Controlling the spectral rotation of ultrashort vortex pulses

Ultrashort Vortex Pulses with Controlled Spectral Gouy Rotation

“…The experimental setup for rotational pulse control in spectral domain with pulsed polychromatic Bessel-Gauss beams is schematically drawn in Figure 2. The studies were performed with a linearly polarized Ti: sapphire laser oscillator as the light source (Tsunami, Spectra Physics, formerly Mountain View, CA, USA) maximum spectral FWHM width 12 nm, minimum pulse duration 80 fs, central wavelength 795 nm, repetition rate 80.2 MHz, pulse energy <8 nJ) [44]. The capability of adaptive and passive optical components to generate OAM beams with variable spatio-spectral parameters, in particular to control the spectral Gouy rotation of pairs of blue-and red-shifted spectral eyes, was studied.…”

“…The capability of adaptive and passive optical components to generate OAM beams with variable spatio-spectral parameters, in particular to control the spectral Gouy rotation of pairs of blue-and red-shifted spectral eyes, was studied. Bessel-Gauss beams were either shaped by static lithographically structured, transmissive spiral phase gratings (SPG) [51][52][53] and continuous-relief spiral phase plates (SPPs) [54], or spiral and forked gratings flexibly programmed into the phase map of a liquid-crystal-on-silicon (LCoS) spatial light modulator (SLM) (GAEA 2, HOLOEYE Photonics AG, Berlin, Germany) [44]. The SLM enables one to individually address 4160 × 2464 pixels with 3.74 µm pitch at a fill factor of 90% with a frame rate of 58 Hz and 8 Bit dynamic range.…”

“…The reflective operation mode requires working at an oblique angle of incidence to avoid the insertion of dispersive beam splitters. The resulting geometrical distortions in one spatial direction can easily be corrected by an adapted linear transformation (stretching or shrinking) with the programmable display [44]. The average laser power density on the SLM was always chosen to ensure a linear operation.…”

“…Relevant geometrical parameters for Spiral Phase Gratings (SPGs) as used in our experiments are listed in Table 1 [44]. To quantitatively compare the influence of diffraction, Fresnel numbers for half of the axial focal zone depths at a central wavelength of 800 nm are included.…”

“…Here, we report on the results of proof-of-principle experiments with the aim to control the angular frequency of the rotating spectral eyes. The performance of different types of spiral phase shapers is compared [44]. The generation of axially variable angular velocity by a programmable, radially chirped spiral grating is demonstrated.…”