Propagation of asymmetric optical vortex beams through turbulence and evolution of their OAM spectra.

In the realm of wave propagation through turbulent media, the spectrum of the orbital angular momentum of optical vortex beams is known to undergo symmetric broadening. However, the evolution of beams that are initially azimuthally asymmetric represents a distinct phenomenon. In this work, we have developed an analytical model describing the propagation of asymmetric OAM beams through the so-called Kolmogorov turbulence. Our results describe how the perturbation strength and the initial beam properties lead to a nonsymmetric spectrum of OAM modes. These findings lay the groundwork for further use of asymmetric fields that propagate in inhomogeneous media and their applications such as communications and sensing.

Self-referenced single-shot low-power Stokes polarimetry.

We demonstrate a Stokes polarimeter that not only preserves the power of the light to be analyzed but also requires only a single measurement. The novel design relies on the distinctive characteristics of a corner-cube retroreflector. It is simple and robust, and it circumvents the need for a local oscillator or a controllable reference beam.

Differential phase-diversity electrooptic modulator for cancellation of fiber dispersion and laser noise.

Bandwidth and noise are fundamental considerations in all communication and signal processing systems. The group-velocity dispersion of optical fibers creates nulls in their frequency response, limiting the bandwidth and hence the temporal response of communication and signal processing systems. Intensity noise is often the dominant optical noise source for semiconductor lasers in data communication. In this paper, we propose and demonstrate a class of electrooptic modulators that is capable of mitigating both of these problems. The modulator, fabricated in thin-film lithium niobate, simultaneously achieves phase diversity and differential operations. The former compensates for the fiber's dispersion penalty, while the latter overcomes intensity noise and other common mode fluctuations. Applications of the so-called four-phase electrooptic modulator in time-stretch data acquisition and in optical communication are demonstrated.

Phase memory of optical vortex beams.

Optical vortex beams are under considerable scrutiny due to their demonstrated potential for applications ranging from quantum optics to optical communications and from material processing to particle trapping. However, upon interaction with inhomogeneous material systems, their deterministic properties are altered. The way these structured beams are affected by different levels of disturbances is critical for their uses. Here, for the first time, we quantify the degradation of perfect optical vortex beams after their interaction with localized random media. We developed an analytical model that (1) describes how the spatial correlation and the phase variance of disturbance affect the phase distribution across the vortex beams and (2) establishes the regimes of randomness for which the beams maintain the memory of their initial vorticity. Systematic numerical simulations and controlled experiments demonstrate the extent of this memory effect for beams with different vorticity indices.

Single-shot omnidirectional Stokes polarimetry.

Many active sensing applications benefit from measuring, as fast as possible, the polarization state of target reflections. Traditional polarimetry, however, relies on (1) the assumption of field transversality and (2) a given direction of wave propagation. When this is not known, one must regard the field as being three-dimensional, which inherently complicates the polarimetry due to experimental constraints imposed by the planar geometry of detector arrays. We demonstrate a single-shot, Stokes polarimetry approach that alleviates these limitations. The approach is based on the spatial Fourier analysis of the interference between the unknown wave and controlled reference fields.

Discriminating randomly polarized fields.

We introduce the scalar average similarity of an ensemble of randomly polarized states. This global measure is based on the complex degree of mutual polarization between any pair of vector fields in the ensemble. We show that, in the case of fully correlated and globally unpolarized fields, the variation of this parameter is bounded, and its value can effectively discriminate between different configurations of pure states.