Alexander A. Kaminskii

Neodymium doped yttrium aluminum garnet (Y3Al5O12) nanocrystalline ceramics—a new generation of solid state laser and optical materials

We have developed and adequately characterized a new generation of solid-state laser and optical materials on the basis of highly transparent nanocrystalline yttrium aluminium garnet Y3Al5O12 (YAG) ceramics. We consider this new type of inorganic laser media as an illustration of selected results of the latest investigations of laser and spectroscopic parameters of nanocrystalline Nd3+:YAG ceramics. In particular, absorption, luminescence, stimulated Raman scattering properties, as well as highly efficient CW laser oscillation at wavelength of 1064 nm under laser-diode pumping were investigated. The results show that this new laser material is a very good alternative to Nd3+:YAG single crystals. In particular, in preliminary comparison laser experiments with both Nd3+:YAG ceramic and single-crystal rods, output powers of 88 W and 99 W were obtained corresponding to optical-to-optical efficiencies of 30% and 34% for ceramic and single crystal rods, respectively. A CW 1.46 kW high power Nd:YAG ceramic laser was developed. Quite recently, laser oscillation at ≈1.32 μm was also demonstrated.

Properties of Nd 3+ -doped and undoped tetragonal PbWO 4 ,NaY(WO 4 ) 2 , CaWO 4 , and undoped monoclinicZnWO 4 and CdWO 4 as laser-active and stimulated Ramanscattering-active crystals

Spectroscopic, laser, and chi((3)) nonlinear optical properties of tetragonal PbWO(4), NaY(WO(4))(2), CaWO(4), and monoclinic CdWO(4) and ZnWO(4) were investigated. Particular attention was paid to Nd(3+)-doped and undoped PbWO(4) and NaY(WO(4))(2) crystals. Their absorption and luminescence intensity characteristics, including the peak cross sections of induced transitions, were determined. Pulsed and continuous-wave lasing in the two 4F(3/2)-->4I(11/2) and 4F(3/2)-->4I(13/2) channels was excited. For these five tungstates, highly efficient (greater than 50%) multiple Stokes generation and anti-Stokes picosecond generation were achieved. All the observed scattered laser components were identified. These results were analyzed and compared with spectroscopic data from spontaneous Raman scattering. A new crystalline Raman laser based on PbWO(4) was developed for the chi((3)) conversion frequency of 1-microm pump radiation to the first Stokes emission with efficiency up to 40%. We classify all the tungstates as promising media for lasers and neodymium-doped crystals for self-stimulated Raman scattering lasers.

Tetragonal vanadates YVO4 and GdVO4 – new efficient χ(3)-materials for Raman lasers

Abstract Efficient room temperature multiple Stokes and anti-Stokes picosecond generation in tetragonal YVO4 and GdVO4 host crystals for lasing trivalent lanthanides (Ln3+) has been observed for the first time. All measured stimulated Raman scattering (SRS) wavelengths in the visible and near infrared are identified and attributed to the SRS-active vibration modes of these vanadates.

Highly efficient 2% Nd:yttrium aluminum garnet ceramic laser

A highly efficient diode-laser end-pumped polycrystalline 2% Nd:yttrium aluminum garnet (YAG) ceramics laser that is comparable in efficiency with Nd:YAG single crystal laser has been developed. With 883 mW pumping, 465-mW-cw laser output at 1064 nm has been obtained corresponding to an optical-to-optical efficiency of 52.7%. The laser threshold is only 30 mW with R=97% output coupler.

Nd3+:Y2O3 Ceramic Laser

We have demonstrated CW one-micron laser oscillation in new ceramic laser material on the base of cubic Nd3+:Y2O3. Slope efficiency of 32% was achieved on an uncoated 1.5 at.% Nd3+:Y2O3 ceramic plate with size of 14 ×2.7 mm under laser diode end-pumping.

Diode-pumped mode-locked Yb 3+ :Lu 2 O 3 ceramic laser

We report a diode-pumped passively mode-locked Yb(3+):Lu(2)O(3) ceramic laser by use of a semiconductor saturable absorber mirror. Almost transform-limited 357 fs pulses at the center wavelength of 1033.5 nm with a maximum average power of 352 mW are obtained. The efficiency against the absorbed pump power is as high as 32% by use of a laser-diode pumping and the repetition rate is 97 MHz. This is the first demonstration of a diode-pumped mode-locked Yb(3+):Lu(2)O(3) ceramic laser to our knowledge.

Spectroscopic and stimulated emission Characteristics of Nd/sup 3+/ in transparent YAG ceramics

Nd: YAG ceramic materials have been synthesized using vacuum sintering technique with the raw materials prepared by the nano-crystalline methods. The spectroscopic studies suggest overall improvement in absorption and emission and reduction in scattering loss. Judd-Ofelt analysis has been employed to compute the relevant spectroscopic and radiative parameters of the material. The SEM and TEM measurements reveal the excellent optical quality of the ceramic with low pore volume and narrow grain boundary. Fluorescence and Raman measurements reveal that the Nd/sup 3+/-doped YAG ceramic is almost equivalent to its single-crystal counterpart in its radiative and nonradiative properties. Individual Stark levels for /sup 2s+1/L/sub J/ manifolds are obtained from the absorption and fluorescence spectra and are analyzed to identify the stimulated emission channels possible in the Nd: YAG ceramic. Laser performance studies favor the use of high-concentration Nd: YAG ceramics in the design of an efficient microchip laser. With 4 at% Nd: YAG ceramic acting as a microchip laser, we obtained a slope efficiency of 40%. High-power laser experiments yield an optical-to-optical conversion efficiency of 30% for Nd (0.6 at%):YAG ceramic as compared to 34% for an Nd (0.6 at%):YAG single crystal. The oscillation experiments at 1.3 mm gives a slope efficiency of 35%. Optical gain measurements conducted in these materials also show values comparable to single crystal, supporting that these materials could be suitable substitutes to single crystals in solid-state laser applications.

Yb3+:Y2O3 Ceramics – a Novel Solid-State Laser Material

A new solid-state laser based on Yb3+-doped highly transparent nanocrystalline yttria (Y2O3) ceramics was developed. At room temperature and under a pump power of 2.63 W from a single InGaAs laser diode at ≈ 0.94 µm, a continuous-wave laser output of 0.47 W at 1.077 µm wavelength was obtained corresponding to a slope efficiency of about 32%. Some main spectroscopic properties of Yb3+:Y2O3 ceramics were also investigated.

Polarized Raman spectra of the oriented NaY(WO4)2 and KY(WO4)2 single crystals

Abstract Polarized Raman scattering spectra of the NaY(WO 4 ) 2 (NYW) single crystal have been measured. Its structure is described in the tetragonal space group isomorphic to CaWO 4 scheelite. The A g , B g and E g spectra were made and discussed in terms of factor group analysis. These spectra are compared to those of monoclinic KY(WO 4 ) 2 (KYW) single crystals whose structure differs from the other crystal. The NYW unit cell comprises of the isolated WO 4 tetrahedra whereas the KYW structure is built from the WO 6 octahedra joined by WO 2 W double bonds and WOW single bridges. The vibrational characteristics of the bridge bond systems are proposed. On this basis, the role of the vibronic transitions for the KYW crystal doped with Eu 3+ ions is discussed.

Highly efficient continuous-wave operation at 1030 and 1075 nm wavelengths of LD-pumped Yb3+:Y2O3 ceramic lasers

Room-temperature cw laser oscillations at 1030 and 1075 nm wavelengths were demonstrated for the TEM00 mode with Yb3+:Y2O3 ceramics by LD-pumping. A maximum extraction efficiency of 72% at 1075 nm lasing wavelengths and of 45% at 1030 nm lasing wavelengths were observed.