Abstracts of Vol. 9, No 1
CONTENTS - return

Invited papers 1, 7, 19
Contributed paper 35, 49, 57, 67, 75, 83, 91

Materials and process issues in the fabrication of high performance VLWIR HgCdTe infrared detectors
H.R. Vydyanath and V. Nathan

Issues relating to fabrication of VLWIR HgCdTe detectors with high performance and uniformity are reviewed. The primary mechanism operative in the activation of p type dopants in HgCdTe is discussed along with implications for fabrication of high performance detectors. Origin of  native defect related deep centers in limiting the minority carrier lifetime is explored.
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High power diode lasers: topics relevant to optical pumping
B. Mroziewicz

Features of diode lasers pertinent to their application in pumps for solid slate lasers and erbium-doped fibre amplifiers (EDFAs) are reviewed. Among them the factors restricting diode laser brightness and output power are discussed more in detail. Design and some properties of heterostructures used in fabrication of laser pumps for solid state lasers and EDFAs are described. Al-free lasers proved to be more resistant to the catastrophic optical mirror damage and are discussed more thoroughly. Broad area lasers, 1-D bars and 2-D arrays are surveyed and some remarks relevant to EDFA application are made. The paper is concluded with discussion of diode laser designs capable to provide the output beam of a better optical quality. In this context ROW and ARROW array's as well as MOPA and MFA-MOPA structures are shortly described.
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Diode-pumped solid-state laers
Z. Jankiewicz and K. Kopczynski

Progress in technology and construction of diode-pumped laser made in the 80's caused renewed interest in diode pumping of active media of solid-state lasers (DPSSL -Diode Pumped Solid State Laser) and next their rapid development. At present, DPSSL are commonly applied in medicine and industry.
The paper presents advantages of such excitation and significant improvement in generation efficiency, longer service life of devices, smaller dimensions of quantum generators and theirs power suppliers. Special attention was paid to the possibility of application of new active media (new neodymium doped hosts), including ytterbium (Yb) doped media, that have perfect functional parameters with diode pumping. Fundamental configurations of active media and their excitation methods were described. A "slab" type geometry used for high-power lasers was distinguished. It was shown that construction of, so-called, microlasers is possible when diodes are used as pumps of solid state lasers. Microlasers can generate strictly monochromatic radiation (i.e., generate only one longitudinal mode). These lasers can be used for rangefinder transmitters and radars with heterodyne detection – new type devices applicability range of which is difficult to predict. Microlasers can be also used as frequency and length standards. A group of fibre lasers was considered and their unusual possibilities were described, among others generation of beams of high quality (M2 ~1) and high-power (1 kW). The examples of construction of high-power DPSSL (3.5 kW) were presented.
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Strained layer SCH SQW InGaAs/GaAs lasers for 980-nm band
M. Bugajski, B. Mroziewicz, K. Reginski, J. Muszalski, J. Kubica, M. Zbroszczyk, P. Sajewicz, T. Piwonski, A. Jachymek, R. Rutkowski, T. Ochalski, A. Wojcik, E. Kowalczyk, A. Malag, A. Kozlowska, L. Dobrzanski, and A. Jagoda

Strained layer InGaAsIGaAs SCH SQW (separate confinement heterostructure single quantum well) lasers were grown by a molecularbeam epitaxy <MBE). Highly reliable CW (continuous wave) 98O-nm. broad contact, pump lasers were fabricated in stripe geometry using Schottky isolation and ridge waveguide construction. Threshold current densities of the order of Jth =280 A/cm2 (for the resonator length L = 700 urn) and differential efficiency h = 0.40 W/A (41%) from one mirror were obtained. The record wall-plug efficiency for AR/HR coated devices was equal to 54%. Theoretical estimations of above parameters. obtained by numerical modelling of devices were Jth = 210 A/cm2 and h = 0.47 W/A from one mirror, respectively. Degradation studies revealed that uncoated and AR/HR coated devices did not show any appreciable degradation after 3000 hr of CW operation at at 35°C heat sink temperature at the constant optical power (50 mW) conditions.
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Oxide crystals for solid state laser applications
T. Lukasiewicz, A. Majchrowski, and Z. Mierczyk

Recent trends in optoelectronics tire towards small solid stale lasers pumped by laser diodes. The paper describes efforts to create material basis for the development of this branch of optoelectronics. Single crystal growth and properties of many compounds acting as active laser or self-frequency doubling materials, passive modulators, nonlinear optical materials, and acousto-optic materials are discussed, including yttrium aluminium garnet with high neodymium concentration, vanadates, borates. and double tungstates.
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High repetition rate, V3+:YAG crystal Q-switched diode pumped Nd lasers
J.K. Jabczynski, Z. Mierczyk, W. Zendzian, K. Kopczynski, and Z. Frukacz
The high repetition rate passively Q-switched neodymium host lasers operating at 1mm wavelength pumped by a 10-W fibre-coupled diode laser are presented. As a passive Q-switch the V3+:YAG crystal was applied. The V3+:YAG parameters were determined in spectroscopic and saturable transmission experiments. A numerical model taking into account short recovery time of V3+:YAG~5 ns and excited state absorption was used to analyse such a laser. The thermal lensing magnitude and performance were determined in free running experiments for two Nd:YAG rods of different quality and Nd:YLF crystal. The smooth Q-switched pulses with repetition rates of'40–200 kHz were obtained in short linear cavities of a length less than 11 cm. The highest average power of 1.4 W with slope efficiency of 20% was demonstrated in Nd:YAG laser. Long pulse duration of hundreds ns and low pulse energy of a few mJ (up to 24 mJ in the best case) were caused by low value of the ratio of the absorption cross section of V3+:YAG to emission cross section of Nd:YAG. The much higher pulse energy of 70 mJ with pulse duration of 80 ns was obtained in lower gain Nd:YLF laser in a cavity of 140 mm length with internal lens of 50 mm focal length.
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Epitaxial RE3+:YAG planar waveguide lasers
M. Malinowski, J. Sarnecki, R. Piramidowicz, P. Szczepanski, and W. Wolinski

The interest in increasing signal speed, lowering optical losses and reducing power requirements led to the integration and miniaturisation of the optoelectronics components. Planar optical devices play an increasingly important role as the components for fibreoptic communication and optical computing systems. Their purpose is to couple, switch, modulate, amplify or generate optical signal. Recent important development is successful operation of planar waveguide amplifiers and lasers that could be easily coupled to fibre components. Several waveguide fabrication techniques are employed depending on host material, including semiconductor materials, dielectric crystals and glasses.
In this work the basic problems related to active waveguide fabrication and properties will be discussed. We also report the spectroscopic and laser properties of the Nd3+:YAG/YAG epitaxial thin films obtained in ITME laboratory in Warsaw
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Investigation on passively Q-switched Nd:YAG slab laser pumped by 2D quasi cw diode laser stack
W. Zendzian, J.K. Jabczynski, and Z. Mierczyk

The paper presents results of investigations on generation of Nd:YAG triangle slab laser pumped by 2D diode array. The pump beam shape quality with respect to pump/mode overlap efficiency was investigated both theoretically and experimentally. Two cavity schemes with and without pump forming optics were verified in free running and passively Q-switching modes. Slope efficiency of 45% and output energy of 24 mJ for incident 60 mJ of pump energy were achieved in free running mode. Applying Cr4+:YAG crystal as passive Q-switch, the output energy of 5 mJ and 0.5 MW peak power were obtained in the optimised resonator.
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Spectral and generation characteristics of YAG:Nd3+ crystals with high concentration of Nd3+ ions
Z. Mierczyk, K. Kopczynski, W. Zendzian, and T. Lukasiewicz

The paper presents investigation results of optical, spectroscopic, and generation parameters of YAG:Nd3+ with higher concentration ofNd3+ ions (1.1–1.8 at. % Nd3+). YAG:Nd3+ single crystals were obtained by the Czochralski method. Investigations on optical quality were carried out using elastoscopic and interferometric methods. Absorption spectra within the spectral range of 200–3000 nm (Dl = I nm) and pumping range of 750-850 nm (Dl = 0.1 nm) were determined. Also the spectra of luminescence induced with radiation emitted by a laser diode of 808 nm were investigated and lifetime of Nd3+ ions in the upper laser level (4F3/2) was determined. In the all investigated crystals, doped up to 1.3 at.% Nd3+, the time of fluorescence decay from 4F3/2 level is 230 us. It was stated that high level of Nd3+ ions doping (above 1.33 at. % Nd3+) causes reduction of lifetime of the upper level 4F3/2 as a result of concentric quenching of luminescence. For the crystals of 1.8 at. % Nd3+ concentration, upper laser level lifetime has been educed to 183 us. Also the results of generation investigations obtained in a laser system with the examined YAG:Nd3+ active media in form of side pumped "slabs" and inform of longitudinally pumped rod.
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UHV plasma enhanced CVD system for preparation of new generation amorphous silicon based efficient solar cells
J. Jonas, P. Rava, T. Stapinski, and E. Walasek

Plasma enhanced chemical vapour deposition (PECVD) is used in the deposition of various thin films such as amorphous silicon, nitrides, oxides and diamond-like carbon. The authors succeeded in preparation of photovoltaic intrinsic a-Si:H with density of states of 1016 cm–3 and high photoconductivity gain. These films are the constituents of homojunction p-i-n solar cells or heterojunction type with silicon-carbon window layer of efficiency over 10%. The microwave plasma chemical vapour deposition (MWCVD) seems to be a promising method for the deposition of passivation layers.
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