I have tried to plot the wavefront of a Laguerre-Gaussian beam, I know that to do that I have to plot the set of all points where the wave has the same phase.

I have try to use the conditional If to do it but the program just don't do it
LG[r_, ϕ_, p_, l_,
w_] := (Sqrt[(2 p!)/(π (p + Abs[l])!)] 1/
w E^(-r^2/w^2) ((r Sqrt[2])/w)^Abs[l] LaguerreL[p, Abs[l],
2 r^2/w^2] E^(I l ϕ))
Module[{l = 1, p = 0, xMax = 3, zMax}, zMax = 2 Pi ;
DensityPlot3D[If[Cos[I( l ϕ -I z)==0,
Re[LG[Sqrt[x^2 + y^2], ArcTan[x, y], p, l, 1] Exp[-I z]]], {x, -xMax,
xMax}, {y, -xMax, xMax}, {z, 0, zMax}, PlotPoints -> 60,
AxesLabel -> {"x", "y", "z"}]]
I would like to obtain something like
Ref: https://en.wikipedia.org/wiki/Orbital_angular_momentum_of_light

