A. M. Malyarevich

Cobalt-doped transparent glass ceramic as a saturable absorber Q switch for erbium:glass lasers

A new saturable absorber Q switch for 1.54-mum Er:glass lasers is presented. The saturable absorber is a transparent glass ceramic that contains magnesium-aluminum spinel nanocrystallites doped with tetrahedrally coordinated Co(2+) ions. We obtained Q-switched pulses of up to 5.5 mJ in energy and 80 ns in duration at 1.54 mum. The relaxation time of (4)A(2) ?(4)T(1)((4)F) transition bleaching was measured to be (450 ? 150) ns. Ground-state and excited-state absorption cross sections at 1.54-mum wavelength were estimated to be (3.2 ? 0.4) x 10(-19) cm(2) and (5.0 ? 0.6) x 10(-20) cm(2), respectively.

Semiconductor-doped glass saturable absorbers for near-infrared solid-state lasers

A survey of results on use of semiconductor-doped glass saturable absorbers for near-infrared passively mode-locked and Q-switched solid-state lasers is presented. Nanosized semiconductor particles (quantum dots) belong to quantum confined systems where motion of an electron and a hole is defined by the finite size of the nanoparticle. Dependence of the excitonic transition energy on the QDs size provides the possibility to tune the absorption of the glasses embedded with such particles to wavelength of specific light source. IV-VI semiconductor QDs (PbS, PbSe) are of interest for IR application due to their narrow band gap and large exciton Bohr radii. These allow for exciton absorption band at the wavelength through 1–3μm. Nonlinear optical properties of PbS, PbSe, and CuxSe nanoparticles embedded in glass matrices necessary for saturable absorber applications are analyzed. It is shown that these materials can be efficiently used for passive mode locking and Q switching of solid-state lasers based on Nd...

Glass doped with PbS quantum dots as a saturable absorber for 1-mu m neodymium lasers

Saturable-absorber mode locking and Q switching of neodymium-doped lasers at 1.06 µm with a PbS-doped glass were demonstrated. Q-switched pulses of 0.3 µJ in energy and 15 ns in duration from a cw diode-pumped Nd3+:KGd(WO4)2 laser and ultrashort pulses of 18 µJ in energy and 70 ps in duration from a Nd3+:Y3Al5O12 laser were obtained. The saturation intensity of the PbS-doped glass (with an average semiconductor crystallite radius of 1.7 nm) was estimated to be 2.3 MW/cm2 at 1.06 µm. The bleaching relaxation time was measured to be 23 ps.

Nonlinear optical properties of CuxS and CuInS2 nanoparticles in sol–gel glasses

Silica glasses with ultrafine CuxS and CuInS2 particles (average radius of 5±3 nm) were fabricated by means of a sol–gel technique. Linear and differential absorption spectra were studied. The glasses reveal absorption peaks in the 600–700 nm range associated with the first excitonic resonance in the quantum confined particles. Laser excitation by 540 nm pulses leads to the induced absorption effect in the 480–980 nm spectral range. The relaxation of the induced absorption has a time constant equal to about 500 ps for CuS-doped glasses and a biexponential type (with τ1≈30 ps and τ2>1 ns) for CuInS2-doped ones.

Linear and nonlinear optical properties of cobalt-doped zinc aluminum glass ceramics

Optical properties of cobalt-doped zinc aluminosilicate transparent glass ceramics in the visible – near-infrared (IR) spectral range have been studied. It was shown that the absorption and luminescence properties of these glass ceramics are defined mainly by tetrahedrally coordinated Co2+ ions located in ZnAl2O4 gahnite nanocrystals formed in the glass ceramic matrix. The luminescence in the visible and near IR was assigned to the transitions from the 4T1(4P) to the 4A2 and 4T2 energy levels of tetrahedrally coordinated Co2+ ion. Absorption saturation and bleaching relaxation under excitation of the 4A2→4T1(4F) transition were studied. Luminescence decay and bleaching relaxation times lie in the ranges 25–200 and 500–800 ns, respectively, depending on the Co concentration. The value of the ground-state absorption cross section of tetrahedrally coordinated Co2+ ions in zinc aluminosilicate transparent glass ceramics was estimated to be 2.0×10−19 cm2 at the wavelength of 1.54 μm.

Magnesium- and zinc-aluminosilicate cobalt-doped glass ceramics as saturable absorbers for diode-pumped 1.3-μm laser

Q switching of a diode-pumped Nd3+:KGd(WO4)2 laser at 1.35 microm by use of cobalt-doped magnesium- and zinc-aluminosilicate glass ceramics as saturable absorbers is demonstrated. Q-switching efficiency up to 40% has been obtained. Ground-state absorption cross sections for Co2+ ions at the wavelengths of 1.35 and 1.54 microm are estimated to be (3.5-4.0) x 10(-19) cm2. Bleaching relaxation times under the excitation of the 4A2 --> 4T1(4F) transition of tetrahedrally coordinated Co2+ ions are of 280 +/- 50 ns and 700 +/- 80 ns for magnesium- and zinc-aluminosilicate glass ceramics, respectively.

Passive mode locking of 2.09 μm Cr,Tm,Ho:Y 3 Sc 2 Al 3 O 12 laser using PbS quantum-dot-doped glass

Passive Q-switched mode locking of a 2.09 microm flashlamp-pumped Cr(3+),Tm(3+),Ho(3+):Y(3)Sc(2)Al(3)O(12) laser by use of a phosphate glass doped with PbS quantum dots of 5 nm in radius was demonstrated. Mode-locked pulses of 290 ps in duration and up to 0.5 mJ in energy were registered.

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.

Nanosized glass-ceramics doped with transition metal ions: nonlinear spectroscopy and possible laser applications

Absorption, luminescence and saturation of absorption for cobalt-doped glass-ceramics were studied. Characteristic times of 44 4 21 luminescence decay of T ( P)→ A transition for tetrahedrally coordinated Co ions in lithium-, zinc-, magnesium- and magnesium- 12 44 4 gallium-aluminosilicate glass-ceramics were evaluated to be in tens of ns time scale. Kinetics of bleaching relaxation of A → T(F ) 21 21 transition for tetrahedrally coordinated Co ions in magnesium-aluminosilicate glass-ceramics was found to be 4506150 and 120640 21 ns for 0.1 and 0.3 wt% cobalt concentration, respectively. Ground-state absorption cross-section for Co ions at 1.54 mm was estimated 219 2 to be |3310 cm . Passively Q-switched pulses from Er:glass laser of 6 mJ in energy and 80 ns in duration using the Co-doped magnesium-aluminosilicate glass-ceramics sample as saturable absorber were demonstrated.  2002 Elsevier Science B.V. All rights reserved.

Formation and Passive Q-Switch Performance of Glass-Ceramics Containing Co2+-Doped Spinel Nanocrystals

Compositions and heat treatment conditions were determined at which absorption and luminescence properties of aluminosilicate transparent glass-ceramics are defined mainly by tetrahedrally coordinated Co2+ ions located in spinel nanocrystals. Optical properties of cobaltdoped aluminosilicate transparent glass-ceramics have been studied in visible – near infrared (IR) spectral range. It was demonstrated that the concentration of tetrahedrally coordinated Co2+ ions in the spinel nanocrystals is determined by the CoO content in the initial glass and is independent of the heat-treatment schedule. Absorption saturation and bleaching relaxation under excitation of the 4A2→4T1(4F) transition of tetrahedrally coordinated Co2+ ions were studied. The value of groundstate and excited state absorption cross-sections of tetrahedrally coordinated Co2+ ions was estimated. Comparative study of output pulse parameters of Q-switched Er:glass laser using cobaltdoped glass-ceramics and Co2+:MgAl2O4 single crystal is presented.