The American Institute for Manufacturing Integrated Photonics (AIM Photonics) is focused on developing an end-to-end
integrated photonics ecosystem in the U.S., including domestic foundry access, integrated design tools, automated
packaging, assembly and test, and workforce development. This paper describes how the institute has been structured to
achieve these goals, with an emphasis on advancing the integrated photonics ecosystem. Additionally, it briefly
highlights several of the technological development targets that have been identified to provide enabling advances in the
manufacture and application of integrated photonics.
We present the theory of operation along with detailed device designs and initial experimental results of a new class of
uncooled thermal detectors. The detectors, termed microphotonic thermal detectors, are based on the thermo-optic effect
in high quality factor (Q) micrometer-scale optical resonators. Microphotonic thermal detectors do not suffer from
Johnson noise, do not require metallic connections to the sensing element, do not suffer from charge trapping effects,
and have responsivities orders of magnitude larger than microbolometer-based thermal detectors. For these reasons,
microphotonic thermal detectors have the potential to reach thermal phonon noise limited performance.
The limits to silicon modulator bandwidth and power consumption are explored. Traditional electrical interconnects
provide insufficient bandwidth (~10Gb/s) and consume far too much power (~10pJ/bit) for future high performance
computing applications. Microphotonic devices closely integrated with advanced CMOS electronics have the potential to
dramatically lower intra- and inter-chip communication power consumption while greatly increasing available
bandwidth. Our recent results confirm the significant advantages offered by microphotonic communication links. We
have broken the 100fJ/bit barrier by demonstrating 4-micron diameter microdisk modulators achieving 10Gb/s data
transmission with a bit-error-rate below 10-12 and a measured power consumption of only 85fJ/bit. Through rigorous
simulation and experimentation, we consider ultimate limits to silicon modulator bandwidth and power consumption.
Microphotonic devices employing strong confinement of light are of growing importance for key applications such as
telecommunication and optical interconnects. They have unique and desirable characteristics but their extreme
sensitivity to dimensional variations makes them difficult to successfully implement. Here, we discuss strategies towards
the successful realization of strong confinement devices. We leverage what planar fabrication technology does best:
replicating structures. Although the absolute dimensional control required for successful fabrication of many strong
confinement devices is all but impossible to achieve, we show that surprisingly-high relative dimensional accuracy can
be obtained on structures in proximity of one another on a wafer. This provides an advantage to schemes that are based
on multiple copies of low-complexity structures. These copies can be made nearly identical or with precise relative-dimensional
offsets to achieve the desired function. We quantify the achievable relative dimensional control and discuss
the first demonstration of multistage filters, integrated polarization diversity, and high-order microring-filter banks.
A novel fabrication strategy has produced optical microring-resonator-based thermal detectors. The detectors are based
on the thermo-optic effect and are thermally isolated from a silicon wafer substrate so as to maximize the temperature
excursion for a given amount of incident radiation and minimize the impact of thermal phonon noise. The combination
of high-Q, thermal isolation, and lack of Johnson noise offers thermal microphotonic detectors the potential to achieve
significantly greater room temperature sensitivity than standard bolometric techniques. Several batch fabrication
strategies were investigated for producing thermal microphotonic detectors using waveguide materials such as LPCVD
Silicon Nitride (Si3N4) on Oxide and Silicon on Insulator (SOI). Fabrication challenges and loss reduction strategies will
be presented along with some initial infrared detection results.
Progress in developing high speed ADC's occurs rather slowly - at a resolution increase of 1.8 bits per decade. This slow progress is mostly caused by the inherent jitter in electronic sampling - currently on the order of 250 femtoseconds in the most advanced CMOS circuitry. Advances in femtosecond lasers and laser stabilization have led to the development of sources of ultrafast optical pulse trains that show jitter on the level of a few femtoseconds over the time spans of typical sampling windows and can be made even smaller. The MIT-GHOST (GigaHertz High Resolution Optical Sampling Technology) Project funded under DARPA's Electronic Photonic Integrated Circuit (EPIC) Program is trying to harness the low noise properties of femtosecond laser sources to overcome the electronic bottleneck inherently present in pure electronic sampling systems. Within this program researchers from MIT Lincoln Laboratory and MIT Campus develop integrated optical components and optically enhanced electronic sampling circuits that enable the fabrication of an electronic-photonic A/D converter chip that surpasses currently available technology in speed and resolution and opens up a technology development roadmap for ADC's. This talk will give an overview on the planned activities within this program and the current status on some key devices such as wavelength-tunable filter banks, high-speed modulators, Ge photodetectors, miniature femtosecond-pulse lasers and advanced sampling techniques that are compatible with standard CMOS processing.
Advanced analog-optical sensor, signal processing and communication systems could benefit significantly from wideband (DC to > 50 GHz) optical modulators having both low half-wave voltage (Vpi) and low optical insertion loss. An important figure-of-merit for modulators used in analog applications is Tmax/Vpi, where Tmax is the optical transmission of the modulator when biased for maximum transmission. Candidate electro-optic materials for realizing these modulators include lithium niobate (LiNbO3), polymers, and semiconductors, each of which has its own set of advantages and disadvantages. In this paper, we report the development of 1.5-um-wavelength Mach-Zehnder modulators utilizing the electrorefractive effect in InGaAsP/InP symmetric, uncoupled semiconductor quantum-wells. Modulators with 1-cm-long, lumped-element electrodes are found to have a push-pull Vpi of 0.9V (Vpi*L = 9 V-mm) and 18-dB fiber-to-fiber insertion loss (Tmax/Vpi = 0.018). Fabry-Perot cutback measurements reveal a waveguide propagation loss of 7 dB/cm and a waveguide-to-fiber coupling loss of 5 dB/facet. The relatively high propagation loss results from a combination of below-bandedge absorption and scattering due to waveguide-sidewall roughness. Analyses show that most of the coupling loss can be eliminated though the use of monolithically integrated inverted-taper optical-mode converters, thereby allowing these modulators to exceed the performance of commercial LiNbO3 modulators (Tmax/Vpi ~ 0.1). We also report the analog modulation characteristics of these modulators.