Phase-shift interference-based wavefront characterization for orbital angular momentum modes

Abstract

Wavefront characterization for orbital angular momentum (OAM) modes is demonstrated using quadrature phase-shift interference. The phase fronts and intensity profiles of OAM(-2), OAM(-4), OAM(-6), and OAM(-8) are measured. Wavefront correlations between the experimental results and the pure Laguerre-Gaussian modes are calculated to evaluate the measurement. The measured results are in reasonable agreement with the anticipated results based on simulations.

Vortex beam: generation and detection of orbital angular momentum [Invited]

“…Moreover, when the vortex beam interferes with a coaxial plane wave, it can be expected to be a petal-like interference pattern, the number of which is jlj due to its spiral phase factor expilϕ. Interfering with the spherical wave instead of the plane wave, the interference pattern will be helical fringes, and the number of fringes is also l [75,76] . Also, the vortex beam can be measured by interfering with its mirror image [77,78] .…”

Universal orbital angular momentum spectrum analyzer for beams

“…After interfere with E R , two various interfere patterns can be captured by introducing 0 and π/2 phase delay for E R , as I cos = |E + E R | 2 and I sin = |E + E R exp (iπ/ 2)| 2 . Then the phase Φ is calculated as Φ = arctan[(I sin -I-I R )/(I cos -I-I R )], where I R is the captured intensity profile of the reference Gaussian beam [49]. By now the complex amplitude of the beam to be analyzed is well recovered as:…”

“…In this paper, motivated by the wavefront diagnosing [49], we demonstrate a universal approach to accurately measure the OAM spectra of beams. In the proposed scheme, a stable but simple interferometer is built, where a probe Gaussian beam is introduced, and interfere with the beam to be measured.…”

Phase correction for a distorted orbital angular momentum beam using a Zernike polynomials-based stochastic-parallel-gradient-descent algorithm

“…Feedback signals: As shown in [24], the mode purity of an OAM beam increases monotonically with increasing quality of its intensity profile, which is defined as correlation coefficient C k between the far-field intensity profile of the OAM beam Ir; θ and its ideal intensity distribution I id r; θ, namely,…”

“…Figures 8(a) and 8(b) show the BERs of the OAM 3 channel before and after phase correction for two turbulence realizations. Without phase correction, the BER can barely reach the forward error correction (FEC) limit of 3.8 × 10 −3 [24], because of the large amount of crosstalk from the other two channels. With the phase correction, the BER could achieve the FEC limit.…”