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Mid-infrared ZGP OPO pumped by near-degenerate narrowband type-I PPKTP parametric oscillator.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.ORCID-id: 0000-0002-2508-391X
KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.ORCID-id: 0000-0001-7688-1367
2007 (Engelska)Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 88, nr 1, s. 37-41Artikel i tidskrift (Refereegranskat) 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%.

Ort, förlag, år, upplaga, sidor
2007. Vol. 88, nr 1, s. 37-41
Nyckelord [en]
2 mu-m, linewidth, power
Nationell ämneskategori
Fysik
Identifikatorer
URN: urn:nbn:se:kth:diva-6721DOI: 10.1007/s00340-007-2661-3ISI: 000247306900006Scopus ID: 2-s2.0-34250616712OAI: oai:DiVA.org:kth-6721DiVA, id: diva2:11510
Anmärkning
Tidigare titel: Efficient pumping of ZGP OPO by narrowband near degenerate PPKTP OPO. Uppdaterad från submitted till published(20101108). QC 20101108Tillgänglig från: 2007-01-10 Skapad: 2007-01-10 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
Ingår i avhandling
1. Nanosecond tandem optical parametric oscillators for mid-infrared generation
Öppna denna publikation i ny flik eller fönster >>Nanosecond tandem optical parametric oscillators for mid-infrared generation
2007 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2007. s. xi, 40
Serie
Trita-FYS, ISSN 0280-316X ; 2006:83
Nyckelord
nonlinear optics, optical parametric oscillators, quasi-phase matching, mid-infrared, linewidth narrowing, volume Bragg gratings.
Nationell ämneskategori
Fysik
Identifikatorer
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 (Engelska)
Opponent
Handledare
Anmärkning
QC 20101108Tillgänglig från: 2007-01-10 Skapad: 2007-01-10 Senast uppdaterad: 2015-03-30Bibliografiskt granskad
2. Tandem optical parametric oscillators using volume Bragg grating spectral control
Öppna denna publikation i ny flik eller fönster >>Tandem optical parametric oscillators using volume Bragg grating spectral control
2010 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2010. s. xii; 54
Serie
Trita-FYS, ISSN 0280-316X ; 21
Nyckelord
optical parametric oscillators, mid-infrared, volume Bragg gratings, PPKTP, ZGP, nonlinear optics, narrowband OPO
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:kth:diva-12864 (URN)978-91-7415-626-3 (ISBN)
Disputation
2010-06-04, Sal FA32, AlbaNova, Roslagstullsbacken 21, Stockholm, 16:00 (Engelska)
Opponent
Handledare
Anmärkning
QC 20100517Tillgänglig från: 2010-05-17 Skapad: 2010-05-17 Senast uppdaterad: 2010-11-08Bibliografiskt granskad

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