Hanbury Brown–Twiss-type experiments with optical vortices and observation of modulated intensity correlation on scattering from rotating ground glass

The famous Hanbury Brown and Twiss type experiments are performed with optical vortices. Though the intensity correlation for vortices are found to be similar to that of the TEM${}_{00}$ mode of the He-Ne laser used to generate the vortices, an interesting difference is observed when they are scattered through a rotating ground glass plate. For smaller time delays, correlations for vortices follow the same pattern as the scattered Gaussian beam of light except that the vortices decay faster and the rate of decay depends on the order of the vortex. For longer time delays, however, the intensity correlation curves for vortices are found to be modulated and this modulation becomes more prominent as the order of the vortex is increased. This seemingly counterintuitive observation is supported by exact analytical results.

Figure 1

Setup for the generation of optical vortices through the spatial light modulator and study the intensity correlation function of these vortices scattered through the RGG plate (details are given in the text).

Figure 2

Schematic of the scattering geometry of the RGG plate; (a) the laser spot (shown in gray) sweeps along a circular annular area of the RGG plate; (b) a magnified view of the laser spot and the coordinate system (not to scale).

Figure 3

Intensity correlation curves for a Gaussian beam ($m=0$) and optical vortices of first ($m=1$) and third ($m=3$) order.

Figure 4

Experimental plots of normalized intensity correlation function for a Gaussian beam ($m=0$) and optical vortex of different orders ($m=1$ to 7).

Figure 5

Theoretical plots of normalized squared field correlation function for a Gaussian beam ($m=0$) and optical vortex of different orders ($m=1$ to 7).

Figure 6

Plots of the normalized correlation time vs order of the vortex for a rotation speed $245.01$ mm/s of the RGG; (a) experimental and (b) theoretical.

Figure 7

Experimental plots of normalized intensity correlation function for a Gaussian beam and optical vortex of different orders.

Figure 8

Theoretical plots of normalized squared field correlation function for a Gaussian beam and optical vortex of different orders.

Figure 9

Plots of the normalized correlation time vs order of the vortex for a rotation speed 397.79 mm/s of the RGG; (a) experimental and (b) theoretical.

Figure 10

Experimental (dotted lines) plots of $g^{\left(2\right)}\left(\tau \right)$ and theoretical (solid lines) plots of $|g^{\left(1\right)}{\left(c\tau \right)|}^2$ for optical vortices of order 3, 4, and 5 with two different linear speeds ($V$) of the RGG plate: (top row) $V=245.01$ mm/s; (bottom row) $V=397.79$ mm/s. For each row, the value of $c$ is 0.66.

Figure 11

Zeros and peaks in the theoretical plots of normalized squared field correlation function for optical vortices of order $m=1$ and $m=2$ when $V=245.01$ mm/s (corresponding to Fig. 5).