This paper reports the dopant ion (Nd3+) concentration effects on its luminescence properties in a new glass system based on barium-alumino-metaphosphates. Amongst the studied concentrations range of 0.276–13.31×1020 ions/cm3, the glass with 2.879×1020 ions/cm3 (1 mol%) Nd3+ concentration shows intense NIR emission from 4F3/2 excited state, followed by a decrease in emission intensity for further increase in Nd3+ ion concentration. The observed luminescence quenching is ascribed to Nd3+ self-quenching through the donor-donor migration assisted cross-relaxation mechanism. The microscopic energy transfer parameters for donor-acceptor energy transfer, C
 DA, and donor-donor energy migration, C
 DD, have been obtained from the theoretical fittings to experimental decay curves and the spectral overlap model respectively. The C
 DD parameters (×10−39 cm6/sec) are found to be about three orders greater than that of C
 DA (×10−42 cm6/sec) for Nd3+ self-quenching in this host, demonstrating that the excitation energy migration among donors is due to the hopping mechanism. The energy transfer micoparameters obtained in the present study are comparable to the values reported for commercially available laser glasses LHG-8 and Q-98.

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Concentration quenched luminescence and energy transfer analysis of Nd 3+ ion doped Ba-Al-metaphosphate laser glasses

We report passive Q switching of Nd:YAG lasers with the use of a bulk InGaAsP film, grown on an InP substrate by liquid-phase epitaxy, as an intracavity saturable absorber. The single Q-switched pulse had a maximum energy of 1.65 mJ with a 20-ns duration. The simple technology is easily extendible to any infrared solid-state laser.

Passive Q switching of Nd:YAG lasers by use of bulk semiconductors.

A conventional pulsed Nd:YALO oscillator was passively Q-switched with a Cr4+:YAG crystal. During each of the flashes, with a repetition rate of 100 Hz, a burst of 27 Q-switch pulses with a half width (FWHM) of 140 ns was generated. The minimal pulse-to-pulse time interval within the burst was about 5 µs. The average repetition rate of these Q-switch pulses was 27 × 100 Hz. Nd: YALO as active material does not show any thermally induced birefringence and therefore a good TEM00 mode was realized despite the high thermal load of the crystal. The 4 × 79 mm laser rod produced 13 W average output power at 1080 nm with an efficiency of 0.5%. In contrast to earlier used LiF:F
 2
 −
 absorbers as passive Q-switch the Cr4+:YAG-crystals did not bleach and therefore the system operated very stable and reliable.

Cr4+:YAG as passive Q-switch for a Nd:YALO oscillator with an average repetition rate of 2.7 kHz, TEM00 mode and 13 W output

Cr4+-doped YAG has been investigated as a passive Q-switch in a diode-pumped Nd:YAG laser. Data on the saturation characteristics, efficiency, pulse stability, and optical damage threshold are presented.

Experimental Investigation of Cr 4+ in YAG as a Passive Q-Switch

A model is proposed for the dynamics of evolution of various transverse modes in the resonator of a passively Q-switched laser. On the basis of this reasoning, a double-pulse YAG:Nd3+ laser with a delay between pulses controllable in the 20–100 ns range was implemented experimentally. A satisfactory agreement was obtained between the parameters of the real laser and the results of the numerical calculations. By using this laser to irradiate a target, it was possible to improve severalfold the contrast of the laser plasma luminescence spectrum.

Double-pulse YAG:Nd3+ laser with a controllable delay in the 20–100 ns range

An investigation was made of the energy characteristics of a YAG:Nd3+ laser subjected to pulse-periodic pumping and to passive Q switching of a resonator by an LiF crystal containing color centers. A comparison was made of the energy of giant laser pulses obtained using passive and electrooptic switches when the pump pulse repetition frequency was up to 50 Hz. The use of a passive switch made of an LiF: crystal under optimal lasing conditions did not reduce the energy of the output pulses of the laser compared with that attainable using an electrooptic Q switch.

Pulsed YAG:Nd3+ laser with a passive Q switch in the form of an LiF crystal containing centers

A theoretical study is made of the influence of a longitudinal optical inhomogeneity of a nonlinear crystal on the value and spectral dependence of the gain, which is calculated numerically for arbitrary parameters of the inhomogeneity. An analytic dependence of the gain in the inhomogeneity parameters is obtained in the two most typical cases of a weak inhomogeneity (linear and step) in nonlinear LiNbO3 crystals. A study is made of the influence of an inhomogeneity on the width and shape of the parametric gain profile. The results are used to formulate requirements in respect of the inhomogeneity parameters of nonlinear crystals suitable for optical parametric oscillators. A report is given of an experimental study of the dependence of the average power of a singly resonant parametric oscillator on the inhomogeneity parameter of an LiNbO3 crystal. The experimental results confirm the theoretical predictions.

B G Lysoĭ

Papers

Pulsed YAG:Nd3+ laser with a passive Q switch in the form of an LiF crystal containing centers

Influence of the longitudinal inhomogeneity of the refractive index of a nonlinear crystal on the parametric gain