Abstract

At present, there are four kinds of high-quality nonlinear crystals that can be practically used in the world, namely BBO, LBO, KBBF, and KTP. Among them, the KTP crystal was invented by DuPont Company of the United States. The other three crystals were discovered and developed by Chen Chuangtian and others of the Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences. Professor Chen Chuangtian led a research group that proposed the renowned theory of anionic groups. This theory fundamentally suggests that nonlinear optical effects are localized effects, which are the geometric accumulation of the microscopic coefficients of the basic units that make up crystals – the anionic groups. The microscopic second-harmonic generation coefficient of the anionic groups can be calculated through localized quantum chemical orbital theory and second-order perturbation theory. Thanks to the backing of this anionic group theory, the Fujian Institute of Research on the Structure of Matter (Fujian CASTECH Crystals) successively developed BBO, LBO, and KBBF crystals. 

Among these three, BBO and LBO crystals were acclaimed as "Chinese brand" crystals by the international academic community in the 1990s. Over more than three decades of development, BBO and LBO crystals have become the top choice for leading ultrafast Laser, UV Solid-state laser field, and OPO laser companies worldwide, holding a market share of over 85%.

History

In 1979, Chen Chuangtian began to explore new nonlinear optical crystals in the borate compound system, and found that the (B3O6) group was an ideal basic structural unit for exploring a new generation of nonlinear optical crystals, and discovered the (B3O7) group LiB3O5 (referred to as LBO) crystals with group as the basic structural unit and KBe2BO3F2 (KBBF) with (BO3) group as the basic structural unit.

In 1980, Chen Chuangtian's research group determined that the discovered barium borate compound with strong nonlinear optical effect was low-temperature phase barium metaborate, and its chemical formula was β-BaB2O4, referred to as BBO .

In September 1983, Chen Chuangtian reported the nonlinear optical properties of BBO crystals to foreign counterparts for the first time, which aroused the attention of the international laser community.

In 1987, Chen Chuangtian and his research team discovered and grown the second "Chinese brand" LBO nonlinear optical crystal .

Honors for BBO Crystals

1984: Chinese Academy of Sciences Award for Scientific and Technological Progress - Grand Prize.

1985: First Prize at the First National Invention Exhibition.

1986: Chinese Academy of Sciences Award for Scientific and Technological Progress - Grand Prize.

1987: As a high-tech industrialized crystal product, it was selected as one of the "Top Ten Cutting-edge New Technology Products" by the editorial board and advisory committee of the American magazine "Lasers & Electro-Optics".

1988: First Chen Jiageng Award for Material Science.

1988: The applied results of its development won the Second Prize for Scientific and Technological Progress from the Chinese Academy of Sciences.

1988: The Third World Academy of Sciences Chemistry Award.

1990: "Industrial Achievement Award" granted by the American magazine "Laser Focus World".

1993: The patent won the China Invention Patent Gold Award.

Honors for LBO Crystals

1990: The LBO crystal was awarded the First Prize for Scientific and Technological Progress by the Chinese Academy of Sciences and was also named one of the Top Ten Laser Products of 1989 by an American laser magazine.

1991: The LBO crystal won the National Invention First Prize.

1999: The LBO crystal received the "China Invention Patent Gold Award" granted by the China National Intellectual Property Administration and the World Intellectual Property Organization.

2018: Awarded the Single-item Champion Product in Manufacturing by the Ministry of Industry and Information Technology (MIIT).

Introduction

BBO crystal is a nonlinear optical crystal which combines a number of unique features.Wide transparency and phase matching ranges, large nonlinear coefficient, high damage threshold and excellent optical homogeneity provide attractive possibilities for various nonlinear optical.Therefore, BBO crystal provides an attractive solution for various nonlinear optical applications like SHG,THG,4HG,5HG,OPO, OPA and others. As a result of large thermal acceptance bandwidth, high damage threshold and small absorption BBO well suits for frequency conversion of high peak or average power laser radiation.Large spectral transmission range as well as phase matching, especially in UV range, makes BBO nonlinear optical crystal perfectly suitable for frequency doubling of Dye, Arion and Copper vapour laser radiation, effective cascade harmonic generation (Frequency doublers, triplers, parametric amplifiers and wave mixers) of wide spread Nd:YAG as well as of ultrashort pulse Ti:Sapphire and Alexandrite laser radiation.

Lithium Triborate(LBO) nonlinear crystal is one of the most excellent nonlinear optical crystals found so far that can be used for non-critical phase matching laser frequency doubling.It has good nonlinear optical and stable physical and chemical properties, which is especially important because its dispersion amount is sensitive to temperature changes.Due to its large damage threshold, it can achieve non-critical phase matching during the frequency doubling process, which means it can achieve high-power fundamental pumping. Also, longer optical crystals can be used, which are undoubtedly useful for obtaining high-power frequency doubling lasers.The optical damage threshold of the LBO is the highest among the commonly used inorganic nonlinear optical crystals. Therefore, it is among the best choices for high-power second harmonic generators and other nonlinear optical applications.

Manufacturing level

In order to meet the market demand of BBO and LBO crystals, our processing and manufacturing level is also constantly improving after strive to explore and experiment.  

CRYSMIT can provide BBO crystals with the following specifications：

(1) Maximum processing size 20x20x10 mm3.

(2) As thin as 0.005mm with 1mm UVFS substrate.

(3) Processing Precision for BBO crystals:

(4) BBO crystal coating:  

• Protective coating (P-coating) ：Due to the low deliquescence of BBO, humid air tends to cloud the surface of polished BBO crystals. We use an effective protective coating (P-coating) to protect the crystal from moisture. This product has the following characteristics：① long lasting: It can be used for at least 6 months at 95% humidity, and longer at lower humidity (such as 80%)； ② High damage threshold: 1064nm wavelength, 30ps pulse width, greater than 7GW/cm2; 1064nm wavelength, 10ns pulse width, repetition rate 10Hz, 0.5GW/cm2. ③ Good transmission effect : In the wavelength range from 200 nm to 3500 nm, the transmission effect of the coated crystal is better than that of the uncoated crystal.

• Anti-reflection coating (AR-coating)：① We offer single and dual frequency anti-reflection coated BBOs for 1064nm and 532nm; ② Dual-frequency anti-reflection coating has the characteristics of low reflectance (less than 0.2% for 1064nm wave and less than 0.4% for 532nm wave), high damage threshold, moisture-proof and long service life;  ③ Coatings for other wavelengths is available.

CRYSMIT can provide LBO crystals with the following specifications：

(1) Maximum processing size 30x30 mm，Maximum processing Length 60mm.

(2) As thin as 0.01mm with 1mm UVFS substrate.

(3) Processing Precision for BBO crystals:

(4) LBO crystal anti-reflection coating: ① Nd:YAG laser frequency doubling LBO dual-frequency reflective coating (DBAR);  ② Low reflection (1064nm wavelength R<0.2%, 532nm wavelength R<0.5%);  ③ high optical damage threshold (dual band>500MW/cm2)Adjustable laser frequency doubling LBO broadband anti-reflection coating (BBAR); ④ Coatings for other wavelengths is available.

Notes for storage and use

• BBO has a low susceptibility to the moisture. Users are advised to provide dry conditions for both application and preservation of BBO.

• BBO is relatively soft and therefore requires precautions to protect its polished surfaces.

• When angle adjusting is necessary, please keep in mind that the acceptance angle of BBO is small.

• LBO has a low susceptibility to moisture. Users are advised to provide dry conditions for both the use and preservation of LBO.

• Polished surfaces of LBO requires precautions to prevent any damage.

Conclusion

Chinese brand BBO and LBO crystals have established themselves as high-quality products in the market. Their exceptional optical properties, competitive pricing, and extensive range of applications make them highly sought after. Inspired by the mission of "a powerful promoter of the development of the optoelectronic industry", CRYSMIT continue to pay attention to the application demands of the market, and continuously improve the internal quality of BBO crystals, especially to further reduce the absorption of ultraviolet bands, and through continuous growth and processing Technological innovation, further realizing mutual benefit and win-win with customers, makes the development of  “Chinese brand BBO and LBO crystals”more and more broad.