P. V. Prokoshin

Chromium-doped forsterite as a solid-state saturable absorber

Saturation of near-infrared absorption in Mg(2)SiO(4):Cr is observed, and the absorption cross section at 1.08 microm is estimated to be sigma(alpha) = (2.3 +/- 0.3) x 10(-18) cm(2). Q switching and passive mode locking of a Nd:YAG laser have been realized with a Mg(2)SiO(4):Cr saturable absorber.

Ultrafast dynamics of excited‐state absorption in V3+:YAG crystal

Picosecond differential absorption spectra measurements for V3+:YAG were performed and a schematic energy‐level diagram for tetrahedrally coordinated V3+ in YAG was deduced. The excited‐state absorption transitions from the 1E(1D) level were observed with peaks at 870 and 740 nm. The lifetime of the 1E(1D) excited state of the tetrahedral V3+ was found to be ∼130 ps. The ground‐state absorption band of the 3T1(3P) state was found to be at 590 nm.

Picosecond absorption spectroscopy of surface modified copper sulfide nanocrystals in polymeric film

The transient induced absorption and bleaching are examined in 10 nm size CuS nanocrystals embedded in polyvinylalcohol film. Partial surface oxidation of CuS nanocrystals produces a new near‐IR‐absorption band peaked at 1100 nm. The surface oxidized shell is supposed to form a midgap electron acceptor level and the near‐IR band relates to the electron transfer from the CuS valence band. The near‐IR band is bleached easily by 15 ps pump pulse from YAG:Nd laser (1.08 μm). The bleaching is accompanied by the induced absorption at the red side of CuS fundamental edge. Both signals induced decay quickly with the time constant 65–70 ps. The model is proposed where the electron–hole pair excited by near‐IR photon (electron in surface shell and hole inside CuS core) creates strong internal electric field, which induces the Stark red shift of CuS fundamental edge.

Nonlinear optical properties and laser applications of copper chalcogenide quantum dots in glass

Absorption saturation and picosecond pump-probe measurements on oxidized copper selenide quantum dots in sol-gel glasses were carried out. The bleaching relaxation time was found to be ∼300 ps. The saturation intensities were estimated to be 2.2 MW/cm 2 at 1.06 μm and 7 MW/cm 2 at 1.54 μm for Cu 2 Se and Cu 2+x Se-doped glasses, respectively. Passive Q-switching of 1.06, 1.34, and 1.54 μm solid state lasers with copper selenide-doped glasses as saturable absorbers were demonstrated.

Sol–gel silica glasses with nanoparticles of copper selenide: synthesis, optics and structure ☆

Abstract The silica glasses with copper selenide nanoparticles were fabricated by the sol–gel technique. The samples were characterized with transmission electron microscopy, Rutherford backscattering spectroscopy and optical absorption. The composition of nanoparticles is close to Cu 2 Se stoichiometry and can be varied under tuning of the preparation steps. These glasses exhibit the new features in visible and IR ranges.

Passively Q-switched Ho3+:Y3Al5O12 laser using a PbSe-doped glass

Saturable absorber Q switching of Ho3+:Y3Al5O12 laser at 2.1 μm using PbSe-doped phosphate glass was demonstrated. Q-switched pulses of 22 mJ in energy and 85 ns in duration were obtained.

Nonlinear optical properties of solgel-derived glasses doped with copper selenide nanoparticles

Transient differential absorption spectra of solgel glasses that contain copper selenide nanoparticles (NP’s) have been studied with a picosecond pump–probe technique. Oxidation of copper selenide NP’s results in the appearance of an additional absorption band peaked at ∼1 µm, which can be transiently bleached under laser excitation. Excited-state absorption related to mid-gap surface trap states was observed. The absorption recovery time was found to be ∼300 ps. The intensity-dependent transmission of oxidized copper selenide NP’s in solgel glass at 1.08 µm has been measured. Permanent laser-induced absorption changes in the glasses were studied with nanosecond pulses as a function of laser exposure. Passive Q switching of 1.06-µm Nd3+:Y3Al5O12, 1.34-µm Nd3+:YAlO3, and 1.54-µm Er3+: glass lasers has been realized with the glasses containing copper selenide NP’s used as saturable absorbers. Q-switched pulses with 100-ns (1.06 µm), 90-ns (1.34 µm), and 60-ns (1.54 µm) pulse widths were obtained.

Nonlinear transmission, ultrafast relaxation and three-photon absorption in reduced SrTiO3

The nonlinear transmission of single picosecond light pulses (λ=1.08 μm) in reduced SrTiO3 is investigated at high intensities. Saturation of free-carrier absorption with ultrashort relaxation time (10-11-10-10 s) is observed at 108-1010W/cm2, while at 1010-1011 W/cm2 three-photon absorption predominates. The free-carrier absorption cross section of σa=2.7x10-18cm2 and the three-photon absorption coefficient of γ=2x10-21cm3/W2 were determined.

Nonlinear optical properties and Q-switch performance of silica glasses doped with CuxSe nanoparticles

Glasses containing copper selenide nanoparticles (CuxSe) reveal an intense absorption band peaking at 1 μm (1.24 eV). The transient bleaching and intensity-dependent transmission of silica glasses with CuxSe nanoparticles of different stoichiometry are studied with 1.08 μm (1.15 eV) picosecond pulses. The bleaching relaxation time decreases with a shift in the absorption band maximum to the lower photon energies. The dependence of absorption on the input energy of the pulses is saturationlike at the beginning of the plateau at ~40 mJ/cm2. Passive Q-switching of the Nd3+:KGd(WO4)2 laser at 1.067 μm is realized with the CuxSe-doped glasses for different x.

EXCITED STATE ABSORPTION OF CR4+ ION IN FORSTERITE

Polarized differential absorption spectra of Cr4+-doped forsterite have been studied using a picosecond pump–probe technique. For pump beam and probe beam polarization parallel to the a axis, an excited state absorption in the 450–800 nm region is observed and assigned to the 3T2→3T1(3P) transition of Cr4+ ion. The lifetime of the 3T1(3F) state is estimated to be less than 15 ps.