Product Code Database
A blue laser emits electromagnetic radiation with a wavelength between 400 and 500 , which the human eye sees in the visible spectrum as blue or violet.
Blue lasers can be produced by:
Lasers emitting wavelengths below 445 nm appear violet, but are nonetheless also called blue lasers. Violet light's 405 nm short wavelength, on the visible spectrum, causes fluorescence in some chemicals, like radiation in the ultraviolet ("black light") spectrum (wavelengths less than 400 nm).
In the 1960s, advancements in sapphire creation allowed researchers to deposit GaN on a sapphire base to create blue lasers, but a lattice mismatch between the structures of gallium nitride and sapphire created many defects or , leading to short lifetimes (<10 hours) and low efficiency (<1%).
Additionally, gallium nitride (GaN) crystal layer construction proved difficult to manufacture as the material requires high nitrogen gas pressures and temperatures, similar to the environment for creating synthetic diamonds.
In 1992, Japanese inventor Shuji Nakamura, while working at Nichia Chemicals, invented the first blue semiconductor LED using an InGaN active region, GaN optical guide and AlGaN cladding, and four years later, the first low-power blue laser; eventually receiving the Millennium Technology Prize awarded in 2006, and a Nobel Prize for Physics along with Professor Isamu Akasaki, and Hiroshi Amano NobelPrize.org Press Release (7 October 2014): The Royal Swedish Academy of Sciences has decided to award the Nobel Prize in Physics for 2014 to Isamu Akasaki (Meijo University, Nagoya, Japan and Nagoya University, Japan), Hiroshi Amano (Nagoya University, Japan) and Shuji Nakamura (University of California, Santa Barbara, CA, USA) "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources" in 2014 for this invention. Shuji Nakamura wins the 2006 Millennium Technology Prize. Gizmag.com (2006-05-17). Retrieved on 2010-10-26. The gain medium defects still remained too high (106–1010 defects/cm2) resulting in a low-power laser with a short, < 300 hour lifetime using Pulsed laser.
In the late 1990s, Dr. Sylwester Porowski, at the Institute of High Pressure Physics at the Polish Academy of Sciences in Warsaw (Poland), developed technology to create gallium nitride mono-crystals with high structural quality using magnesium doping to create fewer than 100 defects/cm2 — at least 10,000 times better than prior attempts. In 1999, Nakamura used Polish-produced GaN crystals, creating lasers with twice the yield and ten times the lifetime of his original designs; 3,000 hours at 30 mW.
In the 2000s, Japanese manufacturers mastered the production of a blue laser with 60 mW of power and long lifetimes, making them applicable for devices that read a dense (due to blue's short wavelength) high-speed stream of data from Blu-ray, BD-R, and BD-RE. Semiconductor lasers enabled the development of small, convenient and low-priced blue, violet, and ultraviolet (UV) lasers, which were previously not available, opening the door for many applications.
Today, blue semiconductor lasers either use a sapphire substrate (primarily used by Nichia, which uses a contract manufacturer: Sony), or a GaN mono-crystal substrate (primarily used by TopGaN), both covered with layers of gallium nitride. The GaN optical guide layer of the Nichia devices is formed from active region InGaN or spontaneously via self-assembly.
Polish technology is considered less expensive than the Japanese, but has a smaller share of the market. Another Polish company creates GaN crystals for use in blue diodes – Ammono, but does not produce blue lasers.
Blue, direct diode lasers can also be fabricated with InGaN semiconductors (445 nm through 465 nm). The InGaN devices are perceived as significantly brighter than GaN (405) nm direct diode lasers, since the longer wavelengths are closer to the peak sensitivity of the human eye.
Use of phosphorescent direct diode blue OLED for lasers is impractical, due to poor lifetimes(<200hrs).
Zener diodes can be incorporated into the circuitry to minimize ESD failures.
Semiconductor lasers can be either driven by pulses or continuous wave operation.
Violet DPSS laser pointers (120 mW at 405 nm) use a direct diode infrared gallium arsenide (1 W @ 808 nm) lasers being directly doubled, without a longer-wave diode-pumped solid state laser interposed between diode laser and doubler-crystal results in higher-power.
Blue DPSS laser pointers, initial availability around 2006, have the same basic construction as DPSS green lasers. They most commonly emit light at 473 nm, which is produced by frequency doubling of 946 nm laser radiation from a diode-pumped or crystal. Neodymium-doped crystals usually produce a principal wavelength of 1064 nm, but with the proper reflective coating mirrors can be also made to lase at other non-principal neodymium wavelengths, such as the 946 nm transition used in blue-laser applications. For high output power BBO crystals are used as frequency doublers; for lower powers, KTP is used. Output powers available are up to 5000 mW. Conversion efficiency for producing 473 nm laser radiation is low with some of the best lab produced results coming in at 10–15% efficient at converting 946 nm laser radiation to 473 nm laser radiation. Due to low conversion efficiency, use of a 1000 mW IR diode results in at most 150 mW of visible blue DPSS laser light, but more practically 120mW.
For display applications which must appear "true blue", a wavelength of 445–450 nm is required. With advances in volume production, 445 nm InGaN laser diodes have dropped in price, becoming an optimal solution for laser phosphor projectors.
|
|
