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

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

OUTLINE What is laser? Basic classification of lasers Why are we interested in lasers? 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 a LASER? http://toutestquantique.fr/, http://video.online-convert.com/

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

Colors of the active media Semiconductors

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

OUTLINE What is laser? Basic classification of lasers Why are we interested in lasers? 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 Extreme Light Infrastructure

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 What is laser? Basic classification of lasers Why are we interested in lasers? 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 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? Everywhere Bono's laser jacket during U2's 360 Rose Bowl concert factory laboratory education hospital telecommuni- cations home laser games laser shows

OUTLINE What is laser? Basic classification of lasers Why are we interested in lasers? 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 high spatial coherence allows collimation or focusing (diffraction-limited)

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

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

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

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

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

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)

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 50 3000 25 25 G64 X 50 800 600 600 G63 Y 50 3000 25 25 G64 Y 50 800 600 600 …………..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

Thank you for your attention ! The End