the significance of laser beam testing for...

The First

International Proficiency Testing Conference

Sinaia, România 11th − 13th October, 2007

312

THE SIGNIFICANCE OF LASER BEAM TESTING FOR THE

DIFFERENT LASER APPLICATIONS

Teodor Necsoiu, Constantin Dragomirescu SC Optoelectronica – 2001 SA, Strada Atomistilor Nr. 409, Magurele, Judetul Ilfov,

Romania, 077125 [email protected], [email protected]

Abstract It is made a short presentation of SC Optoelectronica - 2001 SA. Taking into consideration the expansion of the optoelectronic domain in the last decades, especially of the lasers, and also the European New Approach Directives regarding the quality, it was necessary to develop in SC Optoelectronica a laser beam testing laboratory, accredited by RENAR, Romanian Organism for Accreditation. For most applications of lasers the beam laser must be of very good quality. Therefore the laser beam must be characterized from many points of view, like that: power, energy, laser beam sizes, beam shape, beam divergence, power/energy distribution, spectral band, impulse repetition rate, pulse duration, M2 propagation factor, positional stability a.s.o. Therefore, it will be presented some consideration regarding the quality of laser beam for different applications. General objective of laboratory consists in developing of capacity in certification and evaluation domain for assuring the implementation of European specific legislation transposed in national legislation. The laboratory carries out laser and laser equipment/device testing in order to apply on them CE mark by accredited organisms of product certification as a result of them collaboration with laser beam testing laboratory. It is presented measurements/tests, correspondent standards and measurement uncertainties. Also, it is presented both the testing equipment and their main specifications, without mentioning types and companies and the results obtained by the laboratory in carrying out tests and measurements. Key words Laser, beam, testing, radiation, measurements, propagation, divergence, power, energy, pulse, spectral band, repetition rate, stability, density, size, size, duration

Teodor Necsoiu, Constantin Dragomirescu: The significance of laser beam testing for the different laser applications

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1 A SHORT PRESENTATION OF THE SOCIETY

SC OPTOELECTRONICA – 2001 SA is o private company, with the main activity object research &development in optoelectronic field. The main activities of the society are: research and technological development and innovation in physics, advanced electronics, optoelectronic devices development for special applications, advanced technological developments in the optoelectronic domain. Besides this, society has a small fabrication line for optoelectronic devices (night vision devices, lasers and laser devices, false document analyzers, medical equipment) destined to the civilian and military applications. Also, the society carries out thermovision services, optical and laser testing, mechanical CNC processing services. SC Optoelectronica SA has implemented an ISO 9001:2001 certified Quality System. 2 GENERALITIES Taking into consideration the expansion of the optoelectronic domain in the last decades, especially of the lasers, and also the European New Approach Directives regarding the quality, it was necessary to develop in SC Oprtoelectronica a laser beam testing laboratory, accredited by RENAR, Romanian Organism for Accreditation. For most applications of lasers the beam laser must be of very good quality, therefore the laser beam must be characterized from many points of view, like that: laser beam sizes, beam shape, beam divergence, power/energy distribution, spectral band, impulse repetition rate, pulse duration, M2 propagation factor, pozitional stability a.s.o. Spatial beam quality , that is beam diameter and M2

propagation factor are the critical parameters for a large range of applications, because this quality determines how large the beam will be at some point along the propagation path. For some applications the beam profile is of the major importance. When the beam profile is important, it is usually necessary to measure it to insure that the proper profile exists. For some lasers and applications this may only be necessary during the design or fabrication phase of the laser. In other cases it is necessary to monitor the laser profile continuously during the laser operation, for example: scientific, industrial and medical applications. Also, there is equipment that can make statistics measurement. Statistics on all measurements can provide information on long term stability of the laser beam. This enable one track the stability of a laser with respect to time , temperature fluctuations or other characteristics of interest. Statistics typically provide the mean or average measurement of a parameter, the standard deviation and the minimum and maximum to which that characteristic has drifted. For industrial processing are very important the power of the laser and beam radius. It is vital to know exactly position and power distribution density in the focus of optical system. Generally, for industrial lasers there are very important the parameters as average power, energy/pulse, spatial and temporal profiles of the beam. For medical laser very important parameters are: average power, energy/pulse, laser beam profile , stability, focus , beam radius. Laser beam parameter measurement laboratory was developed in the frame of a project financed by Economy and Commerce Ministry, being in the accreditation stage by RENAR. In the same time there is a new contract in performance that have as objective the extension of the testing range and developing of new testing methods. This contract is financed by Romanian Research Authority in the frame of CEEX Programme.


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We had in attention the actual situation in Romania. In present, there is not an accredited laboratory able to provide a complete characterization of laser beam. Of course, during the time the research institutes and enterprises carried out laser testing for research needs and for production needs, sometimes with improvised methods. In our days the testing equipment were modernised so that the research institutes and enterprises carry out partial beam measurements with modern equipment. 3 OBJECTIVES OF THE LABORATORY General objective of laboratory consists in developing of capacity in certification and evaluation domain for assuring the implementation of European specific legislation transposed in national legislation.The laboratory proposed to carry out a large range of specific testing for regulated domains by the European New Approach Directives regarding the quality and by 608/2001 national law regarding to product evaluation conformity in regulated domains: medical apparatus, industrial machineries, personal protection equipment. The laboratory carries out laser and laser equipment/device testing in order to apply on them CE mark by accredited organisms of product certification as a result of them collaboration with laser beam testing laboratory. It is followed that in the close feature the laboratory to be accredited by The RENAR and then at European level and after that to be integrated in a laboratory network for carrying out of comparative measurements. 4 ACTIVITIES CARRIED OUT BY THE LASER BEAM TESTING LABORATORY The laboratory is organized and carries out its activity on the rules of SR EN ISO 17025:2005. Taking into consideration the requirements of standard it was designed and implemented a Quality Management System, that represents the base of performance of all activities. The main objective of the company and of the laboratory in the quality domain is complying with all contractual requirements of clients, keeping agreed schedule, offering attractive prices, all of them based on respect and sincerity relative to client. The general objectives of the company and laboratory in the quality politics are:

● increasing of client satisfaction; ● increasing of company prestige and creation of an excellence image; ● increasing of efficiency and operational efficiency of all activities;

● continuous improvement of the delivered products/services. Testing/measurement are based on the specific standard requirements. Below, there are presented the measurements/tests and correspondent standard:

● cw laser beam power, SR EN ISO 11554:2004; ● pulse laser beam energy, SR EN ISO 11554:2004; ● laser beam temporal characteristics, SR EN ISO 11554:2004; ● laser beam widths, SR EN ISO 11146:2003; ● laser beam divergence, SR EN ISO 11146:2003;

● laser beam M2 propagation factor, SR EN ISO 11146:2003; ● laser beam power/energy density distribution SR EN ISO 13694:2003; ● laser beam positional stability, SR EN ISO 11670:2003; ● laser beam polarization, SR EN ISO 12005:2004;


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● laser beam spectral characteristics, SR EN ISO 13695:2004; ● shape of laser beam wavefront, SR EN ISO 15367-2/2005; ● laser wavelength measurement – it is not a special standard,

but themeasurement is carried out with a precise equipment, with a soft dedicated to. The staff and personnel of the laboratory are able to carry out the tests with professional ability and to develop a constant activity for improving the testing methods, in accordance with the requirements of reference standard regarding continuous improvement. 5 TESTING/MEASURING EQUIPMENT For carrying out the tests, the laboratory is endowed with the up-to-date testing equipment, that exist on the international market. For measuring the power and energy , the laboratory uses a very good powermeter/energymeter, endowed with 4 measuring heads assuring the possibility to measure powers of µW order to W order (without attenators) and energies of µJ order to J order (without attenators), for wavelength of 150 nm to 11990 nm. With calibrated attenators power and energy range increses significantly , assuring the caracterization of all usual lasers. The equipment is provided with specific software that have a lot of facilities. The calibration accuracy of powermeter/energymeter is 0,0139%. The uncertainty of measuring heads is better than 3%. For beam laser temporal measurements and stability of temporal parameters of the laser pulses there are used ultra fast detectors and digital storage oscilloscope of very wide band. The laboratory is able to carry out measurements in 700-1800 nm spectral range, with the possibilities for extending it and measuring uncertainty is better than 2%. For measuring of laser beam widths, laser beam divergence, laser beam power/energy density distribution, laser beam positional stability, the laboratory has a laser beam profile analyzer with various performances. It works with CCD Camera that assures laser beam diagnostic in 190-1605 nm spectral range, with possibilities of extending in the future to the greater wavelengths acquiring another types of cameras. The calculation program assured by the specific soft is able to supply the above data, with the possibilities of analizing the beam shapes, statistics, hystograms a.s.o. The dimensions of laser beam are determined with uncertainties of µm order. For determination of the laser beam polarization there are used liniar polarizers, λ/4 wave plates and the above mentioned powermeter/energymeter. For the other laser beam parameters there are used various equipment such as: laser spectrum analyzer, M2 Beam Propagation Analyzer, Wavelength Meter that are also up-to-date equipment , provided with specific softwares assuring a very high accuracy level of the measurements.


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6 THE CARRIED OUT TESTS IN THE LABORATORY In the laboratory were carried out the internal tests for a series of existing lasers in the society. Thus, there were complete characterized cw lasers (He-Ne, He-Cd, semiconductor lasers), pulse lasers (especially Yag:Nd lasers), with powers between a few mW and hundreds mW for cw lasers and energy between mJ and hundreds mJ, for pulse lasers and pulse widths between 7-20 ns. Tests carried out had as aim to verify the testing procedures and testing working instructions. Below, it is prezented a testing arrangement for laser beam divergence measurement.

Figure 1 Testing arrangement for laser beam divergence measurement In the next figure it is presented He-Ne laser beam shapes, in 3D si 2D, as they results testing them with a laser beam analyzer.


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Figure 2 He-Ne laser beam shapes: 3D (top); 2D (bottom) REFERENCES [1] [2] [3] [4] [5]

Dumitras D, Ingineria fasciculelor laser. Editura BIC ALL, 2004 Dr.ing. Popescu N , ing. Opran M, Laseri, aplicatii, Editura Militara, Bucuresti 1979 SR EN ISO/CEI 17025:2005 – Cerinte generale pentru competenta laboratoarelor de incercari si etalonari SR ENV 13005:2003 Ghid pentru exprimarea incertitudinii de masurare SR EN ISO mentioned above for laser beam testing

the significance of laser beam testing for...

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