Table of contents

Diode laser pumping was used to excite for the first time single-mode cw lasing of Nd³⁺ ions (⁴F_3/2→⁴I_11/2 transition at 300 K) in disordered fluoride crystals (CaF₂–YF₃, SrF₂–GdF₃, BaF₂–YF₃, and BaF₂–LaF₃).

A new efficient flashlamp-pumped pulsed solid-state laser utilizing disordered Ca₂Ga₂SiO₇:Nd³⁺ crystals (⁴F_3/2→⁴I_11/2 lasing transition) was developed and studied.

An analysis is made of the state of the art of x-ray lithography and x-ray optics. The principles of design and configurations of projection x-ray lithographic systems are considered. An analysis is made of the main trends of research on these topics proceeding in the laboratories in the Soviet Union, USA, Japan, and Great Britain. The problems encountered in the development of multilayer normal-incidence x-ray mirrors are described.

An investigation was made of the current-voltage characteristics of injection lasers with isoperiodic PbSnSeTe layers and of double-heterostructure lasers with a controlled carrier-density profile, based on lead selenide. The investigation was carried out in the temperature range 20–80 K. The methods used in the fabrication of lasers and in measurements under pulsed conditions are described. It is shown that at 20 K the tunnel component of the current becomes important. An increase in temperature increases the role of the thermal current and already at 80 K the diffusion component becomes the dominant one. The tunnel component of the threshold current at 80 K is ∼0.25.

An analysis is made of the model of a single-mode semiconductor injection laser with a feedback loop based on amplitude fluctuations. It is shown that radiation in the sub-Poisson photon statistics can be coupled out from such a laser if a second laser-resonator mirror, which is not in the feedback loop, is used as the exit mirror.

The results are presented of an experimental investigation of injection locking in an XeCl laser with output energies of 30–40 J in a 300-ns pulse, using a 100-ns external signal pulse with a 0.2-cm⁻¹ line width and an energy of 10 mJ. When the axial region of an unstable resonator was filled by the external signal from the start of pumping to the attainment of the lasing threshold, 90% of the lasing energy was concentrated in the injected line.

The results are presented of investigations, performed in 1965–1966, of a pulsed photodissociation iodine laser utilizing CF₃I and C₃F₇I molecules and pumped by light from a shock front created by detonating an explosive charge. Such lasers were found to possess a unique combination of high output energy and high pulse power. Two types of laser were studied. In one of them the active medium was pumped by light from a shock wave in xenon, and in the other a shock wave propagated through a mixture of the active medium and a rare gas. The energy characteristics of the second type of laser were found to be considerably higher than those of the first type. The laser pulse radiation enegy reached ∼100 J with an average power of ∼15 MW.

For the first time, nine emission lines in the 303–545 μm range were obtained from a submillimeter laser utilizing CD₃COND₂ molecules and five emission lines in the 86-973 μm range were obtained utilizing ND₂CD₂COOD molecules pumped optically by a cw tunable CO₂ laser. Data on the wavelengths, the relative intensity, and the polarization of the emission lines are presented.

Temporal characteristics of a Cr–Yb–Er glass laser are presented. Pulses of 13 ps duration were obtained in the 1.54 μm range by active mode locking with a highly efficient LiNbO₃ crystal modulator.

A new solid-state YAG ring laser system with an acoustooptic nonreciprocal element was investigated experimentally and theoretically. Stable single-frequency lasing with an output power of ∼ 1 W was achieved.

Optimization of the technology of fabrication of active LiF (F₂→F₂⁺) laser elements operating at room temperature ensured high parameters of broad-band emission of light by the F₂ and F₂⁺ color centers in a nonselective resonator pumped by the second harmonic of a pulse-periodic YAG:Nd³⁺ laser (λ = 0.532 μm). The efficiency of the LiF (F₂→F₂⁺) laser, expressed in terms of the pumping, was 38%, whereas in terms of the absorbed energy it was 41%. The service life of one pump channel of the LiF (F₂→F₂⁺) laser exceeded 5 × 10⁵ pulses when the pump radiation power density was 150 MW/cm² and the diameter of the active channel was d = 1.5 mm. Broad-band lasing of the F₂ color centers in the same system, but without focusing of the pump radiation, was observed for a period of 15 min at a pulse repetition frequency 12.5 Hz when the pump power density was 40 MW/cm².

Studies of spontaneous radiation and lasing, measurements of the electron density and temperature, and also an analysis of the rates of various processes in mixtures of helium, neon, and argon with NF₃ (pumped by a self-sustained discharge) were used to show that, under conditions of lasing due to atomic transitions in rare gases, the upper active level is filled by electronic excitation processes and the lasing pulse duration in the afterglow is limited by ion-ion recombination.

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.

A four-wave interaction is analyzed in a loop system based on stimulated Brillouin scattering with an amplifier in the feedback loop. It is shown that at inadequate input intensities, the appearance of higher Stokes components in the reflected wave spectrum reduces the reflection coefficient of the system and also the efficiency of energy coupling-out from the amplifier. Radiation having an intensity comparable to the threshold intensity of a phase-conjugation device with a double-pass amplifier must be coupled into the system to achieve good parameters.

The influence of the composition of the active medium on the lasing characteristics and energy deposition efficiency was studied under conditions of electron-beam and electric-discharge initiation in SF₆–H₂ and SF₆–HI pulsed hydrogen fluoride chemical lasers.The best radiation energy characteristics were achieved for an SF₆–HI active medium using electron-beam initiation and for an SF₆–H₂ active medium when the pump reaction was initiated by a self-sustained volume discharge. The following pulse parameters were obtained for an SF₆–HI laser:energy 1.5 J, half-height pulse duration 60 ns,and leading edge duration 20 ns.

An investigation demonstrated the feasibility of amplification of a weak seed Stokes radiation generated by concurrent and counterpropagating stimulated Raman scattering in a barium nitrate crystal. The subsequent amplification took place in a crystal of LiF containing color centers, which made it possible to achieve a high efficiency of conversion of the pump energy into the energy of the Stokes radiation without focusing the pump beam.

It is shown that Monte Carlo simulation of the glass structure (i.e., of the radial distribution function of rare-earth ions in the glass) can explain the "anomalous" behavior of the rate of quenching of the activator and/or sensitizer luminescence as a function of its concentration in laser oxide glasses. The results of the simulation can be used to search specifically for compositions of new efficient laser glasses.

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 ⁴S_3/2 level was converted into a population inversion between the active Stark sublevels of the ⁴I_11/2 and ⁴I_13/2 levels characterized by the maximum efficiency in a YAG crystal. Quenching of the ⁴I_11/2 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%.

Expressions are derived for the calculation of the optical lengths of arms and their components in the case of a planar misaligned ring resonator containing plane-parallel plates. The expressions are valid in the first order in terms of linear and angular displacements of the resonator mirrors.

A modified Magni procedure is used in a numerical analysis of dynamically stable resonators with an internal focusing element. Calculations are reported of the dependences of the maximum volume occupied by the TEM₀₀ mode in the active element, of the width of the stability zone, and of the geometric parameters of the resonator ensuring the maximum volume of the fundamental mode on the focal length (divided by the resonator length) of an induced thermal lens in the middle of the stability zone. An experimental procedure for constructing dynamically stable resonators allowing for real sources of instabilities in continuously pumped laser systems is proposed and the results of experimental tests are reported. These tests show that resonators with the stability zone width considerably greater than the astigmatism of the induced thermal lens can ensure both a spatially homogeneous profile and a minimum instability of the laser radiation, which in practice does not exceed the initial instability of the pump radiation.

A cooled copper adaptive mirror based on a double bimorph structure is proposed for the compensation of large-scale optical aberrations, including those that occur in power systems with an output up to 15 kW. The construction of the adaptive mirror is described and the results are given of calculations and of experimental studies of thermal deformations of the reflecting surface, of the response functions of the control electrodes, and of the frequency properties of the mirror. Estimates are obtained of the effectiveness of compensation of low-order optical aberrations.

A new class of mirrors with a super-Gaussian reflection coefficient distribution was investigated. A technique was developed for fabricating such mirrors in a standard evaporation apparatus. The efficiency of a YAG:Nd³⁺ laser utilizing such mirrors was demonstrated.

A new method for the determination of the parameters of channel integrated optical waveguides is proposed. This method is based on measuring the spectral transmission of a system comprising the investigated waveguide and single-mode fiber waveguides, which are brought into contact with the channel waveguide. The results are reported of an investigation of two channel waveguides formed in glass by a variety of methods and characterized by different refractive index profiles. The proposed method is found to be suitable for determination of the parameters of the refractive index profile of the investigated channel waveguides.

An analysis is made of the process of light emission from a corrugated waveguide into air and into a substrate in a noncollinear geometry, i.e., when the direction along which the waveguide mode propagates does not coincide with the plane in which the emitted wave lies. Calculations show that when a TE mode is excited in a corrugated waveguide by a light beam with the TM polarization incident from air on the waveguide at a grazing angle, one can achieve a high waveguide excitation efficiency (∼ 60%) if the waveguide mode propagates along the normal to the plane of incidence.

A passive ring resonator based on channel waveguides, formed in a K8 glass substrate by diffusion ion exchange in molten potassium nitrate, was made and investigated. The waveguide structure of the resonator included a ring waveguide as well as two Y-type couplers, whose symmetric arms were coupled to the ring waveguide, whereas homogeneous arms were coupled to an external laser and a photodetector. The coupling of the external devices to the channel waveguides was implemented by prisms and butt (end face) contacts. The transfer function of the ring resonator was determined experimentally in order to illustrate its resonant properties and sharpness. Estimates were obtained of the ultimate sensitivity of an optical gyroscope utilizing a ring resonator with the properties described above and ways of improving this sensitivity were analyzed.

A theoretical design of a universal compact fiber-optic compressor based on a monochromator with a spherical mirror in the plane of its exit slit was considered. Ultrashort pulses emitted by an actively mode-locked YAG:Nd³⁺ laser, whose spectrum was broadened in a fiber-optic waveguide, were compressed experimentally to 2.7 ns. A universal compact compressor was developed: it produced 4-ns pulses with an average radiation power of about 1 W. The dimensions of this compressor were several times smaller than those of a traditional scheme using a diffraction grating to compress pulses having an initial duration of about 100 ns.

An analysis is made of a theoretical model of an interference fiber channel for transmission of microwave signals. It is assumed that the channel consists of a multimode fiber waveguide with a step or graded refractive-index profile. A typical statistic of a longitudinal distribution of inhomogeneities is also assumed. Calculations are reported of the interference losses, the spectral profile of the output radio signal, the signal/noise ratio in the channel, and of the dependences of these parameters on: the type, diameter, and the length of the multimode fiber waveguide; the spectral width of the radiation source; the frequency offset between the interfering optical signals.

A numerical method was used to investigate the emission of TE-polarized light from a graded-index corrugated waveguide coated with a metal or semiconductor and either with or without a buffer layer. The main emission characteristics of these systems were analyzed. In the case of metallized dielectric structures an optimal corrugation depth was established for which the emitted power is a maximum. It was found that when the parameters of a structure with a buffer layer were correctly chosen and a highly reflective metal coating was used, practically all the power in the waveguide wave could be emitted along a specified direction. A structure with a buffer layer and an aluminum coating was investigated experimentally.