Nonlinear optical detection of terahertz-wave radiation from resonant-tunneling-diode oscillators

Summary form only given. The sensitive detection of terahertz (THz)-wave radiation from compact sources at room temperature is crucial for real-world THz-wave applications, such as non-destructive inspection and homeland security. As an extremely compact THz-wave source, the resonant-tunneling-diode (RTD) oscillator is a particular important electronic device operating in the THz-wave frequency region. The oscillation frequency of RTD is now close to 2 THz with improvements in their structures [1]. For detecting THz-wave radiation from RTDs at room temperature, frequency up-conversion in nonlinear optical crystals is a promising technique because the input frequency and power of RTD can be calibrated by measuring the output wavelength and energy of up-converted waves, respectively. In the up-conversion process, the THz-wave radiation (ω_thz) is mixed with an optical pump wave (ω_p) in a nonlinear crystal to generate an optical up-converted wave (ω_up) according to the energy conservation law (ω_p = ω_up + ω_thz) [2, 3]. The generated up-converted wave is detected using a commercial photodetector with nanosecond resolution. This optical approach differs from conventional room-temperature THz-wave direct detectors, such as the pyro-electric detector and Golly cell, which offer slow response time on the order of millisecond.In this study, we demonstrate the nonlinear optical detection of μW-level THz-wave radiation from three continuous-wave (CW) RTD devices with oscillation frequencies of 0.58, 0.78, and 1.14 THz at room temperature. We show that the THz-wave radiation from RTD devices is up-converted to near-infrared (NIR) waves in nonlinear optical MgO:LiNbO3 crystal under the noncollinear phase-matching condition.