Development of optical concentrator systems for directly solar pumped laser systems [Elektronische Ressource] / von Yasser Abdel-Fattah Abdel-Hadi

Yasser Abdel-Fattah Abdel-Hadi

Development of optical concentrator systems for directly
solar pumped laser systems

Technical University of Berlin
Institute of Optics
2005
D 83





Development of optical concentrator systems for
directly solar pumped laser systems

von

Yasser Abdel-Fattah Abdel-Hadi, M.Sc.

aus Kairo, Ägypten




Fakultät II - Mathematik und Naturwissenschaften
der Technischen Universität Berlin
zur Verleihung des akademischen Grades
Doktor der Naturwissenschaften
Dr.rer.nat

genehmigte Dissertation








Berlin 2005
D 83


































Tag der wissenschaftlichen Aussprache: 22.12.2005



Berichter: Prof. Dr. –Ing. Adalbert Ding
Berichter: Dr.-Ing. Hans Joachim Eichler
Vorsitzender: Prof. Dr. Erwin Sedlmayr














To the souls of my parents I present this work…

They wanted to be happy to see this work finished…

But they died before it…

I think they are now happy to see it finished…

I also present this work to my home country Egypt
and to Germany…

Yasser



Abstract




Two new solar directly-pumped solid state laser systems were developed to avoid the
disadvantages of the previously developed system.

Using the advantages of the Fresnel lenses, a small solar directly-pumped laser system
was developed. This system consists of a rectangular Fresnel lens as a primary concentrator,
a secondary concentrator and the laser cavity. A slab laser of the type of Nd:YAG laser was
firstly used. For this laser, a collimator convex lens was used as a secondary concentrator.
Another laser rod of the type of Nd:YVO was used. For this laser, a new non-imaging 4
concentrator of the type of Compound Spherical Concentrator (CSC) was used as a secondary
concentrator. The system was constructed on an astronomical mount to track the sun during
the day.

A medium-scale mirror-array concentrator using a system of 105 flat mirrors of the
dimensions 15 cm × 15 cm was developed. The mirrors were organised in three rows. Each
row had seven panels. Each panel carried five mirrors. Six electro-mechanical computer-
controlled motors were used to let the system track the sun during the day. Three of these
motors were responsible for the tracking in the vertical component (altitude of the sun). The
other three motors were responsible for the tracking in the horizontal component (azimuth of
the sun). The mirrors were contolled through these motors in order to result a single fixed
reflected image of the whole system during the day. An additional Fresnel lens was used to
increase the concentration ratio of the whole system.

The measurements of the both systems were taken in the Technical University of
Berlin (Germany). These measurements showed promising results which can lead to
substitute systems which use the large parabolic- or hyperbolic dish concentrators.
I
Abstract in German

Abstrakt




Neue optische Solarkonzentratoren zum Einsatz in Festkörper-Lasersysteme wurden
entwickelt.

Unter Verwendung von großflächigen Fresnellinsen wurde ein kleines direkt-
gepumptes Lasersystem entwickelt. Dieses System besteht aus einer Fresnellinse, einen
Sekundärkonzentrator und einer Laserkavität.

Für das erste System wurde eine asphärische Linse als Sekundärkonzentrator
verwendet, womit ein Nd:YAG Slab-Kristall gepumpt wurde.

Für das zweite System wurde ein monolithischer, nicht abbildender sphärischer
Konzentrator (CSC) als Sekundärkonzentrator eingesetzt, der einen Nd:YVO Stab, der in 4
eine Keramikkavität eingesetzt war, transversal pumpte.

Für Lasersysteme mittlerer Leistung wurde ein System bestehend aus Primär- und
Sekundär-Konzentratoren sowie Kavität entwickelt. Der Primärkonzentrator war ein
Steuerbares Vielspiegelarraysystem bestehend aus 105 quadratische Spiegeln (15 cm × 15
cm). Die Spiegel sind in 3 von einander unabhängigen Gruppen unterteilt, die mit je 2
Motoren (für die vertikale und horizontale Bewegung der Gruppe) eingestellt werden können.
Jede Gruppe besteht aus 7 Panelen mit je 5 vereingestellte Spiegeln. Die Spiegel wurden so
justiert, dass die Sonnenstrahlung auf einen Fleck minimaler Dimensionen konzentriert
wurde. Eine zusätzliche Fresnellinse wurde verwendet, um die Konzentration des System zu
erhöhen.
II
Contents




Abstract......................................................................................................................................I

Abstract in German ................................................................................................................ II

Contents........... III

Chapter 1: Introduction........................................................................................................... 1
1.1 The inspiration of the issue .................................................................................................. 1
1.2 Why Solar Laser?................................................................................................................. 2
1.3 Solar laser as a possible selection ........................................................................................ 5
1.4 Sun and solar radiation energy............................................................................................. 7
1.4.1 The sun .............................................................................................................................. 7
1.4.2 The sun-earth geometry..................................................................................................... 7
1.5 Solar radiation outside the earth's atmosphere ..................................................................... 8
1.5.1 The solar constant.............................................................................................................. 8
1.5.2 Spectral distribution of extraterrestrial radiation .............................................................. 9
1.5.3 Variation of extraterrestrial radiation.............................................................................. 10
1.6 Solar radiation at the earth’s surface .................................................................................. 11
1.7 Solar radiation over Egypt.................................................................................................. 12
1.8 Solar laser techniques......................................................................................................... 14
1.9 Comparison between different pumped lasers ................................................................... 15
1.10 Types of direct solar laser pumping ................................................................................. 17
1.11 Solar laser in space........................................................................................................... 20
1.12 Previous work................................................................................................................... 23
1.13 The aim of the project ...................................................................................................... 28

Chapter 2: Theory of Lasers ................................................................................................. 29
Overview .................................................................................................................................. 29
2.1 Introduction ........................................................................................................................ 29
2.2 Emission and Absorption of radiation................................................................................ 30
2.3 The Einstein relations......................................................................................................... 32
2.4 Absorption and Stimulated Emission of radiation ............................................................. 34
2.5 Population inversion........................................................................................................... 38
2.5.1 Attainment of a population inversion.............................................................................. 38
2.6 Optical feedback................................................................................................................. 40
2.7 Threshold condition - laser losses ...................................................................................... 42
2.8 Lineshape function ............................................................................................................. 44
2.9 Populati