Spatial tomography of light resolved in time, spectrum, and polarisation

Area of Science:

• Optics and Photonics
• Quantum Information Science
• Laser Physics

Background:

• Characterizing optical beams requires measuring polarization, spectrum, temporal dynamics, and spatial complex amplitude for applications in laser dynamics, telecommunications, and nonlinear optics.
• Existing techniques have limitations: non-interferometric methods struggle with spatial phase, and phase-sensitive methods require a reference source.
• Analyzing multiple, mutually incoherent optical fields with complex wavefronts is particularly challenging.

Purpose of the Study:

• To develop a comprehensive method for measuring the complete description of unknown optical beams, including their spectral, temporal, and polarization characteristics.
• To overcome the limitations of current optical beam characterization techniques, especially for complex and incoherent fields.
• To provide a versatile tool for analyzing the spatiotemporal and spatiospectral properties of light.

Main Methods:

• Harnessing principles of spatial state tomography to perform measurements.
• Developing a technique to measure a complete beam description as a set of density matrices.
• Resolving spatial complex amplitude for multiple mutually incoherent fields within each density matrix slice.

Main Results:

• Successfully measured spectrally, temporally, and polarization-resolved spatial state density matrices for an unknown optical beam.
• Demonstrated the ability to resolve the spatial complex amplitude of multiple mutually incoherent fields.
• Revealed spectral or temporal evolution of fields, even when spectrally or temporally overlapping, through multiple density matrix slices.

Conclusions:

• The developed spatial state tomography method provides a complete description of optical beams, overcoming limitations of previous techniques.
• This approach is effective for characterizing complex wavefronts of multiple incoherent fields.
• The method was successfully demonstrated on the output of a vertical-cavity surface-emitting laser, showcasing its practical applicability.