Phototransistors based on InP HEMTs and HBTs, and their applications to fiber-optic/millimeter-wave data transmission systems

다국어 초록 (Multilingual Abstract)

Phototransistors based on InP HEMTs and InP HBTs are investigated and practically implemented to fiber-opticmillimeter-wave data transmission systems. The physical origins involved in photodetection characteristics of the fabricated InP HEMT are clarified through the consideration of its phototransistor operations. Based on the understanding of these photodetection mechanisms, the important device parameters including phototransistor internal gain and optical gain cutoff frequency are determined for the InP HEMT. It is experimentally shown for the first time that they are applicable to millimeter-wave subharmonic optoelectronic mixers that have the possibility to use low frequency local oscillator (LO) for millimeter-wave frequency up-conversion. To evaluate InP HEMT optoelectronic mixer performances, an internal conversion gain is introduced and characterized at 60GHz band. Nonlinear distortion characteristics and usable LO ranges for InP HEMT subharmonic optoelectronic mixers are also investigated. Utilizing them, fiber-opticmillimeter-wave data transmission system is constructed and 622Mbps data transmission over 30km fiber-optic link and 3m wireless link at 60GHz band is demonstrated. Their other applications, direct optically injection-locked oscillators are introduced with expecting their potentials to offer high-power and low phase-noise LO source. By endowing them with harmonic optoelectronic mixing functions, a novel antenna base station architecture is proposed for fiber-opticmillimeter-wave downlinks. It is made up of an InP HEMT oscillator, in which the InP HEMT device simultaneously provides the functions of optically injection-locked oscillation and harmonic optoelectronic mixing. Fiber-optic30GHz data transmission systems employing the proposed scheme are presented and 16QAM downlink data transmission in these systems is successfully demonstrated with the help of its low phase-noise characteristics. For achieving gigabit transmission in fiber-opticmillimeter-wave links, InP HBTs which are expected to provide wide photonic bandwidth are also exploited. It is experimentally shown that an InP HBT exhibits higher optical responsivity and wider optical 3dB bandwidth in comparison with InP HEMT. Utilizing it as a broadband optoelectronic mixer, 1.25Gbps data transmission in both fiber-optic wireline and 60GHz wireless links is achieved and their applicability to broadband fiber-opticmillimeter-wave convergence networks are given.