2012-11-04Tutorial Zemax 9:Physical optical modelling I9Physical optical modelling I19.19.2Physical Beam Propagation........39.3Polarization...79.4Polarization II.........119Physical optical modelling I9.1Gaussian BeamsConsider a simple model of a basic mode(TEMoo)laser resonator at a wavelength of 632.8 nm.Theretroreflecting mirror is plane and here the gaussian beam waist has a size of wo=0.3 mm.After a distanceof 50 mm,a thin ideal lens with focal length f=150 mm is located inside the resonator.The outcouplingmirror has a radius of curvature of R2=-100 mm(concave).a)Determine the distance between the lens and the outcoupling mirror to get a stable gaussian fundamentalmode.Prove the result with the gaussian beam transformation menue.What is the 2w-diameter of thebeam at the outcoupling mirrorb)If the outcoupling component is a lens with 5 mm thickness and made of quarz,determine the outerradius to get a divergence of the outgoing laser beam of 0=10 mrad.c)What is the distance behind the resonator,where the beam diameter is 5 mmSolution:The resonator data ar established as follows:Semi-DLanetertandardtandardThe thickness after the lens is set as variable.In the merit function,the operator GBPR is set at surface 4with a target value of-100 mm.An additional virtual surface with distance 0 to the outcoupling mirror mustbe introduced here,because the radius of curvature is measured behind the surface(incorporating therefraction at the surface).GBThe optimization delivers the desired distance d =75.1126 mm.The gaussian beam transformation confirmes the radius of curvature of-100 mm.The beam diameter at theoutcoupling is 2w=0.323 mm.2Input Beam Parameters::3.00000E-001Surt 1 to waist distance:0.00000E+000M Squared:1,00000E+000Y-Direction:Fundamental mode results:Sur51zeWaistRadiusDivergenceRayleigh13.00000E-0013.00000E-0010.00000E+000Intinity6.71422E-0044.46日13E+0023.01873E-0019.82819E-002-1.39267E+002-1.55780E+0022.04947E-0034.79546E+00133.01873E-001-1.55780E+0022.04947E-0034,79546E+00141.64156E-0019.82819E-002-6.41547E+001-1.00000E+0022.04947E-0034.79546E+0011.64156E-0011.40024E-001-3.37287E+0029.32505E-0041.50159E+00261,61772E-0011.40024E-001-5,63183E+0019,73394E+001IMA1.61772E-0011.40024E-001-5,63183E+001-2,24558E+0021,43851E-0039,73394E+001b)Now the outer radius of the lens is set as variable while the distance da is now fixed.In the merit function.the operator GBPD is used with the corresponding parameters.The result is a radius of R=9.539 mm.Input Beam Parameters:Waist size:3.00000E-001Surt 1 to waist distance:0.00000E+000M Squared:1,00000E+000Y-Direction:Fundamental mode results:Radius13,00000E-0013.00000E-0010,00000E+000Infinity6.71422E-0044.46813E+00223.01873E-0019.82819E-002-1.39267E+002-1.55780E+0022.04947E-0094.79546E+0013.01873E-0019.82819E-002-1.39267E+002-1.55780E+0022.04947E-0034.79546E+0011,64156E=001=1.00000E+0022.04947E=003STO1,64156E-0011,40024E-001-9,18785E+001-3.372872+0029.32505E-0041.50159E+0021.61772E-0012.01420E-002-1.60508E+001-1.63035E+0011.00000E-0022.01413E+000IMA1.61772E-0012.01420E-002-1.60508E+001-1.63035E+0011.00000E-0022.01413E+000c)Now the operator GBPW is used with target 2.5 mm and the last thickness is taken as variable.Sincethere are always two possible solutions for a quadratic gaussian beam matching problem,a positive startingvalue for the distance is necessary here.The desired distance is d =266 mmY-Directioni3.01782619-0.8484761,61772E-0012.01413E+0009.2Physical Beam PropagationTake the system of the previous exercise to evaluate the data by a more rigorous diffraction beampropagation.a)First check the beam diameter at the outcoupling mirror.b)Check the beam curvature and the final divergence of the outgoing beam.c)If a plano convex lens is with focal length f 30 mm,thickness 3 mm and of BK7 is used in a distance of400 mm behind the resonator,calculate the obtained focus width.Compare the result with the ideal caseof an unperturbed gaussian beam.d)The last transition is a far field propagation.Try to improve the resolution be resampling the POP at thelast surface or by using another operator.Solution:The data are as follows:StandarFor the beam data,a x-width of 4 mm and 1024 sampling points are used to get a proper resolution of theprofileZPOP Settings1024X-Wicth:Y-Sampling1024Y-Width:4Beam TypeWaist Y0.3Aperture XOrder XThe result of the beam profile is quite near to a gaussian beam.