We present measurements and analytical modeling which demonstrate enhanced THz transmission through a subwavelength aperture via light-induced diffraction. Our experiment involves photoexciting a conducting pattern onto a silicon interface so as to control and modulate the near-field interference of THz radiation. To illustrate the concept, we photoexcite a simple double-conducting stripe pattern on the incident side of a silicon wafer which has a slit etched into a gold film on the exit side. We show that under certain resonant conditions set by the stripe dimensions, a constructive near-field interference can bring about enhanced transmission through the slit. By raster scanning the excitation pattern under these resonant conditions, one can build an image of subwavelength features such as the slit aperture of our sample.