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| 2. |
- Liu, Yaqun, et al.
(författare)
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2 um type-II optical parametric oscillators in PPRKTP
- 2022
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Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group (formerly OSA).
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Konferensbidrag (refereegranskat)abstract
- The mid-infrared type-II PPRKTP optical parametric oscillators (OPO) operating in 2 um region were investigated using quasi-phase-matched structures with a range of periodicities. A design precisely targeting on/off greenhouse gas absorption lines was devised.
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| 3. |
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| 4. |
- Liu, Yaqun, et al.
(författare)
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Type-II PPRKTP optical parametric oscillators in the 2 μm spectral range
- 2022
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optica Publishing Group. - 0740-3224 .- 1520-8540. ; 39:12, s. A36-A43
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Tidskriftsartikel (refereegranskat)abstract
- We experimentally explored the design parameter space for periodically poled Rb : KTiOPO4 (PPRKTP) struc-tures in type-II optical parametric oscillators (OPOs) pumped at 1.064 mu m and operating in the 1.8-2.5 mu m range. This study identifies a set of Sellmeier expansions and thermooptic coefficients that can be used to accurately design the type-II PPRKTP structures in this spectral range. The performance of this OPO regime is investigated by employing different periodicities of PPRKTP, and the effective nonlinear coefficient is determined. Output at the mJ level with a bandwidth of better than 10 MHz is readily generated without optical damage. The temperature tuning rate of about 8 GHz/K of the central OPO frequency is substantially lower than in similar periodically poled lithium niobate devices and can be exploited for precise frequency tuning and easier thermal stabilization. The stimulated backward polariton scattering in the OPO cavities is also investigated and discussed.
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| 5. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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Multi-transversal mode pumping of Narrow-Bandwidth Backward wave Optical Parametric Oscillator
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A stable, narrow-bandwidth (274 MHz) backward wave optical parametric oscillator (BWOPO) generating mJ-level backward signal at 1885 nm and forward idler at 2495 nm is presented. The BWOPO was pumped by a single-longitudinal mode, Q-switched Nd:YAG high-energy laser at 1064 nm. We show that multi-transversal mode pumping leads to the spectral broadening of the BWOPO backward signal and the generation of nanosecond pulses 2.7 times above the Fourier transform limit. A smooth continuous tuning of the BWOPO frequency over 100 GHz was demonstrated and elucidated the substantial contribution of the thermal expansion to the overall tuning performance. The BWOPO signal was used as a seed for a single-stage PPRKTP optical parametric amplifier (OPA) to boost the narrowband signal and idler energies to 20 mJ. This combination of mJ-level BWOPO seed with a single-stage PPRKTP OPA comprises a simple concept that would benefit long-range DIAL applications in the near and mid-infrared regions.
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| 6. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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Multi-transversal mode pumping of narrow-bandwidth backward wave optical parametric oscillator
- 2023
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 31:15, s. 24320-24327
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Tidskriftsartikel (refereegranskat)abstract
- A stable, narrow-bandwidth (274 MHz) backward wave optical parametric oscillator (BWOPO) generating mJ-level backward signal at 1885nm and forward idler at 2495 nm is presented. The BWOPO was pumped by a single-longitudinal mode, Q-switched Nd:YAG high-energy laser at 1064 nm. We show that multi-transversal mode pumping leads to the spectral broadening of the BWOPO backward signal and the generation of nanosecond pulses 2.7 times above the Fourier transform limit. We demonstrate over 100 GHz continuous tuning of the parametric output by adjusting the temperature of the BWOPO crystal, showcasing the significant role of thermal expansion in tuning performance. The BWOPO signal was used as a seed for a single-stage PPRKTP optical parametric amplifier (OPA) to boost the narrowband signal and idler energies to 20 mJ. This combination of mJ-level BWOPO seed with a single-stage PPRKTP OPA comprises a simple concept that would benefit long-range differential absorption lidar (DIAL) in the near and mid-infrared regions.
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| 7. |
- Mølster, Kjell Martin, 1992-, et al.
(författare)
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Proton irradiation hardness of periodically poled Rb:KTP for spaceborne parametric frequency converters
- 2023
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Ingår i: Optical Materials Express. - : Optica Publishing Group. - 2159-3930 .- 2159-3930. ; 13:2, s. 436-446
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Tidskriftsartikel (refereegranskat)abstract
- Large aperture periodically-poled Rb:KTP crystals designed for optical parametric amplifiers in 2 µm LIDAR systems were radiation hardness tested by exposure of proton beams at 10 MeV and 60 MeV energies. An irradiation dose of 55 Gy was used to commensurate the crystals’ estimated exposure on board a mission in the low-Earth orbit. The irradiation effects were investigated by comparing optical transmission spectra and 2D effective nonlinearity mapping in a 2 µm OPO setup before and after irradiation. The results reveal that the periodically poled structure remained intact after irradiation, and the changes in the optical transmission and nonlinear properties were close to the measurement uncertainty. This investigation is essential for realizing efficient frequency converters for space applications, such as spaceborne active greenhouse gas monitoring LIDAR instruments or correlated photon-pair sources.
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| 8. |
- Barrett, Laura, et al.
(författare)
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High-contrast coercive field engineering for periodic poling of RbKTiOPO4 with Ba2+/K+ ion-exchange
- 2024
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Ingår i: Optics Express. - : Optica Publishing Group. - 1094-4087. ; 32:8, s. 14252-14260
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a new method of coercive field engineering for periodic poling of RbKTiOPO4 (RKTP). By ion exchanging RKTP in a molten salt containing 7 mol% Ba(NO3)2 and 93 mol% KNO3 we achieve more than an order of magnitude difference in polarization switching time between the exchanged and non-exchanged regions. This method is used to fabricate periodic gratings of 2.92 µm in 1 mm thick bulk RKTP for second harmonic generation at 779 nm with a normalized conversion efficiency of 2%/Wcm. We show that the poled domain structures are stable at 300 °C, and that there is no bulk refractive index modification associated with the periodic ion exchange.
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| 9. |
- Lee, Cherrie, 1992-
(författare)
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Assessment of Fabrication Techniques for Large Aperture Quasi Phase Matched Device in RKTP
- 2019
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Konferensbidrag (refereegranskat)abstract
- Since the first demonstration in 1993, the use of quasi-phase matching (QPM) technique has gained wide adoption in a multitude of applications, specifically in optical frequency conversion. QPM is most commonly implemented by periodically inverting the spontaneous polarization in ferroelectric crystals such as Rb-doped KTiOPO4 (RKTP) using electric field poling with periodic electrodes deposited by lithography techniques. For application in high energy optical parametric oscillator (OPO), QPM crystal with large aperture is desirable as this allow pumping with larger beams and thus, larger pulse energy can be obtained. However, fabricating periodically poled crystals with large aperture crystal is challenging as larger electric field is required for polarization switching and also, more difficult for the domain grating to propagate through the whole crystal thickness. Although poling in such thick crystal has been reported, the grating period of those crystals are beyond 30 µm. In this work, we attempt periodic poling in a 3mm thick RKTP crystal with poling periodicity of one order of magnitude smaller, 3.43 µm. Short-period domain like this is necessary for generation of short wavelengths down to 400 nm by frequency doubling.
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| 10. |
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