Efficient Optical Energy Harvesting in Self-Accelerating Beams

Abstract

We report the experimental observation of energetically confined self-accelerating optical beams propagating along various convex trajectories. We show that, under an appropriate transverse compression of their spatial spectra, these self-accelerating beams can exhibit a dramatic enhancement of their peak intensity and a significant decrease of their transverse expansion, yet retaining both the expected acceleration profile and the intrinsic self-healing properties. We found our experimental results to be in excellent agreement with the numerical simulations. We expect further applications in such contexts where power budget and optimal spatial confinement can be important limiting factors.

Figure 1. Propagation characteristics of self-accelerating beams initiated from a circular Gaussian beam.

(a) Beam pattern obtained experimentally at z = 4.2 cm for the parabolic trajectory and (c) the spectral intensity corresponding to its main hump only. (b) Radial position of the main hump and (d) corresponding key spatial frequencies as a function of propagation distance measured for the three studied trajectories given in Table 1, where the dotted, dashed, and solid curves are from analytical results and the markers show the corresponding experimental results.

Figure 2. Propagation characteristics of self-accelerating beams initiated from an elliptical beam.

(a) Phase mask applied on the SLM for a parabolic trajectory and corresponding beam intensity overlap at 95% cutoff for an elliptical incident Gaussian beam (red shading) reshaped from its circular counterpart (blue shading). (b) Radial position of the main hump as a function of propagation obtained for the three convex trajectories. Lines and markers show, respectively, the analytical and experimental results. (c–d) Experimental transverse intensity maps at z = 0 and z = 5.3 cm for the case of the parabolic trajectory.

Figure 3. Peak intensity enhancement relative to the input beam asymmetry.

(a) Expected peak intensity enhancement for the parabolic trajectory case calculated as a function of the minor diameter (ds’) of the elliptical Gaussian beam. The major diameter is constrained to the experimental value of ds = 5.96 mm. (b–d) Measured peak intensities as a function of the longitudinal distance obtained for the trajectories under investigation. The results obtained in the case of an elliptical (red) and a circular (blue) incident beam are compared. Lines and markers respectively show simulation fittings and experimental results.

Figure 4. Experimental results illustrating the self-healing of a 2D accelerating beam initiated from an elliptical beam following a parabolic trajectory.

Transverse intensity maps at (a) z = 0, where the main hump has been blocked at the onset of propagation, and (b) z = 5.3 cm. The parameters for the beam are the same as those of Fig. 2(c–d).