Nonlinear optical crystal is one of the important functional materials of photoelectric information. It is an important material basis for optoelectronic technology, especially laser technology. Its development degree is closely related to the development of laser technology.
The nonlinear optical crystal material can be used for laser frequency conversion, expanding the wavelength of the laser; for modulating the intensity and phase of the laser; realizing the holographic storage of the laser signal, eliminating the self-pumping phase conjugate of the wavefront domain change, and the like. Therefore, nonlinear optical crystals are indispensable key materials in high-tech and modern military technology. All developed countries have placed them in a priority development position and listed them as an important strategic measure in their respective high-tech development plans. Give high priority and support.
With the development of laser technology since the 1960s, nonlinear optical crystals have also been greatly developed. From the initial quartz frequency doubling crystals, lithium niobate (LiNbO3-LN) and potassium dihydrogen phosphate (KH2PO4) have emerged. —KDP), potassium dipotassium phosphate (KD2PO4—DKDP), lithium iodate (LiIO3-LI), potassium titanyl phosphate (KTiOPO4-KTP), barium metaborate (-BaB2O4-BBO), lithium triborate (LiB3O5—LBO ), potassium citrate (KNbO3-KN), bismuth borate (CSB3O5-CBO), lithium lanthanum borate (LiCSB6O10-CLBO), potassium fluoroborate bismuth (KBe2BO3F2-KBBF), and silver-silver gallium (AgGaS2-AGS), arsenic cadmium telluride Nonlinear optical crystals such as (CdGeAs-CGA) and bismuth zinc (ZnGeP2-ZGP) are widely used in laser frequency doubling, sum frequency, difference frequency, optical parametric amplification, electro-optic modulation, and electro-optical deflection. A more representative example is: optical waveguide devices and modulation devices made with LN have been widely used in optical communication; commercial intracavity frequency-doubled YAG lasers using KTP crystals have a green light output of several hundred watts; with CBO and Frequency YAG triple frequency laser, 355nm output has reached 17.7 watts; with CLBO quadruple frequency YAG laser, 266nm ultraviolet light output has reached 42 watts; with KBBF direct six times frequency has obtained 177.3nm deep ultraviolet laser; use KTP , BBO, LBO optical parametric oscillator, the tuning range covers visible light to 4.5m band, and achieve single longitudinal mode operation.
In terms of the level of science and technology in the field of nonlinear optical crystals, devices and applications, developed countries such as the United States and the United Kingdom are among the best in 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, some countries in Japan, China, and the former Soviet Union, such as Russia, Ukraine, and Lithuania, occupy an important position, while some countries in the United States and Europe focus on the manufacture of nonlinear crystal devices and devices. . China occupies an important position in the field of nonlinear optical crystals.
I. China's World Position in the Field China has an important international influence in the academic research and industrialization of nonlinear optical crystals, especially in the field of visible and ultraviolet nonlinear crystals. , attracted the attention of the world. China's main achievements in the field of nonlinear crystals are (1) the invention of magnesium-doped LiNbO3 crystals, which has increased the damage threshold of LiNbO3 by more than two orders of magnitude by doping, which has greatly expanded the application field of lithium niobate crystals; In the borate series, a series of excellent UV nonlinear optical crystals such as BBO, LBO, CBO and KBBF have been discovered and developed, which has created a new era of ultraviolet laser frequency doubling, which has enabled humans to continuously push the limit of solid ultraviolet laser. (3) For the first time, the practical application of KTP large single crystals by solvent method has been carried out internationally, and industrialization has been realized, which has made KTP crystals widely used throughout the world and promoted the development of laser technology. (4) Leading the research and experimental verification of periodic and quasi-periodic polarization artificial microstructure nonlinear optical crystal materials, and opened up a new field of nonlinear optical crystals.
The growth technology of various nonlinear optical crystals in China is at the international advanced level. All the existing crystal growth methods in foreign countries are available in China. Almost all important nonlinear optical crystals have been grown, and some important crystals have met the major domestic engineering needs. A group of high-tech crystals have become commodities and enjoy high reputation in the world.
Second, the market demand analysis Nonlinear optical crystal material is a fairly certain industry closely related to the laser, optoelectronics, optical communications and other industries, greatly affected by the development and changes of these industries. With the rapid development of the world's informatization wave and the widespread adoption of optoelectronic technology at the end of the last century, the market demand for optoelectronic functional crystals, especially nonlinear optical crystals, has increased dramatically at home and abroad.
In recent years, the sales of nonlinear optical crystals worldwide have exceeded 400 million US dollars per year. The demand for traditional nonlinear crystals is still increasing year by year. In the next few years, the market growth rate is around 1530%.
Nonlinear optical components have shown accelerated development in three areas: modulation switches and telecommunications, information processing and entertainment.
The main commercial nonlinear optical crystals are lithium niobate (LiNbO3), potassium titanyl phosphate (KTP), barium metaborate (BBO), lithium triborate (LBO), potassium dihydrogen phosphate (KDP), diphosphoric acid Potassium (DKDP), etc., of which LiNbO3 is the largest nonlinear optical crystal in the market, optical communication and industrial laser are its two most important applications. The continuous development of the optical communication industry has made LiNbO3 crystals used in optical communication modulators not only occupy the vast majority of the market, but also the market share is growing every year.
In addition to optical communication, industrial laser and electro-optic are important markets for nonlinear optical crystal applications. In recent years, it has maintained a market growth of 1520% per year. Among them, BBO and KTP crystals are the fastest growing crystal varieties in the field in recent years. Prospects are promising.
The field of medical solid-state lasers is another important market for nonlinear optical crystals. The main applications are KTP, KDP and BBO crystals. CLBO will also be widely used. Due to the rapid development of lasers in the medical industry, the demand for nonlinear optical crystals such as KTP has also increased rapidly.
According to the latest report from the research firm BCC (Business Communications Company, Inc.), the global market for nonlinear optical crystals reached US$ 851.61 million in 2005. It is expected to expand to an annual average growth rate of 17.1% in 2009. About $1.656 billion. Among them, LiNbO3 for optical communication accounted for 24.5% of the market share of nonlinear optical crystal materials in 2005, and is expected to be 29.6% in 2009. Crystals such as KTP, KDP, DKDP, BBO, CLBO, and LBO used in the laser and electro-optical fields accounted for 18.5% of the market for nonlinear optical crystal materials in 2005, and the AAGR (annual average growth rate) for KTP crystals was 5.4%. The AAGR of other crystals is 8% in total.
From the perspective of the entire nonlinear optical crystal material, device and complete machine equipment, the developed countries such as the United States and Japan are industrial powers, and monopolize the large-scale production of nonlinear optical crystals such as LiNbO3. Small-scale materials such as KTP, BBO, LBO, etc., mainly dominated by China and Lithuania. In terms of device manufacturing, due to the strong technical strength and good industrial base, developed countries such as the United States and Europe occupy a decisive dominant position. Developed countries such as China can only provide crystal materials to developed countries and earn a small profit.
Third, the development trend
1) Development of ultraviolet to shorter wavelengths The development of all-solid-state deep ultraviolet (200 nm) coherent light sources is one of the most advanced research projects in the field of optoelectronics in the world. This is because UV lasers have important applications in many high-tech fields, such as A new generation of integrated circuit lithography requires an all-solid-state UV coherent light source; in photoelectron spectroscopy and spectroscopy, there is an urgent need for a tunable all-solid-state deep-UV coherent light source, which will drive the development of deep ultraviolet spectroscopy and spectrometers. To a critical role, and will open up a new field of material science research; deep ultraviolet coherent light source will also greatly promote the development of laser precision machinery processing industry. Since there is no laser crystal directly outputting deep ultraviolet wavelength, the key problem of solving solid-state deep ultraviolet laser light source is concentrated on the development and application development of NLO frequency conversion crystal in the ultraviolet band. The prospect of driving related industrial development and technological progress is very attractive. Human.
2) Improvement of the performance of existing nonlinear optical crystals and development of new crystals A typical example is the stoichiometric ratio of LiNbO3 (abbreviated as SLN). Due to the improved structural integrity, SLN is more common than conventional molten lithium niobate (CLN for short). There is a qualitative leap in performance. If the practical technology is solved, revolutionary changes will be made in the fields of optoelectronics and optical communication. - BBO is a nonlinear optical crystal that is first used to quadruple the 1064 nm laser output from Nd:YAG to obtain 266 nm ultraviolet light. It has been used for decades in this field of frequency conversion. However, when the output of the 266 nm laser exceeds 180 mW, the crystal is damaged by photorefractive damage. Recently developed mature CLBO crystals, not only crystal growth is easier than BBO, the single crystal grows larger than BBO, and it is not broken when the output of 266nm reaches 40 watts. In this area, CLBO has a tendency to replace BBO.
3) Periodic polarization quasi-phase matching technique (QPM) for nonlinear optical crystals
China is at the international leading level in the research of periodic and quasi-periodic polarization phase matching. Because such quasi-phase matching devices can fully exert the nonlinear optical performance of the crystal, and a crystal can simultaneously perform functions such as frequency multiplication, sum frequency, and parametric oscillation. Therefore, such technologies have important applications in optical communication, laser display, air pollution detection, medicine, and national defense. QPM materials and devices are showing their vitality. Currently more important are PPLN, PPKTP and PPRTA ("PP" is also one of the "quasi-phase matching" notation).
4) Infrared band nonlinear optical crystals Compared with nonlinear crystals in the visible and ultraviolet bands, the nonlinear crystal in the infrared band develops slowly. The main reason is that the optical damage threshold of the existing infrared nonlinear crystal is too low, which directly affects actual use. Since infrared nonlinear optical crystals have important application prospects in the military, this kind of crystal material has become a key development direction in the field of nonlinear optics.
5) New photorefractive crystal materials Existing photorefractive materials such as LiNbO3, BaTiO3, etc., when optical information storage applications, the photorefractive response speed is not fast enough, storage noise is still relatively large, the performance of these two aspects It is still not comparable to the currently widely used electromagnetic storage technology. Therefore, it is necessary to find a new type of photorefractive crystal material with better performance or further improve the modification of the existing photorefractive material.
IV. Development Thoughts and Key Points China has made remarkable progress in the industrialization of nonlinear optical crystals, and established some production lines. Some crystal varieties have been commercialized, such as KTP, LBO, BBO, LN, LT, etc. In addition to meeting domestic demand, a large number of exports.
However, at present, there is still a big gap between the industrialization process of nonlinear crystals in China and the needs of technological development. The requirements for the development of traditional industries and high-tech fields have not been met in both quality and quantity; the overall level of research (application) development is especially There is still a considerable gap between the level of industrialization and foreign countries, and it has not yet formed a set of industrial systems in the true sense of organic connection. Specifically in:
1) The production equipment is backward, the control level is low, the single machine output is low, the yield is low, and the product quality is unstable;
2) Industry dispersion and small scale (some varieties such as LiNbO3, although the total output is large, but not strong, the product grade is low, the optical grade crystal is less, mostly piezoelectric);
3) The variety is small, the specifications are not complete, and the gap between components and developed countries is greater, which is related to the level difference of crystal deep processing such as polishing, coating and precision processing of components;
4) The level of industrialization and engineering is low. On the one hand, some crystal materials with excellent performance are still in the laboratory research stage, which cannot meet the needs of high-tech development. On the other hand, the laboratory results are transformed into industrialization technology level of productivity. Extremely needed to improve;
5) The industrialization is weak, the resources are not effectively utilized, and a complete industrial chain and industrial system have not been established. The division of management system is divided; the investment intensity is low and scattered; the development of raw materials and special instruments and equipment compatible with crystal production is unbalanced; the application and development of products need to be strengthened, and the disorderly competition between peers needs to be resolved. There is no effective combination mechanism between production and application, and new materials, new products are promoted and applications are weak.
According to China's dominant position in the field of nonlinear crystals, China's international optoelectronic functional crystal industry, especially the development trend of the laser and nonlinear crystal industry and the world market, focus on strengths, take advantage, take key breakthroughs, and concentrate on To overcome some of the crystal varieties that are of great significance to the national economy and national defense construction, China's non-linear crystal output value reached 1.5 billion yuan in 2010 and 3 billion yuan in 2020.
Development focus
1) Nonlinear optical crystals used in optical communication and integrated optics, including quasi-phase matching (QPM) multi-domain structural crystal materials and components;
2) Nonlinear optical crystals used in laser red, green and blue primary light sources;
3) Semiconductor frequency doubling crystals (such as KN and some possible QPM products) applied to the next generation optical disc blue light source;
4) Development and production of new infrared, ultraviolet and deep ultraviolet nonlinear crystals.
The nonlinear optical crystal material can be used for laser frequency conversion, expanding the wavelength of the laser; for modulating the intensity and phase of the laser; realizing the holographic storage of the laser signal, eliminating the self-pumping phase conjugate of the wavefront domain change, and the like. Therefore, nonlinear optical crystals are indispensable key materials in high-tech and modern military technology. All developed countries have placed them in a priority development position and listed them as an important strategic measure in their respective high-tech development plans. Give high priority and support.
With the development of laser technology since the 1960s, nonlinear optical crystals have also been greatly developed. From the initial quartz frequency doubling crystals, lithium niobate (LiNbO3-LN) and potassium dihydrogen phosphate (KH2PO4) have emerged. —KDP), potassium dipotassium phosphate (KD2PO4—DKDP), lithium iodate (LiIO3-LI), potassium titanyl phosphate (KTiOPO4-KTP), barium metaborate (-BaB2O4-BBO), lithium triborate (LiB3O5—LBO ), potassium citrate (KNbO3-KN), bismuth borate (CSB3O5-CBO), lithium lanthanum borate (LiCSB6O10-CLBO), potassium fluoroborate bismuth (KBe2BO3F2-KBBF), and silver-silver gallium (AgGaS2-AGS), arsenic cadmium telluride Nonlinear optical crystals such as (CdGeAs-CGA) and bismuth zinc (ZnGeP2-ZGP) are widely used in laser frequency doubling, sum frequency, difference frequency, optical parametric amplification, electro-optic modulation, and electro-optical deflection. A more representative example is: optical waveguide devices and modulation devices made with LN have been widely used in optical communication; commercial intracavity frequency-doubled YAG lasers using KTP crystals have a green light output of several hundred watts; with CBO and Frequency YAG triple frequency laser, 355nm output has reached 17.7 watts; with CLBO quadruple frequency YAG laser, 266nm ultraviolet light output has reached 42 watts; with KBBF direct six times frequency has obtained 177.3nm deep ultraviolet laser; use KTP , BBO, LBO optical parametric oscillator, the tuning range covers visible light to 4.5m band, and achieve single longitudinal mode operation.
In terms of the level of science and technology in the field of nonlinear optical crystals, devices and applications, developed countries such as the United States and the United Kingdom are among the best in 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, some countries in Japan, China, and the former Soviet Union, such as Russia, Ukraine, and Lithuania, occupy an important position, while some countries in the United States and Europe focus on the manufacture of nonlinear crystal devices and devices. . China occupies an important position in the field of nonlinear optical crystals.
I. China's World Position in the Field China has an important international influence in the academic research and industrialization of nonlinear optical crystals, especially in the field of visible and ultraviolet nonlinear crystals. , attracted the attention of the world. China's main achievements in the field of nonlinear crystals are (1) the invention of magnesium-doped LiNbO3 crystals, which has increased the damage threshold of LiNbO3 by more than two orders of magnitude by doping, which has greatly expanded the application field of lithium niobate crystals; In the borate series, a series of excellent UV nonlinear optical crystals such as BBO, LBO, CBO and KBBF have been discovered and developed, which has created a new era of ultraviolet laser frequency doubling, which has enabled humans to continuously push the limit of solid ultraviolet laser. (3) For the first time, the practical application of KTP large single crystals by solvent method has been carried out internationally, and industrialization has been realized, which has made KTP crystals widely used throughout the world and promoted the development of laser technology. (4) Leading the research and experimental verification of periodic and quasi-periodic polarization artificial microstructure nonlinear optical crystal materials, and opened up a new field of nonlinear optical crystals.
The growth technology of various nonlinear optical crystals in China is at the international advanced level. All the existing crystal growth methods in foreign countries are available in China. Almost all important nonlinear optical crystals have been grown, and some important crystals have met the major domestic engineering needs. A group of high-tech crystals have become commodities and enjoy high reputation in the world.
Second, the market demand analysis Nonlinear optical crystal material is a fairly certain industry closely related to the laser, optoelectronics, optical communications and other industries, greatly affected by the development and changes of these industries. With the rapid development of the world's informatization wave and the widespread adoption of optoelectronic technology at the end of the last century, the market demand for optoelectronic functional crystals, especially nonlinear optical crystals, has increased dramatically at home and abroad.
In recent years, the sales of nonlinear optical crystals worldwide have exceeded 400 million US dollars per year. The demand for traditional nonlinear crystals is still increasing year by year. In the next few years, the market growth rate is around 1530%.
Nonlinear optical components have shown accelerated development in three areas: modulation switches and telecommunications, information processing and entertainment.
The main commercial nonlinear optical crystals are lithium niobate (LiNbO3), potassium titanyl phosphate (KTP), barium metaborate (BBO), lithium triborate (LBO), potassium dihydrogen phosphate (KDP), diphosphoric acid Potassium (DKDP), etc., of which LiNbO3 is the largest nonlinear optical crystal in the market, optical communication and industrial laser are its two most important applications. The continuous development of the optical communication industry has made LiNbO3 crystals used in optical communication modulators not only occupy the vast majority of the market, but also the market share is growing every year.
In addition to optical communication, industrial laser and electro-optic are important markets for nonlinear optical crystal applications. In recent years, it has maintained a market growth of 1520% per year. Among them, BBO and KTP crystals are the fastest growing crystal varieties in the field in recent years. Prospects are promising.
The field of medical solid-state lasers is another important market for nonlinear optical crystals. The main applications are KTP, KDP and BBO crystals. CLBO will also be widely used. Due to the rapid development of lasers in the medical industry, the demand for nonlinear optical crystals such as KTP has also increased rapidly.
According to the latest report from the research firm BCC (Business Communications Company, Inc.), the global market for nonlinear optical crystals reached US$ 851.61 million in 2005. It is expected to expand to an annual average growth rate of 17.1% in 2009. About $1.656 billion. Among them, LiNbO3 for optical communication accounted for 24.5% of the market share of nonlinear optical crystal materials in 2005, and is expected to be 29.6% in 2009. Crystals such as KTP, KDP, DKDP, BBO, CLBO, and LBO used in the laser and electro-optical fields accounted for 18.5% of the market for nonlinear optical crystal materials in 2005, and the AAGR (annual average growth rate) for KTP crystals was 5.4%. The AAGR of other crystals is 8% in total.
From the perspective of the entire nonlinear optical crystal material, device and complete machine equipment, the developed countries such as the United States and Japan are industrial powers, and monopolize the large-scale production of nonlinear optical crystals such as LiNbO3. Small-scale materials such as KTP, BBO, LBO, etc., mainly dominated by China and Lithuania. In terms of device manufacturing, due to the strong technical strength and good industrial base, developed countries such as the United States and Europe occupy a decisive dominant position. Developed countries such as China can only provide crystal materials to developed countries and earn a small profit.
Third, the development trend
1) Development of ultraviolet to shorter wavelengths The development of all-solid-state deep ultraviolet (200 nm) coherent light sources is one of the most advanced research projects in the field of optoelectronics in the world. This is because UV lasers have important applications in many high-tech fields, such as A new generation of integrated circuit lithography requires an all-solid-state UV coherent light source; in photoelectron spectroscopy and spectroscopy, there is an urgent need for a tunable all-solid-state deep-UV coherent light source, which will drive the development of deep ultraviolet spectroscopy and spectrometers. To a critical role, and will open up a new field of material science research; deep ultraviolet coherent light source will also greatly promote the development of laser precision machinery processing industry. Since there is no laser crystal directly outputting deep ultraviolet wavelength, the key problem of solving solid-state deep ultraviolet laser light source is concentrated on the development and application development of NLO frequency conversion crystal in the ultraviolet band. The prospect of driving related industrial development and technological progress is very attractive. Human.
2) Improvement of the performance of existing nonlinear optical crystals and development of new crystals A typical example is the stoichiometric ratio of LiNbO3 (abbreviated as SLN). Due to the improved structural integrity, SLN is more common than conventional molten lithium niobate (CLN for short). There is a qualitative leap in performance. If the practical technology is solved, revolutionary changes will be made in the fields of optoelectronics and optical communication. - BBO is a nonlinear optical crystal that is first used to quadruple the 1064 nm laser output from Nd:YAG to obtain 266 nm ultraviolet light. It has been used for decades in this field of frequency conversion. However, when the output of the 266 nm laser exceeds 180 mW, the crystal is damaged by photorefractive damage. Recently developed mature CLBO crystals, not only crystal growth is easier than BBO, the single crystal grows larger than BBO, and it is not broken when the output of 266nm reaches 40 watts. In this area, CLBO has a tendency to replace BBO.
3) Periodic polarization quasi-phase matching technique (QPM) for nonlinear optical crystals
China is at the international leading level in the research of periodic and quasi-periodic polarization phase matching. Because such quasi-phase matching devices can fully exert the nonlinear optical performance of the crystal, and a crystal can simultaneously perform functions such as frequency multiplication, sum frequency, and parametric oscillation. Therefore, such technologies have important applications in optical communication, laser display, air pollution detection, medicine, and national defense. QPM materials and devices are showing their vitality. Currently more important are PPLN, PPKTP and PPRTA ("PP" is also one of the "quasi-phase matching" notation).
4) Infrared band nonlinear optical crystals Compared with nonlinear crystals in the visible and ultraviolet bands, the nonlinear crystal in the infrared band develops slowly. The main reason is that the optical damage threshold of the existing infrared nonlinear crystal is too low, which directly affects actual use. Since infrared nonlinear optical crystals have important application prospects in the military, this kind of crystal material has become a key development direction in the field of nonlinear optics.
5) New photorefractive crystal materials Existing photorefractive materials such as LiNbO3, BaTiO3, etc., when optical information storage applications, the photorefractive response speed is not fast enough, storage noise is still relatively large, the performance of these two aspects It is still not comparable to the currently widely used electromagnetic storage technology. Therefore, it is necessary to find a new type of photorefractive crystal material with better performance or further improve the modification of the existing photorefractive material.
IV. Development Thoughts and Key Points China has made remarkable progress in the industrialization of nonlinear optical crystals, and established some production lines. Some crystal varieties have been commercialized, such as KTP, LBO, BBO, LN, LT, etc. In addition to meeting domestic demand, a large number of exports.
However, at present, there is still a big gap between the industrialization process of nonlinear crystals in China and the needs of technological development. The requirements for the development of traditional industries and high-tech fields have not been met in both quality and quantity; the overall level of research (application) development is especially There is still a considerable gap between the level of industrialization and foreign countries, and it has not yet formed a set of industrial systems in the true sense of organic connection. Specifically in:
1) The production equipment is backward, the control level is low, the single machine output is low, the yield is low, and the product quality is unstable;
2) Industry dispersion and small scale (some varieties such as LiNbO3, although the total output is large, but not strong, the product grade is low, the optical grade crystal is less, mostly piezoelectric);
3) The variety is small, the specifications are not complete, and the gap between components and developed countries is greater, which is related to the level difference of crystal deep processing such as polishing, coating and precision processing of components;
4) The level of industrialization and engineering is low. On the one hand, some crystal materials with excellent performance are still in the laboratory research stage, which cannot meet the needs of high-tech development. On the other hand, the laboratory results are transformed into industrialization technology level of productivity. Extremely needed to improve;
5) The industrialization is weak, the resources are not effectively utilized, and a complete industrial chain and industrial system have not been established. The division of management system is divided; the investment intensity is low and scattered; the development of raw materials and special instruments and equipment compatible with crystal production is unbalanced; the application and development of products need to be strengthened, and the disorderly competition between peers needs to be resolved. There is no effective combination mechanism between production and application, and new materials, new products are promoted and applications are weak.
According to China's dominant position in the field of nonlinear crystals, China's international optoelectronic functional crystal industry, especially the development trend of the laser and nonlinear crystal industry and the world market, focus on strengths, take advantage, take key breakthroughs, and concentrate on To overcome some of the crystal varieties that are of great significance to the national economy and national defense construction, China's non-linear crystal output value reached 1.5 billion yuan in 2010 and 3 billion yuan in 2020.
Development focus
1) Nonlinear optical crystals used in optical communication and integrated optics, including quasi-phase matching (QPM) multi-domain structural crystal materials and components;
2) Nonlinear optical crystals used in laser red, green and blue primary light sources;
3) Semiconductor frequency doubling crystals (such as KN and some possible QPM products) applied to the next generation optical disc blue light source;
4) Development and production of new infrared, ultraviolet and deep ultraviolet nonlinear crystals.
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