Design of a surface-emitting, subwavelength metal-clad disk laser in the visible spectrum

We analyze metal-clad disk cavities designed for nanolasers in the visible red spectrum with subwavelength device size and mode volume. Metal cladding suppresses radiation loss and supports low order modes with room temperature Q of 200 to 300. Non-degenerate single-mode operation with enhanced spontaneous emission coupling factor β is expected with the TE_(011) mode that has a 0.46(λ_0/n)^3 mode volume and Q = 210 in a device of size 0.12λ_0^3. Threshold gain calculations show that room temperature lasing is possible using multiple GaInP/AlGaInP quantum wells as the gain medium. Placing a planar metal reflector under the cavity can enhance radiation and extraction efficiencies or increase the Q, without incurring additional metallic absorption loss. We show that the far-field radiation characteristics are strongly affected by the devices' immediate surroundings, such as changes in metal cladding thickness, even as the resonant mode profile, frequency, and Q remain the same. When the metal cladding is 1 µm thick, light radiates upward with a distinct intensity maximum at 45° when the cladding is 100 nm thick, the emitted light spreads in a near-horizontal direction.