We summarize some design tips and design procedures of nanoapertures with strong field enhancement, based on the theoretical calculations and analyses of near-field distributions of unconventional C apertures and bow-tie apertures by a finite-difference time-domain method. A novel L-shaped aperture is proposed and further validates the proposed design rule. As a result, a 15×15-nm full width half maximum spot forms in the light exit plane of the L aperture. Its intensity maximum enhancement reaches a factor of about 568 and the power throughput is bigger than unity. The mechanisms of electromagnetic field enhancement are preliminarily analyzed. This unconventional nanoaperture is likely to be directly used as an exit aperture of very small aperture lasers, or as an unattached shield, to produce a subwavelength light source with high transmission. © 2005 Society of Photo-Optical Instrumentation Engineers.