This paper presents the design of a high-density optically differential reconfigurable gate array (ODRGA) using a 0.18 mum - 5 Metal CMOS process technology. ODRGA is a type of Field Programmable Gate Arrays (FPGAs). However, unlike conventional FPGAs, ODRGAs are reconfigured optically using an external optical system. Although ODRGAs have already been fabricated using a 0.35 mum - 3 Metal CMOS process technology, their gate-density remains unsatisfactory. For that reason, a new ODRGA-VLSI chip with four logic blocks, five switching matrices, and 16 I/O bits was fabricated on a 7.82 mm(2) chip using more advanced process technology. This paper presents the detailed design of a fabricated ODRGA-VLSI chip, the optical reconfiguration circuit, the gate array structure, the CAD layout, and an ODRGA-VLSI chip mounted on an estimation board. This study also includes experimental results regarding the reconfiguration period.