Complete characterization of ultrashort optical pulses with a phase-shifting wedged reversal shearing interferometer

Abstract

The ability of an interferometer to characterize the spatial information of a light beam is often limited by the temporal profile of the beam, with femtosecond pulse characterization being particularly challenging. In this study, we developed a simple, stable, controllable shearing and vectorial phase-shifting wedged reversal shearing interferometer that is able to characterize all types of coherent and partially coherent light beams. The proposed interferometer consists of only a single beam splitter cube with one wedged entrance face and is insensitive to environmental vibration due to its common path configuration. A near zero-path length difference of the proposed interferometer ensures its operation for ultrashort pulses, providing, for the first time, a simple and stable interferometric tool to fully characterize sub-100 fs laser pulses. All common beam characterization can be carried out with the interferometer, such as the amplitude, phase, polarization, wavelength, and pulse duration. Furthermore, this technique is sensitive to the wavefront tilt and can be used for precise beam alignment. Therefore, this interferometer can be an essential tool for beam characterization, optical imaging, and the testing required for a wide range of applications, including astronomy, biomedicine, ophthalmology, optical testing and imaging systems, and adaptive optics.

Spatial Wavefunction Characterization of Femtosecond Pulses at Single-Photon Level

“…This setup shows similarity to the wedged reversal shearing interferometer in Ref. [28]. However, the spatial chirp issue discussed above was not resolved in Ref.…”

“…Subsequently, the phase information is obtained by intercepting the beam using the CDSI and capturing the images of the interferograms, which requires eight ensemble-averaged measurements. In principle, the wavefront can also be extracted by curve fitting using only the interferograms with shearing amounts of s x = 300µm and s y = 300µm [28]. However, this can result in severe fitting errors for single photons.…”

“…However, the spatial chirp issue discussed above was not resolved in Ref. [28]. Furthermore, the previous technique cannot be applied to single photons due to the stringent requirements for single-photon measurement.…”

“…In the final expression, we do not propagate the initial wavefunctions because the entrance plane of the BSC is imaged. We assume perfect temporal coherence even for pulse duration in the femtosecond regime because CDSI guarantees near-zero optical path difference and group velocity dispersion due to near-equal arm length in the same medium [28]. Hence, the selfinterfering left and right portions of the wavefunction are automatically mode matched temporally.…”

Investigations into femtosecond laser hybrid manufacturing for 3D power sources

“…Effectively utilising fsDLW requires the development of a process that can repeatably and consistently form and characterise 3D PG structures need to be overcome, to account for the uneven fluence during acceleration of the scanning mirrors [162]. The challenge facing direct patterning with fsLIL, on the other hand, stems from the low temporal coherence of femtosecond pulses [163]. Maintaining this temporal coherence for requires fine control over the path length difference between each beam path, which necessitates the development of a fsLIL set-up that allows for high fluence patterning while being flexible and simple to calibrate.…”