High index contrast photonics platform

Abstract

A new low-loss high-index-contrast photonics platform has been developed for integrated optics and microwave photonics. The platform consists of a material system that has an index contrast that is adjustable from 0 to 25% and which is processed using conventional CMOS tools. The platform allows one to four orders of magnitude reduction in the size of optical components compared with conventional planar technologies. As an example, meter long path lengths occupy coils that are millimeters in diameter. Microwave photonic building blocks that are enabled include large bit count programmable delay lines for beam steering and shaping that fit in less than a square centimeter and which have delays controllable from 5 fsec to 10 nsec. Also enabled are arrays of high order tunable filters, a hundred micrometers in size, having linewidths ranging from tens of MHz to tens of GHz. These filters can be tuned over several hundred GHz, and when placed in Vernier architectures can be tuned across the C band (5 THz). An optical chip typically consists of dozens of optical elements. Each element is placed in its own micro-control loop that consists of a thin film heater for thermo-optic control and a thermistor for electronic feedback. The micro-control loops impart intelligence to the optical chip.

Integrated waveguide Bragg gratings for microwave photonics signal processing

“…When multiple devices are employed to implement a more complex signal processor, separate temperature actuators (heaters) localized in correspondence of each device could be used to implement a more accurate control of the temperature across the chip. A similar approach has been successfully employed in previous works [5,57]. Note that the simple layout of the DPS-WBG can be modified to create larger phase shifts while keeping the same all-pass configuration.…”

“…Lowering the speed requirement down to 1.6 Gb/s, the tuning range reaches 660 ps with a loss below 2.2 dB. This corresponds to a loss per time-delay unit of approximately 3.3 dB/ns, which is very low compared to state-of-the-art all-pass filters (APF, constituted by cascaded ORRs coupled to a common waveguide bus) [86,87], coupled resonators optical waveguides (CROW, where resonators are side-coupled to each other) [57,87,88] or photonic-crystal (PhC) waveguides [78]. The expected device length is relatively high (approximately 2 cm) which is difficult to realize with e-beam techniques, thus eventually requiring the use of deep-ultraviolet optical lithography or nano-imprinting lithography.…”

“…In fact, in addition to the well-known advantages of photonics, integrated solutions also offer compactness, light weight, and low power consumption. Moreover, these solutions promise to reduce the per-unit cost thanks to the high yield and reproducibility when realized with CMOS compatible fabrication equipment [57].…”

Integrated Ultra-Low-Loss 4-Bit Tunable Delay for Broadband Phased Array Antenna Applications

“…As a result, integration of such devices would benefit the system by decreasing the footprint, increasing the delay accuracy, increasing stability and reducing cost. Although many fully integrated optical TTD have been demonstrated [4]- [7], the maximum amount of delay is usually limited by high propagation loss limiting the delay time to the picosecond range or a few nanoseconds. We have recently demonstrated record low propagation losses in a Si 3 N 4 /SiO 2 planar waveguide technology, which allows for long delays to be implemented on chip scale devices [8], [9].…”