Polarized Propagation-Invariant Light Field Generation
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Solution Overview
Problem
Existing non-uniform vector polarized light fields either have limited polarization types, unstable polarization states during propagation, or fail to maintain polarization consistency, which hinders their application in optical communication and other fields.
Innovation Solution
A system and method for generating a polarized propagation-invariant light field using a spatial light modulator to produce two Laguerre-Gaussian mode beams with specific Gouy order relationships, which are then combined using a Ronchi grating to maintain orthogonal uniformly polarized states unchanged during propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If non-uniform vector polarized light fields are generated using conventional methods (radially polarized, azimuthally polarized, higher-order Poincare sphere), then the polarization states vary at different positions in space providing higher research value, but the polarization type remains limited (only linear, or single type of elliptical/circular) and cannot contain more beam information
Solution Approach 1:
The light field is segmented into multiple Laguerre-Gaussian mode beams with different topological charges and radial indices. By superimposing these segmented beams with specific Gouy phase order relationships, the system achieves complex polarization states that vary in both position and type, thereby increasing beam information capacity while maintaining spatial non-uniformity
Solution Approach 2:
The patent creates a composite light field by superimposing multiple Laguerre-Gaussian mode beams with different polarization states and spatial distributions. This composite structure enables the light field to exhibit complex polarization characteristics including linear, elliptical, and circular polarization types simultaneously, enhancing both versatility and information capacity
2Loss of information
If complex polarization types containing all linear, elliptical, and circular polarization are generated by combining multiple mode beams, then more beam information is contained, but the polarization states always change at different distances due to different change patterns of mode beams during propagation
Solution Approach 1:
The patent carefully selects and controls the parameters of Laguerre-Gaussian mode beams, specifically the Gouy phase order relationship between different beams. By adjusting radial indices and topological charges to satisfy specific mathematical relationships, the system achieves parameter matching that ensures polarization states remain stable during propagation while maintaining complex polarization types
Solution Approach 2:
The system pre-establishes the Gouy phase order relationship between multiple Laguerre-Gaussian mode beams before propagation begins. This preliminary configuration ensures that during subsequent propagation, the polarization states maintain their intended relationships and stability, preventing the polarization drift that occurs with conventional approaches
3Device complexity
If uniformly polarized light fields are used, then the structure is simple and easy to generate, but the forms of polarization states are unvaried making it impossible to contain and transmit more beam information
Solution Approach 1:
The patent introduces a spatial light modulator as an intermediary device that enables the generation of complex non-uniform vector polarized light fields from a simple uniform laser source. This intermediary component provides the necessary phase and amplitude modulation to create multiple Laguerre-Gaussian mode beams with controlled Gouy phase relationships, achieving high polarization versatility without requiring complex optical systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The generated polarized propagation-invariant light field maintains a stable polarization state across propagation, supporting linear, elliptical, and circular polarizations, thus enabling efficient optical information transfer.
Implementation Method 1
generate two holograms, superimpose grating functions of the two holograms to obtain a composite hologram, and load the composite hologram into the spatial light modulator, where the spatial light modulator is configured to modulate the laser light and simultaneously generate a first Laguerre-Gaussian mode beam and a second Laguerre-Gaussian mode beam
Implementation Method 2
a first quarter-wave plate and a second quarter-wave plate, configured to modulate polarization states of the first Laguerre-Gaussian mode beam and the second Laguerre-Gaussian mode beam after filtering from linear polarization to right-handed circular polarization and left-handed circular polarization orthogonal to each other
Implementation Method 3
a beam combining element, configured to: combine the focused first Laguerre-Gaussian mode beam and second Laguerre-Gaussian mode beam into one beam, and generate a plurality of diffracted beams, to obtain a polarized propagation-invariant light field
Data Source
AI summary
The invention provides a method and a system for generating a polarized propagation-invariant light field. The system includes a laser source, a spatial light modulator, a computer, a first lens, a shading element, a first quarter-wave plate, a second quarter-wave plate, a second lens, and a beam combining element. In the present invention, two Laguerre-Gaussian mode beams that satisfy a particular Gouy order relationship are generated, and orthogonal even polarization is applied to the two Laguerre-Gaussian mode beams. The two Laguerre-Gaussian mode beams are then focused onto a Ronchi grating to be stably combined into polarized propagation-invariant light field. The light field generated in the present invention simultaneously has linear polarization, elliptical polarization, and circular polarization in a cross section of the light field, and in a propagation process of the light field in free space, apart from normal spot size scaling, polarization distribution remains unchanged.