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Showing papers in "Nature Photonics in 2007"


Journal ArticleDOI
TL;DR: An overview of the status of the terahertz technology, its uses and its future prospects are presented in this article, with a focus on the use of the waveband in a wide range of applications.
Abstract: Research into terahertz technology is now receiving increasing attention around the world, and devices exploiting this waveband are set to become increasingly important in a very diverse range of applications. Here, an overview of the status of the technology, its uses and its future prospects are presented.

5,512 citations


Journal ArticleDOI
TL;DR: In this paper, a review describes the recent progress made in creating nanostructured metamaterials with a negative index at optical wavelengths, and discusses some of the devices that could result from these new materials.
Abstract: Artificially engineered metamaterials are now demonstrating unprecedented electromagnetic properties that cannot be obtained with naturally occurring materials. In particular, they provide a route to creating materials that possess a negative refractive index and offer exciting new prospects for manipulating light. This review describes the recent progress made in creating nanostructured metamaterials with a negative index at optical wavelengths, and discusses some of the devices that could result from these new materials.

2,654 citations


Journal ArticleDOI
TL;DR: Microwave photonics has attracted great interest from both the research community and the commercial sector over the past 30 years and is set to have a bright future as mentioned in this paper, which makes it possible to have functions in microwave systems that are complex or even not directly possible in the radiofrequency domain and also creates new opportunities for telecommunication networks.
Abstract: Microwave photonics, which brings together the worlds of radiofrequency engineering and optoelectronics, has attracted great interest from both the research community and the commercial sector over the past 30 years and is set to have a bright future. The technology makes it possible to have functions in microwave systems that are complex or even not directly possible in the radiofrequency domain and also creates new opportunities for telecommunication networks. Here we introduce the technology to the photonics community and summarize recent research and important applications.

2,354 citations


Journal ArticleDOI
TL;DR: The design and realization of metallic nanostructures with tunable plasmon resonances has been greatly advanced by combining a wealth of nanofabrication techniques with advances in computational electromagnetic design.
Abstract: The design and realization of metallic nanostructures with tunable plasmon resonances has been greatly advanced by combining a wealth of nanofabrication techniques with advances in computational electromagnetic design. Plasmonics — a rapidly emerging subdiscipline of nanophotonics — is aimed at exploiting both localized and propagating surface plasmons for technologically important applications, specifically in sensing and waveguiding. Here we present a brief overview of this rapidly growing research field.

2,090 citations


Journal ArticleDOI
TL;DR: This work presents the design of a non-magnetic cloak operating at optical frequencies, and the principle and structure of the proposed cylindrical cloak are analysed and the general recipe for the implementation of such a device is provided.
Abstract: Artificially structured metamaterials have enabled unprecedented flexibility in manipulating electromagnetic waves and producing new functionalities, including the cloak of invisibility based on coordinate transformation1,2,3. Unlike other cloaking approaches4,5,6, which are typically limited to subwavelength objects, the transformation method allows the design of cloaking devices that render a macroscopic object invisible. In addition, the design is not sensitive to the object that is being cloaked. The first experimental demonstration of such a cloak at microwave frequencies was recently reported7. We note, however, that that design7 cannot be implemented for an optical cloak, which is certainly of particular interest because optical frequencies are where the word ‘invisibility’ is conventionally defined. Here we present the design of a non-magnetic cloak operating at optical frequencies. The principle and structure of the proposed cylindrical cloak are analysed, and the general recipe for the implementation of such a device is provided.

1,953 citations


Journal ArticleDOI
TL;DR: In this paper, the state-of-the-art and future prospects for terahertz quantum-cascade laser systems are reviewed, including efforts to increase their operating temperatures, deliver higher output powers and emit longer wavelengths.
Abstract: Six years after their birth, terahertz quantum-cascade lasers can now deliver milliwatts or more of continuous-wave coherent radiation throughout the terahertz range — the spectral regime between millimetre and infrared wavelengths, which has long resisted development. This paper reviews the state-of-the-art and future prospects for these lasers, including efforts to increase their operating temperatures, deliver higher output powers and emit longer wavelengths.

1,426 citations


Journal ArticleDOI
TL;DR: The current state of research and future directions in quantum key distribution and quantum networks are reviewed in this paper, with a special emphasis on quantum key distributions and quantum key sharing in quantum networks.
Abstract: Quantum communication, and indeed quantum information in general, has changed the way we think about quantum physics In 1984 and 1991, the first protocol for quantum cryptography and the first application of quantum non-locality, respectively, attracted a diverse field of researchers in theoretical and experimental physics, mathematics and computer science Since then we have seen a fundamental shift in how we understand information when it is encoded in quantum systems We review the current state of research and future directions in this new field of science with special emphasis on quantum key distribution and quantum networks

1,420 citations


Journal ArticleDOI
Wolfgang Ackermann1, G. Asova, Valeri Ayvazyan2, A. Azima2  +154 moreInstitutions (16)
TL;DR: In this paper, the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured.
Abstract: We report results on the performance of a free-electron laser operating at a wavelength of 13.7 nm where unprecedented peak and average powers for a coherent extreme-ultraviolet radiation source have been measured. In the saturation regime, the peak energy approached 170 J for individual pulses, and the average energy per pulse reached 70 J. The pulse duration was in the region of 10 fs, and peak powers of 10 GW were achieved. At a pulse repetition frequency of 700 pulses per second, the average extreme-ultraviolet power reached 20 mW. The output beam also contained a significant contribution from odd harmonics of approximately 0.6% and 0.03% for the 3rd (4.6 nm) and the 5th (2.75 nm) harmonics, respectively. At 2.75 nm the 5th harmonic of the radiation reaches deep into the water window, a wavelength range that is crucially important for the investigation of biological samples.

1,390 citations


Journal ArticleDOI
TL;DR: In this paper, the trade-offs between resonantly enhanced group delay, device size, insertion loss and operational bandwidth are analyzed for various delay-line designs, and a large fractional group delay exceeding 10 bits is achieved for bit rates as high as 20 Gbps.
Abstract: On-chip optical buffers based on waveguide delay lines might have significant implications for the development of optical interconnects in computer systems. Silicon-on-insulator (SOI) submicrometre photonic wire waveguides are used, because they can provide strong light confinement at the diffraction limit, allowing dramatic scaling of device size. Here we report on-chip optical delay lines based on such waveguides that consist of up to 100 microring resonators cascaded in either coupled-resonator or all-pass filter (APF) configurations. On-chip group delays exceeding 500 ps are demonstrated in a device with a footprint below 0.09 mm2. The trade-offs between resonantly enhanced group delay, device size, insertion loss and operational bandwidth are analysed for various delay-line designs. A large fractional group delay exceeding 10 bits is achieved for bit rates as high as 20 Gbps. Measurements of system-level metrics as bit error rates for different bit rates demonstrate error-free operation up to 5 Gbps.

1,161 citations


Journal ArticleDOI
TL;DR: Optical thin-film materials with low refractive index for broadband elimination of Fresnel reflection were used in this paper, where the authors proposed a method to eliminate the reflection in optical thin-films.
Abstract: Optical thin-film materials with low refractive index for broadband elimination of Fresnel reflection

1,153 citations


Journal ArticleDOI
TL;DR: In this paper, a solution-processable core-shell quantum dots with a CdSe core and a ZnS or CdS/ZnS shell were used as emissive layers in the devices.
Abstract: Quantum-dot-based LEDs are characterized by pure and saturated emission colours with narrow bandwidth, and their emission wavelength is easily tuned by changing the size of the quantum dots. However, the brightness, efficiency and lifetime of LEDs need to be improved to meet the requirements of commercialization in the near future. Here, we report red, orange, yellow and green LEDs with maximum luminance values of 9,064, 3,200, 4,470 and 3,700 cd m−2, respectively, the highest values reported so far. Solution-processable core–shell quantum dots with a CdSe core and a ZnS or CdS/ZnS shell were used as emissive layers in the devices. By optimizing the thicknesses of the constituent layers of the devices, we were able to develop quantum-dot-based LEDs with improved electroluminescent efficiency (1.1–2.8 cd A−1), low turn-on voltages (3–4 V) and long operation lifetimes. These findings suggest that such quantum-dot-based LEDs will be promising for use in flat-panel displays.

Journal ArticleDOI
TL;DR: Some of the exciting developments so far in miniaturized optofluidic platforms bring fluid and light together and exploit their microscale interaction for a large variety of applications are overviewed.
Abstract: The realization of miniaturized optofluidic platforms offers potential for achieving more functional and more compact devices. Such integrated systems bring fluid and light together and exploit their microscale interaction for a large variety of applications. The high sensitivity of compact microphotonic devices can generate effective microfluidic sensors, with integration capabilities. By turning the technology around, the exploitation of fluid properties holds the promise of highly flexible, tunable or reconfigurable microphotonic devices. We overview some of the exciting developments so far.

Journal ArticleDOI
TL;DR: In this paper, the authors describe the recent experimental progress in the control of spontaneous emission by manipulating optical modes with photonic crystals, which can contribute to the evolution of a variety of applications, including illumination, display, optical communication, solar energy and even quantum information systems.
Abstract: We describe the recent experimental progress in the control of spontaneous emission by manipulating optical modes with photonic crystals. It has been clearly demonstrated that the spontaneous emission from light emitters embedded in photonic crystals can be suppressed by the so-called photonic bandgap, whereas the emission efficiency in the direction where optical modes exist can be enhanced. Also, when an artificial defect is introduced into the photonic crystal, a photonic nanocavity is produced that can interact with light emitters. Cavity quality factors, or Q factors, of up to 2 million have been realized while maintaining very small mode volumes, and both spontaneous-emission modification (the Purcell effect) and strong-coupling phenomena have been demonstrated. The use of photonic crystals and nanocavities to manipulate spontaneous emission will contribute to the evolution of a variety of applications, including illumination, display, optical communication, solar energy and even quantum-information systems.

Journal ArticleDOI
Andrew J. Shields1
TL;DR: In this paper, a review of single-photon sources based on the emission of a single semiconductor quantum dot is presented, which suggests that it may be possible to realize compact, robust, LED-like semiconductor devices for quantum light generation.
Abstract: Lasers and LEDs have a statistical distribution in the number of photons emitted within a given time interval. Applications exploiting the quantum properties of light require sources for which either individual photons, or pairs, are generated in a regulated stream. Here we review recent research on single-photon sources based on the emission of a single semiconductor quantum dot. In just a few years remarkable progress has been made in generating indistinguishable single photons and entangled-photon pairs using such structures. This suggests that it may be possible to realize compact, robust, LED-like semiconductor devices for quantum light generation.

Journal ArticleDOI
TL;DR: In this paper, the first laser operation in an electrically pumped metallic-coated nanocavity formed by a semiconductor heterostructure encapsulated in a thin gold film was reported.
Abstract: Metallic cavities can confine light to volumes with dimensions considerably smaller than the wavelength of light. It is commonly believed, however, that the high losses in metals are prohibitive for laser operation in small metallic cavities. Here we report for the first time laser operation in an electrically pumped metallic-coated nanocavity formed by a semiconductor heterostructure encapsulated in a thin gold film. The demonstrated lasers show a low threshold current and their dimensions are smaller than the smallest electrically pumped lasers reported so far. With dimensions comparable to state-of-the-art electronic transistors and operating at low power and high speed, they are a strong contender as basic elements in digital photonic very large-scale integration. Furthermore we demonstrate that metallic-coated nanocavities with modal volumes smaller than dielectric cavities can have moderate quality factors.

Journal ArticleDOI
TL;DR: There is an intense drive at the moment towards paper-like displays, devices having a high reflectivity and contrast to provide viewability in a variety of environments, particularly in sunlight where emissive or backlit devices perform very poorly.
Abstract: In our information-rich world, it is becoming increasingly important to develop technologies capable of displaying dynamic and changeable data, for reasons ranging from value-added advertising to environmental sustainability. There is an intense drive at the moment towards paper-like displays, devices having a high reflectivity and contrast to provide viewability in a variety of environments, particularly in sunlight where emissive or backlit devices perform very poorly. The list of possible technologies is extensive, including electrophoretic, cholesteric liquid crystalline, electrochromic, electrodewetting, interferometric and more. Despite tremendous advances, the key drawback of all these existing display options relates to colour. As soon as an RGB (red, green and blue) colour filter or spatially modulated colour scheme is implemented, substantial light losses are inevitable even if the intrinsic reflectivity of the material is very good.

Journal ArticleDOI
TL;DR: The keys generated in the first quantum key distribution experiment to enable the creation of secure keys over 42 dB channel loss and 200 km of optical fibre are secure against both general collective attacks on individual photons and a specific collective attack on multiphotons.
Abstract: We report the first quantum key distribution (QKD) experiment to enable the creation of secure keys over 42 dB channel loss and 200 km of optical fibre. We used the differential phase shift QKD (DPS-QKD) protocol, implemented with a 10-GHz clock frequency and superconducting single-photon detectors (SSPD) based on NbN nanowires. The SSPD offers a very low dark count rate (a few Hz) and small timing jitter (60 ps, full width at half maximum, FWHM). These characteristics allowed us to achieve a 12.1 bit s–1 secure key rate over 200 km of fibre, which is the longest terrestrial QKD over a fibre link yet demonstrated. Moreover, this is the first 10-GHz clock QKD system to enable secure key generation. The keys generated in our experiment are secure against both general collective attacks on individual photons and a specific collective attack on multiphotons, known as a sequential unambiguous state discrimination (USD) attack.

Journal ArticleDOI
TL;DR: In this paper, a surface-emitting laser with a single-layer high-index-contrast subwavelength grating is proposed to provide both efficient optical feedback and control of the wavelength and polarization of emitted light.
Abstract: Semiconductor diode lasers can be used in a variety of applications including telecommunications, displays, solid-state lighting, sensing and printing. Among them, vertical-cavity surface-emitting lasers1,2,3 (VCSELs) are particularly promising. Because they emit light normal to the constituent wafer surface, it is possible to extract light more efficiently and to fabricate two-dimensional device arrays. A VCSEL contains two distributed Bragg reflector (DBR) mirrors for optical feedback, separated by a very short active gain region. Typically, the reflectivity of the DBRs must exceed 99.5% in order for the VCSEL to lase. However, the realization of practical VCSELs that can be used over a broad spectrum of wavelengths has been hindered by the poor optical and thermal properties of candidate DBR materials4,5,6. In this Letter, we present surface-emitting lasers that incorporate a single-layer high-index-contrast subwavelength grating7,8 (HCG). The HCG provides both efficient optical feedback and control of the wavelength and polarization of the emitted light. Such integration reduces the required VCSEL mirror epitaxial thickness by a factor of two and increases fabrication tolerance. This work will directly influence the future designs of VCSELs, photovoltaic cells and light-emitting diodes at blue–green, 1.3–1.55 µm and mid- to far-infrared wavelengths.

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate an all-optical modulator in which efficient interaction between two light beams at different wavelengths is achieved by converting them into co-propagating surface plasmon polaritons interacting by means of a thin layer of CdSe quantum dots (QDs).
Abstract: Photonics is a promising candidate technology for information processing, communication and data storage. Essential building blocks, such as logic elements and modulators, have been demonstrated. However, because of weak nonlinear light–matter interactions, these components typically require high power densities and large interaction volumes, limiting their application in dense chip-based integration. A solution may be found in surface plasmon polaritons (SPPs), guided electromagnetic waves that propagate with high field confinement along a metal–dielectric interface. We demonstrate an all-optical modulator in which efficient interaction between two light beams at different wavelengths is achieved by converting them into co-propagating SPPs interacting by means of a thin layer of CdSe quantum dots (QDs). The high SPP field confinement and high QD-absorption cross-section enable optical modulation at low power densities (~10^2 W cm^(-2)) in micrometre-scale planar devices.

Journal ArticleDOI
TL;DR: In this article, the first polarization-transparent add-drop filter from polarization-sensitive microring resonators is presented, which shows almost complete elimination of polarization sensitivity over the 60nm bandwidth measured, while maintaining outstanding filter performance.
Abstract: Microphotonic structures that strongly confine light, such as photonic crystals and micron-sized resonators, have unique characteristics that could radically advance technology1,2,3,4,5,6. However, such devices cannot be used in most applications because of their inherent polarization sensitivity; they respond differently to light polarized along different axes7,8,9. To take advantage of the distinctive properties of these structures, a general, integrated, broadband solution to their polarization sensitivity is needed. Here, we show the first demonstration of such a solution. It enables arbitrary, polarization-sensitive, strong-confinement (SC) microphotonic devices to be rendered insensitive (transparent) to the input polarization at all wavelengths of operation. To test our approach, we create the first polarization-transparent add–drop filter from polarization-sensitive microring resonators. It shows almost complete elimination of polarization sensitivity over the 60-nm bandwidth measured, while maintaining outstanding filter performance. This development is a milestone for SC microphotonics, allowing the applications of photonic-crystal and microring devices to several areas, including communications, spectroscopy and remote sensing.

Journal ArticleDOI
TL;DR: In this article, the authors describe how semiconductor quantum-dot structures can provide an efficient means of amplifying and generating ultrafast (of the order of 100 fs), high-power and low-noise optical pulses, with the potential to boost the repetition rate of the pulses to beyond 1 THz.
Abstract: Semiconductor lasers are convenient and compact sources of light, offering highly efficient operation, direct electrical control and integration opportunities. In this review we describe how semiconductor quantum-dot structures can provide an efficient means of amplifying and generating ultrafast (of the order of 100 fs), high-power and low-noise optical pulses, with the potential to boost the repetition rate of the pulses to beyond 1 THz. Such device designs are opening up new possibilities in ultrafast science and technology.

Journal ArticleDOI
TL;DR: In this article, the authors show that the iridescent scales of the Morpho sulkowskyi butterfly give a different optical response to different individual vapours, and that this optical response dramatically outperforms that of existing nano-engineered photonic sensors.
Abstract: Tropical Morpho butterflies are famous for their brilliant iridescent colours, which arise from ordered arrays of scales on their wings. Here we show that the iridescent scales of the Morpho sulkowskyi butterfly give a different optical response to different individual vapours, and that this optical response dramatically outperforms that of existing nano-engineered photonic sensors. The reflectance spectra of the scales provide information about the nature and concentration of the vapours, allowing us to identify a range of closely related vapours–water, methanol, ethanol and isomers of dichloroethylene when they are analysed individually. By comparing the reflectance as a function of time for different vapours, we deduce that wing regions with scale structures of differing spatial periodicity give contributions to the overall spectral response at different wavelengths. Our optical model explains the effect of different components of the wing scales on the vapour response, and could steer the design of new man-made optical gas sensors.

Journal ArticleDOI
TL;DR: In this article, a line-by-line pulse shaping method was proposed to exploit the advantages of pulse shaping and frequency combs simultaneously, in order to scale towards high waveform complexity.
Abstract: Pulse-shaping techniques, in which user-specified, ultrashort-pulse fields are synthesized by means of parallel manipulation of optical Fourier components, have now been widely adopted1,2,3,4,5,6. Mode-locked lasers producing combs of frequency-stabilized spectral lines have resulted in revolutionary advances in frequency metrology7,8,9,10,11. However, until recently, pulse shapers addressed spectral lines in groups, at low spectral resolution. Line-by-line pulse shaping12, in which spectral lines are resolved and manipulated individually, leads to a fundamentally new regime for optical arbitrary waveform generation13, in which the advantages of pulse shaping and of frequency combs are exploited simultaneously. Here we demonstrate programmable line-by-line shaping of more than 100 spectral lines, which constitutes a significant step in scaling towards high waveform complexity. Optical arbitrary waveform generation promises to have an impact both in optical science (allowing, for example, coherent control generalizations of comb-based time–frequency spectroscopies10) and in technology (enabling new truly coherent multiwavelength processing concepts for spread-spectrum lightwave communications and light detection and ranging, lidar).

Journal ArticleDOI
TL;DR: In this paper, the first realization of optical microring resonators in submicrometre thin films of lithium niobate was reported, where high-index contrast films were produced by an improved crystal-ion-slicing and bonding technique using benzocyclobutene.
Abstract: Optical microresonators have recently attracted growing attention in the photonics community1. Their applications range from quantum electrodynamics to sensors and filtering devices for optical telecommunication systems, where they will probably become an essential building block2. Integration of nonlinear and electro–optical properties in resonators represents a very stimulating challenge, as it would incorporate new and more advanced functionality. Lithium niobate is an excellent candidate material, being an established choice for electro–optic and nonlinear optical applications. Here we report on the first realization of optical microring resonators in submicrometre thin films of lithium niobate. High-index-contrast films are produced by an improved crystal-ion-slicing and bonding technique using benzocyclobutene. The rings have radius R = 100 µm, and their transmission spectrum has been tuned using the electro–optic effect. These results open new possibilities for the use of lithium niobate in chip-scale integrated optical devices and nonlinear optical microcavities.

Journal ArticleDOI
TL;DR: In this article, a solution-processed photodetector that exhibits D* (normalized detectivity) greater than 5 × 1012 Jones (a unit of detectivity equivalent to cm-Hz1/2 W−1) was presented.
Abstract: One billion image sensors worldwide render optical images as digital photographs in video cameras, still cameras and camera phones. These silicon-based sensors monolithically integrate photodetection with electronic readout. However, silicon photodiodes rely on a smaller bandgap than that required for visible detection; this degrades visible-wavelength sensitivity and produces unwanted infrared sensitivity. Thin-film top-surface visible photodetectors have therefore been investigated based on amorphous1, organic2 and colloidal quantum-dot3 semiconductors. However, none of these devices has exhibited visible sensitivity approaching that of silicon. Here we report a sensitive solution-processed photodetector that, across the entire visible spectrum, exhibits D* (normalized detectivity) greater than 5 × 1012 Jones (a unit of detectivity equivalent to cm Hz1/2 W−1). A photoconductive gain of >100 has been measured, facilitating high-fidelity electronic readout, and the linear dynamic range is greater than 60 dB, as required for high-contrast applications. These photodetectors are also compatible with flexible organic-based electronics.

Journal ArticleDOI
TL;DR: In this paper, the authors describe time-domain measurements on photonic-crystal cavities with the highest Q among wavelength-scale cavities, and show directly that photons are trapped for one nanosecond.
Abstract: Light is intrinsically very difficult to store in a small space. The ability to trap photons for a long time (photon lifetime, τph) and to slow the propagation of light plays a significant role in quantum information1,2,3 and optical processing4,5,6. Photonic-crystal cavities with an ultrahigh quality factor (Q) are attracting attention7,8 because of their extremely small volume; however, high-Q demonstrations have been accomplished only with spectral measurements9,10,11. Here we describe time-domain measurements on photonic-crystal cavities with the highest Q among wavelength-scale cavities, and show directly that photons are trapped for one nanosecond. These techniques constitute clear and accurate ways of investigating ultrasmall and long τph systems. We also show that optical pulses are delayed for ∼1.45 ns, corresponding to light propagation at ∼2×10−5 c the speed of light in a vacuum, which is the slowest for any dielectric slow-light medium. Furthermore, we succeeded in dynamically changing the Q within the τph, which is key to realizing the dynamic control of light12,13 and photon-trapping memory14.

Journal ArticleDOI
TL;DR: In this paper, the authors propose a cohesive plan for nanophotonics to maximize its impact on the market and the next generation of technology, by formulating a unified plan.
Abstract: Nanophotonics has emerged as an exciting new arena concerned with the interaction of light with nanostructured materials. But if nanophotonics is to maximize its impact on the market and the next generation of technology, those within the field will need to form a cohesive plan.

Journal ArticleDOI
TL;DR: In this paper, a quantum-dot-based single-photon source with a measured singlephoton emission rate of 4.0MHz (31MHz into the first lens, with an extraction efficiency of 38%) due to the suppression of exciton dark states was demonstrated.
Abstract: Optoelectronic devices that provide non-classical light states on demand have a broad range of applications in quantum information science1, including quantum‐key‐distribution systems2, quantum lithography3 and quantum computing4. Single-photon sources5,6 in particular have been demonstrated to outperform key distribution based on attenuated classical laser pulses7. Implementations based on individual molecules8, nitrogen vacancy centres9 or dopant atoms10 are rather inefficient owing to low emission rates, rapid saturation and the lack of mature cavity technology. Promising single-photon-source designs combine high-quality microcavities11 with quantum dots as active emitters12. So far, the highest measured single-photon rates are ∼ 200 kHz using etched micropillars13,14. Here, we demonstrate a quantum-dot-based single-photon source with a measured single-photon emission rate of 4.0 MHz (31 MHz into the first lens, with an extraction efficiency of 38%) due to the suppression of exciton dark states. Furthermore, our microcavity design provides mechanical stability, and voltage-controlled tuning of the emitter/mode resonance and of the polarization state.

Journal ArticleDOI
TL;DR: In this paper, a doped, crosslinked organic EO polymer was incorporated into hybrid polymer/sol-gel waveguide modulator devices with exceptional performance, achieving in-device EO coefficients that are five to six times larger than those of the benchmark inorganic material.
Abstract: Electro–optic (EO) modulators are typically made from inorganic materials such as LiNbO3, but replacing them with organic EO materials, that is, ones with optical properties that change in response to an electric field, could be a promising alternative because they offer large bandwidth, ease of processing and relatively low cost. Here we incorporate a doped, crosslinked organic EO polymer into hybrid polymer/sol–gel waveguide modulator devices with exceptional performance. The half-wave voltages of the resulting Mach–Zehnder (MZ) and phase modulators at 1550 nm are 1 V and 2.5 V, respectively. The unique properties of the sol–gel cladding materials used in the hybrid structure result in a 100% device poling efficiency, leading to respective in-device EO coefficients of 138 pm V–1 and 170 pm V–1 in the MZ and phase modulators. These results are the first to show in-device EO coefficients that are five to six times larger than those of the benchmark inorganic material.

Journal ArticleDOI
TL;DR: In this article, an atomic magnetometer based on a millimetre-scale microfabricated alkali vapour cell with sensitivity below 70 fT −1/2 was presented.
Abstract: Highly sensitive magnetometers capable of measuring magnetic fields below 1 pT have an impact on areas as diverse as geophysical surveying1, the detection of unexploded ordinance2, space science3, nuclear magnetic resonance4,5, health care6 and perimeter and remote monitoring. Recently, it has been shown that laboratory optical magnetometers7,8, based on the precession of the spins of alkali atoms in the vapour phase, could achieve sensitivities in the femtotesla range, comparable to9,10,11,12, or even exceeding13, those of superconducting quantum interference devices6. We demonstrate here an atomic magnetometer based on a millimetre-scale microfabricated alkali vapour cell with sensitivity below 70 fT Hz−1/2. Additionally, we use a simplified optical configuration that requires only a single low-power laser. This result suggests that millimetre-scale, low-power femtotesla magnetometers are feasible, and we support this proposition with a simple sensitivity scaling analysis. Such an instrument would greatly expand the range of applications in which atomic magnetometers could be used.