In recent years reports on very interesting media showing unusual optical properties have appeared in literature on atomic physics. The source of these properties is quantum interference revealed in the process of interaction of atoms with coherent light. The basis of this process is the fact that if there are at least two possibilities of realization of the process of absorption or emission of light in a given medium leading to the same final state, they interfere with each other. The result of the interference depends on relative phases of the interfering processes. However, for the interference to be observable the above phases must be well determined. The phase coherence of the medium is thus a condition necessary for obtaining the optical properties characteristic of quantum interference. This fact has been underlined by the name phaseonium given to these media by Marlan O. Scully. Recently observed unusual optical properties of a phase-coherent atomic medium (phaseonium) is explained using very simple models.

X-ray lasers are currently being studied in many laboratories around the world. This paper gives a short description of x- ray laser physics, presents the parameters of existing x-ray lasers, and their applications. Research aimed at developing an efficient x-ray laser acceptable to potential users is discussed. A new method to produce an x-ray laser active medium using a laser-irradiated gas puff target is presented in the final part of the paper.

The paper presents the main directions of investigations as well as possibilities of new materials applications for solid state laser systems with coherent pumping. The fundamental physico-structural properties of active mediums, materials for frequency conversion systems and non-linear absorbers for passive Q-switching resonator are discussed. The literature data are compared with the results of investigations carried on in the Institute of Optoelectronics MUT in the field of materials engineering, spectroscopy, structural analysis and lasing characteristics of different, coherent pumped laser systems.

The influence of active media parameters on generation characteristic of microlasers is reported. Absorption bands of several laser crystals have been examined and the results are presented. Generation characteristics of the examined Nd:YAG, Nd:GGG, Nd:LSB and Nd:GLS microlasers with their single- frequency generation ranges are presented. The highest differential efficiency of 56% was obtained in Nd:YAG microlaser with 1 mm resonator length. The highest cw output power of a single TEM₀₀ mode equal to 60 mW was reached in Nd:YAG microlaser with 0.8 mm resonator. The lowest threshold of generation was formed for Nd:GGG microlaser. Continuous frequency tunability of the Nd:YAG laser within the range of 103 GHz and with sensitivity equal to 3.1 GHz/K was shown. The relationship between experimentally measured range of generation frequency tuning and output power of microlasers is presented.

The results of investigations of gamma radiation influence on laser performance of Nd:SLGO, Er:YAG and CTH:YAG crystals were reported. Twice and fourfold increase of optical output was stated for Er:YAG and Nd:SLGO, CTH:YAG lasers, respectively. The increase takes place due to color centers created by gamma quanta, that is due to additional absorption bands appearing in the crystals after gamma irradiation.

Excitation-mission spectra have been measured for Pr³⁺, Ce³⁺, Nd³⁺ and Eu³⁺ doped YAP, YAG, and SLGO crystals in room temperature. Results of additional absorption measurements and changes in a luminescence after gamma irradiation with dose up to 10⁵ Gy and energy of 2.5 MeV are also presented.

The paper presents the optical properties of glasses and optical fibers from quartz glass, obtained by the sol-gel method. A new technique of sol-gel glass preparation is described. Rods were formed from the glass thus produced from which PCS-type fibers were next drawn. Using the same sol-gel technology, the erbium-doped quartz glasses were obtained. The transmission and luminescence characteristics were measured for the glasses as well as for fibers drawn from them.

In our work we considered efficiency of pulse train generation in Q-switched lasers excited with rectangular pulses. It was proved that such a generation efficiency is significantly higher than efficiency of monopulses generation, especially for three-level lasers. For four-level lasers, an increase in efficiency of pulse train generation appears for the active materials for which depopulation time of the lower laser level is longer in comparison with generation time. Such efficiency increase is observed also for the Nd:YAG lasers. It was confirmed experimentally for diode pumped passive Q-switched Nd:YAG laser.

A novel, efficient method for generation of ultrashort pulses in short-gain-duration lasers is described and investigated numerically. The method employs fast mode locking accomplished by means of an electro-optic deflector. The possibilities of the method are demonstrated taking XeCl and KrF excimer lasers as an example. It is proved that, in contradistinction to conventional active mode locking (e.g., with an acousto-optic modulator), even at the gain duration as short as 50 - 100 ns, it is possible to obtain pulses shorter than 10^-11 s with this method using a sine-wave driven electro-optic deflector.

A semiclassical model of the nonlinear operation of the laser with Gaussian mirror (GMR) is presented. Nonlinear self- consistent equations including transverse and longitudinal field dependence, gain saturation, spatial hole burning and nonlinear dispersion effects are derived. With the help of energy theorem an approximate solution for steady state single mode operation is presented, which relate the small signal gain to the output power and the laser system characteristic parameters. Characteristics revealing the effects of system parameters are presented for various cavity configurations.

An approximate solution of the problem of the misalignment sensitivity in hollow waveguide resonator with Gaussian reflectivity mirror is presented. With the help of ABCD matrix laws an approximate expression which relate the coupling losses to the distance between end mirror and waveguide aperture, radius of mirror curvature, Gaussian mirror parameter and output mirror tilt angle is derived. Characteristics revealing the effects of resonator parameters on coupling losses are presented for various cavity configurations. It is shown, that using of Gaussian output mirror decreases resonator misalignment sensitivity.

The effect of the excess quantum noise on the light output properties of single mode Fabry-Perot laser is discussed. Using the stochastic approach based on the Fokker-Planck equation taking into account the full saturation effect, the exact analytic expressions of the mean output intensity and the variance of the output intensity of the laser mode are derived. Numerical results obtained for two-mirror laser reveal the influence of the excess noise on output power of the laser.

We analyze the influence of the resonator geometry on the correlation function of the amplitude that express the laser linewidth as well as the coherence of light and of the intensity fluctuations. The stochastic approach based on the solution of the time-dependent Fokker-Planck equation is used. Numerical results are obtained for segment Fabry-Perot and DFB lasers. In the analysis of DFB laser, the complex coupling coefficient as well as the nonvanishing end reflectivities are included.

An influence of the gain saturation effect and spatial hole burning effect on the dynamic operation of distributed feedback (DFB) lasers with the complex coupling coefficient is analyzed. The strong dependence of the nonlinear effects on the dynamic operation is shown for two different dielectric laser structures with the loss coupling and gain coupling.

A model of bistable operation of dielectric planar laser with one and two photon nonlinear absorber is presented. The equations of the small-signal gain coefficient for the planar structures with one and two photon nonlinear absorber are derived. Dependence of the waveguide width, transverse mode number, the saturation parameter and position of the active medium is discussed in detail.

In this work a problem of the nonlinear electromagnetic surface TM waves at a nonlinear interface is presented. There are given: solutions of Maxwell equations, solution of the dispersion equation and results for two media (medium 1 -- MBBA crystal, medium 2 -- YAG crystal). Dependences of the propagation constant (the electric field) and the power (the electric field) are shown in figures 1 - 3. Solutions of the equations can be applied in transmission of an optic signal, optical waveguides, polarization devices.

The delayed luminescence of the various glass and quartz plates as well as of deposited semiconducting and orientating layers was investigated. The shape of emitted delayed luminescence spectrum was different for various samples, but the intensity of this emission can not be neglected in the case of optical systems in which low intensity emission is investigated. Through the proper choice of the material and thickness of the plates, these perturbing effects can be diminished. The lowest delayed luminescence from investigated samples exhibits the quartz Suprasil SQ1. The delay luminescence is practically not diminished and the decrease in temperature from 295 K to 8 K shows that this emission is not generated with the participation of thermal energy.

The paper reports results of investigation of the phenomenon of optical orientation induced by a strong laser beam (optical field) in optically isotropic media. The mechanisms of the phenomenon are indicated and its statistical -- molecular theory is given. Investigation of the phenomenon of optical orientation can provide important information on transparent media allowing a determination of their local structure and microscopic parameters of molecules. This method is particularly useful in the studies of the character and strength of interactions in the gas phase in which these parameters can be easily controlled by changing the gas temperature and pressure. The apparatus used for measuring the effect is briefly described but the main attention has been paid to optical Kerr effect measurements in gases, in particular in carbon dioxide, which is highly suitable for these kinds of measurements as it is easy to study it in different phases and moreover in the vicinity of the critical point. Investigation of carbon dioxide in gas phase was performed in the nanosecond time domain and in a wide range of pressures and temperatures. A detailed interpretation of the results presented in tables and figures is given, and a new method for determination of the orientational relaxation time on optical Kerr effect measurements in the nanosecond time range, is proposed.

The paper reports results of the temperature studies of the optical Kerr effect in p-nitrotoluene and p-dichlorobenzene. The measurements were carried out in the temperature range from 330 to 360 K. The values of Kerr constants for both liquids were determined. The temperature dependence of the optical Kerr effect for p-nitrotoluene revealed deviations from the theoretical predictions which indicates the presence of strong dipolar interactions in this liquid, hindering optical orientation of its molecules.

The paper reports results of the optical Kerr effect investigation in the mixture of carbon disulphide and the air. Measurements were performed as a function of temperature and CS₂ concentration. Assuming the statistical-molecular theory of the optically induced birefringence, the values of the optical and molar Kerr constants as well as polarizability and optical anisotropy were found. The observed deviations of the temperature dependence of Kerr effect from the theoretical predictions indicate the presence of strong molecular interactions in the studied mixtures.

The interactions of laser beams with aqueous solutions of dodecylpiridinium chloride were investigated for different concentrations of the solute. The laser beams were characterized by the light wavelength in the range from 630 nm to 830 nm and by relatively low incident power covering the range 5 - 20 mW. The nonlinear effects previously observed for strong laser beams were experimentally revealed. The paper presents the observed results and an attempt at their interpretation.

The Zeeman He-Ne laser frequency stabilization system using a surface stabilized ferroelectric liquid crystal cell for polarization switching in the frequency stabilization loop is presented. Our experiments showed that two circularly polarized laser beams with on opposite sense of circularity can be switched up to 3.7 kHz rate. No additional optical components (the quarterwave and halfwave plates) were needed in switching setup. During three hours of operation the long time stability of the laser frequency of 3 multiplied by 10^-8 was achieved. The laser stabilization system is suitable for the two frequency interferometer setups.

The new generation of slab waveguide molecular lasers requires new resonators ensuring high extraction of output powers and high beam quality. In this paper we describe a few configuration of laser resonators which seem to be quite attractive for these requirements.

As a result of investigation of construction and technology of anti-laser filters based on colored glass and interference thin-film coating, the new solutions of absorption- interference filters have been developed. Their main advantages are: very high and selective absorption, even for several wavelengths (simultaneously) with increased transmission in the visible region, and increased energy resistance for high power laser systems.

The paper presents the result of investigations of spectroscopic parameters of YAG:Cr⁴⁺ crystals. The non- saturable component of the absorption coefficient, absorption cross-section, active centers concentration, excited state lifetime and energy consumed for bleaching effect have been estimated. Investigations of YAG:Cr⁴⁺ spectroscopic properties, and measurements of absorption and luminescence bands, allow the estimation of chromium ion concentration at particular charging state and positions in YAG crystalline structure, and allow also to determine their mutual relations and influence of these relations on the non-linear properties of absorber.

One of the latest laser beam applications is to selectively pump energy and generate coherent radiation transferred to another wavelength. It expands because the amount of generating sources with different selective wavelength permanently grows. Especially it applies to laser diode pumped systems resulting with highly efficient all solid-state compact lasers. These systems require well fitted thin layers' coatings. For microchip lasers as well as for parametric generators, the project of thin-layers stacks needs wide spectral analysis. Thin layer coatings for compact lasers have been elaborated. Stacks were based on oxide layer and were made with classical electron beam equipment.

There are used many different sources of radiation in present optic systems. The paper presents the beam splitters of radiation at a three different diode lasers used to one optical path. There were analyzed wavelengths: 670, 830, and 904 nm at 45 degrees angle of incidence.

In this paper a few possibilities of influencing the diffraction pattern by using dynamical diffraction gratings, i.e. such gratings, parameters of which evolve in time. This method allows application of a diffraction grating to deflection and/or modulation of the light beams.

A new experimental solution of a picosecond transient absorption spectrometer with a high power pulse YAG:Nd³⁺ laser has been developed and tested in studies of photophysical and spectral properties of molecular systems. The analyzing beam is the 'white' light of the picosecond continuum generated by the 1064 nm beam in isopropanol. The optical delay line of 20 cm travel range permits investigation of the processes occurring in the time scale to 1.3 ns with the time step of approximately 3 fs. The system was used to study the interaction of the excited xanthione molecules with alkanes and benzene occurring in the picosecond time scale. The paper describes also the design and performance of a double-beam pulse spectrometer use for measuring in the real time, changes in transient absorption evolution of emission and dynamics of the ground state depletion of molecular media. The technique of digital recording and data processing at the sampling rate of 2 gigasamples/s ensures a resolution of single nanoseconds in the time interval up to 10 microseconds. The spectrometer has been successfully tested in photophysical studies of the triplet states of xanthione in benzene and n- hexane solutions.

The two frequency laser interferometer for the angle and straightness measurements is presented. The principles of the operation of this laser system is described. The system consists of the laser head, optical elements, meteo station and PC computer. The construction of the main elements of the system are discussed. The parameters of the angle and straightness measurements are presented and compared to the other systems.

The influence of the magnetic field on Zeeman frequency of the He-Ne laser is presented in this paper. The new method of frequency stabilization of He-Ne laser is proposed. The optimization procedure for obtaining optimum discrimination curve of the He-Ne laser is described.

In this paper experimental results on infra-red laser oscillations in the He-Cu sputtered systems excited by an rf discharge (13.5 MHz) are reported. The results of the small- signal gain measurement of the infra-red He-Cu⁴ laser lines are presented.

Lasing properties of active media in sputtered hollow cathode discharge (HCD) He-Cu lasers operating on 780.8 nm transition have been investigated for several HC configurations. Direct measurements of small-signal gain and its spatial distribution have proved that a segmented hollow cathode discharge (SHCD) is the most efficient in achieving laser action on metal ions excited by thermal energy charge-transfer reaction. Results obtained for He-Cu lasers indicate that the observed linear dependency of gain on discharge current can be explained by limited flow of metal atoms into the region of laser generation and probably are valid for all kind of sputtered metal ion lasers oscillating on UV and IR transitions. The possibility of obtaining continuous or long-pulse laser operation in far UV range is also discussed. A new method of measuring diffusion coefficients of metal atoms in noble gases in sputtered HCD lasers is presented.

The article describes measurements and interpretations of transverse distribution of an underpressured nitrogen laser beam. Also there is a trial of visualization of a UV beam.

Propagation and focusing characteristics of the output beam emitted from the industrial, transverse-flow, cw carbo-dioxide laser working in the range up to 1.5 kW were determined experimentally, by implementing the standard scanning knife- edge technique. From the beam propagation caustics recorded under focused conditions the principal beam parameters such as the focal spot size, its location as well as the relevant beam quality factor mM+2) were determined. The focusing properties of the beam were investigated for different laser operation conditions defined by the laser output power values.

The main point of the method presented is the use of a combined probe which is a thermocouple serving also as an electrostatic probe. By means of this device the floating potential and translational temperature of the working medium of gas discharge lasers can be measured simultaneously in time and space. In the present report the construction of the probe and its measuring capacity are described and prospects for increasing the number of quantities measured are discussed.

Main properties of a beam from a flow carbon-dioxide laser were determined for power values of several kilowatts. External energy characteristics of the laser were measured depending on the power supplied to the medium, the medium's total pressure, chemical composition and flow rate. The drop in the mean power of the output beam was evaluated as a function of time. High frequency fluctuation of radiation power was observed. The analysis of beam distribution in the near and far field was carried out.

Electric and thermal properties of the working medium are presented for a flow carbon-dioxide laser generating a beam with a power of the order of some kilowatts. The medium was excited by a transverse stationary dc glow discharge. Floating potential and translational temperature distributions and the magnitude of cathode and anode potential drop were measured. Floating potential was determined depending on spatial coordinates, electric discharge current and on the flow rate. The degree of warming up the medium was analyzed, thermal flux directions and intensity were determined and optical heterogeneity of the gas mixture was evaluated. The measurements were carried out by the use of a combined probe.

The new trends in the construction of advanced versions of carbon-dioxide lasers, based on unconventional shapes of discharge regions as well as special designs of laser resonators promise the construction of compact, efficient infrared laser sources with unitary power much higher than for conventional carbon-dioxide lasers. The paper present the idea of synchronization of output beams in the 'two-slab,' waveguide carbon-dioxide laser, doubling the output power of efficient 'monoslab' laser, but preserving the output beam quality.

The construction of 875 mm long transversally rf excited carbon-dioxide waveguide laser is presented. We show the results of the laser operating in single EH₁₁ waveguide mode for the rectangular aperture of the laser channel equal to 1.7 multiplied by 4 mm.

A high-power all-Nd:glass laser using fiberless chirped-pulse- amplification technique is presented. The laser is capable of producing 1.2-ps, 2-TW pulses while the effective divergence of the beam does not exceed 10^-4 rad.

We present the results of investigations on the actively and passively Q-switched diode-pumped solid state lasers. The 4.4 mJ output energy of 100 W quasi-cw diode bar pumped Nd:YAG laser and 38% slope efficiency were obtained in free-running mode. In electro-optically Q-switched operation we obtained a monopulse of 1.2 mJ energy and a pulsewidth of 5.8 ns, which corresponds to 206 kW of pulse peak power. The pulses of energy of 0.41 mJ and pulse duration of 8 ns were obtained in the passively Cr⁴⁺:YAG Q-switched Nd:YAG laser. Single frequency passively Q-switched end pumped by 10 W fiber coupled diode bar Nd:YAG laser with output averaged power of about 1 W and pulse peak power of about 1 kW has been demonstrated. LiF(F^-₂) and Cr⁴⁺:YAG crystals were applied as passive Q-switches. Investigations of pulse duration, repetition rate, energy, power and spectrum in the Fabry-Perot interferometer were performed.

'Eye safe' lasers are very important for different applications in optical communication and lidar techniques. In this work we report the results of measurements of generation characteristics of Nd:GGG, Nd:YAG crystals for wavelength of 1.32 micrometer as well as Nd:YAP crystals generating radiation of 1.34 micrometer. Influence of UV radiation on the output characteristic of Nd:GGG laser is also reported.

Requirements and methods of forming of diode beams for end pumped lasers were reviewed. Examples of pumping systems were presented and analyzed. Influence of thermal lensing and thermal aberration on beam quality was analyzed theoretically and verified in experiments.

This work presents the parameter comparison of diode pumped solid state lasers worked in longitudinally pump configuration in cw operation. We built three monolithic lasers based on neodymium doped crystals (Nd:YAG, Nd:KGW and Nd:BLGO). They appeared to have quite good power stability and high quality quasi-TEM₀₀ mode beams.

We present comprehensive numerical modeling of graded-index separate-confinement-heterostructure single-quantum well (GRIN SCH SQW) lasers. In particular, we present for the first time a modified drift-diffusion model of the laser, which correctly takes into account quantum nature of carriers in the active region. The drift-diffusion equations are solved self- consistently together with Schrodinger and Poisson equation. The analysis is carried out for the general case of MQW active region. We employ our model to predict the behavior of the devices fabricated by molecular beam epitaxy (MBE) technique. The broad contact, test lasers produced in our laboratory exhibited threshold current density J_th equals 350 A/cm², intrinsic mode loses as low as 7 cm^-1 and internal quantum efficiency near unity. External quantum efficiency above 80% was achieved. The emitted power per uncoated facet just before degradation was equal to 5 W for pulsed operation with 0.1% filing factor and 140 mW for cw operation. We also discuss the development of the technology in terms of growth temperature and V/III beam fluxes ratio optimization.

In the present paper, vertical-cavity surface-emitting lasers (VCSELs) are briefly compared with edge-emitting lasers, general principles of their simulation are formulated, an importance of self-consistent approach in modeling of semiconductor lasers is proved and main results of VCSEL simulations are given for etched-well VCSELs and for proton- implanted top-surface-emitting lasers.

We provide results of the theoretical analysis of guided lateral mode in broad-area (BA) semiconductor lasers with modal reflectors formed by patterning the reflectivity of the front facet. The analysis has been performed by using a simple model based on the effective index method and the concept of the effective facet reflectivity. The numerical results include mode threshold conditions and far-field patterns of the lasing modes for various reflector configurations.

In the paper the author presents the results of experimental research concerning the influence of laser junction temperature on the processing characteristics of examined measuring track sector. Based on the measurements carried out, several signal-processing laser diode models were generated. Each of the models presented some different aspect of examined question, with the consideration of different mathematical formalizations, for example the use of linear regression.

The construction of a single mode semiconductor diode laser spectrometer that can be tuned electronically by temperature as well as current is presented. The laser was tested by tuning to the rubidium resonant line (780.2 nm):5s²S_1/2 - 5p²P_3/2. By using a lithium iodate crystal the primary infrared light (830 nm) emitted by a Sharp LTO- 15PT diode laser was successfully converted into the secondary light wave.

An approximate model of light generation in planar waveguide dielectric lasers with Fabry-Perot as well as distributed feedback lasers is presented. In particular the threshold analysis based on the spectral shape of the emission and absorption cross-section of the active medium is developed, which allows us to predict the threshold gain as well as the oscillation wavelength. Moreover, an approximate expression relating the small signal gain to the output power and characteristic parameters of the laser system is derived. It is used for design optimal planar laser structure (i.e., to calculate optical feedback and optimal thin film thickness) providing the maximal power efficiency. Also the dynamic behavior of the planar waveguide laser is discussed. Especially, the influence of the real system parameters on the relaxation oscillations and modulation bandwidth is analyzed. It is shown that the compromise between the optimal power efficiency and maximal modulation bandwidth is required. Furthermore the statistical properties of the generated light are investigated. In particular the effect of the characteristic parameters of the laser structure on the mean laser intensity, variation of the intensity fluctuation and correlation functions of the mode amplitude (which determines laser linewidth), and of the mode intensity fluctuation.

In this paper the basic problems related to active waveguide fabrication, characterization and properties are discussed. We also report the spectroscopic properties of the Er³⁺:YAG/YAG epitaxial thin films obtained in ITME Laboratory in Warsaw.

In the paper a problem of measurement of physical quantities in laser and optoelectronic photoradiometry is presented. There are defined fundamental terms such as: measurement, a measured object, a measurand, the result of a measurement. There are discussed photoradiometric measurement processing and photoradiometric measurement tasks. There are also presented metrological aspects of photoradiometry.

The present paper contains a description of two fundamental apparatus of the Polish metrological basis for lasermetry, that is two standards, one of which is a standard of a unit of mean radiation power and energy of a laser radiation, the other being that of a unit of energy of pulse radiation of a laser. Diagrams and principles of reproduction and transmission of the value of the unit of power and energy are presented as well as the fundamental characteristics obtained by metrological tests of standards which have been designed, made, and implemented.

The paper presents the parameters and the results of investigations of basic subassemblies of heterodyne detection systems of scattered radiation. Work on heterodyne radiation of infrared radiation, conducted in MUT from 1983, allowed us to develop several measurement systems, based on fundamental subassemblies developed in Poland. The sources of radiation are sealed-off carbon-dioxide lasers, frequency transformation is accomplished by means of acousto-optic modulators, the compression of pulses in dispersive lines, based on surface acoustic waves (SAW) is the heart of the detection systems.

There are many infrared systems which require detectors with controlled spectral responsivities. One of the examples is laser warning device. The spectral response of detectors for this particular application should cover a wide spectral range from about 0.6 micrometer to 11 micrometer. Thermal detectors are unselective, but they suffer from poor speed of response. In contrast, the photon detectors exhibit much better speed of response and sensitivity. The spectral responsivities of conventional photodetectors are close to that of the ideal photon counter with a given cut-off wavelength. It means that responsivities at short wavelength are highly reduced. Here we report MPC IR photodetector, which covers the required spectral band of 0.6 - 11 micrometers, exhibiting increased at short wavelengths. Calculation results of range of device which applies these detectors also are presented.

The aim of this work is to present new limits of application of some often applied criteria of evaluating and measurements bandwidths (linewidths) and to compare the results. There were given results of comparison bandwidths calculated for twelve typical signals according to six definitions of bandwidths applied and 12 coefficients for 'informational criterion' of bandwidths. It was demonstrated that the problem of evaluating or measuring bandwidths cannot be solved by applying any definition of bandwidth separately, because there exist some cases for which the antinomies are very strong.