Six-μm laser generation at room temperature was achieved from ${\mathrm{Fe}}^{2+}$-doped ${\mathrm{Cd}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$ solid-solution active media for the first time, to the best of our knowledge. Laser properties of ${\mathrm{Fe}}^{2+}\text{:}{\mathrm{Cd}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$ crystals with various concentrations of manganese Mn ($x=0.1$, 0.52, 0.56, 0.68, and 0.76) were investigated. The increase of Mn content in these crystals was shown to result in an almost similar long-wavelength shift of absorption, fluorescence, and laser output spectra of about $\sim 60\mathrm{nm}$ per each 10% of Mn. Laser generation was achieved in all crystals with maximum output energies up to 30 μJ (for $x=0.52$). The laser central oscillation wavelength is significantly influenced by Mn concentration and varies in the range from 5400 nm up to 6000 nm.

Comparative investigation of characteristics of spontaneous and stimulated Raman scattering (SRS) in different alkali-earth tungstate and molybdate crystals at both high and low frequency anionic group vibrations is presented. It has been found that, among these crystals, the SrMoO₄ and SrWO₄ crystals are the most perspective for SRS generation on both stretching and bending modes of internal anionic group vibrations with the strongest SRS pulse shortening under synchronous laser pumping because of not only highly intense stretching mode Raman line for efficient primary extra cavity long-shifted SRS conversion but also the widest bending mode Raman line for the strongest SRS pulse shortening down to the inverse width of the widest Raman line (~1 ps) at secondary intracavity short-shifted SRS conversion. The strongest 26-fold pump pulse shortening down to 1.4 ps at the Stokes component with the combined Raman shift in the synchronously pumped extra cavity SrMoO₄ and SrWO₄ Raman lasers has been demonstrated. It was found that synchronously pumped cascade SRS with combined Raman shift is more efficient in the SrWO₄ crystal because the bending mode Raman line is more intense relative to the stretching mode Raman line than that in SrMoO₄.

This paper presents the design and performance measurement results of a prototype time-to-digital converter (TDC) implemented using commercially available components. The TDC is based on an interpolation principle. In this principle, the time interval is first roughly digitized by a coarse counter driven by a high-stability reference clock, and the fractions between the clock periods are measured by two high-resolution interpolators based on the time-to-amplitude conversion method. This principle ensures theoretically unlimited measurement range with fine time resolution. The TDC achieves 2.1-ps rms time interval measurement precision with a resolution of 0.17 ps and the maximum measurement rate of 200 Hz. The estimated single-channel precision is 1.5-ps rms. A unique circuit structure was developed to allow individual channel calibration after each event. During the calibration, a value corresponding to one reference clock period is obtained. This gives the TDC an outstanding long-term stability of 110 fs peak-peak and a long-term drift of 0.2 fs/h over a 24-h interval. The calibration also helps to obtain a high temperature stability of 0.2 ps/°C. The power consumption is 10 W. The circuit structure allows for programmable customization of the TDC to satisfy many potential applications in time-of-flight systems, such as laser range finding or event counting.

Comparative investigation of stimulated Raman scattering (SRS) characteristics in the YVO₄, GdVO₄, and Ca₃(VO₄)₂ orthovanadate crystals at both low and high frequency anionic group vibrations is presented. It was found that GdVO₄ is the most perspective for SRS generation on both the ν₁ stretching and ν₂ bending modes of internal anionic group vibrations with the strongest SRS pulse shortening under synchronous picosecond pumping. It is as a result of GdVO₄‘s widest linewidth (17cm⁻¹) of the homogeneously broadened scheelite-type component of the bending ν₂ Raman line that led to the strongest SRS pulse shortening down to the dephasing time of the widest (scheelite-type) Raman mode at the secondary intracavity short-shifted SRS conversion. It allowed us to achieve SRS pulses with sub-picosecond duration under tens-of-picoseconds pumping due to the strongest 42-fold pulse shortening. Using the Ca₃(VO₄)₂ crystal with essentially wider Raman lines (~50cm⁻¹) did not allow us to generate SRS pulses shorter than 1 ps. It can be explained by inhomogeneous broadening of the Raman lines in Ca₃(VO₄)₂ because of its structural disordering. Using the measured SRS pulse duration, the homogeneous broadening of the inhomogeneously broadened bending Raman line of Ca₃(VO₄)₂ was estimated to be ~9cm⁻¹. Among the orthovanadate crystals, the YVO₄ crystal with the highest Raman gain and with homogeneously broadened Raman lines allowed us to realize the most efficient SRS lasing and SRS pulse shortening truly down to inverse half-width of the bending Raman line.

Comparative characteristics of spontaneous and stimulated Raman scattering in Pb(MoO₄)_1−x(WO₄)_x single crystals (x = 0, 0.5, 0.8, and 1.0) including both the high (ν₁) and low (ν₂) frequency internal anionic group vibrations have been investigated. It was found that among these crystals, Pb(MoO₄)_0.2(WO₄)_0.8 is the most suitable for multi-wavelength Raman laser in several Raman modes simultaneously. This is caused by the optimal relative Mo/W content corresponding to the most efficient coherent combination of the (MoO₄)²⁻ and (WO₄)²⁻ vibrations enhancing the output radiation characteristics of the synchronously pumped Pb(MoO₄)_0.2(WO₄)_0.8 Raman laser. Oscillation of up to twelve, closely spaced SRS components in a range of 1128–1360 nm and the strongest pulse shortening down to 1.16 ps in comparison with not only PbMoO₄ and PbWO₄ but also with all the earlier investigated nominally pure scheelite-like tungstate and molybdate crystals has been achieved.

Two different mid-infrared (mid-IR) solid-state crystalline laser active media of Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mn${}_{\mathrm{x}}$Se and Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mg${}_{\mathrm{x}}$Se 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 $\mathsf{\mu }$m, Q-switched Er:YAG laser at 2.94 $\mathsf{\mu }$m, and the gain-switched Fe:ZnSe laser operated at a liquid nitrogen temperature of 78 K at ∼4.05 $\mathsf{\mu }$m. 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 Cr${}^{2+}$ or by Fe${}^{2+}$ ions under direct excitation or indirectly by the Cr${}^{2+}$→ Fe${}^{2+}$ energy transfer mechanism. Laser generation of Fe${}^{2+}$ ions in Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mn${}_{\mathrm{x}}$Se and Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mg${}_{\mathrm{x}}$Se (x ≈ 0.3) crystals at the wavelengths of ∼4.4 and ∼4.8 $\mathsf{\mu }$m at a temperature of 78 K was achieved, respectively. The excitation of Fe${}^{2+}$ ions in both samples by direct 2.94 $\mathsf{\mu }$m as well as ∼4.05 $\mathsf{\mu }$m radiation or indirectly via the Cr${}^{2+}$→ Fe${}^{2+}$ ions’ energy transfer-based mechanism by 1.73 $\mathsf{\mu }$m 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 $\mathsf{\mu }$m) based on A${}^{\mathrm{II}}$B${}^{\mathrm{VI}}$ matrices was presented.