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Tunable Mid-infrared ZnGeP2 RISTRA OPO pumped by periodically-poled Rb:KTP optical parametric master-oscillator power amplifier
French–German Research Institute of Saint Louis ISL.
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.ORCID iD: 0000-0001-8764-3372
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.
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2012 (English)In: Optics Express, ISSN 1094-4087, Vol. 20, no 4, 4509-4517 p.Article in journal (Refereed) Published
Abstract [en]

A laser-diode pumped Q-switched single-frequency Nd:YAG MOPA operating at 100 Hz was used to generate tunable mid-infrared radiation between 6.27 µm and 8.12 µm by employing a cascaded parametric arrangement consisting of degenerate parametric master-oscillator power amplifier using a large aperture periodically-poled Rb:KTiOPO4 which in turn pumped a ZnGeP2 (ZGP) nonplanar RISTRA OPO. The noncollinear ZGP RISTRA tuning behavior is elucidated. The device is aimed for minimally invasive surgery applications at 6.45 µm where the peak power of 193 kW in 5 ns pulses is demonstrated.

Place, publisher, year, edition, pages
2012. Vol. 20, no 4, 4509-4517 p.
National Category
Atom and Molecular Physics and Optics
URN: urn:nbn:se:kth:diva-79485DOI: 10.1364/OE.20.004509ISI: 000301041900116ScopusID: 2-s2.0-84857319219OAI: diva2:495563
QC 20120507Available from: 2012-02-09 Created: 2012-02-09 Last updated: 2014-12-03Bibliographically approved
In thesis
1. Highly efficient optical parametric oscillators in the mid-IR
Open this publication in new window or tab >>Highly efficient optical parametric oscillators in the mid-IR
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis shows how sources of coherent radiation in the mid-infrared (mid-IR) region can be enhanced. To achieve this, optical parametric oscillators (OPOs) employing improved novel materials, new optical elements, and novel cavity designs have been implemented. Moreover, important measurements for the development of ultrashort-pulsed lasers were conducted. In turn, such lasers are suitable pump sources for the nonlinear conversion to the mid-IR.

The mid-infrared spectral region is of interest for many applications in the areas of medicine, sensing, climate monitoring, and ranging. Here the target wavelength 6.45μm was especially interesting since it is considered particularly useful in surgical applications. Commercially available lasers perform poorly as pump sources for the generation of this wavelength. Therefore, a superior cascaded conversion scheme with large aperture crystals was implemented. In these, Rb-doped KTiOPO4(KTP) was employed since it was found that Rb-doping improves the poling properties of KTP. Moreover, for the conversion scheme to be efficient, a narrow-band out putspectrum of the OPO is required. It was shown here that this can successfully be achieved by utilizing a volume Bragg grating (VBG).

Alternatively, for the direct generation of mid-IR radiation, KTiOAsO4(KTA) crystals with an extended transmission into the mid-IR as compared to KTP have been investigated. Novel room-temperature periodic-poling of KTA was shown and the fabricated crystals were successfully employed in a highly-efficient OPO.

The newly developed pump sources based on the Rb-doped KTP crystals were successfully implemented in a cascaded OPO experiment. Here, a so-called RISTRA cavity was employed and high-energy nanosecond pulses at 6.45μm with improved beam quality were demonstrated.

Pulsed lasers emitting at around 1μm, e.g. Yb-doped host materials, are frequently employed as pump sources of nonlinear optical conversion schemes. To allow further development of ultrashort pulsed Yb-doped double tungstate lasers, the nonlinear refractive index of several materials was measured. Among these are new materials which were for the first time characterized with regard to their nonlinear refractive index.

In addition to the pulsed experiments above, a periodically poled lithium niobate crystal was employed to generate continuous-wave output. Even here, a volume Bragg grating was implemented and thereby demonstrated a novel method to control the threshold of the OPO. Thus, a stable high-energy highly-efficient OPO could be demonstrated.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xiii, 69 p.
National Category
Atom and Molecular Physics and Optics
Research subject
urn:nbn:se:kth:diva-156714 (URN)978-91-7595-366-3 (ISBN)
Public defence
2014-12-19, FB 53, Roslagstullsbacken, AlbaNova, KTH, Stockholm, 10:00 (English)

QC 20141203

Available from: 2014-12-03 Created: 2014-12-02 Last updated: 2015-03-30Bibliographically approved

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