Radially polarized and pulsed output from passively Q-switched Nd:YAG ceramic microchip laser

For the first time, to the best of our knowledge, a radially polarized laser pulse was produced from a passively Q-switched Nd:YAG ceramic microchip laser with a piece of Cr4+:YAG crystal as the saturable absorber and multilayer concentric subwavelength grating as the polarization-selective output coupler. The averaged laser power reached 450 mW with a slope efficiency of 30.2%. The laser pulse had a maximum peak power of 759 W, a minimum pulse duration of 86 ns, and a 6.7 kHz repetition rate at 3.7 W absorbed pump power. The polarization degree of the radially polarized pulse was measured to be as high as 97.4%. Such a radially polarized laser pulse with a high peak power and a short width is important to numerous applications such as metal cutting. (C) 2008 Optical Society of America

Efficient excitations of radially and azimuthally polarized Nd 3+:YAG ceramic microchip laser by use of subwavelength multilayer concentric gratings composed of Nb2O5/SiO2

Cylindrical vector beams were produced from laser diode end-pumped Nd:YAG ceramic microchip laser by use of two types of subwavelength multilayer gratings as the axisymmetric-polarization output couplers respectively. The grating mirrors are composed of high- and low-refractive-index (Nb2O5/SiO2) layers alternately while each layer is shaped into triangle and concentric corrugations. For radially polarized laser output, the beam power reached 610mW with a polarization extinction ratio ( PER) of 61: 1 and a slope efficiency of 68.2%; for azimuthally polarized laser output, the beam power reached 626mW with a PER of 58: 1 and a slope efficiency of 47.6%. In both cases, the laser beams had near-diffraction limited quality. Small differences of beam power, PER and slope efficiency between radially and azimuthally polarized laser outputs were not critical, and could be minimized by further optimized adjustment to laser cavity and the reflectances of respective grating mirrors. The results manifested, by use of the photonic crystal gratings mirrors and end-pumped microchip laser configuration, CVBs can be generated efficiently with high modal symmetry and polarization purity. (C) 2008 Optical Society of America.

Intense infrared luminescence in transparent glass-ceramics containing beta-Ga2O3 : Ni2+ nanocrystals

Transparent glass-ceramics containing beta-Ga2O3:Ni2+ nanocrystals were synthesized and characterized by X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy. Intense broad-band luminescence centering at 1200 nm was observed when the sample was excited by a diode laser at 980 nm. The room-temperature fluorescent lifetime was 665 mu s, which is longer than the Ni2+-doped ZnAl2O4 and LiGa5O8 glass-ceramics and is also comparable to the Ni2+-doped LiGa5O8 single crystal. The intense infrared luminescence with long fluorescent lifetime may be ascribed to the high crystal field hold by Ni2+ and the moderate lattice phonon energy of beta-Ga2O3. The excellent optical properties of this novel material indicate that it might be a promising candidate for broad-band amplifiers and room-temperature tunable lasers.

Transparent Ni2+-doped lithium-alumino-silicate glass-ceramics for broadband near-infrared light source

Broadband infrared luminescence centred at around 1300 nm with full-width at half maximum of about 342 nm was observed from transparent Ni2+-doped lithium-alumino-silicate glass-ceramics embedded with beta-eucryptite crystallines. The room temperature fluorescent lifetime was 98 mu s. The transparent glass-ceramics may have potential applications in a widely tunable laser and a super-broadband optical amplifier for optical communications.

Bismuth-doped zinc aluminosilicate glasses and glass-ceramics with ultra-broadband infrared luminescence

Broadband infrared luminescence covering the optical telecommunication wavelength region of 0, E and S bands was observed from bismuth-doped zinc aluminosilicate glasses and glass-ceramics. The spectroscopic properties of the glasses and glass-ceramics depend on the thermal-treatment history. With the appearance of gahnite (ZnAl2O4) crystalline phase, the fluorescent peak moves to longer wavelength, but the fluorescent intensity decreases. The similar to 1300 nm fluorescence with a FWHM larger than 250 nm and a lifetime longer than 600 mu s possesses these optical materials with potential applications in laser devices and broadband amplifiers. The broad infrared luminescence from the bismuth-doped zinc aluminosilicate glasses and glass-ceramics might be from BiO or bismuth clusters rather than from Bi5+ and Bi3+. (c) 2005 Elsevier B.V. All rights reserved.

Enhanced luminescence from transparent Ni2+-doped MgO-Al2O3-SiO2 glass ceramics by Ga2O3 addition

Transparent Ni2+-doped MgO-Al2O3-SiO2 glass ceramics without and with Ga2O3 were synthetized. The precipitation of spinel nanocrystals, which was identified as solid solutions in the glass ceramics, could be favored by Ga2O3 addition and their sizes were about 7.6 nm in diameter. The luminescent intensity of the Ni2+-doped glass ceramics was largely enhanced by Ga2O3 addition which could mainly be caused by increasing of Ni2+ in the octahedral sites and the reduction of the mean frequency of phonon density of states in the spinel nanocrystals of solid solutions. The full width at half maximum (FWHM) of emissions for the glass ceramics with different Ga2O3 content was all more than 200 nm. The emission lifetime increased with the Ga2O3 content and the longest lifetime is about 250 mu s. The Ni2+-doped transparent glass ceramics with Ga2O3 addition have potential application as broadband optical amplifier and laser materials. (C) 2007 Elsevier Ltd. All rights reserved.

Diode-pumped passively q-switched Nd : YAG ceramic laser with a Cr4+: YAG crystal-satiable absorber

Transparent polycrystalline Nd:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2O3,Y2O3, and Nd2O3 powders. The powders were mixed in ethanol and doped with 0.5 wt% tetraethoxysilane, dried, and pressed. Pressed samples were sintered at 1750 degrees C in vacuum. Transparent fully dense samples with average grain sizes of 10 mu m were obtained. The 1 at.% Nd:YAG ceramic was used to research passively Q-switched laser output with a Cr4+:YAG crystal as a saturable absorber. An average output power of 94 mW with a pulse width of 50 ns was obtained when the incident pump power was 750 mW. The slope efficiency was 13%. The pulse energy is 5 mu J, and the peak power is about 100 W.

Diode-pumped Yb : YAG ceramic laser

Transparent polycrystalline Yb:YAG ceramics were fabricated by solid-state reactive sintering a mixture of commercial Al2O3, Y2O3, and Yb2O3 powders. The powders were mixed in ethanol and doped with 0.5 wt% tetraethoxysilane, dried, and pressed. Pressed samples were sintered at 1730 degrees C in vacuum. Transparent fully dense samples with grain sizes of several micrometers were obtained. The phase from 1500 degrees to 1700 degrees C was important for the grain growth, in which the grains grew quickly and a mass of pores were eliminated from the body of the sample. Annealing was an important step to remove the vacancies of oxygen and transform Yb2+ to Yb3+. The 1 at.% Yb:YAG ceramic sample was pumped by a diode laser to study the laser properties. The maximum output power of 1.02 W was obtained with a slope efficiency of 25% at 1030 nm. The size of the lasering sample was 4 mm x 4 mm x 3 mm.

Investigation of the spectroscopic properties of (Y0.92-xLa0.08Ndx)(2)O-3 transparent ceramics

The spectroscopic properties of (Y0.92-xLa0.08Ndx)(2)O-3 transparent ceramics were investigated. According to three intensity parameters (Omega(2),Omega(4),Omega(6)) fitted by the Judd-Ofelt theory, the spectroscopic quality parameter (X-Nd), branching ratio (beta(J,J')), and quantum efficiency (eta) of Nd3+ were determined. It was found that X-Nd of the host, owing to the additive La2O3, was decreased from 1.6 to 0.46; thus beta(J,11/2) was increased from 46% to 56.82%. A figure of merit of the specimens was discussed and compared with Nd:YAG transparent ceramic. (c) 2007 Optical Society of America.

Fabrication and spectral properties of Nd3+-doped yttrium lanthanum oxide transparent ceramics

Transparent 1 at% Nd3+:Y1.9La0.1O3 ceramics were fabricated with nanopowders prepared by carbonate coprecipitation method. The powder compacts were sintered in H-2 atmosphere at 1550 degrees C for 30 h. The Nd3+:Y1.9La0.1O3 ceramics display uniform grains of about 50 mu m and high transparency. The highest transmittance of the ceramics reaches 67%. The strongest absorption peak is in the wavelength of 820 nm with absorption cross section of 2.48 x 10(-20) cm(2). The absorption is still high at LD wavelength 806 nm with absorption cross section of 1.78 x 10(-20) cm(2) and broad full width at half maximum (FWHM) of about 6.3 nm. The strongest emission peak was centered at 1078 nm with large stimulated emission cross section of 9.63 x 10(-20) cm(2) and broad FWHM of about 7.8 nm. The broad absorption and emission bandwidth of Nd3+:y(1.9)La(0.1)O(3) transparent ceramics are favorable to achieve the miniaturized LD pumping apparatus and ultrashort modelocked pulse laser output, respectively. (c) 2007 Elsevier B.V. All rights reserved.

Multi-color long-lasting phosphorescence in Mn2+-doped ZnO-B2O3-SiO2 glass-ceramics

Multi-color LLP phenomenon was observed in Mn2+-doped ZnO-B2O3-SiO2 glassceramics after the irradiation of a UV lamp at room temperature. Transparent ZnO-B2O3-SiO2 glass emitted reddish LLP while opaque glass-ceramics prepared by the glass sample after heat treatment emitted yellowish or greenish LLP. The change of the phosphorescence is due to the alteration of co-ordination state of Mn2+. The phosphorescence of the samples was seen in the dark with naked eyes even 12 h after the irradiation with a UV lamp (lambda(max) = 254 nm) for 30 min. Based on the approximative t(-1) decay law of the phosphorescence, we suggest that the LLP is attributed to the thermally assisted electron-hole recombination.

Numerical Analysis of a Dual Polarization Mode-Locked Laser with a Quarter Wave Plate

Dynamical behaviors and frequency characteristics of an active mode-locked laser with a quarter wave plate (QWP) are numerically studied by using a set pf vectorial laser equation. Like a polarization self-modulated laser, a frequency shift of half the cavity mode spacing exists between the eigen-modes in the two neutral axes of QWP. Within the active medium, the symmetric gain and cavity structure maintain the pulse's circular polarization with left-hand and right-hand in turn for each round trip. Once the left-hand or right-hand circularly polarized pulse passes through QWP, its polarization is linear and the polarized direction is in one of the directions of i45o with respect to the neutral axes of QWP. The output components in the directions of i45" from the mirror close to QWP are all linearly polarized with a period of twice the round-trip time.

Polarization Self-Modulation Phenomenon in a Free Oscillated Nd: YAG Laser

Polarization self-modulation effect in a free oscillated Nd:YAG laser is investigated after a quarter wave plate is introduced independently in the two positions of the cavity. As described in the previous experiments, the intensity components in the orthogonal directions are modulated with a period of the round-trip time or twice. Different pulse shapes reveal that the seed field from the spontaneous emission is not uniform and seems to be stochastic for each pulse.

Surface amorphous and crystalline microstructure by alloying zirconium using Nd : YAG pulsed laser

A novel composite coating was synthesized by laser alloying of zirconium nanoparticles on an austenite stainless steel surface using a pulsed Nd:YAG laser. The coating contained duplex microstructures comprising an amorphous phase and an austenitic matrix. A discontinuous zirconium-containing region formed at a depth of 16 mum below the surface. The amorphous phase was present in the zirconium-rich region, with the composition of zirconium ranging from 7.8 to 14.5 at. pet. The formation of the amorphous phase was attributed to the zirconium addition. The hardness, corrosion, and wear-corrosion resistance of the irradiated coating were evidently enhanced compared to those of the stainless steel.