We propose a versatile pulse shaper using a 2D spatial light modulator to perform simultaneous and independent control of the spectral amplitude and phase of a fiber-based supercontinuum source. Different spectral optimizations will be demonstrated in a multimodal optical imaging system, combining optical coherence tomography (OCT), multiphoton microscopy (MPM), and nonlinear Raman imaging. This custom pulse shaper enables fast wavelength-tunable excitation for Raman spectroscopy with high spectral resolution. Single beam simultaneous MPM and OCT can also be enabled by compressing a selected multiphoton excitation band while chirping the whole spectrum for ultra-high-resolution OCT.

In this presentation, we will show the latest advances in the context of the European H2020 Horizon project LaserImplant. Functionalized surfaces by ultrashort laser texturing were developed with the aim of improving the biocompatibility and efficiency of medical screws. Both osteoblast cell repellent surfaces as well as surfaces promoting osteogenesis were studied and characterized by bone cells’ growth and wettability tests. Beam delivery strategies were anticipated for future industrial requirements. Compromises had to be found to implement different textures in one unique solution. Targeted processing times as well as quality robustness were at stake for complex cylindrical shapes with multiple dimensions. Upscaling experiments put in evidence thermal effects due to energy deposition acceleration. Solutions were finally found to overcome speed limitations by selecting dedicated optical systems together with adapted synchronized processes.

We are investigating ways to exploit the significant advantages picosecond pulsed lasers can provide for high precision, minimally invasive surgery over conventional surgical tools. Combining a range of characterisation techniques in clinically relevant tissue models, such as high-speed imaging, surface profilometry and histopathological analysis of the laser ablated regions, allows us to control undesirable effects, such as cavitation bubbles, and optimise the ultimate precision achievable. Furthermore, by developing novel, hollow-core optical fibres we have overcome limits imposed by optical damage and non-linear effects delivering peak powers not possible with conventional optical fibres and significantly outperforming state-of-art technologies for laser delivery in surgery. The fundamentals of the laser tissue interactions will be discussed and also our current work on developing the novel optical technologies necessary to move towards devices that could be used in the clinic.

In dentistry, implantation failures of dental implants are primarily due to a poor osteointegration, and complications induced by peri-implantitis. For that reason, a strong bacteria resistance, a fast osseointegration, and a good adhesion of the gingival tissues to the implant surface are essential for a successful implantation, comfort and safety of the patient in question. We showcase that a fine-tuning of ultrafast laser-induced surface structures would improve the implantation successful rate by rendering dental implant surfaces with triple-functionality: repellent for saliva bacteria for the upper part of the dental implant (which is exposed to mouth water, attractive to gingival fibroblasts for the middle part of the dental implant (which interfaces with gum tissue) to prevent bacteria penetration, and fast osseointegration for the lower part of the dental implant which is located in the jaw bone environment.

Artificial fusion between specific cells is a valuable tool for studying various key aspects in biology and biomedicine, either for basic scientific research or for clinically relevant therapeutic applications. A recently developed technique for artificial induction of cell fusion, termed plasmonic cell fusion, uses femtosecond laser pulses for resonant irradiation of specific cells that were targeted by specific gold nanoparticles. The pulse-particle interactions locally destabilize the cell membranes, leading to an efficient, widespread fusion only between the targeted cells. The talk will present a summary of the various experiments and demonstrations of plasmonic cell fusion for basic research and for addressing important clinical challenges, including stimulating of an immune response by fusing together malignant and immune-system cells, treating muscle injuries by fusing together fibroblasts and skeletal muscle cells, and more.

Bioprinting is a rapidly expanding additive manufacturing process, for the development of complex biostructures such as tissue-like structures, able to imitate native tissue functions. Among the most commonly used bioprinting techniques, Laser Induced Forward Transfer (LIFT) offers the highest degree of spatial resolution (minimum feature of <10 μm) and post-printing cell viability while it has also been used for the immobilization of biomaterials on a variety of substrates. Furthermore, this study will present the control of the depth of cell deposition within the ECM by tuning the laser printing parameters and the organoid formation of the laser printed cells, already from Day 1 after bioprinting. Finally, the application of LIFT technique in Organ on Chip applications will be presented.

In this invited talk, we will review the research done at Polytechnique Montreal on the modeling and applications of plasmonic enhanced ultrafast laser nanocavitation and nanosurgery in living cells. . Potential applications in nanomedicine and ophthalmology such as cell transfection, neuron stimulation and in vivo gene delivery into retina cells are presented. Results on plasmonic enhanced ultrafast laser triggered Anticancer Drug Delivery with lipid nanoparticles will be discussed.

Nonlinear optical propagation in multi-mode fibers is used a computational tool for machine learning applications, We demonstrate that optimization of few parameters leads to a performance level achievable only with very large digitally implemented neural networks.

We report supercontinuum generation and pulse compression in two stacked multipass cells based on dielectric mirrors. The 230 fs pulses at 1 MHz containing 12 μJ were compressed by factor 33 down to 7 fs, corresponding to 1.0 GW peak power and overall transmission of 84 %. The source is particularly interesting for such applications as time-resolved ARPES, photoemission electron microscopy, and nonlinear spectroscopy.

Nonlinear spectral broadening based on self-phase modulation followed by pulse compression is a well-established approach in high average power and ultrashort pulse duration systems. One exemplary implementation uses free space propagation through a nonlinear medium (solid or gas) in a multipass arrangement. Scaling this method beyond the 10 mJ-range is mainly limited by three detrimental effects: excessive self-focusing, laser-induced mirror damage and gas ionization. Dominantly multipass cells are realized with a Herriott-cell arrangement comprising two concave mirrors. Here we suggest a different approach, a concave-convex geometry. No foci are present in these multi-pass cells, mitigating the ionization problem. The decreased intensity permits the arrangement's folding, reducing the required footprint for practical applications.

The ability to cut heat-sensitive polymers with minimum kerf width and low HAZ, and at high speeds, is critical for many industrial applications. In this work, we investigate the benefits of using high-power femtosecond UV lasers in processing polymer materials, which are commonly used for OLED displays and flexible circuit boards manufacturing. In particular, we present a study on the impact of the processing conditions on the throughput and quality of laser cutting of polyimide (PI), polyethylene terephthalate (PET) and polytetrafluoroethylene (PTFE) polymers as well as OLED display multi-layer polymer film stacks.

This presentation was prepared for SPIE LASE 2023.

The Bessel beam is a versatile tool for several applications thanks to its propagation-invariant spatial profile. We demonstrate for the first time the possibility of generating high aspect ratio micro-pillars with an ultrafast first-order Bessel beam on a sapphire sample. A single pulse expels matter shaped as a high-aspect ratio pillar. The height can exceed 10 µm with a typical diameter of 500 nm. Importantly, our method does not require milling or deposition of new material. The process is also fast since it requires only a single pulse, and there is no need for sample post-processing.

The peak intensity of an ultrafast laser pulse focused inside a dielectric material can be sufficiently high to drive the nonlinear absorption of the laser light. This deposition of energy in the focal region can result in a localised material modification. This modification can in turn manifest itself through changes to the chemical etch rate and / or refractive index. Using these manifestations, it is possible to manufacture three-dimensional photonic components, such as optical waveguides. In this talk, I will discuss how ultrafast laser inscription can be used to manufacture three-dimensional photonic components for the manipulation of spatial modes.

In this contribution, we compare the etching behaviour of fused silica machined with a femtosecond laser at three different wavelengths. We use a high-power YAG laser to generate 450 fs-long pulses at the first (1030 nm) and third (343 nm) harmonic. We demonstrate how these new machining techniques can be used to improve the laser-assisted etching in fused silica not only in terms of etching speed, but also in terms of minimal feature size and surface roughness. Processing speeds of several 100 mm/s become possible due to the new regime using fs-UV light.

We exploit femtosecond laser writing to create an alkali-metal vapor cell, the core component of an atomic sensor. This laser-written vapor-cell (LWVC) technology allows arbitrarily-shaped 3D geometries and holds the potential for integration with photonic structures and optical components. The fabrication steps of a vapor cell in silica glass will be shown and the possibility of its integration with GRN lenses, as an example of miniaturized optical component, will be investigated. We successfully use this device for sub-Doppler saturated absorption spectroscopy and single beam optical magnetometry to validate its functioning.

Femtosecond laser written (FLW) reconfigurable photonic integrated circuits are attracting large attention from many applications thanks to their unique features. However, in these devices the frequency response of thermo-optic phase shifters is currently limited to the Hz range, hindering the diffusion of FLW circuits in different fields. Here, we present a thermally-reconfigurable Mach-Zehnder interferometer inscribed just a few micrometers below the surface of a fused silica substrate. The interferometer design, purposely optimized by finite element simulations, allows for switching time lower than 200 μs, phase modulation of the optical signal at kHz frequency and limited impact on the power dissipation.

We report the first demonstration of Volume Bragg grating (VBG) by femtosecond laser writing in silver-containing glasses using type A high refractive index modification supported by the laser-inscribed silver clusters. We present a comparative study between different approaches to achieve high diffraction efficiency in VBG for the VIS-NIR range. The first approach involves direct writing, line-by-line, and plane-after-plane, of the entire structure with a Gaussian beam as well as a Bessel beam. The second method will be considered with the inscription under a periodic phase mask. This work opens the avenue for femtosecond writing VBG with high throughputs compatible for industrialisation

Micromachining of transparent materials with high-power lasers demands new approaches to utilize most of the laser power without reduction of the quality. The usually exploited Gaussian beams become absolute when specific beams can be utilized to do the set task. For instance, the Bessel beams can be used to drill very high aspect ratio holes with a single laser pulse, which increases the speed of manufacturing by many orders. In our research, we have even more versatility in the beam shapes as we use the beam shaping techniques which withstand high-power laser pulses. Therefore, higher-order, vectorial Bessel beams, and flattop beams were used to micromachine transparent materials and results will be shown.

Riblets manufacturing allow the reduction of flight consumption of 2 to 3% but requires both high precision in texturing and high processing speed to engrave large surfaces. An innovative combination of high-speed (100 kHz) and high energy (3 mJ) femtosecond laser with a beam division up to 9 spots, and a square shaping of the spots is presented using multi plane light conversion (MPLC) beam shaping technique for both the beam division and the square beam forming, with homogeneity of spots better than 95%. Texturing tests will be presented and compared to achievements using non shaped Gaussian laser beams.

Nanoscale objects, such as nanowires and thin films, possess exceptional physical properties. However, their desirable characteristics are intrinsically coupled to their small size and solitary nature and are generally challenging to harness in conventional monolithic solids. Metamaterials go beyond classical material design approaches and are structured from building blocks with specifically designed spatial architectures, such as lattice-truss frameworks. These architectures grant them many conventionally inaccessible properties. Two-photon polymerization 3D-printing facilitates the miniaturization of metamaterial architectures down to the nanoscale, enabling them to harness material size-effects in their constituent solids, including extreme mechanical strength. Herein, design concepts, synthesis approaches and performance of nanoarchitected materials and mechanical metamaterials are presented, offering a pathway to exploit beneficial nano-properties in 3D volumes.

Femtosecond laser processing is used for writing waveguides with controllable cross-section in glass substrates. Fabricating in the heating regime with high scanning speed, we find that accurate control of the spherical aberration in the laser focus, implemented with a liquid crystal spatial light modulator, is crucial for generating precise modifications at high resolution. These laser written modifications could then be nested tightly together in a 2D multiscan approach to form waveguides with carefully controlled cross-section. We furthermore show how the cross-section can then be modified along the length of the waveguide to create a variety of mode converters.

We report on processing crystalline silicon with ultrashort laser pulses. Careful analysis of the nonlinear interaction process allows to inscribe waveguides in a longitudinal writing geometry. The origin of the waveguiding structures is due to a disturbed crystal structure with a cross section closely matching the focal size of the inscribing laser beam. Thermal annealing studies confirm that the strain from these defects and dislocations is responsible for the refractive index change. Improved control of nonlinear energy deposition paves the way to realize the transversal writing regime. Other applications like welding or localized amorphization will be highlighted as well.

Tellurium (Te), an elemental van der Waals material with a p-type narrow bandgap is attractive for its strong photo-response, piezoelectric, and thermoelectric properties. Its oxide glassy form (TeO2) combines a wide optical transmission window with a high refractive index and nonlinear optical properties. Interestingly, as we showed in a previous study, upon femtosecond (fs) laser exposure, the glassy form of tellurite evolves into a functional Te/TeO2-based glass composite, as a consequence of elemental decomposition and crystallization of Te. By scanning the fs-laser over the tellurite glass, perfect ohmic contacts can be formed between arbitrary locations. Furthermore, we show that the Te micro-wires can have a highly reproducible and sensitive photo response from the near UV to the visible spectrum, and a robust reversible photo-switching behavior. The fs-laser direct-write glass/metalloid composite shows promising performance for novel photodetectors with an arbitrary design.

This presentation was prepared for SPIE LASE 2023.

We report on multi-100W ultrafast laser sources based on industrialized components which deliver pulse energies starting from sub-mJ to well exceeding 200mJ. These sources are based on ytterbium-doped laser media which intrinsically have very high efficiencies and therefore allow for stable operation at high average powers but are limited due to the supported bandwidth to some 100fs pulse durations. The presented setups compress this type of pulses to well below 50fs with a single SPM-based stage which adds approximately an order of magnitude in pulsed peak power. Adding a second stage allows for even shorter pulses in the few-cycle regime where even the carrier-envelope phase of the pulses is of relevance and consequently has to be characterized and stabilized.

The French 4F consortium (10 partners, laboratories, technological centers, and laser companies) has developed new all-solid and low-cost fibers. The Ytterbium active fiber are produced for optimum laser performances, such as a Mode Field Diameter greater than 30 μm, Polarization Extinction Ratio greater than 15 dB, bending radius limited to a relatively small diameter (about 20cm). The fiber allows a laser operation exceeding 200 W. Microstructured, hollow core fibers are key to high power beam delivery. Beam delivery devices have been developed for high average power (up to 100W), high energy and with excellent beam quality.

We report on a new concept of credit card-sized free-space Yb:KYW laser cavity designed to generate femtosecond pulses at a GHz repetition-rate. Optical components are assembled directly, without mounts, inside slots fabricated by direct laser writing and chemical etching in a rigid fused-silica substrate, ensuring a very precise pre-alignment. The alignment fine-tuning is provided by one-time actuators fabricated within the glass substrate itself, which are remotely activated using femtosecond laser-induced micro-deformation in the bulk, ensuring a stable and lasting lasing operation. As a proof-of-concept, efficient CW and SESAM-enabled passive mode-locking regimes are demonstrated.

We report on a 300-W industrial femtosecond laser with ultrashort compressed pulses. Pulse compression is performed within a gas-filled multi-pass cell and results in about 50fs pulses at an energy of 600µJ. Long terms tests of more than 10 days revealed excellent long term and short-term stability of the system. Relevant laser and system parameters are continuously monitored and logged thus enabling to correlate these parameters with results obtained when using this laser for scientific experiments or machining applications. The perspectives to even shorter pulses and higher power and pulse energies will be discussed.

We introduce a new optical component – rotated chirped volume Bragg grating (r-CBG) – with a compact footprint capable of spatially resolving the spectrum without the need for subsequent free-space propagation. Unlike conventional chirped Bragg gratings in which both the length and width of the device increase with operation bandwidth, the link between the length and width of r-CBG is severed, leading to a significantly reduced footprint for the same bandwidth. We fabricate and characterize such a device of total volume 25x6x6 mm3 in multiple spectral windows, we study their spectral resolution, and via FROG measurements we confirm that a pair of cascaded r-CBGs can resolve and combine the spectrum of a 100-fs pulse.