Italian Research Laboratory Analyzes Instabilities in Carbon Dioxide Lasers

The National Institute of Optics, Florence, Italy, has demonstrated spatial and temporal instabilities in CO2 lasers. Marco Ciofini and Riccardo Meucci, Researchers, and Antonino Labate, Graduate Student, in collaboration with other INO staff members have developed an instrument that combines pyroelectric detectors and a scanning mirror to measure intensity variations through the cross-section of the beam and over time. Their measurements show unexpected patterns and fluctuations that should be taken into account by anyone designing laser equipment used for metal cutting, data storage, measurement and other applications. Key to the success of their study was the use of a data analysis software package called Origin capable of storing and graphically depicting the data generated by the measurements.

INO is a public research institution operated by the Italian Ministry of University, Scientific and Technological Research. The institution performs advanced research, certification, technical inspection, and graduate training. Its research areas are classified in three distinct research units. The lines of research pursued by the quantum optics unit include quantum optics, nonlinear dynamics, nonlinear optics and radiofrequency devices. The optical metrology unit handles Fourier optics and coherent techniques, optical testing, computer aided optical design, and diagnosis of works of art. Finally, the optoelectronics unit is responsible for non-invasive optical control, biomedical diagnosis systems and spectrometry.

Figure 1) A 3D reconstruction, plus a contour map, of the intensity profile emitted by a laser in the mid-infrared region created with Origin 5.0.

To measure the uniformity and stability of CO2 laser output, INO researchers developed a special instrument that uses a 256-pixel array of pyroelectric detectors positioned in a straight line. Pyroelectric detectors are based on the fact that ferroelectric materials such as lithium tantalate exhibit a large spontaneous electrical polarization below a temperature known as the Curie point. Incident radiation alters the temperature and changes the polarization. When the polarization changes, the charges induced in the electrodes produce a voltage across the slice if the external impedance is comparatively high. The sensor only produces an electrical output signal when the level of incident radiation changes. The process is independent of the wavelength of the incident radiation and hence pyroelectric sensors have a flat sensors have a flat response over a very wide spectral range.