Sampling a vortex from a Gaussian beam using a wedge-plate shearing interferometer

Abstract

Many vortex-generation techniques have been developed to address a range of potential applications, exploiting their unique amplitude and phase profiles and their possession of orbital angular momentum. In this work, we present what may be the simplest method of vortex beam generation, requiring only a wedged optic: the wedge-plate shearing interferometer (WPSI). We show that the WPSI can reflect a first order Laguerre–Gaussian vortex beam ( L G 01 ) with a theoretical purity of > 99 % from an input fundamental Gaussian beam, with 98% L G 01 purity experimentally demonstrated. We demonstrate 1% power conversion with a route to 14%. The monolithic WPSI is a simple, compact, and highly stable device, which can operate at any wavelength that the material is transparent to. We anticipate that it will be useful where sampling a robust, high-purity vortex beam from a Gaussian laser beam is required, including low-cost vortex generation for metrology or education.

Visible skyrmion praseodymium laser in red and orange

“…10 Additionally, the UV-fused silica WPSI is compatible with ultraviolet to far infrared wavelengths, and could be extended further if constructed with other materials. 12 In this work we have demonstrated a new approach to generating optical skyrmions through directly extracting and combining modes from a laser. The device is low-cost and compact, requiring no specialist equipment or optics.…”

“…In this implementation a wedge-plate shearing interferometer (WPSI) was used, which was an uncoated UV-fused silica plate with a small (40 arcsec) wedge angle (Thorlabs SI100P). Details of the operation of the device can be found in prior publications 12 and has been shown to reliably and efficiently extract high quality modes from a laser resonator. 9,10 The skyrmion states were then produced through the combination of the two coherent u 0 0 and u −1 0 modes to meet the conditions for a paraxial skyrmion beam in Eq.…”

“…This technique has been demonstrated in a variety of laser designs. [9][10][11] We adopt the wedge-plate shearing interferometer (WPSI) configuration, 12 which has advantages in cost, wavelength flexibility, robustness, and simplicity. Using this method, we generated high quality Néel-, Bloch-, and anti-type skyrmions in red (640 nm) and orange (607 nm) using a praseodymium-doped gain medium.…”

Red and orange vortex Pr3+ fibre laser using a mode converting output coupler

“…When these adjustments are correctly configured the interfering beams will form a non-separable, propagation invariant LG 01 mode, full details of this technique can be found in previous work. 17 The conversion from incident Gaussian to LG 01 is only partial, therefore the microscope slide acts as a vortex mode output coupler.…”