This page and the linked pdf explain it rather well. I've implemented it in python where the inputs are lorentz-drude model params and the output is MEEPs (lorentz) model.
#Author: Majid al-Dosari #code that takes in lorentz-drude model parameters and converts them to code #usable by meep. just use eVLD2meepcode #example: eVLD2meepcode('mysilver',100e-9,9,[[.845,.048,0],[.065,3.886,.816]]) #output: #(define mysilver (make dielectric (epsilon 1) #(polarizations #(make polarizability #( omega 8.06554724676e-22 ) ( gamma 0.00387146267844 ) ( sigma 6.8445e+41 )) #( omega 0.0658148655336 ) ( gamma 0.313427166009 ) ( sigma 7.9071150519 )) #))) #it's an implementation of #http://juluribk.com/2011/04/27/plasmonic-materials-in-meep/ by Bala Krishna Juluri #normalization length a #w omega #p plasma #G Gamma def sip(stuff):#stuff in parens return '( ' +str(stuff)+ ' )' def wordandvalue(word,value): return sip(word+' '+str(value)) def meepfactor(a): return 2*3.14159265359*299792458/a #2pi*c/a def eV2w(eV):return eV*(2*3.14159265359)/4.135666e-15 def eV2meep(a,eV):return eV2w(eV)/meepfactor(a) def sigmaa(f,wp,w): """f is oscillator strength, wp is plamsa freq""" return (f*wp**2)/w**2 def eVLD2meepL(a,wp,fGw0_list): oGs_list=[] smallno=1e-20; for f,G,w0 in fGw0_list: if w0==0:w0=smallno #hack oGs_list.append([eV2meep(a,w0) ,eV2meep(a,G) ,sigmaa(f,eV2meep(a,wp),eV2meep(a,w0))]) return oGs_list def eVLD2meepcode(name,a,wp,fGw0_list): """ input: name: for code a: meep normalization const wp: plasma freq in eV fGw0_list: nested list of f oscillator strengths Gamma relaxation in eV omega0 in eV,w=0 is handled by converting it to a very small no. """ return writelorentz(name,oGs_list=eVLD2meepL(a,wp,fGw0_list)) def writelorentz(name,oGs_list=None,epsilon=1):#meep is in lorentz txt='' txt+='(define '+str(name)+' (make dielectric (epsilon '+str(epsilon)+') \n' if oGs_list==None or len(oGs_list)==0: txt+='))' return txt txt+='(polarizations \n' for omega,Gamma,sigma in oGs_list: txt+='(make polarizability \n' txt+=wordandvalue('omega',omega)+' ' txt+=wordandvalue('gamma',Gamma)+' ' txt+=wordandvalue('sigma',sigma)+')\n' txt+=')))' return txt #so 1. normalize then 2. cast into meep
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