Diffractive optics for quasi-direct space-to-time pulse shaping

Abstract

Abstract:The strong chromatic behavior associated with a conventional diffractive lens is fully exploited to propose a novel optical device for pulse shaping in the femtosecond regime. This device consists of two optical elements: a spatially patterned circularly symmetric mask and a kinoform diffractive lens, which are facing each other. The system performs a mapping between the spatial position of the masking function expressed in the squared radial coordinate and the temporal position in the output waveform. This space-to-time conversion occurs at the chromatic focus of the diffractive lens, and makes it possible to tailor the output central wavelength along the axial location of the output point. Inspection of the validity of our device is performed by means of computer simulations involving the generation of femtosecond optical packets.

Synthesis of fractal light pulses by quasi-direct space-to-time pulse shaping

“…In this letter we demonstrate that a kinoform diffractive lens (KDL) can be used to generate self-similar light pulses from any set of circularly symmetric fractal plates (i.e., FZPs or FraGZPs). Our proposal is based on the use of a diffractive pulse shaper that was introduced theoretically [20]. It allows mapping the spatial structure of circularly symmetric binary plates into the temporal domain.…”

“…The temporal window of the shaper Δt is given by the expression Δt a 2 ∕2cz 0 , where c denotes the velocity of light in vacuum and a holds for the maximum extension of the FZP. At the focal point z z 0 , the amplitude of the temporal waveform u out τ is given approximately by the following convolution expression [20]:…”

Programmable quasi-direct space-to-time pulse shaper with active wavefront correction

“…The advantages of these approaches are the compactness of the setups and the saving of time, as the Fouriertransform computation of the spatial patterns is not needed. In this context, the direct space-to-time (DST) [2] and the quasi-direct space-to-time (QDST) [3,4] pulse shapers have demonstrated their utility for highrepetition-rate wavelength-division-multiplexed systems [5], the generation of millimeter waves [6], the generation of fractal light pulses [7], and the study of molecular alignment [8], and also in the spectral domain to obtain bandpass optical filters [9,10].…”

“…In previous versions [3,8], the QDST pulse shaper was composed of two separate elements: a DL and a complex mask facing each other. To construct a single phase mask, both the complex mask transmittance and the DL must be encoded onto the phase-only SLM.…”

“…In our optical setup, the plane z Z 0 was imaged onto the plane of the nonlinear crystal with the help of a telescope composed of two lenses (L 1 and L 2 ) of equal focal length (200 mm). The temporal amplitude of the shaped pulse is approximately given by the convolution of the initial ultrashort pulse with the transmittance of the complex mask in r 2 , previously transformed into the time domain by the conversion constant β 1∕2cZ 0 , where c is the velocity of light in vacuum [3]. Furthermore, the temporal window of the shaper Λ is assessed by the expression Λ r 2 0 β, r 0 4.3 mm being the radial extension of the phase mask.…”