Optical antennas that operate at infrared wavelengths are studied for their potential application in enhancing the sensitivity of infrared detectors. Huge enhancement of infrared intensity can be achieved at the gap region of dipole and bowtie aperture antennas. The intensity enhancement is found to increase monotonically with a narrower gap size. The infrared radiation is also found to be concentrated above and below the antenna plane at the gap region, which allows for easy integration of the optical antennas with infrared detectors. The advantages of the infrared antennas, such as strong field enhancement and easy fabrication, may present a viable solution toward achieving highly sensitive and highly compact uncooled infrared detectors to impact numerous infrared technologies.