This PDF file contains the front matter associated with SPIE Proceedings Volume 11270 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

The generation and use of THz radiation for electron acceleration and manipulation of electron bunches has progressed over the last decade to a level where practical devices for THz guns, acceleration and a wide range of beam manipulations have become possible. Here, we present our progress on generation of single-cycle THz pulses at the two-hundred micro- Joule level to drive advanced acceleration and beam manipulation devices. Specifically, we use pulses centered at 0.3 THz to power a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the 6D-phase-space of ultrashort electron bunches. Using this STEAM device, we demonstrate record THzacceleration of >60 keV, streaking with <10 fs resolution, focusing with >2 kT/m strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of THz-based electron accelerators, manipulators and diagnostic tools enabling science beyond current resolution frontiers with transformative impact.

Laser Induced Forward Transfer (LIFT) process has been utilized as a novel microfabrication tool for the printing of a plurality of organic and inorganic materials, both in liquid and in solid phase, with dimensions down to a few microns, on substrates such as glass, silicon and flexible polymers. LIFT is a direct-write method that can print viable bioinks including living cells in predefined 2D or 3D patterns. It offers many advantages over other direct-write techniques: It is contact-less, offers high spatial control (10-100μm) and is able to print a great variety of materials in terms of viscosity.

The main aim of the paper is to prepare a nonporous aluminum oxide membrane which will be used as a micro/Nano filter in biomedical micro hydraulic device or system by using piezoelectric material actuator acting as a vibroactive member to excite the aluminum oxide membrane. In order to identify the aluminum oxide membrane could be used as active nano filter for filtration of any kind of particle membrane was excited at frequency range of 5 kHz to 100 kHz and the distribution of vibration on the membrane was presented in the paper. On the other hand, it is shown that this type of membrane could be used as a particle separation of fluid separation in the micro hydraulic devices in biomedical. Analysis of transportation of bioparticles through the membrane filter were analyzed using developed coherent optics principles.

LIRIC (laser induced refractive index change) employs femtosecond laser pulses to inscribe local refractive index (RI) changes in corneal tissue via multi-photon absorption. Using a near-infrared wavelength (810 nm) offers a decreased risk of photochemical damage to the retina for clinical applications of LIRIC for refractive vision correction compared to shorter wavelengths that have been used, however the multi-photon order is higher, limiting the amount of RI change achievable before damage. Excised rabbit corneal tissue samples were soaked in 0.25% and 0.50% solutions of either riboflavin or sodium fluorescein, photosensitizers with large two-photon absorption cross-sections at 810 nm that are biologically compatible and safe for use in the cornea. Near-infrared LIRIC was performed on these doped cornea samples as well as on undoped samples using two different laser sources: a Ytterbium fiber laser at 5 MHz and a Ti:Sapphire oscillator at 80 MHz, with average powers in the laser focal volume up to 140 mW and 950 mW, respectively. For the native cornea, similar RI change was induced at both repetition rates for a scanning speed of 10 mm/s (5 MHz) and 20 mm/s (80 MHz). Doping the cornea with either sodium fluorescein or riboflavin allowed for a 10x increase in scanning speed at 5 MHz and a 5x increase in scanning speed at 80 MHz while producing a similar magnitude of RI change to that of the native cornea. With all samples, using the lower repetition rate allowed for a large reduction in the average power needed to induce a similar amount of RI change.

Ultrafast laser ablation may provide treatment for vocal fold (VF) scarring. Optical properties of VF must be known prior to clinical implementation to select appropriate laser surgery conditions. We present scattering lengths and ablation thresholds of human and canine tissues measured using an experimental approach which involves an image-guided, laser-ablation based method. We study effects of tissue storage and cumulative pulse overlap on scattering properties and ablation thresholds. We perform deep tissue ablation using moderate numerical apertures and multiple laser operating conditions to imitate predicted surgical implementation. Results provide guidelines for clinical implementation towards VF restoration therapy.

Organized cellular alignment is critical for variety of biological phenomenon as well as necessary for several tissue engineering applications. Although a variety of methods have been used to control cellular alignment in 2D, recapitulating the organized 3D cellular alignment found within native tissues remains a challenge. In this study, we present a new method to align cells in localized user-defined orientations using femtosecond (fs) laser enabled hydrogel densification. Fs laser direct writing was used to induce densification within partially crosslinked gelatin methacrylate (GelMA) hydrogel. Densified line patterns were used to preferential align variety of cells such as mouse 10T1/2s fibroblasts and IDG-SW3 osteocytes, and human HUVECs and hiPSC-derived MSCs. Cellular alignment as a function of cell-culture time, line spacing, and modification-depth were characterized. As compared to the current technology, this method can be applied to any photocrosslinkable hydrogel, as it does not require specialized chemical or physical modifications or any external guidance cues. Additionally, densification can be introduced during active cell culture providing temporal flexibility in experimental design. This method can be potentially used for the creation of organized engineered tissues.

Cell fusion is an important process that occurs during normal development, as well as during cancer growth and metastasis. Using specific gold nanoparticles and intense femtosecond laser pulses to induce plasmonic cell fusion, we study the reorganization of the actin network within the fused cells, network that is known to be highly involved in epithelial-mesenchymal transitions. Time-lapse confocal microscopy of the fused cells showed large-scale actin networks within the giant hybrid cells, with unique reorganization dynamics that preserve the original filament orientation of original cells.

The black-brown pigment eumelanin acts as a vital barrier to the harmful UV radiation. With an ingenious ability to effectively dissipate 99.9% of the incoming UV energy to the heat within few picoseconds, eumelanin serves as a natural photo-protectant. To unravel the nature of the energy dissipation we study the eumelanin pigment and its major building block using ultrafast broadband transient absorption spectroscopy. The excited state decay was found to be fluence independent for all excitation energies, suggesting that electronic excitations are also spatially localized. The short excited state lifetime – on the order of a few picoseconds – leads to a suggestion that the energy is dissipated through excited-state intramolecular proton transfer, which we examined via comparison with pH-dependent TA spectroscopy of the DHICA and related building blocks.

We present a complete study, together with a careful experimental metrology, on single shot ablation of fused silica and sapphire induced by femtosecond pulses (<200-fs) ranging from 258 nm to 2000 nm. The wavelength-dependent fluence ablation threshold, increasing up to near infrared and saturating on the infrared range, allows to infer the role of drastically changing photoionization rates following Keldysh formalism. While it is also expected an energy deposition primarily relying on electron heating and avalanche in the infrared, we find deep craters are more efficiently obtained near the ablation threshold but the difference rapidly vanishes at increased fluences.

We investigate the possibilities offered by tightly focused ultrashort laser pulses at 2-µm wavelength for modifying the bulk of silicon. Results show that the lower the pulse duration, the lower the probability to modify the material, in good agreement with nonlinear propagation simulations. By evaluating the influence of several laser parameters, we have found ideal conditions for successfully initiating modifications systematically in the bulk of silicon with ultrashort laser pulses through plane surface for the first time. This result holds promises for contactless monolithic integration of three-dimensional architectures inside silicon.

Multilayer dielectric materials are used to tailor the optical properties of interfaces. While laser damage resistant coatings have been carefully investigated, the potential of laser modifications in staked alternating dielectric layers has not been explored thoroughly. Here, we investigate the effects of ultrafast laser exposure on alternating stacks of SiO2 and SiNx dielectric films deposited on a substrate, focusing primarily on non-ablative exposure and on its effect on the layer intermixing and the resultant change of material properties. We are especially interested on the experimental characterization of the materials after femtosecond laser exposure, particularly on the post-exposure material structure.

Filamentation of femtosecond laser pulses at 800 nm provokes many spectacular phenomena like long range propagation, broadband THz generation, pulse self-compression, guided electric discharges and lasing effects. In particular, a coherent forward emission at 391 nm is observed that corresponds to a transition between levels B and X of the singly ionized Nitrogen molecule. Interpretation of this cavity-free air lasing is highly controversial. Several mechanisms like net electronic population inversion, rotational population inversion or Raman-like amplification were proposed but none of them is fully consistent and describes properly the gain properties. We have developed a model of lasing without population inversion in a V scheme arrangement. It is supported by experimental evidence for the long lasting coherent polarizations AX and BX required for such a V scheme. We show that the temporal shape of the lasing emission and its dependence with gas pressure can be well restituted theoretically. In addition, we present new supplementary measurements using consecutive twin femtosecond 800 nm pump pulses. A reduction of the global lasing signal at 391 by a factor ~ 1000 is observed when the gas is pumped with the twin pulses. This spectacular effect is observed over a range of delay between the twin pulses of several ps and can be interpreted in the frame of the V scheme.

Unlike the classical electro-magnetic wave with uniform polarization distribution along the flat wave-front, the light pulses in either laboratory or industry usually have non-vanishing components in the direction of propagation. Therefore, the full description of a generally complex laser pulse should be implemented in multi-dimensional way, for the light in the free space is the combination of a three-dimensional(3D) electric field and a 3D magnetic field in the 3D Euclidean space which is the subspace of the four-dimensional space-time. Here we report on a novel technique for the full-vectorial characterization which includes the spatiotemporal amplitude and phase information as well as the vectorial features of the complex laser pulses. This new measurement capability opens the way to in-depth characterizations and optimizations of the complex laser pulses and ultimately to the study of new phenomena of the interactions between materials and structured ultra-short laser beams.

The performance of industrial ultrafast lasers with average power ranging from 10-1000 Watts depends on their wavelength, pulse duration, total power, and repetition rate. However, variability in laser performance, despite similar characteristics and manufacturing, indicates the current metrics are not enough. Here we introduce the power figure of merit (PFM), to quantify the power that resides within the short pulses as opposed to the background light, or ‘dark energy’ between the pulses. We introduce take advantage of linear sampling using photon counting methods to quantify PFM and demonstrate its use on lasers with PFM ranging from 0.9 to 0.995.

Sonogram encoding is utilized to measure ultrafast optical pulses at 1550 nm. The optical waveform is divided into narrow-bandwidth frequency bins, which are time multiplexed. The recombined single-shot sonogram signal is acquired using high bandwidth electronics and processed to recover the pulse intensity and phase. Measurement of optical pulses with a variety of phase distortions introduced using a pulse shaper or dispersive optical fiber is demonstrated. One sonogram is acquired within less than 1 microsecond, which allows single-shot pulse measurement at a rate of up to 1 MHz. Capabilities and detailed specifications of the method will be presented.

In this work, we investigate non-contact tuning methods to re-align a beam of light in an optical circuit. We show that by combining flexures and femtosecond laser based exposure at low energy pulses, optical elements (a mirror in this case) can be repositioned remotely in a reversible manner, permanently and with unprecedented levels of accuracy down to sub-micro-radian levels. Due to the monolithic nature of these elements and our non-contact tuning approach, they occupy considerably less space and thus offer new possibilities in device miniaturization. Additionally, we show that such repositioning is permanent in nature – meaning – once the device is exposed to the laser and the optimal position is found, it does not fluctuate away from that position.

The recent development of Ultra Short Pulse lasers has widely broadened the range of possibilities of laser material processing. Associated with a proper beam splitting it enables adding to the surface new properties by texturing it. We present here a fully reflective three by three beam splitter compatible with high power up to 300W with 500fs pulses lasers. The process results are presented including the repeatability of the pattern, and the achievable ablation rate. The pattern is 15µm waist gaussian beams with 300µm pitch. Compatibility with scanning system and F-theta lenses, enabling micro-processing throughput improvement, is described.

Laser induced refractive index change (LIRIC) technique has been demonstrated as a non-invasive way to alter optical refractive powers of ophthalmic materials including hydrogel-based contact lenses, exercised corneal tissues and even corneas in vivo, via modifying the refractive index through multiphoton absorption process. In our previous work, blue femtosecond laser pulses at 405 nm with a repetition rate of 80 MHz were focused tightly into the stromal region to achieve refractive corrections in live cats via inscribing phase wrapped structures. In order to improve the efficacy of LIRIC, we here demonstrate that blue femtosecond laser pulses at a lower repetition rate range induce larger amounts of phase change with lower laser powers and higher scan speeds owing to a higher pulse energy density deposition. In comparison to a high repetition rate writing at 80 MHz, higher phase change can be attained at 8.3 MHz at the same average power. Furthermore, one wave of phase change measured at 543 nm was attained in rabbit corneas ex vivo for the first time by inscribing single LIRIC layer at 8.3 MHz with a power of 200 mW and a scan speed of 100 mm/s, corresponding to a refractive index change of 0.025 after the layer thickness was estimated to be 20 μm. Accordingly, the optimum laser repetition rate used in femtosecond micromachining corneas can be determined to be around 8.3 MHz, as arbitrary phase structures can be manufactured by wrapping the phase between 0 and 1 wave.

In this communication, we report on the direct inscription of near-surface waveguides in crystals and polymers for the first time. A Ti-Sapphire femtosecond laser was used to form near-surface waveguides based on a depressed cladding architecture in quartz by placing a cover glass temporarily in optical contact with the surface of the sample during the inscription process. Also, a novel technique based on resonant absorption of polymers in the mid-IR is applied to induce the formation of on-surface waveguides in polymers. As a proof of concept, the near-surface waveguides were used as highly sensitive refractometric sensors.

Astrophotonics is an emerging tool for increasing the angular resolution in ground-based sky observations. Due to the unpolarized nature of celestial light, it is necessary to operate with fully polarization insensitive integrated devices. In this respect, here we show that a thermal annealing after the femtosecond laser writing of waveguides reduces their birefringence of more than order of magnitude, providing integrated circuits whose behaviour is insensitive to the polarization of the input light. As a validation of this technique, we present the successful fabrication of a low-loss integrated device for performing stellar interferometry of up to 8 input beams.

We report on our very recent demonstration of new waveguide Bragg gratings inscribed in a silver-containing oxide phosphate glass. We present the mask-less fabrication of first-order Bragg grating in the red/near-IR range. Based on coupled mode theory, these waveguide Bragg gratings show strong coupling constants, up to 3.9 mm-1 depending of the chosen Bragg grating geometry, which is relevant for applicative perspectives in integrated optics. Detailed description of these silver-sustained waveguide Bragg gratings will be provided, allowing for discussing both limitations and potentialities of the proposed innovative approach for the production of Bragg gratings in such photosensitive glasses.

Femtosecond laser micromachining (FLM) is considered today a key technology for the fabrication of high-quality photonic integrated circuits, especially when a 3D geometry is required. However, when a thermal phase shifter is exploited to reconfigure an FLM device, its operation requires many hundreds of milliwatts. This issue strongly limits the scalability of these circuits. With this work, we present a new FLM fabrication process that takes advantage of thermally insulating microstructures (i.e. trenches and bridge waveguides) to demonstrate low propagation losses (0.29 dB/cm at 1550 nm), along with a power dissipation for a 2π phase shift down to 37 mW.

We present narrowband and high contrast ultrashort pulse written phase shifted fiber Bragg gratings (FBG). The phase shift in the fiber was implemented by overlaying two spectrally slightly differing gratings, resulting in a Moiré grating. They were realized using the phase mask scanning technique, providing a reliable and reproducible inscription process. The different grating periods were implemented by controlling the applied strain on the fiber during inscription which was monitored spectrally. We present the results of single and multiple phase shift gratings with passband bandwidths as low as 4 pm and contrasts as high as 42 dB.

Femtosecond laser irradiation was applied to single-mode optical fiber (SMF450), embedding a filament array through the silica cladding and guiding core cross-section to form chirped Bragg gratings. Unlike the standard plane-shape fiber Bragg grating structures, the filament shape facilitated radiation mode scattering of guided light transversely out of the fiber cladding, while the azimuthal radiation zone was narrowed by the filament geometry, the cylindrical cladding focus, and the photonic stop band design. Chirping of the grating period further provided spectral focusing in the near zone of the fiber, permitting recording of high resolution spectra (~350 pm) over the 400 to 650 nm band with a CCD camera. A comparison of second (Ʌ=364 nm) and fourth-order (Ʌ=728 nm) Bragg gratings is presented. Two-dimensional filament arrays permitted tailoring of photonic bandgap effects to redirect the -1st order grating light into the +1st order, increasing the overall spectrometer efficiency.

We generalize the well-known method of generating nondiffracting beams based on axicons in the near-field using phase modulations with azimuthal dependencies. The enormous benefit of our concept for efficient shaping of nondiffracting beams with arbitrary transverse profiles is shown and optimized processes like cleaving of particularly thin and thick glasses using elliptical Bessel-like beams are discussed.

We present results comparing simultaneous spatial and temporal focusing beams with traditional Gaussian beams during femtosecond laser processing. We establish the importance of accounting for aberrations in refractive focusing elements and present a feedback mechanism for material processing.

An advanced direct imprinting method with low cost, quick, and minimal environmental impact to create a thermally controllable surface pattern using nanosecond and picosecond laser pulses is reported. Patterned micro indents were generated on shape memory alloys (SMA) and aluminum using nanosecond and picosecond laser operating at various wavelengths combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generate pressure pulses up to a few GPA on the surface were focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the surface. Scanning electron microscope (SEM), atomic force microscope (AFM), and optical microscope images show that various patterns were obtained on the surface with high fidelity. Optical profile analysis indicates that the depth of the patterned sample initially increases with the laser energy and later levels off. Our simulations of the laser irradiation process also confirm that high temperature and high pressure (up to 10 GPA) could be generated when laser energy of 2 J/cm2 is used. Experimental data is in good agreement with a theoretical simulation of laser-induced shock wave propagation inside the material. Stress wave closely followed the rise time of the laser pulse to its peak values and initial decay. Ongoing experiments on a different wavelength and confinement medium conditions and recovery ratio (ratio of the depth of cold indent to the depth of the initial indent) will also be presented.

We report on TRUMPF´s industrialized hollow-core-fiber laser-light-cable coupled to the TruMicro ultrafast laser platform. A flexible connection between processing head and laser source offers new opportunities in the design of compact laser processing machines. The compact, light-weight connector at the end of the delivery fiber provides a well defined optical interface close to the processing optics, and spatially eases integration of any laser to the machine, enabling optimum access for fast system maintenance without any need for re-alignments. Constant optical beam parameters are ensured even during dynamical movement of the laser-light-cable and the processing head. TRUMPF offers a complete in-house solution consisting of the ultrafast laser platform with up to 10 m long hollow-core-fiber laser-light-cables. The system further includes monitoring devices, e.g. for mode field and power, fiber protection and a safety circuit.

As an application example of this compact laser system we present further progress on glass welding. Ultrashort laser pulses enable local bulk modifications in glass as well as controlled melting via heat accumulation. Improved glass welding using optimized energy modulation of successive laser pulses from our advanced TruMicro Series 2000 platform are discussed. The approach for joining brittle materials provides long-term stable and gas-tight joints.

We have demonstrated a widely-tunable femtosecond fiber source between 770-1180 nm enabled by self-phase modulation, and the wide spectral coverage is suitable for most of two-photon fluorescence microscopy applications. Based on femtosecond Yb:fiber laser, we also compared spectral broadening in different dispersion regimes using different photonic crystal fibers. We managed to maximize the self-phase modulated feature from the broadened spectra while avoiding unwanted nonlinear temporal trapping. The optimization of fiber selection and laser input conditions led to a wide tunability down to below 800nm region, which is the most commonly used two-photon excitation wavelength for many intrinsic fluorescent labels in biological tissues. We believe this fiber-based femtosecond source can be a relatively cost-effective and robust solution for most of two-photon fluorescence microscopy applications.

We report on the CEP stabilization of a nonlinearly compressed Yb-doped fiber amplifier system delivering 75 μJ, 60 fs-long pulses at 100 kHz repetition rate. The CEP is passively stabilized via DFG in a home-made front-end and preserved in the amplification chain using a fast feedback loop. A CEP noise of only 320 mrad is measured single shot, every shot at 100 kHz. This source paves the way for a new generation of high repletion rate HHG driver.

Integrated modulators of optical phase or intensity are essential elements to reconfigure dynamically the operation of a complex waveguide circuit, or to achieve convenient optical switching within a fiber network. Thermo-optic effects are commonly exploited to achieve dynamic phase modulation in glass-based devices, since nonlinear optical effects are weak in such substrates. Thermo-optic modulators rely on electric resistive heaters patterned on top of the waveguides: they are reliable and easy to fabricate, but they suffer from slow response, dictated by the thermal diffusion dynamics. On the other hand, optically-coupled microstructures in glass, driven at their mechanical resonances, may provide interesting possibilities to achieve modulation of the optical signals in the kilohertz range and higher. In this work, we demonstrate integrated-optics intensity modulators based on micro-cantilevers with resonant oscillation frequencies in the tens-of-kilohertz range. The mechanical structures are realized in alumino-borosilicate glass substrate by water-assisted femtosecond-laser ablation. With the same femtosecond laser an optical waveguide is inscribed within the oscillating beam; a waveguide also continues in the substrate beyond the cantilever's tip. Since the entire device, with all its optical and mechanical parts, is realized in a single fabrication process, relative alignment is guaranteed. If the cantilever is at rest, light propagating in the internal waveguide yields maximum coupling to the remaining part of the waveguide. When the device is excited at resonance by means of a piezo-electric actuator, the cantilever oscillation produces periodical variations of the coupling efficiency, with an observed contrast higher than 10 dB.

We report on an all-laser based fabrication process for optical elements made of glass. Two laser systems, namely a 1030 nm ultrashort pulsed and a CO₂ laser are applied. Firstly, a femtosecond laser is used to precisely ablate the glass substrate layer-wise, forming the designed geometry. This ablation process is investigated in detail, focusing on the influence of the pulse distance as well as the laser fluence on the ablation depth, ablation efficiency and the surface roughness. It is found that the ablation depth decrease with increasing pulse distance while the ablation efficiency shows a maximum in the middle of the pulse distance regime for all investigated fluences. Contrary to these results, no significant influence on the surface roughness is observed. The well developed ultrashort pulsed laser ablation process is demonstrated for the fabrication of optical preforms such as cone-shaped (axicon), spherical and cylindrical lenses. In order to meet high surface quality requirements, inevitable stipulated for optical use, the surface roughness of the generated elements has to be reduced by CO₂ laser polishing. To demonstrate the subsequent surface finishing process, a complex optic geometry i.e. an axicon array consisting of 37 individual axicons is fabricated within 23 minutes while the polishing shows a reduction of the surface roughness from 0.36 μm to 48 nm. For a detailed investigation of the fabricated optic, the axicon array is mounted into the ultrashort pulsed laser machine. Several sub-Bessel beams exhibiting the typical zeroth-order Bessel beam intensity distribution are observed, in turn confirming the applied manufacturing process to be well applicable for the fabrication of complex optic geometries. Cross-sections of the quasi-Bessel beam at the axicon in the middle of the array in both, x- and y-direction, show an almost identical intensity profile, indicating the high contour accuracy of the axicon. The diameter of the sub-beam is measured to be 9.5 μm (FWHM) and the Bessel range in propagation direction amounts to 8.0 mm (FWHM).

Based on a simplified ablation model using only two parameters to describe a material, we have developed a numerical method of inverse computation to obtain the most judicious laser configurations for a given depth of ablation in a given material. The calculations are carried out for more than one million configurations (pulse energy, pulse rate, spot diameter, scan speed, …). The results are stored and analyzed on demand via multiple input tables. The digital tools are validated for stainless steel, and ablation results will also be presented for other metals (aluminum, titanium) or composite materials (CFRP).

Intraocular lenses (IOLs) are widely used to treat cataracts and restore vision, however, the accuracy of manufacture and surgical implantation of IOLs is subject to some limitations. Femtosecond laser micromachining relies on tightly focused, ultrashort laser pulses to locally modify the properties of bulk materials, and has been recently applied in the field of vision correction. In this study, multi-layer dense line patterns were inscribed into Tecnis IOLs using a femtosecond laser operating at 8.3 MHz at a wavelength of 405 nm. Below the damage threshold, uniform phase changes could be obtained within each pattern, and its magnitude increased nonlinearly with laser power. To explore the mechanisms underlying the refractive index (RI) changes, microstructural changes of the phase pattern were quantified by confocal micro-Raman spectroscopy using sectioned IOLs. A significant decrease of the integral intensity of 2988 cm^-1 band (v(C-H)) that confined in the written layer was observed from the lateral scan profile of IOL cross section. We posit that the positive RI changes in IOLs were likely associated with localized photochemical depolymerization, which includes broken of chemical bonds and diffusion of molecular fragments. These findings enhance our understanding of femtosecond micromachining as a new method to customize high visual-quality IOLs.

The knowledge of the ionization of water is essential in different fields such as Biology and Atomic Physics. Basic reactions involving this molecule are crucial to understand the interaction between radiation and the biological tissue because living cells are composed mostly by water. Therefore, we study theoretically the laser-assisted photoionization of water molecules by attopulses in the streaking regime by means of a Coulomb-Volkov model. We analyze reactions initiated by an extreme ultraviolet single attosecond pulse assisted by a near-infrared laser. The initial molecular wavefunctions are described by using the Moccia’s monocentric wavefunctions whereas the final state wavefunctions are given by the separable Coulomb-Volkov type wavefunctions. We obtain analytical expressions for the observables of interest. We calculate photoelectron spectra as a function of the delay between the attopulse and the assistant laser field for water molecules. Several polarization configurations of pulses and assistant laser are considered. Particularly, we focus on the conditions where asymmetries are generated in the observables and we examine those under which these asymmetries could be enhanced and/or diminished leading to a directional selectivity of the photoelectron emission. Consequently, we hope our work promotes progress on the control of the chemical reactivity of water as this could be useful in many domains of radiobiology and medical physics. Finally, we expect these studies contribute to the improvement of attopulses and assistant laser technologies as well as to the development of new polarization and delay control experiments.