Ram Oron

The formation of laser beams with pure azimuthal or radial polarization

Laser resonator configurations for obtaining pure azimuthal and radial polarized beams are presented. They involve the coherent summation, inside the laser resonator, of two orthogonally polarized TEM01 modes. Basic principles and experimental results with a Nd:YAG laser are presented. The results include a full space variant polarization measurement and show efficient formation of high-quality azimuthal and radial polarized beams.

Discontinuous phase elements for transverse mode selection in laser resonators

Discontinuous phase elements can be inserted into laser resonators so that the lasers will operate with only one desired high order transverse mode. These elements introduce sharp discontinuous phase changes so as to result in minimal losses for a desired transverse mode but high losses to others. The basic principles, along with experimental results with Nd:yttrium–aluminum–garnet and CO2 lasers, illustrating improved output powers with a high beam quality of low divergence, are presented.

Continuous-phase elements can improve laser beam quality

Siegman [Opt. Lett. 18, 675 (1993)] showed that binary-phase plates cannot improve laser beam quality. We demonstrate that continuous spiral phase elements can improve the quality of beams that originate from a laser operating with a pure high-order transverse mode. A theoretical analysis is presented, along with experimental results obtained with a CO(2) laser. The results reveal that a nearly optimal Gaussian output beam can be obtained with only a small decrease in the output power.

Chapter 6 – Transverse mode shaping and selection in laser resonators

This chapter discusses the transverse mode shaping and selection in laser resonators. Laser resonators are categorized as either stable or unstable. In a stable resonator, a ray launched inside the resonator parallel to the optical axis remains inside it, whereas in an unstable resonator, the ray may bounce off the resonator after a few round-trips. The chapter describes transverse modes in stable and unstable resonators, and also the numerical and analytical methods to determine the field distributions of the transverse modes. Various methods to select specific transverse modes in laser resonators, along with techniques for fabricating the needed intra-cavity elements are also described. Intra-cavity elements can be incorporated into laser resonators to shape specific transverse mode patterns and to discriminate and select a specific single mode out of the many modes that exist in the resonator. The properties of the laser output beams include beam quality, output power and field distributions. The analytical tools for describing the properties of the laser output beams, along with selected applications are discussed in the chapter.

Efficient formation of pure helical laser beams

Abstract A novel method for forming pure helical laser beams of pre-determined helicity is presented. It is mainly based on replacing one of the laser mirrors with a spiral phase element. The basic principles along with experimental results using a CO 2 laser are described.

Laser mode discrimination with intra-cavity spiral phase elements

A novel method for discriminating and selecting a specific high order mode is presented. It is based on introducing spiral phase elements into a laser resonator, so as to improve the output beam quality over that when the laser operates with multi-modes, and yet maintain a relatively high output power. The theoretical analysis, along with experimental results with CO and Nd:YAG lasers are presented. The results reveal that a 50% increase of laser output power over that operating with 2

Laser operation with two orthogonally polarized transverse modes

Laser resonator configurations, which enable laser operation with two orthogonally polarized transverse modes, are presented. The intensity distributions of these two modes can be chosen to be complementary, so the gain medium can be exploited more efficiently than with a single mode, leading to improved output power. Moreover, the two modes can be combined and efficiently transformed into a single high-quality beam. Basic principles and experimental results with Nd:YAG lasers are presented.

Anomaly in a high-numerical-aperture diffractive focusing lens

We show an anomalous behavior in a diffractive lens in which the spot size at the focus reaches a minimum at a numerical aperture of ~0.5 and then increases significantly at higher values. Theoretical and experimental results are presented, along with a comparison with refractive aplanatic lenses, in which the anomaly does not appear to exist.

Manipulating the Wigner distribution of high order laser modes

Abstract Despite the fact that the phase distribution across a beam emerging from a laser operating with several transverse modes is random, it is possible to improve the beam quality. This is achieved by manipulating the Wigner distribution function of the emerging beam, utilizing phase elements and a beam converter. The theoretical analysis along with experimental results with a Nd:YAG laser operating with two Laguerre–Gaussian modes are presented.

Planar optical dynamic crossbar switch

A compact dynamic crossbar switch, based on a planar optics configuration, is presented. It consists of a pair of identical planar holographic cylindrical telescopes, each recorded on a single substrate, and a two-dimensional array (8x8) ferroelectric liquid crystal spatial light modulator. The crossbar switch can direct the light from any particular source in a one-dimensional array of 8 sources to a particular detector in a one-dimensional array of 8 detectors. The design of the overall configuration is presented along with experimental results.