Direct Optical Injection Locking of a 100-GHz-Class Oscillator IC Using a Back-Illuminated InP/InGaAs HPT and Its Applications

Tsugumichi SHIBATA
Minoru IDA

IEICE TRANSACTIONS on Electronics   Vol.E86-C    No.7    pp.1290-1298
Publication Date: 2003/07/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section INVITED PAPER (Special Issue on Recent Progress in Microwave and Millimeter-wave Photonics Technologies)
Category: MWP Devices
HPT,  HBT,  optically injection-locked oscillator,  microwave photonics,  millimeter wave,  optical fiber communication,  

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This paper discusses direct optical injection locking of a millimeter-wave oscillator using an InP/InGaAs heterojunction phototransistor (HPT) and its applications. Previously reported optically injection-locked oscillators (OILOs) are reviewed first. In particular, the features of a direct OILO (DOILO), where synchronization can be achieved by illuminating the active oscillator device itself, are discussed in comparison with the indirect OILO. DOILOs with excellent characteristics require high-performance transistors having both a high maximum oscillation frequency and fast photoresponse. We have developed high-performance opto-microwave-compatible InP/InGaAs HPTs whose layer and fabrication process are fully compatible with ultrahigh-speed heterojunction bipolar transistors. The paper discusses the photocoupling structure, and it is shown that the back-illuminated structure with the aid of InP subcollector enables one to achieve a 100-GHz-class DOILO. The configuration and performance of the 100-GHz-class DOILO are then presented; in particular, injection locking from optical signals with a modulation or beat frequency of around the fundamental (96 GHz) or second harmonic (192 GHz) is successfully demonstrated. To our knowledge, 96 GHz is the highest optically injection-locked frequency and 192 GHz is the highest inputmodulation frequency reported for OILOs. The HPT oscillator IC promises compact, low-power-consumption remote local oscillators for 100-GHz-class wireless systems and 100-Gbit/s-class optoelectronic clock recovery circuits. In addition, when the HPT oscillator is used as a modulator, we can attain cost-effective millimeter-wave systems compatible with conventional optical fiber networks transmitting digitally modulated baseband signals.