Tuesday, February 7, 2012

Task 1: Understanding MEEP's dispersive media

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]])
#(define mysilver (make dielectric (epsilon 1) 
#(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):
    for f,G,w0 in fGw0_list:
        if w0==0:w0=smallno #hack
    return oGs_list

def eVLD2meepcode(name,a,wp,fGw0_list):
        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+='(define '+str(name)+' (make dielectric (epsilon '+str(epsilon)+') \n'
    if oGs_list==None or len(oGs_list)==0:
        return txt
    txt+='(polarizations \n'
    for omega,Gamma,sigma in oGs_list:        
        txt+='(make polarizability \n'
        txt+=wordandvalue('omega',omega)+' '
        txt+=wordandvalue('gamma',Gamma)+' '
    return txt

#so 1. normalize then 2. cast into meep

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