Fig. 1. Schematic diagrams of double-junction cascade QD VCSEL. (a) Overall structure; (b) active region structure

Fig. 2. Energy-band structure, standing-wave profile, and refractive-index distribution of double-junction cascaded QD VCSEL. (a) Energy-band structure; (b) standing-wave intensity and refractive index versus epitaxial depth

Fig. 3. Power and voltage of QD VCSEL versus current at 25 ℃ and 85 ℃. (a) Power; (b) voltage

Fig. 4. Carrier differential gain curves of single-junction and double-junction QD VCSELs at 25 ℃. (a) Single-junction; (b) double-junction

Fig. 5. Longitudinal distribution of net electron concentration at the aperture center for single-junction and double-junction QD VCSELs. (a) Single-junction; (b) double-junction

Fig. 6. Longitudinal distribution of net hole concentration at the aperture center for single-junction and double-junction QD VCSELs. (a) Single-junction; (b) double-junction

Fig. 7. Small-signal modulation response of single-junction and double-junction QD VCSEL devices at 25 ℃. (a) Single-junction; (b) double-junction

Fig. 8. Small-signal modulation response of single-junction and double-junction QD VCSEL devices at 85 ℃. (a) Single-junction; (b) double-junction

Fig. 9. Relationship between f_{3 dB} and J-Jth for single-junction and double-junction QD VCSELs at 25 ℃ and 85 ℃

Fig. 10. Power versus injection current for double-junction QD VCSEL with 17.5 and 16.5 pairs of p-DBR

Fig. 11. Small-signal modulation response of the double-junction QD VCSEL with 16.5 pairs of p-DBR at different temperatures. (a) 25 ℃; (b) 85 ℃

Fig. 12. Small-signal modulation response of double-junction QD VCSEL with different apertures. (a) 4 μm; (b) 5 μm; (c) 6 μm