Closed-cavity solutions with partially coherent fields in the space-frequency domain

Numerical investigation on the generation of high-order Laguerre-Gaussian beams in end-pumped solid-state lasers by introducing loss control

This paper reports a robust and systematic approach to generate high-order scalar Laguerre-Gaussian (LG_p,l) beams in end-pumped solid-state lasers by introducing loss control. Based on the spatial distributions of Laguerre-Gaussian modes and the theory of transverse mode selection, the "loss control" is implemented by an amplitude mask in the resonator. This proposed mechanism can be divided into three categories: radial loss, azimuthal loss, and the combination of radial and azimuthal loss, which correspond to excite radial high-order modes (LG_p,0), azimuthal high-order modes (LG_0,l), and regular high-order modes (LG_p,l), respectively. By controlling the locations and thicknesses of opaque rings and lines on the mask, all kinds of LG_p,l modes can be obtained. With the application of mode purity, all the generated modes possess high mode purities greater than 93% in simulation.

Analysis of an optical resonator formed by a pair of specially shaped axicons

We propose a design for an optical resonator suited to using large-bore active media. The resonator consists of a pair of waxicons, so we call it a "wwaxicon optical resonator." The resonator is considered a conventional (solid) resonator surrounded by coaxial annular resonators. A numerical simulation of the resonator designed for use in a commercial CO2 laser is performed. It is found that parasitic oscillation modes can be suppressed by the use of an spatial-frequency filter. The resonator exhibits oscillation in the TEM*01 transverse mode and produces twice as much output power as a sevenfold multipass stable optical resonator.

Generation of high-order Hermite-Gaussian modes in end-pumped solid-state lasers for square vortex array laser beam generation

This study reports the first systematic approach to the excitation of all high-order Hermite-Gaussian modes (HGMs) in end-pumped solid-state lasers. This study uses a metal-wire-inserted laser resonator accompanied with the "off axis pumping" approach. This study presents numerical analysis of the excitation of HGMs in end-pumped solid-state lasers and experimentally generated HGM patterns. This study also experimentally demonstrates the generation of an square vortex array laser beams by passing specific high-order HGMs (HGn,n + 1 or HGn + 1,n modes) through a Dove prism-embedded unbalanced Mach-Zehnder interferometer [Optics Express 16, 19934-19949]. The resulting square vortex array laser beams with embedded vortexes aligned in a square array can be applied to multi-spot dark optical traps in the future.

Coupled simulation of chemical lasers based on intracavity partially coherent light model and 3D CFD model

Coupled simulation based on intracavity partially coherent light model and 3D CFD model is firstly achieved in this paper. The dynamic equation of partially coherent intracavity field is derived based on partially coherent light theory. A numerical scheme for the coupled simulation as well as a method for computing the intracavity partially coherent field is given. The presented model explains the formation of the sugar scooping phenomenon, and enables studies on the dependence of the spatial mode spectrum on physical parameters of laser cavity and gain medium. Computational results show that as the flow rate of iodine increases, higher order mode components dominate in the partially coherent field. Results obtained by the proposed model are in good agreement with experimental results.

Numerical study for selective excitation of Mathieu-Gauss modes in end-pumped solid-state laser systems

This study reports a possible first systematic approach to the selective excitations of all Mathieu-Gauss modes (MGMs) in end-pumped solid-state lasers with a new kind of axicon-based stable laser resonator. The study classifies MGMs into two categories, and explores and verifies the approach to excite each MGM category using numerical simulations. Controlling both the "cavity mode gain" and the "cavity conical asymmetry" of the axicon-based stable laser resonator achieves the proposed selective MGM-excitation approach.

Generation of doughnutlike vortex beam with tunable orbital angular momentum from lasers with controlled Hermite-Gaussian modes

This study demonstrates successive higher-order Hermite-Gaussian (HG(0,m)) mode operations in a microchip solid-state laser with a controlled off-axis laser diode (LD) pumping and generation of the corresponding doughnutlike laser beam of tunable ring diameter and orbital angular momentum, by experimentally focusing a Hermite-Gaussian mode (HGM) lasing beam into an astigmatic mode converter (AMC) with a mode-matching lens. Based on the successful generation of stable doughnutlike vortex beams by combining the LD off-axis pumping of microchip lasers and an AMC, this study proposes a design for a compact, solid doughnutlike vortex laser beam generator that combines three elements (i.e., laser cavity, mode-matching lens, and AMC) into one practical device. The desired doughnutlike vortex beam with different orbital angular momentum is easily generated by simply controlling the lateral off-axis pump position and pump beam shape on the laser crystal by numerical simulation.

Generation of vortex beams from lasers with controlled Hermite- and Ince-Gaussian modes

We report selective excitations of higher-order Hermite-Gaussian and Ince-Gaussian (IG) modes in a laser-diode-pumped microchip solidstate laser and controlled generation of corresponding higher-order and multiple optical vortex beams of different shapes using an astigmatic mode converter (AMC). Simply changing the pump-beam diameter, shape, and lateral off-axis position of the tight pump beam focus on the laser crystal within a microchip semispherical cavity can produce the desired optical vortex beams in a well controlled manner. Pattern changes featuring different IG and HG modes obtained by rotating the AMC are also demonstrated. Numerical simulation shows that the vortex structure is changed by controlled off-axis laser diode pumping, which could lead toward precise optical manipulation of small particles.

Numerical study for selective excitation of Ince-Gaussian modes in end-pumped solid-state lasers

This study report a first systematic approach to the selective excitations of all Ince-Gaussian modes (IGMs) in end-pumped solid-state lasers. The proposed Ince-Gaussian mode excitation mechanism is based on the "mode-gain control" concept. This study classifies IGMs into three categories, explores and verifies approach to excite each IGM category using numerical simulation.

Two-dimensional simulation of an unstable resonator with a stable core

An optical resonator simulation code based on the idea of a partially coherent optical field has been developed and used to optimize the design parameters of an unstable resonator with a stable core. The resonator was intended for use with low-gain, large-bore lasers, such as the chemical oxygen-iodine laser (COIL). First the design parameters of the resonator were optimized by the simulation code; then a set of mirrors was fabricated for a small-scale COIL. A 14-W output with M(2) = 29 was obtained. The experimentally obtained results were in good agreement with calculations.