Analysis of blue-violet semiconductor laser

A blue-violet semiconductor laser refers to a semiconductor laser with an oscillation wavelength of about 410 nm. In addition to being used as a light source for Blu-ray discs and the like, it is also expected to be used as an illumination light source, a display light source, and the like. Blu-ray discs use varieties with an oscillation wavelength of 405 nm. The blue-violet semiconductor laser is the basic component of the new generation of optical discs after DVD. Since the late 1990s, manufacturers, universities and research institutions have launched fierce competition for development.

4-layer Blu-ray Disc enables 12x recording speed

Like blue LEDs, blue-violet semiconductor lasers generally use GaN-based semiconductor materials. A GaN-based semiconductor crystal layer is stacked on a GaN substrate. There is also a method of utilizing SHG (Second Harmonic Generation) technology without using GaN-based semiconductors. SHG lasers use optical waveguide type elements to convert the light output from infrared semiconductor lasers into 1/2 wavelength light. For example, using an infrared semiconductor laser of 850 nm, a blue-violet laser of about 425 nm can be obtained. Using a semiconductor laser with a pulse output of 450mW, 12x speed recording can be achieved on a 4-layer Blu-ray disc. It is expected that Blu-ray Discs will continue to increase in capacity through multi-layered discs in the future. At that time, semiconductor lasers with output powers as high as 900 mW, etc., will be required.

Can be used for white light sources

The blue-violet semiconductor laser can change the oscillation wavelength by changing the layer structure of its GaN-based semiconductor layer. For example, a blue semiconductor laser can be obtained by extending the oscillation wavelength by a certain amount. Blue semiconductor lasers can be used as light sources for laser projectors in the field of displays. In addition to the direct use of blue semiconductor lasers for blue light sources, blue semiconductor lasers and optical fibers can also be used in combination. In the combined optical fiber technology developed by optical glass, the core material in the optical fiber can convert the wavelength of blue light, so that it resonates in the optical fiber to generate green light and red light, forming the three primary colors of light. When a blue-violet semiconductor laser is used for illumination, a white light source can be obtained in combination with a phosphor. For example, the white light source developed by Nichia is a combination of a blue-violet or blue semiconductor laser and an optical fiber, and the light emitted by the laser is extracted to the outside through the optical fiber. The part where the optical fiber exits is coated with a phosphor material for color mixing to obtain white light.

Among GaN-based semiconductor lasers including blue-violet semiconductor lasers, the development of green semiconductor lasers is currently attracting the most attention. Ultra-small projectors called "micro-projectors" have strong demand for green semiconductor lasers. There are still several issues for the smooth popularization of pico projectors in the future. Among the three technical issues of miniaturization, low power consumption and cost reduction, the killer of miniaturization is the laser light source. Compared with the current mainstream LED, the light emitted by the laser light source is not easy to diffuse, and it is easy to further reduce the size of the optical system. However, to use a laser light source, the efficiency is low compared with red and blue, and the high-priced green laser is the bottleneck. At present, since green semiconductor lasers that can be directly oscillated have not yet been commercialized, SHG elements have to be used to convert the wavelength of infrared laser light, which has become an obstacle to miniaturization and low power consumption.