Z. Mierczyk

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.

Nd:YAP 1.34-μm/1.08-μm laser passively mode-locked and Q-switched by V3+:YAG/BDN II saturable absorbers with efficient radiation delivery through a hollow glass waveguide coated with COP/Ag

A compact, passively Q-switched and mode-locked Nd:YAP laser in oscillator-amplifier configuration was designed and constructed. Operation wavelength switching (between 1.34 and 1.08 mm) was achieved with a three-mirror cavity and mechanical shutter. For Q switch- ing and mode locking of the 1.34-mm Nd:YAP laser transition, a V 31 -doped yttrium aluminum garnet (YAG) saturable absorber was em- ployed. The optimal performance was found after variation of the reso- nator length (40 to 100 cm) and of the absorber initial transmission (52% to 89%). The duration of a single pulse in a train was around 1 ns. The saturation intensity of the V 31 :YAG absorber was determined to be 10 MW/cm 2 . A BDN II polymer thin-film saturable absorber was used forQ switching the 1.08-mm laser transition. After amplification, the maximum output energy reached was 27 mJ (train of mode-locked pulses at 1.34 mm) or 94 mJ (Q-switched pulse at 1.08 mm). The output laser radiation was delivered by means of a hollow glass waveguide coated with cyclic olefin polymer and Ag, with 95% and 80% efficiencies for 1.34 and 1.08 mm, respectively.

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.

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].

Comparison of 905 nm and 1550 nm semiconductor laser rangefinders’ performance deterioration due to adverse environmental conditions

Laser rangefinder performance (i.e., maximum range) is strongly affected by environment due to visibility-dependent laser attenuation in the atmosphere and target reflectivity variations induced by surface condition changes (dry vs. wet). Both factors have their unique spectral features which means that rangefinders operating at different wavelengths are affected by specific environmental changes in a different way. Current state of the art TOF (time of flight) semiconductor laser rangefinders are based mainly on two wavelengths: 905 nm and 1550 nm, which results from atmospheric transmission windows and availability of high power pulsed sources. The paper discusses the scope of maximum range degradation of hypothetical 0.9 μm and 1.5 μm rangefinders due to selected water-related environmental effects. Atmospheric extinction spectra were adapted from Standard Atmosphere Model and reflectance fingerprints of various materials have been measured. It is not the aim of the paper to determine in general which wavelength is superior for laser range finding, since a number of criteria could be considered, but to verify their susceptibility to adverse environmental conditions.

Wavelength tuning in Er3+,Yb3+:glass microchip lasers

The paper presents the investigation results of laser generation around 1.5 μm at different wavelengths. The shifts of the wavelength were achieved by the change of pump power, transmission of an output mirror, and length of an active medium. Mathematical analysis and explanation of this phenomenon was curried out on the basis of the change in relation between the gain and loss lines.

Practical application of pulsed “eye-safe” microchip laser to laser rangefinders

The paper describes practical application of pulsed microchip laser generating at 1535-nm wavelength to a laser rangefinder. The complete prototype of a laser rangefinder was built and investigated in real environmental conditions. The measured performance of the device is discussed. To build the prototype of a laser rangefinder at a reasonable price and shape a number of basic considerations had to be done. These include the mechanical and optical design of a microchip laser and the opto-mechanical construction of the rangefinder.