Abstract
We present an experimental characterization of frequency- and bias-dependent detector responses in a resonant-tunneling-diode (RTD) terahertz (THz)-wave oscillator. By tuning the incident THz-wave frequency and the bias voltage applied to the RTD device, the origins of detection signals are identified to be two distinct detection modes. One is based on square-law detection near the peak and valley points of the negative differential conductance (NDC) region, with the detection bandwidth determined by an integrated slot antenna. The other is based on detectable current changes induced by injection locking within the NDC region when the frequency of the incident THz-wave radiation to be detected is coincident with that of the bias-dependent RTD self-oscillation between 0.74 and 0.81 THz, resulting in a minimum noise equivalent power (NEP) of 7.7 pW/√Hz at 0.78 THz at room temperature. Our conclusions demonstrate that an RTD oscillator can be used as a sensitive THz-wave detector within and around the NDC region.
Highlights
On the other hand, it has long been known that the nonlinearity appearing in the current–voltage (I–V) characteristics of Resonant tunneling diodes (RTDs) can be leveraged to utilize them as detectors.4–6,12,13 Such significant nonlinearity leads to square-law detection, especially near the peak and valley points of the negative differential conductance (NDC) region
The other is based on detectable current changes induced by injection locking within the NDC region when the frequency of the incident THz-wave radiation to be detected is coincident with that of the bias-dependent RTD self-oscillation between 0.74 and 0.81 THz, resulting in a minimum noise equivalent power (NEP) of 7.7 pW/ͱHz at 0.78 THz at room temperature
Coherent THz-wave detection based on injection locking within the NDC region was recently demonstrated using a 0.34-THz RTD oscillator in the context of THz-wave wireless communications,14 suggesting the possibility of superior detection performance compared with other diode-based room-temperature THz-wave detectors, such as Schottky barrier diodes15 and Fermi-level managed barrier diodes
Summary
It has long been known that the nonlinearity appearing in the current–voltage (I–V) characteristics of RTDs can be leveraged to utilize them as detectors.4–6,12,13 Such significant nonlinearity leads to square-law detection, especially near the peak and valley points of the negative differential conductance (NDC) region. The other is based on detectable current changes induced by injection locking within the NDC region when the frequency of the incident THz-wave radiation to be detected is coincident with that of the bias-dependent RTD self-oscillation between 0.74 and 0.81 THz, resulting in a minimum noise equivalent power (NEP) of 7.7 pW/ͱHz at 0.78 THz at room temperature.
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