There is a significant difference in the results obtained by reusing a certain piece of code and using it alone

[niubiworker]

As mentioned in the question, I cycled through the code and only changed the value of a by using for, but the results I obtained were significantly different from those obtained by running a single value of a, such as 0.8. Why is this? Who can help me, thank you!

import numpy as np
import meep as mp
import matplotlib.pyplot as plt


def lno(a):
    b = 1+2.6734*a**2/(a**2-0.01764)+1.2290*a**2/(a**2-0.0591)+12.614*a**2/(a**2-474.60)
    return b
def lne(a):
    b = 1+2.9804*a**2/(a**2-0.02047)+0.5981*a**2/(a**2-0.0666)+8.9543*a**2/(a**2-416.08)
    return b
def geo_phc(wl):
    geo_phc = [mp.Block(size=mp.Vector3(Block_x,Block_y,Block_z),
                         center=mp.Vector3(block_x,block_y,block_z),
                         material=mp.Medium(epsilon_diag=(lno(wl),lne(wl),lno(wl))))]
    geo_phc += [mp.Block(size=mp.Vector3(x_length,y_length,z_length),
                          center=mp.Vector3(block_x1,0,0),
                          material=mp.Medium(epsilon_diag=(lno(wl),lne(wl),lno(wl)))),
                mp.Block(size=mp.Vector3(x_length,y_length,z_length),
                          center=mp.Vector3(block_x2,0,0),
                          material=mp.Medium(epsilon_diag=(lno(wl),lne(wl),lno(wl))))]
    for i in np.linspace(-x_num*0.5*a,x_num*0.5*a,70+1):
        for j in np.linspace(-y_num*np.sqrt(3)*a,y_num*np.sqrt(3)*a,2*y_num+1):
            if j != 0:
                geo_phc += [add_cylinder(mp.Vector3(i+0.5*a,j,0)),
                            add_cylinder(mp.Vector3(i,j+np.sqrt(3)*0.5*a,0))]
            else:
                geo_phc += [add_cylinder(mp.Vector3(i,np.sqrt(3)*0.5*a,0))]
    return geo_phc
def geo_str(wl):
    geo_str = [mp.Block(size=mp.Vector3(sim_x,y_length,z_length),
                         center=mp.Vector3(0),
                         material=mp.Medium(epsilon_diag=(lno(wl),lne(wl),lno(wl))))]
    return geo_str
def add_cylinder(local):
    a = mp.Cylinder(radius=r,height=h,center=local,material=mp.air)
    return a


array_list=[]
num_1 = 11
for i in np.linspace(0.7,0.8,num_1):
    a = float('%.2f'%i)
 #   m = i
    r,h, = 0.315*a,0.3
    x_num,y_num = 60,6
    period_num = 50
    resolution= 10
    courant=0.5
    pml=1
    wg_wight = y_num*np.sqrt(3)*a*2

    wavel_min,wavel_max,nfreq=1.3,2.3,100
    frq_min,frq_max=1/wavel_max,1/wavel_min
    fcen = 0.5*(frq_max+frq_min)
    df = (frq_max-frq_min)
    

    LN = mp.Medium(epsilon_diag=(lno(1/fcen),lne(1/fcen),lno(1/fcen)))

#板参数
    block_x,block_y,block_z=0,0,0
    Block_x,Block_y,Block_z=x_num*a,wg_wight,h

#导光板左与右
    x_length = 6 #板长度
    y_length = np.sqrt(3)*a
    z_length = h
    block_x1= -x_num*0.5*a-x_length*0.5#右边板位置
    block_x2= -block_x1

#源范围、类型与位置
    soc_wight,soc_hight=np.sqrt(3)*a*2,3*h
    soc_area=mp.Vector3(0,soc_wight,soc_hight)
    soc_local=mp.Vector3(-0.5*a*x_num-x_length*0.9,0,0)
    eig_sources = [mp.EigenModeSource(
        src=mp.GaussianSource(fcen,fwidth=df),
        center=soc_local,
        direction=mp.AUTOMATIC,
        size=soc_area,
        eig_band=1,
        eig_kpoint=mp.Vector3(1,0,0),
        eig_parity=mp.EVEN_Z+mp.ODD_Y,
        eig_match_freq=True,
    )]

#监视器的位置和大小
    monitor_size=soc_area+soc_area
    monitor_1_local=mp.Vector3(x=-period_num*0.5*a)
    monitor_2_local=mp.Vector3(x=period_num*a*0.5)
    monitor_3_local=mp.Vector3(x=a)+soc_local#stright refl
    monitor_4_local=mp.Vector3(x=a)+monitor_1_local#phc_wg refl
    monitor_5_local=mp.Vector3(x=y_num*a*np.sqrt(3)*0.5-0.1*a)#stright tran

#模拟区域
    sim_x,sim_y,sim_z=x_num*a+2*x_length+pml*2,y_num*a*np.sqrt(3)+pml*2,10*h+pml*2
    simulation_area=mp.Vector3(sim_x,sim_y,sim_z)


###################



    sim = mp.Simulation(cell_size=simulation_area,
                    resolution=resolution,
                    boundary_layers=[mp.PML(pml)],
                    sources=eig_sources,
                    geometry=geo_str(1/fcen),
                    symmetries=[mp.Mirror(mp.Z,phase=1)])
    refl_str=sim.add_flux(fcen,df,nfreq,
                  mp.FluxRegion(center=monitor_3_local,direction=mp.X,size=monitor_size))
    tran_str=sim.add_flux(fcen,df,nfreq,
                   mp.FluxRegion(center=monitor_5_local,direction=mp.X,size=monitor_size))

    pt=monitor_5_local-mp.Vector3(x=0.5*a)
    sim.run(until_after_sources=mp.stop_when_fields_decayed(50,mp.Ey,pt,1e-6))
    str_tran_flux = mp.get_fluxes(tran_str)
    str_refl_data=sim.get_flux_data(refl_str)

##################################
    sim.reset_meep()

    sim = mp.Simulation(cell_size=simulation_area,
                    resolution=resolution,
                    boundary_layers=[mp.PML(pml)],
                    sources=eig_sources,
                    geometry=geo_phc(1/fcen),
                    symmetries=[mp.Mirror(mp.Z,phase=1)])
    refl_phc=sim.add_flux(fcen,df,nfreq,
                  mp.FluxRegion(center=monitor_3_local,direction=mp.X,size=monitor_size))
    tran_phc_1=sim.add_flux(fcen,df,nfreq,
                  mp.FluxRegion(center=monitor_1_local,direction=mp.X,size=monitor_size))
    tran_phc_2=sim.add_flux(fcen,df,nfreq,
                   mp.FluxRegion(center=monitor_2_local,direction=mp.X,size=monitor_size))
    sim.load_minus_flux_data(refl_phc,str_refl_data)
    pt=monitor_2_local-mp.Vector3(x=0.5*a)
    sim.run(until_after_sources=mp.stop_when_fields_decayed(50,mp.Ey,pt,1e-6))
    phc_tran_flux_1=mp.get_fluxes(tran_phc_1)
    phc_tran_flux_2=mp.get_fluxes(tran_phc_2)
    flux_freq=mp.get_flux_freqs(refl_phc)

    wl = []
    Ts_1 = []
    Ts_2 = []
    Ts_3 = []
    for j in range(nfreq):
        wl = np.append(wl,1/flux_freq[j])
        Ts_1 = np.append(Ts_1,phc_tran_flux_1[j]/str_tran_flux[j])
        Ts_2 = np.append(Ts_2,phc_tran_flux_2[j]/str_tran_flux[j])
        Ts_3 = np.append(Ts_3,phc_tran_flux_2[j]/phc_tran_flux_1[j])
    np.savetxt(f"Ts_{i}.txt",Ts_3,fmt='%f',delimiter=',')
    array_list.append(Ts_3)
 
 
 
 #   np.savetxt('Ts_1.txt',Ts_1,fmt='%f',delimiter=',')
  #  np.savetxt('Ts_2.txt',Ts_2,fmt='%f',delimiter=',')
for m in range(num_1):
    plt.grid(True)
    wl_1=np.linspace(1.3,2.3,100)
#plt.plot(wl, Ts_1, "bo-", label="reflectance")
#plt.plot(wl, Ts_2, "ro-", label="transmittance")

    plt.plot(wl_1,np.array(array_list)[m,:], label=f"transmittance_{'%.2f'%np.linspace(0.7,0.8,num_1)[m]}") 
    plt.xlim(min(wl),max(wl))
    plt.xlabel("wavelength (μm)")
    plt.legend(loc="upper right")
plt.savefig("T_R_loss.png")
plt.show()

[zekishaw]

Try a sim.reset_meep() at the end of your second simulation run?

In the loop after the second simulation from what I can see you will have fields, etc. Saved from previous computation. [Someone will correct me if I'm wrong, but it looks similar to an issue I was facing alsoz and resetting the sim fixed it]