K. V. Yumashev

Yb3+-doped YVO4 crystal for efficient Kerr-lens mode locking in solid-state lasers

We report the first demonstration, to our knowledge, of soft-aperture Kerr-lens mode locking in a diode-pumped femtosecond Yb3+:YVO4 laser. Near-transform-limited pulses as short as 61 fs are generated around a center wavelength of 1050 nm with an output power of 54 mW and a pulse repetition frequency of 104.5 MHz. This is, to our knowledge, the shortest pulse generated directly from an Yb laser having a crystalline host material. The femtosecond operation has a mode-locking threshold at an absorbed pump power of 190 mW. The nonlinear refractive indexes of the Yb3+:YVO4 crystal have been measured to be 19 x 10(-16) cm2/W and 15 x 10(-16) cm2/W for the sigma and pi polarizations, respectively, at 1080 nm.

Absorption and luminescence of tetrahedral Co2+ ion in MgAl2O4

Abstract Optical absorption, luminescence, saturation of absorption and lifetime measurements have been carried out on Co-doped MgAl 2 O 4 . The crystal field parameter Dq of 400 cm -1 and the Racah parameters B of 730 cm -1 and C of 3500 cm -1 are estimated for the tetrahedral Co 2+ ion. Luminescence bands observed in the visible at 660 nm and in the near infrared at 880 and 1270 nm are assigned to transitions from the 4 T 1 ( 4 P) level to the lower levels 4 A 2 ( 4 F), 4 T 2 ( 4 F), and 4 T 1 ( 4 F), respectively. Strong luminescence quenching due to nonradiative decay processes is observed. Saturation of Co 2+ absorption at 540 nm is measured and the absorption cross section is estimated to be (2.1 ± 0.2) × 10 -19 cm 2 .

Optical absorption and nonlinear transmission of tetrahedral V3+ (d2) in yttrium aluminum garnet

Abstract The saturation of the optical absorption in V 3+ : YAG crystal is investigated. The absorption cross section of tetrahedral V 3+ at 1.08 μm is estimated to be 8.2±2.5x10 -18 cm 2 . Q -switching and passive mode-locking for a number of solid state lasers with wavelengths at 747 nm, 780 nm, 1.06 μm and 1.34 μm have been obtained with a V 3+ :YAG saturable absorber.

Saturable absorber Co 2+ :MgAl 2 O 4 crystal for Q switching of 1.34-µm Nd 3+ :YAlO 3 and 1.54-µm Er 3+ :glass lasers

Saturable-absorber Q switching of a neodymium-doped YAlO3 laser at 1.34 µm and an erbium-doped glass laser at 1.54 µm with a Co2+:MgAl2O4 crystal was demonstrated. Q-switched 1.34-µm pulses of 19-mJ energy and 60-ns duration and Q-switched 1.54-µm pulses of 2.7-mJ energy and 75-ns width were obtained. The ground-state absorption cross sections of the Co2+:MgAl2O4 crystal were estimated to be (2.8 ± 0.4) × 10-19 and (3.5 ± 0.6) × 10-19 cm2 at 1.34 and 1.54 µm, respectively. The 4T1(4F) → 4A2 relaxation time of the Co2+ ion in the MgAl2O4 crystal was measured to be ∼350 ns.

Excited state absorption and passive Q-switch performance of Co2+ doped oxide crystals

Abstract Excited state absorption spectra (ESA) of the LiGa 5 O 8 (LGO), MgAl 2 O 4 (MALO) and LaMgAl 11 O 19 (LMA) crystals doped with the tetrahedral Co 2+ ion were studied under excitation at the 4 A 2 → 4 T 1 ( 4 F) transition. The ESA band was observed near 710–740 nm and assigned to the 4 T 2 → 4 T 1 ( 4 P) transition of the Co 2+ ion. The lifetime of the 4 T 2 level of Co 2+ ion at room temperature was estimated to be 130–350 ns depending on the crystal host. Absorption saturation measurements were performed and ground state and excited state absorption cross sections were estimated at the wavelengths of 1.34 and 1.54 μm. The crystals studied were used to Q-switch flashlamp-pumped 1.34 μm Nd 3+ :YAlO 3 and 1.54 μm Er 3+ :glass lasers. Passive Q-switching of a diode pumped 1.35 μm Nd:KGd(WO 4 ) 2 laser was demonstrated using Co 2+ :MALO saturable absorber.

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.

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.

Co2+:LiGa5O8 saturable absorber passive Q switch for 1.34 μm Nd3+:YAlO3 and 1.54 μm Er3+:glass lasers

Passive Q switching of a Nd3+:YAlO3 laser at 1.34 μm and an Er3+: glass laser at 1.54 μm was demonstrated using a Co2+:LiGa5O8 crystal as a saturable absorber. Q-switched pulses at 1.34 μm of 13 mJ energy and 90 ns duration and at 1.54 μm of 8 mJ energy and 70 ns duration were obtained. The ground state absorption cross section of the Co2+:LiGa5O8 was estimated to be (2.6±0.4)×10−19 cm2 and (2.5±0.5)×10−19 cm2 at 1.34 and 1.54 μm, respectively. The 4T1(4F)→4A2 relaxation time of the Co2+ ion in the LiGa5O8 crystal was measured to be ∼130 ns.

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...

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.