Jerzy S. Witkowski

Well-ordered laser signature

Abstract It was found that the longitudinal tuning of the CO 2 laser could give a well-ordered laser signature (WOLS). The considered phenomenon was observed and investigated in an RF excited slab-waveguide CO 2 laser equipped with a confocal unstable resonator in a few configurations.

Field calibration system implementing 3-D optically modulated scatterers for immunity test site purposes

In this paper, a field calibration system for immunity test site using optically modulated scatterers is described. The presented system utilizes, designed by authors, three-dimensional optically modulated and powered scatterers. One of the most important features of using modulated scatterers is their low influence on the tested field, which allows employing an array of scatterers instead of mechanically scanned classical field sensor. The use of an array version of a measurement setup can result in a considerable reduction of the calibration time. Speed and accuracy improvements of field calibrations have been the main intention of the new calibration system development.

Computer networks based on optical passive couplers

The practical realisation of passive fibre coupler network Ethernet 10 Mb/s is presented. The passive star coupler configuration has been particularly emphasised. The practical configurations of the Ethernet 1O Mb/s-computer network using special properties of passive star fibre couplers have been described. It allows using the ordinary transceivers with simple algorithm of collision detection.

Algorithm of RF-excited slab-waveguide laser design

Basic mechanisms influencing the resonant frequency of the RF-discharged slab-waveguide CO2 laser head are described. An algorithm of calculations to design a laser head resonant frequency is given. The algorithm is experimentally confirmed.

Fourier transform in THz measurements of refractive index

A Fourier Transform is applied to the coherent detection signal in the THz photomixer arrangement. The method is used in measurements of a refractive index of plastic materials.

Prediction of the thermal properties of CO2, CO, and Xe laser media

Abstract Approximation functions describing the experimental data of thermal conductivity and viscosity of chosen gases ( CO 2 , N 2 , He , Xe , CO , O 2 , Ar) are given in the paper. Introduced formulas allow to predict thermal conductivity and temperature distribution of typical high-power laser gas mixture. Examples of temperature distribution in RF excited CO2, CO, and Xe laser media are shown. Knowledge of the temperature distribution in the laser cavity can be useful for predicting the general properties of laser.

Diffractive scanning mechanism for laser marker

Abstract We present a new idea of marking based on spectral properties of CO 2 laser radiation. The idea has been illustrated on RF excited waveguide CO 2 lasers in different configurations: single channel, multi-waveguide and slab-waveguide ones. The pulse operation of the laser has been considered as well. The advantage of the presented diffraction marker is avoiding complicated and fallible mechanical elements. The only executive elements of the marker are a diffraction grating and a piezoceramic transducer. It has been shown that the slab-waveguide configuration of the RF excited CO 2 laser equipped with an unstable resonator is the most promising configuration for application to the diffraction marker.

Synchronous measurement of inter-modulation products using a multi-frequency coherent signal

The use of a new signal, a multi-frequency coherent signal is presented for measurement of inter-modulation components caused by nonlinearity of transmission channel. This signal allows the use of digital coherent demodulation for measurement of inter-modulation components. It makes possible measurement of very weak signals, undetectable by non-coherent measurement.

A numerical analysis of pumping efficiency using the side coupling method in double-clad fiber lasers

The numerical analysis of the efficiency of the side pumping method using special asymmetrical couplers for the high-power double-clad fiber lasers is presented in the paper.

Thermodynamic processes in an RF pulsed excited CO2 slab-waveguide laser

A pulsed excitation of the laser plasma in gas lasers creates an acoustic wave in the laser reservoir. It changes thermodynamic parameters of the laser plasma in the laser cavity like pressure, and temperature, as well, and consequently it changes the density of the laser plasma, or, in other words, the refractive index of the laser medium. Tuning laser frequency during the pulse developing is observed as a result. The measurements of the pressure, temperature, and refractive index changes in an RF pulsed excited CO2 slab-waveguide laser are purposes of the work. The pressure changes are measured with calibrated microphones situated close to the laser plasma. The temperature changes are calculated via measured refractive index characteristics, and simple formulas linking the refractive index with the gas density. The picture of the acoustic wave propagation in the laser cavity is presented. The obtained results give the picture of the laser plasma behavior during the pulsed excitation. It leads to a single frequency pulsed laser operation design.