Current situation and development trend of nonlinear optical crystal
Nonlinear optical crystal is one of the most important photoelectric information functional materials. It is an important material basis of photoelectron technology, especially laser technology. Its development degree is closely related to the development of laser technology.
The nonlinear optical crystal material can be used to transform the laser frequency and expand the wavelength of the laser. It is used to modulate the intensity and phase of the laser, realize holographic storage of the laser signal and eliminate the self pumped phase conjugation of the wavefront domain. So, nonlinear optical crystal is an important material of high technology and modern military technology, the developed countries will be the priority in the position of development, and as an important strategic measure in the development of high technology in their respective programs, give attention and support.
With laser technology from the last century in 60s so far, the nonlinear optical crystal has also been considerable development, starting from the initial quartz crystal, emerging lithium niobate (LiNbO3 - LN), potassium dihydrogen phosphate (KH2PO4 - KDP), two potassium deuterium phosphate (KD2PO4 - DKDP), lithium iodate (LiIO3 - LI), K titanyl phosphate (KTiOPO4 - KTP), barium metaborate (-BaB2O4 - BBO), three (LiB3O5 - LBO) lithium borate, potassium niobate (KNbO3 - KN) and boric acid (CSB3O5 - CBO), cesium cesium lithium borate (LiCSB6O10 - CLBO) and KBBF (KBe2BO3F2 - KBBF) of beryllium and sulfur Silver gallium (AgGaS2 AGS), arsenic and cadmium germanium (CdGeAs - CGA), Zinc Germanium phosphide (ZnGeP2 - ZGP) and nonlinear optical crystal, widely used in laser frequency, and frequency, difference frequency generation, optical parametric amplification, electro-optic modulation, electro-optic deflection etc.. A representative example is: using optical waveguide devices and modulation devices made by LN, has been widely used in optical communication; the use of commercial intracavity frequency doubling YAG laser with KTP crystal, the green light output up to hundreds of watts; using CBO and frequency YAG three laser, 355nm output has reached 17.7 kilowatts; YAG CLBO four laser the frequency doubling, 266nm UV output reached 42 kilowatts; deep ultraviolet laser with six KBBF direct frequency has been 177.3nm; optical parametric oscillator using KTP, BBO, LBO, the tuning range covers the visible to the 4.5m band, and realize single longitudinal mode operation.
In terms of the level of technology in the field of nonlinear optical crystals, devices and applications, developed countries, such as the United States and Britain, are leading the world. They have made important contributions from the initial principles, the exploration of new materials and the development of devices. In the production of nonlinear crystal materials, Japan, China and some other countries in the former Soviet Union, such as Russia, Ukraine and Lithuania, play an important role. Some countries in the US and Europe mainly focus on the manufacture of nonlinear crystal devices and devices. China occupies an important position in the field of nonlinear optical crystals.
The world status of China in this field
In terms of academic research and industrialization of nonlinear optical crystals, China has important influence on the world, especially in the research of nonlinear crystals in visible and ultraviolet band. The main achievements in the field of our country is a nonlinear crystal (1) magnesium doped LiNbO3 crystals were invented, by doping the LiNbO3 damage threshold increased more than two orders of magnitude, greatly expand the application of lithium niobate crystal; (2) found in the series in borate and developed UV nonlinear optical crystal is excellent BBO, LBO, CBO, KBBF and a series of performance, ushered in a new era of UV laser, the limit of human beings constantly to solid ultraviolet laser propulsion; (3) for the first time in the world by the solvent method, growth of large KTP crystals can be of practical application, and realize the industrialization, make KTP crystal widely used in the world, promoted the development of laser technology. (4) led to the research and experimental verification of periodic and quasi periodic poled artificial nonlinear optical crystal materials, and opened up a new field of nonlinear optical crystals.
The growth of technology in China a variety of nonlinear optical crystals in the international advanced level, all crystal growth methods abroad in China are almost all important nonlinear optical crystals have been grown, some important to meet the demand of domestic major crystal engineering, a group of high-tech crystal has become a commodity in the international reputation.
Two. Market demand analysis
Nonlinear optical crystal material is a fairly determined industry closely related to industries such as laser, photoelectron and optical communications, and is greatly influenced by the development and change of these industries. With the rapid development of information technology in the world at the end of last century and the wide adoption of optoelectronic technology, the market demand of optoelectronic functional crystals, especially nonlinear optical crystals, has increased dramatically.
In recent years, the worldwide sales of nonlinear optical crystals are over 400 million US dollars per year. The demand for traditional nonlinear crystals is increasing year by year, and the market growth rate will be around 1530% in the next few years.
Nonlinear optical elements have shown a trend of accelerated development in three fields, such as modulation switch and remote communication, information processing and entertainment.
The commercialization of nonlinear optical crystal is lithium niobate (LiNbO3) and potassium titanyl phosphate (KTP) and barium metaborate (BBO), three (LBO), lithium borate, potassium dihydrogen phosphate (KDP) two (DKDP) and deuterium phosphate, where LiNbO3 is the largest market of nonlinear optical crystals, optical communications and industrial the laser is two of the most important applications of it. With the continuous development of optical communication industry, LiNbO3 crystals applied to optical communication amplitude modulator not only occupy most of the market, but also increase market share every year.
In addition to optical communication, industrial lasers and electro-optic are important markets for applications of nonlinear optical crystals. In recent years, it has maintained 1520% annual market growth. Among them, BBO and KTP crystals are the fastest growing crystal varieties in recent years, and their market prospects are promising.
The field of medical solid lasers is another important market of nonlinear optical crystals. The main applications are KTP, KDP and BBO crystals. CLBO will also be widely applied. Due to the rapid development of the laser in the medical industry, the demand for nonlinear optical crystals, such as KTP, has also increased rapidly.
According to market research company BCC (Business Communications Company, Inc) the latest research report, 2005, nonlinear optical crystal size of the global market reached $856 million 100 thousand, is expected in the future will be 17.1% of the average annual growth rate of 2009 expanded to about $1 billion 656 million. The market share of LiNbO3 used for optical communication in 2005 was 24.5% for nonlinear optical crystal materials and 29.6% in 2009. KTP, KDP, DKDP, BBO, CLBO, LBO and other crystals used in laser and electro-optic fields accounted for 18.5% of the total market share of nonlinear optical crystals in 2005. The AAGR growth rate of KTP crystal is 5.4%, and the total AAGR of other crystals is 8%.
From the perspective of the whole nonlinear optical crystal materials, devices and equipment, the developed countries such as the United States and Japan are big industrial countries. They occupy a monopoly position in large-scale production of nonlinear optical crystals, such as LiNbO3. Small scale materials such as KTP, BBO, LBO and so on are mainly China and Lithuania. In the field of device manufacturing, the developed countries, such as the United States and Europe, have the decisive advantage because of the strong overall technical force and the good industrial base. The developed countries such as China and other developed countries can only provide the developed countries with crystal materials to earn a little profit.
Three. The trend of development
1. the development of the extrovert and shorter band of purple
Development of all solid state deep ultraviolet (200nm) coherent light source, is currently one of the research projects in the forefront of the international field of optoelectronics, this is because the UV laser has important applications in many high technology fields, such as the new generation of integrated circuit lithography requires all solid state ultraviolet coherent light source; photoelectron spectrum in urgent need of tunable solid-state deep ultraviolet coherent light source, the development promote deep ultraviolet spectroscopy, EDS will play a key role, and will open up a new research field of material science; the development of deep ultraviolet coherent light source will also greatly promote the laser precision machining the. Because there is no direct output of the laser crystal deep ultraviolet wavelength was developed to solve key problems of development and application of solid state deep ultraviolet laser focused on NLO crystal frequency ultraviolet band, the prospect of related industrial development and technological progress is very attractive.
2. improvement of the properties of existing nonlinear optical crystals and the development of new crystals
One of the most typical example is the LiNbO3 stoichiometric ratio (SLN), due to the structural integrity of the increase, compared with the congruent lithium niobate SLN (CLN) over the quality of the performance, if practical technology, will have a revolutionary change in optoelectronics, optical communications and other fields. BBO is a nonlinear optical crystal which is first used to obtain 266nm ultraviolet light from the four frequency doubling of the 1064nm laser output by Nd:YAG. It has been applied for several decades in the field of frequency conversion. However, when the power of the output 266nm laser exceeds 180 milliwatts, it will produce photorefractive damage and be damaged. In recent development of mature CLBO crystals, not only the crystal growth is easier than that of BBO, but also the single crystal grows larger than that of BBO, and it has not been damaged when the output of 266nm is 40 watts. In this field, CLBO has a tendency to replace BBO.
3. periodic polarization quasi phase matching technique (QPM) for nonlinear optical crystals
China is in the worlds leading level in the study of periodic and quasi periodic polarization phase matching. Because such quasi phase matching devices can give full play to the nonlinear optical properties of crystals, and a single crystal can perform functions of frequency doubling, frequency sum and parametric oscillation simultaneously. So these technologies have important applications in optical communication, laser display, air pollution detection, medicine and national defense. QPM materials and devices are showing great vitality. At present, PPLN, PPKTP and PPRTA are more important (PP is one of the quasi phase matching).
4. nonlinear optical crystal in infrared band
Compared with the nonlinear crystals in visible and ultraviolet band, the development of nonlinear crystals in the infrared band is slow. The main reason is that the optical damage threshold of the existing infrared nonlinear crystals is too low, which directly affects the actual use. Because of the important application prospect of infrared nonlinear optical crystals in the military field, this kind of crystal material has become a key development direction in the field of nonlinear optics.
5. a new type of photorefractive crystal material
The existing photorefractive materials such as LiNbO3, BaTiO3 and other optical information storage applications, its photorefractive response speed is not fast enough, the storage noise is relatively large, these two aspects of the performance can not be compared with the widely used electromagnetic storage technology. Therefore, it is necessary to find a new type of photorefractive crystal material with better performance or to further improve the existing photorefractive materials.
Four. Develop ideas and focus
China has made significant progress in the industrialization of nonlinear optical crystals. Some production lines have been established. Some crystal varieties have been commercialized, such as KTP, LBO, BBO, LN, LT and so on. The products not only meet domestic demand, but also export a lot.
However, there is a big gap between the current development of the industrialization process of Chinas nonlinear crystal and technology, has yet to meet the development of traditional industry and high technology requirements in the two aspects of quality and quantity; the overall research (application) development level of a particular level of industrialization and foreign countries is still a considerable gap, but also has not formed set the organic connection of the true meaning of the industrial system. The specific performance is:
1. the production equipment is backward, the control level is low, the output of the single machine is few, the product rate is low, and the product quality is not stable.
2. the industrial dispersion and small scale (some varieties such as LiNbO3, although the total output is large, but big but not strong, the product grade is low, the optical grade crystal is few, most is the piezoelectric grade).
3. varieties and specifications are not complete. The gap between components and developed countries is even greater, which is related to the deep level processing of crystals, such as polishing, coating and precision machining of components.
4. industrialization and engineering level is low. On the one hand, some excellent performance crystalline materials are still in laboratory research stage, which can not meet the needs of high technology development. On the other hand, the industrialization level of laboratory achievements transforming to productivity needs to be improved.
5. the industrialization promotion is weak, the resources are not used effectively, and the complete industrial chain and industrial system have not been established. The management system is fragmented, the investment intensity is low and dispersed, the development of raw materials and special instruments and equipment that are matched with crystal production is not balanced, and the application and development of products need to be strengthened. The disorderly competition between peers needs to be solved. There is no effective combination mechanism between production and application, and the promotion and application of new materials and new products are weak.
According to our countrys dominant position in the field of nonlinear crystal part, with international photoelectric crystal industry, especially the development trend of laser and nonlinear crystal industry and the world market as the direction, focus, play advantage, take the key breakthrough, crystal varieties concentrate on capturing a part of the national economy and national defense construction is of great significance. The value of nonlinear crystal in China reached 1 billion 500 million yuan in 2010, 2020 reached 3 billion yuan.
1. nonlinear optical crystals used in optical communication and integrated optics, including quasi phase matching (QPM) multi domain structure crystal materials and components;
2. the nonlinear optical crystal used by the red, green and blue three base light sources of laser TV.
3. semiconductor frequency doubling crystals (such as KN and some possible QPM products) applied to the next generation of optical disk blue light sources;