Nd-doped Phosphate Glass Research Articles

Study on surface modification and optical properties of Nd-doped phosphate glass

Using laser neodymium glass (N31) as the substrate, through ion exchange and hydrogen reduction process, a high-efficiency light absorption layer was formed from the substrate around the glass. It has been discovered that increasing the ion exchange temperature and time enhanced the exchange depth of laser glass, but excessive temperature and prolonged time will lead to corrosion of laser glass. The experiment shows that the best exchange temperature is 460°C and the best exchange time is 720min. When the hydrogen pressure was 0.8MP, the reduction temperature was 480°C and the reduction time was 12000 min, the absorption rate of the sample at 1053nm was 95.8%.

Numerical Simulations of the Influence on the Temperature Fields of Large-Sized Nd-Glass Slab with Designed Edge-Cladding Materials, Methods, and Structures

The good cladding of a large-sized Nd-doped phosphate glass slab as a laser amplifier requires not only the amplified spontaneous emission and parasitic oscillation to be fully absorbed, to hold up the small signal gain coefficient of the Nd ions, but also the absorbed heat energy to be appropriately dissipated to extend a uniform temperature field for the larger laser beam aperture of the edge-cladded Nd–glass slab. In the present work, numerical simulations were performed based on the developed feasible edge-cladding designs for a 786 × 436 × 40 mm3 Nd–glass slab, including the following alterations: optical absorptivity, quantum-dot absorption centers, ceramics with higher thermal diffusivity, glasses with lower and higher specific heat values, 3D printing edge-cladding methods, double-deck edge-cladding structure with transparent strips as a buffer layer, and thickening of the edge-cladding. All of these designed edge-cladding materials, methods, and structures satisfy both requirements of sufficiently absorbing and precisely matching with the refractive index, as emphasized by the edge-cladding for the Nd–glass. Some of the designed edge-claddings resulted in a much more uniform temperature field than the composite polymer–glass edge-cladding as the standard for comparison, which could be utilized to extend the effective laser aperture of the Nd–glass slab, thus being beneficial to the laser beam size and laser energy in the optics recycle loop strategy.

Thermal effects reduction in a diode side-pumped rod-like bonded α-quartz||Nd:glass||α-quartz amplifying medium

We present a numerical study of a square-shape rod-like bonded laser gain medium operating at 1053 nm. The sample is composed of a 5-mm thick Nd-doped phosphate glass bonded to two α-quartz crystals. Owing to this face cooling scheme, the heat generated in the gain medium is effectively reduced, hence resulting in less optical distortions. The simulation of the thermomechanical effects was conducted using COMSOL MultiPhysics® software. Transverse wavefront distortion and birefringence profiles were computed for a given pump mean power. Wavefront and birefringence measurements will be conducted on the bonded sample using a pump-probe setup which is discussed in this paper. These measurements will be presented and weighed with the numerical results.

Thermal lens in diode-pumped square-section rods of Nd-doped phosphate glass and 0.5%Nd:5%Lu:CaF2 crystal: simulations and experiments.

We performed simulations and experiments of wavefront distortions induced by propagating through diode-pumped square-section amplifying laser rods of Nd-doped phosphate glass and 0.5%Nd:5%Lu:CaF2. We observed that depending on the material, wavefront distortions' profile can vary from a circular lens-like distortion to a complex astigmatic distortion. We showed that this difference comes from the relative sign of piezo-optic tensor coefficients.

Fabrication of planar optical waveguides by 6.0 MeV silicon ion implantation in Nd-doped phosphate glasses

We report the fabrication of a planar optical waveguide by silicon ion implantation into Nd-doped phosphate glass at an energy of 6.0 MeV and a dose of 5.0 × 1014 ions/cm2. The change in the surface morphology of the glass after the implantation can be clearly observed by scanning electron microscopy. The measurement of the dark mode spectrum of the waveguide is conducted using a prism coupler at 632.8 nm. The refractive index distribution of the waveguide is reconstructed by the reflectivity calculation method. The near-field optical intensity profile of the waveguide is measured using an end-face coupling system. The waveguide with good optical properties on the glass matrix may be valuable for the application of the Nd-doped phosphate glass in integrated optical devices.

Nd-doped phosphate glass cane laser: from materials fabrication to power scaling tests

We report on the fabrication and characterization of two Nd-doped active glasses and two compatible cladding compositions. The materials were synthesized to be compatible in terms of thermal expansion and characteristic temperatures. The glass system with higher refractive index and absorption cross-section was selected for the fabrication of a core/cladding cane with a diameter of 800 μm. Laser experiments, performed on a 60 mm-long cane, show laser emission at 1054 nm with output power higher than 2 W and efficiency above 40%. These values, obtained on a very simple geometry, are promising for the development of short-length cane lasers and amplifiers for emission in the 1 μm region.

Effect of gamma irradiation on X-ray absorption andphotoelectron spectroscopy of Nd-doped phosphate glass.

X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectroscopy (XPS) of Nd-doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of the L3-edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d5/2 peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy-dispersive X-ray spectroscopy measurements. The ratio of non-bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration.

Thermal window of constant luminescence quantum efficiency of Nd3+-doped phosphate glass

In this work was investigated the luminescence quantum efficiency, η, of Nd-doped phosphate glasses, as a function of temperature (298–438K), using the normalized lifetime thermal lens technique. This system presents high quantum efficiency at low Nd3+ concentration and at ambient temperature, 98%. In the temperature interval from 298 to 313K, η, presents a decrease and then becomes constant until 393K. Above this temperature it decrease again. This thermal quenching process was ascribed to thermally activated low energy phonons, associated to rocking motions of the corner-shared PO4 tetrahedron cluster (order–disorder phase transformation), inducing changing on non-radiative transition that leave to a reduction of luminescence quantum efficiency at 298 and 393K. From 313 to 393K occurs a constant window of luminescence quantum efficiency in the PANK+xNd3+ system. This assumption is supported by Differential Scanning Calorimetry and Raman measurements.

Experimental study of diode-pumped Nd, Y:CaF2 amplifier for inertial confinement fusion laser driver

In a conventional laser-driven inertial confinement fusion (ICF), Nd-doped phosphate glass is used as a gain medium. However, the repetition frequency operation of such a laser system is restricted by the low thermal conductivity of the phosphate glass. To attain a high ICF performance, the laser driver must be able to operate at a repetition frequency of no less than 10 Hz. Typically, an Nd-doped laser glass operates at a repetition frequency well below 10 Hz. In this paper, an Nd, Y:CaF2 crystal is taken as a gain medium for the laser amplifier, and experiments are carried out to demonstrate the capability of Nd, Y:CaF2 crystal to act as a gain medium for ICF laser driver. A laser-diode plane-array five-direction horizontal-side-pumped Nd, Y:CaF2 laser amplifier 5 mm70 mm is developed and an experimental study is carried out. The absorption spectrum and emission spectrum of Nd, Y:CaF2 crystal and the fluorescence distribution of the amplifier are measured. The Nd:CaF2 co-doped with Y3+ ions results in a broad absorption band, which makes the laser diode pumping more efficient. The strongest excitation band peak is centered around 796 nm. The small signal gains of Nd, Y:CaF2 and Nd:Glass working respectively at repetition frequencies of 10 and 1 Hz under the same pump power are measured. The small signal gain of Nd, Y:CaF2 amplifier reaches 6.12 under a pump power of 9.63 kW, which is 1.5 times that of Nd:Glass amplifier. The measurements of the spectrum of the seed beam and the spectrum from Nd, Y:CaF2 amplifier show that the signals have no change before and after being amplified. Most likely the Nd, Y:CaF2 crystal is a promising laser material for repetitive ICF laser drivers.

Investigation on thermal properties of a new Nd-doped phosphate glass

Thermal properties of a new Nd-doped phosphate glass were investigated. The thermal expansion coefficient was measured by a dilatometric technique. A Mach–Zehnder interferometer was used to measure the temperature coefficient of refractive index (dn/dT) and the thermo-optic coefficient (ds/dT) in the temperature range of 30–100°C. A low thermal expansion coefficient was observed for the new phosphate glass. The dispersion of the thermo-optic parameters was calculated from an empirical equation. The thermo-optic coefficient (ds/dT) at the working wavelength of 1053nm is lower than those of other high average power glasses. These results indicate that the new Nd-doped phosphate glass is a good candidate for high average power laser applications.

Sensitivity enhancement for measurement of nonlinear refraction using top-hat beams

A simple and high-sensitivity technique is presented to investigate nonlinear refraction. In this technique, a combination of aperture and obscuration disk is introduced in the measurement system. Compared to the top-hat Z-scan, the curves of modified top-hat Z-scan for the nonlinear refraction show a single peak. Furthermore, the sensitivity of this new technique can be more than two orders of magnitude enhanced. Nonlinear refraction of Nd-doped phosphate glass is investigated using this technique with 19 ps pulses at wavelength of 532 nm.

Acousto-optical adaptive correction of a chirped laser pulse spectral profile in a Nd-phosphate glass regenerative amplifier

We present results of experimental research carried out with the help of an acousto-optical light dispersive delay line (LDDL) on spectral correction of chirped laser pulses in a Nd-doped phosphate glass regenerative amplifier (RA) characterized by high gain (G ≈ 4 × 107). The spectral resolution of the LDDL was equal to 1.1 cm−1 at a diffraction efficiency greater than 80%. The use of the LDDL made it possible to implement operating conditions of the RA under which the duration of the output chirped pulse did not shorten in comparison with the duration of the input one, which meant that the width of the spectral emission could be preserved.

Nanoparticle dispersion laser

Lasing action from a dispersion of nanoparticles is reported for the first time to our knowledge. The nanoparticles are Nd(2)O(3) modified with dimethyldichlorosilane (DMDCS) in dimethylsulfoxide. The laser was pumped with a pulsed laser at 802 nm and yielded 2.7 mJ with a slope efficiency of 50%. This was compared to a standard Nd-doped phosphate glass that yielded very similar results in the same setup.

Experimental investigation on laser-induced surface damage threshold of Nd-doped phosphate glass

Nd-doped phosphate glass is the dominant amplifier material used in solid state high average power laser systems. Surface imperfection and subsurface damage (SSD) of the glass, resulting from the optical fabrication process, limit the increment of laser system energy output. Thus, it is important to enhance the surface damage threshold of Nd-doped phosphate glass surface. The in°uence of abrasive size, polishing powder, grinding mode, and chemical treatment on the laser-induced damage threshold (LIDT) of Nd-doped phosphate glass surface is investigated. Results show that the LIDT is affected little by different polishing powders and grinding modes. The LIDT correlates with the abrasive size, which produced different depths of SSD. A suitable acid etching treatment can remove the imperfection and the SSD for improving the LIDT of Nd-doped phosphate glass surface. The combination of several effective techniques and methods, which are low-cost and practical, should be useful to enhance the LIDT of Nd-doped phosphate glass surface.

Phase locking of a compact Nd-doped phosphate multicore fiber laser

Two compact fiber lasers based on the gain medium of Nd-doped phosphate glass multicore fiber (MCF), of length no more than 10 cm, have been demonstrated experimentally for the first time. A stable phase-locked laser beam at 1055 nm emitted from a three-core fiber that is 8.5 cm in length has been achieved, with a maximum output power of 20 mW. The properties of similar seven-core fiber laser also have been investigated.

熔石英和磷酸盐钕玻璃表面三角形微裂纹对入射光的散射分析

熔石英和磷酸盐钕玻璃表面三角形微裂纹对入射光的散射分析

Distribution of electric field and energy flux around the cracks on the surfaces of Nd-doped phosphate glasses

We simulate and calculate numerically the electromagnetic field and energy flux around a surface crack of an Nd-doped phosphate laser glass by using the finite-difference time-domain method. Because of a strong interference between the incident wave and the total internal reflections from the crack and the glass surface, the electric field is redistributed and enhanced. The results show that the electric-field distribution and corresponding energy flux component depend sensitively on the light polarization and crack geometry, such as orientation and depth. The polarization of the incident laser beam relative to the crack surfaces will determine the profile of the electric field around the crack. Under TE wave incidence, the energy flux peak is always inside the glass. But under TM wave incidence, the energy flux peak will be located inside the glass or inside the air gap. For both incident modes, the light intensification factor increases with the crack depth, especially for energy flux along the surface. Because cracks on the polished surfaces are the same as the roots extending down, the probability for much larger intensification occurring is high. The results suggest that the surface laser-damage threshold of Nd-doped phosphate may decrease dramatically with subsurface damage.

Concentration dependent fluorescence quantum efficiency of neodymium doped phosphate glass matrix

Abstract In this work, we have studied the optical and thermal properties of Nd-doped phosphate glass matrix. The studied samples have concentration ranging from 0.5 to 5 wt% of Nd 2 O 3 . Here we report the measurements of fluorescence quantum efficiency, η , obtained through the thermal lens technique using a reference sample. Also, the refractive index, n , specific heat, c p , mass density, and the thermal diffusivity and conductivity measurements were performed. The knowledge of these characteristics as a function of neodymium concentration is very important to design optical devices, especially high power solid state lasers.

Nd-doped phosphate glass microstructured optical fiber laser

We experimentally demonstrated a single-mode laser at 1056 nm with Nd-doped phosphate glass microstructured optical fiber (MOF), which was fabricated with conventional stack-and-draw method. The laser action was observed from a Fabry-Perot cavity formed by placing two dichroic mirrors of ∼100 and 85% reflectivity, to the two end facets of MOF. Pumped by CW laser diodes (LDs) at 808 nm, the MOF laser yielded a maximum output power of 8.5 mW and a slope efficiency of 2%.

The influence of the inhomogeneous gain profile on the spatio-temporal dynamics ofbroad-area class B lasers

A study on the spatio-temporal dynamics of broad-area Nd:YAG (yttrium aluminiumgarnet), Nd-doped phosphate glass and Nd-doped silicate glass lasers is presented to showthe influence of the inhomogeneous gain profile and cross-relaxation phenomena on thespatio-temporal dynamics of the system. The suppression of the order–disorder transitionshown in Cabrera et al (2006 Opt. Lett. 31 1067) for homogeneously broadened class B lasersis found for both glass lasers, independently of the strength of the cross-relaxationmechanisms. The results obtained indicate that a higher degree of inhomogeneousbroadening leads to suppression of the filamentation in the transverse intensity pattern.