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Coherent terahertz imaging with synchronized distributed-feedback diode lasers

We present a heterodyne hybrid terahertz imaging system, which combines electronic narrow-band emitters, operating at 0.2 THz and 0.62 THz respectiveley, with a continuous-wave two-color laser system for electro-optic detection. The laser system employs two distributed-feedback laser diodes, providing a tunable difference frequency which is phase-locked to the emitted terahertz frequency with an offset of 10 MHz.