Compact Emitters Research Articles

Underwater Directional Acoustic Source Based on Pentamode Material

An underwater directional acoustic emitter is conceived with a highly anisotropic lattice material, whose acoustic characteristics manifest strong dependence on the orientation of the lattice material’s principal axis. Exploiting these features, a cylindrical structure made of such anisotropic lattice material is engineered to possess distinct impedance values in different directions, thereby facilitating wave emission along the principal axis while inducing reflection in other directions. Notably, through numerical simulations, it is demonstrated that the emission direction can be effectively manipulated by adjusting the principal axis orientation, concurrently enhancing the emitted power. In contrast to previous directional acoustic structures, the compact emitter presented in this study can get rid of the size-wavelength constraint, enabling effective control of low-frequency waves.

Compact spin-valley-locked perovskite emission.

Circularly polarized light sources with free-space directional emission play a key role in chiroptics1, spintronics2, valleytronics3 and asymmetric photocatalysis4. However, conventional approaches fail to simultaneously realize pure circular polarization, high directionality and large emission angles in a compact emitter. Metal-halide perovskite semiconductors are promising light emitters5-8, but the absence of an intrinsic spin-locking mechanism results in poor emission chirality. Further, device integration has undermined the efficiency and directionality of perovskite chiral emitters. Here we realize compact spin-valley-locked perovskite emitting metasurfaces where spin-dependent geometric phases are imparted into bound states in the continuum via Brillouin zone folding, and thus, photons with different spins are selectively addressed to opposite valleys. Employing this approach, chiral purity of 0.91 and emission angle of 41.0° are simultaneously achieved, with a beam divergence angle of 1.6°. With this approach, we envisage the realization of chiral light-emitting diodes, as well as the on-chip generation of entangled photon pairs.

Transmission Geometry Laser Lighting with a Compact Emitter

Transmission Geometry Laser Lighting with a Compact Emitter

Transmission Geometry Laser Lighting with a Compact Emitter

Laser lighting systems can take many form factors for applications, such as spotlighting, general illumination, or decorative lighting. The use of lasers in conjunction with phosphors for white lighting leads to questions about incorporating the various package elements. Some practical considerations of a transmission geometry system implementing a blue laser and a yellow Ce:YAG single crystal phosphor are discussed, with specific focus on color tuning and the optical efficiency of the single crystal. A compact emitter is demonstrated with examples of modifications to increase the system performance and complexity. Moving from a cool white system to a warm white system is done through the addition of a red light such as a red laser or red phosphor. The single crystal phosphor component needs to allow light to be coupled in from the laser and has high extraction efficiency. A wavelength‐selective reflective coating is implemented to address these concerns, which increases the luminous efficacy of the system. Engineering the phosphor element using this concept may allow for single crystal phosphors to be viable options for future laser lighting systems.

Integrated, Portable, Tunable, and Coherent Terahertz Sources and Sensitive Detectors Based on Layered Superconductors

Current compact emitter and receiver technologies are generally inefficient and impractical at terahertz (THz) frequencies between 0.1 and 10 THz. Hence, a gap exists between mature microwave and developed optical technologies. On-chip, integrated broadly tunable and powerful quantum sources that coherently radiate THz waves between 0.1 and 11 THz (potentially extendable to 15 THz) and with potential output power of >1 mW can be achieved based on quantum tunneling of electron pairs across the stack of intrinsic Josephson junctions (IJJs) naturally present in a single crystal of the layered high- ${T}_{c}$ superconducting Bi2Sr2CaCu2O $_{8+\delta}$ (BSCCO). Such devices have been found to be especially promising solid-state THz sources capable of bridging the entire THz gap, as their wide-frequency tunability range is superior to that obtained from their semiconducting-based rivals, either single resonant-tunneling diodes (RTDs) or THz-quantum cascade lasers (QCLs). Due to the unique electrodynamics of BSCCO, they can also be operated as switching current detectors, paving the way for the realization of on-chip THz-integrated circuits for applications in ultrahigh-speed telecommunications, quantum information, on-chip spectroscopy, and nondestructive sensing, testing, and imaging. This article reviews the history and recent advances in THz sources and detectors based on IJJs with a focus on the application of IJJ THz devices in THz spectroscopy and various types of THz imaging systems such as reflection, transmission, and computed tomography. We show that compact IJJ THz devices with sub-centimeter-sized modules are easy to use in many applications, as they can be regarded as pocket quantum THz torches.

Generation of Continuously Variable-mode Orbital Angular Momentum Beams

Orbital angular momentum (OAM) beam emitters with compact structure and high performance are highly desirable for wireless communication and radar technology. Here, we propose a compact emitter that only consists of a ring resonator and a feed line. Continuously-variable-mode OAM beams are generated by adjusting the wavelength and transmission path. The basic design principle and specific evaluation index are discussed. Both the simulated and experimental results demonstrate that the proposed emitter obtains the capacity of generating variable-modes. This approach opens a way for designing novel OAM beam emitter with desired properties.

Compact UV Nitrogen Laser Pumped by a Pulsed Longitudinal Inductive Discharge

The creation of a compact emitter for an inductive nitrogen laser (λ = 337.1 nm) with the active medium pumped by a pulsed inductive longitudinal discharge of the transformer type is reported for the first time. In the inductive laser head created, the lasing energy attains 0.35 mJ and the lasing pulse length is (25 ± 5) ns (FWHM) depending on the cavity Q-factor. The use of a semiconfocal cavity provides for a near-Gaussian beam profile.

Compact high-efficiency vortex beam emitter based on a silicon photonics micro-ring.

Photonic integrated devices that emit vortex beam carrying orbital angular momentum are becoming key components for multiple applications. Here we propose and demonstrate a high-efficiency vortex beam emitter based on a silicon micro-ring resonator integrated with a metal mirror. Such a compact emitter is capable of generating vortex beams with a high efficiency and small divergence angle. Vector vortex beams of various topological charges are selectively generated by the emitter at different wavelengths with an emission efficiency of up to 37%.

Monolithic high-contrast metastructure for beam-shaping VCSELs

We report a high-contrast metastructure (HCM) mirror as a novel beam-shaping element for vertical-cavity surface-emitting lasers (VCSELs). The metastructure is monolithically integrated as a part of the VCSEL, working both as a microelectromechanical tunable mirror and output beam shaper. While providing broadband, high reflection to support lasing of the VCSEL, its angular transmission characteristics can be tailored to shape the angular profile of the output beam. Various far-field emission patterns are demonstrated for single-mode, 1550 nm VCSELs with different HCM designs. We further demonstrated two-faced VCSELs with different mode profiles from their two mirrors, for the first time, to the best of our knowledge. This bifunctional integrated metastructure opens new avenues to engineer a VCSEL’s emission properties, and shows great promise for applications that desire highly compact emitters integrated on a chip to provide versatile functionalities.

High-directional vortex beam emitter based on Archimedean spiral adiabatic waveguides.

Integrated devices that emit light beams with orbital angular momentum (OAM) are becoming key components for wide-ranging applications. Here we propose and demonstrate a highly directional silicon photonic vortex beam emitter based on a 3-turn Archimedean spiral adiabatic waveguide integrated with an angular grating. Such a compact emitter is capable of generating vortex beams with small divergence angles and high directivity. Various orders of OAM modes can be selectively generated by the emitter at different wavelengths with a side-mode suppression ratio as large as 13.6 dB.

A novel semiconductor-based, fully incoherent amplified spontaneous emission light source for ghost imaging

Initially, ghost imaging (GI) was demonstrated with entangled light from parametric down conversion. Later, classical light sources were introduced with the development of thermal light GI concepts. State-of-the-art classical GI light sources rely either on complex combinations of coherent light with spatially randomizing optical elements or on incoherent lamps with monochromating optics, however suffering strong losses of efficiency and directionality. Here, a broad-area superluminescent diode is proposed as a new light source for classical ghost imaging. The coherence behavior of this spectrally broadband emitting opto-electronic light source is investigated in detail. An interferometric two-photon detection technique is exploited in order to resolve the ultra-short correlation timescales. We thereby quantify the coherence time, the photon statistics as well as the number of spatial modes unveiling a complete incoherent light behavior. With a one-dimensional proof-of-principle GI experiment, we introduce these compact emitters to the field which could be beneficial for high-speed GI systems as well as for long range GI sensing in future applications.

Temperature control of thermal radiation from composite bodies

We demonstrate that recent advances in nanoscale thermal transport and temperature manipulation can be brought to bear on the problem of tailoring thermal radiation from compact emitters. We show that wavelength-scale composite bodies involving complicated arrangements of phase-change chalcogenide (GST) glasses and metals or semiconductors can exhibit large emissivities and partial directivities at mid-infrared wavelengths, a consequence of temperature localization within the GST. We consider multiple object topologies, including spherical, cylindrical, and mushroom-like composites, and show that partial directivity follows from a complicated interplay between particle shape, material dispersion, and temperature localization. Our calculations exploit a recently developed fluctuating-volume current formulation of electromagnetic fluctuations that rigorously captures radiation phenomena in structures with both temperature and dielectric inhomogeneities.

Emission of terahertz radiation from GaN under impact ionization of donors in an electric field

The emission of terahertz radiation from epitaxial n-GaN layers in lateral electric field was found and studied for the first time. Radiation emission was observed in fields exceeding the impurity breakdown threshold. The highest -intensity radiation lines may be associated with intracenter electron transitions between donor levels (Si and O) and electron transitions from the conduction band to donor ground levels. Compact emitters of terahertz radiation operating at temperatures from 4 to 80 K can be created on the basis of n-GaN.

Controlling Neuronal Activity

Back to table of contents Previous article Next article Images in NeuroscienceFull AccessControlling Neuronal ActivityM. Bret Schneider M.D.Viviana Gradinaru B.Sc.Feng Zhang A.B.Karl Deisseroth M.D., Ph.D.,M. Bret Schneider M.D.Search for more papers by this authorViviana Gradinaru B.Sc.Search for more papers by this authorFeng Zhang A.B.Search for more papers by this authorKarl Deisseroth M.D., Ph.D.Search for more papers by this author,Published Online:1 May 2008https://doi.org/10.1176/appi.ajp.2008.08030444AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail With a new technology called optogenetics , it is possible to turn neuronal activity on and off in distinct neuronal populations, using cell-type specific, optically-sensitive, molecular, neuronal activity “switches.” These “switches” are microbial, light-sensitive ion conductance-regulating proteins, exemplified by channelrhodopsin-2 (ChR2) and halorhodopsin (NpHR). They are individually introduced into neuronal populations in the brain and become part of the cellular machinery. Ion flux-regulating activity of these “switches” can be controlled externally with light pulses. ChR2 is a cation channel that allows sodium ions to pass into a neuron after it has been activated by approximately 470 nm blue light (thereby increasing activity of the neuron and increasing action potentials). NpHR is a chloride pump that transfers chloride anions into the neuron after it has been activated by approximately 580 nm yellow light (thereby increasing accumulation of negative charge inside the cell and suppressing activity of the neuron). For application of this technology, light of the proper wavelength is delivered to the brain region of interest using a fiberoptic-based system or a light-emitting diode (LED). ChR2 and NpHR can be controlled independently to either increase action-potential firing of specific target neurons or to suppress neural activity, respectively, in intact tissue. In animal experiments, the LED or fiberoptic can be tethered to an external power source with lightweight flexible connectors, allowing stimulation during normal, freely moving behavior. The genes encoding these proteins are introduced into the brain with viral vectors and are expressed in distinct populations of neurons in vivo using specific DNA promoters fused to the gene, thereby guiding expression only in the cell type of choice. Figure 1. Top: Electrical versus optogenetic neuromodulation; the electrode non-specifically affects all nearby neurons (left), whereas blue or yellow light emitting devices affect only the neurons containing excitatory ChR2 protein (center) or inhibitory NpHR protein (right). (Figure adapted/modified with permission from A.M. Aravanis et al., “An Optical Neural Interface: In Vivo Control of Rodent Motor Cortex With Integrated Fiberoptic and Optogenetic Technology” [J Neural Eng 2007; 4:S143–S156]. Copyright ” J Neural Eng. Bottom left: A prototype implantable light-delivery device based on diode technologies can be directly mounted onto laboratory animals used as disease models (Image courtesy of the Deisseroth Lab). The use of yet more compact emitters may smooth the path to preclinical or clinical use. Bottom right: neurons expressing ChR2 and NpHR can be optically silenced or driven to fire precisely-patterned action potentials (Figure adapted/modified with permission from F. Zhang et al., “Multimodal Fast Optical Interrogation of Neural Circuitry” [Nature 2007; 446:633–639]. Copyright ” Nature.Currently, these molecular “switches” are being used to interrogate the functions of specific cell populations within complex neural circuits of living animals in order to better understand the contribution of defined cell types to behavior. For example, dopamine-releasing neurons are being targeted by this approach, with the goal of understanding the causal role of specific patterns of activity of these cells in behaviors relating to reward and depression. Preclinical work of this kind will help us better understand the circuits involved in human disease. In the long run, clinical studies may eventually allow—for example—the use of NpHR or ChR2 protein to be introduced into human cell types in diseases for which candidate targets of surgical intervention are already known, i.e., the subthalamic nucleus in Parkinson’s disease, the hippocampal seizure foci in epilepsy, and the subgenual cingulate in depression.Stanford, Calif.Address reprint requests to Dr. Tamminga, UT Southwestern Medical Center, Department of Psychiatry, 5323 Harry Hines Blvd., #NE5.110, Dallas, TX 75390-9070; [email protected] (e-mail). Image accepted for publication March 2008 (doi: 10.1176/appi.ajp.2008.08030444). FiguresReferencesCited byDetailsCited ByIvermectin-Activated, Cation-Permeable Glycine Receptors for the Chemogenetic Control of Neuronal Excitation27 September 2016 | ACS Chemical Neuroscience, Vol. 7, No. 12, Vol. 122Neurobiology of Learning and Memory, Vol. 115Developmental Neurobiology, Vol. 72, No. 3Nature Reviews Neuroscience, Vol. 13, No. 4Journal of Molecular Biology, Vol. 405, No. 2Optogenetics – shining light on neurosurgical conditions28 September 2010 | British Journal of Neurosurgery, Vol. 24, No. 6, Vol. 477 Volume 165Issue 5 May, 2008Pages 562-562THE AMERICAN JOURNAL OF PSYCHIATRY May 2008 Volume 165 Number 5 Metrics PDF download History Published online 1 May 2008 Published in print 1 May 2008

A Search for New Emission Nebulae from the SHASSA and VTSS Surveys

As an adjunct to the planetary nebula (PN) search from the AAO/UKST Hα survey, a visual search was conducted for new emission nebulae from the SHASSA and VTSS surveys, outside a Galactic latitude of |b| =1 0 ◦ . Fifteen new objects were found from SHASSA and three from the available fields of VTSS. With one exception, all objects are >5 � across, as smaller nebulae are confused with large numbers of artifacts and compact emitters on these surveys. All previously known PNe larger than this size in the search area, as well as Hewett 1, PG 0108, and PG 0109 were recovered in this blind search. Candidates were selected as discrete, morphologically symmetric Hα enhancements, to differentiate them from the ubiquitous diffuse emission structure of the ISM. These criteria were relaxed for the VTSS survey due to its poorer inherent resolution. Most of the new discoveries are probable Stromgren spheres in the ISM. Some show unusual line ratios (e.g. strong (O iii) or (N ii) emission) based on slit spectroscopy and WHAM data (see Madsen et al. 2006, this volume), suggesting these are ionised by a hot subdwarf or white dwarf star, and may be possible PNe. Our most interesting discovery is a rare bowshock nebula around a bright, previously unnoticed, nova-like cataclysmic variable.