Transcript Adopt_lecture_F_Laurell_part1.ppt i Powerpoint-format (9,4 MB)

The solid-state laser
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A 50 year old light bulb
Fredrik Laurell, Laser Physics group, Applied Physics Department, KTH
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Lasers - in the Solid State
• What ?
• How ?
• Where and why ?
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Outline
Outline
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Background and history
Diode laser concepts
Compact stable tailored lasers
Diode-pumped Solid-state Lasers
Fiber lasers
Tailoring DPSSL and fiber lasers
Conclusions
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Basic Laser
• Laser medium
• Resonator
• Pump
Atoms in a matrix
Energy diagram for a laser
stimulated emission
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i.e. the concept of Stimulated emission
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Laser history
1916 Einstein introduces quantum transitions
1924 Tolman suggests amplification via stimulated emission
it is a very unlikely process
1920- 50 Quantum mechanics, atomic and microwave physics
1954
first MASER
1959
acronym LASER was introduced
Schawlow: ”ruby is not a good laser candidate”
1960
Maiman realize the ruby laser
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a ruby rod, mirros deposited on the end-faces and a flash lamp
Maiman had
to fabricate
everything
himself
Absorption and emission for Cr3+
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What lasers do
we have today?
Gas lasers
Dye lasers
Solid-state lasers;
Ruby, Nd:YAG, Ti-Sapphire
Diode-pumped solid-state lasers
Thin disc laser
Fiber laser
Semiconductor laser
Free electron lasers
...
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Choosing the Laser Medium
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Gas
Liquid
Solids
Crystals
Semiconductor
Glass
Fiber
Dye in gelatin
...
Finding the right atom and
matrix by Spectroscopy
1. Absorption
2. Emission/ Fluorescence
3. Lifetime of energy levels
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A 2 kW CO2 Laser
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Laser History - continued
• 60-ties laser invented and most effects discovered
• 70-ties a solution looking for a problem ...
• 80-ties problems discovered!
• 90-ties commercial success!!
• 00-ties everybodies toy!!!
Diode Pumped Solid-state lasers (DPSSL)
Fiber lasers
Diode lasers
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The diode laser
the smallest and most frequently used laser
The diode laser and the optical
fiber is the backbone of
telecommunication
Nobel prize 2000 Zhores I. Alferov
A.F. Ioffe Physico-Technical Institute, St. Petersburg
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Types of diode lasers
• Edge emitters
• Array lasers
• Broad area diodes
• Tapered diodes
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Types of diode lasers -continued
• VECSELs – OPSL
A vertical-external-cavity surface-emitting-laser (VECSEL)
is a small semiconductor laser similar to a
vertical-cavity surface-emitting laser (VCSEL).
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Solving the spectral problem
Grating stabilization – feed-back
Diffraction gratings
Fiber Bragg Gratings
Volume Bragg Gratings
Integrated gratings
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Tuning the diode
– alternative feed-back techniques
Stretching the FBG
Temperature tune or translating a chirped VBG
Retroreflector
= continuous tuning
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Diode laser tuning with strechable silicone grating
Moulded silicone grating
Littrow configuration
O2 sensing in air
Laser tunable
over 3 nm
 FWHM  310MHz
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S Bertani, B Jacobsson, F Laurell, V Pasiskevicius and M Stjernström, Opt. Express, 14, 11982, 2006.
Increasing the Power- Resonant Cavities
Resonant cavities require
advanced locking techniques
W. Risk, Compact Blue-Green Lasers
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The Diode-Pumped Solid-State Laser
Converts a poor diode laser beam to a high quality solid-state laser beam
- spatially, spectrally and temporally engineered
Diode
Pump
SolidState
Material
Functional
element
Allows functionality to be integrated in the laser
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DPSSL scales to high power
heat
pump
laser
Minimize the quantum
defect – i.e. heat
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