S-waveplate converts linear polarization to radial or azimuthal polarization and circular polarization to an optical vortex.
Main features
- Converts linear polarization to radial or azimuthal polarization.
- Converts circular polarization to an optical vortex.
- High 94% transmission @ 1030 nm (no AR coating).
- Stand-alone – no additional optical elements needed.
- High damage threshold: 63,4 J/cm² @1064 nm, 10 ns and 2,2 J/cm² @1030 nm, 212 fs.
- Suitable for high LIDT applications and high-power lasers.
- Reliable and resistant surface – the structure is inside the bulk.
Detailed description
Fabrication of S-waveplate is based on the inscription of self-organized nanograting’s inside fused silica glass using a femtosecond laser.
Beams with radial or azimuthal polarization attract significant interest due to unique optical properties associated with their inherent symmetry. Such beams enable resolution below the diffraction limit and interact without the undesirable anisotropy produced by linearly polarized light.
S-waveplate can be beneficial in polarization-sensitive applications. For example, a radially polarized beam is more efficient at drilling and cutting high-aspect-ratio features in metals. Vector beams are also applicable in optical tweezers, laser micromachining, STED microscopy, and two-photon-excitation fluorescence microscopy.
Acknowledgment. Enabling technology was developed by Prof. Peter G. Kazansky’s group in the Optoelectronics Research Centre at the University of Southampton. Southampton University has applied for patent application and appointed exclusivity in commercializing activities for Workshop of Photonics (Altechna R&D Ltd.).
Technical features
- High damage threshold | LIDT – 63.4 J/cm² @ 1064 nm, 10 ns; 2.2 J/cm² @ 1030 nm, 212 fs
- High transmission (no AR coating) – 94% @ 1030 nm, 92% @ 515 nm, 85% @ 343 nm of most SS lasers
- Large aperture possible – up to 15 mm
- Topological charges from 1 to 100
- Wavelength from 257 to 4000 nm
Main benefits
- Allows focusing into smaller spot size (using NA > 0.9)
- Ensures the same machining properties in all directions
- Ensures the same cutting speed in all directions
- Enable ring-shaped intensity distribution in focus (at NA <0.8)
- Increases cutting speed
- Suitable for high LIDT applications
- Suitable for high power lasers
Application examples
- STED microscopy
- Micromachining
- Micro drilling high-aspect-ratio channels
- Generate any cylindrical vector vortex
- Multiple particle trapping
- Micro-mill is driven by optical tweezers
- Use as an intracavity polarization-controlling element in cladding-pumped ytterbium-doped fiber laser for radially polarized output beam generation
Application example
Radial polarization used with high NA > 0.9 (numerical aperture) allows focusing into a smaller spot size comparing with limits described by diffraction.
Methods of use
Universal approach
Cylindrically symmetric polarization (radial or azimuthal) generation
- Mount a λ/2 waveplate into a kinematic holder.
- Place the radial polarization converter into the path of the linearly polarized beam.
- Align the center of the converter with the optical axis of the incident laser beam.
- Check the alignment with the linear polarizer placed after the converter. The dumbbell shape must be symmetric for all polarizer angles.
- Polarization state (radial/azimuthal) of the output beam can be controlled by rotating the converter or the incident polarization (by rotating λ/2 waveplate).
Simplified approach
Cylindrically symmetric polarization (radial or azimuthal) generation
- Place the radial polarization converter directly into the linearly polarized laser beam.
- Align the center of the converter with the optical axis of the incident laser beam.
- Check the alignment with the linear polarizer placed after the converter. The dumbbell shape must be symmetric for all polarizer angles.
- The polarization state of the output beam can be controlled by rotating the converter or the incident polarization (by rotating λ/2 waveplate placed before converter).