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Tandem optical parametric oscillators using volume Bragg grating spectral control
KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
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 [en]
optical parametric oscillators, mid-infrared, volume Bragg gratings, PPKTP, ZGP, nonlinear optics, narrowband OPO
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-12864ISBN: 978-91-7415-626-3 (print)OAI: oai:DiVA.org:kth-12864DiVA: diva2:319380
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
List of papers
1. Narrow linewidth 2 mu m optical parametric oscillation in periodically poled LiNbO3 with volume Bragg grating outcoupler
Open this publication in new window or tab >>Narrow linewidth 2 mu m optical parametric oscillation in periodically poled LiNbO3 with volume Bragg grating outcoupler
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.

Keyword
All fiber Michelson interferometer, Add and drop multiplexer
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-12858 (URN)10.1007/s00340-006-2446-0 (DOI)000244292500025 ()2-s2.0-33847218682 (Scopus ID)
Note
QC 20100517Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
2. ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 μm source
Open this publication in new window or tab >>ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 μm source
2006 (English)In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, 1878-1880 p.Article in journal (Refereed) Published
Abstract [en]

A tandem optical parametric oscillator (OPO) is used to convert radiation from 1.064 μm to the mid-infrared. Spectral bandwidth narrowing close to 80 times compared with a conventional cavity was achieved by using a bulk Bragg grating as an outcoupler in a near-degenerate periodically poled KTiOPO4 OPO. The narrowed 2008 nm radiation was subsequently used for pumping the ZnGeP2 OPO, which was tunable between 3.3 and 5.2 μm. Pulse energies of 170 μJ and pump depletion close to 70% were obtained in the ZnGeP2 OPO. To our knowledge this is the first time the output from a near-degenerate type I PPKTP OPO has been used for ZnGeP2 OPO pumping.

Keyword
Volume gratings ; Infrared and far-infrared lasers; Nonlinear optics, devices; Parametric oscillators and amplifiers
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-12859 (URN)10.1364/OL.31.001878 (DOI)000238156800034 ()2-s2.0-33745880111 (Scopus ID)
Note
QC 100517Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
3. Mode spectrum of multi-longitudinal mode pumped near-degenerate OPOs with volume Bragg grating output couplers
Open this publication in new window or tab >>Mode spectrum of multi-longitudinal mode pumped near-degenerate OPOs with volume Bragg grating output couplers
2009 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, no 20, 17582-17589 p.Article in journal (Refereed) Published
Abstract [en]

Spectral requirements for the first stage OPO used to pump a tandem ZGP mid-infrared OPO are theoretically investigated. Based on these requirements we demonstrate a singly-resonant type-I OPO including periodically poled KTiOPO4 and volume-Bragg gratings as output couplers. Singly resonant oscillation is demonstrated very close to degeneracy, where signal and idler spectra are not well separated. Investigations of the longitudinal mode spectrum and the idler spectrum with high resolution using a scanning Fabry-Perot interferometer show the essential role played by the phase correlations of the multi-longitudinal mode Q-switched pump laser in formation of the nonresonant idler spectrum.

Keyword
Volume gratings ; Parametric oscillators and amplifiers
Identifiers
urn:nbn:se:kth:diva-12861 (URN)000270295300036 ()2-s2.0-70349679288 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, 224042
Note
QC 100517Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
4. Cavity length resonances in a nanosecond singly resonant optical parametric oscillator
Open this publication in new window or tab >>Cavity length resonances in a nanosecond singly resonant optical parametric oscillator
2010 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, no 10, 10742-10749 p.Article in journal (Refereed) Published
Abstract [en]

Resonant output energy enhancement in a singly resonant nondegenerate type-I optical parametric oscillator with a volume Bragg grating output coupler is demonstrated. The resonances occur when the pump laser and parametric oscillator cavity length ratio is an integer or a fraction of small integers. Although the length resonances are similar to those observed in doubly resonant optical parametric oscillators, the physical mechanism is distinctly different. The resonances in the singly resonant oscillator are caused by correlation of the instantaneous power between the quasi-periodic multimode pump laser beam and the OPO signal.

Keyword
Volume gratings, Parametric oscillators and amplifiers
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-12862 (URN)10.1364/OE.18.010742 (DOI)000277560000098 ()2-s2.0-77952725335 (Scopus ID)
Funder
Swedish Research Council
Note
QC 20100517Available from: 2010-05-17 Created: 2010-05-17 Last updated: 2017-12-12Bibliographically approved
5. Mid-infrared ZGP OPO pumped by near-degenerate narrowband type-I PPKTP parametric oscillator.
Open this publication in new window or tab >>Mid-infrared ZGP OPO pumped by near-degenerate narrowband type-I PPKTP parametric oscillator.
2007 (English)In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 88, no 1, 37-41 p.Article in journal (Refereed) Published
Abstract [en]

The total pulse energy of the signal and idler in a near-degenerate type-I periodically poled KTiOPO4 (PPKTP) optical parametrical oscillator (OPO) was spectrally confined within a 2 nm spectral bandwidth at 2.13 mu m. This was achieved by using a volume Bragg grating as the output coupler. Both the signal and the idler from the PPKTP OPO were then simultaneously used to pump a mid-infrared ZnGeP2 (ZGP) OPO. The 2 nm bandwidth was narrower than the ZGP crystal acceptance bandwidth and, thus, made efficient conversion in the second OPO possible. A total slope efficiency of 10% from 1.06 mu m to the 3.5-5 mu m region was demonstrated, generating 250 mu J in the mid-IR with only 3.6 mJ of 1.06 mu m pump energy. This corresponds to a Nd:YAG pump to mid-IR conversion efficiency of 7%.

Keyword
2 mu-m, linewidth, power
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-6721 (URN)10.1007/s00340-007-2661-3 (DOI)000247306900006 ()2-s2.0-34250616712 (Scopus ID)
Note
Tidigare titel: Efficient pumping of ZGP OPO by narrowband near degenerate PPKTP OPO. Uppdaterad från submitted till published(20101108). QC 20101108Available from: 2007-01-10 Created: 2007-01-10 Last updated: 2015-03-30Bibliographically approved

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