Chap. 6. Optical Properties Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Incident beam [irradiation] : absorption, reflection, transmission [Filtering of Transmission] Effect of nanoparticles: distributions of non-agglomerated nanoparticles in a polymer are used to tune the index of refraction. [Optical Properties]

Chap. 6. Optical Properties Excitation[pumping] and emission of photon[light]: in pumping process needs energy absorption. [Absorption vs. Emission] [Pumping process] In falling process, photon (light) is emitted:  [nm] = hc / E = 1240 / E [eV] Wavelength of visible light = 400~800 nm [ 3.1 ~ 1.5 eV] [Energy ~ Wavelength ]

Chap. 6. Optical Properties Light : both properties of wave and particle Therefore, relationship of Energy == Wavelength Wavelength of light:  [nm] = hc / E = 1240 / E [eV] [Energy ~ Wavelength ]

Chap. 6. Optical Properties Color and polarization [polarized light]; Color: reflected light from matter  leaf, sky Polarized light: specially selected light  LCD White light White light polarizer polarized light [Color and Polarization ]

Chap. 6. Optical Properties Principle of LCD (liquid crystal display): light valve on each pixel. pixels [Efficiency of passing light through polarizer] Reduction in intensity [Transverse wave] [LCD and Polarization ]

Chap. 6. Optical Properties Principle of LED: light emission from p-n junction Eg Wavelength of light:  [nm] = hc / E = 1240 / Eg [eV] Eg of Emission layer[InGaN]  wavelength of light [LED and Color]

Chap. 6. Optical Properties Refractive index n: greater than 1 [from 1.0 ~ 2.0] [OFC] Speed of light ~ wavelength of light determine refraction angle] [refraction index]

Chap. 6. Optical Properties Snell's law of refraction): describe between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air. Refraction of light at the interface between two media of different refractive indices, with n2 > n1. Since the velocity is lower in the second medium (v2 < v1), the angle of refraction θ2 is less than the angle of incidence θ1;  that is, the ray in the higher-index medium is closer to the normal. : [스넬의 법칙] [refraction index]

Chap. 6. Optical Properties Principle of Optical-fiber communication: light transport without energy loss. n1 n2 Creation of critical incident angle: n(2) > n(1) [Core materials] [optical fiber communication and refraction index]

Chap. 6. Optical Properties [Homework #6] / Due date: before next class Describe the relationship between energy change[E] and wavelength[] during de-excitation process. How about visible light in terms of energy and wavelength? 2. Describe operational principle of LCD. 3. Describe operational principle of LED. 4. Describe operational principle of optical-fiber communication