Novel TC and FTC Detection Techniques for Vortex Beams: Addressing Wandering Perturbations and Obstacle Occlusion

(2) This section presents a novel TC detection technology for vortex beams that is capable of detecting wandering perturbations and obstacle occlusion. The proposed method uses a single cylindrical lens to detect the average OAM value and obtain the TC value of vortex beams. Comparing the TC detection results of the light intensity method, the Fourier transform method, and the phase method under extreme conditions (sector-shaped opaque obstacle blocking more than 180ﾰ), it is evident that the above detection methods are ineffective. Only the detection methods proposed in this section can accurately determine the TC value size and symbol of the input beam. This technique effectively addresses the problem of detecting the TC of vortex beams under the interference of non-ideal factors such as obstruction and environmental wandering perturbations. The proposed TC detection method against beam wanders and obstruction has significant applications in optical communication and optical encryption based on vortex beams.

(3) This section proposes a novel method for detecting the fractional topological charge (FTC) of a vortex beam using a holographic phase plate. The proposed method involves changing the phase difference of the holographic phase plate so that three minimum visibility (left opening, right opening, left opening) continuously appear on both sides of the vortex beam, recording the phase differences corresponding to the three minimum visibility, and calculating the FTC using the formula. This method effectively solves the problem of a complex device and prone to experimental errors in detecting FTC using a phase plate and provides a detection scheme for FTC in wandering perturbations environment.