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Narrow linewidth 2 mu m optical parametric oscillation in periodically poled LiNbO3 with volume Bragg grating outcoupler
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
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.ORCID iD: 0000-0001-7688-1367
2007 (English)In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 86, 497-501 p.Article in journal (Refereed) Published
Abstract [en]

An optical parametric oscillator using a periodically poled LiNbO3 crystal and a volume Bragg grating output coupler is presented. Signal and idler wavelengths of 2008 and 2264 nm were generated from the 1064 nm Nd:YVO4 pump laser. The Bragg grating was reflecting in a narrow band around 2008 nm, creating a purely singly resonant cavity. Signal and idler linewidths of approximately 0.44 and 0.72 nm, respectively, were measured. This is a reduction of 80 and 60 times compared to when using a mirror as output coupler. A total output energy of 156 mu J was measured with 47% slope efficiency.

Place, publisher, year, edition, pages
2007. Vol. 86, 497-501 p.
Keyword [en]
All fiber Michelson interferometer, Add and drop multiplexer
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-12858DOI: 10.1007/s00340-006-2446-0ISI: 000244292500025Scopus ID: 2-s2.0-33847218682OAI: oai:DiVA.org:kth-12858DiVA: diva2:319358
Note
QC 20100517Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
In thesis
1. Nanosecond tandem optical parametric oscillators for mid-infrared generation
Open this publication in new window or tab >>Nanosecond tandem optical parametric oscillators for mid-infrared generation
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis discusses a new scheme for generating radiation in the mid infrared spectral region, especially the 3.5-5 µm range. The scheme uses established Nd3+-lasers at 1.06 µm and down conversion in nonlinear optical crystals. The down conversion is made by two optical parametric oscillators (OPO) in series. The second OPO is a classical OPO using a zink germanium phosphide (ZGP) crystal. ZGP is the best nonlinear material available for the 4-8 µm spectral range, but it is absorbing below 2 µm. The new development presented in this thesis is the OPO used to convert the 1.06 µm laser radiation to a suitable OPO pump near 2 µm.

The OPO uses a type I quasi phase-matched crystal, which accesses high nonlinearities and avoids walk-off. The problem with type I OPOs close to degeneracy is the broad bandwidth of the generated radiation, which reduces the efficiency of a second OPO. This has been solved with a spectrally selective cavity using a volume Bragg grating output coupler. Unlike other bandwidth limiting schemes this introduces no intracavity losses and thus efficient OPO operation is achievable.

Narrow linewidth (~0.5 nm) OPO operation has been achieved with periodically poled LiNbO3 (PPLN) and periodically poled KTiOPO4 (PPKTP) while locking the signal wavelength at 2008 nm and simultaneously generating an idler at 2264 nm. A high average power PPLN OPO with 36 % conversion efficiency and 47 % slope efficiency is reported. Operation very close to degeneracy at 2128 nm with the narrowband signal and idler peaks separated by 0.6 nm was demonstrated in a PPKTP OPO. Both the signal at 2008 nm and the combined signal and idler around 2128 nm from the PPKTP OPOs have been used to show efficient pumping of a ZGP OPO. The maximum conversion efficiency from 1 µm to the mid-IR demonstrated is 7 % with a slope efficiency of 10 %. This is not quite as high as what has been presented by other authors, but the experiments reported here have not shown the optimum efficiency of the new scheme. Relatively simple improvements are expected to give a significant increase in conversion efficiency.

Place, publisher, year, edition, pages
Stockholm: KTH, 2007. xi, 40 p.
Series
Trita-FYS, ISSN 0280-316X ; 2006:83
Keyword
nonlinear optics, optical parametric oscillators, quasi-phase matching, mid-infrared, linewidth narrowing, volume Bragg gratings.
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-4261 (URN)978-91-7178-552-7 (ISBN)
Presentation
2007-01-24, Sal FA32, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 13:15 (English)
Opponent
Supervisors
Note
QC 20101108Available from: 2007-01-10 Created: 2007-01-10 Last updated: 2015-03-30Bibliographically approved
2. Tandem optical parametric oscillators using volume Bragg grating spectral control
Open this publication in new window or tab >>Tandem optical parametric oscillators using volume Bragg grating spectral control
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis describes research on near degenerate quasi phase-matched opticalparametric oscillators (OPO) where volume Bragg gratings (VBG) are used toproduce narrow oscillation bandwidth. These OPOs are then used to pump a secondOPO to generate mid-infrared radiation.

The atmospheric transmission windows in the 3.5 to 5 μm wavelength region areused for seekers on infrared homing missiles. These missiles are available to guerrillaand terrorist groups and have been used in a number of attacks on military and civilianaircraft. Laser sources at the same wavelengths are an important component incountermeasure systems for aircraft self-protection. Similar laser sources also haveapplications in laser surgery.

At wavelengths longer than 4 μm crystal materials for multi-Watt level averagepower nonlinear devices is a problem. The best solution so far is to use ZnGeP2(ZGP). ZGP and the available alternatives all have a problem of near-infraredabsorption, and a mid-infrared OPO thus has to use a pump wavelength near 2 μm.This pump source can be a neodymium laser at 1.06 μm with a near degenerate OPO.

Nonlinear devices for low to medium pulse energies are dominated by quasi phasematchedmaterials because of their higher effective nonlinearities and lack of walkoff.In addition they allow type I interaction where signal and idler from the OPOhave the same polarization, which has the advantage that both waves can be used topump the ZGP OPO. The drawback of this is that the near-degenerate interaction hasvery wide gain bandwidth. Efficient pumping of the second OPO demands narrowbandwidth output from the first OPO.Volume Bragg gratings that are glass materials with a periodic refractive indexmodulation have emerged as high quality narrow bandwidth reflectors. By using aVBG as one cavity mirror in an OPO the feedback bandwidth and hence the OPOoscillation bandwidth can be kept very narrow. Signal and idler bandwidths of 10 and20 GHz (FWHM) at 2122 and 2135 nm, respectively, have been demonstrated. Thisshould be compared to the several hundred nanometre bandwidth from an OPO usingdielectric mirrors. Very narrow bandwidth operation has been achieved so close todegeneracy that the signal and idler are not resolvable.

The total output energy generated in the PPKTP OPO (signal and idler together)has been used to pump a ZGP OPO that produced mid-IR radiation. Tuning of thesignal from a ZGP OPO from 2.9 μm to degeneracy at 4.3 μm has been shown, with acorresponding idler wavelength tuneable up to 8 μm. The highest conversionefficiency that has been reached from 1.06 μm to the mid-IR was 12 %. This setupused a PPKTP OPO with 30 % conversion efficiency and 13 nm separation of signaland idler (2122 and 2135 nm). The pulse repetition frequency was 20 kHz and thegenerated output power in the mid-IR was 3.2 W.

Place, publisher, year, edition, pages
Stockholm: KTH, 2010. xii; 54 p.
Series
Trita-FYS, ISSN 0280-316X ; 21
Keyword
optical parametric oscillators, mid-infrared, volume Bragg gratings, PPKTP, ZGP, nonlinear optics, narrowband OPO
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-12864 (URN)978-91-7415-626-3 (ISBN)
Public defence
2010-06-04, Sal FA32, AlbaNova, Roslagstullsbacken 21, Stockholm, 16:00 (English)
Opponent
Supervisors
Note
QC 20100517Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2010-11-08Bibliographically approved

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Pasiskevicius, ValdasLaurell, Fredrik

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