Mid-Infrared Laser Generation of Zn1-xMnxSe and Zn1-xMgxSe (x ≈ 0.3) Single Crystals Co-Doped by Cr2+ and Fe2+ Ions-Comparison of Different Excitation Wavelengths.

Two different mid-infrared (mid-IR) solid-state crystalline laser active media of Cr2+, Fe2+:Zn1-xMnxSe and Cr2+, Fe2+:Zn1-xMgxSe with similar amounts of manganese or magnesium ions of x ≈ 0.3 were investigated at cryogenic temperatures for three different excitation wavelengths: Q-switched Er:YLF laser at the wavelength of 1.73 µm, Q-switched Er:YAG laser at 2.94 µm, and the gain-switched Fe:ZnSe laser operated at a liquid nitrogen temperature of 78 K at ∼4.05 µm. The temperature dependence of spectral and laser characteristics was measured. Depending on the excitation wavelength and the selected output coupler, both laser systems were able to generate radiation by Cr2+ or by Fe2+ ions under direct excitation or indirectly by the Cr2+→ Fe2+ energy transfer mechanism. Laser generation of Fe2+ ions in Cr2+, Fe2+:Zn1-xMnxSe and Cr2+, Fe2+:Zn1-xMgxSe (x ≈ 0.3) crystals at the wavelengths of ∼4.4 and ∼4.8 µm at a temperature of 78 K was achieved, respectively. The excitation of Fe2+ ions in both samples by direct 2.94 µm as well as ∼4.05 µm radiation or indirectly via the Cr2+→ Fe2+ ions' energy transfer-based mechanism by 1.73 µm radiation was demonstrated. Based on the obtained results, the possibility of developing novel coherent laser systems in mid-IR regions (∼2.3-2.5 and ∼4.4-4.9 µm) based on AIIBVI matrices was presented.

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.

Influence of the pumping wavelength on laser properties of Fe2+ ions in ZnSe crystal.

ZnSe:Fe2+ active laser crystal properties at different excitation wavelengths (2.94 and 4.1 µm) were investigated, and noticeable variations of the fluorescence spectra shape and their maxima positions, as well as changes in decay times, were observed. A stepwise shift of the laser oscillation wavelength from 4.7 µm at 2.94 µm pumping to 4.95 µm at 4.1 µm pumping was achieved at room temperature.

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.