BNNTs-dye lasers operating at a stable exceptional point – EXCEPTIONAL

EXCEPTIONAL aims at achieving a long-standing goal in non-Hermitian photonics: the realization of a laser operating at a stable exceptional point (EP). For this we seek i) to rely on a well-established laser technology, namely Vertical External Cavity Surface Emitting Lasers (VECSELs) and ii) to develop a new kind of laser device: a macroscopic laser cavity whose gain medium consists in dye molecules embedded in Boron Nitride Nanotubes (BNNTs) as a dielectric template. In addition to the immunity to bleaching due to the nanotube shielding, this laser cavity fulfils the two requirements for a stable EP laser: i) the dispersive nonlinearities of dye molecules are weak at the gain maximum, therefore the system can be built in the so-called parity-time configuration, which warrants the existence of EPs; ii) the (nanosecond) time scale of dye fluorescent molecules is shorter than the photon lifetime, giving rise to what is known as a class-A laser, ensuring the stability of EPs