The solid-state laser - A 50 year old light bulb Fredrik Laurell, Laser Physics group, Applied Physics Department, KTH

Lasers - in the Solid State What ? How ? Where and why ?

Outline Outline Background and history Diode laser concepts Compact stable tailored lasers Diode-pumped Solid-state Lasers Fiber lasers Tailoring DPSSL and fiber lasers Conclusions

Basic Laser Laser medium Resonator Pump Atoms in a matrix Energy diagram for a laser stimulated emission

i.e. the concept of Stimulated emission

Laser history Einstein introduces quantum transitions 1924 Tolman suggests amplification via stimulated emission 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 it is a very unlikely process

a ruby rod, mirros deposited on the end-faces and a flash lamp Maiman had to fabricate everything himself Absorption and emission for Cr3+

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 ... What lasers do we have today?

Choosing the Laser Medium 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

A 2 kW CO2 Laser

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

The diode laser The diode laser and the optical 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

Types of diode lasers Edge emitters Array lasers Broad area diodes Tapered diodes

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).

Solving the spectral problem Grating stabilization – feed-back Fiber Bragg Gratings Diffraction gratings Volume Bragg Gratings Integrated gratings

Tuning the diode – alternative feed-back techniques Stretching the FBG Temperature tune or translating a chirped VBG Retroreflector = continuous tuning

Diode laser tuning with strechable silicone grating Moulded silicone grating Littrow configuration O2 sensing in air Laser tunable over 3 nm 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

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 Solid- State Material Functional element Diode Pump Allows functionality to be integrated in the laser

DPSSL scales to high power heat laser pump Minimize the quantum defect – i.e. heat