python光学仿真相速度和群速度计算理解学习

import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3D import Axes3D
z = np.arange(15,200)*10    #单位为nm
x = np.arange(15,200)*10
x,z = np.meshgrid(x,z)      #创建坐标系
E = 1/np.sqrt(x**2+z**2)*np.cos(2*np.pi*np.sqrt(x**2+z**2)/(532*1e-9))
fig = plt.figure()
ax = Axes3D(fig)
ax.plot_surface(x,z,E)
plt.show()

def wavePacket(d = [532e-9,600e-9]):
    d = np.array(d)
    k = 2*np.pi/d           #波数
    dk = k[0]-k[1]          #波数差
    bk = k[1]+dk/2          #平均波数
    z = np.arange(10000)/1e9  #位置为0到10um
    E0 = np.cos(-k[0]*z)
    E1 = np.cos(-k[1]*z)
    E = E0+E1
    #E = 2*np.cos(-dk/2*z)*np.cos(-bk*z)
    fig = plt.figure()
    plt.plot(z,E0,'--',color='red',label='E0')
    plt.plot(z,E1,'--',color='blue',label='E1')
    plt.plot(z,E,'-',color='green',label='E')
    plt.legend()
    plt.show()