Influence of addition of B_2O_3 on properties of Yb^(3+)-doped phosphate laser glass

The three host glasses doped with Yb 3+ were prepared by means of conventional melt quenching technology, and the influence on physical and spectral properties of phosphate glass due to addition of B2O3 was investigated and compared with silicate glass. The results show that due to the existence of OH- impurities which induce the non-radiative route, the fluorescence lifetime of phosphate glass is shorter, so silicate glass has better spectral properties than phosphate glass. Silicate glass has more excellent thermal-mechanical properties than phosphate glass, but with the addition of B2O3, thermal-mechanical properties of phosphate glass are improved greatly without fluorescence quenching effect, and this kind of borophosphate glass will be the candidate to be used in high average power solid state laser.

Investigation on Structures and Properties of Yb^(3+)-Doped Laser Glasses

The Yb3^＋ -doped silicate, phosphate and borophosphate laser glasses were prepared by means of conventional melt quenching technology. The physical and spectral properties of the glasses were investigated. The results show that, due to the existence of OH^-, the fluorescence lifetime of phosphate glass is shorter than that of silicate glass, so silicate glass has better spectral properties than phosphate glass. Silicate glass has better mechanical and thermal properties than phosphate glass, but with the addition of B2O3, mechanical and thermal properties of phosphate glass are improved greatly without fluorescence quenching effect. This kind of borophosphate glass can be used in high average power solid state lasers.

Effect of copper impurity on the optical loss and Nd^(3+) nonradiative energy loss of Nd-doped phosphate laser glass

N31-type phosphate laser glasses doped with different concentrations of Cu were prepared. Their optical loss coefficient at 1053 nm wavelength and nonradiative transition rate from the Nd3＋ 4F3/2 state were determined and analyzed in detail. The optical loss coefficient per unit of Cu2＋ （cm–1/ppmw） and the fluorescence decay rate （Hz/ppmw） caused by Cu2＋ and Nd3＋ interaction were 0.0024 and 7.9, respectively. Cu impurity affected both optical loss at 1053 nm and fluorescent emission of Nd3＋ 4F3/2 state seriously in N31 laser glass.

Monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped high-power laser glass

This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The thermal stress,interface bubbles and residual refiectivity,which are due to high-temperature casting and bonding during the monolithic edge-cladding process,are simulated and determined.The applied mould is optimized to a rectangular cavity mould,and the casting temperature is optimized to 1000℃.The resulting lower bubble density makes the mean residual refiectivity as low as 6.75×10^(-5),which is enough to suppress the amplified spontaneous emission generated in the Nd-glass disk,and the resulting maximum optical retardation is converged to 10.2–13.3 nm/cm,which is a favourable base for fine annealing to achieve the stress specification of less than or equal to 5 nm/cm.After fine annealing at the optimized 520℃,the maximum optical retardation is as low as 4.8 nm/cm,and the minimum transmitted wavefront peak-to-valley value is 0.222 wavelength(632.8 nm).An N31 elliptical disk with the size of 194 mm×102 mm×40 mm can be successfully cladded by the optimized monolithic edge-cladding process,whose edge-cladded disk with the size of 200 mm×108 mm×40 mm can achieve laser gain one-third higher than that of an N21-type disk of the same size.

A moisture-resistant antireflective coating by sol-gel process for neodymium-doped phosphate laser glass

Using methyl triethoxysilicane as precursor, a moisture-resistant coating for neodymium-doped laser glass was developed by the sol-gel process. Colloidal silica was added in coating solution as modifier. The refractive index of this coating varied from 1.31 to 1.42. A porous antireflective （AR） silica coating with the index of 1.27 was coated on the moisture-resistant coating surface. The two-layer coating possessed transmission up to 99.1% at wavelength of 966 nm, surface root-mean-square （RMS） roughaess of 1.245 am, and roughness of average （RA） of 0.961 am. In the case of laser of 1053-nm laser waveleilgth and 1-ns pulse duration, the damage threshold of the two-layer coatings was more than 15 J/cm^2.

Crystallization Behavior of Nd_2O_3 Doped Na_2O–CaO–SiO_2 Laser Glass-ceramics

For the desirable laser optical property, transition metals or rare-earths are always doped into parent glasses as active ions, and this doping will affect the crystallization of the precursor glasses inevitably. In this work, crystallization behavior of NaO-CaO-SiO2 system glasses doped with Nd2O3 was investigated. The crystallization kinetic parameters including the crystallization apparent activation energy （E） and the Avrami parameter （n） were also measured. The results show that the NaO-CaO-SiO2 system glassceramics with the NaxCa2Si3O9 crystal as primary phase can be highly crystalized as above 90%. The Nd2O3 doping has a significant influence on the crystallization apparent activation energy and the Avrami parameter, which affect the crystallization behavior and morphology of the transparent glass-ceramics of this system.

Optimization of spectroscopic properties of ytterbium-doped laser glasses

Four laser glasses with high emission cross sections are experimentally obtained. The laser performance parameters are determined from the spectroscopic parameters of these glasses and compared with those of developing laser glasses abroad. It is shown that Yb3+-doped telluorogermanate, Yb3+-doped niobosilicate glasses have the highest emission cross section and gain coefficient, the smallest minimum pumping intensity and saturation pumping intensity, and the lowest minimum fraction of excited ions. Yb3+-doped borate glass follows just behind them. These glasses have some spectroscopic advantages over laser glasses developed recently elsewhere. Yb3+-doped phosphate glass is comparable to phosphate laser glass which had high emission cross section and was developed recently by HOYA Corporation in Japan. The domestic glasses with optimum spectroscopic properties may be promising candidates for applications in high-average power and high-peak power solid state lasers, especially laser for the next generation laser nuclear fusion facility.

Large aperture N31 neodymium phosphate laser glass for use in a high power laser facility

Large aperture Nd:phosphate laser glass is a key optical element for an inertial confinement fusion(ICF) facility. N31,one type of neodymium doped phosphate glasses, was developed for high peak power laser facility applications in China. The composition and main properties of N31 glass are given, together with those of LHG-8, LG-770, and KGSS-0180 Nd:phosphate laser glasses, from Hoya and Schott, and from Russia. The technologies of pot melting, continuous melting, and edge cladding of large size N31 phosphate laser glass are briefly described. The small signal gain profiles of N31 glass slabs from both pot melting and continuous melting at various values of the pumping energy of the xenon lamp are presented. N31 glass is characterized by a stimulated emission cross section of 3.8 × 10-20cm2 at 1053 nm,an absorption coefficient of 0.10–0.15% cm-1at laser wavelength, small residual stress around the interface between the cladding glass and the laser glass, optical homogeneity of ～2 × 10-6in a 400 mm aperture, and laser damage threshold larger than 42 J/cm2 for a 3 ns pulse width at 1064 nm wavelength.

Research and development of new neodymium laser glasses

This work presents a brief introduction on three kinds of newly developed Nd^(3+)-doped laser glasses in Shanghai Institute of Optics and Fine Mechanics(SIOM), China. Two Nd^(3+)-doped phosphate glasses with lower thermal expansion coefficient and thermal shock resistance 4 times higher than that of N31 glass are developed for laser processing.Nd:Silicate and Nd:Aluminate glasses with peak emission wavelength at 1061 and 1065 nm, effective emission bandwidth of 34 and 50 nm, respectively, are developed for Exawatt-class laser system application. Fluorophosphate glasses with low nonlinear refractive index(n_2=0.6–0.86) and long fluorescence lifetime(430–510 μs) are investigated for the purpose of decreasing B integral in high-power laser system. The properties of all these glasses are presented and compared with those of commercial neodymium laser glasses.

Thermodynamic study on elimination of platinum inclusions in phosphate laser glasses for inertial confinement fusion applications

A new method to calculate the formation enthalpies and free energies of compounds based on standard electromotive force of cation,φ0, and free energies of formation, ΔG2980, or formation enthalpies, ΔH2980, of chloride was proposed. A linear relationship between φ0 and ΔG2980, φ0 and ΔH2980, and ΔG2980 and ΔH2980 was found respectively. The parameters used for thermodynamic calculation were calculated. The calculated values of the formation enthalpies and the free energies of formation of platinum compounds, such as Pt3（PO4）2 and Pt （PO3）2,were given for the first time. The mechanism of eliminating platinum inclusions in phosphate laser glass by POCI3 gas bubbling was interpreted from thermodynamic aspect.

Laser Welding of Zr_(41)Ti_(14)Cu_(12)Ni_(10)Be_(23) Bulk Metallic Glass and Zirconium Metal

The laser bonding technology between the Zr41 Ti14 Cu12 Ni10 Be23 bulk metallic glass and zirconium metal was investigated under welding parameters of 1.3 kW and 7 m/min. The welded bead, microstructure, and micro-hardness of the welded joint were examined by Keyence, transmission electron microscopy, scanning electron microscopy, and Vickers hardness, respectively. The experimental results showed that the Zr41 Ti14 Cu12 Ni10 Be2 bulk metallic glass and zirconium metal were successfully bonded together. The Zr41 Ti14 Cu12 Ni10 Be2 in the base material zone maintained amorphous structure, and the welding fusion zone kept the hardness as high as as-received BMG. Therefore, the laser welding technology can be used to achieve successful bonding of bulk metallic glasses and crystallization metal.

Effects of femtosecond laser ablation on the surface morphology and microstructure of a bulk TiCuPdZr glass alloy

The effects of femtosecond laser ablation on the surface characteristics and microstructure of a bulk TiCuPdZr glass alloy were investigated. The heat influence zone of femtosecond laser ablated with a laser energy of 100 μJ exhibits a ripple-like feather, while a porous structure appears on the surface of the specimen ablated by a 200 μJ femtosecond laser. The contents of Ti, Zr, and Pd on the ablated surface decrease and that of Cu increases with increasing laser energy. The crystallization process occurs on the glass alloy specimens during femtosecond laser ablation, and the crystallinity of a 100 μJ femtosecond laser-ablated specimen is greater than that of a 200 μJ femtosecond laser-ablated one.

Bubble Generation in Germanate Glass Induced by Femtosecond Laser

We report the observation of bubble generation and migration in a germanate g/ass during irradiation by a femtosecond laser of high repetition rate. Bubbles are formed around the focal area of the laser beam, and their movement indicates the presence of thermal gravity convection in the glass melt, which is beyond the existing theoretical model about temperature l^eld of focal area. Inside the bubbles, oxygen molecules are observed by the con focal Raman micro-spectroscopy. The generation of molecular oxygen and bubbles is explained in terms of the spatial separation of Ge and 0 ions and micro-explosion inside the glass melt.

Generalized model for laser-induced surface structure in metallic glass

The details of the special three-dimensional micro-nano scale ripples with a period of hundreds of microns on the surfaces of a Zr-based and a La-based metallic glass irradiated separately by single laser pulse are investigated.We use the small-amplitude capillary wave theory to unveil the ripple formation mechanism through considering each of the molten metallic glasses as an incompressible viscous fluid.A generalized model is presented to describe the special morphology,which fits the experimental result well.It is also revealed that the viscosity brings about the biggest effect on the monotone decreasing nature of the amplitude and the wavelength of the surface ripples.The greater the viscosity is,the shorter the amplitude and the wavelength are.

Transmission Properties of a New Glass Ceramic and Doped with Co^(2+) as Saturable Absorber for 1.54 μm Er Glass Short Pulse Laser

The preparation and characteristics of a new transparent glass ceramic were described. Crystal phase particles with nanometer size were successfully precipitated in glass matrix, which was confirmed to be one of indium aluminum zinc oxide compounds （InxAlrZn2O）. The presence of aluminum （A1） and indium （In） impurities in the zinc oxides （ZnO） crystal lattice leads to some changes of the carrier concentration in the material and then promote the sharply changes of transmission spectra in IR range wavelength. And subsequently, the IR cut-off edge blue shifted from 5.5 pm in base glass to 3 μm in transparent glass ceramic sample. Furthermore, passive Q switched 1.54 ktm Er glass laser pulses with pulse energy of 10 mJ and pulse width of 800 ns were successfully obtained by using the cobalt doped transparent glass ceramic as a saturable absorber.

Femtosecond Laser Induced Precipitation of LiNbO_3 Crystals in Sm^(3+)-doped Li_2O-Nb_2O_5-SiO_2 Glass

A femtosecond laser with 800 nm, 250 kHz and 150 fs was used to irradiate Sm^3＋-doped Li2O- Nb2O5-SiO2 glass. At the initial stage of the laser irradiation, a white emission was observed near the focal point of the laser beam inside the glass. After 20 second irradiation, a red and blue emission began to emerge. From the micro-Raman spectra, we found that the crystal spot has formed at the focal point of the femtosecond laser beam in the glass. The mechanism of the observed phenomena is discussed.

The photosensitive effect of Ce on the precipitation of Ag nanoparticles induced by femtosecond laser in silicate glass

This paper studies the photosensitive effect of cerium oxide on the precipitation of Ag nanoparticles after femtosecond laser irradiating into silicate glass and successive annealing.Spectroscopy analysis and diffraction efficiency measurements show that the introduction of cerium oxide may increase the concentration of Ag atoms in the femtosecond laser-irradiated regions resulting from the photoreduction reaction Ce^3＋ ＋ Ag^＋ → Ce^4＋ ＋ Ag^0 via multiphoton excitation.These results promote the aggregation of Ag nanopartieles during the annealing process. It is also found that different concentrations of cerium oxide may influence the Ag nanoparticle precipitation in the corresponding glass.

The effect of spherical aberration on temperature distribution inside glass by irradiation of a high repetition rate femtosecond pulse laser

In this paper, we study the effect of spherical aberrations on the light intensity and the temperature distribution in the focal region in a 250-kHz femtosecond laser irradiated Ag^＋-doped borosilicate glass. When a focused beam goes through an interface between air and glass, spherical aberration will result in the separation of the focal point and then cause a clear change of the light intensity distribution along the incident direction. That phenomenon will further influence the longitudinal cross-section temperature distribution in glass. Here we use Ag nanoparticle formation as a marker for establishing temperature distribution and we find that the formation of nanoparticle shows a strong dependence on the temperature field and the detailed precipitation process is also discussed.

Highly Er^(3+)/Yb^(3+) Co-Doped Fluoroaluminate Glasses for Microchip Laser at 1.54 μm

A series of highly Er^(3+)/Yb^(3+) co-doped fluoroaluminate glasses were investigated in order to develop a microchip laser at 1.54 μm under 980 nm excitation. Measurements of absorption, emission and up-conversion spectra were performed to examine the effect of concentration quenching on spectroscopic properties. In the glasses with Er^(3+) concentrations below 10% (mol fraction), concentration quenching is low and the Er^(3+)/Yb^(3+) co-doped fluoroaluminate glasses gave stronger fluorescence of 1.54 μm from the (()~4I_(13/2))→(()~4I_(15/2)) transition than those of Er^(3+) singly-doped glasses. In the glass with Er^(3+) concentrations above 10%, concentration quenching of 1.54 μm obviously occurs more than that of the Er^(3+) singly-doped samples because of the back energy-transfer from Er^(3+) to Yb^(3+). To obtain the highest emission efficiency at 1.54 μm, the optimum doping-concentration ratio of Er^(3+)/Yb^(3+) is found to be approximately 1∶1 in mol fraction when the Er^(3+) concentration is less than 10%.

Glass Marking with CO₂Laser: Experimental Study of the Interaction Laser - Material

Laser marking is a laser processing technology used in many fields of industry like automotive [1], aerospace [2], microelectronic [3] and medecine [4]. CO2 laser is an appropriate source for marking glasses [5]. Compared to the other techniques of marking, the principal advantages of the use of the laser are: made inalterable, high degree of accuracy and the smoothness of the features, the possibility of marking at difficult to reach places, and the fact of being able to mark fragile materials like ceramic and glass [6]. In this experimental work, the influence of marking parameters like interaction time laser-glass, laser power, shooting time etc. on the micromarking precision are reported. A “melt” depth prediction model has been established.