The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
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Passively Q-Switched Nd:YAG Lasers and Their Use in UV Light Generation

Ossi Kimmelma

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium AS2 at Helsinki University of Technology (Espoo, Finland) on the 6th of November, 2009, at 12 noon.

Overview in PDF format (ISBN 978-952-248-074-3)   [1474 KB]
Dissertation is also available in print (ISBN 978-952-248-073-6)

Abstract

Recent advances in optoelectronics open up possibilities to realize new kinds of solid state lasers that utilize powerful diode lasers as pump sources. A laser medium has often several appropriate transitions that provide conditions for lasing. Bright pump sources that have recently become available enable building of efficient lasers for wavelengths utilizing such laser transitions that have been unpractical or even totally unattainable.

Pulsed lasers are used to create the intensity needed in the nonlinear conversion. With such a laser, focusing of the light beam into the nonlinear crystal is enough to obtain a decent conversion in the range of a few tens of percents. However, this applies to a laser that is designed to produce high enough peak power for the conversion. In this thesis, passive Q-switching is used to develop high peak power laser sources enabling compact and robust lasers. With these laser sources cascaded frequency conversion using nonlinear processes is demonstrated ranging from IR to deep UV wavelengths.

In this thesis, passively Q-switched Nd:YAG laser crystal was used in lasers putting out pulses at 946, 1064 and 1123 nm. By second harmonic generation these lasers were used in creating light in the visible wavelength range at 473 and 561 nm. By further conversions to UV the wavelengths of 374, 280 and 236 nm were created. At IR wavelengths, peak powers of 3.7 and 3.2 kW at 946 and 1123 nm were achieved, respectively, while the peak powers for the deep UV lasers were 100 and 120 W at wavelengths of 280 and 236 nm, respectively. Tuning of the pulse properties was studied through adjusting the laser crystal temperature in Q-switched Nd:YAG laser at 1064 nm. A remarkable 90 per cent change in peak power was achieved by heating of the laser mount by 100°C with all the studied lasers.

This thesis consists of an overview and of the following 5 publications:

  1. Ossi Kimmelma, Matti Kaivola, Ilkka Tittonen, and Scott Buchter. 2007. Short pulse, high peak power, diode pumped, passively Q-switched 946 nm Nd:YAG laser. Optics Communications, volume 273, number 2, pages 496-499. © 2006 Elsevier Science. By permission.
  2. Ossi Kimmelma, Ilkka Tittonen, and Scott C. Buchter. 2008. Short pulse, diode pumped, passively Q-switched Nd:YAG laser at 946 nm quadrupled for UV production. Journal of the European Optical Society - Rapid Publications, volume 3, 08008, 5 pages. © 2008 by authors.
  3. Ossi Kimmelma, Ilkka Tittonen, and Scott C. Buchter. 2008. Thermal tuning of laser pulse parameters in passively Q-switched Nd:YAG lasers. Applied Optics, volume 47, number 23, pages 4262-4266. © 2008 Optical Society of America (OSA). By permission.
  4. Ossi Kimmelma and Ilkka Tittonen. 2009. Passively Q-switched Nd:YAG pumped UV lasers at 280 and 374 nm. Optics Communications, volume 282, number 14, pages 2930-2933. © 2009 Elsevier Science. By permission.
  5. E. Räikkönen, O. Kimmelma, M. Kaivola, and S. C. Buchter. 2008. Passively Q-switched Nd:YAG/KTA laser at 561 nm. Optics Communications, volume 281, numbers 15-16, pages 4088-4091. © 2008 Elsevier Science. By permission.

Keywords: solid state lasers, nonlinear optics, passive Q-switching

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© 2009 Helsinki University of Technology

Last update 2011-05-26