Synchronously Intracavity-Pumped Picosecond Optical Parametric Oscillators for Sensors.

The research and development of laser systems for intracavity phase interferometry is described. These systems are based on an intracavity synchronously pumped optical parametric oscillator (OPO), enabling the generation of two trains of picosecond pulses inside a single cavity. In such a configuration, it is possible to measure the beat note frequency between two pulses and to very precisely determine the phase difference between them. The pump source is a diode-pumped passively mode-locked Nd:YVO4 laser. A periodically poled magnesium-doped lithium niobate crystal is used as the optical parametric oscillator crystal coupling the pump and the signal cavities. We designed a synchronously pumped OPO in a linear and ring cavity configuration allowing generation in a dual-pulse regime. By a mutual detuning of both cavity lengths, the quasi-synchronous regime of pumping was achieved and high harmonics of repetition rate frequencies were generated. Such a system can be useful for applications such as pump-probe spectroscopy or for testing telecommunication systems. We also realized the subharmonic OPO cavity as a source of two independent trains of picosecond pulses suitable for intracavity phase interferometry; we also measured the beat note signal.

Multiwavelength, picosecond, synchronously pumped, Pb(MoO4)0.2(WO4)0.8 Raman laser oscillating at 12 wavelengths in a range of 1128-1360 nm.

In this Letter, a mixed Pb(MoO4)0.2(WO4)0.8 as a new, to the best of our knowledge, active medium with optimized content for a synchronously pumped multiwavelength Raman laser with a combined frequency shift is presented. The unique structure of this crystal resulted in oscillations at 12 closely spaced output wavelengths in a spectral range from 1128 to 1360 nm. The strongest pulse shortening in comparison with nominally pure scheelite-like crystals has been achieved.

Highly efficient, high-energy, picosecond, synchronously pumped Raman laser at 1171 and 1217 nm based on PbMoO4 crystals with single and combined Raman shifts.

For the first time to our knowledge, the operation of a synchronously pumped ultrafast Raman laser that uses a PbMoO4 crystal as the active medium has been demonstrated. We achieved efficient Raman conversion in PbMoO4 from pumping 1063 nm into 1171 and 1217 nm, respectively, at single and combined frequency shifts on stretching and bending Raman modes. The output pulse energy (up to 160 nJ) and peak power (up to 11 kW) of the output picosecond radiation is the highest among all-solid-state synchronously pumped Raman lasers published to date. The strongest pulse shortening at 1217 nm down to 1.4 ps was obtained that is close to the bending mode dephasing time.

Long-pulse 4.4-4.6 µm laser oscillations of Fe2+ ions in a Zn1-xMnxSe (x = 0.3) crystal pumped by a 1940 nm Tm fiber laser through Cr2+ → Fe2+ energy transfer.

Millisecond-pulse laser operation of Fe2+ ions at 78 K is demonstrated in the Zn1-xMnxSe:Fe2+,Cr2+ (x=0.3) crystal under a Tm fiber 1940 nm laser pumping through a Cr2+→Fe2+ energy transfer process for the first time, to the best of our knowledge. The laser slope efficiency was 1% with respect to absorbed pumping energy at 1940 nm. The laser central wavelength shift from 4450 nm at 78 K up to 4510 nm at 110 K was observed. Tunability from 4350 up to 4670 nm at 78 K was achieved using an intracavity tuning element.

Highly efficient picosecond all-solid-state Raman laser at 1179 and 1227 nm on single and combined Raman lines in a BaWO4 crystal.

We present a highly efficient ring-cavity all-solid-state BaWO4 Raman laser generating at both the long-shift (ν1=925 cm-1) and short-shift (ν2=332 cm-1) Raman lines under external picosecond synchronous pumping at the wavelength of 1063 nm. Very high slope efficiencies and output pulse energies of 68.8% and 103 nJ at the ν1-shifted Stokes wavelength of 1179 nm, and 38.6% and 53 nJ at the (ν1+ν2)-shifted Stokes wavelength of 1227 nm have been achieved. Self-mode locking of the (ν1+ν2)-shifted Stokes field under intracavity pumping by the ν1-shifted Stokes field allowed to realize 12-fold shortening of the 1227 nm radiation pulse down to 3 ps close to the shorter dephasing time of the ν2 Raman line at the output pulse peak power 1.5 times higher than the pump peak power.

Thulium fiber pumped tunable Ho:CaF2 laser.

The paper reports the first room-temperature operation of the in-band pumped Ho:CaF2 laser. A set of Ho:CaF2 crystals varying in holmium concentrations (from 0.1 up to 2.5 mol. % of HoF2), synthesized using the Bridgeman technique, was used for lasing and related spectroscopy investigation. A pulsed 1.94 µm thulium fiber laser system was used for Ho:CaF2 longitudinal pumping. For 1.5 mol. % of Ho:CaF2, the maximal wavelength tunability (from 2073 to 2114 nm) and output energy (1.6 mJ at 2113 nm) were obtained for absorbed pumping energy 34 mJ. Without the tuning element, the slope efficiency up to 30% in respect to absorbed power was obtained using this sample.

Molecular phylogeny of Metanoeina net-winged beetles identifies Ochinoeus, a new genus from China and Laos (Coleoptera: Lycidae).

The molecular hypothesis on relationships of Metanoeina lineages is presented and results are compared with morphology. A new genus Ochinoeus is proposed for four East Palearctic and Oriental species. Ochinoeus is recovered as a sister lineage to Matsudanoeus Sklenarova et al., 2014 and differs from related genera in morphology of genitalia and incomplete secondary elytral costae. We show, that the structure of elytral costae, although highly homoplastic across Metriorrhynchini, can be used for identification of Ochinoeus. The geographic distribution of Metanoeina is limited to the eastern parts of the Palaearctic and Oriental regions. The reconstruction of ancestral ranges identifies continental Eastern Asia as the centre of generic diversity of Metanoeina and suggests the dispersal from continental Asia to the southern part of the Oriental region, i.e. to the Sundaland and Philippines. Among Metanoeina lineages, only Metanoeus Waterhouse, 1878 contains higher number of species. The following four species are described: Ochinoeus huaphanensis sp. nov., O. hainanensis sp. nov., O. habashanensis sp. nov., and O. xunyanbaensis sp. nov..