Fig. 1. Schematics of a Gaussian light beam that is partially obstructed by an object that has a rotational orientation (ϕo) and theoretically calculated spiral spectra and phase differences of the partially obstructed Gaussian light beam’s constituent OAM modes as described in the text. The spiral spectra are normalized with respect to the sum of the powers of OAM modes from ℓ=−10 to ℓ=+10. The phase differences are relative to the phase of the ℓ=0 OAM mode.

Fig. 2. Experimental setup as described in the text.

Fig. 3. Measured phase differences (θ) between the ℓ=−1 and ℓ=+1 OAM modes of the partially obstructed Gaussian light beam as a function of the rotation angle (ϕo) as described in the text. Circles represent measured values. Solid lines represent theoretically calculated values. Note that the error bars are smaller than the markers.

Fig. 4. Measured phase differences (θ) between the ℓ=0 and ℓ=+1 OAM modes of the partially obstructed Gaussian light beam as a function of the rotation angle (ϕo) as described in the text. Circles represent measured values. Solid lines represent theoretically calculated values. Note that the error bars are smaller than the markers.

Fig. 5. Measured phase differences (θ) between the ℓ=−1 and ℓ=+1 OAM modes of the partially obstructed Gaussian light beam for three varying positions of R’s edge with respect to the light beam’s center as described in the text. Circles represent measured values. Solid lines represent theoretically calculated values. Note that the error bars are smaller than the markers.