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8 May 2006 An optically triggered I-RTD hybrid device for continous-wave generation of THz oscillations
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A novel optically-triggered (OT) interband resonant-tunneling-diode (I-RTD) device (based on AlGaSb/InAs/AlGaSb heterostructures) concept for generating terahertz (THz) frequency oscillations has been previously presented that shows promise for achieving enhanced output power levels under pulsed operation. The main concept is to utilize novel nanoscale mechanisms to achieve an externally driven relaxation oscillation that consists of two phases. Namely, the first phase is a valence band (VB) well hole-charging transient produced by a natural Zener (interband) tunneling process and the second is a discharging transient induced by optical annihilation of the VB well hole-charge by externally-injected photon flux. While the initial simulation results for a practical diode-laser implementation clearly show the superiority of this new oscillator concept (i.e., excellent output power capability, ~10mW, over broad portions of the THz regime, ~300-600GHz), the specific optical-triggering conditions required by the AlGaSb/InAs based material systems (i.e., photonic-energy ~4.7 μm, intensity level ~3.5x107 W/cm2 and a pulse repetition frequency (PRF) equal to the THz oscillation period) are technically too demanding to meet for continuous-wave (CW) mode operation. Hence, this paper will report on variations and extensions of the original OT-I-RTD oscillator concept. Specifically, modifications to the device structure will be considered to allow for OT operation at 1.55 μm where the optical technology is more robust. Here the specific focus will be in the introduction of In1-xGaxAs /GaSbyAs1-y hetero-systems and the application of band-engineering to assess the potential of a 1.55 μm based OT-I-RTD oscillator design.
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Dwight Woolard, Weidong Zhang, Elliott Brown, Boris Gelmont, and Robert Trew "An optically triggered I-RTD hybrid device for continous-wave generation of THz oscillations", Proc. SPIE 6212, Terahertz for Military and Security Applications IV, 621207 (8 May 2006);

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