Characterization of blue- and red- very small aperture lasers for hybrid recording

The characterization of a rectangular aperture on a very small aperture laser (VSAL) is described and the parameters of interest to hybrid recording technology is quantified. VSALs based on blue laser diodes (LDs) (λ = 405 nm) and red-LDs (λ = 658 nm) with 100 nm × 200 nm rectangular apertures milled into 50 nm thick aluminum by focused ion beam etching (FIBE) are fabricated and their slope efficiencies (SE) captured by a NA 0.65 objective lens in the far field (FF) measured. SE is defined as the-ratio of the measured optical power to the input current. The background SEs (BSE) were measured after coating with Al but prior to forming the aperture for reference. The SEs of these blue and red lasers with apertures were 2.7 mW/A (BSE = 1.3 mW/A) and 3.8 mW/A (BSE = 0.3 mW/A), respectively. Detailed characterization of both lasers before and after aperture fabrication indicate that this greater SE of the red VSAL is primarily due to greater efficiency of coupling between the laser and the aperture, η_coupling, and greater transmission efficiency of the aperture, η_aperture, in the red. It is not due to difference in the SBs of the two LDs themselves. Near field simulation of the apertures using the finite difference time domain (FDTD) method supports the above conclusions.