2-D layer structure of index in KDP crystal and creation of diffraction grating

Research Project

Project/Area Number	14350009
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Research Field	Applied materials science/Crystal engineering
Research Institution	Osaka University
Principal Investigator	NAKATSUKA Masahiro Institute of Laser Engineering, Professor, レーザーエネルギー学研究センター, 教授 (20088462)
Co-Investigator(Kenkyū-buntansha)	FUJIMOTO Yasushi Institute of Laser Engineering, Research Associate, レーザーエネルギー学研究センター, 助手 (70343241) TSUBAKIMOTO Koji Institute of Laser Engineering, Research Associate, レーザーエネルギー学研究センター, 助手 (90270579)
Project Period (FY)	2002 – 2003
Project Status	Completed (Fiscal Year 2003)
Budget Amount *help	¥6,700,000 (Direct Cost: ¥6,700,000) Fiscal Year 2003: ¥3,600,000 (Direct Cost: ¥3,600,000) Fiscal Year 2002: ¥3,100,000 (Direct Cost: ¥3,100,000)
Keywords	Water-soluble crystal / Layered index structure / Impurity doping / Diffraction effect / Diffractive optical element / Laser damage threshold / KDP crystal / Automatic rapid growth method of crystal / KDP / 高速育成 / 縞構造 / 回折格子 / 屈折率構造 / 不純物添加結晶
Research Abstract	The rapid growing method of water-soluble crystals has been developed. In order to keep a controllability of crystal growth, an automatic growing technology was established by measuring a super-saturation of the solution. The growth rate was increased from 1-2 mm/day in a conventional method to 50 mm/day in the rapid growth method. A selective inclusion of an ionic metal as an impurity in the crystal, such as iron ion, has been studied in the rapid growing method in which a growth rate has been controlled in time. As a result, KDP crystal has been found having a layered structure of index in an a-axis. But, a crystal structure of KDP shows needle-like one at a growth with a high impurity level in a solution. The two dimensional structure of index in a crystal has been achieved of several micron thickness. Optical parameters were investigated as a diffractive optic element. The theoretical properties of a transmission or reflective grating were summarized with a diffraction efficiency, wavelength matching, and allowance of the diffraction. The diffraction effect by layered structure of index was measured in an experiment showing a several-microns structure, then suggesting that 10^<-4>□ 10^<-5> index mismatching was needed for an efficient diffraction. The thermal shock parameter of KDP was measured for increasing strength of crystal at using an average power condition. In conclusion, the basic technology and knowledge have been established for a development of the diffractive optics in use at power laser system such as pulse compression, so on.