Achromatic complex holograms for laser mode conversion

Area of Science:

• Optics and Photonics
• Holography
• Diffractive Optics

Background:

• Conventional complex phase masks exhibit chromatic aberrations, limiting their use in broadband optical systems.
• Achieving achromatic optical transformations is crucial for advanced photonic applications requiring wavelength independence.

Purpose of the Study:

• To present a novel achromatic holographic phase mask capable of performing optical beam transformations over an extended spectral range.
• To demonstrate the device's ability to overcome chromatic limitations inherent in traditional phase masks.

Main Methods:

• Fabrication of a holographic phase mask by encoding phase profiles into volume Bragg gratings.
• Integration of the volume Bragg grating between two surface gratings to manage spectral components.
• Experimental validation using narrow-line lasers (488-1550 nm) and a broadband femtosecond source.

Main Results:

• Demonstration of achromatic optical beam transformations over a spectral range exceeding 1000 nm.
• The device automatically aligns spectral components to the Bragg angle and equalizes phase incursion for all wavelengths.
• Successful transverse mode conversion validated against theoretical predictions.

Conclusions:

• The developed holographic phase mask offers a robust solution for achromatic optical beam shaping.
• This technology enables consistent optical performance across a broad spectrum, advancing applications in laser processing, imaging, and spectroscopy.