Metasurfaces incorporating plasmonic/dielectric nanostructures for light wavefront manipulation

Gao, Song Kwangwoon University Graduate School 2019 국내박사

Metasurface holds a great promise to replace conventional bulky and heavy optical components/modules, owing to its unprecedented capability in manipulating the light properties including the phase, amplitude, and polarization over a subwavelength scale. This dissertation elaborates on the investigation and demonstration of various types of metasurfaces comprising subwavelength-scaled plasmonic/dielectric nanostructures for tailoring the optical light wavefront. The metasurfaces are developed for diverse applications including light steering, polarization spectrum splitting, and light focusing, to overcome the existing issues of conventional metasurfaces such as the dispersion of the phase gradient, operation bandwidth, number of functionalities, and operation efficiency. First, an aluminum plasmonic metasurface, capitalizing on a metal-dielectric-metal configuration where the ground plane is coupled with a trapezoidal aluminum nanoantenna via a dielectric layer, is conceived to render a wavelength-insensitive phase gradient for the linearly polarized visible light. Considering the light in the whole visible band is normally incident on the sample, the transverse-electric component of the light is directly reflected from the fabricated sample, while the transverse-magnetic component of light is highly angle-resolved via an anomalous reflection. An optical device with minimized dimensions, which is able to efficiently resolve an ultra-broad spectrum into a wide splitting angle but incurring no spectrum overlap, is of great importance. Towards that end, we further present vertically integrated visible and near-infrared metasurfaces by resorting to a supercell that consists of two vertically concatenated trapezoidal aluminum antennae, that are paired with a metallic ground plane via a dielectric layer. Under normal incidence, reflected light from the visible to NIR is angle-resolved to a single diffraction order without spectrum overlap, exhibiting a high reflection efficiency and a substantial angular splitting. In light of the supercell pitch and the observed prominent results, a world-record operation bandwidth for spectrum splitting has been accomplished. In a bid to mitigate the intrinsic absorption loss in metals and to meet the demands for both device miniaturization and integration, a highly efficient bifunctional all-dielectric metasurface for operation in the transmission mode is conceived. The metasurface, taking advantage of a unit cell, the building block of which capitalizes on a nanopost in hydrogenated amorphous silicon, successfully renders polarization-mediated anomalous beam steering and focusing in the visible band. For the fabricated sample, the normal transverse-electric incidence within a broad spectral band is angle-resolved to a single diffraction order via the beam steering, while a bright line focus is attained at the target focal plane for the normal transverse-magnetic incidence at a selected wavelength. The various type of metasurface devices resorting to plasmonic and dielectric nanostructures as mentioned, are anticipated to pave a way for the miniaturization of optical devices and readily to be applied in the construction of integrated photonic systems.

Edvard Hagerup Grieg piano sonata in E minor, Op. 7에 관한 연구

Gao, Song 이화여자대학교 대학원 2012 국내석사

본 논문은 에드바르드 그리그(Edvard Hagerup Grieg, 1843-1907)의 <Piano Sonata in E minor, Op. 7>에 관한 분석 연구이다. 19세기 후반기에 들어서면서 유럽에서는 민족주의(Nationalism)가 새롭게 등장한다. 민족주의 음악은 국가의 민속음악을 발굴, 채집하여 전통적인 음악으로 만든 것이다. 이들 민족주의는 독일, 이탈리아, 프랑스의 음악에 크게 영향을 받은 러시아 , 동유럽, 북유럽 등 나라들에서 활발히 나타났다. <Piano Sonata in E minor, Op. 7>은 그리그의 유일한 피아노 소나타이며 4개 악장으로 이루어져 있는데, 1악장은 소나타 형식, 2악장은 A-B-A' 형식, 3악장은 미뉴에트-트리오-미뉴에트 형식, 4악장은 소나타 형식으로 되어 있다. 이 작품은 전통적인 고전소나타 형식을 취하고, 노르웨이의 민속적인 선율과 리듬의 인용, 대조되는 주제 변화, 다양한 지속음과 연속적인 반음계 진행, 빈번한 전조 등 여러 기법을 사용함으로써 그리그만이 지닌 특색과 민족성이 반영되었다. 그리그는 19세기 후기 노르웨이를 대표하는 민족주의 음악가로써 노르웨이의 국민음악의 기초를 확립하는데 크게 공헌을 하였다. 그의 초기 음악은 독일 낭만주의 음악기법의 영향을 받았지만 그 후에는 전통적인 고전주의 형식 위에 노르웨이 민족음악 요소를 음악으로 표현하여 민족적 정서가 뚜렷이 드러났다. Norwegian composer Edward Grieg(1843―1907) was the founder of Norwegian folk music and one of the most outstanding composers in the late 19th century's European folk music world. He dedicated to there search of folk music and by paying tribute to the country's history and with his artistic feeling for the nature and folk life, he produced music compositions with strong Norwegian folk characteristics and flavor. In June of 1865 Grieg spent 11 days on the piano sonata Op.7, the only sonata of all his piano compositions. This traditional sonata consists of four movements, namely, the first movement ,Allegro moderato, is composed of recapitulation, development, exposition and coda; the second, andante molto, is in the A-B-A pattern, the third, Alla Menuetto ma poco piu lento is composed of minuet-trio-minuet and the fourth movement, molto allegro, like the first, is of the traditional sonata form. This paper, starting with the music chart of Grieg's piano sonata Op.7, explores Norwegian folk music, the composer's life and the background of his compositions and analyzes his music style and structure, his peculiar features, the rhythm, tune, harmonics, melody etc. He employed, displays the writer's perception and knowledge of the style of the North European folk music in the 19th century and its contribution to the music creation in the 20th century.

Robert Starer 중급 피아노 작품 Sketches in Color 분석 연구

GAO SONG 세종대학교 대학원 2017 국내박사

Robert Starer (1924-2001)는 오스트리아 출신의 미국 현대음악 작곡가이자 음악교육가 겸 피아니스트이다. Starer는 음악교육자로서 어린이 음악교육에 관심이 많으며, 다조성, 12음기법, 무조성, jazz 등 20세기 다양한 음악어법을 경험할 수 있는 많은 피아노 교육용 작품들을 작곡하였다. 이러한 작품들은 북미 지역에서 활용되고 있으며 현대음악 지도에 있어 교육적 가치가 높은 레퍼토리로 평가를 받고 있다. Starer의 대표적인 작품 Sketches in Color는 현대적인 색채감이 넘치는 중급 교육용 피아노 작품이며, Set 1 (1963)과 Set 2 (1973)로 구성된다. 두 set는 모두 7개의 짧은 소곡으로 이루어져 있으며 각 소곡들에는 특정 color를 명시하는 title이 붙는 것이 특징이다. 또한 Sketches in Color는 다조성, 12음기법, 무조성, 신조성, 점묘주의, tone cluster, jazz, 변박자, 타악기적인 주법 등 다양한 20세기 작곡기법들이 포함되어 있다. 이 작품에서 Starer는 음악과 색이 가지고 있는 연관성을 이용하여 20세기 음악요소들을 color와 접목시킴으로써 자신의 음악어법을 고안함과 동시에 20세기 현대음악 접근법의 새로운 장을 열었다. Set 1은 Starer의 아들 Dan의 피아노 학습을 위해 작곡하였으며, 그는 이 작품을 통해 아이들이 20세기 음악을 흥미롭게 공부할 수 있기를 희망하였다. Sketches in Color Set 1은 1. Purple, 2. Shades of Blue, 3. Black and White, 4. Bright Orange, 5. Grey, 6. Pink, 7. Crimson으로 구성되었으며 Set 2는 1. Maroon, 2. Aluminum, 3. Sliver and Gold, 4. Khaki, 5. Pepper and Salt, 6. Aquamarine, 7. Chrome Yellow로 구성되었다. Set 2에 수록된 곡들은 Set 1과 다르게 곡 제목에서 color뿐만 아니라 금속계열인 aluminum, silver, gold와 조미료 계열인 pepper, salt등 다양한 소재들을 음악으로 표현하였으며 이는 Set 1보다 기교적으로 어렵고 음악적인 면에서도 더욱 깊이가 있다.

Laboratory studies and field measurements of organic compounds in tropospheric aerosols

Gao, Song University of Washington 2002 해외박사(DDOD)

소속기관이 구독 중이 아닌 경우 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

This dissertation explores the chemical identity, sources, and formation pathways of organic compounds in tropospheric aerosols. Laboratory studies and field measurements are integrated to achieve two main objectives. The 1<super>st</super> objective is to better understand some secondary organic aerosol formation processes and their potential importance in the marine boundary layer (MBL). This is achieved by studying three hydrocarbon-ozone systems in a controlled chamber. It is found that at plausible concentrations in the MBL, these systems readily form new submicron particles, with dicarboxylic acids as important components. It is proposed that the particle nucleation is most likely due to the H₂SO₄-H₂O-NH₃ nucleation, whereas the particle growth is mainly due to the partitioning of organic products and the condensation of water vapor. This study lends substantial experimental support to such a particle nucleation and growth scheme, which can be a common process in the MBL and help explain the observed cloud condensation nuclei (CCN) budget. The 2<super>nd</super> objective is to better identify and quantify organic species in tropospheric aerosols, and study their possible sources and formation pathways. A novel methodology, electrospray ionization mass spectrometry used concurrently with ion chromatography, is developed to measure carbohydrate species in ambient aerosol samples. Airborne measurements in southern Africa show that carbohydrates and organic acids are important aerosol components in that region. In addition, even though biomass burning is the only major source during the dry season there, the aerosol composition is affected by more than one factor, including the combustion phase of the biomass fires, and the aerosol aging processes. Airborne measurements in eastern Asia and the Northwest Pacific show that four major sources, i.e., soil dust, biomass burning, pollution, and sea salt, can simultaneously affect the aerosol composition there. The interplay of multiple sources, meteorological conditions, and aging processes results in a highly variable aerosol composition in that region. It is therefore recognized that aerosol composition is at least source-dependent and region-dependent, and organic species are often, but not always, one of the major constituents in tropospheric aerosols.