In this paper we present prospecting single crystal materials for light generation. We describe basic property borates like: Ca4GdO(BO3)3-(GdCOB), Ga4YO(BO3)3-(YCOB), Sr3Y(BO3)3-(BOYS) doped with Yb, Pr, Nd, Sm, Tm. These crystals turn out laser and non linear optical (NLO) properties. We show KY(WO4)2-(KYW) and KGd(WO4)2-(KGW) belonged to double vanadates group, and flourides LiCAlF6-(LiCAF) and LiSrAlF6-(LiSAF), their properties and growth methods. Interesting group of materials which can be used as source of light are organic compounds. Examples of these materials are presented.
Problems of ultra-violet wavelengths generation in rare-earth doped crystals and glasses are discussed. Examples of UV interconfigurational transitions of praseodymium (Pr3+) ion in different hosts are presented and discussed and UV intraconfigurational transitions of holmium (Ho3+) ion in ZBLAN glass optical fiber after upconversion pumping are reported.
In this paper, we present an analysis of gain enhancement in 1D photonic crystals. In our theoretical model, for the first time, we take into account the gain saturation effect. The special algorithm is develoepd to obtain characteristic of gain enhancement with gain saturation effect. That algorithm allows to define in easy way the influence of the real structures parameters (for example photonic crystal primitive cell geometry) on the gain enhancement.
Literature referring to superconductor optoelectronic switches report about curious phenomenon of improvement of dynamical properties as a result of introduction of a thin, low thermal conductivity buffer layer. Present paper is a trial of interpretation of this phenomenon basing on analysis of non-stationary temperature fields within the element's structure. The analysis has been made using the method of numeric modeling of thermal processes occurring within the thin-layer structure consisting of high-temperature superconductor YBa2Cu3O7-x sputtered over the LaAlO3 substrate and separated with an intermediate SrTiO3 layer. Numerical modeling is very difficult due to strong nonlinearity of resistivity in relation to temperature and current. The essential reason of shortening of key's switch-off time is the fact that the buffer layer limits heat diffusion towards the substrate during switching-on time; as a result its switching-off occurs through heat abstraction towards the high thermal conductivity substrate which temperature is lower than the superconductor's switch-off temperature.
The method of selective deposition of GaN layer using combination of additional AlN and GaN films has been presented. All layers have been reached by lift-off technique and were etching ALN and dry etching GaN.
The investigation results of wideband (8-12 μm) antireflection coatings on germanium substrate and spectral characteristics of interference wideband filter for spectral range of 8-12 μm are presented. For design of filters and antireflection coatings the following layer materials were used: Ge, ZnS and Mira, and substrate materials such as: Ge for antireflection coatings and ZnSe for interference filters. Wideband filter for the range of 8-12 μm requires application of additional two filters cutting off radiation from the range of 1-7 μm. The cutting off filters are interference filters for which construction germanium, Mira, and ZnS were used. The constructions of basic and cutting off filters were designed considering technical possibilities of vacuum device BAK 550 of the Balzers firm.
Thin films of zirconia were deposited on quartz substrates by conventional reactive electron beam deposition and ion-assisted deposition. The influence of the post-deposition annealing between 400°C and 900°C on the structural and optical properties and on the surface morpohology was investigated. It is shown that after post-deposition annealing the ZrO2 films the degree of order becomes higher. The contribution of the monoclinic phase increases with the rise of annealing temperature. The post-deposition annealed (temperature range: 700-900°C) samples exhibit lower threshold to damage for the radiation of pulse Nd:YAG laser. Correlation between the observed film properties and laser damage threshold is discussed.
The connections of the telecommunications tract elements have a significant influence on the quality of the information transmission. In the essay reasons and an analysis of the losses in fiber optic connectors are introduced. The case of fiber optic connectors: PC type and with a surface enlargement are emphasized. Different types of fiber sleeve connectors are discussed. These optical connectors can be divided according to following criteria: structure (ST, FC, Sc, E-2000, F-3000, LC, MT-RJ, MU, etc.) types of applied ferrules (monolithic, with multiple elements) technology of production (standard, Light Crimp - AMP, Hot Melt - 3MCrimp Lok - 3M, Universal Com Lite - Siecor) and tuning. Moreover the quality of DWDM fiber optic connectors, which have high functional density and an impact on the light polarization is touched on. The results of measurements of transmission parameters and of mechanical resistance on vibration, folding of the cable in the fiber, strikes on hard surfaces, multiple connection and disconnecting, pulling out of a cable from the connectors and climate conditions are discussed. The results of the measurements listed above with additional interferometric tests of ferrule head constitute the main factor of the fiber connectors quality analysis. Furthermore, the up to date results of the compatibility analysis of the connectors manufactured by different producers are mentioned and a future development in the field is forecasted.
The aim of work is to present results of interferometric measurements research of fiber connectors. The values of parameters are essential for attenuation and reflectance of connectors. There are presented result for PC and APC connectors and compared with international standards requirements (IEC standard, Bellcore standard).
The work presents simulation of transmission line results with the fiber standard ITU-T G.652. The parameters of Lorenz laser decide about electrical signal parameters like eye pattern, jitter, BER, S/N, Q-factor, scattering diagram. For a short line lasers with linewidth larger than 100MHz can be used. In the paper cases for 10 Gbit/s and 40 Gbit/s transmission and the fiber length 30km, 50km, and 70km are calculated. The average open eye patterns were 1*10-5-120*10-5. The Q factor was 10-23dB. In calcuations the bit error rate (BER) was 10-40-10-4. If the bandwidth of Lorenz laser increases from 10 MHz to 500MHz a distance of transmission decrease from 70km to 30km. Very important for transmission distance is a rate bit of transmitter. If a bit rate increase from 10Gbit/s to 40 Gbit/s, the transmission distance for the signal mode fiber G.652 will decrease from 70km to 5km.
There are presented the results of measurements of optical connector reflectance. The research BD ("branching device") method of reflectance measurements have given the dependence on patchcord (fiber) length. The value of reflectance depends on the Rayleigh scattering at the place of mandreling obtained for BD measurement method. The correct measurements of connectors reflectance are made when distance between connector and modes cutoff place is 2-5 meters. The slope of reflectance curve is variable: 2dB/m (for the cut place 0-1 m), 0.5dB/m (2-5m).
The idea of coherent optical communications with frequency division multiplexing gives larger possibilities and new qualities compare to IM-DD (Intensity Modulation - Direct Detection) systems. However, optical coherent systems are much more complicated in realization then their "radio" counterparts. These optical FM systems require stable and controllable offset lasers. Heterodynes of microchip lasers with offset frequency stabilization are presented.
An original semiconductor programmable light source has been designed and constructed. It consists of the controller module and the stabilized optical head comprising an optical feedback loop. The radiation emitted by the light source proposed can be generated in the continuous or pulse mode and its brightness can be adjustable in a wide range.
Threshold current and differential quatnum efficiency of broad contact lasers with optically asymmetric mirrors is discussed with the purpose to reveal factors essential for optimization of the power efficiency of such lasers.
An advanced 3D model of a room-temperature (RT) continuous-wave (CW) VCSEL operation is used to investigate a possibility of reaching a RT CW single-fundamental-mode operation of nitride VCSELs. A nitride VCSEL of a traditional, double-ring-contacted structure has been found to generate at RT simultaneously many higher-order transverse modes which is a direct consequence of an unavoidable strong current-crowding effect at edges of its active region. Various possible structure modifications of nitride VCSELs have been examined to improve uniformity of the current injection into active regions which seems to be crucial for achieving their RT lasing operation and improving their mode selectivity. Both semi-transparent contacts and tunnel junctions have been suggested as useful tools to enhance considerably radial current flows in the nitride VCSEL structure. They should be, however, properly arranged within the laser cavity not only to improve the radial current sperding between the top ring contact and the centrally lcoated active region but also they should not introduce additional optical losses within a semi-transparent contact and highly doped tunnel junctions.
The influence of CG-DFB laser parameters on the statistical properties of generated light is analyzed. In our paper we concentrate on the effects resulting from the nonorthogonality properties of laser modes. The semi-classical approach based on stationary and time-dependent solution of the Fokker-Planck equation is used. Numerical results obtained for CG-DFB structure with external outcoupler reveal the behavior of statistical parameters of light such as the mean laser intensity, intensity fluctuations and the laser linewidth as the functions of the realistic parameters of considered device.
This work presents the possibility of modification of semiconductor laser characteristics by a superposition of stresses introduced during technological process. A short description of the most often introduced stress mechanisms and their theoretically expected influence on laser diode emission characteristics are outlined. Experimental results of combination of stress (or strain) mechanisms introduced both by a MOVE growth of lattice-mismatched GaAsP active layer in AlGaAs heterostructure and by H+ and He+ implantation used for stripe definition are presented. It has been shown that He+ implantation-induced strain can be considerably stronger with respect to lattice-mismatch originated strain then it has been evaluated so far in literature, giving possibilities of new solutions in optoelectronics design.
This paper presents results of the investigated levels of Catastrophic Optical Damage of the SQW-SCH lasers mirrors coated with AlN (λ/4n) layer. These results have been compared with COD levels of this same type of the lasers with mirros coated by Si3N4 (λ/4n), thick AlN (3λ/4n) layers, and without coatings.
We have developed resonant-cavity light emitting diodes (RC LED) with very good emission characteristics. RC LEDs proved to be more tolerant to the epitaxial growth parameters and device fabrication procedures. As relatively robust devices they are less sensitive to typical for VCSEL manufacturing challenges and seem to have great potential for applications. Comparing to classical LED the spectrum of RC LED is concentrated into a narrow line with less than 2 nm halfwidth. The RC LED spectrum is determined mainly by the cavity resonance; its width decreases with the increase of the cavity finesse and the intensity increase reflect the on axis cavity enhancement. Additional, favorable RC LED property is its emission characteristic directionality which depends on the tuning between QW emission and cavity resonance. We have optimized the series resistance of diodes. The best results have been obtained for digital alloy graded distributed Bragg reflector (DRB) interfaces. The MBE grown structures were tested extensively prior to the device fabrication by reflectivity and photoluminescence. The assembled diodes were subjected to electrical and optical tests. Generally we have found very good correlation between the results of optical test (PL maps) on as grown wafers and probe tests on final devices.
The state of development of constructions and technology of elements used in high-power fiber laser systems is presented. Laser working conditions related to constructions and new technology limit maximum cw-output power and level of energy (pulse regime). The analysis concerns recent available active dopants used in active optical fiber lasers and methods of its activation. The perspectives of progress of high-power fiber lasers have also been presented.
We present the results of investigations on OPO systems, operating at the 'eye safe' region λ=1.5÷1.6μm. The peak power of 0.65 MW with 1.9-mJ energy at 1572 nm-wavelngth was demonstrated in a simple singly resonant OPO intracavity pumped by passively Q-switched Nd:YAG slab laser with 300 W quasi-cw diode array as a pump unit. The KTP crystal, of 5×5×20 mm3 size, 'x-cut' for non-critically phase-matched parametric generation at the signal wavelength of 1572 nm, was used as nonlinear converter. The five-fold shortening of signal pusle duration with respect to 1064-nm pump radiation was observed. The conversion efficiency of 44% with respect to 1064-nm pump energy and 3.8% with respect to diode pump energy was demonstrated. As a pump source for the extracavity OPO with PPLN (Λ=29.6 μm) the diode pumped acousto-optically q-switched Nd:YVO4 laser of 2.5-W average power was used. The conversion efficiency of 43% was demonstrated. The pulses of 110 μJ energy, 7.8 ns duration and up to 10 kHz repetition rate were obtained. The signal wavelengh was temperature tuned from 1.510 μm to 1.560 μm.
The diode side pumped lasers heads for rod and slab active elements were elaborated and characterized under real pumping conditions. Model of side pumped laser elements of rod or slab shape enabling estimation of overlapping efficiency and threshold was developed. It was shown in experiments that the optical performance for both types of heads is delimited by transversal, asymmetrical thermal gradients resulting in high level of depolarization and diffraction losses. The fundamental mode limit is about 20 W per 1 cm for a head side pumped by single diode bar.
Comparison of characteristics of three laser materials doped with Yb3+ ions pumped with high power laser diodes in the end-pumped configuration is presented. The investigated materials are 10%Yb:KY(WO4)2, 10%Yb:KGd(WO4)2, 10%Yb:YAG disk and 10%Yb:YAG rod in semi-spherical configuration.
In this paper, for the first time we present an analysis of the nonlinear operation of the F-P and DFB lasers based on photonic crystal structure. In our theoretical mode, we take into account the gain saturation effect, transverse and longitudinal field distribution. That model allows to define in easy ways the influence of the real structures parameters (for example photonic crystal cell geometry) on the normalized small signal gain.
In this paper, fundamental problems connected with optical amplifiers and multichannel transmission are considered. A type-based division of optical amplifiers and their possible applications in optical transmission lines are presented. The physical phenomena occurring in optical amplifiers, particularly in EDFAs (Erbium Doped Fiber Amplifiers), are discussed. A method of optimizing the basic parameters (gain, noise, etc.) of EDFAs is given. The properties of EDFAs and the latter's applicability to optical transparent networks are considered. How to increase the capacity of telecommunications lines is a topical issue. In this paper, ways of achieving a wide waveband for an optical transparent network through the use of a set-up of hybrid (Raman and EDFA) optical fiber amplifiers are presented.
Results of research on metal ion lasers are presented. They were obtained using novel diagnostic methods for measurements lasing parameters of noble gas-metal vapor systems and determination of metal atom diffusion coefficients in noble gases. Influence of helium 3He isotope on plasma and laser parameters in He-noble gas and metal atom mixtures was studied as well as some elementary processes in noble gas discharges for laser generation.
The results of mode spectrum investigations of commercial internal mirrors 543 nm HeNe laser are presented in this paper. Measurements of the laser Zeeman frequency were done for 543 nm HeNe laser tube placed in longitudinal magnetic field. Obtained results were applied for frequency stabilization of 543 nm HeNe commercial laser.
The results of investigation of saturation spectrum of iodine 127I2 hyperfine transitions for 543 nm HeNe laser radiation are presented in paper. Commercially available internal mirror green HeNe laser tube emitting at 543.5 nm and short external absorption cell were used in investigations. The 19 absorption components were observed, the parameters of obtained components can be suitable for frequency stabilization of 543 nm HeNe laser.
In this paper a new construction and technology of argon laser discharge tube is presented. The discharge capillary consists of silicon carbide discs brazed to copper segments. Basic parameters of the new tube (laser output power and magnitude of a gas pumping effect) were measured. These parameters are better in comparison to classical metal-ceramic laser tube.
Results of the investigations of pulsed CO2 laser plasma are presented. Theoretical calculations of temperature and pressure changes and their influence on laser tuning during the pulse evolution have been experimentally proven. The laser slab-waveguide structure equipped with an unstable resonator has been used in the experiment.
The design properties and preliminary tests of a deformable mirror with a shape controlled by adjusting the pressure of the cooling medium are presented in the paper. The mirror, used as a rear mirror of a stable cavity, was tested under conditions of a transverse flow cw CO2 laser operation. The tests proved that the use of the variable focal length mirror in the laser cavity allows the dynamic changes in the resonator configuration and thus the dynamic and controllable changes in the laser output characteristics.
The state-of-the-art and the trends in development of table-top soft x-ray lasers (XRLs) with a special emphasis on the work of the Max Born Institute (MBI) are presented. Both, basic physics and some features of the output radiation crucial for applications are discussed as well.