Integrated Compact Optical Vortex Beam Emitters Cai, Xinlun; Wang, Jianwei; Strain, Michael J. ...
Science (American Association for the Advancement of Science),
10/2012, Volume:
338, Issue:
6105
Journal Article
Peer reviewed
Open access
Emerging applications based on optical beams carrying orbital angular momentum (OAM) will probably require photonic integrated devices and circuits for miniaturization, improved performance, and ...enhanced functionality. We demonstrate silicon-integrated optical vortex emitters, using angular gratings to extract light confined in whispering gallery modes with high OAM into free-space beams with well-controlled amounts of OAM. The smallest device has a radius of 3.9 micrometers. Experimental characterization confirms the theoretical prediction that the emitted beams carry exactly defined and adjustable OAM. Fabrication of integrated arrays and demonstration of simultaneous emission of multiple identical optical vortices provide the potential for large-scale integration of optical vortex emitters on complementary metal-oxide-semiconductor compatible silicon chips for wide-ranging applications.
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Terahertz radiation encompasses a wide band of the electromagnetic spectrum, spanning from microwaves to infrared light, and is a particularly powerful tool for both fundamental scientific research ...and applications such as security screening, communications, quality control, and medical imaging. Considerable information can be conveyed by the full polarization state of terahertz light, yet to date, most time-domain terahertz detectors are sensitive to just one polarization component. Here we demonstrate a nanotechnology-based semiconductor detector using cross-nanowire networks that records the full polarization state of terahertz pulses. The monolithic device allows simultaneous measurements of the orthogonal components of the terahertz electric field vector without cross-talk. Furthermore, we demonstrate the capabilities of the detector for the study of metamaterials.
We demonstrate efficient generation of correlated photon pairs by spontaneous four wave mixing in a 5 μm radius silicon ring resonator in the telecom band around 1550 nm. By optically pumping our ...device with a 200 μW continuous wave laser, we obtain a pair generation rate of 0.2 MHz and demonstrate photon time correlations with a coincidence-to-accidental ratio as high as 250. The results are in good agreement with theoretical predictions and show the potential of silicon micro-ring resonators as room temperature sources for integrated quantum optics applications.
Current and previous psychopathology in bariatric surgery candidates is believed to be common. Accurate prevalence estimates, however, are difficult to obtain given that bariatric surgery candidates ...often wish to appear psychiatrically healthy when undergoing psychiatric evaluation for approval for surgery. Also, structured diagnostic assessments have been infrequently used.
The present report concerned 199 patients enrolled in the longitudinal assessment of bariatric surgery study, who also participated in the longitudinal assessment of bariatric surgery-3 psychopathology substudy. The setting was 3 university hospitals, 1 private not-for-profit research institute, and 1 community hospital. All the patients were interviewed independently of the usual preoperative psychosocial evaluation process. The patients were explicitly informed that the data would not be shared with the surgical team unless certain high-risk behaviors, such as suicidality, that could lead to adverse perioperative outcomes were reported.
Most of the patients were women (82.9%) and white (nonwhite 7.6%, Hispanic 5.0%). The median age was 46.0 years, and the median body mass index was 44.9 kg/m2. Of the 199 patients, 33.7% had ≥1 current Axis I disorder, and 68.8% had ≥1 lifetime Axis I disorder. Also, 38.7% had a lifetime history of a major depressive disorder, and 33.2% had a lifetime diagnosis of alcohol abuse or dependence. All these rates were much greater than the population-based prevalence rates obtained for this age group in the National Comorbidity Survey-Replication Study. Also, 13.1% had a lifetime diagnosis and 10.1% had a current diagnosis of a binge eating disorder.
The current and lifetime rates of psychopathology are high in bariatric surgery candidates, and the lifetime rates of affective disorder and alcohol use disorders are particularly prominent. Finally, binge eating disorder is present in approximately 1 in 10 bariatric surgery candidates.
The ability to process optical signals without passing into the electrical domain has always attracted the attention of the research community. Processing photons by photons unfolds new scenarios, in ...principle allowing for unseen signal processing and computing capabilities. Optical computation can be seen as a large scientific field in which researchers operate, trying to find solutions to their specific needs by different approaches; although the challenges can be substantially different, they are typically addressed using knowledge and technological platforms that are shared across the whole field. This significant know-how can also benefit other scientific communities, providing lateral solutions to their problems, as well as leading to novel applications. The aim of this Roadmap is to provide a broad view of the state-of-the-art in this lively scientific research field and to discuss the advances required to tackle emerging challenges, thanks to contributions authored by experts affiliated to both academic institutions and high-tech industries. The Roadmap is organized so as to put side by side contributions on different aspects of optical processing, aiming to enhance the cross-contamination of ideas between scientists working in three different fields of photonics: optical gates and logical units, high bit-rate signal processing and optical quantum computing. The ultimate intent of this paper is to provide guidance for young scientists as well as providing research-funding institutions and stake holders with a comprehensive overview of perspectives and opportunities offered by this research field.
The heterogeneous integration of pre-fabricated lithium niobate photonic waveguide devices onto a silicon nitride waveguide platform via a transfer-printing approach has been demonstrated for the ...first time. A fabrication process was developed to make free-standing lithium niobate membrane devices compatible with back-end integration onto photonic integrated circuits. Micro-ring resonators in membrane format were lithographically defined by using laser direct writing and plasma dry etching. The lithium niobate micro-ring resonators were then transferred from their host substrate and released onto a silicon nitride waveguide chip. An all-pass ring resonator transmission spectrum was obtained in the 1.5 µm to 1.6 µm wavelength range, with a measured loaded Q-factor larger than 3.2 × 10 4 .
Harnessing the full complexity of optical fields requires the complete control of all degrees of freedom within a region of space and time—an open goal for present-day spatial light modulators, ...active metasurfaces and optical phased arrays. Here, we resolve this challenge with a programmable photonic crystal cavity array enabled by four key advances: (1) near-unity vertical coupling to high-finesse microcavities through inverse design; (2) scalable fabrication by optimized 300 mm full-wafer processing; (3) picometre-precision resonance alignment using automated, closed-loop ‘holographic trimming’; and (4) out-of-plane cavity control via a high-speed μLED array. Combining each, we demonstrate the near-complete spatiotemporal control of a 64 resonator, two-dimensional spatial light modulator with nanosecond- and femtojoule-order switching. Simultaneously operating wavelength-scale modes near the space–bandwidth and time–bandwidth limits, this work opens a new regime of programmability at the fundamental limits of multimode optical control.Panuski et al. demonstrate a programmable photonic crystal cavity array, enabling the spatiotemporal control of a 64 resonator, two-dimensional spatial light modulator with nanosecond- and femtojoule-order switching.
The ability to rapidly switch between orbital angular momentum modes of light has important implications for future classical and quantum systems. In general, orbital angular momentum beams are ...generated using free-space bulk optical components where the fastest reconfiguration of such systems is around a millisecond using spatial light modulators. In this work, an extremely compact optical vortex emitter is demonstrated with the ability to actively tune between different orbital angular momentum modes. The emitter is tuned using a single electrically contacted thermo-optical control, maintaining device simplicity and micron scale footprint. On-off keying and orbital angular momentum mode switching are achieved at rates of 10 μs and 20 μs respectively.
Photonic technologies lack non-invasive monitoring tools to inspect the light inside optical waveguides. This is one of the main barriers to large scale integration, even though photonic platforms ...are potentially ready to host thousands of elements on a single chip. Here, we demonstrate non-invasive light observation in silicon photonics devices by exploiting photon interaction with intra-gap energy states localized at the waveguide surface. Light intensity is monitored by measuring the electric conductance of the silicon core through a capacitive access to the waveguide. The electric contacts are located at suitable distance from the waveguide core, thus introducing no measurable extra-photon absorption and a phase perturbation as low as 0.2 mrad, comparable to thermal fluctuations below 3 mK. Light monitoring with a sensitivity of -30 dBm and a dynamic range of 40 dB is demonstrated in waveguides and high-Q resonators, and for the tuning of coupled-resonator optical filters. This approach realizes a ContactLess Integrated Photonic Probe (CLIPP), that is simple, inherently CMOS compatible, non-invasive and scalable to hundreds of probing points per chip. The CLIPP concept provides a viable route to real-time conditioning and feedback control of densely-integrated photonic systems.
A transfer printing (TP) method is presented for the micro-assembly of integrated photonic devices from suspended membrane components. Ultra thin membranes with thickness of 150nm are directly ...printed without the use of mechanical support and adhesion layers. By using a correlation alignment scheme vertical integration of single-mode silicon waveguides is achieved with an average placement accuracy of 100±70nm. Silicon (Si) μ-ring resonators are also fabricated and show controllable optical coupling by varying the lateral absolute position to an underlying Si bus waveguide.
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