Measurement of Thermal Lens Focal Length and Its Effect on Laser Output Characteristics in LD End-pumped Nd:YVO4 Lasers

According to the resonator transform circle theory, the focal length of thermal lens of laser media in laser diode end-pumped solid-state lasers is analyzed and measured with a simple method. A 30W 808nm LD pumped YVO4 laser is developed and characterized.     

Experimental Investigation of Thermal Lensing in End-pumped Nd∶YVO_4 Crystal Using a New Simple Approach

１ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｈｉｇｈｐｏｗｅｒｓｏｌｉｄｓｔａｔｅｌａｓｅｒｓ，ｐｕｍｐｉｎｄｕｃｅｄｔｈｅｒｍａｌｆｏｃｕｓｉｎｇｉｓｏｆｐｒｉｍａｒｙｉｍｐｏｒｔａｎｃｅｂｅｃａｕｓｅｏｆｉｔｓｓｉｇｎｉｆｉｃａｎｔｉｎｆｌｕｅｎｃｅｓｏ...     

Modulated Pulse Generations in a Laser-diode-pumped Passively Q-switched Intracavity-frequency-doubling Nd∶YVO_4 Laser

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｉｔｉｓｅａｓｙｔｏｏｂｔａｉｎｈｉｇｈｈａｒｍｏｎｉｃ ｃｏｎｖｅｒｓｉｏｎｅｆｆｉｃｉｅｎｃｙｂｙ ｐｌａｃｉｎｇｔｈｅｄｏｕｂｌｉｎｇｃｒｙｓｔａｌｉｎｔｏｔｈｅｒｅｓｏｎａｔｏｒｄｕｅｔｏｔｈｅｈｉｇｈｆｕｎｄａｍｅｎｔａｌ ｗａｖｅ ｐｏｗｅｒｄｅｎｓｉｔｙ ,ｗｈｉｃｈｉｓｅｓｐｅｃｉａｌｌｙｓｕｉｔａｂｌｅｆｏｒｔｈｅｈａｒｍｏｎｉｃｃｏｎｖｅｒｓｉｏｎｏｆＣＷｌａｓｅｒｗｉｔｈｍｉｄｄｌｅｏｒｌｏｗｏｕｔｐｕｔｐｏｗｅｒ.Ｉｆｔｈｅ ｐａｓｓｉｖｅｌｙＱ ｓ…     

Simultaneous Q-switching and Frequency-doubling by a Single KTP Crystal in a Diode-pumped Nd∶YVO_4 Laser

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｃｏｍｐａｃｔｇｒｅｅｎｌａｓｅｒｓａｒｅｏｆｐｏｔｅｎｔｉａｌｉｎｔｅｒｅｓｔｆｏｒｍａｎｙａｐｐｌｉｃａｔｉｏｎｓ ,ｓｕｃｈａｓｕｎｄｅｒｗａｔｅｒｃｏｍｍｕｎｉｃａｔｉｏｎ ,ｏｐｔｉｃａｌｄａｔａｓｔｏｒａｇｅ,ｄｉｓｐｌａｙ ,ａｎｄｃｈｅｍｉｃａｌｐｒｏｃｅｓｓｉｎｇ[1,2 ] .Ａｔｐｒｅｓｅｎｔ,ｍｏｓｔｓｃｈｅｍｅｓｒｅｐｏｒｔｅｄｆｏｒｇｅｎｅｒａｔｉｎｇｇｒｅｅｎｂｅａｍｓａｒｅｂａｓｅｄｏｎｔｈｅｆｒｅｑｕｅｎｃｙｃｏｎｖｅｒｓｉｏｎｏｆｎｅａｒ ｉｎｆ…     

Output Intensity Variations of the Laser Used in a Prism Coupling System and Its Application

The output intensity variations of the laser used in a prism coupling system are observed and found to be induced by the external optical feedback, which comes from the reflection on the prism. The intensity variations are explained with laser theory. The trough in the intensity variation corresponds to the position of the prism when the output light beam propagates perpendicularly to the prism. Based on the trough a new method for rotating the prism and reading out the step numbers is proposed, by which the angle 0° in the system need not to be calibrated. It is proven by experiment that the new method would improve the accuracy of the refractive index up to ±0.00001 and thickness to ±1 nm.     

Investigation on mode matching including thermal effects in LD end-pumped passively mode-locked Nd：YVO_4 laser

We design a laser diode （LD） end-pumped passively mode-locked solid-state laser with a semiconductor saturable absorber mirror. Mode-matching efficiency in the active medium including the thermal effect is analyzed, and the optimum mode-matching coefficient is obtained by optimizing the pump mode. In the experiment, a total power of 4.2 W stable pulse sequences without multipulse at 1064 nm is obtained with a pulse repetition rate of 86 MHz and a pulse width of 13 ps, corresponding to a high optical to optical efficiency of 44%.     

Theoretical Analysis on the Simultaneous Operation of a Color-Center Laser and a -Switched Nd∶YAG Laser

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　ＢｅｃａｕｓｅＬｉＦ∶Ｆ- 2 ｃｏｌｏｒ ｃｅｎｔｅｒｃｒｙｓｔａｌｈａｓｉｔｓｏｗｎｄｉｓｔｉｎｇｕｉｓｈｅｄｃｈａｒａｃｔｅｒｉｓｔｉｃｓ[1～ 5] ,ｉｔｈａｓｂｅｅｎｕｓｅｄａｓａｃｔｉｖｅｍｅｄｉｕｍｓ[4 ,6,7] ｏｒａｓｍｏｄｕｌａｔｅｄｅｌｅｍｅｎｔｓ[8,9] .Ｉｎｔｈｉｓｐａｐｅｒ,ｗｅｗｉｌｌｉｎｔｒｏｄｕｃｅａｎｏｔｈｅｒｋｉｎｄｏｆｕｓａｇｅ ,ｔｈａｔｉｓ ,ｉｔｉｓｕｓｅｄｂｏｔｈａｓａｎａｃｔｉｖｅｍｅｄｉｕｍｆｏｒｃｏｌｏｒｃｅｎｔｅｒｌａｓｅｒｔｕｎａ…     

Orthogonally Linearly Polarized Dual Frequency Nd：YAG Lasers with Tunable Frequency Difference and Its Application in Precision Angle Measurement

The orthogonally linearly polarized dual frequency Nd： YA G lasers with two quarter wave plates in laser resonator are proposed. The intra-cavity variable birefringence, which is caused by relative rotation of these two wave plates in laser inner cavity, results in the frequency difference of the dual frequency laser also changeable. The theory model based on the Jones matrix is presented, as well as experimental results. The potential application of this phenomenon in precision roll-angle measurement is also discussed.     

Gaseous Hydrogenation and Its Effect on Thermal Stability of Mg63Ni22Pr15 Metallic Glass

Mg63Ni22Pr15 metallic glasses are produced by a single roller melt-spinning technique. The hydrogen absorption and desorption capacities are respectively 0.38 and 0.14 wt% at 313 K obtained by pressure-composition isotherm. The amorphous structure is found to be retained after gaseous hydrogenation. The glass transition temperature, the onset crystallization temperature, and the crystallization temperature of the hydrogenated Mg63Ni22Pr15 metallic glass are 550, 570 and 577K, respectively, much higher than the corresponding values of 440, 470 and 499K of the as-quenched sample. This means that dramatic enhancement of thermal stability occurs in Mg63Ni22Pr15 metallic glass due to hydrogenation.     

Effect of the Length and Pressure of a Gas Jet on Optical Harmonics Generation by 4.5-μm Femtosecond Laser Radiation of a Fe:ZnSe Laser System

JETP Letters - The effect of the length and pressure of an argon gas jet on low-order harmonics (5th, 7th, 9th, and 11th) generation by 4.5-μm femtosecond laser radiation of a Fe:ZnSe laser...     

Simulation of Patterns and Qualitative Analysis of Pattern Rotation in an End-Pumped Nd：YVO4 Laser

We simulate some laser output patterns observed in our previous experiment employing superposition of Laguerre- Gaussian modes. The rotating pattern is qualitatively analysed from the point of contemporary spatial burning hole effect of the lasing crystal.     

Effects of Thermal Treatments on Helium Retention and Thermal Desorption Behaviors in a V-4Ti Aalloy

Vanadium alloys are considered as the promising first wall and structure materials of the future fusion reactors owing to their perfect low neutron-induced radioactivity and good high temperature performance. Helium retention and thermal desorption behaviors are key issues for the applications of vanadium alloys in fusion reactors since helium can be produced by helium discharge cleaning and neutron transmutation. A. van Veen groupt investigated helium trapping and thermal desorption mechanisms in vanadium alloys by using 1 keV helium ion irradiation to the fluence of 10^13～10^14He/cm^2, and the influenee of pre-annealing treatments on helium trapping. Two group of peaks were found at the thermal helium desorption spectrum. They thought one was due to helium-vacancyimpurity clusters and the other was corresponding to helium trapping into pre-existing traps, such as fine-size precipitates.     

The Effect of Active Region Heating on Dynamic and Power Characteristics of Quantum Cascade Lasers Emitting at a Wavelength of 4.8 µm at Room Temperature

Optics and Spectroscopy - Results of studying stripe quantum cascade lasers emitting at room temperature in the spectral range of 4.8 µm are presented. Power characteristics and turn-on...     

Temperature effect on emission lines and fluorescence lifetime of the ~4F_(3/2) state of Nd:YVO_4

By measuring the absorption and fluorescence spectra and the fluorescence lifetime of 4F3/2 state of Nd3+ ions in YVO4 (2 at.-%) crystal at different temperature, the effects of temperature on the spectra and the lifetime of F3/2 state have been investigated. As the temperature is increased, the line width of the 4F3/2 -4I11/2 transitions is found to increase and the spectral line toward the longer wavelength, which are duo to the ion-phonon interaction. The variation fluorescence lifetime of the 4F3/2 state of Nd:YVO4 is found to be anomalous in the measured range 8 - 300 K. It is about 81 us at room temperature and decreases to 30 us at 8 K. The experimental results are explained by ascribing to the thermal mixing between the two Stark levels of 4F3/2 state with different lifetime.     

Influence of Thermal Treatment of Ti–45Nb Alloy in Ultrafine-Grained State on Its Structural Parameters and Heat Capacity

Russian Physics Journal - The effect of heat treatment of the Ti – 45 wt.% Nb alloy in the ultrafine- and coarse-grained states on its structural parameters (lattice parameters, volumetric...     

Effect of Pulsed IR Laser Radiation on the Dynamics and Morphology of Deformation Bands in an Aluminum–Magnesium Alloy

The dynamics and morphology of deformation bands under the simultaneous effect of mechanical loading and pulsed IR laser radiation on the surface of in aluminum–magnesium alloy AlMg6 were studied by high-speed video recording. The conditions, under which a laser pulse pierces a through hole with a diameter of an order of magnitude smaller than the thickness of a plane specimen, thus inducing the development of a complicated spatiotemporal structure of deformation bands and a macroscopic jump in the tension diagram, were determined. The morphological transitions associated with the transformation of the type, shape, and spatiostatistical distribution of bands with a change in the laser pulse energy density were revealed. The probable mechanism of this phenomenon was discussed.     

Effect of Laser Radiation near 1.5 µm on the Photoluminescence Parameters and the Ensemble of NV Centers in Diamond

JETP Letters - The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of “nitrogen-vacancy” (NV) color centers in diamond has been studied...     

Effect of the Initial Laser Phase on the Interaction Between Relativistic Electron and Ultra－Intense Laser Field in a Strong Uniform Magnetic Field

We investigate the influence of the initial laser phase on the interaction between relativistic electron and ultraintense linear polarized laser field in a strong uniform magnetic field. It is found that the dynamic behaviour of the relativistic electron and the emission spectrum varies dramatically with different initial laser field phases.The effect of changing initial phase is contrary in the two parameter regions divided by the resonance condition.The phase dependence of the electron energy and velocity components are also studied. Some beat structure is found when the initial laser phase is zero and this structure is absent when the initial laser phase is a quarter of a period.     

Effect of Nd~(3 ) Concentration on theLaser Performance of a New Laser Crystal: Nd: NaY(WO_4)_ 2

The transmission and emission spectra of a new crystal, Nd:NaY(WO4)2(Nd:NYW) have been measured. Using a Ti: Sapphire laser as the pump source, the laser performances of Nd: NYW crystals with different concentrations are compared for the first time. The Nd3 concentrations used are 1, 2, 4 and 5 at.-% . The experiments show that 2 at.-% is the optimum concentration. When the incident pump power is 575 mW, the 1. 06 μm output can reach 184 mW, corresponding to an optical to optical efficiency of 32 % . The experimental results show that the work is significant to the further research and praction application of this promising laser crystal.