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R.6.2 Lasery Optoelektronika 2014

R.6.2 Lasery Optoelektronika 2014. Dr hab. inż. B. B. Kosmowski. 1. Active material : Ions in crystals (eg. Fe 2+ , Dy 2+ , Cr 3+ , Ti 3+ , Nd 3+ , Pr 3+ , Dy 3+ , Ho 3+ , Er 3+ , Tm 3+ , Yb 3+ ), Atoms ( e.g . Cu, Ne, I), Ions ( e.g . Cd + , Ar + ),

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R.6.2 Lasery Optoelektronika 2014

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  1. R.6.2 LaseryOptoelektronika 2014 Dr hab. inż. B. B. Kosmowski

  2. 1. Activematerial: • Ionsincrystals (eg. Fe2+, Dy2+, Cr3+, Ti3+, Nd3+, Pr3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+), • Atoms (e.g. Cu, Ne, I), • Ions (e.g. Cd+, Ar+), • Molecules (e.g. ArF, CO, CO2), • Gases, • Dyemoleculesinsolutionsorsolids, • Electron-holpairsin semiconductor material, • Multi-ionizedatomsinplasma. • 2. Pumping energy source: • Pumpingrequires: • Thelightfrom a flash-lamp, • Radiationfromanother laser, • Electricaldischarge, • Chemical reaction, • Electric current to causeelectroncollisions. • 3. Optical (open) resonator – createsopticalfeedbackmechanismessential for formation of laser oscillationsinsidetheresonator: • system of two(ormore!) mirrorsorotherreflectingopticalelements (prisms).

  3. Laser classification: • Active medium lasers can be classifiedinto five groups: solid state, semiconductor, gas, liquid, and plasmalasers, • Wavelengthsgenerated by laserscan be dividedinto: infrared, visible, ultraviolet, and X-raylasers, • Energy levelsinvolvedinstimulatedemissionlasersaredistinguished as: electron, ion, and molecular (rotational, vibrational, rotational-vibrational) bandsin semiconductor lasers, • Pumpingmethods:the systems aredividedintolaserspumpedoptically, by electric discharge, by electronbeam, by expansion of compressed gas, by chemical reaction, by recombination, etc., • Time development of theradiation: laserscan be dividedintocontinuous (cw) lasres, pulsed, and quasi-continuous, • Regime of operation: laserscan be free-running, Q-switched, and mode-locked, • Safetyprecautions: lasersaredividedintofourcategories.

  4. Properties of laser radiation: • Monochromaticity, M=/ • Directionality - kolimacja, gęstość strumienia • Coherence - droga spójności • Brightness - Luminancja P – moc / strumień, A – powierzchnia,  - kąt bryłowy

  5. Laser radiationparametrs

  6. Laser radiationparameters • Continuos (cw), • Pulsed, • Free-running, Q-switched, mode-locked.

  7. Laser parameters: • -free-runningregime, • Q-switchedregime, • Mode-lockedregime • Time characteristicis a significantparameter of thegeneratedoutputradiation, power of theradiation. Theinteracting time scalecanvary by 15 orders of magnitude.

  8. Energy and power of Laser radiation Peakpower Averagepower Fluenceor energy density Intensity, irradiance, orpowerdensity Radiationdoseor radiant exposure Radiant intensity

  9. Spatialstructure and divergence of the laser beam Beamdiameteristhewidthatwhichthebeamintensityhasfallen to 1/e2 (13,5%) of itspeakvalue.

  10. The spot radius at a distance z fromthebeamwaistis: The near field and the far field: The Rayleigh range (legth) isdefined as: Thebeamqualityfactororbeampropagationfactor, M2 , describeshow far thereal laser beamisfrom a so-called „perfectGaussian” one. Non-perfectbeam, thevalue of M2 > 1

  11. Beamparameterproduct (BPP) (mm x mrad): • Theproduct of beam radius (measuredatthebeamwaist) and thebeamdivergencehalf-angle (measuredinthe far field), • Thesmallest possibile BPP – Gaussianbeam. • In thiscase • BPP=  / 

  12. Laser beamfocusing 2wo’ 2wo’ – średnica w ognisku, F – liczba soczewki D – średnica promienia f - ogniskowa soczewki

  13. Summary: • Wavelength (μm), • Wavenumber k (cm-1) k=1 / , • Pulsewidth (duration) , • Repetitionfrequency (repetitionrate) frep (Hz), • Pulse energy E(J), • PeakpowerPpeak(W) (pulsed laser orquasi-cw laser)- generated energy E(J) per length of thepulse (s): • Ppeak= E / , • Averageormeanpower P(W) (pulsed laser orquasi-cw laser)- generated single pulse energy E(J) multiplied by repetitionfrequencyfrep (Hz): • Pave= E · frep,

  14. Power (cw laser): • P(W) – generatedoutput energy per second, • Beam spot size A(cm2), refers to thearea of the laser beam on the target (A=w2), • Energy density (fluenceor energy dose) F(J/cm2) – theamount of energy E(J) delivered to thetreatedarea A(cm2) F=E/A, • Intensity, irradiance, powerdensity I (W/cm2) – power P(W) per irradiatedarea A(cm2) • I = P / A, • Laser beamdivergenceangle (rad) – isdefined by beamqualityfactor M2, generatedwavelength  (cm), and a spot radius atthebeamwaistwo(cm) •  = M2  / ( wo).

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