60 lines
1.6 KiB
Python
60 lines
1.6 KiB
Python
# These calculations are based on Ashkin's article "Forces of a single-beam
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# gradient laser trap on a dielectric sphere in the ray optics regime".
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# There are axial forces only
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import numpy as np
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import matplotlib.pyplot as plt
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import seaborn as sns
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from functions import *
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from scipy import integrate
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sns.set()
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# Intensity profile graphics
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rho = np.linspace(-r_max, r_max, 500)
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plt.figure(1, figsize=(10, 6))
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I = gauss(rho)
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I0 = np.max(I)
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plt.plot(rho, I / I0)
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plt.fill_between(rho, I / I0, 0, alpha=0.3)
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plt.title("Forces along Y axis")
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plt.xlabel('$r, m$', fontsize=18)
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plt.ylabel('$I(r)$', fontsize=18)
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# Integration
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def q_res_g(z, func):
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ans = integrate.quad(lambda dr: dr * func(dr) * q_g_z(dr, z) * (~np.iscomplex(q_g_z(dr, z))).astype(float),
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0, r_max, epsabs=1e-12, epsrel=1e-6)
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return 2 * np.pi * ans[0] / (np.pi * w0 ** 2)
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def q_res_s(z, func):
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ans = integrate.quad(lambda dr: dr * func(dr) * q_s_z(dr, z) * (~np.iscomplex(q_s_z(dr, z))).astype(float),
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0, r_max, epsabs=1e-12, epsrel=1e-6)
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return 2 * np.pi * ans[0] / (np.pi * w0 ** 2)
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# Calculation
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n = 200
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z = np.linspace(-2 * Rsp, 2 * Rsp, n)
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axial_g = [q_res_g(dz, gauss) for dz in z]
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axial_s = [q_res_s(dz, gauss) for dz in z]
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axial_g = F0 * np.array(axial_g[::-1])
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axial_s = F0 * np.array(axial_s[::-1])
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axial = axial_g + axial_s
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z = -z[::-1]
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# Graphics
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plt.figure(2, figsize=(10, 6))
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plt.plot(z, axial_g, '-.', lw=1, label='$F_{g}$')
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plt.plot(z, axial_s, '--', lw=1, label='$F_{s}$')
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plt.plot(z, axial, lw=1, label='$F_{t}$')
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plt.xlabel('$r, m$', fontsize=18)
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plt.ylabel('$F, N$', fontsize=18)
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plt.legend(fontsize=18)
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plt.show()
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