Ultrashort vortex from a Gaussian pulse – An achromatic-interferometric approach

Abstract

The more than a century old Sagnac interferometer is put to first of its kind use to generate an achromatic single-charge vortex equivalent to a Laguerre-Gaussian beam possessing orbital angular momentum (OAM). The interference of counter-propagating polychromatic Gaussian beams of beam waist ωλ with correlated linear phase (ϕ 0 ≥ 0.025 λ) and lateral shear (y 0 ≥ 0.05 ωλ) in orthogonal directions is shown to create a vortex phase distribution around the null interference. Using a wavelength-tunable continuous-wave laser the entire range of visible wavelengths is shown to satisfy the condition for vortex generation to achieve a highly stable white-light vortex with excellent propagation integrity. The application capablitiy of the proposed scheme is demonstrated by generating ultrashort optical vortex pulses, its nonlinear frequency conversion and transforming them to vector pulses. We believe that our scheme for generating robust achromatic vortex (implemented with only mirrors and a beam-splitter) pulses in the femtosecond regime, with no conceivable spectral-temporal range and peak-power limitations, can have significant advantages for a variety of applications.

CEP-stable few-cycle pulses with more than 190 μJ of energy at 100 kHz from a noncollinear optical parametric amplifier

“…Amidst these methods, Atencia et al developed a compound holographic optical element to generate achromatic vortices [20], while Swartzlander designed achromatic spiral phase plates from two different glasses, providing a perfect topological charge at two wavelengths, akin to achromatic lenses [21]. who introduced an elegant approach based on a Sagnac interferometer to generate achromatic vortices [22], these techniques often prove complex or challenging to implement, and/or incompatible with the generation of high-energy ultra broadband vortex pulses. An alternative to generating a wide-band optical vortex directly (i.e., transforming a field without OAM), is to use an optical parametric chirped pulse amplifier (OPCPA) [23] to transfer the OAM of a narrowband pump beam to a wide-band idler beam.…”

Frequency-Doubled High-Power Optical Vortex Beam With Sub 500 fs Pulse Duration

“…This system was based on tiled-aperture coherent beam combination where the VBs were generated by individually controlling the phase of each laser channel. Another approach is the interferometric generation of VBs directly inside a resonator [21]. The generation of up to 31 W of average power at a repetition rate of 600 kHz and at a wavelength of 1064 nm was demonstrated in a Q-switched laser with this scheme [22].…”

High-order femtosecond vortices converted from a tunable high-order Hermite–Gaussian Yb:CALGO laser

“…However, limited reports are available on the generation of high-order tunable femtosecond vortices using active methods. Passive femtosecond vortex laser generators utilize the spiral phase plate [13,14], computer-generated hologram [15], axially symmetric polarizer/axially symmetric half-wave plate [16], uniaxial crystal [17], spiral grating [18], spiral multi-pinhole plate [19], Sagnac interferometer [20], and cylindrical lens pair [21][22][23]. It is reported that computer generated holograms and cylindrical lens mode converters can realize a high-order tunable femtosecond vortex laser.…”