44 research outputs found
Programmable optics for ultrashort pulse management: devices and applications
The contribution of the present report to the field of ultrashort optics has several aspects: from the development of new optical devices for ultrashort pulse management, to the application of those devices for triggering laser-matter interaction processes. In this sense, the key point of this Thesis is the use of reconfigurable phase-only SLMs based on LCOS technology for spatial and temporal shaping of femtosecond pulses. The management of femtosecond pulses demands specific strategies to obtain the desired output response while preventing undesirable distortions. Our results show that programmable diffractive optics encoded in SLMs is a powerful tool for ultrashort (~30 fs) beam management. The reconfigurable nature of SLMs allows wavefront control of an input pulsed beam at a micro scale level. In this way, we have developed devices for transferring amplitude and/or phase maps onto the spatial and temporal profile of an ultrashort pulse. Moreover, our proposals result in very compact optical devices, allowing easy-to-align setups especially suitable for non-expert users. We believe that this fact may promote the use of ultrafast technology in many different scientific fields that demands user-friendly devices for ultrashort pulse control
Dispersion management in two-photon microscopy by using diffractive optical elements
We demonstrate efficient generation of wide-field fluorescence signals in two-photon microscopy exploiting diffractive optical elements and short pulses by using a dispersion-compensated beam delivery optics module. Computer-generated holograms are codified onto a phase-only spatial light modulator, which allows for arbitrary single-shot patterning of the sample. Spatiotemporal shaping of the pulse is mandatory to overcome spatial chirp and pulse-front tilt effects that spread both in space and time the irradiance patterns, thus limiting not only the spatial resolution but also the signal-to-noise ratio in two-photon microscopy. By using a multipass amplifier delivering 30 fs, 0.8 mJ pulses at 1 kHz repetition rate, we experimentally demonstrated arbitrary single-shot fluorescence irradiance patterns in Rhodamine B
Free-Motion Beam Propagation Factor Measurement by Means of a Liquid Crystal Spatial Light Modulator
In contrast to the mechanical scanning procedure
described in the standard ISO/DIS 11146, the use of electronically tunable focal length lenses has proved its capability for the
measurement of the laser beam propagation factor (
) without
moving components. Here, we demonstrate a novel experimental
implementation where we use a low-cost programmable liquid
crystal spatial light modulator (SLM) for sequentially codifying
a set of lenses with different focal lengths. The use of this kind of
modulators introduces some benefits such as the possibility for
high numerical aperture or local beam control of the phase of the
lenses which allows for minimizing systematic errors originated by
lens aberrations. The beamwidth, according to the second-order
moment of the irradiance, is determined for each focal length by
using a digital sensor at a fixed position with respect to the spatial
light modulator. After fitting the measured data to the theoretical
focusing behavior of a real laser beam, the beam propagation
factor is obtained. We successfully validated the results in the laboratory where a full digital control of the measurement procedure
without mechanical scanning was demonstrated
Fresnel phase retrieval method using an annular lens array on an SLM
Wavefront aberrations play a major role when
focusing an ultrashort laser pulse to a high-quality focal
spot. Here, we report a novel method to measure and
correct wavefront aberrations of a 30-fs pulsed laser beam.
The method only requires a programmable liquid-crystal
spatial light modulator and a camera. Wavefront retrieval is
based on pupil segmentation with an annular lens array,
which allows us to determine the local phase that mini-
mizes focusing errors due to wavefront aberrations. Our
method provides accurate results even when implemented
with low dynamic range cameras and polychromatic
beams. Finally, the retrieved phase is added to a diffractive
lens codified onto the spatial light modulator to experi-
mentally demonstrate near-diffraction-limited femtosecond
beam focusing without refractive components
Programmable quasi-direct space-to-time pulse shaper with active wavefront correction
We experimentally demonstrate an extremely compact and programmable pulse shaper composed of a single phase mask encoded into a spatial light modulator. Its principle of operation is similar to the previously theoretically introduced quasi-direct space-to-time pulse shaper [Opt. Express 16, 16993 (2008)], which is based on diffractive optics. The proposed pulse shaper exhibits not only real-time temporal modulation, but also high-efficiency output pulses thanks to an active correction of the wavefront aberrations.This research was funded by the Spanish Ministerio de Ciencia e Innovación and the Generalitat Valenciana through Consolider Programme (SAUUL CSD2007-00013), and Prometeo Excellence Programme (PROMETEO/2012/021), and projects FIS2010-15746, P11B2010-26, and CTQ2008- 02578. We also thank the European network ITN FAS- TQUAST (PITN-GA-2008-214962). Authors are also very grateful to the SCIC of the Universitat Jaume I for the use of the femtosecond laser
Controlled Multibeam Supercontinuum Generation With a Spatial Light Modulator
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
Dynamic Control of Interference Effects Between Optical Filaments through Programmable Optical Phase Modulation
Light beams shaped by programmable megapixel spatial light modulators (SLMs) are key to broadening 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.This work was supported by Generalitat Valenciana through the programme (PROMETEO\2012\021), Spanish Ministry of Science
under Grant FIS2013-40666-P) and University Jaume I through the project P1 1B2013-53
Tailoring the spatio-temporal distribution of diffractive focused ultrashort pulses through pulse shaping
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 spatiotemporal
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
Tailoring the spatio-temporal distribution of diffractive focused ultrashort pulses through pulse shaping
[EN]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
Diffraction-Based Phase Calibration of Spatial Light Modulators With Binary Phase Fresnel Lenses
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 intensity-dependent 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 zero-order, 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.This work was supported in part from MINECO under Grant
FIS2013–40666-P, Generalitat Valenciana under Grants PROMETEO2012–021
and ISIC 2012/013, and Universitat Jaume I (P1-1B2012-55)