Krzysztof Kopczynski

Efficient diode-pumped passively Q-switched Raman laser on barium tungstate crystal

Abstract An efficient all-solid-state diode-pumped intracavity Raman laser was constructed. This laser was based on three-mirror linear cavity with triangular Brewster-angle-cut Nd:YAG slab crystal pumped by 300-W quasi-CW diode Q-switched by Cr 4+ :YAG saturable absorber operated at 1064 nm. BaWO 4 (barium tungstate) crystal was used as a Raman converter. After the Raman laser optimisation for the first Stokes (1180 nm) the reproducible conversion efficiency was about 40% with respect to the Q-switched laser operation at the fundamental frequency. The corresponding output energy and pulse duration was 1.46 mJ and 3.5 ns, respectively. The top reached Raman laser output energy was 2.3 mJ with the conversion efficiency of 55%.

Comparison of cw laser generation in Er3+, Yb3+: glass microchip lasers with different types of glasses

The paper describes comparison of laser generation of concentrated and SELG glasses developed at the General Physics Institute of Russian Academy of Sciences in Moscow and most recent EAT14 glass worked out by the CLaser Photonics Company in Shanghai. The laser generation was carried out using 976-nm pump wavelength in cw and quasi-cw regimes. Comparison of efficiencies and thresholds as well as of dissipative losses was made with a view to choose the best glass for “eye-safe” microchip laser range-finder. The generated wavelengths by each sample were measured.

Fluorescence excitation-emission matrices of selected biological materials

EX-EM fluorescence matrices from suspensions of 11 vegetative bacteria, 5 spores, and 14 interferents (fungi, pollens) were measured and cross-sections of the selected bacteria were calculated. The changes of fluorescence characteristics of vegetative cells during their sporulation and starvation to death as well as spores during germination are shown. Influence of culture media on emission spectra and rate of spores formation under starving conditions was examined. Analysis of the measured fluorescence characteristics shows that double- or multi-wavelenghts excitation can make it possible to distinguish between particular groups of biological material, i.e., spores, vegetative cells, proteins, and interferents.

Improved laser-induced fluorescence method for bio-attack early warning detection system

Laser Induced Fluorescence (LIF) could permit fast early warning systems either for point or stand-off detection if a reliable classification of warfare biological agents versus biological or non-biological fluorescing background can be achieved. In order to improve LIF discrimination capability, a new system is described in which the fluorescence pattern is enriched by the use of multiple wavelength delayed excitation while usual spectral fluorescence analysis is extended to time domain to use both aspects as criteria for classification. General considerations and guidelines for the system design are given as well as results showing good discrimination between background and simulants.

Optical and Luminescence Properties of YAlO3 -Tm Crystals

The results on optical absorption, photoluminescence and thermoluminescence of YAP-Tm crystals of 1 at.% and 4 at.% of Tm are presented as well as influence ofUV-, γ-radiation and thermal treatments on optical and luminescence properties of the crystals. The blue-green luminescence of defect centers was observed in YAP-Tm crystals at Ar + -laser excitation. The possibility of energy transfer processes between defect centers and Tm 3+ ions was shown.

Effect of ionizing radiation on optical and lasing properties of Y3Al5O12 single crystals doped with Nd, Er, Ho, Tm, Cr ions

Abstract The influence of gamma irradiation on optical and lasing properties of YAG:Er, YAG:CTH, YAG:Nd and YAG:Cr4+ single crystals were studied. For no thermal annealed rods from YAG:Er and YAG:CTH crystals the increase of laser output energy was established. The mechanisms of radiation sensibilization are discussed.

Pulse generation at 1.5-μm wavelength in new EAT14 glasses doped with Er3+ and Yb3+ ions

The paper describes investigation of pulse laser generation in newly developed EAT14 glasses with the use of MALO saturable absorber. Different initial transmission of the saturable absorbers and different transmission of the output coupler were investigated. The laser generation was carried out using 976-nm pump wavelength. Comparison of peak powers, slop efficiencies and thresholds was made with a view to choose the best set of glass and saturable absorber for “eye-safe” microchip laser range-finder. The generated wavelengths by each sample were measured.

Application of modified difference absorption method to stand-off detection of alcohol in simulated car cabins

Abstract Some aspects of stand-off detection of alcohol in simulated car cabins are described. The proposed method is the well-known “difference absorption” method applied to the differential absorption lidar system, modified by taking advantage of a third laser beam. The modification was motivated by the familiar physical phenomena such as dispersion and different absorption coefficients in window panes for applied laser wavelengths. The mathematical expressions for the method were derived and confirmed by experiments. The presented investigations indicate that the method can be successfully applied to stand-off detection of ethyl alcohol in moving cars.

Stand-off detection of alcohol in car cabins

Abstract The results of experiments concerning detection of alcohol vapors in car cabins using a laboratory device, which was developed and built at the Institute of Optoelectronics at the Military University of Technology, are described. The work is a continuation of the investigations presented in an earlier paper. On the basis of those results, the whole device was designed and built. Then it was investigated using a car with special system simulating a driver under the influence of alcohol. To simulate the appropriate concentration of alcohol in human blood, a special method of generation of alcohol vapor was developed.

Fluorescence/depolarization LIDAR for mid-range stand-off detection of biological agents

LIDAR [1] system for real-time standoff detection of bio-agents is presented and preliminary experimental results are discussed. The detection approach is based on two independent physical phenomena: - laser induced fluorescence [2], - depolarization resulting from elastic scattering on non-spherical particles [3].