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A quantitative study of the up-conversion process ( 4 I 13 2 → 4 I 15 2 ) + ( 4 I 13 2 → 4 I 9 2 → 4 I case11 2 ) , essential in the 3 μm emission of Er3+ in YAG, over a large concentration range (0.1 to 100 at% Er3+) and pumping energy has been performed. The concentration and sample dependence of the “intrinsic” lifetime of 4I 13 2 and 4I 13 2 laser levels is tentatively explained by energy transfer to aleatory impurities. The quadratic concentration dependence of the up-conversion parameter, obtained experimentally, and the possibility to describe the up-conversion process by rate equations are explained by large migration effects and effective interactions between nearest neighbours.

A pulse laser on a phosphate glass activated by Cr3+-Yb3+-Er3+ ions (λ = 1.54 μm) was used to pump Y2Al5O12:Er3+ (YAG:Er) crystals to the lower laser level of a 3-μm transition (4I11/2 → 4I13/2) in Er3+ ions (λ = 2.94 μm). For a pumping pulse energy of Eexc = 200 mJ, the efficiency of 3-μm lasing was 20%. A differential efficiency of the YAG:Er laser in the case of a resonance pumping into the lower laser level amounted to 26%.

Stornatologic service is most popular of all kinds of medical aid, since up to 90% of people suffer from caries, parodontosis holds the second place after such a widespread disease as cardiovascular pathology. The treatment of the tooth hard tissue, intervention into pulp and parodontium using conventional methods are accompanied with painfulness and unpleasant sensation. A lack of efficient methods of anesthesia and pulp devitalization, a high percentage of complica tions after pulpitis treatment made it necessary to search for new methods of treatment which exclude these negative aspects. Application of laser radiation may be one of the ways in resolving this problem. Such attempts have been made repeatedly with the development of laser technology.'3 However, not all of them turned out to be successful. The greatest difficulties occurred on surgical intervention into hard tooth tissue. The best results have been so far attained when using pulsed CO2 laser operated at the wavelength A =1O.61um. For instance, at pulse width 1O1us and frequency 10-20 Hz, the tooth channel drilling was efficient at energy density in pulse P . 10 JIcm2. 4'5 The electron-microscopic investigations have proved the tooth microstructure to be preserved for this laser operation mode. The traces of graphitization were observed only in the vicinity of the lateral walls of the channel.

Excitation of Y2.94Tm0.06Al5O12 crystals with ruby laser radiation resulted in generation of stimulated radiation due to the 3F4–3H5 transition. The duration of the output pulses was approximately five times the duration of the pump pulses. This was attributed to the accumulation of excitation at 1D2 and 3H4 levels.

An investigation was made of the lasing properties of Q-switched YAG:Er/sup 3 +/ crystals (/sup 4/I/sub 11/2/--/sup 4/I/sub 13/2/). An energy of 100 mJ was obtained in the TEM/sub 00/ mode and the pulse duration was 65 nsec. Under free-lasing conditions, the efficiency was 1.25% and the output radiation energy 5 J. The radiation parameters were strongly influenced by the Stark splitting of the /sup 4/I/sub 11/2/ and /sup 4/I/sub 13/2/ active levels.

A comparison of theoretical and experimental results shows that a suitable selection of the spectroscopic parameters of YAG:Er3+ crystals can ensure a qualitative agreement between calculations and experiments (within the limits of the relevant errors). Calculations demonstrate a considerable contribution of direct pumping of the upper active level by flashlamp excitation. The maximum theoretical value of the differential efficiency for the best laser head is 2.7%.

An investigation was made of the kinetics of the luminescence due to 4I11/2 → 4I15/2 and 4I13/2 → 4I15/2 transitions in the Er3+ ion in yttrium erbium aluminum garnet crystals subjected to strong resonant excitation argon laser radiation (λ = 4880 nm). The efficiency of the cooperative process resulting in nonlinear quenching of the luminescence from the 4I13/2 level and sensitization of the 4I11/2 level was estimated. The influence of this process on the kinetics of lasing as a result of the 4I11/2 → 4I13/2 transition (λ = 2.94 μ) was analyzed.

An electrooptic filter was used for broad-band tuning (720–900 nm) of a flashlamp-pumped Al2O3:Ti3+ crystal laser. Some characteristics of the use of electrooptic filters in tunable laser resonators are analyzed. It is shown that the observed deviation of the Al2O3:Ti3+ laser tuning characteristics from a linear dependence on the voltage across the filter is due to a combination of two factors: the wavelength dependence of the active medium gain and the width of the filter transmission band.

A study was made of the possibility of using thermal sensitization of a silver halide photographic emulsion for recording YAG:Er3+ laser radiation (λ = 2.94 μm). Using an FT-101 photographic film it was possible to record the radiation down to energy densities of ~ 1 mJ/cm2 in a dynamic range of ~ 100 with a resolution of at least 50 lines/mm when the laser pulse duration was ~ 150 μsec. This method was employed to determine for the first time the spectral width of a line emitted by a YAG:Er3+ laser operating in the free-running regime.

An analysis was made of a new configuration of a laser utilizing the 4I11/2–4I11/2 transition in the Er3+ ions in YAG with a high activator concentration (~5×1021cm−3). It is shown that at a certain excitation rate the cross-relaxation processes increase considerably the lasing efficiency and make it possible to achieve cw emission as a result of transitions from a long-lived lower level.

Measurements were made of the ratio of the luminescence energies represented by the 4I11/2–4I13/2 and 4I11/2–4I15/2 transitions in Er3+ ions in (Y1–xErx)3Al5O12 crystals. The Einstein coefficients of these transitions were also determined. The cross section of the 4I11/2–4I13/2 (X2–Y6) stimulated emission transition was measured. The concentration dependences of the absolute quantum efficiencies of the luminescence from the 4I11/2 and 4I13/2 levels were obtained.

The development of a pulsed Y3Al5O12:Er3+ laser (4I11/2–4I13/2 transition, λ = 2.94 μ) with activator concentrations of 30 wt.% (T = 300 °K) is reported. A pulse repetition frequency of f = 20 Hz was obtained under free-oscillation and Q-switched conditions. Stimulated emission due to this transition at T = 300 °K was obtained over the whole concentration series of the Y3Al5O12–Er3Al5O12 system with Er3+ concentrations of between 10 and 100 wt.%.

An electrooptic LiNbO3 filter is used for tuning free running oscillation (720-900 nm) and giant pulses (760-820 nm) of a flash lamp pumped Ti:A12O3 laser. The tuning laser characteristics and the peculiarities of electrooptic filters application in tunable laser resonators are analyzed.

The advent of effective solid-state pulse lasers operating in the 3-pm range [1, 2] that became available during the last ten years sets forth the problem of designing methods of registration and visualization of laser radiation within this range. Today, a researcher may choose from a good number of IR radiation visualization techniques resting upon the effect of a change of properties in various materials under the influence of heat [3]. In terms of such indicators as sensitivity, dynamic range, resolution, as well as a number of operational characteristics, the "thermal sensitization" technique applied to silver-halide photoemulsions [4] is far superior to any other available technique for visualization of IR radiation pulsed laser fields. This technique has been originally applied to photoregistration of pulsed gas laser radiation in the range of 5 and 10 pm. This paper presents the results of the experimental study of the potential of the method for registration of a YAG:Er3+ laser radiation at λ = 2.94 μm. The following parameters were determined: sensitivity, 2 mJ/cm2; dynamic range, 100; resolution with the generation pulse duration of 200 μs, not worse than 50 lines/mm.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The method of adiabatic pulsed laser calorimetry is considered. It is shown that this method of determination of the volume absorption coefficient of optical materials heated by laser pulses of different duration makes it possible to find the dimensions of submicron defects and to analyze the nature of nonlinear absorption without damage to the optical material.

Lasing was induced in Y1.5Er1.5Al5O12 (λ = 2.94 μm) crystals by selective pumping of the electronic–vibrational wing of the 4I15/2–4I13/2 transition. A population inversion was established in this YAG:Er3+ laser by a strong interaction between the excited Er3+ ions at the 4I13/2 level and the transfer of energy from the lower active level to the upper one in accordance with the 4I13/2–4I9/2, 4I13/2–4I15/2 scheme.

An investigation was made of electrooptic modulation of the Q factor of a resonator of a titanium-activated corundum laser. One electrooptic switch was used to achieve continuous tuning (in the range 760–820 nm) of the wavelength of the giant pulses generated in the Al2O3:Ti laser. The energy of the giant pulses was 10–30 mJ and their duration was 50–70 ns.

Experimental and theoretical studies demonstrated that steady-state emission was possible from an YAG:Er3+ laser utilizing the self-terminating 4I11/2–4I13/2 transition with a cross-relaxing lower level (4I13/2)