Fig. 1. Structure schematics. (a) VCSEL; (b) EEL

Fig. 2. Applications of VCSELs^[2]

Fig. 3. Schematic of oxide-confined VCSEL and profile of refractive index

Fig. 4. Schematics of single-mode VCSEL structures. (a) Surface-relief VCSEL; (b) implantation/oxidation hybrid aperture VCSEL; (c) multi-oxide aperture VCSEL; (d) metal-aperture VCSEL; (e) Zn-diffusion aperture VCSEL; (f) holey VCSEL; (g) subwavelength grating VCSEL; (h) coupled-cavity VCSEL

Fig. 5. Typical schematic of 850-nm high-speed VCSEL^[4]

Fig. 6. Broadband high-reflectivity HCG^[103]. (a) Schematic of HCG; (b) principle of HCG with broadband and high reflectivity of HCG

Fig. 7. Metasturcture VCSELs with different functions. (a) Schematic of HCG-VCSEL^[53]; (b) HCG-VCSEL array with beam shaping^[118]; (c) schematic of tunable HCG-VCSEL^[119]; (d) schematic of monolithically integrated multi-wavelength HCG-VCSEL array^[6]

Fig. 8. HCG-VCSELs for photonic integrated circuits. (a) Schematic of Si-based HCG-VCSEL at 1550 nm (SOI-based HCG as reflector)^[124]; (b) schematic of Si-based HCG-VCSEL (SOI-based HCG as reflector and coupler)^[125]; (c) schematic of VCSEL with horizontal output waveguide (SiN-based HCG as coupler)^[126]