1. Fundamentals of lasers
Joint International Physics Summer School
Insubria University (Como) – Palacky University (Olomouc)
Optics
Fundamentals of lasers
Jan Soubusta
Olomouc - 29 agosto 2017

2. OUTLINE What is laser? Basic classification of lasers
Why are we interested in lasers?
Useful unique properties of lasers

3. OUTLINE What is laser? Basic classification of lasers
Why are we interested in lasers?
Useful unique properties of lasers

4. 1.What is laser?
Light Amplification by Stimulated Emission of Radiation
1917 : Albert Einstein performed needed theoretical foundations
1960 : Theodore H. Maiman (California)
the first laser based on ruby crystal : λ = 694 nm
1962 : Robert N. Hall
the first laser diode, GaAs and λ = 850 nm
1963 : Karel Pátek (born in Přibyslav)
the first laser in Czechoslovakia, Nd:glass, λ = 1064 nm
Nowadays : many types of lasers
gas, chemical, excimer, solid-state,
fiber, photonic crystal,
semiconductor, dye
and other exotic media

5. 1.1 The easiest construction of a laser
What has to be inside a LASER?

6. 1.1 The easiest construction of a laser
100% reflective mirror
pumping
semitransparent mirror
output laser beam
active media

7. Colors of the active media
Semiconductors

8. Tunable lasers useful for spectroscopy
testing specific atoms interactions
for medical technologies
photoluminnescence
spectroscopy
Ekspla ns laser tunable
in range 210 – 2600 nm

9. OUTLINE What is laser? Basic classification of lasers
Why are we interested in lasers?
Useful unique properties of lasers

10. 2. Basic classification of lasers
CW : continuous wave lasers
continuous power in range from mW to MW
Pulsed : ns, ps or fs lasers
pulse energy in range from mJ to 300 J
Extreme
Light
Infrastructure

11. Femtosecond lasers provide short pulses and broad spectrum
ns laser : narrow spectrum nearly continuous
1 ps laser : length 0.3 mm (500 waves)
20 fs laser : length 6 μm (8 waves)
transform-limited : minimum possible duration for
a given spectral bandwidth

12. OUTLINE What is laser? Basic classification of lasers
Why are we interested in lasers?
Useful unique properties of lasers

13. 3. Why are we interested in lasers?
provide strong light (high power)
light with unique properties
enabled construction of
a new devices
improved existing devices

14. 3.1 Typical applications of lasers
barcode readers
CD and DVD R/W technologies
laser printers, copiers
material processing (drilling, cuting)
holography, speckles
sensors, precise position and motion control
fiber-optic communications
medical and military devices
laser games

15. 3.2 Where are the lasers used today?
Everywhere
Bono's laser jacket during U2's 360 Rose Bowl concert
factory
laboratory
education
hospital
telecommuni-
cations
home
laser games
laser shows

16. OUTLINE What is laser? Basic classification of lasers
Why are we interested in lasers?
Useful unique properties of lasers

17. 4. Useful unique properties of lasers
extreme power of laser light
monochromatic continuous light
or broadband short pulses
monochromatic cw laser light has
high temporal coherence
high spatial coherence
allows collimation or focusing
(diffraction-limited)

18. 4.1 High power or high peak energy
Where we need extreme energy?
nonlinear optics
material processing (drilling, cutting)
WARNING !!

19. 4.2 Favorable spectrum CW laser can generate monochromatic light
one color → high temporal coherence
white light (bulb) : 400 nm spectral width
sodium lamp (one line) : 589 nm, spectral width <1nm
(Δf ≈ 800 MHz)
gas laser : typical Kr laser at single frequency
413 nm, Δλ ≈ 10-6 nm, Δf ≈ 1 MHz
Δf ≈ 1/τ
380 nm
400 nm
780 nm
800 nm

20. 4.3 High spatial coherence
diffraction limited collimation
focusing to very small spot
Incoherent light collimation limit
Laser collimation limit
Θ = w / F
Θ = λ / 2w

21. #4A Laser cutting (Hana Chmelíčková)
Laboratory activities
#4 Lasers
#4A Laser cutting (Hana Chmelíčková)

22. 1) SAFETY FIRST - Verification of the laser pointers class II
Are all laser pointers safe ?
Power of three different laser pointers will be measured by means of the photodiode sensor and laser beam 3D profile will be analyzed by camera system

23. 2) LASER CUTTING – Test of laser parameters
What are the optimal process parameters for laser cutting ?
Different thickness and kinds of thin metal sheets will be cut with industrial laser cutting system, dimensions of cut width and quality of edges will be measured and evaluated by means of camera system in laser processing head.
v…speed, R…reflexivity, P…laser power, D…laser beam diameter, h…material thickness, matE…energy density (J/m3)

24. 3) SPL Repeater – tool for programming of the required shape
How can I edit CNC program ?
Teaching set of instructions for X,Y linear axis motion, droved by servo electromotor, design, edit and test program by means of SW SPL Repeater, then cutting required shape on the laser
G12 3
G63 X
G64 X
G63 Y
G64 Y …………..speed of axis in 0,01 mm/s
G00 X0 Y0…………………………move without laser ON
G00 X2461 Y923; lips
G12 1………………………………open gas
G12 0………………………………open laser
G04 300……………………………time delay for piercing
G01 X2558 Y824………………….linear motion
G02 X1572 Y1812 A2226………...circular CW motion
G01 X562 Y850
G02 X661 Y944 A433
G01 X761 Y1039
G03 X1572 Y1812 A1786…………circular ACW motion
G01 X2364 Y1020
G02 X2461 Y923 A433
G12 3………………………………gas and laser OFF ….
G12 7………………………………end of program
M30………………………………..end of program

25. Thank you for your attention !
The End