Modal domains and selectivity in large square lasers

Modes in square resonators have C4v symmetry. A special set of modes in these resonators have odd parities and behave like whispering gallery modes. These quasi-whispering gallery modes have high quality factors and exhibit interesting features. In particular, higher order quasi-whispering gallery modes present nodes that seem to be grouped into smaller domains. We show that the removal of one of these domains does not significantly affect a particular mode but can lead to significant increment in the radiation losses of other modes. This mode selectivity process can eventually be used to develop quasi single-mode lasers.