Mathematical simulation of composite optical systems loaded with active medium

Abstract

A set of programs to simulate a diffractive optics in various laser systems is developed. The codes are based on the efficient and general diffractive propogation computer program that employs FFT (FHT) techniques and the scheme of splitting the diffractive and gain-refractive steps of calculation. The codes include new method of iterative calculations for the optical resonators loaded with active medium. This method solves the problem of calculation 's convergency in a case of several equal-loss modes and allows to find the single mode stability limits. The method is proposed to calculate continuous multimode lasing when neglecting a transverse-mode beating.The results of numerical simulation of several laser systems are reported: 1) the slave laser under the injection of an external signal (injection locked laser, 2-D code) ; 2) three-mirror resonators with active medium (3-D code) ; 3) two optically coupled lasers having unstable resonators (3-D code) ; 4) 1-D laser array in the Talbot cavity (self-imaging resonator 2-D code).Most suitable parameters of pointed optical schemes to achieve high efficiency and high beam quality can be found by using mathematical simulation. INTRODUCTIONRecently there has been considerable interest in composite laser systems El, 21. This is due to several reasons: 1. Powerful single-frequency high quality laser beam may be obtained using the masteroscillator ( MO ) radiation injection into the slave laser having unstable cavity.2. Three mirror unstable cavity with a central coupling hole in the concave mirror ( see Fig.1) allows to vary independently conditions in the central and outer zones. So, additional possibilities are available to control laser beam characteristics.3. Optically coupled laser arrays are very attractive to produce high power density on a target when multiple laser beams are mutually coherent. In this case the total power equals N times single laser power and the diffraction limited angle is determined by the whole output aperture.It is important in calculations to include correctly the interference of light beams reflected from different parts of an optical system. The mirror edges and coupling hole diffraction is very essential, too. Till now there are known not so many works devoted to mathematical simulation of composite laser systems including a diffraction and an interference as well. The problem of mathematical simulation of active systems (loaded with an active medium) is much more complex because of nonlinearity.One of the most important physical problems, that may be solved by numerical simulation, is the determination of parameters of the designed system for which single mode lasing is stable. Several transverse modes have nearly equal losses in composite systems more frequently than in a monolithic laser with unstable resonator. It 108 / SPIE Vol. 1501 Advanced Laser Concepts andApplications(1991) O-8194-0610-4/91/$4.00 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/17/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUs...