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Vladimir G. Niziev

NATIONAL UNITED UNIVERSITYMiao-li, Taiwan

Selected slides from course of lectures

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Head of laboratory

Institute on Laser and Information Technologies

RUSSIAN ACADEMY OF SCIENCES

Vladimir G. Niziev

Citizen of RUSSIA

1960 2005

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Making substitution

E(r,,z,t) ~ E(r,,z) exp(-it);H(r,,z,t) ~ H(r,,z) exp(-it) ; k=/c

Maxwell equations

E and H are vectors

.0c

4

c

1

,4,0c

1

Hj,EH

EHE

If a wave propagates in free space

external charges and currents are absent = 0, j = 0

.00c

1

,0,0c

1

H,EH

EHE

Wave equationE and H are vectors EE 2

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2 tc

1

HH 2

2

2 tc

1

0HH 2k

.00c

1

,0,0c

1

H,EH

EHE

0EE 2k 0EE 2k

Vladimir Niziev Lasers: basics, design, properties

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TEM00

TEM10

TEM20

TEM11

TEM21

TEM01 TEM02

TEM12

Laguerre – Gauss transverse modes of stable resonators for round mirrors

TEMp1 p = 0,1,2…

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t

Perfect temporal coherence

t

Wavefront

Direction of wave propagation

t t

“Bad” (limited) temporal coherence

Temporal coherence

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Perfect temporal coherence

“Bad” (limited) temporal coherence

Time of coherence

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E

The main reason of bad (limited) temporal coherence

Coherence

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Discharge pulse duration ~ 1 s

Laser pulse duration ~ 0.03 s

Time

Typical time of gas dynamic processes ~ 30 s

Variable delay time

Screen

Partial mirror Total mirror

Ruby laser Objective

Interferometry Mach-Zehnder interferometer

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Interferometry

Sound speed ~ 3104 cm/s

Time of formation of sound wave ~ 30 s

Size of heated region is ~ 1cm

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Lidar (detection of leakage in gas pipeline)

Gas pipeline Crack, leakage

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Cloud of detected gas

Lidar of differential absorption

Lidar

Ground surface

Laser

Detector

System of processing signals

Parabolic mirror

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Ek

P -polarizat ion

Reflectivity from surface

0 15 30 45 60 75 90

Angle of incidence, degrees

1.0

0.8

0.6

0.4

0.2

0.0

P-polarizat ion

Brewster angle

1

2nn

tg = Brewster angle

S-polarization

Ek

Fresnel law

OpticsOptics

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Linear amplification

Stationary state of inversion population. It is dynamic but not static

Pumping Spontaneous emission or/and collisions

Pumping

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Atom-photon interaction

Ene

rgy

Ground state

Excited state

Only resonance interaction is possible !

No excitation !No excitation !Excitation of atom

Atom in the ground state

Atom in the Atom in the excited stateexcited state

Isolated atomIsolated atomAtom’s state Atom’s state

is not changedis not changedSpontaneous Spontaneous

emission.emission.

Interaction with photons

Excitation of atom

Stimulated Stimulated emissionemission

Interaction Interaction with particles with particles

Atom excitation Atom excitation

in collisions in collisions

Atom relaxation Atom relaxation in collisionsin collisions

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100nm 200 300 400 500 600 700 nmULTRAVIOLET VISIBLE

800nm 900 1 m 3 10 30 100 1000 m

NEAR-INFRARED MID-INFRARED FAR-INFRARED

Nd:YAG laser

1064 1570 nm

2nd harmonic532 nm

3rd harmonic355 nm

4th harmonic266 nm

5th harmonic213 nm

Raman shifted1.39, 1.54, 1.91 m

Logarithmic scale

Crystal Flash lamp or diode lasers pumping Main wavelength 1064 nm Output power 1-1000 Watts CW, pulse, pulse periodic

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Damage of eyes by laser radiation

The range of wavelength

Direct hit of laser beam to eyes is very dangerous

VISIBLEULRAVIOLET INFRAREDULRAVIOLET INFRAREDVISIBLE

Safety first !

19Computer model

Military planeDrafts

Plastic copy

Laser stereo lithography

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Laser stereo lithography

Resolution is 10 m

Micro models

21Operation on heart

Transmyocardial revascularization (scheme of procedure)

Lasers for cardio surgery

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