(a) One approach for metallic nanolasers with surface-emitting properties is to encapsulate a semiconductor heterostructure pillar in an insulator then a low optical loss metal such as silver or aluminium. Such an approach is particularly suitable for electrical pumping of the laser. In the figure shown an InP/InGaAs heterostructure is used with SiN insulator. Some light in the optical mode escapes through the bottom of the pillar and the substrate. (b) The optical mode in such structures is trapped on the InGaAs gain region in the center of the pillar due to refractive index differences. The figure shows just the center section of the pillar containing the InGaAs. The contour lines show of the trapped optical mode in a slice through the pillar center, with color giving intensity. The arrows show the magnitude and direction of the time averaged Poynting vector for this slice of the mode and show that the energy of the mode is mostly being dissipated as heat in the metal sidewalls.
