Neodymium Phosphate Glass Laser Research Articles

Generation of negative pressures and spallation phenomena in diamond exposed to a picosecond laser pulse

The spallation phenomena in poly- and single-crystal synthetic diamonds have been experimentally investigated. A shock-wave impact on a target was implemented using a laser pulse in the Kamerton-T facility. The ablation pressure of on the front target surface was formed by pulsed radiation of a neodymium phosphate glass laser (second harmonic , pulse energy ) with an intensity as high as . The maximum diamond spall strength is found to be 24 % of the theoretical ultimate strength. Raman scattering data indicate that a small amount of crystalline diamond in the spallation region on the rear side of the target is graphitised.

Laser Initiation of Energetic Materials: Selective Photoinitiation Regime in Pentaerythritol Tetranitrate

We describe and analyze the selective (resonance) laser-induced initiation of chemical decomposition reactions in pentaerythritol tetranitrate (PETN, C5H8N4O12) and propose a potential mechanism for the phenomenon. On the basis of our experiments, the photoinitiation of PETN is a two-stage process that is comprised of a laser-induced optical excitation of the molecule with an activation energy of 1.17 eV (1060 nm) by a neodymium phosphate glass laser followed by the thermal decomposition of the excited state with an energy barrier of 0.4 eV. We also illustrate that the small efficiency of the optical absorption of PETN at this wavelength can be enhanced by the MgO light-scattering additives, which significantly increase the absorption due to multiple scattering incidents in PETN. The resonance photoinitiation clearly demonstrates a possibility for designing tunable explosive material systems and identifies ways to control the sensitivity of the materials to rapid decomposition.

Diode-array-pumped repetitively pulsed neodymium phosphate glass laser

Repetitively pulsed generation (200 μs, 40 Hz) was obtained in a neodymium phosphate glass laser pumped by a 870-nm diode array. The maximum slope lasing efficiency with respect to the optical pump energy equal to 13% is restricted by the factor (≈0.23) of active-medium filling by the mode field. By adjusting the laser cavity, the single-transverse mode regime, in particular, the generation of the TEM00 mode is obtained in the entire range of pump energies.

Generation of high-order Hermite–Gaussian modes in a flashlamp-pumped neodymium phosphate glass laser and their conversion to Laguerre–Gaussian modes

The Hermite–Gaussian modes up to the third order inclusive are generated in a flashlamp-pumped neodymium phosphate laser and converted to the corresponding Laguerre–Gaussian modes in an astigmatic converter. It is also shown that, by using a laser with the gain minimum on the axis of a plane-spherical resonator and changing its Fresnel number, it is possible to excite efficiently Laguerre–Gaussian modes with the field amplitude dependence .

Highly efficient generation of tunable picosecond pulses in an LiF:F2- laser crystal

An investigation was made of a synchronously pumped pulsed LiF:F2- crystal laser. The pump radiation was provided by a neodymium phosphate glass laser operating under passive mode-locking conditions and generating pulses of 7 ps duration. The LiF:F2- laser generated 2 ps pulses tunable in the 1.10–1.22 μm range and the efficiency of the conversion process was 35%. Under the conditions of quasi-cw nanosecond pumping and active mode locking the LiF:F2- laser generated pulses of duration of the order of 400 ps.

High-power neodymium phosphate glass laser for experiments on the interaction of ultrahigh optical fields with matter

Preliminary results are reported on the development of a high-power neodymium phosphate glass (λ = 1.053 μm) laser system designed for experiments on the interaction of picosecond pulses with matter. The system comprises a laser oscillator with negative feedback, a Q-switched preamplifier, and a multistage amplifying channel. Amplification of chirped pulses is followed by their compression in the system. The results of experiments on the interaction of high-intensity (I < 1015 W cm-2) laser radiation pulses of different duration with targets in a vacuum chamber are reported. The characteristics of a laser plasma formed in this way are also reported.

GENERATION OF SHOCK WAVES BY LASER-MATTER INTERACTION IN CONFINED GEOMETRIES

GENERATION OF SHOCK WAVES BY LASER-MATTER INTERACTION IN CONFINED GEOMETRIES

Generation of giant pulses with the same single-frequency spectrum and a controlled repetition interval in neodymium phosphate glass lasers

The conditions for single-frequency quasi-cw operation were identified for a solid-state pulsed laser with a ring resonator and a dynamic amplitude switch. Single-frequency (Δν≤0.002 cm−1) pulses up to 1.5 ms duration were generated by a neodymium phosphate glass laser when a mirror in an amplitude switch was set in motion at a velocity of 40 mm/s. When active Q switching was used, the method of injection of seed radiation made it possible to generate pairs of single-frequency giant pulses with an identical spectrum and with a controlled (0–1.5 ms) interval between them.

Active mode locking in a solid-state (concentrated neodymium phosphate glass) laser by a modulator with regular domain structures

Active mode locking in a long-resonator laser was performed using regular domain structures. Intracavity conversion of the output radiation to the second harmonic was achieved by such modulation. The width of the emission spectrum was measured. A negative feedback loop was used to increase the duration of a train of pulses under active mode-locking conditions.

Use of nonlinear dynamic spectroscopy in determination of the chirp of picosecond pulses generated in a neodymium phosphate glass laser

A nonlinear dynamic spectrograph with a time resolution of 0.1 psec and a spectral resolution of 0.02 nm was used to determine the chirp of picosecond pulses generated in a neodymium phosphate glass laser emitting at the wavelength of 1.054 µ. A time scan was obtained employing a nonlinear LiIO3 crystal together with conversion of the investigated radiation to the visible range, where dynamic spectrograms were recorded. It was established that the chirp amplitude increased at the end of a train of pulses to 1.5 nm/psec.

Self-stabilization of ultrashort pulses emitted by a neodymium phosphate glass laser

An investigation was made of the emission spectra of a neodymium phosphate glass laser during various stages of formation of ultrashort pulses. The kinetics of the spectrum of free lasing with passive mode locking was observed first. Considerable changes in the spectrum were observed for successive free-lasing spikes, which made it impossible to achieve self-stabilization of the ultrashort pulse duration. The spectrum of ultrashort pulses varied with the point of selection of a pulse in a train. The results were explained allowing for the simultaneous influence of burning of spectral holes in the population inversion and phase self-modulation on the operation of a laser with passive mode locking.

Stimulated Brillouin scattering mirror in the form of a multimode optical fiber in a four-pass neodymium phosphate glass laser amplifier

A multimode optical fiber was used as a wavefront-reversing mirror in a four-pass laser amplifier utilizing neodymium phosphate glass.

Mode locking of a Nd:glass laser with

Lithium fluoride crystal containing F2− color centers (LiF:F2−) as a saturable absorber has been used for passive mode locking of a neodymium phosphate glass (Nd:glass) laser. Complete modulation, i.e., 100% depth, was achieved. The time resolution of the modulated laser output was studied using a photochron streak camera. LiF:F2− crystal optimization and a Nd:glass laser operating optimization were proposed. The use of color center crystals as saturable absorber shows promise.

Continuous wave mode-locked neodymium:phosphate glass laser

We report the first successful mode locking of a cw neodymium phosphate glass laser. Transform-limited, 80-ps pulses were generated at 1.054 μm.

Subpicosecond neodymium phosphate glass laser

A description is given of a passively mode-locked neodymium phosphate glass laser emitting pulses with an average duration of 0.7 psec.

Generation of subpicosecond continuously frequency-tunable infrared pulses

An investigation was made of a cavity optical parametric oscillator (COPO) utilizing a KDP crystal pumped synchronously with the second harmonic of a picosecond neodymium phosphate glass laser with passive mode locking. A strong discrimination of the time profile of the signal under conditions of gain saturation and group velocity mismatch resulted in generation of subpicosecond pulses (~0.5 psec) in the COPO when the duration of the pump pulses was 3–5 psec. The COPO was tunable in the range 0.82–1.3 μ, the energy efficiency of the conversion process was 2%, and the average energy of a single subpicosecond pulse was 20 μ J. A numerical analysis was made of the transient parametric amplification in the COPO and the subpicosecond COPO was optimized so as to reduce the pulse duration and increase their contrast.

High-power neodymium phosphate glass laser system with improved spectral and spatial characteristics of the radiation

A high-power single-pulse neodymium phosphate glass laser system having radiation characteristics similar to those of a plane linearly polarized monochromatic wave is described. Smooth profiles of the temporal and spatial distributions are achieved by using a single-frequency master oscillator and a simple system for formation of the spatial distribution of the radiation provided that the quality of all the optical elements is controlled. It is noted that inhomogeneous broadening in the spectrum of Nd/sup 3 +/ ions influences the gain of the laser radiation.

Nanosecond neodymium phosphate glass laser pumped by laser radiation

The active element made of concentrated neodymium phosphate glass and placed in a short resonator emitted pulses of 2.5 nsec duration. The element was pumped by pulses of 30 nsec duration and 0.53 μ wavelength. The experimental results are analyzed.

Limiting repetition rate of a neodymium phosphate glass laser

Limiting repetition rate of a neodymium phosphate glass laser