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We develop simple and reliable technique, based on suitable Interference Wedged Structures (IWSs) as small-size, tile-like 5x2x0.1 cm device - IWS Analyzer (IWSA; Composed IWSA) for registration and quantitative evaluation of Hg (harmful pollutant) in gas discharge in lamps and in air. The main advantage of the IWSA technique is its applicability for direct observation with the naked eye of an illuminated IWSA through diffused or direct light from the object under study. We present theory, simulations, and appropriate realization for IWSA.

We present further development of our solutions of attractive Interference Wedged Structure based Beam Splitters built as suitable composition of only pure glasses (using Fresnel's reflection). Theoretical treatment and experimental test show the potential for suitable parameters to reach controlled splitting in range of 26%-99%. The splitters are list-like (5x2x0.2cm) interferential constructions especially for laser light. No problematic dielectric and metallic mirrors, operating power MW/cm2, easily maintenance. We have developed, applied and improved theoretical model for description and computer treatment.

A conventional Fizeau wedge (FW) is built of two flat reflecting surfaces inclined at a small angle. They form a gap with linearly increasing thickness normally to the wedge ridge. Such FWs with apex angles of 5–100 microradians and 5– 1000 micrometers thickness find application in optical metrology, spectroscopy and laser spectral control. The apex angle, the reflection coefficients and the refractive index in the gap form a unique interference pattern on both FW’s sides. To benefit from a large free spectral range of thin wedges and high spectral resolution of thick wedges, recently we proposed a stack of two FWs with matched parameters. Matching provides the same change of the resonant wavelength at the same lateral displacement of both wedges. The aim of this study is to develop a technique for calculation of the resultant transmission of the stack of two matched wedges at plane wave illumination that is based on determination of the number and optical path differences of the rays leaving the stack at a given point on its rear surface. Only rays with non-negligible contribution as an amplitude are taken into account. Numerical simulation and experimental verification are provided.

The optical interferential wedge or Fizeau wedge (FW) is a useful optical element with various applications in optical metrology, spectroscopy and laser technique. Various FW applications require knowledge of its response to illumination by a laser beam with an arbitrary wavefront. Recently, we applied the plane wave expansion method to study transmission and reflection of an air-gap FW under illumination with a Gaussian beam. The approach is based on the angular spectrum of the beam and the known FW response to illumination with a plane wave. In this study, we adapt this approach for the more general and more frequently encountered case of a FW with a non-air gap. We developed an approximate algorithm, which is applicable at small incidence angles to wedges with refractive indices different from 1 and illuminating beams with arbitrary amplitude and phase distributions. Comparison to the experiment is also provided.

We demonstrate that interference wedge structures suitably composed of wedged purely glass elements using Fresnel reflection only can be effectively employed for realization of competitive light beam splitters and filters (especially for high-power laser beams). The theoretical analysis, simulation and experimental testing show that for appropriately chosen parameters and for a suitably composed interference complex such structures can achieve a controlled variable transmission in a wide range (99% – ∼30%) and reflection from ∼2% to ∼70%. The traditional realization of purely glass splitters ensures no more than ∼20% reflectivity. The splitters proposed are very compact sheet-like elements (e.g., 5×3×0.2 cm) and the splitting is implemented by sliding in the splitter’s plane. Thus, the propagation direction of the formed beams is preserved. The incident beam on the purely glass splitter (no dielectric or metallic mirrors) can be of high power and the influence of the air humidity is strongly reduced; also, cleaning the filter surfaces presents no difficulties. A single splitter can work in a wide range of wavelengths (IR, visible) without polarization dependence for incident angles up to ∼20°.

In the present paper, we propose a compact composite wedge interference structure by combining wedges with different geometry. We use interferential wedges with optical thickness from several micrometers to several hundred micrometers and apex angles of the order of tens microradians. The aim of the conducted study is to prove that such a structure exhibits improved optical properties in comparison to a conventional wedge. We have carried out simulations and experiments with a structure built from two wedges. We have shown that, instead of multiple transmission peaks observed for a single interferential wedge, the composite structure provides selection of a single resonance in transmission within the impact area of a large diameter monochromatic beam and enables wavelength tuning when a small diameter multi-wavelength beam is used. The first property ensures analysis of light beams characterized with a wide spectrum. The second feature allows for increase of the wavelegth tuning range at keeping spectrally narrow transmission peak if the structure is formed by a thin and a thick interferential wedges. Two such structures have been realized using a technique which we have developed. The experiments made with this structures show that the produced transmission peak is narrowed spatially and spectrally at the expense of lower transmission which achieves 50–60% of transmission ensured by the used interferential wedges.

Having an essential experience [2]–[5] in the field of Interference Wedged Structure (IWS), we introduce a new advantageous element of this type – Composite Tunable Interference Wedged Structure (CTIWS). The CTIWS is Iist-Iike sequence of superimposed wedged layers each with reflecting surfaces. For conveniently chosen apex angles and thickness of the layers, the CTIWS can assure high spectral selectivity (to ∼0.01nm and less in spectral range of ∼10 nm and more) and smooth tunability by simple sliding of the structure along all wedge arm (∼ few cm). We have developed simple manner for physical description of IWS and especially CTIWS by convenient adaptation of the Fabry-Perot theory. We show that for the most important practical cases the results are similar to the obtained by more complex exact analytical treatment. The useful for the application new experimental results are carried out. On the base of IWS and CTIWS, applying convenient architecture, we have introduced and investigated new Iossless Wavelength Division Multiplexing (WDM) element with independent tuning of each output/input. We considered the realization for the case of fiber optic systems of interest for optical communications.

We propose to take advantage of the focalization effect of the pump light by the cylindrical laser rod in a side-pumped Nd:YAG laser (flashlamp or diode pumping) to obtain efficient two-wavelength operation. Under conveniently chosen conditions the focusing by the rod increases the pump power density in the near axial rod part about 2½ times, as we show, in comparison with the peripheral rod part. The focalization can strongly facilitate and to increase energetically the generation of weaker lasing lines in the axial part. This advantage is utilized by employing coaxial two-channel laser architecture, where the optically separated axial and peripheral parts of the rod generate each in its own spectral selective resonator. Beside the competition-less generation at two wavelengths (lines), other specific and essential advantages of the proposed laser solution are: (1) to produce emissions at a weaker line (generated in the axial part) and at a stronger line (in peripheral part), simultaneously and with equalized energy without loss of pump energy for the equalization; (2) the two emissions are produced and emitted naturally in coaxial beams using the full rod volume. We have realized such a laser with flash-lamp pumping (output to ~0.45 J; tunable pair of lines from 1.06, 1.32, 1.34, 1.36 and 1.44 μm) and carried out an experimental and theoretical study of its operation, including passive Q-switching.

Having essential experience and results, concerning Interference Wedged Structures (IWS), we have developed and practically realized optical beam splitter elements as suitably built variants of IWS. The principle of action, theoretical treatment, including computer simulation for optimization is briefly discussed. As an essential point, the technological approach for practical realization of simplest applicable Interference Wedged Based Splitters (IWBS), are carried out. The splitters are built as compact thin flat and plane, practically – sheet-like, elements with dimensions e.g. ∼ 4 × 3 × 0.2 cm. They present advantages as: smooth and linear varying the power ratio between the formed beams by simple sliding of the splitter in its plane; keeping the direction of propagation of the formed beams during the control of their variations; very small losses in splitting (theoretically ∼5 %); work with high power incident beams (kW/cm2 and more for CW and MW/cm2 for ns pulses beams).

We report (theory, experimental check) an improved approach for generation of a tunable, subnanosecond pulse (0.1–0.4 ns), based on a single pulsation (“spike”) separation from the transient oscillations in a dye laser with active mirror (AMIR). A pumping by 20–50 ns pulses from Q-switched Nd:YAG laser is considered. The separation is in original, two-spectral selective channels cavity, where the forced by AMIR quenched generation at one of the wavelength stops initially started spiking generation at the other wavelength after the first spike development. The AMIR quickly starts the quenching generation at a precisely controlled moment and with necessary intensity thus assuring the desired separation. An advantage is a high reproducibility of the separation for high (~250%) pump power fluctuations combined with tuning in large range (~20 nm). To obtain such an operation we form ~1 ns leading front pump pulse by electrooptical temporal cutting of the input pump pulse and use an optical delay line. This increases also a few times the power in the separated spike (to be ~100 kW). Our approach widens the combinations of lasers for effective applications of spike separation technique (dye lasers excited by Q-switched solid-state or Cu-vapor lasers).

The results of a comparative study (theoretical and experimental) of two original approaches for spectral control of two-wavelength pulsed Ti:sapphire (Ti:S) lasers and the most popular conventional methods are presented. Single line operation as a particular case is considered. We compare our own methods: (i) combined dual pulse pumping–passive self-injection locking (DPP–PSIL) and (ii) coupled cavity dye laser injection locking (CCLIL) with the conventional methods: (i) intracavity selection (IS), (ii) PSIL and (iii) traditional injection locking using an external dye laser. The most important criteria—laser efficiency, emission line width, tuning range, spectral purity and buildup time are compared under optimized conditions. The comparison is made using the same pump source with constant output energy in each case. The results serve as a basis for choosing correctly the most suitable spectral control technique for a particular Ti:S laser application. It is shown that the DPP–PSIL method guarantees a remarkable improvement of the Ti:S laser performance (nearly doubling the laser efficiency with the same line width and comparable laser tuning range as IS, combined with a protection of the selectors). The CCLIL approach assures a maximum laser efficiency in narrow line emission in addition to a minimal and reproducible buildup time. The IS method provides a maximal tuning range.

Spatial and spectral control of a ring laser with a homogeneously broadened active medium has been achieved using a bi-directional injection scheme. Such a type of injection provides a new technique to obtain a controlled pulsed laser emission spectrally locked to a selected atomic absorption line. The proposed technique makes use of the strong competition between counterpropagating waves in the ring cavity. The output control relies on the unbalance between the two injected beam intensities produced by the absorption. When the injected light is scanned around the absorption line, an unidirectional light generation occurs only at the wavelength of the desired absorption line. Due to the non-linear character of the process, the emitted spectrum can be an order of magnitude narrower than the absorption line. Both computer simulation and experimental study of the phenomena are reported for a pulsed dye laser pumped with the second harmonic of a Q-switched Nd:YAG laser.

By using the developed by us approaches and instrumentation, we have obtained and presented series of systematized data, which are important for the use of the laser light in infrared (IR) spectral region. The obtained data include: 1) reflectivity of the human tooth dentin; 2) the spatial intensity distribution in the cross-section of the light beam penetrating the tooth’s dentin; 3) the absorbed and the diffused parts of the laser light that have been determined separately through combination of optical and calorimetric techniques. The last result is the most important because it permits to calculate the dentin absorption and scattering coefficients. The study is performed for the laser light at two easily generated wavelengths – 1.06 μm and 1.36 μm, emitted by the Nd:YAG laser that is well known, commercially available, economical and widely used in many laboratories and medical institutions. The study is made on the basis of fresh in-vitro teeth samples from the persons of Bulgaria, Sofia region.

On the base of our previous experience in the dual-color lasers we present our actual development - experimental realization, theory of a flash-lamp pumped Nd 3+ :YAG laser, that produces output at two desired (tunable) lines in the spectral range of 1μm -1.44 μm in free lasing and Q-switching operation. The laser operation avoids the wave’s competition effect for the two generations operating in two different parts of the active volume of an active single crystal and two closely disposed prism-selected resonators. Also, as we have shown, varying the partial laser volumes and the losses at each resonator in combination, it is possible to produce the generation at the two desired wavelengths with near equal output energy, peak power simultaneously or at desired time interval. We have found and treated some peculiarity of the formation of the generation, such as the actually used parts of the partial volumes.

We have developed a novel simple technique for a wide gain laser narrow line selection and tuning using classical interferometric selectors (Fabry–Perot interferometer, interference wedge). Its most important advantage is that selection and tuning need only one thick interferometer instead of a combination of a thin (5 μm) and a thick (∼100 μm) one as in the conventional approach. This makes tuning much simpler without having to synchronize two tuning elements and the system as a whole essentially cheaper. The computer simulation and the experimental test have shown that the proposed technique is highly competitive compared with traditional interferometers with thicknesses of 30–70 μm. It assures a spectral resolution of less than ∼0.01 nm and tuning in the wide region (≥100 nm), in particular, it completely covers the spectrum of the dye solution and that of the Ti:Al2O3 crystal. Besides enlarging the tuning region, the linewidth is narrowed and the spectral purity of emission is increased. Using a qualitative interferometer with transmission close to unity a high efficiency can be reached.

We have demonstrated that passive self-injection control is very effective in a CW Ti/sup 3+/:Al/sub 2/O/sub 3/ laser to produce high efficiency (/spl eta//spl sim/15%), narrow-line, two-wavelength emission. Light reinjection is achieved with an original high-resolution two-wavelength selector combining an interference wedge and a grazing incidence grating. The device operates outside the main nonselective laser cavity; thus avoiding insertion losses and optical damage problems. A 1.5 W, background free, total output power has been obtained simultaneously at two narrow laser lines (fwhm: 8 pm), independently tunable over 50 mn. The two laser lines can be emitted in a single beam or in two separated beams. Self-injection wavelength control has been demonstrated both for linear and for ring laser cavities. In the latter case, unidirectional behavior is also obtained in the same way. Single-step (5s/sup 2/S/sub 1/2/-5P/sup 2/P/sub 1/2,3/2/) and two-step (5s/sup 2/S/sub 1/2/-5p/sup 2/P/sub 3/2/-5d/sup 2/D/sub 3/2,5/2/) excitation of atomic rubidium vapor has been performed with our original laser device. >

A coaxial flashlamp pumped titanium: sapphire laser, emitting two independently tunable wavelength separately selected in a novel dual-channel cavity, is described. Two different modes of operation—with and without wavelength competition—are realized; they can easily be switched between. Generation of two simultaneous or successive pulses (produced by one pumping pulse), each corresponding to one of the emitted wavelengths, is accomplished. The time interval between the pulses is variable from 0 to about 3 μs. The generated wavelengths are different or identical. A coupled rate equation model is used to estimate the time characteristics of the two-wavelength operation.

We present two novel applications of optical properties of the interference wedge (compact realization of the Fizeau Interferometer) for the case of illumination with a small diameter laser beam. The first one is a new and competitive wavelength division multiplexing structure. The main advantages of the device are the possibility for separate frequency tuning of each input-output channel as well as its compactness. The made computer simulation proves that the structure can work with very short laser pulse duration (~ 0.1 ns), which corresponds to pulse repetition rate of order of ten GHz and more, thus fulfilling the requirements of modern digital communication systems. The theoretical analysis and the experimental check with laboratory model of a free-optical communication system show a sufficient resonant narrowline transmission up to 75% with the linewidth of emission from 0.05 nm to few nm. The second proposal is a device which allows for distant laser measurement of small linear translation of a rigid object for distances from a few meters up to hundred meters.

A simple, purely optical approach to produce, in a ring Ti:Al2O3 laser, a pulsed unidirectional generation, spectrally fixed at a reference atomic absorption line is described. The control relies on the unbalance between two opposite, passive, wavelength-scanned self-injections that is produced by the absorption at the reference line. It is shown both experimentally and theoretically that: (i) the emitted spectrum is centered at the absorption maximum and (ii) due to the nonlinear character of the process the spectrum is narrowed several times compared with an absorption linewidth.

We describe a plane-wave-expansion approach for calculation of the fringe pattern in transmission and reflection for a Gaussian monochromatic beam. Both positive and negative incidence, at which the incident light beam undergoes multiple reflections within the wedge in direction of increasing or decreasing wedge thickness respectively, are analyzed. It is shown that the two opposite incidences of the light beam are described by the same mathematical expressions; i.e., the transmitted/reflected fringe pattern at positive incidence is a continuation of the pattern at negative incidence at some distance from the wedge. Numerical simulations are made for a high-reflectivity-coating air-gap Fizeau interferential wedge with apex angle of 5-100 microrad and thickness of 5-500 microm as a useful optical element in laser resonator design. Experimental verification is also provided.

The peculiar properties of the high-reflectivity Fizeau wedge used in reflection are pointed out and used to obtain single-mode operation of a Nd:YAG-pumped dye laser. It is demonstrated that the reflecting Fizeau wedge can have, as a cavity output coupler, the double action of selective-feedback mirror and an output filter, thus producing a background-free tunable narrow line.

We have developed and investigated a 0.53 μm Nd: YAG pumped combined dye-Ti 3+ :Al 2 O 3 laser, which emits two independently tunable near-infrared wavelengths in a single beam with relative time decay controllable in the range 0–250 ns. The emission is produced in a simple dual-channel resonator, where an intracavity interference wedge is used both as an efficient channel coupler and as a spectral selector. The delay between the pulses arises from the different temporal behavior of the dye and the Ti 3+ :Al 2 O 3 laser emission and is controlled by varying the pump intensity or the cavity length.

We present two original, all optical techniques, to produce a narrowline laser light, fixed at the frequency of a chosen reference atomic absorption transition. The first type of systems is an essential improvement of our method 3,4 for laser spectral locking using a control by two frequency scanned, competitive injections with disturbed power ratio by the absorption at the reference line. The new development eliminates the narrowing limiting problem, related with the fixed laser longitudinal mode structure. We have proposed an original new technique for continuously tunable single mode laser operation in combination with synchronously and equal continuous tuning of the modes of the amplifier. By adapting the laser differential rate equations, the system is analyzed theoretically in details and is shown its feasibility. The results are in agreement with previous our experiments. The essential advantage, except simplicity of realization, is that the laser line can be of order of magnitude and more narrowed than the absorption linewidth. The second system is based of the laser amplifier arrangement with a gain knock-down from the competitive frequency scanned pulse, except at the wavelength of the desired absorption reference line. The essential advantages of the last system are that the problem of fixing laser mode presence is naturally avoided. The theoretical modeling and the numerical investigations show the peculiarity and advantages of the system proposed. The developed approaches are of interest for applications in spectroscopy, in DIAL monitoring of the atmospheric pollutants, in isotope separation system and potentially - for creation of simple, all optical, frequency standards for optical communications. Also, the continuously tunable single mode laser (and the combination with the simultaneously tunable amplifier) presents itself the interest for many practical applications in spectroscopy, metrology, and holography. We compare the action and the advantages of the two systems proposed.

The goal of the present paper is to develop a procedure for calculation of the fringe pattern in reflection for Fizeau interferntial wedge considering both positive and negative incidence at which the incident light beam undergoes multiple reflections within the wedge in direction of increasing or decreasing wedge thickness respectively. High-reflectivity coatings wedges with apex angle of 5 - 100 μrad and thickness of 5 - 500 μm are considered. To avoid the drawbacks of the plane-wave approximation and to calculate the interference pattern for a limited beam illumination at any distance from the wedge, we proposed a plane-wave expansion approach. We analyzed the wedge interaction with a Gaussian beam as a beam structure of particular importance in laser technique. In addition, an analytical solution of the involved integrals was obtained for the Gaussian intensity distribution. It was shown that both contra-incidences of the light beam could be described by the same mathematical expressions, i.e. the reflected fringe pattern at positive incidence could be considered as prolongation of the reflected pattern at negative incidence at some distance from the wedge. Experimental verification is also provided.

The potential of the Ti:sapphire lasers for applications in spectroscopy and differential absorption lidar measurement can be essentially improved when the lasers operate simultaneously at two independently tuned wavelengths.1-3 Recently, we have demonstrated that for the cw Ti: sapphire laser, a passively self-injection locking technique4 is an attractive way to realise this mode of operation. We applied here this technique in novel schemes to obtain efficient two-wavelength operation for a pulsed Ti:Al2O3 laser, pumped with a 0.53µm harmonic of Nd:YAG laser (Ep~4 mj), Δτp ~ 15 ns). The control is produced by reinjection of a small part (~0.003%) of the cw output back into the non-selective cavity at two wavelengths after the spectral filtering.3 The two-wavelength laser arrangements used are given in Figs, 1a, 1b, and 1c. They have as a principal part a two-outputs Kogelnic-type concave mirrors (mc1,mc2)—flat mirrors (MO,Me) cavity with a longitudinally pumped 1-cm-long 5×5 mm cross section Ti:Al2O3 crystal. The one laser output, this from the flat mirror Me (R = 70%), is reinjected back at two selected wavelengths λ1, and λ2 by the two wavelength retroreflector TWR, based on the Interference wedges (IW, and IW2);5 wedge thickness ~5µm, reflectivity of the coatings R1 = R2 = 0.9, and the wedge angle α = 5.10–5 rad. The wedge transmission at resonant wavelength is ~0.7. In the schemes used, a single interference wedge acts as a tunable spectral filter for one wavelength (which is resonant for the wedge thickness of the incident part) and as a coupler for the second wavelength λ2, selected by the second wedge IW2. In the first arrangement (Fig. 1a), which is similar to this applied by us for the cw laser,3 the retroreflection is in coincident beams.

We report a simple technique for generation of tunable subnanosecond pulses (0.1-0.3 ns) based on single spike selection from the relaxation oscillations in a dye laser by use of an active mirror. The selection is in original two-wavelength cavity with competitive generations at two wavelengths, the second of which is forced in appropriate moment by the quickly included amplification of the active mirror to suppress the initially started lasing in the first channel. To produce such switching we form the pump pulse by temporal division of a 15-50 ns standard pump laser pulse using a Pockel's cell with a 1-2 ns switching time and an optical delay line. We have shown that in addition, such formation increases essentially the selected spike power. The proposed technique widens the choice of suitable lasers in which the single spike selection technique may be applied to include dye lasers excited by a Q-switched solid-state laser or a Cu-vapor laser. The other advantages in comparison with the given in the literature single-spike selection techniques is the improved reproducibility of the selection for high (~100-200%) pump pulse power fluctuations, shorter pulse duration and pulse shape improvement. Both theoretical consideration and experimental verification are carried out.

Recently, using an aopposite injection we have introduced a novel laser injection-locking approach for high gain (~10 4 -10 8 ) and linear amplification of modulated low power (~μW-mW) laser radiation. In this work we report the investigation of the noise characteristics of such amplifier at the example of high repetition rate pulse pumped linear dye lasers. The background emission of the laser at the laser modes outside the signal and counter injection wavelengths is considered as a main source of the noise. By modeling the laser action with adapted system of differential equations and numerical analysis, solving this system for the cavity modes, we have obtained the total noise and its spectral distribution. The results show that for suitably chosen conditions the intracavity noise is very low or acceptable (~10 -2 with respect to the signal output). The essential dependencies of noise characteristics from the system parameters are carried out.

We demonstrate and investigate (theory, experiment) a peculiar mode of cw Yb3+:doped crystal laser operation when two emissions, at two independently tunable wavelengths, are simultaneously produced. Both emissions are generated from a single pumped volume and take place either in a single beam or in spatially separated beams. The laser employs original two-channel cavities that use a Passively Self-Injection Locking (PSIL) control to reduce the intracavity losses or a very simple for practical realization two near collinear channels cavity. A two-wavelength, single, longitudinal mode generation is also obtained. The results reported are based on the example of Yb3+:GGG laser and Yb3+:YAH laser. The lasers operate in the range 1023-1033 nm and 1030-1040 nm, respectively with a total output power of ~0.4 W.© (2004) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present a further development of the proposed by us an injection-locking technique for all-optical and high gain (~10 3 -10 6 ) amplification of a periodically modulated (PM) intensity, low power (~μW), laser radiation. The problem that limits the use of standard injection locking optical amplifier is to obtain a linear response to the PM injection. We have solved this problem by introducing a competitive CW injection in appropriate ring and linear schemes and have carried out previously the detailed consideration for the sinus low modulated radiation. Here we report the application of our original technique for amplification of information sequences of rectangular pulses. The amplifier operation is modeled with the rate differential equations system. We have shown the applicability of the proposed technique for amplification of pulses with repetition rate more than 40 MHz and in special conditions-to approximately 128 MHz without loss of the information capability. The pumping is with 100-250 MHz mode locked Nd:YAG laser (0.53 μm harmonic). The consideration is on the example of Rhodamin 6G dye laser. The pulses with peak power of 0.1μ W to 200 μW are amplified by factor of 10 9 -10 6 (to more than 2000 W).

We present two simple and effective approaches for widening of the tuning range of the two-wavelength generation in two-channel laser cavity. The first is based on the use of combination of interference wedge and linear neutral filter and the second on the use of active mirror. This widening is combined with near equal intensities in both emissions. The use of the active mirror assures a real simultaneous two-wavelength operation. We consider a dye laser.

We present new solutions of a diode-pumped, cw Yb:YAG laser that is of interest for applications in spectroscopy and metrology. The proposed schemes permit producing of the emission in a single pumped volume at two independently tunable wavelengths, including single-mode regime. A passively self-injection (PSIL) controlled operation that ensures low threshold and high output is presented. The peculiarities of the two-wavelength operation of the considered laser are carried out. The laser operates in the range 1028 - 1035 nmw with a total output power of 0.4 - 0.7 W.

Recently we have proposed an injection-locking technique for all-optical and high gain (approximately 10 3 - 10 6 ) amplification of a periodically modulated (PM) intensity low power (approximately μW) laser radiation. The amplification is based on the injection locking control in linear laser schemes with homogeneously broadened active medium. The problem that limits use of such type of optical amplifier is to obtain a linear response to the PM injection. This is solved using a competitive CW injection. We have introduced a few different solutions of such laser amplifier -- with pulse pumping and with CW pumping, using the high repetition rate intracavity laser generation chopping. Here we report the detailed comparative study of such different realization of the proposed by us technique. The theoretical study is based on adapted rate equations system. The main results concerned the optimal case with the lowest nonlinear distortion and the condition of its elimination.

We propose a simple interferometer-type-device that permits to produce a variable length (1 - 15 ns) rectangular laser pulses, starting from a long (approximately 10 - 50 ns) conventional pulse that is emitted by Q-switched Nd 3+ -doped laser. The system uses an one time switched electro-optical pulse division at the input laser pulse and cutting all-optically a rectangular part of one of the formed partial pulses by appropriate bleaching of interferometer (Fabry-Perot, Fizeau) which gap is an Cr 4+ :YAG plate. The precisely controlled bleaching is produced in reliable manner using the second partial pulses and an optical delay line. The length of the obtained rectangular pulse can be precisely varied between 1 and 15 ns. The technique proposed can be applied also for the other lasers.

We demonstrate and investigate a peculiar mode of cw Yb3+-doped crystal laser operation when two emissions, at two independently tunable wavelengths, are simultaneously produced. Both emissions are generated from a single pumped volume and take place in either a single beam or spatially separated beams. The laser employs original two-channel cavities that use a passive self-injection-locking (PSIL) control to reduce intracavity loss. The advantages of the application of the PSIL technique and some limitations are shown. The conditions for two-wavelength multimode operation of the cw quasi-three-level diode-pumped Yb3+ lasers and the peculiarity of such an operation are carried out both theoretically and experimentally. The results reported are based on the example of a Yb3+:GGG laser but similar results are also obtained with a Yb3+:YAG laser. The laser operates in the 1023–1033-nm (1030–1040-nm) range with a total output power of 0.4 W. A two-wavelength, single longitudinal mode generation is also obtained.

We describe a simple, new technique for producing of nanosecond pulses with rectangular (or triangular) temporal shape and with tunable wavelength. The technique is based on a pumping of a tunable dye laser by pulses with formed rectangular (or triangular) shape, emitted from a standard Nd:YAG (2 -nd harmonic) or Copper-vapor lasers. The pump pulses are formed in a simple electro-optical system. We have shown theoretically that the main problem to reproduce the pump pulse shape in a nanosecond dye laser -- a 'spiking' phenomenon, can be avoided using an appropriate pre-pulse pumping of the dye before the main, formed pump pulse. The experimental check confirms the theoretical predictions.

We describe and analyze an original technique for all-optical and high gain (approximately 10 3 - 10 6 ) amplification of a periodically modulated (PM) intensity low-power (approximately (mu) W) laser radiation. The amplification is based on the injection locking control in linear laser schemes with homogeneously broadened active medium. The main problem of the injection locking amplifiers is to obtain a linear response to the PM injection. We propose to solve this problem by injecting a second laser beam with a constant power and a slightly different wavelength or orthogonal polarization compared to the injected PM beam.

Here we report the proposed by us concept for monitoring the atmospheric and Earth Hg and Pb pollution by means of Intracavity Laser Spectroscopy (ILS). The concept profits from the extremely high sensitivity of the ILS dye laser registration by preliminary excitation of the Hg(Pb) atoms to a suitable level to induce absorption at the analytical transition corresponding to the second dye laser emission spectrum. A theoretical proof is given on the possibility for two-step optical excitation from the ground state level.

Combining optical asymmetry in reflection of a unequal mirrors interference wedge with its focusing property at negative incidence, we propose effective separation of a laser oscillator from a highly excited amplifier in a tunable laser oscillator-amplifier system, i.e. solution of the problem with removal of the background radiation self- injection.

We report an original approach for tunable subnanosecond pulse (200 - 500 ps) generation in a ring dye laser. It is based on limitation of generation to a single `spike' from the starting transient process using for excitation a quasi- rectangular pulse with duration less or comparable with the time interval between the spikes. The pumping pulse (3 - 7 ns) is formed both by electrooptical division of a standard nanosecond (15 - 50 ns) pulse emitted by a Q-modulated laser in an original scheme and by overlapping of the obtained partial pulses which are fed bi-directionally into the active medium of the ring laser.

We show, that the unbalanced bi-directional passive self- injection permits to obtain a pulsed unidirectional operation at the reference atomic absorption line in a ring Ar 3+ pumped Ti 3+ :Al 2 O 3 laser with a repetition rate of order of 10 3 - 10 5 Hz. The model used for the description of this type of laser is based on the adaptation of the rate equations systems. By computer simulation, the dependence for the repetition rate from the laser parameters and the switching time is obtained.

In this paper we report a comparative study the amplification and spectral tuning characteristics of an injection seeded Ti:Sapphire laser and multipass (4 passages) amplifiers. We show the advantages of injection seeding method to amplify input pulses of low energy levels (nJ and sub nJ). In the multi-passages amplifiers the wave competition for the two wavelength amplification is low. For high level (mJ) pulses the both systems are comparable, but in the injection locking amplifier the temporal pulse shape distortion is essentially high. The energy and power amplification levels are compared both with the change of the output width. For the reported two new multi-passages schemes we are study the dependence of the characteristics on the input polarization.