Multiple quantum well in-line optical modulators using tunable distributed Bragg gratings photonically controlled active array

Abstract

The integration of photonic technology into phased array radar systems promises to reduce aperture, weight, size, transmit/receive (T/R) module complexity, mitigate EMI, and accommodate wider signal bandwidth with frequency independent beam steering. One of the photonic control methodology is to employ true time delays which have been incorporated in a variety of ways in the realization of phased array radar. We have proposed a technique using wavelength division multiplexing (WDM) to address a large number of elements, with each clement carrying the phase information on one channel/wavelength. This architecture is optically non-coherent and achieves a reduction in hardware complexity via sharing of various devices. As part of the Office of Naval Research's Accelerated Capabilities initiative, Raytheon/University of Connecticut team is developing and implementing this methodology. This paper focuses on the devices, including novel waveguide amplitude modulators and tunable filters, required to implement such an architecture. In particular, we propose to employ the quantum confined Stark effect in 1.55 micron InGaAsP/InP multiple quantum well (MQWs) for these components. We intend to use the quadratic electrorefractive effect in InGaAsP (1.5 /spl mu/m)/InGaAsP (1.3 /spl mu/m) and/or InGaAsP (1.5 /spl mu/m)/InP multiple quantum well (MQW) structures to achieve intensity modulation with the applied signal voltage. The investigation focuses on MQW devices which exhibit the quantum confined Stark effect since these devices yield large changes of refractive index with low insertion loss and are capable of being modulated at the required frequencies. The details of modulator structures are described.