A preferred transmission filter (10) includes a first flange (18) transparent to a laser beam (58) and includes a second flange (20) opaque to the laser beam (58) and meltable upon exposure thereto. The flanges (18, 20) are in registered, abutting relationship with a laser weld bead (62) at the juncture (44) between the flanges (18, 20) to provide a fluid seal circumscribing the filter (10). The preferred filter manufacturing apparatus (12) includes a laser (54) coupled to a robot arm (50) controlled by a programmable logic controller (52). The controller (52) operates the robot arm (50) in order to direct the laser beam (58) through the first flange (18) onto the second flange (20) and along the juncture (44) to form the laser weld bead (62).