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Abstract-We propose a simple and robust method to determine the calibration function of phase-only spatial light modulators (SLMs). The proposed method is based on the codification of binary phase Fresnel lenses (BPFLs) onto an SLM. At the principal focal plane of a BPFL, the focal irradiance is collected with a single device just able to measure intensitydependent signals, e.g., CCD camera, photodiodes, power meter, etc. In accordance with the theoretical model, it is easy to extract the desired calibration function from the numerical processing of the experimental data. The lack of an interferometric optical arrangement, and the use of minimal optical components allow a fast alignment of the setup, which is in fact poorly dependent on environmental fluctuations. In addition, the effects of the zeroorder, commonly presented in the diffraction-based methods, are drastically reduced because measurements are carried out only in the vicinity of the focal points, where main light contributions are coming from diffracted light at the BPFL. Furthermore, owing to the simplicity of the method, full calibration can be done, in most practical situations, without moving the SLM from the original place for a given application.

Abstract-We report on deterministic femtosecond multifilamentation in fused silica by encoding a diffractive microlens array into a spatial light modulator. The efficiency and focal length of each microlens are modified through the addressing voltage. This allows for a precise control on the energy coupled to the filaments thus obtaining a homogenized supercontinuum pattern from an inhomogeneous irradiance input distribution. Slight changes in the focal length of the microlenses allow for independent tailoring of the supercontinuum spectra.

Focusing control of ultrashort pulsed beams is an important research topic, due to its impact to subsequent interaction with matter. In this work, we study the propagation near the focus of ultrashort laser pulses of ~25 fs duration under diffractive focusing. We perform the spatio-spectral and spatio-temporal measurements of their amplitude and phase, complemented by the corresponding simulations. With them, we demonstrate that pulse shaping allows modifying in a controlled way not only the spatio-temporal distribution of the light irradiance in the focal region, but also the way it propagates as well as the frequency distribution within the pulse (temporal chirp). To gain a further intuitive insight, the role of diverse added spectral phase components is analyzed, showing the symmetries that arise for each case. In particular, we compare the effects, similarities and differences of the second and third order dispersion cases.

Abstract-Light beams shaped by programmable megapixel spatial light modulators (SLMs) are key to broaden the applications of photonics. In this paper, we consider the application of a SLM for the generation of two mutually coherent white-light continuum optical sources by filamentation of infrared femtosecond pulses in bulk. We demonstrate that the inhomogeneity of the input beam and the longitudinal separation of the generated filaments are crucial parameters that break down the mutual coherence across neighboring filaments. We show that local control over the optical phase enables us to gain fine control over filament interference effects.