We present a fully tunable multistage narrowband optical pole-zero notch filter that is fabricated in a silicon complementary metal oxide semiconductor (CMOS) foundry. The filter allows for the reconfigurable and independent tuning of the center frequency, null depth, and bandwidth for one or more notches simultaneously. It is constructed using a Mach-Zehnder interferometer (MZI) with cascaded tunable all-pass filter (APF) ring resonators in its arms. Measured filter nulling response exhibits ultranarrow notch 3 dB BW of 0.6350 GHz, and nulling depth of 33 dB. This filter is compact and integrated in an area of 1.75 mm 2. Using this device, a novel method to cancel undesired bands of 3 dB bandwidth of 910 MHz in microwave-photonic systems is demonstrated. The ultranarrow filter response properties have been realized based on our developed low-propagation loss silicon channel waveguide and tunable ring-resonator designs. Experimentally, they yielded a loss of 0.25 dB/cm and 0.18 dB/round trip, respectively.

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Multilevel thin film processing, global planarization and advanced photolithography enables the ability to integrate complimentary materials and process sequences required for high index contrast photonic components all within a single CMOS process flow. Developing high performance photonic components that can be integrated with electronic circuits at a high level of functionality in silicon CMOS is one of the basic objectives of the EPIC program sponsored by the Microsystems Technology Office (MTO) of DARPA. Our research team consisting of members from: BAE Systems, Alcatel-Lucent, Massachusetts Institute of Technology, Cornell University and Applied Wave Research reports on the latest developments of the technology to fabricate an application specific, electronic-photonic integrated circuit (AS_EPIC). Now in its second phase of the EPIC program, the team has designed, developed and integrated fourth order optical tunable filters, both silicon ring resonator and germanium electro-absorption modulators and germanium pin diode photodetectors using silicon waveguides within a full 150nm CMOS process flow for a broadband RF channelizer application. This presentation will review the latest advances of the passive and active photonic devices developed and the processes used for monolithic integration with CMOS processing. Examples include multilevel waveguides for optical interconnect and germanium epitaxy for active photonic devices such as p-i-n photodiodes and modulators.

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An RF-photonic filter and down-converter system based on a compact and fully tunable silicon optical filter has been demonstrated and analyzed. Its frequency down-conversion was implemented using optical heterodyne detection with an injection locked laser. This system filters a 1.25 GHz-wide signal with 20 dB filter rejection and a very broad 20 GHz center tuning range. The frequency down-conversion process is operated in a low-IF mode to avoid laser low frequency noises. Measured system Spurious-Free Dynamic Range (SFDR) of 94.3 dB*Hz 2 3 has been limited by the optical losses from I/O coupling and measurement setup. We examined experimentally that 105.3 dB*Hz 2 3 SFDR is achievable if the encountered optical loss were reduced to the filter's intrinsic loss. Based on the excellent agreements between measured and simulated results, we explore the critical improvements of the silicon photonic devices needed for the system to achieve 118 dB*Hz 2 3 SFDR and briefly review the status of the component technologies. Index Terms-Coherent detection, microwave-photonic filter, RF-photonic filter, silicon photonics, ultra wide band filter. I. INTRODUCTION M ILITARY industries continue to have strong interest in ultra-wide-bandwidth RF-photonic systems, primarily due to their ability to deliver performance with unprecedented high time-bandwidth product [1]. As communication/electronic warfare systems evolve to handle applications involving commercial cellular, fixed wireless, and high frequency radars all in a single platform, the system instantaneous bandwidth might reach 100 GHz. Designing with a conventional approach for such high spectral range would yield a complex system with enormous size, weight and power consumption. Though the speed of modern semiconductor devices already supports RF IC with bandwidths exceeding many tens of gigahertz, there is still not a filter technology competitive enough to facilitate radio operations with a similar bandwidth. Recent tunable filters (mostly MEMS or LTCC cavity-based) have center frequencies that are confined to a range of less than 10 GHz [2]-[4] and,