Konrad Altmann

The particle picture presented by the author in the paper “A particle picture of the optical resonator” [K. Altmann, ASSL 2014 Conference Paper ATu2A.29], which shows that the probability density of a photon propagating with a Gaussian wave can be computed by the use of a Schrödinger equation, is generalized to the case of a wave with arbitrary shape of the phase front. Based on a consideration of the changing propagation direction of the relativistic mass density propagating with the electromagnetic wave, a transverse force acting on the photon is derived. The expression obtained for this force makes it possible to show that the photon moves within a transverse potential that in combination with a Schrödinger equation allows to describe the transverse quantum mechanical motion of the photon by the use of matter wave theory, even though the photon has no rest mass. The obtained results are verified for the plane, the spherical, and the Gaussian wave. Additional verification could be provided also by the fact that the mathematical equation describing the Guoy phase shift could be derived from this particle picture in full agreement with wave optics. One more verification could be obtained by the fact that within the range of the validity of paraxial wave optics, Snell's law could also be derived from this particle picture. Numerical validation of the obtained results for the case of the general wave is under development.

The comment on the paper "Contradiction within wave optics and its solution within a particle picture," [Opt. Express 23, 3731 (2015)10.1364/OE.23.003731] is discussed.

It is shown that the condition provided by paraxial wave optics for the resonance frequencies of the eigenmodes of an optical resonator leads to a contradiction, if the resonator is divided into subcavities. Moreover, it is shown that the results obtained in this way imply a violation of energy conservation. Since for nearly plane waves, paraxial wave optics becomes exact within wave optics, this contradiction also concerns wave optics. A solution for this problem is proposed within a particle picture as presented recently by the author. It is based on a consideration of the change of momentum of a photon bouncing between two equiphase surfaces with vanishing distance. This leads to a transverse force exerted on the photon. Assigning a relativistic mass to the photon leads to a Schrödinger equation describing a transverse motion of the photon. In this way the transverse modes of an optical resonator can be understood as the quantum mechanical eigenfunctions of a single photon.

We derive a new model and simulation technique called “Dynamic Multimode Analysis (DMA)” to simulate the 3-dimensional dynamic behavior of a laser. A Gaussian mode analysis is used to obtain resonator eigenmodes taking into account thermal aberrations. These modes are coupled by a set of rate equations to describe the dynamic behavior of the individual modes for cw and Q-switched lasers. Our approach analyzes mode competition and provides a detailed description of the laser beam in terms of output power, beam quality factor M², and pulse shape. Comparison of experimental data with our simulation results provides new insight into the effect of mode competition and the operation of Q-switched lasers.

A new method for computing eigenmodes of a laser resonator by the use of finite element analysis (FEA) is presented. For this purpose, the scalar wave equation [Δ + k²]E(x,y,z) = 0 is transformed into a solvable 3D eigenvalue problem by separating out the propagation factor exp(-ikz) from the phasor amplitude E(x,y,z) of the time-harmonic electrical field. For standing wave resonators, the beam inside the cavity is represented by a two-wave ansatz. For cavities with parabolic optical elements the new approach has successfully been verified by the use of the Gaussian mode algorithm. For a DPSSL with a thermally lensing crystal inside the cavity the expected deviation between Gaussian approximation and numerical solution could be demonstrated clearly.

In an earlier paper [Appl. Opt. 43, 1892 (2004)], the title was incorrectly expressed. That error is corrected here.

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