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  • 1.
    Henriksson, Markus
    KTH, School of Engineering Sciences (SCI), Physics.
    Nanosecond tandem optical parametric oscillators for mid-infrared generation2007Licentiate 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.

  • 2.
    Henriksson, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tandem optical parametric oscillators using volume Bragg grating spectral control2010Doctoral 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.

  • 3.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. FOI.
    Sjökvist, Lars
    FOI.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Longitudinal mode structure of degenerate OPO with volume Bragg grating output coupler2008Conference paper (Refereed)
    Abstract [en]

    Optical parametric oscillators using volume Bragg gratings as cavity mirrors provide narrow bandwidth signals. The longitudinal mode spectrum of a 1.06 mu m pumped degenerate OPO is measured with Fabry-Perot etalon and compared to simulations

  • 4.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sjökvist, Lars
    FOI.
    Strömqvist, Gustav
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tandem PPKTP and ZGP OPO for mid-infrared generation2008In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 7115, p. 71150O1-10Article in journal (Refereed)
    Abstract [en]

    Efficient laser sources in the 3-5 μrn wavelength range are needed for directed infrared countermeasures, but also have applications in remote-sensing, medicine and spectroscopy. We present new results on our tandem optical parametric oscillator (OPO) scheme for converting the radiation from a 1.06 μm Nd3+-laser to the mid-infrared. Multi Watt level output power in the 3-5 μm range at 20 kHz pulse repetition frequency is reported. Our setup uses a type I quasi phasematched PPKTP crystal in a near degenerate OPO to generate 2.13 μm radiation. A volume Bragg grating resonant close to, but not exactly at the degenerate wavelength, is used as a cavity mirror to reduce the bandwidth and ensure singly resonant operation. Both signal and idler from the PPKTP OPO are used to pump a ZGP OPO generating high power radiation in the 3-5μm region. Using this scheme for each pump photon it is possible to generate four photons for each pump photon, all in the interesting wavelength range, thus enabling high efficiency conversion.

  • 5.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. Dept. of Laser Systems, Swedish Defence Research Agency, FOI, Sweden.
    Sjöqvist, L.
    Gustafsson, O.
    Experimental study of mid-IR laser beam wander close to a jet engine exhaust2006In: Proceedings of SPIE, the International Society for Optical Engineering, ISSN 0277-786X, E-ISSN 1996-756X, Vol. 6397Article in journal (Refereed)
    Abstract [en]

    An increasing interest in lasers placed on aircrafts for active countermeasures and active imaging is observed. There remain unsolved issues regarding the propagation effects close to the jet engine exhaust and the possibilities of compensating them with adaptive optics. Laser beam propagation experiments parallel to the exhaust of a downscaled jet engine test rig have been performed. The experiments were carried out with nanosecond laser pulses at 1.6 and 3.5 μm wavelength. The laser spots were projected on a screen and the centroid motion were imaged by cameras. Root mean square magnitudes of the beam wander between 50 and 150 μrad were observed for different engine conditions and geometries. The 3.5 μm system had a frame rate of 607 Hz and could partly resolve the time variation of the beam wander. A correlation time (50 %) of 3.5 ms was observed for the beam wander. Deflections of several hundred μrad due to the average gradients in temperature and pressure were also found when the engine was turned on. In addition to beam wander intensity scintillations has been studied.

  • 6.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sjöqvist, L
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Narrow linewidth 2 mu m optical parametric oscillation in periodically poled LiNbO3 with volume Bragg grating outcoupler2007In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 86, p. 497-501Article in journal (Refereed)
    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.

  • 7.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. Swedish Defence Research Agency, Linköping, Sweden.
    Sjöqvist, L.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tandem OPO systems for mid-infrared generation using quasi phase-matching and volume Bragg gratings2007In: Proceedings of SPIE - The International Society for Optical Engineering, SPIE - International Society for Optical Engineering, 2007, Vol. 6738, p. 73805-73805Conference paper (Refereed)
    Abstract [en]

    Efficient laser sources in the 3 - 5 μm wavelength range are needed for directed infrared countermeasures, but also have applications in remote sensing, medicine and spectroscopy. We present results and discuss the possibilities of a tandem optical parametric oscillator (OPO) scheme for converting the radiation from a 1.06 μm Nd3+-laser to the mid-infrared. Our setup uses type I quasi phase-matched (QPM) crystals in a near degenerate OPO to generate 2.13 μm radiation. The QPM crystal provides higher nonlinearity and longer interaction lengths, because walk-off is avoided, compared to conventional bulk crystals. This is an advantage especially in low pulse energy applications. To make the 2.13 μm radiation usable for pumping a second OPO a volume Bragg grating is used as a cavity mirror to limit the bandwidth, which in a conventional QPM OPO at degeneracy can be several hundred nanometers. The acceptance bandwidth for efficient OPO operation of a 14 mm long ZnGeP2 (ZGP) crystal is approximately 5 nm, which makes the need for bandwidth limiting clear. The majority of the signal energy from a periodically poled KTiOPO4 (PP KTP) OPO with a volume Bragg grating output coupler was found to be in a single longitudinal mode, whereas the idler bandwidth was measured to 19 GHz (FWHM). A volume Bragg grating resonant near 2124 nm was chosen so that the signal and idler were separated by 9 nm. This OPO output has been used as a pump source for a conventional ZGP OPO demonstrating efficient conversion and providing broadband tunable output in the mid-infrared.

  • 8.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sjöqvist, Lars
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Cavity length resonances in a nanosecond singly resonant optical parametric oscillator2010In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, no 10, p. 10742-10749Article in journal (Refereed)
    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.

  • 9.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Sjöqvist, Lars
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Mode spectrum of multi-longitudinal mode pumped near-degenerate OPOs with volume Bragg grating output couplers2009In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 17, no 20, p. 17582-17589Article in journal (Refereed)
    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.

  • 10.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. FOI - Swedish Defence Research Agency, Sweden.
    Sjöqvist, Lars
    FOI - Swedish Defence Research Agency, Sweden.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Narrow Bandwidth High Power IR OPOs with Volume Bragg Gratings2008Conference paper (Refereed)
  • 11.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics. FOI – Swedish Defense Research Agency, Sweden.
    Sjöqvist, Lars
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tandem optical parametric oscillator mid-infrared laser source2009Conference paper (Refereed)
  • 12.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Mid-infrared ZGP OPO pumped by near-degenerate narrowband type-I PPKTP parametric oscillator.2007In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 88, no 1, p. 37-41Article in journal (Refereed)
    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%.

  • 13.
    Henriksson, Markus
    et al.
    KTH, School of Engineering Sciences (SCI), Physics.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Physics.
    Mid-IR ZGP-OPO pumped by a Bragg grating line-narrowed PPKTP-OPO2006In: Conf. Lasers Electro-Opt. Quantum Electron. Laser Sci. Conf., CLEO/QELS, 2006Conference paper (Refereed)
    Abstract [en]

    Here we report on a tandem OPO consisting of a Type IPPKTP-OPO pumping a ZGP-OPO generating radiation in the mid-IR. The PPKTP-OPO uses a bulk Bragg grating to generate narrowband pump radiation at 2008 nm.

  • 14.
    Henriksson, Markus
    et al.
    FOI.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    ZGP Mid-infrared laser source pumped by nearly-degenerate PPKTP parametric oscillator2007In: Optics InfoBase Conference Papers, Optical Society of America, 2007Conference paper (Refereed)
  • 15. Henriksson, Markus
    et al.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Pasiskevicius, Valdas
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    ZnGeP2 parametric oscillator pumped by a linewidth-narrowed parametric 2 μm source2006In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 31, p. 1878-1880Article in journal (Refereed)
    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.

  • 16.
    Pasiskevicius, Valdas
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Tiihonen, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Jacobsson, Björn
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Henriksson, Markus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Hirohashi, Junji
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Canalias, Carlota
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Laurell, Fredrik
    KTH, School of Engineering Sciences (SCI), Applied Physics, Laser Physics.
    Optical parametric oscillators and amplifiers with periodically poled ferroelectrics2006In: 2nd EPS-QEOD EUROPHOTON CONFERENCE, European Physical Society , 2006Conference paper (Refereed)
1 - 16 of 16
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