Diffraction is a phenomenon related to the wave nature of light and arises when a propagating wave comes across an obstacle. Consequently, the wave can be transformed in amplitude or phase and diffraction occurs. Those parts of the wavefront avoiding an obstacle form a diffraction pattern after interfering with each other. In this review paper, we have discussed the topic of non-diffractive beams, explicitly Bessel beams. Such beams provide some resistance to diffraction and hence are hypothetically a phenomenal alternate to Gaussian beams in several circumstances. Several outstanding applications are coined to Bessel beams and have been employed in commercial applications. We have discussed several hot applications based on these magnificent beams such as optical trapping, material processing, free-space long-distance self-healing beams, optical coherence tomography, superresolution, sharp focusing, polarization transformation, increased depth of focus, birefringence detection based on astigmatic transformed BB and encryption in optical communication. According to our knowledge, each topic presented in this review is justifiably explained.

Bessel Beam: Significance and Applications-A Progressive Review.

Rays, waves, SU(2) symmetry and geometry: toolkits for structured light

Spinning object detection based on perfect optical vortex

In this Letter, we introduce a new class of angular dependent autofocusing ring Pearcey beams by imposing a cross-phase structure. Due to this structure, the beam exhibits a non-uniform abrupt autofocusing behavior. Unlike the properties of the ring Pearcey beam without a cross phase [Opt. Lett.43, 3626 (2018)OPLEDP0146-959210.1364/OL.43.003626], we can flexibly adjust the focal length of the beam and its focusing ability, as well as the direction of the ring Pearcey beams, with the help of only the cross-phase structure. Furthermore, the Poynting vectors are employed to demonstrate convincingly the beam-focusing mechanism. Such beams with these fascinating characteristics are anticipated to find potential applications in optical tweezing, three-dimensional printing, material processing, and so on.

Flexible autofocusing properties of ring Pearcey beams by means of a cross phase.

An erratum is presented to correct funding section of [Opt. Express 27(17), 24781-24792 (2019)].

Detection of spinning objects at oblique light incidence using the optical rotational Doppler effect: erratum.

The discovery of the optical rotational Doppler effect associated with orbital angular momentum of light paves a new way to detect the rotational speed of spinning objects. In this paper, we investigate the influence of lateral misalignment, i.e., the distance between the beam axis of a probe light and the rotation axis of a spinning object, on the rotational Doppler effect. First, we analyze the mechanism of the rotational Doppler effect of optical vortices based on the linear Doppler effect. Specifically, we consider the general case where the center of the optical vortex does not coincide with the rotation axis, and deduce the generalized formula of rotational Doppler shift based on a local scattering model. It is found that the bandwidth of the rotational Doppler signal depends proportionally on the amount of lateral misalignment, whereas the value of rotational Doppler shift remains constant. A proof-of-concept experiment is performed, and the measured results agree well with theoretical predictions. These findings may be useful for practical application of the optical rotational Doppler effect in remote sensing and metrology.

Influence of lateral misalignment on the optical rotational Doppler effect.

Rotational Doppler effect (RDE) has attracted much attention in recent years which opens new avenues to angular velocity measurement. However, most previous studies used single-frequency vortex light as the detection beam so that the rotational Doppler signal is in the low frequency domain where most of noise signals exist. In this article, we use the dual-frequency 2-fold multiplexed vortex light as the probe beam and transform the Doppler signals from the low frequency domain to the high frequency domain successfully. The results show hardly any noise compared with the measurement in the low frequency domain. More importantly, the direction of rotation can be obtained directly by comparing the modulated signal and the reference signal. Our work demonstrates a new detection method for the RDE and provides a reference for its practical application.

Direction-sensitive detection of a spinning object using dual-frequency vortex light.

Increasing demand for practical applications is forcing more in-depth research into optical vortices (OVs): from the generation and measurement to the shaping and multi-singularity manipulation of OVs. Herein, we propose a new type of phase structure called the high-order cross-phase (HOCP), which can be employed to modulate OVs to implement polygonal shaping and multi-singularity manipulation simultaneously at far-field. Theoretically, we investigate the propagation characteristics of OVs modulated by a HOCP. In experiments, we achieve the polygonal shaping and multi-singularity manipulation of OVs via HOCPs. On this basis, we discuss the relationship between shapes and the orders of HOCPs, where we find that the order of a HOCP is exactly equal to the number of sides of polygonal OVs. This work provides a novel method to achieve polygonal shaping and multi-singularity manipulation simultaneously, which facilitate applications in optical micro-manipulation and optical communication.

Song Qiu

Papers

Influence of lateral misalignment on the optical rotational Doppler effect.

Spinning object detection based on perfect optical vortex

Detection of spinning objects at oblique light incidence using the optical rotational Doppler effect: erratum.

Direction-sensitive detection of a spinning object using dual-frequency vortex light.

Polygonal shaping and multi-singularity manipulation of optical vortices via high-order cross-phase.