Piotr Wasylczyk

University of Warsaw | UW · Institute of Experimental Physics

The ability to grip and handle small objects, from sub‐millimeter electronic components to single‐micrometer living cells, is vital for numerous ever‐shrinking technologies. Mechanical grippers, powered by electric, pneumatic, hydraulic or piezoelectric servos, are well suited for the job at larger scales, but their complexity and need for force tr...

With continuous miniaturization of many technologies, robotics seems to be lagging behind. While the semiconductor technologies operate confidently at the nanometer scale and micro-mechanics of simple structures (MEMS) in micrometers, autonomous devices are struggling to break the centimeter barrier and have hardly colonized smaller scales. One way...

Optical vortex beams carry orbital angular momentum and thus exert torque on illuminated objects. A dielectric microtool–a microbarbell–is used in two-laser optical tweezers to measure the torque of a focused optical vortex. The tool was either freely rotating due to the applied torque or set into oscillations by the counteracting force. Four diffe...

In light science and applications, equally important roles are played by efficient light emitters/detectors and by the optical elements responsible for light extraction and delivery. The latter should be simple, cost effective, broadband, versatile and compatible with other components of widely desired micro-optical systems. Ideally, they should al...

The photo-mechanical response of liquid crystal polymer networks (LCNs) can be used to directly convert light energy into different forms of mechanical energy. In this study, we demonstrate how a traveling deformation, induced in a liquid crystal polymer ring by a spatially modulated laser beam, can be used to drive the ring (the rotor) to rotate a...

As the 3D quantitative phase imaging (QPI) methods mature, their further development calls for reliable tools and methods to characterize and compare their metrological parameters. We use refractive index engineering during two-photon laser photolithography to fabricate a life-scale phantom of a biological cell with internal structures that mimic o...

Optical vortex beams carry orbital angular momentum and thus exert torque on illuminated objects. A dielectric microtool - a microbarbell - is used in a two-laser optical tweezers to measure the torque of a focused optical vortex. The tool was either freely rotating due to the applied torque or set into oscillations by the counteracting force. Four...

Front Cover: In article number 1900279, Piotr Wasylczyk and co‐workers demonstrate a light‐powered, soft snail robot capable of adhesive locomotion. The traveling deformation used for the robot propulsion is generated by photo‐mechanical response in a liquid crystal elastomer (LCE) continuous actuator. Crawling on various surfaces and in many confi...

Crawling by means of the traveling deformation of a soft body is a widespread mode of locomotion in nature—animals across scales, from microscopic nematodes to earthworms to gastropods, use it to move around challenging terrestrial environments. Snails, in particular, use mucus—a slippery, aqueous secretion—to enhance the interaction between their...

Safe interactions between humans and robots require the robotic arms and/or tools to recognize and react to the surrounding environment via pressure sensing. With small-scale surgical interventions in mind, we have developed a flexible skin with tens of pressure sensing elements, designed to cover a 5mm diameter tool. The prototype uses only biocom...

Just like nanometer-scale conductive paths in an electronic chip at some point end up connected to macroscopic wires of the printed circuit board, photonic integrated circuits often need light in/out coupling from/to external devices, such as light sources or detectors. In the optical domain, these connections are challenging due to the scale misma...

Young researchers often encounter questions, problems and hurdles at the early stages of their careers that relate to areas, particularly outside their core subject. These may span from selecting the research topic and methodology to publishing strategies and identifying the position of audiovisual translation research in a wider framework of the f...

Manipulation of micro- and nano-sized objects with optical tweezers is a well-established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool operated with holographi...

Light‐controlled soft microrobotics technologies can bridge the gap between microrobotics and polymeric artificial muscles. In article number 1703554, Hao Zeng, Arri Priimagi, and co‐workers highlight recent progress in photomobile devices based on liquid‐crystal elastomers, such as walkers, swimmers, and oscillators. Self‐regulated actuation is pr...

Manipulation of micro- and nano-sized objects with optical tweezers is a well established, albeit still evolving technique. While many objects can be trapped directly with focused laser beam(s), for some applications indirect manipulation with tweezers-operated tools is preferred. We introduce a simple, versatile micro-tool operated with holographi...

Prototyping of fiber-coupled integrated photonic devices requires robust and reliable way of docking optical fibers to other structures, often with sub-micron accuracy. We have developed an optical fiber micro-connector 3D-printed with Direct Laser Writing on a planar substrate. The connector provides fiber core precision positioning better than 12...

We demonstrate that a stochastic optimization algorithm with a properly chosen, weighted fitness function, following a global variation of parameters upon each step can be used to effectively design reflective polarizing optical elements. Two sub-wavelength metallic metasurfaces, corresponding to broadband half- and quarter-waveplates are demonstra...

A versatile, laser-projector-based method is demonstrated for programming alignment patterns into monolithic films of liquid crystal polymer networks. Complex images can be photopatterned into the polymer films with sub-100 µm resolution, using relatively short exposure times. The method is further used to devise both photochemically and phototherm...

With constant progress of nano- and microfabrication technologies, photolithography in particular, a number of sub-wavelength metallic structures have been demonstrated that can be used to manipulate light polarization. Numerical simulations of light propagation hint that helical twisted bands can have interesting polarization properties. We use th...

We design, optimize and fabricate an all-dielectric photonic structure, having a significant, polarization-independent asymmetry in light transmission for opposite incident wave directions. The device, consisting of a dielectric Bragg mirror topped with a regular grid of micrometer-sized pillars, acting as a diffraction grating, is potentially scal...

For decades, roboticists have focused their efforts on rigid systems that enable programmable, automated action, and sophisticated control with maximal movement precision and speed. Meanwhile, material scientists have sought compounds and fabrication strategies to devise polymeric actuators that are small, soft, adaptive, and stimuli-responsive...

Iris is a biological tissue that can change the pupil size to stabilize light transmission into the eye. In article number 1701814, Hao Zeng, Arri Priimagi and co-workers report an artificial iris made of radially photo-aligned liquid crystal elastomer. This soft device is capable of self-regulating its aperture size in response to changing inciden...

Liquid crystal elastomers are among the best candidates for artificial muscles, and the mate­rials of choice when constructing microscale robotic systems. Recently, significant efforts are dedicated to designing stimuli­responsive actuators that can reproduce the shape­change of soft bodies of animals by means of proper external energy source. Howe...

The iris, found in many animal species, is a biological tissue that can change the aperture (pupil) size to regulate light transmission into the eye in response to varying illumination conditions. The self-regulation of the eye lies behind its autofocusing ability and large dynamic range, rendering it the ultimate “imaging device” and a continuous...

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is nece...

The first study of modified human remains using an electron microscope was carried out at the end of the 1950 and in 1979 the first result of the study involving a scanning electron microscope (SEM) was published for the first time. The study was mainly focused on the structure of tissues and cells. With the help of this technique cell and tissue e...

With proper alignment of the molecules in liquid crystal elastomer (LCE) films, the material deformation can be engineered. On page 1689, P. Wasylczyk and co-workers show that, upon illumination with laser light, a 15 mm long stripe of LCE soft material curls in a way that mimics the caterpillar body motion. The miniature soft robot can crawl on fl...

Genetic algorithm was applied for optimization of dispersion properties in semiconductor Bragg reflectors for applications in femtosecond lasers. Broadband, large negative group-delay dispersion was achieved in the optimized design: The group-delay dispersion (GDD) as large as \(-3500\,\hbox {fs}^{2}\) was theoretically obtained over a 10-nm bandwi...

Soft robots that can be remotely powered and controlled and mimic locomotion of living species open new perspectives in science and engineering. A natural-scale monolithic caterpillar robot based on an optomechanical liquid crystalline elastomer with patterned molecular alignment is reported. The robot demonstrates different gaits and is capable of...

After earning two advanced degrees, completing three postdocs, working in three countries, and finally reaching the stage when I am setting up my own lab, I realize that three lessons taught by three great mentors have influenced how I think about doing science. These lessons, each of which came at

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers' attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques,...

While animals have access to sugars as energy source, this option is generally not available to artificial machines and robots. Energy delivery is thus the bottleneck for creating independent robots and machines, especially on micro- and nano- meter length scales. We have found a way to produce polymeric nano-structures with local control over the...

We designed and 3D-printed a dielectric structure, exhibiting significant difference in transmittance for the opposite incident wave vectors. Measured asymmetry is polarization-independent and spans over 70 nm in the near infrared (780 nm).

We propose a concept for light polarization management: polarization-dependent diffraction in all-dielectric microstructures. Numerical simulations of light propagation show that with an appropriately configured array of twisted bands, such structures may exhibit zero birefringence and at the same time diffract two circular polarizations with diffe...

On page 3883, H. Zeng, D. S. Wiersma, and co-workers report the first light-powered microscopic artificial walker equipped with a liquid-crystalline elastomer muscle. The walker is fabricated by direct laser writing, is smaller than any known living terrestrial creatures, and is capable of several autonomous locomotions on different surfaces. The s...

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Artificial muscles have been investigated for a few decades, however, all attempts to build a micrometer-sized terrestrial robot have failed due to the huge natural adhesion. The first microscopic artificial walker equipped with liquid crystalline elastomer muscle is reported. The walker is fabricated by direct laser writing, smaller than any known...

We report a method to fabricate polymer microstructures with local control over the molecular orientation. Alignment control is achieved on molecular level in a structure of arbitrary form that can be from 1 to 100 μm in size, by fixing the local boundary conditions with micro-grating patterns. The method makes use of two-photon polymerization (Dir...

We demonstrate a photonic structure, composed of a dielectric quarter-wavelength stack topped with a transmission phase grating, designed to exhibit a significant asymmetry in the near infrared light transmission for waves propagating in opposite directions. The asymmetry, defined as the difference between the intensity transmission coefficients, r...

This paper reports on a successful application of evolutionary computation techniques to the computer aided design of a dedicated highly dispersive mirror which is used in an ultrafast laser. The mirror is a GaAs plate coated with many interleaving layers of GaAs/AlAs and SiO2/Si3N4 layers whose thickness undergo optimization. We report and compare...

The optimized nonuniform growth process was used to achieve spatially dependent reflectivity and dispersions characteristics in a highly dispersive semiconductor mirror. The mirror, together with a semiconductor saturable absorber mirror (SESAM), was used to demonstrate a tunable femtosecond Yb:KYW oscillator. In the passive modelocking regime the...

We present a simple broadband gradient-index antireflective coating, fabricated directly on a single mode telecom fiber tip. A regular array of hemi-ellipsoidal protrusions significantly reduce the Fresnel reflection from the glass-air interface. The parameters of the structure were optimized with numerical simulation for the best performance at an...

Liquid-crystalline elastomers (LCEs) are great candidates for smart artificial materials. On page 2319, D. S. Wiersma, C. Parmeggiani, and co-workers use direct laser writing to fabricate 3D LCE structures with sub-micrometer resolution and maintaining the designed molecular orientation. This technique opens up the road towards 3D microphotonics in...

We present a compact Yb-doped fiber chirped pulse amplification system set in a single pass configuration. The system is capable of delivering 34μJ pulses with 200kHz repetition rate. When seeded with a low average power oscillator, the amplifier optical-to-optical efficiency is as high as 37% and the gain reaches 52dB. Temporal pulse degradation d...

We present a femtosecond, diode-pumped Yb:KYW laser configured with a range of saturable absorber mirrors, both commercially available and state-of-the-art structures. The laser performance is characterized for different output couplers (OC) transmission - for the typically used OC transmission between 0.5-10% the laser power increases with the inc...

We have developed a tunable semiconductor double-chirped mirror with high negative dispersion grown by molecular beam epitaxy. The simplified numerical plane-wave reflection transfer method was applied to design the dispersive mirror structure. The multilayer stack was grown of AlAs/GaAs materials and capped by an SiNx antireflective layer. The gro...

The article outlines a new type of audio description: auteur description, which aims to immerse the blind and partially sighted audience into the story world created by the auteur-director, as presented in the screenplay. Two fi lms: Volver by Pedro Almodóvar and Dzień Świra (The Day of the Wacko) by Marek Koterski, are used to highlight the main f...

Simple diffraction structures having the form of a regular grid of pillars can generate a significant range of hues in white light transmission due to color-dependent diffraction into higher orders. We present the fabrication of such submicrometer scale structures by three dimensional laser two-photon photolithography, results of their optical prop...

High temporal resolution measurements of the output of an Yb:KYW femtosecond laser, recorded immediately after opening the laser cavity, give an insight into the transient laser dynamics. The evolution of the light intensity measured with linear and nonlinear detectors, together with the time-resolved laser spectrum were measured and the process of...

We report on the development of semiconductor double-chirped mirrors with the group delay dispersion of -3,800 ± 100 fs2 in the wavelength range between 1,058 ÷ 1,064 nm and reflectivity of 99.1 %. The simplified plane-wave reflection transfer method was used to design the mirror multilayer stack. The mirror contains an epitaxial AlAs/GaAs structur...

We demonstrate a semiconductor double-chirped mirror consisting of an AlAs/GaAs multilayer stack grown by molecular beam epitaxy. The mirror has a high negative group velocity dispersion of -2450 +/- 100 fs(2) and a reflectivity exceeding 98.9% over the spectral range spanning +/- 4 nm around 1035 nm. When used to compensate the cavity dispersion i...

Many potential applications of ultrashort laser pulses in physics, chemistry, biology, and medicine motivate intensive works in this field. The performance of ultrashort pulsed lasers is determined by the efficient management of the laser cavity dispersion [1]. Multilayer mirrors are often employed to compensate the dispersion of the laser gain mat...

Time evolution of the laser light intensity from a self-starting Yb:KYW femtosecond laser with passive mode-locking is presented. One photon and two photon signal transients have been recorded for a few hundred microseconds after opening the laser cavity, and transition from continuous wave to pulsed operation is observed. The collected data are di...

We report the first demonstration of laser wavelength tuning with a resonant grating in the mid-infrared spectral domain and with Littrow mounting of the grating. We show for a mid-infrared Cr:ZnSe solid-state laser that this tuning technique is much more wavelength selective than prism-based tuning, while inducing significantly lower cavity losses...

In an open competition, students were to determine the mass of a metal cylinder hanging on a spring inside a transparent enclosure. With the time for experiments limited to 24 h due to the unexpectedly large number of participants, a few surprisingly accurate results were submitted, the best of them differing by no more than 0.5% from the true valu...

We report the first demonstration of resonant-grating-based laser wavelength tuning in the mid-infrared spectral domain and with Littrow mounting of the grating. We show for a mid-infrared Cr:ZnSe laser that this tuning technique is much more wavelength selective than prism-based tuning, while inducing very low cavity losses (around 2%), which are...

Two particular instabilities: chaotic behavior and period doubling of the automodulated pulse train of the Ti:Sapphire extended cavity oscillator are observed. Complex temporal evolution of the pulse spectrum within the modulation period is investigated.

An extended cavity Ti:Sapphire oscillator exhibits stable operation for positively chirped pulses, while in the negative chirp regime multiple pulses are present in the cavity. At the border of these regimes automodulations, being an effect of the interplay between population inversion, laser medium polarization and the laser pulse field, appear. T...

We present two configurations of low repetition rate Ti:Sapphire femtosecond oscillators with the Herriott cell. Pulse energies of 50 nJ at 13.6 MHz and 40 nJ at the 5.4 MHz repetition rate were achieved. We discuss Herriott cell design as well as the details of laser construction.

We demonstrate a high repetition rate, single mode fiber-coupled diode pumped, Yb:KYW laser in a four mirror ring cavity configuration and study its performance in soft aperture, Kerr lens mode-locked operation at around 1.04 μm.

We present an efficient, single-diode pumped, prismless Yb:KYW femtosecond laser and study its performance in the soft aperture, Kerr lens mode-locked operation. Practical directions are given to identify the conditions under which high-power, stable mode-locking can be obtained.

Manipulation of quantum interference requires that the system under control remains coherent, avoiding (or at least postponing) the phase randomization that can ensue from coupling to an uncontrolled environment. We show that closed-loop coherent control can be used to mitigate the rate of quantum dephasing in a gas-phase ensemble of potassium dime...