Method and apparatus for generating a phase-modulated wave front of electromagnetic radiation

A method for generating a phase-modulated wave front of electromagnetic radiation comprising the steps of:

• providing an input wave front of electromagnetic radiation, E(x,y),
• performing a spatial amplitude modulation α(x,y) on the input wave front to generate a spatial amplitude distribution a(x,y) in the electromagnetic radiation in a plane transverse to a direction of propagation of the electromagnetic radiation,
• Fourier or Fresnel transforming the amplitude-modulated wave front a(x,y) to form a Fourier or Fresnel distribution of the amplitude-modulated wave front ã(fx,fy) said Fourier or Fresnel distribution comprising Fourier or Fresnel components,
• filtering the Fourier or Fresnel distribution by phase shifting at least part of a zero-order component of the Fourier or Fresnel distribution ã(fx,fy) in relation to other components of the Fourier or Fresnel distribution and/or damping a zero-order component of the Fourier or Fresnel distribution ã(fx,fy) in relation to other components of the Fourier or Fresnel distribution by a spatial filter having a filter function H(fx,fy) giving the phase shift and/or damping of the zero-order component in relation to higher-order components of the Fourier or Fresnel distribution ã(fx,fy), and
• inverse Fourier or inverse Fresnel transforming the filtered electromagnetic radiation whereby a phase-modulated wave front o(x′,y′) is formed, said phase-modulated wave front being a function of at least the input wave front E(x,y), the amplitude modulation α(x,y), and the filter function H(fx,fy).

A system for generating a phase-modulated wave front of electromagnetic radiation, said system comprising

• a first deflecting and/or absorbing device for receiving an input wave front E(x,y) of electromagnetic radiation, performing a spatial amplitude modulation α(x,y) on the input wave front by deflecting and/or absorbing parts of the wave front to generate a spatial amplitude distribution a(x,y) in a plane transverse to a direction of propagation of the wave front, and emitting the amplitude modulated wave front a(x,y),
• means for Fourier or Fresnel transforming the amplitude-modulated wave front a(x,y) to form a Fourier or Fresnel distribution ā(fx,fy), said Fourier or Fresnel distribution comprising Fourier or Fresnel components,
• a spatial filter for receiving the Fourier or Fresnel distribution ã(fx,fy), phase shifting one or more first components in relation to one or more second components of the Fourier or Fresnel distribution and/or damping one or more third components in relation to one or more fourth components of the Fourier or Fresnel distribution, and emitting a filtered distribution ā′(fx,fy), said spatial filter being characterized by a filter function H(fx,fy) which gives the damping and/or phase shift for each component of the Fourier or Fresnel distribution ā(fx,fy),
• means for inverse Fourier or inverse Fresnel transforming the filtered electromagnetic radiation to form a phase-modulated wave front o(x′,y′), said phase-modulated wave front being a function of at least the input wave front E(x,y), the amplitude modulation α(x,y), and the filter function H(fx,fy).

A system for generating a phase-modulated wave front of electromagnetic radiation, said system comprising

• a first deflecting and/or absorbing device for receiving an input wave front E(x,y) of electromagnetic radiation, performing a spatial amplitude modulation α(x,y) on the input wave front by deflecting and/or absorbing parts of the wave front to generate a spatial amplitude distribution a(x,y) in a plane transverse to a direction of propagation of the wave front, and emitting the amplitude modulated wave front a(x,y),
• means for Fourier or Fresnel transforming the amplitude-modulated wave front a(x,y) to form a Fourier or Fresnel distribution ã(fx,fy) said Fourier or Fresnel distribution comprising Fourier or Fresnel components,
• a spatial filter for receiving the Fourier or Fresnel distribution ã(fx,fy), phase shifting a zero-order component of the Fourier or Fresnel distribution in relation to other components of the Fourier or Fresnel distribution and/or damping a zero-order component of the Fourier or Fresnel distribution in relation to other components of the Fourier or Fresnel distribution, and emitting a filtered distribution ā′(fx,fy), said spatial filter being characterized by a filter function H(fx,fy) which gives the damping and/or phase shift of the zero-order component in relation to other components of the Fourier or Fresnel distribution ā(fx,fy), and
• means for inverse Fourier or inverse Fresnel transforming the filtered electromagnetic radiation to form a phase-modulated wave front o(x′,y′), said phase-modulated wave front being a function of at least the input wave front E(x,y), the amplitude modulation α(x,y), and the filter function H(fx,fy).