Changing the face of diffractive optical design methods through questioning whether we succeed by working together or by going it alone.  Each one of us in this community has special talents and strengths.  Many of us are competitors and share the same goal; designing more effective solutions for laser beam shaping.  This section is dedicated to developing a cooperative relationship by sharing published design methods, tricks of the trade and new variations of modified algorithms. “If I have seen further it is by standing on the shoulders of giants” – I. Newton.

 Refractive statistical concave 1D diffusers for laser beam shaping 

Paper 7062-25  
Author(s): Roland Bitterli, Toralf Scharf, Hans Peter Herzig, Univ. of Neuchâtel (Switzerland); Andreas Bich, Christine Dumouchel, Sylvain Roth, Kenneth J. Weible, Reinhard Völkel, SUSS MicroOptics SA (Switzerland)

 
Abstract

Certain high power laser applications require thin homogeneous laser lines. Diffusers can be used to improve the homogeneity.
We have fabricated diffusers made of fused silica for wavelengths between ultraviolet and near infrared that diffuse only in one direction.
The concept is based on arrays of concave cylindrical microlenses with locally varying size and position following a well defined statistical distribution.
We discuss the optical characteristics of the fabricated devices and propose a model to simulate the influence of the fabrication and design parameters on the device performance.     

       
Stochastic tandem microlens arrays for beam homogenization 

Paper 7062-26  
Author(s): Frank C. Wippermann, Daniela Radtke, Peter Dannberg, Uwe-Detlef Zeitner, Andreas H. Bräuer, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)


Abstract

Fly’s eye condensers are commonly used for the beam shaping of an arbitrary input intensity distribution into a top hat. The setup usually consists of a Fourier lens and two identical regular microlens arrays - often referred to as tandem lens array - where the second one is placed in the focal plane of the first microlenses. We propose a new concept for fly’s eye condensers incorporating a stochastic tandem microlens array for the generation of an intensity far field distribution with improved homogenization under coherent illumination with the envelope of a top hat. The influences of the variance of the lens parameters, the number of illuminated lenses and the numerical apertures of the lenses on the homogenization results are discussed. Measurements obtained at first prototypes fabricated by laser lithography and a subsequent uv-replication are presented. 

       
Randomly varying micro-optical elements for the generation of uniform intensity profiles in coherent laser sources 

Paper 7062-27  
Author(s): Kenneth J. Weible, Andreas Bich, Sylvain Roth, Christine Dumouchel, Pascal Pernet, Martin Eisner, Reinhard Voelkel, SUSS MicroOptics SA (Switzerland); Roland Bitterli, Toralf Scharf, Wilfried Noell, Univ. de Neuchâtel (Switzerland)

 
Abstract

Micro-optical elements comprised of a randomly varying component can be used to help smooth out the interference effects within the far-field intensity profile. The influence of the random micro-optical elements will be demonstrated in 1-D and 2-D applications using coherent illumination sources. The performance with and without the random elements will be analyzed. Both diffractive and refractive elements are discussed and demonstrated. Their combination with imaging integrators is shown to produce uniform intensity profiles in 1-D lines or 2-D rectangular profiles.  

       
Generation of several uniform spots with micro optics 

Paper 7062-28  
Author(s): Jana Fruendt, Manfred Jarczynski, Thomas Mitra, LIMO-Lissotschenko Mikrooptik GmbH (Germany)

 
Abstract

Direct laser patterning of various materials is industrially implemented into several micro-system production lines like inkjet printing, solar cell technology and flat-panel display production.
In contrast to applications of single mode sources, multimode lasers can provide extremely high power. High power allows multi channel material processing if uniform light fields can be provided in parallel.
We present an illumination system based on a high power multimode laser source which generates several uniform spots simultaneously without high stability requirements for the incoming laser source. These spots can be generated in diverse sizes and distances.
Applications could be direct material processing as well as mask illumination approaches.   

   
       
Free form micro-optics enable uniform off-axis illumination and superposition of high power laser devices 

Paper 7062-29  
Author(s): Tanja Bizjak, Oliver Homburg, Andreas Bayer, Thomas Mitra, Lutz Aschke, LIMO-Lissotschenko Mikrooptik GmbH (Germany)

 
Abstract

Free form micro-optics can be manufactured in glass, semiconductors or crystals generating the appropriate beam profile and providing the advantages in laser applications, such as ablation, welding, soldering, cutting, drilling, laser annealing, micro-machining and deep-UV lithography. Each lens of the array can be designed individually and can also be shaped asymmetrically. The applications results of such monolithic arrays are presented for beam shaping of high power diode lasers. The generation of a homogeneous light field by a 100 W laser with off-axis illumination under an angle of 30°-50° is shown. A multi-kW line generator based on the superposition of over 50 diode laser bars under different illumination angles is demonstrated as well. Novel microoptical beam shapers in lithographic applications reduce the complexity of macrooptics in hyper-NA illumination systems. 

Application of the angular spectrum diffraction transform in the design of binary optical element 

Paper 7062-44  
Author(s): Yanmei Wu, Junchang Li, Kunming Univ. of Science and Technology (China)

 
Abstract

The sampling conditions that using FFT to calculate the angular spectrum diffraction transform are deduced. Combining the Gerchberg-Saxton（GS）algorithm with the angular spectrum theory of diffraction, the design method of binary optical element to realize beam transformation is advanced. And a design example of diffraction element in marking pattern is also given  

Dispersion compensation of femtosecond laser pulses by maximising a second harmonic signal with a feedback loop containing a genetic search algorithm and an acoustic-optic modulator 

Paper 7062-51  
Author(s): Andrew Mori, Univ. Stellenbosch (South Africa) and CSIR National Laser Ctr. (South Africa); Lourens R. Botha, Anton du Plessis, Ted Roberts, Hendrik Maat, CSIR National Laser Ctr. (South Africa)

No abstract available