|
| 1 | +from numpy import * |
| 2 | +from pylab import * |
| 3 | +import timeit |
| 4 | + |
| 5 | + |
| 6 | +class DBRMirror: |
| 7 | + def __init__(self, ni, nbr): # ni - refractive indices as array, nbr - number of layers (must be even!) |
| 8 | + if nbr % 2 != 0: print("Number must be even! Program will give wrong results") |
| 9 | + self.nbr = nbr |
| 10 | + self.n = array(concatenate(([1], tile(ni, (self.nbr-2)//2), [ni[0]]))) |
| 11 | + |
| 12 | + def reflection_coeff(self, incidentwavelength, braggwavelength): |
| 13 | + nm = (self.n[:-1] / self.n[1:]) |
| 14 | + R = array([]) |
| 15 | + for value in braggwavelength: |
| 16 | + d = array(concatenate(([0], 0.25 * value/self.n[1:-1], [0]))) |
| 17 | + phi = 2j*pi*self.n[:-1]*d[:-1]/incidentwavelength |
| 18 | + transition_matrix = array([[0.5*(1+nm)*exp(-phi), 0.5*(1-nm)*exp(phi)], |
| 19 | + [0.5*(1-nm)*exp(-phi), 0.5*(1+nm)*exp(phi)]]) |
| 20 | + |
| 21 | + general_transition_matrix = 1 |
| 22 | + for k in range(self.nbr - 2,-1,-1): |
| 23 | + general_transition_matrix = dot(general_transition_matrix, transition_matrix[:, :, k]) |
| 24 | + |
| 25 | + # print(general_transition_matrix) |
| 26 | + r = - general_transition_matrix.item(2) / general_transition_matrix.item(3) |
| 27 | + R = append(R, abs(r)**2) |
| 28 | + |
| 29 | + # t = linalg.det(general_transition_matrix) / general_transition_matrix.item(3) |
| 30 | + # T = n.item(N-1)/n.item(0) * abs(t)**2 |
| 31 | + # |
| 32 | + # print(R) |
| 33 | + # print(T) |
| 34 | + # print(R+T) |
| 35 | + return R |
| 36 | + |
| 37 | + |
| 38 | +start = timeit.default_timer() |
| 39 | +wave_length = 0.98 * 10 ** (-6) |
| 40 | +NewMirror = DBRMirror([3.0, 3.5], 42) |
| 41 | +braggwavelength = array(linspace(0.68,1.28,100000)*10**(-6)) |
| 42 | +R = NewMirror.reflection_coeff(wave_length,braggwavelength) |
| 43 | + |
| 44 | +stop = timeit.default_timer() |
| 45 | +print(stop - start) |
| 46 | + |
| 47 | +plot(braggwavelength, R) |
| 48 | +xlabel("$\lambda$") |
| 49 | +ylabel("R") |
| 50 | +show() |
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