Smectic and soap bubble optofluidic lasers

Soap bubbles are simple, yet very unique and marvelous objects. They exhibit a number of interesting properties such as beautiful interference colors and the formation of minimal surfaces. Various optical phenomena have been studied in soap films and bubbles, but so far they were not employed as optical cavities. Here we demonstrate, that dye doped soap or smectic liquid crystal bubbles can support whispering gallery mode lasing, which is observed in the spectrum as hundreds of regularly spaced peaks, resembling a frequency comb. The lasing enabled the measurement of size changes as small as 10 nm in a millimeter-sized, $\sim$100 nm thick bubble. Bubble lasers were used as extremely sensitive electric field sensors with a smallest measurable electric field of 110 Vm$^{-1}$Hz$^{-1/2}$. They also enable the measurement of pressures up to a 100 bar with a resolution of 1.5 Pa, resulting in a dynamic range of almost $10^7$. By connecting the bubble to a reservoir of air, almost arbitrarily low pressure changes can be measured while maintaining an outstanding dynamic range. The demonstrated soap bubble lasers are a very unique type of microcavities which are one of the best electric field and pressure microsensors to date and could in future also be employed to study thin films and cavity optomechanics

Cellular dye lasers : lasing thresholds and sensing in a planar resonator

This research was supported in part by the U.S. National Science Foundation (ECCS-1101947, ECCS-1505569) and National Institutes of Health (P41 EB015903). M.H. was supported in part by the Marie Curie International Outgoing Fellowship N° 627274 within the 7th European Community Framework Programme. M.C.G. was supported in part by the Starting Grant N° 640012 within the H2020 European Community Framework Programme.Biological cell lasers are promising novel building blocks of future biocompatible optical systems and offer new approaches to cellular sensing and cytometry in a microfluidic setting. Here, we demonstrate a simple method for providing optical gain by using a variety of standard fluorescent dyes. The dye gain medium can be located inside or outside a cell, or in both, which gives flexibility in experimental design and makes the method applicable to all cell types. Due to the higher refractive index of the cytoplasm compared to the surrounding medium, a cell acts as a convex lens in a planar Fabry-Perot cavity. Its effect on the stability of the laser cavity is analyzed and utilized to suppress lasing outside cells. The resonance modes depend on the shape and internal structure of the cell. As proof of concept, we show how the laser output modes are affected by the osmotic pressure.Publisher PDFPeer reviewe

Laser Particle Stimulated Emission Microscopy

We introduce an optical microscopy technique that utilizes micro- or nanolasers embedded in a sample as imaging probes. The narrow spectra and nonlinear power dependence of stimulated emission from the laser particles yield optical sectioning, subdiffraction resolution, and low out-of-focus background. A proof of concept is demonstrated using perovskite nanowires.National Science Foundation (U.S.) (Grant ECCS-1505569)National Institutes of Health (U.S.) (Grants DP1EB024242 and P41EB015903)Massachusetts General Hospital. Research Scholar Award Progra

Vector beams generated by microlasers based on topological liquid-crystal structures

Structured light with designable intensity, polarization and phase fields is today of high relevance, with application ranging from imaging, metrology, optical trapping, ultracold atoms, classical and quantum communications and memory. Specifically, vortex and vector beams can be generated directly in the laser cavity, however, a controllable, geometrically simple and easy to manufacture laser microcavity that generates structured light on demand, especially tailored polarization, is still an open challenge. Here we show that tunable laser vector beams can be generated from self-assembled liquid-crystal (LC) micro-structures with topological defects inside a thin Fabry-P\'erot microcavity. The LC superstructure provides complex three dimensional birefringent refractive index profiles with order parameter singularities. The topology of the LC structures is transferred into the topology of the light polarization. The oriented fluorescent dye emission dipoles enable the selection of optical modes with a particular polarization, as enabled by the birefringence profile in the laser cavity. The proposed lasers have no principal limitation for realizing structured light with arbitrarily tailored intensity and polarization fields

Toward biomaterial-based implantable photonic devices

Optical technologies are essential for the rapid and efficient delivery of health care to patients. Efforts have begun to implement these technologies in miniature devices that are implantable in patients for continuous or chronic uses. In this review, we discuss guidelines for biomaterials suitable for use in vivo. Basic optical functions such as focusing, reflection, and diffraction have been realized with biopolymers. Biocompatible optical fibers can deliver sensing or therapeutic-inducing light into tissues and enable optical communications with implanted photonic devices. Wirelessly powered, light-emitting diodes (LEDs) and miniature lasers made of biocompatible materials may offer new approaches in optical sensing and therapy. Advances in biotechnologies, such as optogenetics, enable more sophisticated photonic devices with a high level of integration with neurological or physiological circuits. With further innovations and translational development, implantable photonic devices offer a pathway to improve health monitoring, diagnostics, and light-activated therapies. Keywords: biomaterials; biocompatible; biodegradable; optics; photonicsUnited States. Department of Defense (Award FA9550-13-1-0068)National Institutes of Health (U.S.) (Award P41-EB015903)National Institutes of Health (U.S.) (Award R01-CA192878)National Science Foundation (U.S.) (Award CBET-1264356)National Science Foundation (U.S.) (Award ECCS-1505569

Photonic Hydrogel Sensors

Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified

Bioabsorbable polymer optical waveguides for deep-tissue photomedicine

Advances in photonics have stimulated significant progress in medicine, with many techniques now in routine clinical use. However, the finite depth of light penetration in tissue is a serious constraint to clinical utility. Here we show implantable light-delivery devices made of bio-derived or biocompatible, and biodegradable polymers. In contrast to conventional optical fibres, which must be removed from the body soon after use, the biodegradable and biocompatible waveguides may be used for long-term light delivery and need not be removed as they are gradually resorbed by the tissue. As proof of concept, we demonstrate this paradigm-shifting approach for photochemical tissue bonding (PTB). Using comb-shaped planar waveguides, we achieve a full thickness (>10 mm) wound closure of porcine skin, which represents ∼10-fold extension of the tissue area achieved with conventional PTB. The results point to a new direction in photomedicine for using light in deep tissues

Photonic hydrogel sensors

Analyte-sensitive hydrogels that incorporate optical structures have emerged as sensing platforms for point-of-care diagnostics. The optical properties of the hydrogel sensors can be rationally designed and fabricated through self-assembly, microfabrication or laser writing. The advantages of photonic hydrogel sensors over conventional assay formats include label-free, quantitative, reusable, and continuous measurement capability that can be integrated with equipment-free text or image display. This Review explains the operation principles of photonic hydrogel sensors, presents syntheses of stimuli-responsive polymers, and provides an overview of qualitative and quantitative readout technologies. Applications in clinical samples are discussed, and potential future directions are identified

Potential wood biomass for energy purposes in Slovenia

Slovenija je ena najbolj gozdnatih držav v Evropinjena pokritost z gozdom je več kot 57 %. To zagotavlja velik potencial lesne biomase, ki bi ga lahko bolj učinkovito in v večjem obsegu izkoristili tudi v energetske namene. Les je pomembna surovina v lesno obdelovalni industriji, gradbeništvu, energetiki in celulozni industriji. Njegova poraba se že nekaj časa zmanjšuje, saj ga kot surovino, predvsem v energetiki in gradbeništvu, izpodrivajo drugi materialito pa ima negativen vpliv na okolje in družbo. Celovitejše izkoriščanje lesa iz naših gozdov bi imelo pozitiven vpliv tako v lesni obdelovalni industriji kot energetiki. Omogočilo bi večjo rast prihodka, odpiranje novih delovnih mest, zmanjševanje emisij toplogrednih plinov in večjo samooskrbo s toplotno energijo. V Sloveniji se les kot biomasa v energetske namene uporablja predvsem na podeželjuskupno pa se z lesom ogreva približno 30 % prebivalstva. V zadnjem obdobju se zaradi sodobnih tehnologij pridobivanja, predelave in rabe lesa, kot tudi zaradi sodobnih sistemov kurjenja z visokimi energijskimi izkoristki, opaza povečanje uporabe lesne biomase kot goriva.Slovenia is one of the most forested countries in Europe. More than 57 % of its surface is covered with forests, securing a large potential, which could be used more efficiently, and in greater extend also for energy purposes. Wood is an important raw material in wood industry, in civil engineering, in energy and cellulose industry. Wood usage has been reduced. As a raw material it has been superseded by other materials, especially in energy and civil engineeringthis having a bad influence for environment and society. Better exploitation of wood from our forests would have better influence on wood industry, as well on energy. It would enable to rise revenues, new employments, as well at reduce emission from greenhouse gases and bigger self-sufficiency with heat energy. In Slovenia, wood as biomass is used especially in the country30 % of population use it. In the last period, the interest to use wood biomass increased, especially because of contemporary technology of acquiring, processing and using wood, as well as because of contemporary systems of heating with good energy results