Generation of Radially Polarized Beams with an Image-Rotating Resonator

We show how a passive image-rotating optical resonator can be used to convert a linearly polarized, lowest-order Gaussian beam into a radially polarized beam. The image and polarization rotation of the cavity removes the frequency degeneracy of the modes, making it possible to select the radially polarized mode by cavity tuning. With the addition of gain, the same cavity should operate as a radially polarized laser when injection seeded at the proper wavelength.