Design and fabrication of ultrathin nanophotonic devices based on metasurfaces

Wydział FizykiOd kilkuset lat badania natury światła fascynuje naukowców na całym świecie. W XVII wieku, holenderski astronom i matematyk, Willebrord Snellius zdefiniował pojęcie refrakcji światła, które później od jego nazwiska zostało nazwane prawem Snella. Prawo to wciąż jest szeroko stosowane, a jego uogólnienie w roku 2011 zaproponował prof. Capasso z Uniwersytetu Harvarda. Uogólnione prawo Snella pozwala na rozwijanie technik kontroli frontów falowych wykorzystując powierzchnie zmieniające ich fazę w transmisji lub w odbiciu, zwane metapowierzchniami. Uogólnione prawo Snella jest zgodne z zasadą Fermata a wytwarza się je przy użyciu bardzo małych struktur mogących arbitralnie modyfikować amplitudę, fazę, polaryzację fali światła. Mechanizm odpowiedzialny za to zjawisko można dostosować do konkretnych zakresów długości fali i jest szczególnie dobrze sprawdzone dla światła z zakresu widzialnego. W pracy doktorskiej przedstawiłem koncepcję wykorzystania metapowierzchni do projektowania kilku urządzeń nanofotonicznych. Zaprojektowałem w pełni dielektryczne filtry koloru na bazie krzemu, które efektywnie działają dla fal przechodzących i odbitych. Rozszerzyłem te badania również o projekt dynamicznych i przestrajalnych filtrów kolorów kontrolując polaryzację światła przy wykorzystaniu ciekłych kryształów. Następnie zaproponowałem koncepcję urządzenia wykorzystujące zjawisko impedancji powierzchniowej do sterowania transmisją i umożliwiając prowadzenie fal w płaszczyźnie falowodu kryształu fotonicznego.Light is one of the most fascinating research areas of science since the past few centuries and this century no exception. In 17th, Snell's law was introduced by Willebrord Snellius a Dutch astronomer and mathematician, which explain the properties of refraction and reflection of light. In 2011, prof. Capasso group from Harvard University generalized the Snell's law and introduce a new way to modify the wave-front of the wave using phase varying surfaces. The modified Snell's law follows the Fermat principle for the phase changing surfaces. This phase changing surface can be created using tiny nanostructures to arbitrarily modified the amplitude, phase, polarization of the wave, commonly known as metasurfaces. The concept is scalable to arbitrary wavelength range and very well followed especially in the visible range. In this thesis, I used the concept of metasurfaces to design and fabricate the different nanophotonics devices. I design and fabricate the Si-based all-dielectric color filters which can be used in transmission and reflection mode. The color filter design presented in this thesis is very efficient due to the all dielectric material approach. I also extended the research to design dynamically tunable color filters with the aid of source polarisation and liquid crystal. Furthermore, I also proposed the surface impedance approach to control the in-plane transmission within the photonic crystal waveguide

Design and fabrication of ultrathin nanophotonic devices based on metasurfaces

Wydział FizykiOd kilkuset lat badania natury światła fascynuje naukowców na całym świecie. W XVII wieku, holenderski astronom i matematyk, Willebrord Snellius zdefiniował pojęcie refrakcji światła, które później od jego nazwiska zostało nazwane prawem Snella. Prawo to wciąż jest szeroko stosowane, a jego uogólnienie w roku 2011 zaproponował prof. Capasso z Uniwersytetu Harvarda. Uogólnione prawo Snella pozwala na rozwijanie technik kontroli frontów falowych wykorzystując powierzchnie zmieniające ich fazę w transmisji lub w odbiciu, zwane metapowierzchniami. Uogólnione prawo Snella jest zgodne z zasadą Fermata a wytwarza się je przy użyciu bardzo małych struktur mogących arbitralnie modyfikować amplitudę, fazę, polaryzację fali światła. Mechanizm odpowiedzialny za to zjawisko można dostosować do konkretnych zakresów długości fali i jest szczególnie dobrze sprawdzone dla światła z zakresu widzialnego. W pracy doktorskiej przedstawiłem koncepcję wykorzystania metapowierzchni do projektowania kilku urządzeń nanofotonicznych. Zaprojektowałem w pełni dielektryczne filtry koloru na bazie krzemu, które efektywnie działają dla fal przechodzących i odbitych. Rozszerzyłem te badania również o projekt dynamicznych i przestrajalnych filtrów kolorów kontrolując polaryzację światła przy wykorzystaniu ciekłych kryształów. Następnie zaproponowałem koncepcję urządzenia wykorzystujące zjawisko impedancji powierzchniowej do sterowania transmisją i umożliwiając prowadzenie fal w płaszczyźnie falowodu kryształu fotonicznego.Light is one of the most fascinating research areas of science since the past few centuries and this century no exception. In 17th, Snell's law was introduced by Willebrord Snellius a Dutch astronomer and mathematician, which explain the properties of refraction and reflection of light. In 2011, prof. Capasso group from Harvard University generalized the Snell's law and introduce a new way to modify the wave-front of the wave using phase varying surfaces. The modified Snell's law follows the Fermat principle for the phase changing surfaces. This phase changing surface can be created using tiny nanostructures to arbitrarily modified the amplitude, phase, polarization of the wave, commonly known as metasurfaces. The concept is scalable to arbitrary wavelength range and very well followed especially in the visible range. In this thesis, I used the concept of metasurfaces to design and fabricate the different nanophotonics devices. I design and fabricate the Si-based all-dielectric color filters which can be used in transmission and reflection mode. The color filter design presented in this thesis is very efficient due to the all dielectric material approach. I also extended the research to design dynamically tunable color filters with the aid of source polarisation and liquid crystal. Furthermore, I also proposed the surface impedance approach to control the in-plane transmission within the photonic crystal waveguide

Electromagnetic anapoles of a Cartesian expansion of localized electric currents

Electromagnetic anapoles are nonradiating oscillations of electric charge. They are known to be formed by a combination of an ordinary and a toroidal multipole. In this work, we introduce a different family of anapoles based on a Cartesian electric-current multipole expansion and propose a way to create the lowest-order, centrosymmetric member of this family. We also find a nontoroidal multipole structure that radiates as an electric dipole despite its zero total dipole moment. Radiation-free charge oscillations are interesting not only in view of their unique fundamental properties, but also in view of practical applications, e.g., in near-field-based optical sensing and detection.Peer reviewe

Light guiding, bending, and splitting via local modification of interfaces of a photonic waveguide

A general approach to the surface control of the localization, guiding, and redirecting of volume-mode light in photonic waveguides via tailoring their interfaces (surfaces) is proposed. The approach is demonstrated for dielectric rod-type photonic crystal slabs, whose regular and defect parts are distinguished by whether the nanocylinders are covered by metal caps. Thus, the rod-array part of the structure is not changed, while the local modifications are only applied to the interfaces. The basic functionalities, i.e., localized volume wave guiding, bending, and splitting are achievable. Selective dual-mode operation is possible due to the co-existence of a defect mode and a chainlike mode in one structure.status: publishe

All-dielectric metasurfaces based on cross-shaped resonators for color pixels with extended gamut.

Printing technology based on plasmonic structures has many advantages over pigment-based color printing such as high resolution, ultracompact size, and low power consumption. However, due to high losses and broad resonance behavior of metals in the visible spectrum, it becomes challenging to produce well-defined colors. Here, we investigate cross-shaped dielectric nanoresonators, which enable high-quality resonances in the visible spectral regime and, hence, high-quality colors. We numerically predict and experimentally demonstrate that the proposed all-dielectric nanostructures exhibit high-quality colors with selective wavelengths, in particular, due to lower losses as compared to metal-based plasmonic filters. This results in fundamental colors (RGB) with high hue and saturation. We further show that a large gamut of colors can be achieved by selecting the appropriate length and width of individual Si nanoantennas. Moreover, the proposed all-dielectric metasurface-based color filters can be integrated with the well-matured fabrication technology of electronic devices.by Vishal Vashistha, Gayatri Vaidya, Ravi S. Hegde, Andriy E. Serebryannikov, Nicolas Bonod and Maciej Krawczy

Health outcomes and healthcare resource utilization among Veterans with stage IV non-small cell lung cancer treated with second-line chemotherapy versus immunotherapy

Background Until recently, multi-agent chemotherapy (CT) was the standard of care for patients with advanced non-small cell lung cancer (NSCLC). Clinical trials have confirmed benefits in overall survival (OS) and progression-free survival with immunotherapy (IO) compared to CT. This study compares real-world treatment patterns and outcomes between CT and IO administrations in second-line (2L) settings for patients with stage IV NSCLC. Materials and methods This retrospective study included patients in the United States Department of Veterans Affairs healthcare system diagnosed with stage IV NSCLC during 2012–2017 and receiving IO or CT in the 2L. Patient demographics and clinical characteristics, healthcare resource utilization (HCRU), and adverse events (AEs) were compared between treatment groups. Logistic regression was used to examine differences in baseline characteristics between groups, and inverse probability weighting multivariable Cox proportional hazard regression was used to analyze OS. Results Among 4,609 Veterans who received first-line (1L) therapy for stage IV NSCLC, 96% received 1L CT alone. A total of 1,630 (35%) were administered 2L systemic therapy, with 695 (43%) receiving IO and 935 (57%) receiving CT. Median age was 67 years (IO group) and 65 years (CT group); most patients were male (97%) and white (76–77%). Patients administered 2L IO had a higher Charlson Comorbidity Index than those administered CT (p = 0.0002). 2L IO was associated with significantly longer OS compared with CT (hazard ratio 0.84, 95% CI 0.75–0.94). IO was more frequently prescribed during the study period (p Conclusions Overall, the proportion of advanced NSCLC patients receiving 2L systemic therapy is low. Among patients treated with 1L CT and without IO contraindications, 2L IO should be considered, as this supports potential benefit of IO for advanced NSCLC. The increasing availability and indications for IO will likely increase the administration of 2L therapy to NSCLC patients

Health outcomes and healthcare resource utilization among Veterans with stage IV non-small cell lung cancer treated with second-line chemotherapy versus immunotherapy.

BackgroundUntil recently, multi-agent chemotherapy (CT) was the standard of care for patients with advanced non-small cell lung cancer (NSCLC). Clinical trials have confirmed benefits in overall survival (OS) and progression-free survival with immunotherapy (IO) compared to CT. This study compares real-world treatment patterns and outcomes between CT and IO administrations in second-line (2L) settings for patients with stage IV NSCLC.Materials and methodsThis retrospective study included patients in the United States Department of Veterans Affairs healthcare system diagnosed with stage IV NSCLC during 2012-2017 and receiving IO or CT in the 2L. Patient demographics and clinical characteristics, healthcare resource utilization (HCRU), and adverse events (AEs) were compared between treatment groups. Logistic regression was used to examine differences in baseline characteristics between groups, and inverse probability weighting multivariable Cox proportional hazard regression was used to analyze OS.ResultsAmong 4,609 Veterans who received first-line (1L) therapy for stage IV NSCLC, 96% received 1L CT alone. A total of 1,630 (35%) were administered 2L systemic therapy, with 695 (43%) receiving IO and 935 (57%) receiving CT. Median age was 67 years (IO group) and 65 years (CT group); most patients were male (97%) and white (76-77%). Patients administered 2L IO had a higher Charlson Comorbidity Index than those administered CT (p = 0.0002). 2L IO was associated with significantly longer OS compared with CT (hazard ratio 0.84, 95% CI 0.75-0.94). IO was more frequently prescribed during the study period (p ConclusionsOverall, the proportion of advanced NSCLC patients receiving 2L systemic therapy is low. Among patients treated with 1L CT and without IO contraindications, 2L IO should be considered, as this supports potential benefit of IO for advanced NSCLC. The increasing availability and indications for IO will likely increase the administration of 2L therapy to NSCLC patients