Diffraction-free Lommel beams

We consider a new family of nonparaxial diffraction-free laser beams with their complex amplitude being proportional to the $n$-th order Lommel function of two variables. Therefore, these beams are called Lommel beams (L-beams). We obtained explicit analytical expressions for the angular spectrum of plane waves and for the orbital angular momentum of the L-beams. Transverse intensity of the L-beams has a reflective symmetry with respect to both Cartesian coordinate axes. Since transverse intensity distribution of L-beams does not change upon propagation, L-beams are modes of free space (L-modes). Functions of complex amplitudes of even ($n = 2p$) and odd ($n = 2p + 1$) L-modes are mutually orthogonal. For certain parameter, L-modes become traditional Bessel modes.