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

2. OCW
Lens production: Light Reflection Refraction: OLED Process Samsung Is radiation dangerous (TED 5min)

3. KOCW
재료의 광학적 성질1 재료의 광학적 성질2

4. 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:

5. 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:

6. 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

7. 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:

8. 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
Sb blue
Mn2+ orange-red
Flourescent lamps
Neon Lights

9. 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

10. 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

11. Refraction (굴절) Light is slower in a material vs vacuum
Refractive index: n = c / v (velocity in vacuum/medium)
Glasses , Plastics , Diamond 2.41 θ1 θ2 n1 n2
Light in glass:

12. 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

13. 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
LCD monitor

14. 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

15. 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