Transcript Snímek 1

Joint International Physics Summer School
Insubria University (Como) – Palacky University (Olomouc)
Optics
Fundamentals of lasers
Jan Soubusta
Olomouc - 25 agosto 2015
OUTLINE
1. What is laser?
2. Basic classification of lasers
3. Why are we interested in lasers?
4. Useful unique properties of lasers
OUTLINE
1. What is laser?
2. Basic classification of lasers
3. Why are we interested in lasers?
4. Useful unique properties of lasers
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
1.1 The easiest construction of a laser
What has to be inside?
http://toutestquantique.fr/, http://video.online-convert.com/
1.1 The easiest construction of a laser
semitransparent mirror
pumping
100% reflective mirror
output laser beam
active media
1.2 Laser generated colors
• two mirrors compose a resonator
• the resonator supports only
a discrete spectrum of colors
Typical optical frequency :
≈ 5 x 10 14 Hz
intensity
wavelength
frequency
The color of the laser is
determined by the energy levels
of the active media
frequency
Colors of the active media
Excimer
ArF, KrF
Noble gases He-Ne
Ar+
Kr+
Solid-state
193 nm, 248 nm
633 nm
455 nm, 515 nm, 529 nm
413 nm, 531 nm, 647 nm
Ruby
694 nm
Ti:saphire 800 nm
Nd:YAG
1064 nm
Tunable lasers
• useful for spectroscopy
• testing specific atoms interactions
• for medical technologies
Ekspla ns laser tunable
in range 210 – 2600 nm
photoluminnescence
spectroscopy
OUTLINE
1. What is laser?
2. Basic classification of lasers
3. Why are we interested in lasers?
4. Useful unique properties of lasers
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
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
OUTLINE
1. What is laser?
2. Basic classification of lasers
3. Why are we interested in lasers?
4. Useful unique properties of lasers
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
3.1 Typical applications of lasers
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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
3.2 Where are the lasers used today?
Bono's laser jacket during U2's 360 Rose Bowl concert
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factory
laboratory
education
hospital
telecommunications
• home
• laser games
• laser shows
OUTLINE
1. What is laser?
2. Basic classification of lasers
3. Why are we interested in lasers?
4. Useful unique properties of lasers
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
 broad spectrum of transform-limited
fs pulses
 high spatial coherence
allows collimation or focusing
(diffraction-limited)
WARNING !!
4.1 High power or high peak energy
Where we need extreme energy?
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nonlinear optics
material processing (drilling, cutting)
new materials development and testing
particle acceleration by laser
laser pulse generation of ultrashort
X-ray pulses
• plasma physics, exotic physics
• military purposes
4.1 High power or high peak energy
Where we appreciate enough intensity?
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CD and DVD R/W technologies
laser printers, copiers
sensors
precise position and motion control
medical devices
laser games
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
4.2 Favorable spectrum
Where we need narrow spectrum?
optics communications
spectroscopy
interferometry
photoluminnescence
spectroscopy
interference
4.3 High spatial coherence
• diffraction limited collimation
• focusing to very small spot
Incoherent light collimation limit
Θ=w/F
Laser collimation limit
Θ = λ / 2w
4.3 High spatial coherence
Why we need so fine focusing?
high capacity of CD and DVD
fine laser printing
precise cutting and drilling
or precise medical surgery
Laboratory activities
#4 Lasers
#4A Laser cutting (Hana Chmelíčková)
Students will 1) work with pulsed Nd:YAG laser system, which is capable to
drill, cut or weld different samples.
2) will be programming the computer controlled sample movement, that
allows cutting of 2D objects from different materials.
3) can design and cut their own smiley pictures from a metal plate.
Thank you for your attention !
The End