Photonic-electronic integration with polysilicon photonics in bulk CMOS

Here, I review the development of a polysilicon photonic platform that is optimized for integration with electronics fabricated on bulk silicon wafers. This platform enables large-scale monolithic integration of silicon photonics with microelectronics. A single-polysilicon deposition and lithography mask were used to simultaneously define the transistor gate, the low-loss waveguides, the depletion modulators, and the photodetectors. Several approaches to reduce optical scattering and mitigate defect state absorption are presented. Waveguide propagation loss as low as 3 dB/cm could be realized in front-end polysilicon with an end-of-line loss as low as 10 dB/cm at 1280nm. The defect state density could be enhanced to enable all-silicon, infrared photodetectors. The resulting microring resonant detectors exhibit over 20% quantum efficiency with 9.7 GHz bandwidth over a wide range of wavelengths. A complete photonic link has been demonstrated at 5 Gbps that transfers digital information from one bulk CMOS photonics chip to another.United States. Defense Advanced Research Projects Agency. Photonically Optimized Embedded Microprocessors Program (Award HR0011-11-C-0100

Irreversible Thermodynamic Bound for the Efficiency of Light-Emitting Diodes

A thermodynamic model for light-emitting diodes (LEDs) is developed by considering energy and entropy flows in the system. Thermodynamic constraints have previously been considered separately for the reversible process of electroluminescence in LEDs and for light extraction and collimation in other optical systems. By considering both processes in the LED model, an irreversible upper bound for the conversion of electrical energy to optical energy is derived and shown to be higher than unity, but tighter and more realistic than the reversible case. We also model a LED as an endoreversible heat engine where the carrier-transport processes can be directly connected to the elements of a thermodynamic cycle

Thermophotonics for ultra-high efficiency visible LEDs

The wall-plug efficiency of modern light-emitting diodes (LEDs) has far surpassed all other forms of lighting and is expected to improve further as the lifetime cost of a luminaire is today dominated by the cost of energy. The drive towards higher efficiency inevitably opens the question about the limits of future enhancement. Here, we investigate thermoelectric pumping as a means for improving efficiency in wide-bandgap GaN based LEDs. A forward biased diode can work as a heat pump, which pumps lattice heat into the electrons injected into the active region via the Peltier effect. We experimentally demonstrate a thermally enhanced 450 nm GaN LED, in which nearly fourfold light output power is achieved at 615 K (compared to 295 K room temperature operation), with virtually no reduction in the wall-plug efficiency at bias V < hω/q. This result suggests the possibility of removing bulky heat sinks in high power LED products. A review of recent high-efficiency GaN LEDs suggests that Peltier thermal pumping plays a more important role in a wide range of modern LED structures that previously thought - opening a path to even higher efficiencies and lower lifetime costs for future lighting.MIT Bose Fellowship Progra

A nonlinear optoelectronic filter for electronic signal processing

The conversion of electrical signals into modulated optical waves and back into electrical signals provides the capacity for low-loss radio-frequency (RF) signal transfer over optical fiber. Here, we show that the unique properties of this microwave-photonic link also enable the manipulation of RF signals beyond what is possible in conventional systems. We achieve these capabilities by realizing a novel nonlinear filter, which acts to suppress a stronger RF signal in the presence of a weaker signal independent of their separation in frequency. Using this filter, we demonstrate a relative suppression of 56 dB for a stronger signal having a 1-GHz center frequency, uncovering the presence of otherwise undetectable weaker signals located as close as 3.5 Hz away. The capabilities of the optoelectronic filter break the conventional limits of signal detection, opening up new possibilities for radar and communication systems, and for the field of precision frequency metrology.United States. Dept. of Defense. Assistant Secretary of Defense for Research & Engineering (Air Force Contract FA8721-05-C-0002

Architecture and System Analysis of Microgrids with Peer-to-Peer Electricity Sharing to Create a Marketplace which Enables Energy Access

More than 1.3 billion people in the world lack access to electricity and this energy poverty is a major barrier to human development. This paper describes a new concept of peer-to-peer electricity sharing which creates a marketplace for electricity. In this marketplace, the people who can afford power generating sources such as solar panels can sell electricity to people who are unable to afford generating sources or who might have access to electricity but require more electricity at certain times. These ad-hoc microgrids created by sharing of resources provide affordable electricity and are enabled by a Power Management Unit (PMU) described in this paper.MIT Tata Center for Technology and Desig

Scaling of the photon noise in semiconductor cascade lasers

Antes de ir de férias gostava de fazer alguma publicidade ao curso de bases de dados bibliográficas e Zotero que vou dar na Escola de Verão da FCSH, entre 2 a 4 de Setembro (http://verao.fcsh.unl.pt/Cursos/Bibliografias%20Zotero.html). Para os mais distraídos, o Zotero é um programa de gestão de informação bibliográfica, gratuito, feito por historiadores (é verdade!!!) e que permite gerir todas as nossas referências bibliográficas (e não só!) à medida que navegamos na Internet. Hoje em dia, u..

Optical Detection of Degraded Therapeutic Proteins

The quality of therapeutic proteins such as hormones, subunit and conjugate vaccines, and antibodies is critical to the safety and efficacy of modern medicine. Identifying malformed proteins at the point-of-care can prevent adverse immune reactions in patients; this is of special concern when there is an insecure supply chain resulting in the delivery of degraded, or even counterfeit, drug product. Identification of degraded protein, for example human growth hormone, is demonstrated by applying automated anomaly detection algorithms. Detection of the degraded protein differs from previous applications of machine-learning and classification to spectral analysis: only example spectra of genuine, high-quality drug products are used to construct the classifier. The algorithm is tested on Raman spectra acquired on protein dilutions typical of formulated drug product and at sample volumes of 25 μL, below the typical overfill (waste) volumes present in vials of injectable drug product. The algorithm is demonstrated to c orrectly classify anomalous recombinant human growth hormone (rhGH) with 92% sensitivity and 98% specificity even when the algorithm has only previously encountered high-quality drug product.United States. Defense Advanced Research Projects Agency (Contract N66001-13-C-4025

High-Q CMOS-integrated photonic crystal microcavity devices

Integrated optical resonators are necessary or beneficial in realizations of various functions in scaled photonic platforms, including filtering, modulation, and detection in classical communication systems, optical sensing, as well as addressing and control of solid state emitters for quantum technologies. Although photonic crystal (PhC) microresonators can be advantageous to the more commonly used microring devices due to the former's low mode volumes, fabrication of PhC cavities has typically relied on electron-beam lithography, which precludes integration with large-scale and reproducible CMOS fabrication. Here, we demonstrate wavelength-scale polycrystalline silicon (pSi) PhC microresonators with Qs up to 60,000 fabricated within a bulk CMOS process. Quasi-1D resonators in lateral p-i-n structures allow for resonant defect-state photodetection in all-silicon devices, exhibiting voltage-dependent quantum efficiencies in the range of a few 10 s of %, few-GHz bandwidths, and low dark currents, in devices with loaded Qs in the range of 4,300–9,300; one device, for example, exhibited a loaded Q of 4,300, 25% quantum efficiency (corresponding to a responsivity of 0.31 A/W), 3 GHz bandwidth, and 30 nA dark current at a reverse bias of 30 V. This work demonstrates the possibility for practical integration of PhC microresonators with active electro-optic capability into large-scale silicon photonic systems.United States. Defense Advanced Research Projects Agency. Photonically Optimized Embedded MicroprocessorsUnited States. Dept. of Energy (Science Graduate Fellowship