/* * WMM-Application: * MMI coupler, 1x2/2x1 power splitter/combiner */ /* * WMM * Wave-matching method for mode analysis of dielectric waveguides * Manfred Lohmeyer * University of Osnabrueck, Department of Physics * Barbarastrasse 7, D-49069 Osnabrueck, Germany * (1999) */ #include #include #include #include"wmminc.h" /* waveguide parameters */ #define Wgpns 1.95 // substrate refractive index #define Wgpnf 2.2 // film refractive index #define Wgpnc 1.0 // cover: air #define Wgpw 1.3 // input waveguide width #define WgpW 4.45 // width of the multimode segment #define Wgph 0.7 // strip height #define Wgpl 1.3 // vacuum wavelength #define WgpS 1.05 // off-center position of port waveguides #define WgpL 32.3 // length of the MMI segment /* waveguide definition: a single strip of width w */ Waveguide wgdef(double w) { Waveguide g(1, 1); g.hx(0) = 0.0; g.hx(1) = Wgph; g.hy(0) = -w/2.0; g.hy(1) = w/2.0; g.n(0,0) = Wgpns; g.n(0,1) = Wgpns; g.n(0,2) = Wgpns; g.n(1,0) = Wgpnc; g.n(1,1) = Wgpnf; g.n(1,2) = Wgpnc; g.n(2,0) = Wgpnc; g.n(2,1) = Wgpnc; g.n(2,2) = Wgpnc; g.lambda = Wgpl; return g; } /* two output ports */ Waveguide wg2def() { Waveguide g(1, 3); g.hx(0) = 0.0; g.hx(1) = Wgph; g.hy(0) = -Wgpw/2.0-WgpS; g.hy(1) = Wgpw/2.0-WgpS; g.hy(2) = -Wgpw/2.0+WgpS; g.hy(3) = Wgpw/2.0+WgpS; g.n(0,0) = Wgpns; g.n(0,1) = Wgpns; g.n(0,2) = Wgpns; g.n(0,3) = Wgpns; g.n(0,4) = Wgpns; g.n(1,0) = Wgpnc; g.n(1,1) = Wgpnf; g.n(1,2) = Wgpnc; g.n(1,3) = Wgpnf; g.n(1,4) = Wgpnc; g.n(2,0) = Wgpnc; g.n(2,1) = Wgpnc; g.n(2,2) = Wgpnc; g.n(2,3) = Wgpnc; g.n(2,4) = Wgpnc; g.lambda = Wgpl; return g; } /* WMM analysis parameters */ WMM_Parameters pardef() { WMM_Parameters p; p.vform = HXHY; p.vnorm = NRMMH; p.ccomp = CCALL; p.ini_d_alpha = 0.01; p.ini_N_alpha = 15; p.ini_alpha_max = 2.0; p.ini_steps = 50; p.ref_num = 5; p.ref_exp = 4.0; p.ref_sdf = 0.5; p.fin_d_alpha = 0.01; p.fin_N_alpha = 30; p.fin_alpha_max = 3.0; p.btol = 1.0e-7; p.mshift = 1.0e-10; return p; } /* calculate QTE modes, save modes, write mode profile data, write interference data */ int main() { WMM_Parameters par = pardef(); WMM_ModeArray mmis; WMM_ModeArray mmia; WMM_ModeArray mmi; WMM_Mode m; WMM_Mode t; Waveguide wg; int i; // the input/output waveguide wg = wgdef(Wgpw); // calculate the input/output mode WMM_findfundmode(wg, QTE, SYM, 1.95, 2.11, par, '-', '-', mmi); // ... and save it m = mmi(0); m.write_def('-', '-'); mmi.clear(); // the multimode segment wg = wgdef(WgpW); // find all its symmetrical modes WMM_modeanalysis(wg, QTE, SYM, 1.95, 2.11, par, '-', '-', mmis); // and save to files mmis.write_def('s', '-'); // find all its antriysymmetrical modes WMM_modeanalysis(wg, QTE, ASY, 1.95, 2.11, par, '-', '-', mmia); // and save to files mmia.write_def('a', '-'); // second run should start here ... // m.read_def(QTE, SYM, '-', '-'); // mmis.read_def('s', '-'); // mmia.read_def('a', '-'); // display window Rect display(-Wgph, -(WgpW/2.0+1.0), Wgph*1.5, WgpW/2.0+1.0); // Mlop_Print=YES; // Mlop_Colour=NO; // write mode profiles, surface and contour plots m.mfile(EY, ORG, display, 75, 155, '0', 'i', 'S'); m.mfile(EY, SQR, display, 75, 155, '0', 'i', 'C'); for(i=0; i<=mmis.num-1; ++i) { mmis(i).mfile(EY,ORG,display,75,155,dig10(i),dig1(i),'S'); mmis(i).mfile(EY,SQR,display,75,155,dig10(i),dig1(i),'C'); } for(i=0; i<=mmia.num-1; ++i) { mmia(i).mfile(EY,ORG,display,75,155,dig10(i),dig1(i),'S'); mmia(i).mfile(EY,SQR,display,75,155,dig10(i),dig1(i),'C'); } // no perturbation Cvector p(mmis.num+mmia.num); p.init(CC0); // first we need only symmetrical modes mmi = mmis; // initial mode amplitudes: centered input waveguide Cvector a(mmi.num); for(i=0; i<=mmi.num-1; ++i) { t = mmi(i); a(i) = Complex(lscalprod(t, m), 0.0); } // --> the initial intensity distribution mmi.mfile(a, p, 0.0, SZ, ORG, display, 75, 155, '0', 's', 'C'); // propagation along one focusing length mmi.prop(a, p, Wgph/2.0, display.y0, display.y1, 115, 0.0, WgpL, 250, 'p', '0'); // interference animation // mmi.movie(a, p, EY, MOD, display, 75, 155, 'I', 32, 0.0, WgpL); // mmi.movie(a, p, SZ, ORG, display, 75, 155, 'F', 32, 0.0, WgpL); // to determine a proper device length: // power transfer versus length of the MMI segment // centered input port -> centered output port mmi.writeiopower(m, m, p, 1000, 0.0, 100.0, '0', '0'); // to determine the off-center port position: // transverse intensity contours at half the focusing length mmi.mfile(a, p, WgpL/2.0, SZ, ORG, display, 75, 155, '1', 's', 'C'); // interference: top views, port waveguides included // one complete focus length, single centered input/output ports mmi.ioprop(m, m, p, Wgph/2.0, WgpL, display.y0, display.y1, 115, -2.0, WgpL+2.0, 250, '0', '0'); // power splitter WMM_ModeArray omode; omode.add(m); omode.add(m); omode(0).translate(0.0, -WgpS); omode(1).translate(0.0, WgpS); Waveguide owg=wg2def(); mmi.ioprop(m, omode, owg, p, Wgph/2.0, WgpL/2.0, display.y0, display.y1, 115, -2.0, WgpL/2.0+2.0, 250, 's', '0'); omode.clear(); // power combiner // equal imput amplitudes, constructive interference WMM_ModeArray imode; imode.add(m); imode.add(m); imode(0).translate(0.0, -WgpS); imode(1).translate(0.0, WgpS); Waveguide iwg=wg2def(); Cvector iamp(2); iamp(0) = CC1; iamp(1) = CC1; omode.add(m); mmi.ioprop(iamp, imode, iwg, omode, m.wg, p, Wgph/2.0, WgpL/2.0, display.y0, display.y1, 115, -2.0, WgpL/2.0+2.0, 250, 'c', '0'); // 180^o phase difference of the input modes, destructive interference // now the antisymmetrical modes are required as well mmi.merge(mmia); mmi.sort(); iamp(0) = CC1; iamp(1) = -CC1; mmi.ioprop(iamp, imode, iwg, omode, m.wg, p, Wgph/2.0, WgpL/2.0, display.y0, display.y1, 115, -2.0, WgpL/2.0+2.0, 250, 'd', '0'); // only one of the input channels of the power combiner is excited: // about half of the input power passes the device iamp(0) = CC1; iamp(1) = CC0; mmi.ioprop(iamp, imode, iwg, omode, m.wg, p, Wgph/2.0, WgpL/2.0, display.y0, display.y1, 115, -2.0, WgpL/2.0+2.0, 250, 'a', '0'); return 0; }