Optical Properties (광학적 성질) Material Science Optical Properties (광학적 성질) Associate Professor Su-Jin Kim School of Mechanical Engineering Gyeongsang National University 1

OCW Lens production: https://www.youtube.com/watch?v=MKNFW0YwDYw Light Reflection Refraction: https://www.youtube.com/watch?v=xBYeV1DVXtM OLED Process Samsung https://www.youtube.com/watch?v=a-ojIZnn1ps Is radiation dangerous (TED 5min) https://youtu.be/zI2vRwFKnHQ

KOCW 재료의 광학적 성질1 http://www.kocw.net/home/cview.do?lid=88733f366e79a548 재료의 광학적 성질2 http://www.kocw.net/home/cview.do?lid=58ab3b5ee23c8e5b

Lights (빛) Electromagnetic wave (전자기 파동) Velocity of light c=300,000 km/s (Diameter of earth = 12,756 km) Wavelength λ (m) Frequency f (Hz) EM wave: http://www.youtube.com/watch?v=cfXzwh3KadE

Reflect, Absorb , Transmit Incident(입사) light is either reflected(반사), absorbed(흡수), transmitted(투과) or scattered(분산) Reflect Absorb Transmit Scatter Transparent Opaque Reflective Reflect Transmit Absorb: http://www.youtube.com/watch?v=d3puVP1lcn4

Light & Electron transition Incident light(photon) of energy E=hν transit near surface electron from ground state to exited state. When excited unstable electron move back down into it's ground state it releases a light(photon). Absorb light Light emission e hν e Excited state Egap Ground state blue light: h = 3.1 eV red light: h = 1.7 eV Copper color https://www.youtube.com/watch?v=zrjhOH6yoXE

Luminescence (발광) Luminescence (emission of light by a material): material absorbs light at one frequency & emits at another (lower) frequency. Phosphorescence(인광) and fluorescence(형광) e phosphorescence & fluorescence: https://www.youtube.com/watch?v=dTllxNpxUfo

Fluorescence Lamps (형광등) Arc between electrodes excites mercury in lamp to higher energy level. Electron falls back emitting UV light (i.e., suntan lamp). Material Inner surface of glass absorbs UV and emits visible light Ca10F2P6O24 with 20% of F - replaced by Cl - Adjust color by doping with metal cations Sb3+ blue Mn2+ orange-red Flourescent lamps https://www.youtube.com/watch?v=td38NCj0MZ4 Neon Lights https://www.youtube.com/watch?v=zPDoBjlpxXY

OLED Organic Light-Emitting Diode (유기 발광 다이오드) A film of organic semiconductor emits light in response to an electric current. used for smartphone & television. LED & OLED https://www.youtube.com/watch?v=8quZrUcRFlw

Solar Cell (태양전지) Incident photon produces hole-electron pair. Typically 0.5 V potential. Current increases with light intensity. n-type Si p-type Si p-n junction light + - creation of hole-electron pair Solar cell https://www.youtube.com/watch?v=1gta2ICarDw

Refraction (굴절) Light is slower in a material vs vacuum Refractive index: n = c / v (velocity in vacuum/medium) Glasses 1.5 -1.7, Plastics 1.3 -1.6, Diamond 2.41 θ1 θ2 n1 n2   Light in glass: https://www.youtube.com/watch?v=JXC3mmITrCw

Optical Fiber (광섬유) Total refraction (전반사) An optical fiber is made of silica(glass) core surrounded by a cladding with a lower index of refraction. It transmits light between the two ends of the fiber. Refraction index Optical Fiber https://www.youtube.com/watch?v=0MwMkBET_5I

Polarized Light (편광) Light is polarized by a filter that allows only one direction of wave. Nonpolarized light vibrates in all directions Horizontal component pass through polarizer Polarized light Polarization http://www.youtube.com/watch?v=E9qpbt0v5Hw LCD monitor http://www.youtube.com/watch?v=jiejNAUwcQ8

Laser LASERS (Light Amplification by Stimulated Emission of Radiation) Laser emitting material is excited by flash lamp. Tune frequency by adjusting mirror spacing. CO2 & Nd:YAG high power lasers are used for industrial cutting & welding. Mirror Xenon Flashlamp Nd:YAG crystal Laser Laser cutting http://ma.gnu.ac.kr/vod/Machining/Laser_beam_machining.MP4

Interference (간섭) A double-slit interference experiment shows light is wave He-Ne Laser Interferometer λ=633 nm 1. Wave is divided 2. Returning wave is recombine Reference mirror Moving mirror Laser beam 3. Measures the superposition of the two waves traveled different paths λ/4 + Bright Dark Laser Interferometer http://www.youtube.com/watch?v=VyePASErr5Q