Spectral singularities and threshold gain of a slab laser under illumination of a focused Gaussian beam

Abstract

We study spectral singularities of an infinite planar slab of homogeneous optically active material in focus of a thin lens under illumination of a Gaussian beam. We describe the field distribution of the Gaussian beam under this configuration as a plane wave propagated near the optical axis which its phase and amplitude vary with distance from center of the beam. Based on this approximation, we carry out the transfer matrix for the slab. We explore the consequences of this configuration on determining the threshold gain of the active medium and tuning the resonance frequencies related to spectral singularities. We show that the spectral singularities and the threshold gain besides that vary with distance from center of the Gaussian beam, also they change with relative aperture of the focusing lens. As a result, using a thin lens with higher relative aperture, the spectral singularities corresponding resonances shift to the higher frequencies (lower wavelengths). Numerical results confirm the theoretical findings

11 pages, 6 figures

References in corpus (7)

• Spectral singularities in PT-symmetric periodic finite-gap systems
• Lasing Threshold Condition for Oblique TE and TM Modes, Spectral Singularities, and Coherent Perfect Absorption
• Wave emission and absorption at spectral singularities
• PT-symmetric spectral singularity and negative frequency resonance
• Spectral Singularities and CPA-Laser Action in a Weakly Nonlinear PT-Symmetric Bilayer Slab
• Cavity controlled spectral singularity
• Spectral singularities and tunable slab lasers with 2D material coating