Ultrafast optical manipulation of magnetic order in ferromagnetic materials

Wang Chuangtang,Liu Yongmin 나노기술연구협의회 2020 Nano Convergence Vol.7 No.35

The interaction between ultrafast lasers and magnetic materials is an appealing topic. It not only involves interesting fundamental questions that remain inconclusive and hence need further investigation, but also has the potential to revolutionize data storage technologies because such an opto-magnetic interaction provides an ultrafast and energyefficient means to control magnetization. Fruitful progress has been made in this area over the past quarter century. In this paper, we review the state-of-the-art experimental and theoretical studies on magnetization dynamics and switching in ferromagnetic materials that are induced by ultrafast lasers. We start by describing the physical mechanisms of ultrafast demagnetization based on different experimental observations and theoretical methods. Both the spin-flip scattering theory and the superdiffusive spin transport model will be discussed in detail. Then, we will discuss laser-induced torques and resultant magnetization dynamics in ferromagnetic materials. Recent developments of all-optical switching (AOS) of ferromagnetic materials towards ultrafast magnetic storage and memory will also be reviewed, followed by the perspectives on the challenges and future directions in this emerging area.

Measuring the optical permittivity of two-dimensional materials without <i>a priori</i> knowledge of electronic transitions

Jung, Gwang-Hun,Yoo, SeokJae,Park, Q-Han De Gruyter 2019 Nanophotonics Vol.8 No.2

<P><B>Abstract</B></P><P>We propose a deterministic method to measure the optical permittivity of two-dimensional (2D) materials without<I>a priori</I>knowledge of the electronic transitions over the spectral window of interest. Using the thin-film approximation, we show that the ratio of reflection coefficients for s and p polarization can give a unique solution to the permittivity of 2D materials within the measured spectral window. The uniqueness and completeness of our permittivity measurement method do not require<I>a priori</I>knowledge of the electronic transitions of a given material. We experimentally demonstrate that the permittivity of monolayers of MoS<SUB>2</SUB>, WS<SUB>2</SUB>, and WSe<SUB>2</SUB>in the visible frequency range can be accurately obtained by our method. We believe that our method can provide fast and reliable measurement of the optical permittivity of newly discovered 2D materials.</P>

Zirconia nanocomposites and their applications as transparent advanced optical materials with high refractive index

이든찬,조한준,윤일선 대한화학회 2023 Bulletin of the Korean Chemical Society Vol.44 No.4

Polymer nanocomposites, prepared by incorporating functional nanoparticles (NPs) into a polymer matrix, have advantages of utilizing functionalities of poly- mers and NPs. Among them, transparent high-refractive-index polymer nano- composites (THPNs), prepared by incorporating highly refractive NPs into polymer matrices, are advantageous for effectively manipulating light. This review focuses on the introduction of fabrication of THPN prepared by incorpo- rating inorganic-oxide NPs, especially zirconia (ZrO2), and its characteristics as an optical material. ZrO2 NPs have a high refractive index and high transmit- tance in visible light regions with high and narrow optical bandgap energy. Since ZrO2 NPs are harmless to humans and physically and chemically stable, they are suitable for applications of advanced optical materials for display and energy devices. Various fabrication methods of THPN with ZrO2 NPs and sur- face modifications of ZrO2 NPs to prevent agglomeration are introduced. Prin- ciples and specific applications, which THPN could work with and for, are introduced as well.

Graphene-based plasmonic waveguide devices for electronic-photonic integrated circuit

Kim, Jin Tae,Choe, Jong-Ho,Kim, Jin-Soo,Seo, Dongjea,Kim, Young Duck,Chung, Kwang Hyo Elsevier 2018 OPTICS AND LASER TECHNOLOGY Vol.106 No.-

<P><B>Abstract</B></P> <P>Graphene is a one-atom thick carbon film packed in a honeycomb structure, and because it has extraordinary optoelectronic properties, it has attracted a great deal of attention in the field of photonics. Graphene-based plasmonic photonic devices have been developed which are capable of emitting, transmitting, modulating, and detecting light wave signals using a single material. In this paper, we propose the concept of on-chip graphene electronic-photonic integrated circuits (EPICs) architecture, and present developments and perspectives on the essential graphene plasmonic-based photonic components, including the plasmonic waveguide, modulator, and photodetector, which are based on the graphene EPICs. The optical characteristics and design considerations of the graphene-based photonic devices are discussed based on experimental and theoretical investigations at telecommunications wavelengths. In parallel, we provide new device design concepts and a potential solution for further improving their operating characteristics. We also performed a numerical investigation of the characteristics of the photonic devices to explain their operating principles and to predict their operating performances. The proposed photonic components were fabricated on an organic photonic chip using an optimized fabrication process, and their optical characteristics were experimentally demonstrated. Based on these results and demonstrations, we hope to introduce new perspectives on the future direction of graphene-EPICs in graphene plasmonics and the optical telecom field.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Architecture of graphene electronic-photonic integrated circuits is proposed. </LI> <LI> Characteristics of graphene-based plasmonic waveguide devices are investigated. </LI> <LI> Perspectives on the graphene-based plasmonic waveguide devices are presented. </LI> </UL> </P>

Synthesis, growth and studies of undoped and sodium chloride-doped Zinc Tris-thiourea Sulphate (ZTS) single crystals

C. Krishnan,P. Selvarajan,S. Pari 한국물리학회 2010 Current Applied Physics Vol.10 No.2

Single crystals of undoped (pure) and sodium chloride (NaCl)-doped Zinc Tris-thiourea Sulphate (ZTS)were grown from aqueous solutions by slow evaporation technique. Morphological alterations have been observed when NaCl is doped into ZTS crystals. Density of the grown crystals was measured by floatation method. The values of unit cell parameters from single crystal X-ray diffraction (XRD) studies show that pure and sodium chloride-doped ZTS crystals are in orthorhombic structure. Impurity concentration in the doped crystals was estimated by using an atomic absorption spectrometer. Second Harmonic Generation (SHG) test for the undoped and NaCl-doped ZTS crystals was performed by the powder technique of Kurtz and Perry using a pulsed Nd:YAG laser. Microhardness studies show that hardness number (Hv)increases with load for all the grown crystals of this work. From the values of work hardening coefficients,it is concluded that pure and sodium chloride-doped ZTS crystals belong to the category of soft materials. UV–vis–NIR spectra show that the grown crystals have wide optical transparency in the entire visible region. Birefringence studies of the grown samples have been performed by channelled spectrum method. The thermal stability of the materials is found to be increasing with the doping concentration of sodium chloride (NaCl) in the lattice of ZTS crystals.

Nanosize Control of Final Products from Sol-Gel Reactions for Optical Waveguides

( Se Yun Kim ),( Jeung Ku Kang ) 대한금속재료학회 ( 구 대한금속학회 ) 2005 ELECTRONIC MATERIALS LETTERS Vol.1 No.2

We determined the mechanism and the nanosize products of a sol-gel reaction with diphenylsilanediol (DPD) and 3-methacryloxypropyltrimethoxysilane (MEMO) precursors for synthesizing an optical waveguide material. From the first-principles calculation, we found that diphenyldimethoxysilane (DPDM) and 3-methacrylox-ypropylmethoxysilanediol (MEMDO) are generated through the first two steps, and we also determined that the reaction pathway could be modified by the presence of H2O released from a catalyst such as Ba(OH)2?H2O. In the final step, condensation between a MEMDO hydroxyl and a DPDM methoxy occurs, generating a DPDM-MEMDO dimer and CH3OH molecule as products. In a similar fashion, the DPDM of the DPDM-MEMDO dimer can condense with the MEMDO of another DPDM-MEMDO dimer to increase the chain, but its reaction rate of 2.8×10(-11) per second is predicted to be about five times smaller than that between DPDM and MEMDO. This implies that the reaction rate becomes smaller for larger nanostructures.

반사율 측정에 의한 적외선 광학재료의 중적외선 굴절률 추정

진두한,정경석 한국산학기술학회 2020 한국산학기술학회논문지 Vol.21 No.6

An optical arrangement has been set inside a photo-spectrometer to measure the reflectance of IR optics materials in mid IR range. The optical arrangement consists of equally spaced 4 gold coated full reflecting mirrors with the incidence angle of 45°. Baseline beam intensity has been measured while the beam proceeds through the 4 mirrors. Reflectance of a mirror has been estimated from the . And the beam intensity with the specimen in the optical path has been measured with the 4th mirror replaced with the specimen. Reflectance of the specimen has been estimated from the value of /. Then the estimated reflectance has been put in Fresnel equation relating reflectance and refractive index(RI) to estimate the RI of the material. Measurement has been made for sapphire, germanium, magnesium fluoride, and zinc sulfide. The estimated RI of the materials are closely matching with reference data and the maximum difference less than 2% over the wavelength range 3-5 m for all materials tested. As an FT-IR photo-spectrometer with a broadband wavelength infrared light source is used, this method has the advantage of measuring the refractive index at multiple wavelengths in a single measurement. 본 연구는 적외선 광학재료의 중적외선 영역의 굴절률을 파악하기 위해 반사율을 측정하고 굴절률과 반사율의 관계로부터 굴절률을 추정하는 방법을 제안한다. 전반사 거울 4개를 일정한 간격으로 배열하고 적외선 광원으로부터 연속 파장의 평행광이 45°로 입사되도록 광 경로를 구성한다. 광 경로를 따라 4개의 전반사 거울에 반사되어 온 광강도 IB 를 측정한 후, 광 경로의 마지막에 놓이는 거울을 시편으로 교체하고 광강도 Is 를 측정한다. IB와 Is, 전반사 거울의 비를 이용하여 재료의 반사율을 계산한다. 계산된 반사율과 Fresnel의 굴절률과 반사율 관계식에 넣고 시행착오법으로 굴절률을 추정한다. 이 방법을 적용하여 사파이어(Al2O3), 게르마늄(Ge), 불화마그네슘(MgF2), 황화아연(ZnS)재료를 대상으로 실험하고 굴절률을 추정하여 참고문헌자료들과의 비교를 통하여 모든 재료에 대해 파장범위 3 - 5 m에서 최대 차이 2% 이하로 잘 일치하는 결과를 얻을 수 있었으며, 이를 통해 본 굴절률 측정방법의 타당성을 확인할 수 있다. 본 연구에서 제시된 방법은 연속 파장의 적외선 광원을 사용하기 때문에 한 번의 측정으로 여러 파장에 대한 굴절률을 추정 할 수 있는 장점이 있다.

State of the art two-dimensional materials-based photodetectors: Prospects, challenges and future outlook

Adeela Rehman,Soo-Jin Park 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.89 No.-

The study of light at the nanoscale, known as nanophotonics, has become a vibrantfield of research. Recently, researchers are being focused to regulate theflow of light at length scales beyond the opticalwavelength, mainly outstripping the classical limits constraints by diffraction. In this regard, twodimensional(2D) and three-dimensional (3D) nanostructures sculpted from metallic and insulatingmaterials can refract,filter, scatter, and process light in intriguing ways, never possible before inconventional materials and traditional geometries. This control over light-matter interaction atnanoscale has not only unveiled new phenomena but has also launched variety of novel applications,developing new strategies for integrated circuitry, energy harvesting and electro-optical technologies,establishing high expectations for future innovative discoveries.

A Q-switched, 1.89µm fiber laser using an Fe₃O₄-based saturable absorber

Koo, Joonhoi,Lee, Junsu,Kim, Jihwan,Lee, Ju Han Elsevier 2018 Journal of luminescence Vol.195 No.-

<P><B>Abstract</B></P> <P>The potential of Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles as a base material for saturable absorbers (SAs) that can operate in the 2μm-wavelength regime, was investigated. An SA was fabricated on a sandwich-structured fiber-ferrule platform through the deposition of an Fe<SUB>3</SUB>O<SUB>4</SUB> mixture with polyvinyl alcohol (PVA) onto the end surface of the fiber ferrule. Using the prepared Fe<SUB>3</SUB>O<SUB>4</SUB>/PVA-composite-based SA within a Tm-Ho codoped fiber laser, stable Q-switched pulses were readily produced at 1894nm. The temporal characteristics of the output pulses were investigated as a function of the pump power, and the maximum energy of the output pulses was 322nJ. The temporal width of the output pulses was measured as 2.6µs at the maximum pulse-repetition rate of 37.2kHz. The output performance of the passively Q-switched Tm-Ho-codoped fiber laser in this work was compared with those of recently demonstrated, passively Q-switched Tm-doped fiber lasers for which the other types of saturable-absorption materials.</P>

건축 재료의 스펙트럼 특성에 관한 연구 : 화강석을 중심으로

조수현(Cho Su-Hyun),김원우(Kim WonWoo),신인중(Shin In-Jung),박진철(Park JinChul) 한국태양에너지학회 2011 한국태양에너지학회 학술대회논문집 Vol.2011 No.4

It is a wide range of types of building materials. Depending on the flow of time for the increased interest in building appearance of quality new and different materials are being developed. In particular, the case of granite widely used as cladding, recently, China's low-cost stone disguised as a large number of local granite stone as the domestic industry has been a big hit. Therefore, the purpose of study is establishment of the database for granite building exterior materials. For that, the domestic granite and chinese granite are selected. The spectrums of these material are investigated and analyzed.