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Efficient Nd: YAG laser frequency doubling with periodically poled KTP
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.ORCID iD: 0000-0002-2508-391X
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.ORCID iD: 0000-0001-7688-1367
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1998 (English)In: Applied Optics, ISSN 0003-6935, E-ISSN 1539-4522, Vol. 37, no 30, 7116-7119 p.Article in journal (Refereed) Published
Abstract [en]

Periodically poled flux-grown KTiOPO4 was used for efficient extracavity 1064-nm Nd:YAG laser frequency doubling. A conversion efficiency exceeding 65% was obtained in Q-switched operation, and 1.34 W of average frequency-doubled power was generated with 2.2 W of mode-locked laser output. The conversion efficiency is approximately two times higher for periodically poled KTP than for conventional type II phase-matched KTP. The measurements indicate that periodically poled KTP is less susceptible to optical damage than type II KTP.

Place, publisher, year, edition, pages
Optical Society of America , 1998. Vol. 37, no 30, 7116-7119 p.
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-8753DOI: 10.1364/AO.37.007116OAI: diva2:14163
QC 20111007Available from: 2005-11-09 Created: 2005-11-09 Last updated: 2015-03-30Bibliographically approved
In thesis
1. Fabrication and characterization of periodically poled KTB and RB-doped KTB for applications in the visible and UV
Open this publication in new window or tab >>Fabrication and characterization of periodically poled KTB and RB-doped KTB for applications in the visible and UV
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis deals with the fabrication and the characterization of periodically-poled crystals for use in lasers to generate visible and UV radiation by second-harmonic generation (SHG) through quasi-phasematching (QPM). Such lasers are of practical importance in many applications like high-density optical storage, biomedical instrumentation, colour printing, and for laser displays.

The main goals of this work were: (1) to develop effective monitoring methods for poling of crystals from the KTiOPO4 (KTP) family, (2) to develop useful non-destructive domain characterization techniques, (3) to try to find alternative crystals to KTP for easier, periodic poling, (4) to investigate the physical mechanisms responsible for optical damage in KTP. The work shows that the in-situ SHG technique used together with electro-optic monitoring, makes it possible to obtain reliable, real-time information regarding the poling quality over the whole crystal aperture during the electric-field poling process. Using this combined monitoring method, both KTP and Rb-doped KTP (RKTP) crystals were successfully poled. By comparing these two crystals, we found that a low-doped KTP has a substantially reduced ionic conductivity and, thus, a high-quality periodic poling can be obtained without otherwise affecting the properties of the crystal. RKTP is a good alternative candidate to KTP for poling purpose. We have also shown that Atomic Force Microscopy (AFM) is an informative tool for investigating domain nucleation, growth, and merging. Furthermore, we have demonstrated a simple technique for 3D characterization of QPM samples. It utilizes a group-velocity mismatched, type-II SHG of femtosecond pulses for layer-by-layer monitoring of the effective nonlinearity along the propagation direction of the beam. The quality of these crystals was finally reflected in a number of SHG experiments with a variety of laser sources. High energies and high efficiencies were thus demonstrated using CW, mode-locked and Q-switched lasers. Gratings with pitches smaller than 3 µm, were demonstrated for first-order UV generation. Type-II QPM SHG was demonstrated as a technique for reducing the fabrication constraints.

High intensity light in the visible and the UV leads to modification of the material properties and, eventually, to optical damage. In KTP and its isomorphs, the first sign of material change is an optically-induced absorption. We have used thermal-lens spectroscopy with a common-path interferometer for high-sensitivity measurements of green light-induced infrared absorption dynamics in single-domain and periodically-poled KTP (PPKTP). The saturated, green light-induced absorption has been shown to be consistently higher in periodically-poled crystals, and is attributed to the creation of stoichiometric and interstitial defects in the crystals during the poling process. Finally, irreversible bulk damage thresholds in PPKTP have been determined for pulsed frequency converters. As the characteristics of optical damage are closely related to the material quality, this investigation can provide useful information for crystal manufactures and will help to optimise the crystal growth conditions.

Trita-FYS, ISSN 0280-316X ; 2005:50
Nonlinear optics, second-harmonic generation, quasi-phasematching, type-I QPM SHG, type-II QPM SHG, KTP, RKTP, periodic electric-field poling
National Category
Physical Sciences
urn:nbn:se:kth:diva-483 (URN)91-7178-153-6 (ISBN)
Public defence
2005-11-25, Sal FB53, AlbaNova, Roslagstullsbacken 21, Stockholm, 10:00
Available from: 2005-11-09 Created: 2005-11-09 Last updated: 2012-03-22

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