Neodymium Laser Radiation Research Articles

Three-micron laser action in Dy3+

An experimental investigation was made of laser action in Dy3+ ions in an LaF3 crystal excited by neodymium laser radiation. It is shown by calculation that neodymium laser radiation may be converted to the three-micron range with an efficiency of the order of 10% using Y3Al5O12:Yb3+:Dy3+ and BaY2F8:Dy3+ media.

Ionization of isolated deuterium pellets by neodymium laser radiation

Freely falling deuterium pellets containing 1...2*1018 deuterium atoms were irradiated with a high power Nd laser and ionized. For complete ionization of the pellet it is necessary to apply the laser energy in two consecutive pulses separated by a few hundred nanoseconds. The first laser pulse with only little energy disintegrates the pellet, whereas the main following ionizes the material. The influence of the following parameters on plasma production were investigated: laser energy of prepulse and main pulse, pulse separation, laser beam diameter at the pellet sites and irradiation from one and two directions. Under optimum conditions for all these parameters-which are not independent of each other-almost 100 per cent ionization of the pellet was achieved. Approximately 30 per cent of the laser energy is measured as ion kinetic energy of the plasma. The number of electrons was determined by holographic interferometry, the number and energy of ions were measured with 12 Faraday cups. The laser energy balance was achieved with various diodes, calorimeters and an integrating sphere around the pellet site.

Use of LiYbF4:Ho3+as an active medium in a laser frequency converter

It was found that LiYbF4:Ho3+ is an efficient converter of neodymium laser radiation to the infrared range (1.06-2.06μ). A cascade stimulated emission scheme was realized for the first time at room temperature in a solid-state laser utilizing Ho3+ ions.

Evolution of a laser plasma near a solid target in high pressure gases

A study is reported of the evolution of a laser plasma near the surface of a solid target subjected to neodymium laser radiation having a flux density q which was varied over the range 1–10 MW/cm2. A qualitative analysis is made of the mechanism of laser plasma generation near a solid target, over a wide range of pressures p (1–120 atm) of the gas surrounding it (nitrogen, helium). There are three plasma generation mechanisms, depending on the values of q and p.

Laser frequency converter based on a BaYb2F8:Ho3+crystal. Stimulated emission at 2μ.

An investigation was made of conversion of neodymium laser radiation to the 2-μ wavelength range by means of a BaYb2F8:Ho3+ laser crystal. The most important spectroscopic and lasing characteristics of the crystal were determined.

Changes in the gain of stimulated Raman scattering of neodymium laser radiation by rotational levels of gaseous hydrogen

Measurements were made of the gain of stimulated Raman scattering by rotational levels of gaseous hydrogen in the case when the directions of rotation of the polarizations of the pump (neodymium laser) radiation and of the Stokes signal coincided or were opposite. The dependence of the gain on the hydrogen pressure was found. It was found that a ~50% efficiency of conversion into just the first Stokes component could be acheived without any special measures to suppress the second component.

Transient self-diffraction of laser beams in an absorbing liquid

Theoretical and experimental investigations were made of the transient self-diffraction of neodymium laser radiation in an absorbing liquid. Calculations carried out without assuming a constant pump field showed good agreement with the experimental results. The high energy efficiency of the conversion process and the virtual absence of distortion effects in the liquid suggests that this process may be used to compensate for laser radiation wavefront deformations. The possibility of increasing the axial brightness was demonstrated in a model experiment by introducing appreciable phase distortions into a strong beam.

Temperature dependence of the absorption coefficient of optical glasses exposed to laser radiation

Results are presented of an interferometric investigation of the refractive index variations of K8 and L47 glasses and laser glasses under the action of neodymium laser radiation. Thermal instability, found in the laser glasses, is associated with the thermal excitation of the ions to the 4I11/2 level and with the existence of a nonradiative decay channel for the metastable level via the higher 2G9/2 level. The cross section of the 4F3/2→2G9/2 transition is determined.

Parametric conversion of infrared radiation in zinc-germanium diphosphide

Computer calculations were made of the main characteristics of an infrared parametric converter utilizing a ZnGeP2 crystal pumped by YAG:Nd3+ laser radiation. An experiment was carried out to study the conversion of CO2 laser radiation into the visible range using ZnGeP2 specimens, which exhibited considerable absorption. A conversion coefficient of 0.05 was obtained using a Q-switched pump laser with a power density of 3 MW/cm2 and a crystal 0.3 cm long. An investigation was made of the resistance of the ZnGeP2 crystal to damage caused by pulsed neodymium laser radiation and cw CO2 laser radiation.

Generation of subnanosecond light pulses in CdS

Subnanosecond light pulses (λ =495 nm, τ =6×10-11 sec) were generated in CdS single crystals (T=77 °K) by excitation with the third harmonic of radiation emitted from a mode-locked neodymium laser. The angular divergence, luminescence spectra, and stimulated emission spectra were determined at various pumping (by neodymium laser radiation) rates.

Two-photon absorption of neodymium laser radiation in gallium arsenide

We have studied the interaction of picosecond pulses from a Nd : glass laser with GaAs. The experimental data at incident powers up to ∼30 GW/cm2 can be satisfactorily explained in terms of two-photon absorption with β=0.015±0.005 cm/MW. The results are discussed in connection with the discrepancies existing in the literature about the experimental values of β. Their implications for the existence of self-induced transparency effects in GaAs are also briefly pointed out.

Dynamics of self-interaction of neodymium laser radiation in II–VI semiconductors

It is shown that a positive change in the refractive index n, in the field of a light wave, in II–VI semiconductors follows the variation in light intensity in a single laser pulse with practically no time lag, but the relaxation of the negative nonlinear contribution to n correlates with the lifetime of the nonequilibrium free carriers which result from two-photon absorption. It is also shown that the principal mechanism of nonlinearity in n which leads to self-focusing is the nonlinear polarizability of the bound electrons, whereas the nonequilibrium free carriers determine the nature of the nonlinearity which results in self-defocusing of the laser beam.

Generation of laser radiation of difference frequency in a rectangular millimeter waveguide

Results are reported for an experimental investigation of the generation of the difference frequency of partially mode-locked neodymium laser radiation in a nonlinear lithium niobate (LiNbO/sub 3/) crystal placed inside a rectangular waveguide. Difference-frequency radiation was detected at a wavelength of about 8 mm and also in the wavelength range from 2 to 4.5 mm the measurements indicate that the radiation was maximum in the 70-GHz range and that the spectral density of the radiation was independent of crystal length. Focusing with a cylindrical lens is found to increase the conversion efficiency of the laser radiation approximately twofold in comparison with the case of a homogeneous distribution of the laser beam across the waveguide. The experimental results are compared with theoretical calculations of difference-frequency generation in a rectangular waveguide.

Tunable Raman laser based on the third Stokes component of liquid nitrogen

Stimulated emission was obtained at a wavelength of 4 ? (with continuous tuning within 0.15 ?) as a result of conversion of neodymium laser radiation into the third Stokes component in a liquid nitrogen Raman laser. The output radiation of the Raman laser was used to determine the isotopic structure and spectroscopic characteristics of the P(4) line of the principal vibrational band of the HBr molecule. The measured isotopic shift was 0.29?0.05 cm?1.

Influence of self-focusing on laser damage to II-VI semiconductors

An investigation was made of the nature and magnitude of the threshold of damage caused by ruby and neodymium laser radiation to

Correlation of the efficiency of cooperative sensitization of luminescence with the intensity of Rayleigh scattering

An analysis was made of the fine structure of the Rayleigh scattering spectra and of the efficiency of conversion of neodymium laser radiation into visible light in activated potassium germanate glasses of various compositions. A correlation was found between the intensity of the central component in the Rayleigh scattering spectrum and the intensity of the Tb3+ ion luminescence due to the cooperative sensitization of Tb3+ by Yb3+. This effect is interpreted by assuming activator segregation. It is concluded that the effect is fairly common and it may be used in the search for, and investigations of, quantum-electronic materials.

Pulp effects of neodymium laser: A preliminary report

A total of eight teeth from two rhesus monkeys were exposed to various amounts of neodymium laser radiation. The pulp response was found to be much less severe than that in a study of nineteen teeth previously reported for exposure to similar amounts of ruby laser radiation. If additional studies support this initial finding, it is suggested that a re-evaluation of neodymium laser-mediated procedures in vital teeth be initiated.

Continuous dynamic frequency tuning of pulse laser radiation

It is demonstrated for the first time that stimulated emission tuned continuously over a wide range can be obtained from pulse lasers with wide gain profiles (including solid-state lasers). The tuning range is at least two orders of magnitude greater than the intermode spacing and this is achieved by varying the length of a resonator emitting quasicontinuously by 100 or more wavelengths during stimulated emission. A report is given of experimental attainment of continuous tuning of single-mode neodymium laser radiation in a range of 0.5 cm?1. Estimates obtained indicate that under certain conditions it is possible to achieve continuous tuning of ruby laser radiation in the range 1?2 cm?1, of neodymium glass laser radiation in the range 5?8 cm?1, and of dye laser radiation in a range up to 100 cm?1.

Frequency conversion of neodymium laser radiation by resonant pumping of YAG crystals activated with Tm3+and Ho3+ions

Stimulated emission from Tm3+ and Ho3+ ions in an yttrium aluminum garnet (YAG) crystal was obtained for the first time by pumping with neodymium laser radiation via the absorption band of Yb3+. The stimulated emission wavelength of the Tm3+ ions was 2.014 μ and that of the Ho3+ ions was 2.09 μ. The room-temperature output energy was of the order of 10 mJ. The experimental results indicated that the efficiency of conversion of the neodymium laser wavelength to the 2 μ. range could be increased to values limited by the Stokes losses.

Efficiency of two-photon absorption in single-frequency and multifrequency laser radiation fields

An experimental study was made of the dependence of the two-photon absorption of neodymium laser radiation in an alcohol solution of rhodamine 6G on the intensity of the excitation field under the following conditions: single-frequency emission, emission of 3–5 axial modes, and emission of a large number of longitudinal modes (~300). It was found that the efficiency of the two-photon absorption in the field of 3–5 modes was 1.5 times higher and the corresponding absorption in the multifrequency field and 2.1 times higher than the efficiency of absorption in the single-frequency field.