gaussian_beams.py 8.94 KB
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import pykat.exceptions as pkex
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import numpy as np
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import math
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import copy
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import warnings
import cmath
from scipy.special import hermite
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from pykat.SIfloat import SIfloat
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class gauss_param(object):
    """
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    Use beam_param instead, will be future name of this object.
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    Gaussian beam complex parameter
    
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    beam_param is effectively a complex number with extra
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    functionality to determine beam parameters.
    
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    Defaults to 1064e-9m for wavelength and refractive index 1
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    usage:
        q = gauss_param(w0=w0, z=z)
        q = gauss_param(z=z, zr=zr)
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        q = gauss_param(w=w, rc=rc)
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        q = gauss_param(q=a) # where a is a complex number
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        or change default wavelength and refractive index with:
        
        q = gauss_param(wavelength, nr, w0=w0, zr=zr)
    """
    
    def __init__(self, wavelength=1064e-9, nr=1, *args, **kwargs):
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        if self.__class__ != beam_param:
            warnings.warn("Name changed. Use beam_param instead of gauss_param.")
            
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        self.__q = None
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        self.__lambda = SIfloat(wavelength)
        self.__nr = SIfloat(nr)
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        if len(args) == 1:
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            self.__q = complex(args[0])
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        elif len(kwargs) == 1:
            if "q" in kwargs:
                self.__q = complex(kwargs["q"])        
            else:
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                raise pkex.BasePyKatException("Must specify: z and w0 or z and zr or rc and w or q, to define the beam parameter")
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        elif len(kwargs) == 2:        
            
            if "w0" in kwargs and "z" in kwargs:
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                q = SIfloat(kwargs["z"]) + 1j *float(math.pi*SIfloat(kwargs["w0"])**2/(self.__lambda/self.__nr) )
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            elif "z" in kwargs and "zr" in kwargs:
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                q = SIfloat(kwargs["z"]) + 1j *SIfloat(kwargs["zr"]) 
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            elif "rc" in kwargs and "w" in kwargs:
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                one_q = 1 / SIfloat(kwargs["rc"]) - 1j * self.__lamda / (math.pi * self.__nr * SIfloat(kwargs["w"])**2)
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                q = 1/one_q
            else:
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                raise pkex.BasePyKatException("Must specify: z and w0 or z and zr or rc and w or q, to define the beam parameter")
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            self.__q = q
        else:
            raise pkex.BasePyKatException("Incorrect usage for gauss_param constructor")
    
    @property
    def wavelength(self): return self.__lambda
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    @wavelength.setter
    def wavelength(self,value): self.__lambda = SIfloat(value)
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    @property
    def nr(self): return self.__nr
    
    @property
    def q(self): return self.__q
    
    @property
    def z(self): return self.__q.real
    
    @property
    def zr(self): return self.__q.imag
    
    @property
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    def w(self):
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        return abs(self.__q)*math.sqrt(self.__lambda / (self.__nr * math.pi * self.__q.imag))
        #return self.w0 * math.sqrt(1 + (self.__q.real/self.__q.imag)**2)
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    @property
    def w0(self):
        return math.sqrt(self.__q.imag * self.__lambda / (self.__nr * math.pi))    

    @property
    def Rc(self):
        if self.__q.real != 0:
            return abs(self.__q) / self.__q.real
        else:
            return float("inf")
    
    def conjugate(self):
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        return beam_param(self.__lambda, self.__nr, self.__q.conjugate())
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    def __complex__(self):
        return self.__q
    
    def __str__(self):
        return str(self.__q)
    
    def __mul__(self, a):
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        return beam_param(self.__lambda, self.__nr, self.__q * complex(a))
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    def __imul__(self, a):
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        self.__q *= complex(a)
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        return self
        
    __rmul__ = __mul__
    
    def __add__(self, a):
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        return beam_param(self.__lambda, self.__nr, self.__q + complex(a))
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    def __iadd__(self, a):
        self.__q += complex(a)
        return self
        
    __radd__ = __add__
    
    def __sub__(self, a):
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        return beam_param(self.__lambda, self.__nr, self.__q - complex(a))
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    def __isub__(self, a):
        self.__q -= complex(a)
        return self
        
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    def __rsub__(self, a):
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        return beam_param(self.__lambda, self.__nr, complex(a) - self.__q)
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    def __div__(self, a):
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        return beam_param(self.__lambda, self.__nr, self.__q / complex(a))
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    def __idiv__(self, a):
        self.__q /= complex(a)
        return self
    
    def __pow__(self, q):
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        return beam_param(self.__lambda, self.__nr, self.__q**q)
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    def __neg__(self, q):
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        return beam_param(self.__lambda, self.__nr, -self.__q)
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    def __eq__(self, q):
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        return complex(q) == self.__q
        
    @property
    def real(self): return self.__q.real
    @real.setter
    def real(self, value): self.__q.real = SIfloat(value)
    
    @property
    def imag(self): return self.__q.imag
    @imag.setter
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    def imag(self, value): self.__q.imag = SIfloat(value)
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    # reverse beam direction 
    def reverse(self):
        self.__q = -1.0 * self.__q.real + 1j * self.__q.imag
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class beam_param(gauss_param):
    pass

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class HG_beam(object):
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    def __init__(self, qx, qy=None, n=0, m=0):
        self._qx = copy.deepcopy(qx)
        self._2pi_qrt = math.pow(2.0/math.pi, 0.25)
        
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        if qy.__class__ == beam_param:
            self._qy = copy.deepcopy(qx)
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        else:
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            self._qy = copy.deepcopy(qy)
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        self._n = n
        self._m = m
        self._hn = hermite(n)
        self._hm = hermite(m)
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        self._calc_constants()
        
    @property
    def n(self): return self._n
    @n.setter
    def n(self,value): 
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        self._n = int(value)
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        self._calc_constants()
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        self._hn = hermite(self._n)
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    @property
    def m(self): return self._m
    @m.setter
    def m(self,value): 
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        self._m = int(value)
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        self._calc_constants()
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        self._hm = hermite(self._m)
            
    @property
    def q(self):
        if self._qx.q == self._qy.q:
            return self._qx.q
        else:
            return (self._qx.q, self._qy.q)
    @q.setter
    def q(self, value):
        if value.__class__ == beam_param:
            self._qx = copy.deepcopy(value)
            self._qy = copy.deepcopy(value)
        else:
            self._qx = beam_param(q=complex(value))
            self._qy = beam_param(q=complex(value))
    
    @property
    def qx(self):
        return self._qx.q
        
    @qx.setter
    def qx(self, value):
        if value.__class__ == beam_param:
            self._qx = copy.deepcopy(value)
        else:
            self._qx = beam_param(q=complex(value))
    
    @property
    def qy(self):
        return self._qy.q
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    @qy.setter
    def qy(self, value):
        if value.__class__ == beam_param:
            self._qy = copy.deepcopy(value)
        else:
            self._qy = beam_param(q=complex(value))
            
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    def _calc_constants(self):
        self.__xpre_const = math.pow(2.0/math.pi, 0.25)
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        self.__xpre_const *= math.sqrt(1.0/(2**self._n * math.factorial(self._n)))
        self.__xpre_const *= cmath.sqrt(1j*self._qx.imag / self._qx.q)
        self.__xpre_const *= ((1j*self._qx.imag * self._qx.q.conjugate())/(-1j*self._qx.imag * self._qx.q)) ** ( self._n/2.0)
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        self.__ypre_const = math.pow(2.0/math.pi, 0.25)
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        self.__ypre_const *= math.sqrt(1.0/(2**self._m * math.factorial(self._m)))
        self.__ypre_const *= cmath.sqrt(1j*self._qy.imag / self._qy.q)
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        self.__ypre_const *= ((1j*self._qy.imag * self._qy.q.conjugate())/(-1j*self._qy.imag * self._qy.q)) **(self._m/2.0)
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        self.__sqrt2_wxz = math.sqrt(2) / self._qx.w
        self.__sqrt2_wyz = math.sqrt(2) / self._qy.w
        
        self.__kx =  2*math.pi / self._qx.wavelength
        self.__ky =  2*math.pi / self._qy.wavelength
        
        self.__invqx = 1/ self._qx.q
        self.__invqy = 1/ self._qy.q
        
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    def Un(self, x):
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        return self.__xpre_const * self._hn(self.__sqrt2_wxz * x) * np.exp(-0.5j * self.__kx * x*x * self.__invqx)
    
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    def Um(self, y):
        return self.__ypre_const * self._hm(self.__sqrt2_wyz * y) * np.exp(-0.5j * self.__ky * y*y * self.__invqy)
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    def Unm(self, x, y):  
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        return self.Un(x) * self.Um(y)
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    def plot(self, ndx=100, ndy=100, xscale=4, yscale=4):
        import pylab
        
        xrange = xscale * np.linspace(-self._qx.w, self._qx.w, ndx)
        yrange = yscale * np.linspace(-self._qy.w, self._qy.w, ndy)

        dx = xrange[1]-xrange[0]
        dy = yrange[1]-yrange[0]

        xx, yy = np.meshgrid(xrange,yrange)

        data = self.Unm(xx, yy)

        fig = pylab.figure()
        axes = pylab.imshow(np.abs(data), aspect=dx/dy, extent=[min(xrange),max(xrange),min(yrange),max(yrange)])
        pylab.xlabel('x [m]')
        pylab.ylabel('y [m]')
        cbar = fig.colorbar(axes)
        pylab.show()
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