Due to its fast axis distribution, it will generate similar polarization distributions regardless of the incident polarization direction of the light. Furthermore, the former is more circular than the latter.Īnother notable difference is that the m = 2 vortex retarder is a polarization independent device. The profile created by the m = 1 retarder has a smaller central hole (about Ø0.25 mm) than the profile from the m = 2 waveplate (about Ø0.4 mm). Both of these intensity profiles were created from the same 633 nm laser source. The table to the right highlights some of the main differences between the m = 1 and m = 2 vortex retarders, including graphs of the generated donut beams by each style retarder. For an explanation of why the linear power density provides the best metric for long pulse and CW sources, please see the Damage Thresholds tab.įigure 1: The plot above shows the fast axis orientation (denoted by arrows) over the surface of our m = 1 vortex retarders.
<0.08 nm/☌ over the Operating Temperature Range Liquid Crystal Polymer Between N-BK7 Glass Plates They are mounted in a thin walled, Ø1" housing that is compatible with many of our Ø1" optic mounts, including XY translation mounts. The engraved lines on the housing of these devices give a rough indication as to the position of the center.Īn AR coating is applied to both outer surfaces to improve the transmission through the optic at its specified wavelength. The point of rotation for the fast axis is nominally located in the center of the glass substrate, but has a Ø1 mm variable range from retarder to retarder. Vortex retarders should be used at a single wavelength close to the design wavelength the donut beam profile will degrade as the deviation from the design wavelength increases. In general, the m = 1 retarder will produce a smaller, more circular donut hole compared to the m = 2. Both the m = 1 and m = 2 retarders are capable of generating a donut hole shaped beam however, the polarization direction of the resulting beam will be different (see the Comparison tab for more information). Specifically, these retarders convert standard TEM 00 Gaussian beams into so-called "donut hole" Laguerre-Gaussian modes, as shown in Figure 2. Vortex retarders generate nondiffracting, or Bessel, beams, which have been demonstrated to enlarge the trapping region of optical tweezers.
Additionally, they are compatible with beam diameters from 21.5 mm (0.84") down to 0.3 mm (0.01"). Due to their construction, these retarders can accept a large AOI of ☒0°. Photo-alignment techniques set the LCP molecules' orientations to create the continuously rotating fast axis, with the point of rotation at the center of the optic. Each LCP vortex retarder is composed of a thin LCP film sandwiched between two Ø23 mm, 1 mm thick N-BK7 glass plates. The m = 1 retarders have an additional mark, denoted by 3 lines, to indicate the orientation of the zero-degree fast axis (see Figure 1). These retarders are mounted in an aluminum housing with an engraving along the perimeter to assist in locating the center point of the plate for beam alignment purposes.
As a result, they generate different polarization patterns from linearly polarized light (see the Comparison tab for more information). The difference between the two orders is the fast axis distribution over the clear aperture of the retarder. These retarders are offered as either m = 1 (Item # Prefix WPV10L) or m = 2 (Item # Prefix WPV10) order vortex retarders. Thorlabs’ Liquid Crystal Polymer (LCP) Vortex Retarders are half-wave retarders designed to affect the radial and azimuthal polarization of optical fields. A vortex retarder has a constant retardance across the clear aperture but its fast axis rotates continuously over the area of the optic. Compatible with Beam Sizes from Ø300 µm to Ø21.5 mm.Center Wavelength Options from 405 nm to 1550 nm.Options for m = 1 or m = 2 Vortex Retarder.Controls Radial and Azimuthal Polarizations.True Zero-Order Vortex Half-Wave Plates.Figure 1: Each retarder is engraved with its part number and leader lines to aid in alignment.