. In Sony's blue-violet laser, the cladding layer of P and N-type is made of aluminum gallium nitride (AlGaN). By optimizing the structure of the MQW light-emitting layer, Sony has been able to achieve excellent light emitting efficiency.
A key challenge for the development of a working blue-violet laser has been durability. A semiconductor laser produces heat when light, and this can be the materials and the lifetime of the device. Former semiconductor lasers had sapphire substrates, but the poor heat transfer performance of this material is little scope for improvement in the semiconductor life. Sony radically redesigned semiconductor industry and the substrate used gallium, the excellent thermal conductivity, instead of sapphire. By improving the efficiency with which laser heat is used by the semiconductor industry, Sony was able to dramatically improve the life span.
Laser Wavelengths (Colors) and Storage Densities
Density data storage on optical disk are the length of waves and the output of the laser beam. By reducing the wave length of laser radiation, the beam can be to a smaller place, and that the density of information.
The world's first semiconductor laser has a wave length of 840nm and vibrations generated infrared light. In 1975, Sony reach temperature continuous wave operation of algae with infrared laser wave length of 780nm. This device helped by the popularity of the music CD 650-700MB of data to 12 cm on a disk. In 1985, Sony has developed the first laser AlGalnP red, the room-temperature continuous wave operation at 650nm. If it is possible to make a film full time on a single DVD-12cm, with a capacity of 4.7 GB per layer.
With very short waves of 405 nm, blue-violet semiconductor laser was developed to even higher density than the host of the DVD. Through the development of semiconductor-blue-violet, Sony has the BD format, the 25 GB of memory in a single-layer disc and 50 GB on a dual-layer disc. This is sufficient for about two hours of HD video in 1920x1080i resolution.
The History of the Blue Laser
Initially the development of a blue or blue-violet laser was seen as an impossible task because of the difficulty of crystallizing the compound semiconductor needed to produce this light. Furthermore, a semiconductor capable of emitting blue or blue-violet light would need to be manufactured from elements at the high end of the periodic table. This was a major challenge. Elements at the high end of the periodic table are difficult to crystallize because of their strong bonding characteristics.
Sony's development efforts started with the raw materials. It began to explore the characteristics of the various elements, using a trial-and-error approach. In July 1993, it created the world's first ZnSe semiconductor laser capable of room-temperature continuous-wave operation, an achievement that was previously regarded as impossible. In February 1996, Sony succeeded in maintaining continuous oscillation of a ZnSe semiconductor for 100 hours. These successes brought the commercial development of a blue semiconductor laser within reach. Subsequently it was decided to use GaN, which produces a more stable blue-violet light. Sony had succeeded in developing a blue-violet semiconductor laser suitable for use in consumer electronic products, and in 2003 it launched the world's first BD recorder, the BDZ-S77.
Figure 2: Output Power-Current and Voltage-Current Properties of a 405nm AlGaInN Laser (a) and a 780nm AlGaAs Laser (b) During Room-temperature Continuous-wave Operation
There are differences in the voltage-current properties of a BD laser and CD-R laser. Because a BD laser has a shorter wavelength, the energy per photon is greater. This means that the drive voltage and power consumption are higher than for a CD-R laser.
Creating a Triple-Wavelength Laser
By using a triple-wavelength laser, it is possible to simplify the optical pickup in the optical systems. The advantages include a reduction in the number of parts required, and in the number of assembly and manufacturing processes involved. However, the lasers used in CDs, DVDs, and BDs are all made from different materials, and the development of a simple three-in-one device was thought to be impossible.
The impossible was made possible through technology used in PlayStation 2. Sony had already succeeded in developing a hybrid CD/DVD pickup for PlayStation 2 and was able to apply this technology to the creation of a triple-wavelength pickup. It did this by fabricating a substrate with a BD GaN laser chip and mounting a hybrid CD/DVD chip on top. The excellent thermal conductivity of the BD GaN substrate ensures efficient removal of heat generated by the hybrid CD/DVD chip.
PLAYSTATION 3 was designed to accommodate three totally different optical disc standards—CD, DVD and BD—in a single unit. As a game console that also functions as a next-generation HD player, PLAYSTATION 3 has taken the market by storm.
Figure 3: The Structure of the Triple Wavelength Laser
The Future of the Technology
The evolution of optical discs as media for the storage of video has advanced from the CD to the DVD, and now from the DVD to the BD. The development of semiconductor lasers has been a major factor in this evolution.
With the emergence of the blue-violet laser, the development of lasers with shorter wavelengths appears to have reached a plateau. A semiconductor laser with a wavelength shorter than the blue-violet laser would produce ultraviolet light, and in addition to the development of the semiconductor laser itself, it would also be necessary to develop optical components and recording media capable of withstanding exposure to ultraviolet light. Future development efforts are likely to focus on the development of blue-violet semiconductor lasers with improved output power, and on the creation of media with faster recording speeds and more layers
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