Optics and Photonics

Selim JochimMPI für Kernphysik und

Uni HeidelbergEmail: selim.jochim@mpi-hd.mpg.de

Website for this lecture: www.mpi-hd.mpg.de/ultracold/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 here:– 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:• 20.4. geometric optics, rays

• 27.4. wave optics, gaussian beams,

• 4.5. fourier optics, holography

• 11.5. Polarization, linear, circular birefringence

• 18.5. Optical coatings, wave guides, fibers ...

• 25.5. Atom-photon interactions

Contents II

• 1.6. Lasers: principle, optical resonators, eigenmodes

• 8.6. More lasers, solid state lasers, dye lasers, etc.

• 15.6. Pulsed lasers: Q-swtiching, mode locking, extremely short pulses

• 22.6. Semiconductor photonics: detectors, LEDs, Lasers

• 29.6. Nonlinear optics concepts

Contents III

• 6.7. Nonlinear optics applications: Frequency doubling, mixing ...

• 13.7. Advanced applications: Frequency comb, optical synthesizer ...

• 20.7. accoustooptical and electrooptical tools: AOM EOM etc.

• 27.7. Reserved for special topics, extra time that certain subjects may require

Recommended literature

• Davis: Lasers and Electro-Optics: Fundamentals and Engineering

• Saleh, Teich: Fundamentals of Photonics

• Demtröder: Laserspektroskopie

• Hecht, Optics (Especially the first few lectures)

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

Reflection and Refraction

• Easily derived from Fermat’s principle

Parabolic mirror

Parallel beams are focused onto a single spot:

Car headlight!

Spherical mirror

Paraxial rays:Close to optical axis, rays will be 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

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:

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 ….

Where 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