Characterization of KDP crystals used in large aperture doublers and triplers

We report on laser-induced damage threshold (LIDT) and UV-laser excited defect formation measurements in large aperture KDP crystals developed as doublers and triplers for mega-Joule laser. Measurements of LIDT were performed according to the ISO 11254-2 standard for repetitive pulses with duration ~ 4 ns and repetition rate of 10 Hz. The results for different laser wavelengths (1064, 532 and 355 nm) and polarizations are presented. The largest LIDT was observed for 532 nm pulses and the 1064 nm wavelength had a strong dependence on laser polarization. The LIDT values at 532 nm and 355 nm also depended on the crystal cutting angle, which is different for doublers and triplers. A comparison of LIDT with earlier reported crystal absorptance at different wavelengths is also performed. The UV-laser induced defect formation was investigated by the means of pump-probe technique. The excitation was performed with a single pulse of ns Nd:YAG laser (355 or 266 nm wavelength) and probing with another Nd:YVO4 laser system (532 nm) operating at 1kHz. This gave us a temporal resolution of 1ms. The transient absorption of defect states relaxed non-exponentially and fully disappeared in ~10 s. A comparison is made between crystal grown by distinct growth methods and between different laser polarizations. An influence of laser conditioning on UV induced defect state formation is also revealed.

[1]  Hisanori Fujita,et al.  Investigation of bulk laser damage in KDP crystal as a function of laser irradiation direction, polarization, and wavelength , 2000 .

[2]  Fred P. Milanovich,et al.  High‐laser‐damage‐threshold potassium dihydrogen phosphate crystals , 1990 .

[3]  Stavros G. Demos,et al.  Production and thermal decay of radiation-induced point defects in KD2PO4 crystals , 2003 .

[4]  Mark A. Henesian,et al.  Ultraviolet-induced transient absorption in potassium dihydrogen phosphate and its influence on frequency conversion , 1994 .

[5]  Aaas News,et al.  Book Reviews , 1893, Buffalo Medical and Surgical Journal.

[6]  Robert S. Hughes,et al.  Investigation of optically generated transient electronic defects and protonic transport in hydrogen-bonded molecular solids. Isomorphs of potassium dihydrogen phosphate , 1993 .

[7]  A. Yokotani,et al.  Growth of large KDP crystals for laser fusion experiments , 1990 .

[8]  Stavros G. Demos,et al.  Bulk defect formations in KH2PO4 crystals investigated using fluorescence microscopy , 2003 .

[9]  Mark A. Rhodes,et al.  Plasma electrode pockels cell for ICF lasers , 1995, Other Conferences.

[10]  H. Fujita,et al.  Rapid growth over 50 mm/day of water-soluble KDP crystal , 1997 .

[11]  Laurent Lamaignère,et al.  Linear and nonlinear absorption and defects formation in KDP crystals used for large aperture doublers and triplers , 2005, SPIE Optics + Optoelectronics.

[12]  James J. De Yoreo,et al.  Thermal and laser conditioning of production and rapid growth KDP and KD*P crystals , 1994, Laser Damage.

[13]  David Milam,et al.  Improving the bulk laser damage resistance of potassium dihydrogen phosphate crystals by pulsed laser irradiation , 1982 .

[14]  Y. Nishida,et al.  Formation of macroscopic hillocks on the prismatic faces of KDP crystals due to microbes in the solution , 1987 .

[15]  John D. Boyes,et al.  Conceptual design of the National Ignition Facility , 1995, Other Conferences.