레이저 분광학

(1)

Nonlinear Optics Lab

Nonlinear Optics Lab.

.

HanyangHanyang Univ.Univ.

레이저 분광학

(Laser Spectroscopy)

(2)

.

분광학

fluorescence / scattering

transmission / absorption incident light

sample

; 광과 물질과의 상호작용의 결과로 나타나는 광의 특성 변화를 분석

(3)

.

분광학 정보

- Wavelength : energy levels of atomic system - Line intensity : transition probability

- Natural linewidth : mean lifetime of excited states - Doppler width : velocity distribution (temperature)

- Pressure broadening/shift : collision/interatomic potential - Zeeman / Stark splitting : magnetic/electric moments

λ₁ λ₂ λ

λ₁ λ₂

energy level & transition spectrum

(4)

.

레이저 분광학의 장점

- High power density : reduce noise, nonlinear spectroscopy - Directionality : multiple pass(sensitive detection)

- Monochromaticity : high spectral resolution - Short pulse laser : transient behavior

레이저 분광학의 응용

- Measurement of Atomic/molecular constants

: Atomic/molecular physics, Condensed matter physics, Biomedical optics, Plasma physics, Isotope separation, Pollution detection, …

- Light-matter interaction

: New spectroscopic technique, Manipulation of photon ÎQuantum optics, Optical information processing, …

(5)

.

레이저 분광학

- Doppler-limited absorption and florescence spectroscopy

- Sub-Doppler laser spectroscopy(nonlinear laser spectroscopy) - Time-resolved laser spectroscopy

- Advanced spectroscopy

(6)

.

Doppler-limited absorption and florescence spectroscopy

- Absorption spectroscopy - Excitation spectroscopy - Photoacoustic spectroscopy - Optogalvanic spectroscopy - Ionization spectroscopy

- Laser magnetic resonance/Stark spectroscopy, - Multiphoton spectroscopy, …

(7)

.

Absorption spectroscopy

(8)

.

Excitation spectroscopy

(9)

.

Photoacoustic spectroscopy

(10)

.

Optogalvanic spectroscopy

(11)

.

Ionization spectroscopy

(12)

.

Sub-Doppler laser spectroscopy

- Saturation spectroscopy - Polarization spectroscopy - Multiphoton spectroscopy, …

(13)

.

Saturation spectroscopy

(14)

.

LD

BK-7

bare glass M

variable attenuator

λ/2 or λ/4 wave plate

BK-7

bare glass Helmholtz

coils(3-pairs)

B/S

-

+

photodiode

data acquisition 852 nm

example

(15)

.

0 100 200 300 400 500 600

(d) (c)

(a) _(3,2) _(3,3) _(3,4)

(b)

relative frequency [MHz]

0 100 200 300 400 500 600

(d)

relative frequency [MHz]

(c) (b)

(4,5) (4,4)

(4,3)

(a)

F=4 -> 3, 4, 5

lin||lin

lin lin

F=3 -> 2, 3, 4

σ⁺σ⁺ σ⁺σ^-

(16)

.

Polarization spectroscopy

(17)

.

Multiphoton spectroscopy

(18)

.

Time-resolved laser spectroscopy

fs Ti:sapphire laser system

Mode-locked pulse

(19)

.

Pump-probe spectrum of InGaAs Nano structure processing

(20)

.

Advanced spectroscopy

- EIT(electromagnetically induced transparency) - Laser cooling

…

(21)

.

EIT(electromagnetically induced transparency)

- Optical pulse manipulation

- Quantum information processing - Nonlinear optics

- Single photon switching

…

(22)

.

빛을 멈추다

CQCC B.S. Ham

Nature 409, 461 (2001)

1. In cold atoms, C. Liu et al.,

Nature 409, 490 (2001)

2. In atomic vapors, D. Philips et al., PRL 86, 783 (2001)

3. In solids,

A. Turukhin et al.,

• PRL 88, 023602 (2002) 빛 멈춤 실험관측

(23)

.

Laser cooling

- High resolution spectroscopy - BEC

- Atomic optics / interferometry - Atomic layer deposition

…

(24)

.

Bose-Einstein Condensation

A series of 140 overlapping pulses form a continuous, well-collimated atom laser beam. (6 cm/s)