A High-intensity Nano-aperture Vertical-Cavity Surface-Emitting Laser With Controlled Polarization

near-field optical data storage. Also, data transfer rates canbegreatly increased iftheVCSELsareapplied inparallel arrays[11. Previous workonnanoaperture VCSELsutilize conventional circular apertures whichsuffer fromlowpoweroutput through thenanoaperture whentheaperture size becomes muchsmaller thanonewavelength[23]. We propose toapply aunique C-shaped nano-aperture (C-aperture) ontoVCSELs.Fromsimulation, theC-aperture showsthree orders of magnitude higher powertransmission efficiency thanaconventional square orcircular aperture producing thesame near-field spotsize[41. We report herearecord-high near-field intensity of15.4mW/[tm2 achieved fromournanoaperture VCSELwitha70nmC-aperture. Ourtop-emitting VCSELsaredesigned tooperate around 970nmandconsist of9.5pairs ofp-type distributed Bragg reflectors (DBR),three strain-compensated InGaAs/GaAsP quantumwellsand38.5pairs ofn-DBRs.The reflectivity ofthetopmirror isenhanced witha150nmthick Aucoating. We insert ahalf-wavelength thick SiO2 filmbetween theAucoating andthetopDBR pairs toenhance thetransmission through thenano-aperture. We use wetoxidation ofAlGaAstoobtain a2.8pim-diameter oxide aperture forcurrent andmodeconfinement. Thenanoapertures areetched through theAucoating using aFocused IonBeam(FIB). Thetransmission oflight through theC-aperture ispolarization-dependent. Forthematched polarization, theCaperture produces awell-confined near-field spotwithhighintensity. However, fortheorthogonal mismatched polarization, theresulted near-field spotispoorly confined andtheintensity istwoorders ofmagnitude lower. Since VCSELsnormally havetwodegenerate orthogonal polarization states, weneedtocontrol thepolarization ofthe VCSELsinorder toapply theC-aperture ontheVCSELs.We openfour50*1500nm slits surrounding a70nmCaperture intheAu coating using FIBtocontrol thepolarization. Sincethetransmission oflight polarized perpendicular totheslit ismuchhigher thanthatoflight polarized parallel totheslit, thepolarization ofthe VCSELsiseffectively controlled tobeparallel totheslit duetolower loss inthis direction. Toidentify howmuchnetpowercomesoutoftheC-aperture, weblock thelight transmitted through theslits by depositing 150nmthick Pttofill theslits using electron-beam assisted chemical vapordeposition onaFIB/SEM dual-beam system. Pthasreflectivity of73%at1ptm, compared withreflectivity of95%forAu.Sothepolarization selectivity bytheslits ismaintained after theslits arefilled withPt.We measured thepolarization-resolved power