Fig. 1. (a) Schematic of the InP/InGaAs nanolaser with DBRs directly grown on (001)-oriented SOI wafers. The nanocavity and the two DBRs are marked. (b) Schematic depicting the improved optical feedback from the two defined DBRs. (c) Cross-sectional schematic of the InP/InGaAs nanolaser on SOI. Five In0.53Ga0.47As ridge quantum wells are embedded as the active gain medium. (d) Tilted-view SEM photo of the as-grown InP/InGaAs nanoridges on (001) SOI wafers. (e) Cross-sectional TEM image of the as-grown InP/InGaAs nanoridge on SOI wafers.

Fig. 2. Design of nanoscale DBRs with different parameters. (a) Calculated reflectivity from InP/air interface, 10 periods of DBRs with 325 nm InP and 225 nm air gaps, and 10 periods of DBRs with 225 nm InP and 225 nm air gaps. (b) Mode profiles of the first three supported transverse modes. (c) Calculated electric field distribution of the TE01 mode with the introduction of 10 periods of DBRs with 225 nm InP and 225 nm air gaps. (d) Calculated mirror loss of the TE01 mode of a 20 μm long nanocavity with different mirror architectures.

Fig. 3. (a) Top view SEM image of the fabricated InP/InGaAs nanolasers with defined DBRs (325 nm InP spacers and 225 nm air gaps) on SOI. (b) Tilted-view SEM image of InP/InGaAs nanolasers with labeled DBRs. (c) Zoomed-in SEM photo of one DBR composed of InP spacers and air gaps. (d) Zoomed-in SEM photo of one DBR showing the etched InP spacers and air gaps. (e) Close-up showing the details of the DBRs. The InP spacer exhibits a tapered morphology from the bottom to the top.

Fig. 4. (a) Room temperature PL spectra of one InP/InGaAs nanolaser with conventional 20 μm long FP cavity under different excitation levels. Equally spaced FP modes are detected. (b) Room temperature PL spectra of one InP/InGaAs nanolaser with DBRs (325 nm thick InP spacers and 225 nm thick air gaps) and a 20 μm active waveguide section under different excitation levels. Stimulated emission at 1442 nm is detected. (c) Room temperature PL spectra of one InP/InGaAs nanolaser with DBRs (225 nm thick InP spacers and 225 nm thick air gaps) and a 20 μm active waveguide section under different excitation levels. Stimulated emission at 1478 nm is detected.

Fig. 5. (a) Zoomed-in emission spectra of three different InP/InGaAs nanolasers under low excitation levels. The free spectral ranges are marked. (b) Light in–light out (L-L) curves of the three measured InP/InGaAs nanolasers with/without DBRs.