Hybrid Laser Cavity Design for Improved Photon Lifetime and Performance

We report an optical cavity design that combines a distributed feedback (DFB) cavity as the primary feedback element for lasing with a silver mirror acting as a Fabry-Pérot cavity for broadband reflection and mode confinement. To evaluate the design, we studied the effects of the silver mirror by excluding the DFB cavity and compared its amplified spontaneous emission (ASE) properties with the sample without the mirror. In the structure with the mirror, the gain medium undergoes ASE at an excitation fluence of
$17.5\,\,\mathrm { {\mu J c}}\mathrm {m}^{\mathrm {-2}}$
compared to
$37\,\,\mathrm { {\mu J c}}\mathrm {m}^{\mathrm {-2}}$
for the sample without the mirror. This lower ASE threshold is attributed to enhanced mode confinement and photon density of states (PDOS) from the silver mirror increasing the cavity photon lifetime (
$ {\tau }_{\mathrm {c}}\mathrm {)}$
. Using this hybrid cavity, a multimode optically pumped laser with a threshold of
$42\,\,\mathrm { {\mu J c}}\mathrm {m}^{\mathrm {-2}}$
is demonstrated. This hybrid cavity design offers an effective solution that can be readily applied to other thin film-based laser devices.