The spatial, temporal, and spectral characteristics of the output radiation of diode-pumped laser systems and optical amplifiers with active elements made of Nd : YAG ceramics are studied. It is shown that the divergence of radiation in the subthreshold regime has the form of concentric nested cones emerging from the active element (AE) faces at angles of 2 – 4 °. A model explaining the experimentally observed phenomenon is proposed based on the mechanism of scattering of the generated beam from the granular structure of the optical ceramics. Analysis of the divergence pattern makes it possible to estimate the grain size and the optical quality of ceramics. The output beam divergence in the lasing regime is determined mainly by the cavity parameters and does not exceed several milliradians. The scattering events in this case serve as sources of additional optical losses. Luminescence enhancement and parasitic oscillations in the AE volume restrict the possibility of using Nd : YAG ceramics for fabricating AEs of high-power optical amplifiers.

Operating regimes of an optical system consisting of a compact pulsed master diode-pumped Q-switched Nd:YAG laser and triple-crystal (KTP) ring cell of an optical parametric oscillator have been investigated. It was experimentally shown that the frequency-selective properties of a passive Q-switched unit in natural mode selection are enhanced by creating a Lyot polarization interference filter with the phase plate in the form of a laser active element with thermally induced birefringence and a polarizer. Such Lyot filter appears in the Nd:YAG laser cavity during operation at relatively high energy and repetition rate of radiation pulses (60–100 mJ, 20 Hz). The combined action of the natural mode selection process and the Lyot filter ensures stable operation of a passive Q-switched Ng:YAG laser in single-frequency lasing mode (the lasing bandwidth is <57 MHz). The master single-frequency pulsed Nd:YAG laser (λ = 1.06 μm) allows the energy of pulses applied to the input of the optical parametric oscillator to be reduced by greater than 1.5 times while maintaining the specified energy level of the output pulses (30 mJ, λ = 1.57 μm). An additional increase in the efficiency of the optical parametric oscillator conversion is achieved by introducing a two-lens 1.3× telescope into the master laser cavity.

We investigated the conditions for forming the single-frequency monopulse operation mode of the transversally diode pumped Yb,Er-phosphate glass laser with a passive Q-switch based on the Co 2 + :MgAl 2 O 4 crystal. It was shown experimentally that the spectral selectivity that ensures the stable single-frequency operation for the Yb,Er-laser is achieved in the intracavity Fabry–Perot interferometer in the form of the totally reflecting mirror and nearest end surface of an active element with plane-parallel faces, as well as the polarization interference filter (PIF, Lyot filter). Meanwhile, the PIF created by an active element with thermally induced anisotropy and a polarizer in the form of a passive Q-switch plate, oriented at Brewster’s angle to the resonator axis, acts as a preliminary spectral selector. The maximum energy of the formed output laser pulses was 6 mJ with a duration of 20.2 ns, a repetition rate of 1 Hz, and a singlefrequency lasing spectrum width of 41 MHz.

We investigated the conditions for forming the single-frequency monopulse operation mode of the transversally diode pumped Yb,Er-phosphate glass laser with a passive Q-switch based on the Co 2+ :MgAl 2 O 4 crystal. It was shown experimentally that the spectral selectivity that ensures the stable single-frequency operation for the Yb,Er-laser is achieved in the intracavity Fabry–Perot interferometer in the form of the totally reflecting mirror and nearest end surface of an active element with plane-parallel faces, as well as the polarization interference filter (PIF, Lyot filter). Meanwhile, the PIF created by an active element with thermally induced anisotropy and a polarizer in the form of a passive Q-switch plate, oriented at Brewster’s angle to the resonator axis, acts as a preliminary spectral selector. The maximum energy of the formed output laser pulses was 6 mJ with a duration of 20.2 ns, a repetition rate of 1 Hz, and a single-frequency lasing spectrum width of 41 MHz.

We studied the thermo-optic properties of diode-pumped high-power pulsed ceramic- and crystalline-activeelement Nd:YAG lasers with neodymium ion concentrations of 2.0 and 1.1 at. %, respectively. We showed that under comparable excitation conditions, the mean heat generation from the ceramic Nd:YAG active element is 30%-35% higher than that from the crystalline Nd:YAG active element. The difference in thermal power is apparent from the energy of the polarized output laser pulses as a function of frequency. A quarter-wave plate partially compensates for thermally induced birefringence. This technique was found to be effective up to maximum frequencies of 50 and 70 Hz, for the ceramic and crystalline active elements, respectively. (C) 2020 Optical Society of America

The optical losses introduced into the cavity of transversally diode pumped Nd:YAG lasers operating in the linearly polarized Q-switched mode by the induced birefringence were evaluated. The relationship between the loss values and the state of the side surface of laser active elements was established. It has been shown that the active elements with adhesive light-scattering layers on their side surfaces make it possible to create the laser sources not only with a high degree of uniformity of the distribution of radiation within the output beam cross-section, but also with a low level of the optical depolarization losses.

The formation features of the single-frequency unidirectional monopulse lasing mode of a Nd:YAG laser with a triple-mirror ring cavity and a side diode-pump with injection of external narrow-band optical radiation into the cavity are studied. The asymmetric layout of the intracavity elements relative to the output mirror and depolarization effects in them cause the energy and polarization of the monopulse Nd:YAG ring laser to differ depending on the input direction (clockwise or counterclockwise) of the injected radiation. The difference in the output characteristics of the single-frequency unidirectional monopulse Nd:YAG ring laser is most evident for a change from active to passive Q-switching.

The formation features of the regime of single-frequency unidirectional monopulse lasing of Nd:YAG laser with a triple-mirror ring cavity and a side diode-pump under the condition of injection of external narrow-band optical radiation into the resonator are studied. It is experimentally shown that the asymmetrical layout of the intracavity elements relative to the laser output mirror and the depolarization effects in these elements lead to a difference in the energy and polarization of the monopulse Nd:YAG ring laser depending on the direction (clockwise or anticlockwise) of the input of the injected radiation. The difference in the output characteristics of the single-frequency unidirectional monopulse Nd:YAG ring laser is the most evident in the case of transition from the active to the passive Q-switching.

Temperature effects on photoluminescence and absorption spectra of the active medium (LGS-DE erbium phosphate glass) and passive Q-switch (MgAl2O4:Co2+ crystal) of a diode-side pumped Yb,Er-laser are studied. The obtained data are applied to an analysis of the spectral and energetic characteristics of compact erbium emitters. It is established that the dominant generation channel in the temperature range 233–328 K is the optical transition between lower Stark sublevels of Er3+ states 4I13/2 and 4I15/2 (λ = 1532.0–1533.9 nm). A rate-equation system taking into account thermal population of Stark sublevels of states 4I13/2 and 4I15/2 is proposed to describe the experimental temperature dependence of the threshold absorbed power of the pumping radiation. This system and the lasing threshold enable modeling of Yb,Er-emitter output energetic and temporal characteristics.

A model system of two differential rate equations is proposed to describe the temporal characteristics of the radiation of a solid-state laser with high-energy pumping. Using a laser head with a YAG:Nd active element and a side-pumped laser diode array unit as an example, a method is discussed of determining the excitation levels of the active elements at which the amplified luminescence and the nonaxial (stray) lasing modes begin to manifest themselves in the output radiation dynamics all the way to the limitation of the maximum pulse energy generated by a solid-state laser in the Q-switched regime. The proposed approach to analyzing the role of the processes associated with the formation and evolution of amplified luminescence fluxes and nonaxial (stray) lasing modes in the active media can also be applied to other types of laser radiators.

An optical scheme of an optical parametric oscillator with a master laser based on an Nd : KGW active element excited by two orthogonally oriented diode side pump modules is proposed to form radiation pulses with energies above 30 mJ and a repetition rate of 1 – 20 Hz in the eye-safe spectral range of 1.5 – 1.6 μm. The two-module excitation of the active medium makes the distribution of the master laser radiation intensity in the output beam cross section more uniform and provides a reliable operation of the optical parametric oscillator.

The feasibility of using light-emitting devices, the radiation spectrum of which has maxima at wavelengths of 1.7, 1.9, and 2.2 μm for determining the water concentration in oil and oil products (gasoline, kerosene, diesel fuel) has been demonstrated. It has been found that the measurement error can be lowered if (i) the temperature of the light-emitting diode is maintained accurate to 0.5–1.0°C, (ii) by using a cell through which a permanently stirred analyte is pumped, and (iii) by selecting the repetition rate of radiation pulses from the light-emitting diodes according to the averaging time. A meter of water content in oil and oil products has been developed that is built around IR light-emitting device–photodiode optrons. This device provides water content on-line monitoring accurate to 1.5%.

Compact eye-safe pulsed optical parametrical oscillator based on Nd:KGW laser with two orthogonal diode pump modules has been developed. The oscillator is characterized by output energy at 1.57 μm in excess of 30 mJ and the pulse repetition rate up to 20 Hz.

A system of balance equations is used to calculate the time (t) dependence of the intensity (I) of the output of a Nd:YAG laser rod from the time a pump pulse is applied for different levels of excitation of the rod by arrays of laser diodes (transverse pump configuration). Comparison of the calculations with experimental data shows that an analysis of the I(t) curves can be used to determine the contributions of amplified luminescence and parasitic lasing modes, which do not leave the volume of the active medium, to the overall loss of pump radiation energy. The model approach developed here can be used to evaluate the quality of the active media in diode-pumped solid-state lasers.

The spectral characteristics of light emitting diodes based on a InAs/InAsSb/InAsSbP heterostructure, which emit in a wavelength range of 3.5–4.5 µm, are investigated experimentally. It is shown that the temperature shift of the maximum emission wavelength of a light emitting diode in the temperature range 80–313 K is 1.8 nm/K. The temperature dependence of the band gap of the InAs0.88Sb0.12 active layer is described by the Varshni formula with the characteristic parameters: Eg0 = 0.326 eV, a = 2.917 × 10–4 eV/K, and ß = 168.83 K. The results of our measurements of the concentrations of carbon dioxide (CO2) using the studied light emitting diodes show the possibility of the reliable detection of CO2 in the concentration range 300–100000 ppm.

A method of modelling the conditions for side pumping a passively Q-switched erbium laser with linear laser-diode arrays is proposed that makes it possible to determine the most efficient geometry for the placement of the linear arrays relative to the active element, taking into account the characteristics of not only the diode arrays and the active element, but also of the optical cavity that is used. The results of the modelling make it possible to choose the distance between the linear arrays and the active element and the allowable shift of the linear arrays relative to each other, and this optimizes the matching of the excitation and lasing conditions. The proposed optimization method takes into account the divergence and polarization of the radiation of the diode arrays, the geometrical and optical properties of the active element, and the configuration of the lasing mode. The theoretical results of the modelling are compared with the experimental data. (C) 2015 Optical Society of America.

The work is devoted to the development and creation of the powerful all solid-state air-cooled multiwave Nd:YAG laser integrated with the output telescope system and to the development of the LD-pumped solid-state source with the extremely narrow lasing linewidth. The laser sources are meant for operation with the multiwave aerosol LIDAR (atmosphere probing altitude is up to 40 km).

An all-solid-state multiwave laser radiator (lasing wavelengths 1064, 532, and 355 nm), integrated in a single implement with a telescope, has been developed for use in aerosol lidars. The main radiator is the master laser and an amplifier based on a YAG:Nd crystal, excited by laser diode arrays using a transverse pumping layout. In the Q-switched regime, the energy of the output pulses of the YAG:Nd laser radiator reaches 400 mJ (1064 nm). With simultaneous lasing at three wavelengths, the radiator forms radiation pulses at 1064, 532, and 355 nm, with energies of 170, 150, and 80 mJ, respectively. The pulse width is 8-11 ns at a repetition rate of 10 Hz. The developed multiwave laser radiator is effective for use as a component of aerosol lidars with an atmospheric probing range of up to 40 km. (C) 2014 Optical Society of America.