optics and photonics selim jochim together with dr. k. simeonidis mpi für kernphysik und uni...
TRANSCRIPT
Optics and Photonics
Selim Jochim together with Dr. K. SimeonidisMPI für Kernphysik und
Uni HeidelbergEmail: [email protected]
[email protected] for this lecture:
www.lithium6.de teaching
What will you learn in this course?
• How to use advanced photonics instruments and technology in the laboratory
• Learn to develop your own ideas on how to make use of photonics for (precision) experiments
• Knowlegde that is widely needed in many labs in Heidelberg:– Biomedical research– Laser spectroscopy– High-power “ultrafast” lasers for atomic physics– Laser cooling and trapping, (quantum) manipulation of
atoms, molecules or ions
Motivation
• We make (increasingly) heavy use of photonics in our daily life. Two interesting examples:
• Green laser pointers emit bright light at 532 nm: How are they made? make use of almost anything you will learn in this course!!
• DVD reader/writer ( resolution of a microscope for a few €!!)
Contents
Preliminary list:
• 11.4. Geometric optics, rays (Fermat’s principle)
• 18.4. No class
• 25.4. Wave optics, gaussian beams (paraxial Helmholtz eq.)
• 2.5. Polarization optics, optical coatings, wave guides, …
• 9.5. Atom-photon interaction
• 16.5. Lasers: Light amplification
• 23.5. Laser oscillation, optical resonators
Contents II
• 30.5. More lasers, solid state lasers, dye lasers, etc.
• 6.6. Pulsed lasers: Q-switching, mode locking, extremely short pulses
• 13.6. Semiconductor photonics: detectors, LEDs, Lasers
• 20.6. Fourier optics, holography
• 27.6. Nonlinear optics concepts
• 4.7. Nonlinear optics applications: Frequency doubling, mixing ..
• 11.7. Advanced applications: Frequency comb, optical synthesizer ...
• 18.7. Lab tour(s)
Recommended literature
• Saleh, Teich: Fundamentals of Photonics
• Kneubühl, Sigrist: Laser
• Davis: Lasers and Electro-Optics: Fundamentals and Engineering
• Demtröder: Laserspektroskopie
• Hecht, Optics (Especially for the first few lectures)
1. Geometric (ray) optics
• Light propagates as rays with “speed of light”, c in vacuum
• In a medium, the light is slowed down by the refractive index n
• In an inhomogeneous system, propagation is governed by Fermat’s principle:
“Minimize” optical path length: ( )d 0B
A
n s r
Fermat’s principle
Phenomenologically:
• Hero of Alexandria (ca. 70 – 10 A.D.): Light always takes the shortest path when reflected from a surface:
Refraction
1 2
2 1
sin sin
n n
A
B
Interfaces between dielectrics …
• n2>n1 …
• Total internal reflection ….
critical angle:
2
1
arcsin( )C
n
n
Where total internal reflection is used
• Prisms, e.g. binoculars, camera viewfinder
• Optical fibers:
Parabolic mirror
Parallel beams are focused onto a single spot:
Car headlight!
Spherical mirror, paraxial rays
Paraxial rays: Assume that all beams propagate “close” to optical axis. In most cases, this means that sin ≈ tan ≈ Rays are focused toF=R/2
Imaging with spherical mirrors
1 2
1 1 1 1
2z z R f
Thin lenses
1 2
1 1 1( 1)( )n
f R R
Paraxial imaging
1 2
1 1 1
z z f 2
2 11
zy y
z
Magnification
Matrix formalism for parax. rays
• Use it to describe a complex optical system with a single (2,2)-matrix
• Define state of a ray by a 2-comp. vector:
valid if
Example matrices
• Free space propagation
• Refraction at a surface
Optical system ….
When the paraxial approx. fails …
Focussing of a laser beam:
Minimize non-paraxial distortions:
Plano-convex lens, also “best form lens”
Spherical aberration …
• Can we make all parallel rays incident on a lens end up in a single spot??
Aspheric lens?
• Optical path length should be the same for all angles ….
Aspheric lenses
• All kinds of quality grades available
• Molded, plastic material
Precision machined …
ASPHERIC LIMITS
STANDARD
HIGH PRECISION
Diameter (mm) 15-120 15-120
Length (mm) 10.5-85 10.5-85
Width (mm) 10.5-85 10.5-85
Dimensional Tolerances (µm)
25 5
Center Thickness Tolerance (µm)
100 35
Wedge Tolerance (µm)
75 25
Surface Quality 60-40 10-5
Radius Limits (mm) LRC Limited
LRC Limited
Concave >30.0 >30.0
Convex >5.0 >5.0
Radius Tolerance (%)
0.1 0.05
Total SAG (mm) <25 <25
Aspheric Surface Accuracy (wave)
1/4 1/10