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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.

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).

A simple all-optical technique for fixing the spectrum of the output from semiconductor laser at a chosen absorption atomic line is realized and studied. The technique, which is not of a laser locking type, uses a conventional diode laser without any influence on its operation. For implementation of the technique, the diode laser output is fed to a modified Michelson interferometer, and controllable disturbing of phase and amplitude correlation between the interfering beams in the two arms of the interferometer is achieved by frequency scanning through a contour of a reference absorption line of a substance introduced in one of the arms of the interferometer. It is shown both by experiment and theory that, under properly chosen conditions, the spectrum of the obtained light is fixed at the atomic line and has a linewidth comparable to the linewidth of the used absorption line.

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).

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 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.

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.

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 have developed and investigated a simple solution of tunable laser with strongly decreased background emission (max pick-to-pick power ratio ≤ 10 -8 ) by generation at additional wavelengths, except the selected. The cavity scheme permits to obtain easily laser output only at the selected wavelength, using a simple system with interference wedges. The spectral position and the losses at both generations are easily and independently controlled to needed optimal values. The theoretical treatment based on the rate equation system, shows that for the appropriate chosen conditions the technique developed permits to reduce by approximately two orders of magnitude the intensity of the background emission about the selected line (pick power to be less than 10 -8 ). The investigation is on the example of pulsed dye lasers. The results are applicable for other tunable lasers with homogeneously broadened active medium such as Ti:sapphire, diode, etc. The lasers of considered type (with high spectral purity) are of essential interest for application in biomedical investigations of tissue luminescence spectrum, in Raman spectroscopic investigation, in isotope separation.

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.

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 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.

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.

We report a simple technique for generation of tunable subnanosecond pulses (0.2–0.4 ns) based on single spike selection from the relaxation oscillations in a dye laser using preformed and overlapping in time excitation pulses. The pulses were obtained by temporal division of a 5–50 ns initial pulse using a Pockels cell with a 1–2 ns switching time and an optical delay time. The proposed technique widens the choice of suitable dye 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. Other advantages to this technique are the shortened length of the generated subnanosecond pulse, the increased energetic output, higher reproducibility, and the possibility for synchronization of spike generation to an external signal accurate to within 2–3 ns.