High-Q microcavities: characterization and optomechanical applications

In this thesis we tried to address several important problems in modern photonic research. We developed a novel tool for complex analysis of integrated photonic circuits and components. The technique allows to see the time-response of the studied structures on sub-picosecond scale and even to image the pulse propagation resolving the time-frames on the same scale. We report investigation of direct laser written polymeric photonic components and advances in double layered electron beam lithographically fabricated complex photonic circuits. Then introducing a smart material that is capable of changing the its shape in response to external stimuli, we show the material application in photonics and optomechanics. In a separate chapter we demonstrate a novel micro robotic device that is being several hundred microns in size can be controlled remotely by a laser beam. As presented micro gripper can catch and release different kinds of particles, it is also capable of autonomous action, when that act of gripping is triggered by a color of a target. In the last part we present a principle of optomechanical tuning of photonic components. Although this demonstration is not complete, the main principle, however, is evident

Photonic Microhand with Autonomous Action

Grabbing and holding objects at the microscale is a complex function, even for microscopic living animals. Inspired by the hominid-type hand, a microscopic equivalent able to catch microelements is engineered. This microhand is light sensitive and can be either remotely controlled by optical illumination or can act autonomously and grab small particles on the basis of their optical properties. Since the energy is delivered optically, without the need for wires or batteries, the artificial hand can be shrunk down to the micrometer scale. Soft material is used, in particular, a custom-made liquid-crystal network that is patterned by a photolithographic technique. The elastic reshaping properties of this material allow finger movement, using environmental light as the only energy source. The hand can be either controlled externally (via the light field), or else the conditions in which it autonomously grabs a particle in its vicinity can be created. This microrobot has the unique feature that it can distinguish between particles of different colors and gray levels. The realization of this autonomous hand constitutes a crucial element in the development of microscopic creatures that can perform tasks without human intervention and self-organized automation at the micrometer scale

Information technology in the penitentiary crimes prevention and specific environmental crimes investigation

In recent years, there has been a tendency in the digitalization of all spheres of public life, the introduction of information technology and the use of technical means. At scientific events of various levels, they discuss the importance, necessity and possibility of using certain achievements of information technology. In Russia and other countries of the world, exhibitions of technical means, security means are annually held (Sfitex, Securexpo, Interpolitech, etc.) where one can witness achievements in this area. Naturally, the results of technological advances began to be actively used in the activities of law enforcement agencies, including the prevention of penitentiary crimes. This article is devoted to the study of use of information technology and technical means in the prevention of penitentiary crimes. This issue has more than once become the object of discussion of scientists and practitioners. Based on the analysis of doctrinal sources, scientific research, statistical data, the article formulates a theoretical substantiation of the importance, necessity and effectiveness of use of information technologies and technical means in the prevention of penitentiary crimes

Detection methods of low-speed small objects for panoramic ultrashort pulsed radar

The article discusses ways to improve the detection efficiency of small and low-speed objects in conditions of intense background reflections. The properties of the ultrashort pulse echo signals are investigated. The phenomenon of interfering visibility is investigated

Diagnostics and Characterization of Photonic Circuits by Wide-Field Spatiotemporal Imaging

The growing diffusion of integrated photonic technologies requires fast and noninvasive quality control techniques for mass production. We present a general diagnostic technique for subps imaging of photonic circuits combining wide-field optical microscopy and optical gating. The simultaneous access to multiple parameters of a photonic structure enables an unprecedented characterization of its functional design as opposed to typical single-domain techniques such as frequency or time domain reflectometry and near-field microscopy. The noncontact and nonperturbative nature of the technique makes it relevant for both planar and three-dimensional circuits, as well as for silicon, polymeric, or hybrid platforms. We apply our technique to different photonic chip components fabricated by Direct Laser Writing, revealing the spatial and temporal hallmarks of fabrication imperfections causing losses or deviations from the intended device behavior. At the same time, the technique allows in situ probing of the key properties of photonic devices as the local propagation constants of guided modes or the quality factor of resonant elements. Our method is relevant for both the scientific and the industrial communities, as it lends itself to be scaled up to in-line quality control thanks to its nonscanning nature

In‐depth polarisation resolved SHG microscopy in biological tissues using iterative wavefront optimisation

International audienceAbstract Polarised nonlinear microscopy has been extensively developed to study molecular organisation in biological tissues, quantifying the response of nonlinear signals to a varying incident linear polarisation. Polarisation Second harmonic Generation (PSHG) in particular is a powerful tool to decipher sub‐microscopic modifications of fibrillar collagen organisation in type I and III collagen‐rich tissues. The quality of SHG imaging is however limited to about one scattering mean free path in depth (typically 100 micrometres in biological tissues), due to the loss of focus quality, induced by wavefront aberrations and scattering at even larger depths. In this work, we study how optical depth penetration in biological tissues affects the quality of polarisation control, a crucial parameter for quantitative assessment of PSHG measurements. We apply wavefront shaping to correct for SHG signal quality in two regimes, adaptive optics for smooth aberration modes corrections at shallow depth, and wavefront shaping of higher spatial frequencies for optical focus correction at larger depths. Using nonlinear SHG active nanocrystals as guide stars, we quantify the capabilities of such optimisation methods to recover a high‐quality linear polarisation and investigate how this approach can be applied to in‐depth PSHG imaging in tissues, namely tendon and mouse cranial bone

Adaptive scans allow 3D-targeted laser dissection to probe the mechanics of cell sheets

International audienceThe mechanical actuation of cells by active forces from the cytoskeleton drives tissue morphogenesis. To understand these forces, multicellular laser dissection has become an essential tool for severing tissue locally and inferring tension from the recoil of surrounding structures. However, conventional laser dissection is limited by 2D steering, which is inadequate for embryos and developing tissues that are intrinsically 3D structures. In this study, we introduce a flexible near-infrared (NIR) fs-pulsed laserdissection system that allows for dissection trajectories to proceed in 3D and adapt to the curved surfaces of cell sheets, which are prominent structures in embryos. Trajectories are computed through an unsupervised search for the surface of interest. Using this technique, we demonstrate sectioning of multicellular domains on curved tissue, which was not possible with regular NIR laser scanning. We apply the developed strategy to map mechanical stresses in the imaginal disc of the developing Drosophila wing. Our targeted, adaptive scans can be used in other nonlinear processes, such as two-photon fluorescence imaging or optogenetics. Overall, this new laser-dissection system offers an innovative solution for studying complex 3D structures and their mechanical properties

Adaptive scans allow targeted cell-ablations on curved cell sheets

Tissue morphogenesis proceeds through the mechanical actuation of cells by active forces from the cytoskeleton. Multicellular laser ablation has emerged as an essential means to probe these active forces by severing the tissue locally and inferring the tension born by the severed domain from the recoil of the surrounding structures. The realm of applications of laser ablations is however limited by the 2D steering of the laser in most instrumental configurations, while embryos and developing tissues are intrinsically 3D structures. Here, we present a flexible near infrared (NIR) fs-pulsed laser ablation system in which ablation trajectories proceed in 3D and adapt to the curved surface of cell sheets, which are prominent structures in embryos. Trajectories are computed through an unsupervised search for the surface of interest. We demonstrate that, depending on the exact experimental setup, the surface estimation can rely on a high content 3D imaging with a combined confocal microscope, or alternatively on a rapid Lissajou scan of the sample space with a NIR stand-alone setup. We apply the developed strategy mapping tensions in the developing Drosophila wing imaginal disc. These targeted, adaptive scans could be applied to other forms of non-linear processes such as two-photon fluorescence imaging or opto-genetics