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The transfer of energy from Tm3+ to Ho3+ ions and also the interaction between excited Tm3+ ions and excited Tm3+ and Ho3+ ions in YSGG:Cr3+:Tm3+:Ho3+ and YSGG:Cr3+:Tm3+ crystals were studied quantitatively. The influence of these processes on the operation of two-micron lasers was analyzed.

Highly efficient nonradiative energy transfer from Ce3+ to Er3+ was observed in a YAG:Ce3+:Er3+ crystal. The experiments showed that the excitation of the 4S3/2 level was converted into a population inversion between the active Stark sublevels of the 4I11/2 and 4I13/2 levels characterized by the maximum efficiency in a YAG crystal. Quenching of the 4I11/2 level of the Er3+ ion by the Ce3+ anions in YAG:Ce3+:Er3+ was slight. The contribution of the Ce3+ ions to the population of the active levels of the Er3+ ions in YAG:Ce3+:Er3+ was 15–20%.

An unconventional system for the excitation of crystals activated with Tm3+ and Er3+ ions was proposed and implemented experimentally. This eliminated the need for any direct interaction between the external electromagnetic field and ions in the ground energy state. It was shown that efficient filling of unstable states of these ions may be achieved as a result of the absorption of photons due to a transition from an excited state and subsequent cross relaxation of the excitation.

An investigation was made of the influence of short-wavelength pump radiation on the spectral and luminescence characteristics of GSGG:Cr3+:Nd3+ and GSAG:Cr3+:Nd3+ crystals. A sensitive system was developed for measurement of the induced absorption based on multipass probing of a crystal by laser radiation. Dependences of the induced absorption on the excitation energy and the lifetimes of the photoinduced color centers were determined and the influence of the induced absorption on the pumping efficiency of the laser active element was studied. It was established that the intensity of the photoinduced absorption in a GSAG:Cr3+:Nd3+ crystal was substantially lower than that in a GSGG:Cr3+:Nd3+ crystal. It was shown that the induced absorption reduces the efficiency of filling of the 4F3/2 upper active level of the Nd3+ ion.

The influence of the spectral composition of the pump radiation on the spectral luminescence and lasing characteristics of YSGG:Cr3+:Tm3+:Ho3+ (λlas = 2.088 μm) and GSAG:Cr3+:Tm3+:Ho3+ (λlas = 2.095 μm) crystals was studied. It was found that the GSAG:Cr3+:Tm3+:Ho3+ crystal exhibited good optical strength in the ultraviolet, so that a broad spectral range of the pump radiation could be utilized. This factor, combined with good thermophysical properties, should make this crystal a suitable active medium of efficient two-micron holmium lasers operated as a high pulse repetition frequency.

An investigation was made of the influence of the spectral composition of the exciting light on the lasing and spectral-luminescence characteristics of a YAlO3:Nd3+ crystal. The spectral and relaxation characteristics of the photoinduced absorption, associated with the formation of color centers in the crystal, were determined. The induced absorption could increase the evolution of heat in the active element, but it did not influence the efficiency of filling the upper active level 4F3/2 of the Nd3+ ion. The mechanism responsible for the reduction in the lasing efficiency of the YAlO3:Nd3+ crystal in the presence of an ultraviolet component in the pump radiation spectrum was identified.

An experimental investigation was made of the influence of interaction processes involving excited Er3+ ions on the stimulated emission characteristics of a 3-μm yttrium scandium gallium garnet (YSGG:Cr3+:Er3+) crystal laser pumped by a krypton laser. The results are explained using a spectroscopic model of this crystal.

An investigation was made of the luminescence spectra and lasing parameters of a YSGG:Cr3+:Tm3+ crystal. An active element 3 mm in diameter and 54 mm long was flashlamp-pumped (at T = 300 K) and its differential efficiency was 1% (λlas = 2.018 μm, 3H 4→3H 6 transition in Tm3+).

An experimental investigation was made of multispike lasing regimes in various pulsed Nd3+ lasers Q-switched using a movable passive switch based on an yttrium scandium gallium garnet crystal containing Cr4+ ions. The results indicate that these passive switches should make it possible to develop Nd3+ lasers with high average and peak powers.

Efficiencies of ~ 1.5–2% were achieved in YSGG:Cr:Nd lasers utilizing resonators insensitive to thermal birefringence in the active element under conditions of frequency doubling in a KTP crystal. The pulse output energies were 400 (240) mJ and the pulse repetition frequencies were 25 (50) Hz. Prospects for further improvement in the output parameters of these lasers were demonstrated.

A fiber amplifier containing a waveguide activated with Er3+ ions was used for the first time to reduce the losses and thus improve the resolving power of a fiber Michelson interferometer. An interferometer with a path difference between the arms amounting to 5 km was constructed and the losses in this interferometer were fully compensated by the use of such an amplifier.

A flashlamp-pumped Q-switched pulsed laser utilizing yttrium scandium gallium garnet activated with Cr and Nd was developed. This had an efficiency of 4% and a pulse energy of 450 mJ. The laser design featured an optomechanical modulator based on the frustrated total internal reflection of light, and an illumination enclosure having a special configuration which ensured spatial averaging of the gain distribution over the cross section of the active element. An analysis was made of the conditions for maximization of the lasing efficiency as a function of the resonator parameters.

Single-mode fiber waveguides were used in constructing a Michelson interferometer with a 50-km difference between its arm lengths. An analysis was made of its resolving power as a function of the parameters of the optical part and of the characteristics of the electronic apparatus used in the system. The width of a spectral emission line of a semiconductor laser with a distributed Rayleigh fiber resonator was determined.

Suppression of amplified spontaneous emission and a 1.5-fold increase in the energy efficiency were achieved in YSGG:Cr3+:Nd3+ crystals when saturable Cr centers absorbing at a wavelength of 1.06 μm were formed.

Single crystals of gadolinium vanadate doped with neodymium ions have been grown by the Czochralski method. The absorption and luminescence spectra of the neodymium have been measured. The absorption near 0.8 μm is higher than 70 cm−1. The lifetime of the neodymium ions is 90 μs. Laser action has been achieved on the transitions 4F3/2 → 4I13/2, 4I11/2. The differential efficiency of the lasing near 1.06 μm is 54%.

Stable single-frequency generation of short (2 ns) radiation pulses in a YAG:Nd laser was achieved by using a passive Q switch made of a GSGG:Cr3+:Cr4+:Nd3+ crystal.

An investigation was made of the propagation of subnanosecond light pulses through a system of coupled channel waveguides formed in a potassium titanyl phosphate (KTP) crystal. An increase in the input signal to 5 kW resulted in a nonlinear transfer of 40% of the optical power from one channel to another.

The dependence of the output power Pout, on the incident power Pin reaching the end of a waveguide was investigated for a channel waveguide made of Rb-activated potassium titanyl phosphate (KTP) at λ = 514 μm. This dependence was linear in the range Pout = 0–450 mW. When the power density at the entry to the waveguide reached 10 MW/cm2, optical damage to the crystal was observed in the form of a surface crater.

A method for the fabrication of volume phase diffraction gratings in a KTP (potassium titanyl phosphate) crystal was developed. Gratings with a period of 5 μm and a depth of 150 μm were obtained. A study was made of the characteristics of these gratings. The diffraction efficiency was found to depend on the direction of the plane of polarization of the incident beam relative to the grating lines. The Bragg diffraction of light characterized by rotation of the plane of polarization by 90° was observed.

A method for improving the homogeneity of the distribution of the intensity of the output radiation from lasers by spatial averaging of the gain over the cross section of the active element is proposed. This method utilizes a laser head in which the active element and the flashlamp inside a reflecting illumination enclosure are tilted. The local intensity maxima in the cross section of the output radiation beams of YSGG:Cr:Nd and YAG:Nd crystal lasers can be reduced considerably by this method.

A description is given of laser resonators that ensure a highly efficient method for generation of linearly polarized radiation with a homogeneous distribution across a beam when a strong thermally induced birefringence is established in an active element. It is reported that single pulses of 240 mJ energy with a repetition frequency up to 100 Hz were generated in a YAG:Nd laser and the efficiency of the process was 1.4%.

The optical characteristics of channel waveguides made of rubidium-activated potassium titanyl phosphate (KTP:Rb) were determined. The refractive index increment of such waveguides was found to exhibit a considerable anisotropy: Δnx / Δnz ≈ 2. A deviation of the distribution of the refractive index in a channel waveguide from the model distribution was observed for ion-exchange times in excess of 1 h.

Diffused planar waveguides were formed in a potassium titanyl phosphate (KTP) crystal by ion exchange with molten RbNO3. The optical strength was determined at the wavelengths of 0.488 and 0.514 μm. The cost of Rb:KTP waveguides was at least two orders of magnitude less than planar Ti:LiNbO3 waveguides.

A wedge-shaped phase plate was used in a laser resonator to improve the homogeneity of the intensity distribution over the cross section of the output beam from a YSGG:Cr:Nd laser using polarization coupling out of radiation, operated under conditions of a strong induced thermal birefringence in the active element. The local intensity maxima were then approximately halved compared with those using a quarter-wave phase plate in the resonator.