High power radially-polarized Yb-doped fiber laser

A simple technique for directly generating a radially-polarized output beam from an ytterbium-doped fiber laser using an intracavity spatially-variant waveplate is reported. The laser yielded 32W of output with a corresponding slope efficiency of 65.8% in a radially-polarised beam with beam propagation factor ~2.1 and polarization purity >95%

Self-assembled nanostructuring of a-Si:H films with ultrashort light pulses

For several decades, hydrogenated amorphous silicon (a-Si:H) has been playing a significant role in the world's production of photovoltaic modules. In this work, we investigate different types of modifications induced by a femtosecond laser in a-Si:H thin films. We demonstrate that several distinctive modification regimes with peculiar optical properties can be obtained in a narrow range of the laser pulse energies

Engineering anisotropy in glass with ultrafast laser assisted nanostructuring

Recent applications of femtosecond laser assisted self-assembled nanostructures will be overviewed. Specifically, polarization sensitive optical elements and 5-dimensional optical data storage with practically unlimited life-time will be demonstrated and discussed

Visible luminescence from hydrogenated amorphous silicon modified by femtosecond laser radiation

Visible luminescence is observed from the composite of SiO2 with embedded silicon nanocrystallites produced by femtosecond laser irradiation of hydrogenated amorphous silicon (a-Si:H) film in air. The photoluminescence originates from the defect states at the interface between silicon crystallites and SiO2 matrix. The method could be used for fabrication of luminescent layers to increase energy conversion of a-Si:H solar cells

Ultrafast laser nanostructuring of glass: from S-waveplate to multidimensional data storage

Material processing with ultrafast lasers has attracted considerable interest due to new science and a wide range of applications from laser surgery, integrated optics to optical data storage. A decade ago it has been discovered that under certain irradiation conditions ordered sub-wavelength structures with features smaller than 20 nm can be formed in the volume of silica glass. Here we discuss recent applications of self-assembled sub-wavelength structuring specifically polarization converters branded as the S-waveplate and polarization multiplexed optical data storage

Femtosecond laser nanostructuring for high-topological charge vortex tweezers with continuously tunable orbital angular momentum

It is well known that the light carries linear and angular momentum that can be transferred to the irradiated objects. Angular momentum of the beam is comprised of spin angular momentum (SAM) and orbital angular momentum (OAM). SAM is associated to the beam's polarization and is always intrinsic. OAM comes from the azimuthal phase variations of the beam and can be both extrinsic and intrinsic. The beam with helical phase phi = l.Phi, where phi is phase, Phi is polar angle and l is positive or negative integer number, possesses well-defined OAM with l.h [1]. Such beams are often referred to as optical vortices and are exploited in optical tweezer experiments enabling the rotation of trapped particles. Changing the wavefront's helicity, also the geometry of the beam is changed. The higher is |l|, the larger is the diameter of the beam. In order to change the total angular momentum of the beam, either the shape of the beam or the photon density has to be changed. As a result, the experiments which require fixed beam size and intensity are limited to fixed OAM. Recently, we implemented optical tweezers with tunable angular momentum, there OAM could be changed from -1 to 1 by controlling ellipticity of the incident laser beam. Here we extend this technology and demonstrate the generation of optical vortices of high topological charge up to 100 (Fig. 1(a)-(i)) using femtosecond laser written polarization converters (the S-waveplate) [2]

Direct generation of radially-polarized output from an Yb-doped fiber laser

A simple technique for directly generating a radially-polarized output beam from an ytterbium-doped fiber laser using an intracavity S-waveplate is reported. The laser yielded 7W of output with a corresponding slope efficiency of 67%

Second-harmonic vortex generation with a poled glass

A Simple method for nonlinear vortex generation is presented. Spin-to-Orbital transfer with total angular momentum conservation between photons at the fundamental and at the second-harmonic frequency is demonstrated

Femtosecond laser printed microoptics in hydrogenated amorphous silicon

Conventional optics (e.g. lenses or mirrors) manipulates the phase via optical path difference by controlling thickness or refractive index of material. Recently, a promising type of optics emerged which exploits geometric phase shift, when a lightwave is transformed by parameter other than optical path difference, e.g. polarization. Here, wavefront is modified by introducing spatially varying anisotropy and is a result of Panchatraman-Berry phase [1]. Theoretically any phase pattern can be achieved solely by means of geometric phase with efficiencies reaching 100% [2]. This allows continuous optical phase shifts and without phase resets, in stark contrast to conventional elements, wherein phase profiles are encoded as discrete optical path variations in refractive index or thickness, limiting performance. The geometric phase optics is a promising alternative for controlling and manipulating light, but it stumbles on the lack of adequate fabrication technology