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DarkF Mikael LAVAL (OCA – Artemis)

DarkF Mikael LAVAL (OCA – Artemis). Authors:. Jean-Yves VINET (OCA – Artemis) Mikael LAVAL (OCA – Artemis). Language: Fortran90. SUMMARY. Introduction DarkF using The three kinds of simulation The simulation parameters Results given by an automatic simulation

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DarkF Mikael LAVAL (OCA – Artemis)

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  1. DarkFMikael LAVAL (OCA – Artemis) Authors: Jean-Yves VINET (OCA – Artemis) Mikael LAVAL (OCA – Artemis) Language:Fortran90 R&D Meeting

  2. SUMMARY • Introduction • DarkF using • The three kinds of simulation • The simulation parameters • Results given by an automatic simulation • What can we simulate with DarkF? • To be done • Conclusion R&D Meeting

  3. Introduction • DarkF is an optical simulation code using a plane wave decomposition to propagate the wavefronts. • It uses the Fourier transform method to propagate the beam. • Beams and mirrors are sampled on a grid (x,y) and the DarkF resolution is depending of the grid size and of the point number (typically a size of 0.7m (larger than a mirror) with 128*128 points). • We can include mirror maps in the simulation after a treatment by another program (extract.f90). • We can simulate simple systems such as Fabry Perot cavities (locked or not), Michelson interferometers or complex systems as Virgo (for the carrier and for the sidebands). • As we have no map of the splitter inclined by 45°, we can only include maps in front view for the splitter in DarkF. R&D Meeting

  4. DarkF utilization DarkF is a complex code but it has been coded to have a semi-automatic version. DarkF is composed by a main program, 7 modules and 3 parameter files. The user has just to modify the parameter list and to choose one of the first two kinds of simulation he wants to do. Afterwards he launches the program and obtain the result files. The three “kinds of simulation” One of the DarkF parameters is the “kind of simulation”. Three kinds are available but only the first two are automatic. • “Main”: With this parameter, DarkF will simulate the Virgo interferometer but only for the carrier. R&D Meeting

  5. “Main&SB”: This second kind will simulate the Virgo interferometer for the carrier and the sidebands. • “Free”: It is the expert mode! If you do not want to simulate the complete interferometer or if you want a specific result which is not given in the result file, you must choose this kind of simulation. So you must code your specific simulation in the case ”free” of the main program darkf.f90 . Remark: For the first two kinds of simulation, it is not necessary to compile the code. But for the case “Free”, a new compilation will be essential. So, a Makefile will be available with the program. R&D Meeting

  6. The simulation parameters We have three parameter files for DarkF: • paramfiles.in: This is the parameter file which defines the name of the other parameter files and of the result file. • paramsimu.in: This is the parameter file of the simulation (size of the sampling window, number of points of the window, power of the initial beams, waist, kind of simulation, modulation frequency, interferometer lengths,…). • paramirrors.in: This file contains all the mirror parameters (transmission, losses, tilt, rotation,…) and the name of the mirror maps. R&D Meeting

  7. Results given by an automatic simulation DarkF creates a result file where all the parameters are saved and where one finds the results of the simulation. These results include the power of the different beams, the losses, their couplings with perfect TEM modes, their barycenter and the contrast defect (before and after OMC). For example, if we want to characterize the long arms, we have: • Carrier reflectivity: • North arm: 98.85% & West arm: 99.02% • Carrier coupling with TEM00 (waist=2cm): • North arm: 99.36% & West arm: 99.21% • Losses during a round trip of the carrier: • North arm: 306ppm & West arm: 242ppm We can also see the shape of the different beams. R&D Meeting

  8. E0 Ecav Input Mirror End mirror z What can we simulate with DarkF? DarkF can simulate several systems (simple or double Fabry Perot cavities, Michelson interferometer, Virgo, …). The studies realized during the DarkF development are a good representation of the possibilities of this code. Simple Fabry Perot cavity: This system has been used for the characterization of the Virgo long arms, for the calculation of the curvature radius of the Virgo end mirrors and for the characterization of the gain limitations in the recycling cavity. R&D Meeting

  9. Characterization of the long arms and calculation of the end mirror curvature radii: (see the Virgo note “Optical Simulation, Mirror Curvatures and Long Arms”) • Calculation of the curvature of the end mirror (with parabolic fit of the wavefront) • Spacing between 00 and 01 mode resonances give by a formula: fm(north arm)=6.264422MHz fm(west arm)=6.263978MHz δfm = 31Hz Rc(NEM) ~ 3583m Rc(WEM) ~ 3621m R&D Meeting

  10. Flat-flat cavities: (first study of the sideband gain) The residual radii of curvature has a effect on the recycling gain but probably we can adjust the incoming beam parameters to correct it. R&D Meeting

  11. E0 Erec Ecav y z x Old Recycling Mirror z=-Lrec Input Mirror z=0 End Mirror z=2999.9 z Double Fabry-Perot cavity We search for this configuration (without mirror maps) the recycling length which maximizes the recycling gain for the sidebands. We use for the long arm the north arm parameters Lower sideband : Lrec=12.068 m  G=49.02 Upper sideband : Lrec=12.077 m  G=48.24 We take the mean value : Lrec=12.073 m R&D Meeting

  12. WE 2999.9m WI 5.634m L(PR-BS) 6.512m 2999.9m BS PR NI NE Virgo simulation: Two examples give the possibilities of DarkF for the Virgo simulation. Tuning of the recycling length (with all the mirror maps): We use the Virgo modulation frequency: 6.264219MHz R&D Meeting

  13. As precedent we search the recycling length which maximize the gain for the sidebands. With the old recycling mirror: Lower sideband: Lrec=12.081m  G=34.29 Upper sideband: Lrec=12.043m  G=33.24 Half sum: Lrec=12.064m  G=33.44 Virgo value: Lrec=12.073m R&D Meeting

  14. With the new recycling mirror: Lower sideband: Lrec=12.055m  G=43.73 Upper sideband: Lrec=12.120m  G=39.19 Half sum: Lrec=12.085m  G=39.30 Virgo value: Lrec=12.053m If we use the map of the new recycling mirror but with the parameters of the old, the values of Lrec are not modified The optimal recycling length is depending of the mirror shape. R&D Meeting

  15. Study of the sideband behaviors if we misalign Virgo (without the mirror maps): DarkF + phase camera  actualmisalignments status R&D Meeting

  16. Flat modes: Mode 00 (w0=2cm; rd=10cm; z=0) : But it is important to remark that all preceding examples (except sideband behaviors) can be done only in the mode expert. And to use this mode, you must know the code (approximately 5400 lines with the comments) and its documentation. R&D Meeting

  17. To be done • Install DarkF on a computer of Cascina: • Problem with the free fortran90 compiler • See the FFT library of the constructor • Finish the comparison of the results with the NV code of Vincent Loriette (ESPCI-Paris). During DarkF development, these comparisons have permitted to debug both codes, in particular for the map orientations (see the Virgo Software Technical Documentation “Map inversions for the Virgo optical simulations’) • Use DarkF to simulate the interferometers with flat modes (Losses, effect of the mirror shape, misalignments,…). Only DarkF in expert mode can do these simulations but for Virgo, there is nobody to do them. • Put the documentation in free access • Do a DarkF demonstration R&D Meeting

  18. Conclusion DarkF is an optical simulation code which allows to simulate several systems. And for each system we can change easily the mirrors parameters. DarkF and NV codes have not exactly the same properties. For the simulations with some centered defaults at long correlation length and for the present configuration of Virgo, NV will be adapted and we could appreciate its computing time speed. On the other hand, DarkF will be adapted to the simulations with defaults at short correlation length (but more than the sampling step) and to the R&D. R&D Meeting

  19. The parameter files paramfiles.in: paramsimu.in !name of the file containing the simulation parameters paramirrors.in !name of the file containing the mirror parameters results.out !name of the result file IMPORTANT : You can not change the name of this file! paramsimu.in: %% Sampling Window and convergence precision %% 0.5 !size of the window 64 !N ; grid dimension = N*N 1.e-9 !eps_cav ; accuracy of the cavity convergence 1.e-9 !eps-rec ; accuracy of the recycling convergence R&D Meeting

  20. %% Initial beam parameters %% 0.02 !beam width 0. !beam position (waist=0.) 1. !initial carrier power 1. !initial sidebands power 0 !order m of the TEM(m,n) 0 !order n of the TEM(m,n) 0. !tilt teta in radians (positive and small) 0. !tilt rotation phi in radians 0. !horizontal offset in x 0. !vertical offset in y 1.064e-6 !wavelength %% Modulation frequency %% 6264219. !fm %% Interferometer length %% 2999.9 !North arm length 2999.9 !West arm length 6. !PR-BS length 6.512 !BS-NI length 5.634 !BS-WI length R&D Meeting

  21. %% Output Mode cleaner %% 12. !length between BS and OMC 0.02 !width of the perfect TEM00 at its waist 0. !tilt teta in radians (positive and small) 0. !tilt rotation phi in radians 0. !horizontal translation in x 0. !vertical translation in y %% What kind of simulation? %% %%Virgo Main field = Main %% %%Virgo Main field + Sidebands = Main&SB %% %%Free simulation = Free %% Main&SB %% What kind of FFT? %% %%fft2d = use function fft2d in propag.f90 %% %%zfft_2d = use the library dxml or dxmlp %% %%fftw = use the library fftw3 fftw R&D Meeting

  22. paramirrors.in: %% Mirrors parameters %% --North End-- 4.67e-6 !HR coating losses 42.9e-6 !Transmission (T+R+P=1) 3583.126 !Curvature Radius 0. !tilt teta in radians (positive and small) 0 !tilt rotation phi in radians 0 !Horizontal translation x 0. !Vertical translation y Cmir12.map !Filename of the HR coating map 0.15785 !Radius of the mirror (0.15785m) 0 !mirror rotation ("0"(arrow below) or "pi" (arrow on the top)) --West End— The same thing --North Input— The same list of parameters except for the losses and for the maps) 0.9e-6 !AR coating losses Tmir11.map !Filename of the transmission map R&D Meeting

  23. --West Input— The same thing as for North Input except the last parameter 0 !mirror rotation ("0"(arrow on the top) or "pi" (arrow below)) --Recycling— We have the same parameter as West Input but without the losses for the antireflective coating. --Beam Splitter-- 6.85e-6 !HR coating losses 519.e-6 !AR coating losses 0.5025 !HR coating Reflection nomap !Filename of the HR coating map nomap !Filename of the transmission map (north arm) nomap !Filename of the transmission map (west arm) 0.1015 !Radius of the mirror (0.1015m) 0 !mirror rotation ("0"(arrow on the top) or "pi" (arrow below)) R&D Meeting

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