Spectral Singularities and a New Method of Generating Tunable Lasers

We use a simple setup based on an infinite planar slab gain medium with no mirrors to explore the possibility of realizing a recently discovered resonance effect related to the mathematical concept of spectral singularity. In particular we determine the range of the gain coefficient g and the width L of the gain region required to achieve this resonance effect. We outline a method that allows for amplifying waves of desired wavelength by adjusting the gain coefficient (pumping intensity). We expect this method to have important practical applications in building tunable lasers