In situ tomography of femtosecond optical beams with a holographic knife-edge

Abstract

We present an in situ beam characterization technique to analyze femtosecond optical beams in a folded version of a 2f-2f setup. This technique makes use of a two-dimensional spatial light modulator (SLM) to holographically redirect radiation between different diffraction orders. This manipulation of light between diffraction orders is carried out locally within the beam. Because SLMs can withstand intensities of up to I ∼ 10(11) W/cm2, this makes them suitable for amplified femtosecond radiation. The flexibility of the SLM was demonstrated by producing a diverse assortment of "soft apertures" that are mechanically difficult or impossible to reproduce. We test our method by holographically knife-edging and tomographically reconstructing both continuous wave and broadband radiation in transverse optical modes.

Extension of filament propagation in water with Bessel-Gaussian beams

“…The input beam patterns were created from an initial Gaussian beam of a Ti:sapphire laser system (pulse duration of ∼50 fs, central wavelength of 800 nm, and an output energy of 1 mJ per pulse at a 1 kHz repetition rate) by using computer generated-holograms 30 displayed on a liquid crystal spatial light modulator (Hamamatsu LCOS-SLM X10468-2). The SLM had a resolution of 800x600 pixels (16 mm x 12 mm), and a maximum reflectivity of >95% for radiation between 750 nm and 850 nm.…”

Cascade Raman sideband generation and orbital angular momentum relations for paraxial beam modes

“…The produced optical beam modes were then sent into the beam crossing setup and allowed to interact in the Raman-active crystal. When the device is used to produce off-axis holograms, amplitude information can also be encoded in the computer generated holograms by redirecting radiation between orders [2,14]. This phase-amplitude encoding produces high fidelity beam modes but at the expense of pulse energy.…”

“…Applications of optical modes include: optical manipulation of Bose Einstein (BECs) condensates, such as tight confinement using Hermite Gaussian (HG) modes [4]; transfer of angular momentum with Laguerre Gaussian (LG) modes [5,6]; optical spanners [7] and pumps [8]; imaging of cytoskeletal filaments (stimulated emission depletion) [9] multiplexing and cryptography [10,11] and the search for exoplanets (optical vortex coronagraph) [12]. The success of many high-field experiments is possible by advances in the generation and analysis of beam modes in femtosecond fields [2,13,14]. However, investigations of highly nonlinear interactions of beam modes with matter have remained largely unexplored.…”

“…LG [18]. The polynomials used are: the Hermite [14], Laguerre [14], as well as the even and odd Ince [18] respectively. Reference [18] contains the full derivation of the IG modes.…”

Three-dimensional measurement of a tightly focused laser beam

“…Strohaber et al introduced a holographic knifeedge for in situ femtosecond optical beam tomography with micron (μm) resolution. 16 17 suggested a method to obtain a 2D profile of the focused light spot by repeating the knife-edge scanning process at different scanning angles, which is similar to Dorn's method.…”