We experimentally demonstrate that a high-power 0.1-THz continuous wave can be generated by external modulation. A low-noise electrical amplifier and a W-band antenna with a gain of 25 dBi are employed to enhance photodiode output power. Detection power exceeds 1 mW when an absolute terahertz power meter is used. We experimentally demonstrate that a high-power 0.1-THz continuous wave can be generated by external modulation. A low-noise electrical amplifier and a W-band antenna with a gain of 25 dBi are employed to enhance photodiode output power. Detection power exceeds 1 mW when an absolute terahertz power meter is used.