Generation Of Such Beams Research Articles

Structurally Invariant Higher-Order Ince-Gaussian Beams and Their Expansions into Hermite-Gaussian or Laguerre-Gaussian Beams

Paraxial beam modes, which propagate in space and focus without changing their transverse intensity pattern, are of great value for multiplexing transmitted data in optical communications, both in waveguides and in free space. The best-known paraxial modes are the Hermite-Gaussian and Laguerre-Gaussian beams. Here, we derive explicit analytical expressions for Ince-Gaussian (IG) beams for several first values of the indices p = 3, 4, 5, and 6. In total, we obtain expressions for the amplitudes of 24 IG beams. These formulae are written as superpositions of the Laguerre-Gaussian (LG) or Hermite-Gaussian (HG) beams, with the superposition coefficients explicitly depending on the ellipticity parameter. Due to simultaneous representation of the IG modes via the LG and HG modes, it is easy to obtain the IG modes in the limiting cases wherein the ellipticity parameter is zero or approaches infinity. The explicit dependence of the obtained expressions for the IG modes on the ellipticity parameter makes it possible to change the intensity pattern at the beam cross-section by continuously varying the parameter values. For the first time, the intensity distributions of the IG beams are obtained for negative values of the ellipticity parameter. The obtained expressions could facilitate a theoretical analysis of properties of the IG modes and could find practical applications in the numerical simulation or generation of such beams with a liquid-crystal spatial light modulator.

The generation of femtosecond optical vortex beams with megawatt powers directly from a fiber based Mamyshev oscillator.

Numerous approaches have been developed to generate optical vortex beams carrying orbital angular momentum(OAM) over the past decades, but the direct intracavity generation of such beams with practical output powers in the femtosecond regime still remains a challenge. Here we propose and experimentally demonstrate the efficient generation of high-peak-power femtosecond optical vortex pulses from a Mamyshev oscillator (MO) based on few-mode polarization-maintaining (PM) ytterbium-doped fibers (YDFs). By employing an appropriate intracavity transverse spatial mode selection technique, ultrafast pulses carrying OAM with selectable topological charge of l=±1 are successfully generated with an average output power of∼5.72W at ∼24.35MHz repetition rate, corresponding to a single pulse energy of ∼235nJ.The chirped pulses can be compressed to ∼76fs outside the cavity, leading to a pulse peak power of ∼2.2MW. To the best of our knowledge, this isby far the highest pulse energy and peak power for optical vortex pulses ever generated directly from a fiber oscillator. This unprecedented level of performance should be of great interest for a variety of applications including materials processing and imaging.

Reconfigurable structured light generation in a multicore fibre amplifier

Structured light, with spatially varying phase or polarization distributions, has given rise to many novel applications in fields ranging from optical communication to laser-based material processing. However the efficient and flexible generation of such beams from a compact laser source at practical output powers still remains a great challenge. Here we describe an approach capable of addressing this need based on the coherent combination of multiple tailored Gaussian beams emitted from a multicore fibre (MCF) amplifier. We report a proof-of-concept structured light generation experiment, using a cladding-pumped 7-core MCF amplifier as an integrated parallel amplifier array and a spatial light modulator (SLM) to actively control the amplitude, polarization and phase of the signal light input to each fibre core. We report the successful generation of various structured light beams including high-order linearly polarized spatial fibre modes, cylindrical vector (CV) beams and helical phase front optical vortex (OV) beams.

Nondiffracting beam emission from hyperbolic metasurfaces

We demonstrate highly directive and transversely confined emissions from hyperbolic metasurfaces (HMSs) to free-space. The generation of such beams is attributed to the narrow hyperbolic isofrequency contour, such that only propagating waves with their wavevectors near normal incidence can transmit through the medium. The directions of transmitted waves’ Poynting vectors are altered by the medium and become parallel to the propagation direction, resulting in the generation of nondiffracting beams. We also suggest a realization of the proposed HMS using a layered silver-dielectric structure for optical wavelengths.

Generation of self-imaged optical bottle beams

We propose a novel technique to generate self-imaged optical bottle beams by interfering two Bessel beams with varying radial propagation constant or radial frequency. The optical bottle beams have on-axis intensity minima along the propagation direction surrounded with regions of higher intensity. We introduce the phenomena of self-imaging in an optical bottle beam to possess numerous bottles embedded in a single beam. This removes the constraint on optical bottle beams to possess p bottles or null intensity points, where p is radial mode index of a Laguerre–Gaussian beam used to generate it, as reported by McGlaoin [Opt. Commun. 225 (2003) 215]. This technique also provides additional freedom on the bottle size and its location, which can be pre-determined. Both simulation and experimental results for the generation of such beams are reported in the paper.

Phase singularities in beams

Beams of electromagnetic radiation with phase singularities can transport angular momentum and exert torques on objects. In this paper we discuss the generation of such beams and present a simple analysis of the phenomenon. These beams and their effects have been studied at optical and at millimeter wavelengths. We describe a particularly efficient way of generating these beams at millimeter wavelengths employing a specially configured blazed grating.

Formation of a beam with a uniform intensity distribution in a CO2 laser with a generalised confocal cavity

A description is given of a method of forming, in a composite confocal cavity, non-Gaussian light beams with a uniform intensity distribution. The method is based on the use of a reflector with discretely distributed absorbing or scattering inhomogeneities. Theoretical and experimental confirmations are reported of the generation of such beams at the output of a CO2 laser with a nonuniform amplitude-stepped mirror.