Holographic spectrum-splitting optical systems for solar photovoltaics

NASA Astrophysics Data System (ADS)

Zhang, Deming

Solar energy is the most abundant source of renewable energy available. The relatively high cost prevents solar photovoltaic (PV) from replacing fossil fuel on a larger scale. In solar PV power generation the cost is reduced with more efficient PV technologies. In this dissertation, methods to improve PV conversion efficiency with holographic optical components are discussed. The tandem multiple-junction approach has achieved very high conversion efficiency. However it is impossible to manufacture tandem PV cells at a low cost due to stringent fabrication standards and limited material types that satisfy lattice compatibility. Current produced by the tandem multi-junction PV cell is limited by the lowest junction due to series connection. Spectrum-splitting is a lateral multi-junction concept that is free of lattice and current matching constraints. Each PV cell can be optimized towards full absorption of a spectral band with tailored light-trapping schemes. Holographic optical components are designed to achieve spectrum-splitting PV energy conversion. The incident solar spectrum is separated onto multiple PV cells that are matched to the corresponding spectral band. Holographic spectrum-splitting can take advantage of existing and future low-cost technologies that produces high efficiency thin-film solar cells. Spectrum-splitting optical systems are designed and analyzed with both transmission and reflection holographic optical components. Prototype holograms are fabricated and high optical efficiency is achieved. Light-trapping in PV cells increases the effective optical path-length in the semiconductor material leading to improved absorption and conversion efficiency. It has been shown that the effective optical path length can be increased by a factor of 4n2 using diffusive surfaces. Ultra-light-trapping can be achieved with optical filters that limit the escape angle of the diffused light. Holographic reflection gratings have been shown to act as angle-wavelength selective filters that can function as ultra-light-trapping filters. Results from an experimental reflection hologram are used to model the absorption enhancement factor for a silicon solar cell and light-trapping filter. The result shows a significant improvement in current generation for thin-film silicon solar cells under typical operating conditions.

Efficient quantum microwave-to-optical conversion using electro-optic nanophotonic coupled resonators

NASA Astrophysics Data System (ADS)

Soltani, Mohammad; Zhang, Mian; Ryan, Colm; Ribeill, Guilhem J.; Wang, Cheng; Loncar, Marko

2017-10-01

We propose a low-noise, triply resonant, electro-optic (EO) scheme for quantum microwave-to-optical conversion based on coupled nanophotonics resonators integrated with a superconducting qubit. Our optical system features a split resonance—a doublet—with a tunable frequency splitting that matches the microwave resonance frequency of the superconducting qubit. This is in contrast to conventional approaches, where large optical resonators with free-spectral range comparable to the qubit microwave frequency are used. In our system, EO mixing between the optical pump coupled into the low-frequency doublet mode and a resonance microwave photon results in an up-converted optical photon on resonance with high-frequency doublet mode. Importantly, the down-conversion process, which is the source of noise, is suppressed in our scheme as the coupled-resonator system does not support modes at that frequency. Our device has at least an order of magnitude smaller footprint than conventional devices, resulting in large overlap between optical and microwave fields and a large photon conversion rate (g /2 π ) in the range of ˜5 -15 kHz. Owing to a large g factor and doubly resonant nature of our device, microwave-to-optical frequency conversion can be achieved with optical pump powers in the range of tens of microwatts, even with moderate values for optical Q (˜106 ) and microwave Q (˜104 ). The performance metrics of our device, with substantial improvement over the previous EO-based approaches, promise a scalable quantum microwave-to-optical conversion and networking of superconducting processors via optical fiber communication.

All-optical conversion scheme from binary to its MTN form with the help of nonlinear material based tree-net architecture

NASA Astrophysics Data System (ADS)

Maiti, Anup Kumar; Nath Roy, Jitendra; Mukhopadhyay, Sourangshu

2007-08-01

In the field of optical computing and parallel information processing, several number systems have been used for different arithmetic and algebraic operations. Therefore an efficient conversion scheme from one number system to another is very important. Modified trinary number (MTN) has already taken a significant role towards carry and borrow free arithmetic operations. In this communication, we propose a tree-net architecture based all optical conversion scheme from binary number to its MTN form. Optical switch using nonlinear material (NLM) plays an important role.

High efficiency solar cells combining a perovskite and a silicon heterojunction solar cells via an optical splitting system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uzu, Hisashi, E-mail: Hisashi.Uzu@kaneka.co.jp, E-mail: npark@skku.edu; Ichikawa, Mitsuru; Hino, Masashi

2015-01-05

We have applied an optical splitting system in order to achieve very high conversion efficiency for a full spectrum multi-junction solar cell. This system consists of multiple solar cells with different band gap optically coupled via an “optical splitter.” An optical splitter is a multi-layered beam splitter with very high reflection in the shorter-wave-length range and very high transmission in the longer-wave-length range. By splitting the incident solar spectrum and distributing it to each solar cell, the solar energy can be managed more efficiently. We have fabricated optical splitters and used them with a wide-gap amorphous silicon (a-Si) solar cellmore » or a CH{sub 3}NH{sub 3}PbI{sub 3} perovskite solar cell as top cells, combined with mono-crystalline silicon heterojunction (HJ) solar cells as bottom cells. We have achieved with a 550 nm cutoff splitter an active area conversion efficiency of over 25% using a-Si and HJ solar cells and 28% using perovskite and HJ solar cells.« less

Optical frequency up-conversion by supercontinuum-free widely-tunable fiber-optic Cherenkov radiation

PubMed Central

Tu, Haohua; Boppart, Stephen A.

2010-01-01

Spectrally-isolated narrowband Cherenkov radiation from commercial nonlinear photonic crystal fibers is demonstrated as an ultrafast optical source with a visible tuning range of 485–690 nm, which complementarily extends the near-infrared tuning range of 690–1020 nm from the corresponding femtosecond Ti:sapphire pump laser. Pump-to-signal conversion efficiency routinely surpasses 10%, enabling multimilliwatt visible output across the entire tuning range. Appropriate selection of fiber parameters and pumping conditions efficiently suppresses the supercontinuum generation typically associated with Cherenkov radiation. PMID:19506636

Magneto-optical mode conversion in a hybrid glass waveguide made by sol-gel and ion-exchange techniques

NASA Astrophysics Data System (ADS)

Royer, François; Amata, Hadi; Parsy, François; Jamon, Damien; Ghibaudo, Elise; Broquin, Jean-Emmanuel; Neveu, Sophie

2012-01-01

The integration of magneto-optical materials with classical technologies being still a difficult problem, this study explores the possibility to realize a mode converter based on a hybrid structure. A composite magneto-optical layer made of a silica/zirconia matrix doped by magnetic nanoparticles is coated on the top face of ion-exchanged glass waveguides. Optical characterizations that have been carried out demonstrated the efficiency of these hybrid structures in terms of lateral confinement. Furthermore, TE to TM mode conversion has been observed when a longitudinal magnetic field is applied to the device. The amount of this conversion is analysed taking into account the magneto-optical confinement and the modal birefringence of the structure.

Reconstructing a plasmonic metasurface for a broadband high-efficiency optical vortex in the visible frequency.

PubMed

Lu, Bing-Rui; Deng, Jianan; Li, Qi; Zhang, Sichao; Zhou, Jing; Zhou, Lei; Chen, Yifang

2018-06-14

Metasurfaces consisting of a two-dimensional metallic nano-antenna array are capable of transferring a Gaussian beam into an optical vortex with a helical phase front and a phase singularity by manipulating the polarization/phase status of light. This miniaturizes a laboratory scaled optical system into a wafer scale component, opening up a new area for broad applications in optics. However, the low conversion efficiency to generate a vortex beam from circularly polarized light hinders further development. This paper reports our recent success in improving the efficiency over a broad waveband at the visible frequency compared with the existing work. The choice of material, the geometry and the spatial organization of meta-atoms, and the fabrication fidelity are theoretically investigated by the Jones matrix method. The theoretical conversion efficiency over 40% in the visible wavelength range is worked out by systematic calculation using the finite difference time domain (FDTD) method. The fabricated metasurface based on the parameters by theoretical optimization demonstrates a high quality vortex in optical frequencies with a significantly enhanced efficiency of over 20% in a broad waveband.

Roadmap on optical energy conversion

NASA Astrophysics Data System (ADS)

Boriskina, Svetlana V.; Green, Martin A.; Catchpole, Kylie; Yablonovitch, Eli; Beard, Matthew C.; Okada, Yoshitaka; Lany, Stephan; Gershon, Talia; Zakutayev, Andriy; Tahersima, Mohammad H.; Sorger, Volker J.; Naughton, Michael J.; Kempa, Krzysztof; Dagenais, Mario; Yao, Yuan; Xu, Lu; Sheng, Xing; Bronstein, Noah D.; Rogers, John A.; Alivisatos, A. Paul; Nuzzo, Ralph G.; Gordon, Jeffrey M.; Wu, Di M.; Wisser, Michael D.; Salleo, Alberto; Dionne, Jennifer; Bermel, Peter; Greffet, Jean-Jacques; Celanovic, Ivan; Soljacic, Marin; Manor, Assaf; Rotschild, Carmel; Raman, Aaswath; Zhu, Linxiao; Fan, Shanhui; Chen, Gang

2016-07-01

For decades, progress in the field of optical (including solar) energy conversion was dominated by advances in the conventional concentrating optics and materials design. In recent years, however, conceptual and technological breakthroughs in the fields of nanophotonics and plasmonics combined with a better understanding of the thermodynamics of the photon energy-conversion processes reshaped the landscape of energy-conversion schemes and devices. Nanostructured devices and materials that make use of size quantization effects to manipulate photon density of states offer a way to overcome the conventional light absorption limits. Novel optical spectrum splitting and photon-recycling schemes reduce the entropy production in the optical energy-conversion platforms and boost their efficiencies. Optical design concepts are rapidly expanding into the infrared energy band, offering new approaches to harvest waste heat, to reduce the thermal emission losses, and to achieve noncontact radiative cooling of solar cells as well as of optical and electronic circuitries. Light-matter interaction enabled by nanophotonics and plasmonics underlie the performance of the third- and fourth-generation energy-conversion devices, including up- and down-conversion of photon energy, near-field radiative energy transfer, and hot electron generation and harvesting. Finally, the increased market penetration of alternative solar energy-conversion technologies amplifies the role of cost-driven and environmental considerations. This roadmap on optical energy conversion provides a snapshot of the state of the art in optical energy conversion, remaining challenges, and most promising approaches to address these challenges. Leading experts authored 19 focused short sections of the roadmap where they share their vision on a specific aspect of this burgeoning research field. The roadmap opens up with a tutorial section, which introduces major concepts and terminology. It is our hope that the roadmap will serve as an important resource for the scientific community, new generations of researchers, funding agencies, industry experts, and investors.

Diffractive optical elements for transformation of modes in lasers

DOEpatents

Sridharan, Arun K.; Pax, Paul H.; Heebner, John E.; Drachenberg, Derrek R.; Armstrong, James P.; Dawson, Jay W.

2015-09-01

Spatial mode conversion modules are described, with the capability of efficiently transforming a given optical beam profile, at one plane in space into another well-defined optical beam profile at a different plane in space, whose detailed spatial features and symmetry properties can, in general, differ significantly. The modules are comprised of passive, high-efficiency, low-loss diffractive optical elements, combined with Fourier transform optics. Design rules are described that employ phase retrieval techniques and associated algorithms to determine the necessary profiles of the diffractive optical components. System augmentations are described that utilize real-time adaptive optical techniques for enhanced performance as well as power scaling.

Diffractive optical elements for transformation of modes in lasers

DOEpatents

Sridharan, Arun K; Pax, Paul H; Heebner, John E; Drachenberg, Derrek R.; Armstrong, James P.; Dawson, Jay W.

2016-06-21

Spatial mode conversion modules are described, with the capability of efficiently transforming a given optical beam profile, at one plane in space into another well-defined optical beam profile at a different plane in space, whose detailed spatial features and symmetry properties can, in general, differ significantly. The modules are comprised of passive, high-efficiency, low-loss diffractive optical elements, combined with Fourier transform optics. Design rules are described that employ phase retrieval techniques and associated algorithms to determine the necessary profiles of the diffractive optical components. System augmentations are described that utilize real-time adaptive optical techniques for enhanced performance as well as power scaling.

Relaxed damage threshold intensity conditions and nonlinear increase in the conversion efficiency of an optical parametric oscillator using a bi-directional pump geometry.

PubMed

Norris, G; McConnell, G

2010-03-01

A novel bi-directional pump geometry that nonlinearly increases the nonlinear optical conversion efficiency of a synchronously pumped optical parametric oscillator (OPO) is reported. This bi-directional pumping method synchronizes the circulating signal pulse with two counter-propagating pump pulses within a linear OPO resonator. Through this pump scheme, an increase in nonlinear optical conversion efficiency of 22% was achieved at the signal wavelength, corresponding to a 95% overall increase in average power. Given an almost unchanged measured pulse duration of 260 fs under optimal performance conditions, this related to a signal wavelength peak power output of 18.8 kW, compared with 10 kW using the traditional single-pass geometry. In this study, a total effective peak intensity pump-field of 7.11 GW/cm(2) (corresponding to 3.55 GW/cm(2) from each pump beam) was applied to a 3 mm long periodically poled lithium niobate crystal, which had a damage threshold intensity of 4 GW/cm(2), without impairing crystal integrity. We therefore prove the application of this novel pump geometry provides opportunities for power-scaling of synchronously pumped OPO systems together with enhanced nonlinear conversion efficiency through relaxed damage threshold intensity conditions.

High-power Broadband Organic THz Generator

PubMed Central

Jeong, Jae-Hyeok; Kang, Bong-Joo; Kim, Ji-Soo; Jazbinsek, Mojca; Lee, Seung-Heon; Lee, Seung-Chul; Baek, In-Hyung; Yun, Hoseop; Kim, Jongtaek; Lee, Yoon Sup; Lee, Jae-Hyeok; Kim, Jae-Ho; Rotermund, Fabian; Kwon, O-Pil

2013-01-01

The high-power broadband terahertz (THz) generator is an essential tool for a wide range of THz applications. Here, we present a novel highly efficient electro-optic quinolinium single crystal for THz wave generation. For obtaining intense and broadband THz waves by optical-to-THz frequency conversion, a quinolinium crystal was developed to fulfill all the requirements, which are in general extremely difficult to maintain simultaneously in a single medium, such as a large macroscopic electro-optic response and excellent crystal characteristics including a large crystal size with desired facets, good environmental stability, high optical quality, wide transparency range, and controllable crystal thickness. Compared to the benchmark inorganic and organic crystals, the new quinolinium crystal possesses excellent crystal properties and THz generation characteristics with broader THz spectral coverage and higher THz conversion efficiency at the technologically important pump wavelength of 800 nm. Therefore, the quinolinium crystal offers great potential for efficient and gap-free broadband THz wave generation. PMID:24220234

High-power broadband organic THz generator.

PubMed

Jeong, Jae-Hyeok; Kang, Bong-Joo; Kim, Ji-Soo; Jazbinsek, Mojca; Lee, Seung-Heon; Lee, Seung-Chul; Baek, In-Hyung; Yun, Hoseop; Kim, Jongtaek; Lee, Yoon Sup; Lee, Jae-Hyeok; Kim, Jae-Ho; Rotermund, Fabian; Kwon, O-Pil

2013-11-13

The high-power broadband terahertz (THz) generator is an essential tool for a wide range of THz applications. Here, we present a novel highly efficient electro-optic quinolinium single crystal for THz wave generation. For obtaining intense and broadband THz waves by optical-to-THz frequency conversion, a quinolinium crystal was developed to fulfill all the requirements, which are in general extremely difficult to maintain simultaneously in a single medium, such as a large macroscopic electro-optic response and excellent crystal characteristics including a large crystal size with desired facets, good environmental stability, high optical quality, wide transparency range, and controllable crystal thickness. Compared to the benchmark inorganic and organic crystals, the new quinolinium crystal possesses excellent crystal properties and THz generation characteristics with broader THz spectral coverage and higher THz conversion efficiency at the technologically important pump wavelength of 800 nm. Therefore, the quinolinium crystal offers great potential for efficient and gap-free broadband THz wave generation.

High energy efficient solid state laser sources

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1988-01-01

Recent progress in the development of highly efficient coherent optical sources is reviewed. This work focusses on nonlinear frequency conversion of the highly coherent output of the Non-Planar Ring Laser Oscillators developed earlier in the program, and includes high efficiency second harmonic generation and the operation of optical parametric oscillators for wavelength diversity and tunability.

Characterization of ErAs:GaAs and LuAs:GaAs Superlattice Structures for Continuous-Wave Terahertz Wave Generation through Plasmonic Photomixing

NASA Astrophysics Data System (ADS)

Yang, Shang-Hua; Salas, Rodolfo; Krivoy, Erica M.; Nair, Hari P.; Bank, Seth R.; Jarrahi, Mona

2016-07-01

We investigate the impact of ErAs:GaAs and LuAs:GaAs superlattice structures with different LuAs/ErAs nanoparticle depositions and superlattice geometries on terahertz radiation properties of plasmonic photomixers operating at a 780-nm optical wavelength. Our analysis indicates the crucial impact of carrier drift velocity and carrier lifetime on the performance of plasmonic photomixers. While higher carrier drift velocities enable higher optical-to-terahertz conversion efficiencies by offering higher quantum efficiencies, shorter carrier lifetimes allow achieving higher optical-to-terahertz conversion efficiencies by mitigating the negative impact of destructive terahertz radiation from slow photocarriers and preventing the carrier screening effect.

Optical management for efficiency enhancement in hybrid organic-inorganic lead halide perovskite solar cells

PubMed Central

Zhang, Hui; Toudert, Johann

2018-01-01

Abstract In a few years only, solar cells using hybrid organic–inorganic lead halide perovskites as optical absorber have reached record photovoltaic energy conversion efficiencies above 20%. To reach and overcome such values, it is required to tailor both the electrical and optical properties of the device. For a given efficient device, optical optimization overtakes electrical one. Here, we provide a synthetic review of recent works reporting or proposing so-called optical management approaches for improving the efficiency of perovskite solar cells, including the use of anti-reflection coatings at the front substrate surface, the design of optical cavities integrated within the device, the incorporation of plasmonic or dielectric nanostructures into the different layers of the device and the structuration of its internal interfaces. We finally give as outlooks some insights into the less-explored management of the perovskite fluorescence and its potential for enhancing the cell efficiency. PMID:29868146

Optically-gated Non-latched High Gain Power Device

DTIC Science & Technology

2008-11-21

parameters such as power conversion efficiency, dv/dt and di/dt stress on PSD and electromagnetic noise emission spectrum, which depend directly on the...4. EXPERIMENTAL STUDIES ON OTPT AND OPTICAL INTENSITY MODULATION OF OTPT PARAMETERS 33 4.1 Optical source, driver, and fiber details 33 4.2...off dynamics characterizations 36 4.5. Optical intensity modulation of OTPT parameters 37 5. EXPERIMENTAL STUDIES ON HYBRID OTPT-PSD AND OPTICAL

Roadmap on optical energy conversion

DOE PAGES

Boriskina, Svetlana V.; Green, Martin A.; Catchpole, Kylie; ...

2016-06-24

For decades, progress in the field of optical (including solar) energy conversion was dominated by advances in the conventional concentrating optics and materials design. In recent years, however, conceptual and technological breakthroughs in the fields of nanophotonics and plasmonics combined with a better understanding of the thermodynamics of the photon energy-conversion processes reshaped the landscape of energy-conversion schemes and devices. Nanostructured devices and materials that make use of size quantization effects to manipulate photon density of states offer a way to overcome the conventional light absorption limits. Novel optical spectrum splitting and photon-recycling schemes reduce the entropy production in themore » optical energy-conversion platforms and boost their efficiencies. Optical design concepts are rapidly expanding into the infrared energy band, offering new approaches to harvest waste heat, to reduce the thermal emission losses, and to achieve noncontact radiative cooling of solar cells as well as of optical and electronic circuitries. Light-matter interaction enabled by nanophotonics and plasmonics underlie the performance of the third- and fourth-generation energy-conversion devices, including up- and down-conversion of photon energy, near-field radiative energy transfer, and hot electron generation and harvesting. Finally, the increased market penetration of alternative solar energy-conversion technologies amplifies the role of cost-driven and environmental considerations. This roadmap on optical energy conversion provides a snapshot of the state of the art in optical energy conversion, remaining challenges, and most promising approaches to address these challenges. Leading experts authored 19 focused short sections of the roadmap where they share their vision on a specific aspect of this burgeoning research field. The roadmap opens up with a tutorial section, which introduces major concepts and terminology. As a result, it is our hope that the roadmap will serve as an important resource for the scientific community, new generations of researchers, funding agencies, industry experts, and investors.« less

Hollow optical fiber induced solar cells with optical energy storage and conversion.

PubMed

Ding, Jie; Zhao, Yuanyuan; Duan, Jialong; Duan, Yanyan; Tang, Qunwei

2017-11-09

Hollow optical fiber induced dye-sensitized solar cells are made by twisting Ti wire/N719-TiO 2 nanotube photoanodes and Ti wire/Pt (CoSe, Pt 3 Ni) counter electrodes, yielding a maximized efficiency of 0.7% and good stability. Arising from optical energy storage ability, the solar cells can generate electricity without laser illumination.

High energy efficient solid state laser sources

NASA Technical Reports Server (NTRS)

Byer, Robert L.

1989-01-01

Recent progress in the development of highly efficient coherent optical sources was reviewed. This work has focused on nonlinear frequency conversion of the highly coherent output of the non-planar ring laser oscillators developed earlier in the program, and includes high efficiency second harmonic generation and the operation of optical parametric oscillators for wavelength diversity and tunability.

Studying the energy dependence of intrinsic conversion efficiency of single crystal scintillators under X-ray excitation

NASA Astrophysics Data System (ADS)

Kalyvas, N.; Valais, I.; David, S.; Michail, Ch.; Fountos, G.; Liaparinos, P.; Kandarakis, I.

2014-05-01

Single crystal scintilators are used in various radiation detectors applications. The efficiency of the crystal can be determined by the Detector Optical Gain (DOG) defined as the ratio of the emitted optical photon flux over the incident radiation photons flux. A parameter affecting DOG is the intrinsic conversion efficiency ( n C ) giving the percentage of the X-ray photon power converted to optical photon power. n C is considered a constant value for X-ray energies in the order of keV although a non-proportional behavior has been reported. In this work an analytical model, has been utilized to single crystals scintillators GSO:Ce, LSO:Ce and LYSO:Ce to examine whether the intrinsic conversion efficiency shows non proportional behavior under X-ray excitation. DOG was theoretically calculated as a function of the incident X-ray spectrum, the X-ray absorption efficiency, the energy of the produced optical photons and the light transmission efficiency. The theoretical DOG values were compared with experimental data obtained by irradiating the crystals with X-rays at tube voltages from 50 to 140 kV and by measuring the light energy flux emitted from the irradiated screen. An initial value for n C (calculated from literature data) was assumed for the X-ray tube voltage of 50 kV. For higher X-ray tube voltages the optical photon propagation phenomena was assumed constant and any deviations between experimental and theoretical data were associated with changes in the intrinsic conversion efficiency. The experimental errors were below 7% for each experimental setup. The behavior of n C values for LSO:Ce and LYSO:Ce were found very similar, i.e., ranging with values from 0.089 at 50 kV to 0.015 at 140 kV, while for GSO:Ce, n C demonstrated a peak at 80 kV.

Crystal growth of organics for nonlinear optical applications

NASA Technical Reports Server (NTRS)

Singh, N. B.; Mazelsky, R.

1993-01-01

The crystal growth and characterization of organic and inorganic nonlinear optical materials were extensively studied. For example, inorganic crystals such as thallium arsenic selenide were studied in our laboratory for several years and crystals in sizes over 2.5 cm in diameter are available. Organic crystals are suitable for the ultraviolet and near infrared region, but are relatively less developed than their inorganic counterparts. Very high values of the second harmonic conversion efficiency and the electro-optic coefficient were reported for organic compounds. Single crystals of a binary organic alloy based on m.NA and CNA were grown and higher second harmonic conversion efficiency than the values reported for m.NA were observed.

High power diode laser Master Oscillator-Power Amplifier (MOPA)

NASA Technical Reports Server (NTRS)

Andrews, John R.; Mouroulis, P.; Wicks, G.

1994-01-01

High power multiple quantum well AlGaAs diode laser master oscillator - power amplifier (MOPA) systems were examined both experimentally and theoretically. For two pass operation, it was found that powers in excess of 0.3 W per 100 micrometers of facet length were achievable while maintaining diffraction-limited beam quality. Internal electrical-to-optical conversion efficiencies as high as 25 percent were observed at an internal amplifier gain of 9 dB. Theoretical modeling of multiple quantum well amplifiers was done using appropriate rate equations and a heuristic model of the carrier density dependent gain. The model gave a qualitative agreement with the experimental results. In addition, the model allowed exploration of a wider design space for the amplifiers. The model predicted that internal electrical-to-optical conversion efficiencies in excess of 50 percent should be achievable with careful system design. The model predicted that no global optimum design exists, but gain, efficiency, and optical confinement (coupling efficiency) can be mutually adjusted to meet a specific system requirement. A three quantum well, low optical confinement amplifier was fabricated using molecular beam epitaxial growth. Coherent beam combining of two high power amplifiers injected from a common master oscillator was also examined. Coherent beam combining with an efficiency of 93 percent resulted in a single beam having diffraction-limited characteristics. This beam combining efficiency is a world record result for such a system. Interferometric observations of the output of the amplifier indicated that spatial mode matching was a significant factor in the less than perfect beam combining. Finally, the system issues of arrays of amplifiers in a coherent beam combining system were investigated. Based upon experimentally observed parameters coherent beam combining could result in a megawatt-scale coherent beam with a 10 percent electrical-to-optical conversion efficiency.

Multi-Watt femtosecond optical parametric master oscillator power amplifier at 43 MHz.

PubMed

Mörz, Florian; Steinle, Tobias; Steinmann, Andy; Giessen, Harald

2015-09-07

We present a high repetition rate mid-infrared optical parametric master oscillator power amplifier (MOPA) scheme, which is tunable from 1370 to 4120nm. Up to 4.3W average output power are generated at 1370nm, corresponding to a photon conversion efficiency of 78%. Bandwidths of 6 to 12nm with pulse durations between 250 and 400fs have been measured. Strong conversion saturation over the whole signal range is observed, resulting in excellent power stability. The system consists of a fiber-feedback optical parametric oscillator that seeds an optical parametric power amplifier. Both systems are pumped by the same Yb:KGW femtosecond oscillator.

Demonstration of spatial-light-modulation-based four-wave mixing in cold atoms

NASA Astrophysics Data System (ADS)

Juo, Jz-Yuan; Lin, Jia-Kang; Cheng, Chin-Yao; Liu, Zi-Yu; Yu, Ite A.; Chen, Yong-Fan

2018-05-01

Long-distance quantum optical communications usually require efficient wave-mixing processes to convert the wavelengths of single photons. Many quantum applications based on electromagnetically induced transparency (EIT) have been proposed and demonstrated at the single-photon level, such as quantum memories, all-optical transistors, and cross-phase modulations. However, EIT-based four-wave mixing (FWM) in a resonant double-Λ configuration has a maximum conversion efficiency (CE) of 25% because of absorptive loss due to spontaneous emission. An improved scheme using spatially modulated intensities of two control fields has been theoretically proposed to overcome this conversion limit. In this study, we first demonstrate wavelength conversion from 780 to 795 nm with a 43% CE by using this scheme at an optical density (OD) of 19 in cold 87Rb atoms. According to the theoretical model, the CE in the proposed scheme can further increase to 96% at an OD of 240 under ideal conditions, thereby attaining an identical CE to that of the previous nonresonant double-Λ scheme at half the OD. This spatial-light-modulation-based FWM scheme can achieve a near-unity CE, thus providing an easy method of implementing an efficient quantum wavelength converter for all-optical quantum information processing.

Highly efficient continuous-wave Nd:YAG ceramic lasers at 946 nm

NASA Astrophysics Data System (ADS)

Zhu, H. Y.; Xu, C. W.; Zhang, J.; Tang, D. Y.; Luo, D. W.; Duan, Y. M.

2013-07-01

Highly efficient CW operation of diode-end-pumped Nd:YAG ceramic lasers at 946 nm is experimentally demonstrated. When a 5 mm long in-house fabricated Nd:YAG ceramic was used as the gain medium, a maximum output power of 10.5 W was obtained under an incident pump power of 35 W, corresponding to an optical conversion efficiency of 30%, while, when a 3 mm long ceramic sample was used, a maximum output power of 8.7 W was generated with a slope efficiency of 65% with respect to the absorbed pump power. Both the optical conversion efficiency and slope efficiency are the highest results reported so far for the diode-pumped 946 nm lasers.

Efficiency limits of laser power converters for optical power transfer applications

NASA Astrophysics Data System (ADS)

Mukherjee, J.; Jarvis, S.; Perren, M.; Sweeney, S. J.

2013-07-01

We have developed III-V-based high-efficiency laser power converters (LPCs), optimized specifically for converting monochromatic laser radiation at the eye-safe wavelength of 1.55 µm into electrical power. The applications of these photovoltaic cells include high-efficiency space-based and terrestrial laser power transfer and subsequent conversion to electrical power. In addition, these cells also find use in fibre-optic power delivery, remote powering of subcutaneous equipment and several other optical power delivery applications. The LPC design is based on lattice-matched InGaAsP/InP and incorporates elements for photon-recycling and contact design for efficient carrier extraction. Here we compare results from electro-optical design simulations with experimental results from prototype devices studied both in the lab and in field tests. We analyse wavelength and temperature dependence of the LPC characteristics. An experimental conversion efficiency of 44.6% [±1%] is obtained from the prototype devices under monochromatic illumination at 1.55 µm (illumination power density of 1 kW m-2) at room temperature. Further design optimization of our LPC is expected to scale the efficiency beyond 50% at 1 kW m-2.

Ridge Waveguide Structures in Magnesium-Doped Lithium Niobate

NASA Technical Reports Server (NTRS)

Himmer, Phillip; Battle, Philip; Suckow, William; Switzer, Greg

2011-01-01

This work proposes to establish the feasibility of fabricating isolated ridge waveguides in 5% MgO:LN. Ridge waveguides in MgO:LN will significantly improve power handling and conversion efficiency, increase photonic component integration, and be well suited to spacebased applications. The key innovation in this effort is to combine recently available large, high-photorefractive-damage-threshold, z-cut 5% MgO:LN with novel ridge fabrication techniques to achieve high-optical power, low-cost, high-volume manufacturing of frequency conversion structures. The proposed ridge waveguide structure should maintain the characteristics of the periodically poled bulk substrate, allowing for the efficient frequency conversion typical of waveguides and the high optical damage threshold and long lifetimes typical of the 5% doped bulk substrate. The low cost and large area of 5% MgO:LN wafers, and the improved performance of the proposed ridge waveguide structure, will enhance existing measurement capabilities as well as reduce the resources required to achieve high-performance specifications. The purpose of the ridge waveguides in MgO:LN is to provide platform technology that will improve optical power handling and conversion efficiency compared to existing waveguide technology. The proposed ridge waveguide is produced using standard microfabrication techniques. The approach is enabled by recent advances in inductively coupled plasma etchers and chemical mechanical planarization techniques. In conjunction with wafer bonding, this fabrication methodology can be used to create arbitrarily shaped waveguides allowing complex optical circuits to be engineered in nonlinear optical materials such as magnesium doped lithium niobate. Researchers here have identified NLO (nonlinear optical) ridge waveguide structures as having suitable value to be the leading frequency conversion structures. Its value is based on having the low-cost fabrication necessary to satisfy the challenging pricing requirements as well as achieve the power handling and other specifications in a suitably compact package.

MO detector (MOD): a dual-function optical modulator-detector for on-chip communication

NASA Astrophysics Data System (ADS)

Sun, Shuai; Zhang, Ruoyu; Peng, Jiaxin; Narayana, Vikram K.; Dalir, Hamed; El-Ghazawi, Tarek; Sorger, Volker J.

2018-04-01

Physical challenges at the device and interconnect level limit both network and computing energy efficiency. While photonics is being considered to address interconnect bottlenecks, optical routing is still limited by electronic circuitry, requiring substantial overhead for optical-electrical-optical conversion. Here we show a novel design of an integrated broadband photonic-plasmonic hybrid device termed MODetector featuring dual light modulation and detection function to act as an optical transceiver in the photonic network-on-chip. With over 10 dB extinction ratio and 0.8 dB insertion loss at the modulation state, this MODetector provides 0.7 W/A responsivity in the detection state with 36 ps response time. This multi-functional device: (i) eliminates OEO conversion, (ii) reduces optical losses from photodetectors when not needed, and (iii) enables cognitive routing strategies for network-on-chips.

Optical apparatus for conversion of whispering-gallery modes into a free space gaussian like beam

DOEpatents

Stallard, Barry W.; Makowski, Michael A.; Byers, Jack A.

1992-01-01

An optical converter for efficient conversion of millimeter wavelength whispering-gallery gyrotron output into a linearly polarized, free-space Gaussian-like beam. The converter uses a mode-converting taper and three mirror optics. The first mirror has an azimuthal tilt to eliminate the k.sub..phi. component of the propagation vector of the gyrotron output beam. The second mirror has a twist reflector to linearly polarize the beam. The third mirror has a constant phase surface so the converter output is in phase.

Metallic metasurfaces for high efficient polarization conversion control in transmission mode.

PubMed

Li, Tong; Hu, Xiaobin; Chen, Huamin; Zhao, Chen; Xu, Yun; Wei, Xin; Song, Guofeng

2017-10-02

A high efficient broadband polarization converter is an important component in integrated miniaturized optical systems, but its performances is often restricted by the material structures, metallic metasurfaces for polarization control in transmission mode never achieved efficiency above 0.5. Herein, we theoretically demonstrate that metallic metasurfaces constructed by thick cross-shaped particles can realize a high efficient polarization transformation over a broadband. We investigated the resonant properties of designed matesurfaces and found that the interaction between double FP cavity resonances and double bulk magnetic resonances is the main reason to generate a high transmissivity over a broadband. In addition, through using four resonances effect and tuning the anisotropic optical response, we realized a high efficient (> 0.85) quarter-wave plate at the wavelength range from 1175nm to 1310nm and a high efficient (> 0.9) half-wave plate at the wavelength range from 1130nm to 1230nm. The proposed polarization converters may have many potential applications in integrated polarization conversion devices and optical data storage systems.

Controllable optical modulation of blue/green up-conversion fluorescence from Tm3+ (Er3+) single-doped glass ceramics upon two-step excitation of two-wavelengths

PubMed Central

Chen, Zhi; Kang, Shiliang; Zhang, Hang; Wang, Ting; Lv, Shichao; Chen, Qiuqun; Dong, Guoping; Qiu, Jianrong

2017-01-01

Optical modulation is a crucial operation in photonics for network data processing with the aim to overcome information bottleneck in terms of speed, energy consumption, dispersion and cross-talking from conventional electronic interconnection approach. However, due to the weak interactions between photons, a facile physical approach is required to efficiently manipulate photon-photon interactions. Herein, we demonstrate that transparent glass ceramics containing LaF3: Tm3+ (Er3+) nanocrystals can enable fast-slow optical modulation of blue/green up-conversion fluorescence upon two-step excitation of two-wavelengths at telecom windows (0.8–1.8 μm). We show an optical modulation of more than 1500% (800%) of the green (blue) up-conversion fluorescence intensity, and fast response of 280 μs (367 μs) as well as slow response of 5.82 ms (618 μs) in the green (blue) up-conversion fluorescence signal, respectively. The success of manipulating laser at telecom windows for fast-slow optical modulation from rear-earth single-doped glass ceramics may find application in all-optical fiber telecommunication areas. PMID:28368041

High Photoelectric Conversion Efficiency of Metal Phthalocyanine/Fullerene Heterojunction Photovoltaic Device

PubMed Central

Lin, Chi-Feng; Zhang, Mi; Liu, Shun-Wei; Chiu, Tien-Lung; Lee, Jiun-Haw

2011-01-01

This paper introduces the fundamental physical characteristics of organic photovoltaic (OPV) devices. Photoelectric conversion efficiency is crucial to the evaluation of quality in OPV devices, and enhancing efficiency has been spurring on researchers to seek alternatives to this problem. In this paper, we focus on organic photovoltaic (OPV) devices and review several approaches to enhance the energy conversion efficiency of small molecular heterojunction OPV devices based on an optimal metal-phthalocyanine/fullerene (C60) planar heterojunction thin film structure. For the sake of discussion, these mechanisms have been divided into electrical and optical sections: (1) Electrical: Modification on electrodes or active regions to benefit carrier injection, charge transport and exciton dissociation; (2) Optical: Optional architectures or infilling to promote photon confinement and enhance absorption. PMID:21339999

Third harmonic frequency generation by type-I critically phase-matched LiB3O5 crystal by means of optically active quartz crystal.

PubMed

Gapontsev, Valentin P; Tyrtyshnyy, Valentin A; Vershinin, Oleg I; Davydov, Boris L; Oulianov, Dmitri A

2013-02-11

We present a method of third harmonic generation at 355 nm by frequency mixing of fundamental and second harmonic radiation of an ytterbium nanosecond pulsed all-fiber laser in a type-I phase-matched LiB(3)O(5) (LBO) crystal where originally orthogonal polarization planes of the fundamental and second harmonic beams are aligned by an optically active quartz crystal. 8 W of ultraviolet light at 355 nm were achieved with 40% conversion efficiency from 1064 nm radiation. The conversion efficiency obtained in a type-I phase-matched LBO THG crystal was 1.6 times higher than the one achieved in a type-II LBO crystal at similar experimental conditions. In comparison to half-wave plates traditionally used for polarization alignment the optically active quartz crystal has much lower temperature dependence and requires simpler optical alignment.

High bandwidth on-chip capacitive tuning of microtoroid resonators

NASA Astrophysics Data System (ADS)

Baker, Christopher G.; Bekker, Christiaan; McAuslan, David L.; Sheridan, Eoin; Bowen, Warwick P.

2016-09-01

We report on the design, fabrication and characterization of silica microtoroid based cavity opto-electromechanical systems (COEMS). Electrodes patterned onto the microtoroid resonators allow for rapid capacitive tuning of the optical whispering gallery mode resonances while maintaining their ultrahigh quality factor, enabling applications such as efficient radio to optical frequency conversion, optical routing and switching applications.

The influence of thermal and free carrier dispersion effects on all-optical wavelength conversion in a silicon racetrack-shaped microring resonator

NASA Astrophysics Data System (ADS)

Wang, Zhaolu; Liu, Hongjun; Sun, Qibing; Huang, Nan; Li, Shaopeng; Han, Jing

2016-07-01

We experimentally demonstrate ultra-low pump power wavelength conversion based on four-wave mixing in a silicon racetrack-shaped microring resonator. When the pump and signal are located at the resonance wavelengths, wavelength conversion with a pump power of only 1 mW can be realized in this microring resonator because of the resonant enhancement of the device. However, saturation of the conversion efficiency occurs because of the shift of the resonance peak, which is caused by the change of the effective refractive index induced by a combination of thermal and free carrier dispersion effects, and it is demonstrated that the thermal effect is the leading-order factor for the change of the refractive index. The maximum conversion efficiency of  -21 dB is obtained when the pump power is less than 12 mW. This ultra-low-power on-chip wavelength convertor based on a silicon microring resonator can find important potential applications in highly integrated optical circuits for all-optical signal processing.

Unity-Efficiency Parametric Down-Conversion via Amplitude Amplification.

PubMed

Niu, Murphy Yuezhen; Sanders, Barry C; Wong, Franco N C; Shapiro, Jeffrey H

2017-03-24

We propose an optical scheme, employing optical parametric down-converters interlaced with nonlinear sign gates (NSGs), that completely converts an n-photon Fock-state pump to n signal-idler photon pairs when the down-converters' crystal lengths are chosen appropriately. The proof of this assertion relies on amplitude amplification, analogous to that employed in Grover search, applied to the full quantum dynamics of single-mode parametric down-conversion. When we require that all Grover iterations use the same crystal, and account for potential experimental limitations on crystal-length precision, our optimized conversion efficiencies reach unity for 1≤n≤5, after which they decrease monotonically for n values up to 50, which is the upper limit of our numerical dynamics evaluations. Nevertheless, our conversion efficiencies remain higher than those for a conventional (no NSGs) down-converter.

High efficiency light source using solid-state emitter and down-conversion material

DOEpatents

Narendran, Nadarajah; Gu, Yimin; Freyssinier, Jean Paul

2010-10-26

A light emitting apparatus includes a source of light for emitting light; a down conversion material receiving the emitted light, and converting the emitted light into transmitted light and backward transmitted light; and an optic device configured to receive the backward transmitted light and transfer the backward transmitted light outside of the optic device. The source of light is a semiconductor light emitting diode, a laser diode (LD), or a resonant cavity light emitting diode (RCLED). The down conversion material includes one of phosphor or other material for absorbing light in one spectral region and emitting light in another spectral region. The optic device, or lens, includes light transmissive material.

Complete energy conversion by autoresonant three-wave mixing in nonuniform media.

PubMed

Yaakobi, O; Caspani, L; Clerici, M; Vidal, F; Morandotti, R

2013-01-28

Resonant three-wave interactions appear in many fields of physics e.g. nonlinear optics, plasma physics, acoustics and hydrodynamics. A general theory of autoresonant three-wave mixing in a nonuniform media is derived analytically and demonstrated numerically. It is shown that due to the medium nonuniformity, a stable phase-locked evolution is automatically established. For a weak nonuniformity, the efficiency of the energy conversion between the interacting waves can reach almost 100%. One of the potential applications of our theory is the design of highly-efficient optical parametric amplifiers.

Microwave-to-Optical Conversion in WGM Resonators

NASA Technical Reports Server (NTRS)

Savchenkov, Anatoliy; Strekalov, Dmitry; Yu, Nan; Matsko, Andrey; Maleki, Lute

2008-01-01

Microwave-to-optical frequency converters based on whispering-gallery-mode (WGM) resonators have been proposed as mixers for the input ends of microwave receivers in which, downstream of the input ends, signals would be processed photonically. A frequency converter as proposed (see figure) would exploit the nonlinearity of the electromagnetic response of a WGM resonator made of LiNbO3 or another suitable ferroelectric material. Up-conversion would take place by three-wave mixing in the resonator. The WGM resonator would be de - signed and fabricated to obtain (1) resonance at both the microwave and the optical operating frequencies and (2) phase matching among the input and output microwave and optical signals as described in the immediately preceding article. Because the resonator would be all dielectric there would be no metal electrodes signal losses would be very low and, consequently, the resonance quality factors (Q values) of the microwave and optical fields would be very large. The long lifetimes associated with the large Q values would enable attainment of high efficiency of nonlinear interaction with low saturation power. It is anticipated that efficiency would be especially well enhanced by the combination of optical and microwave resonances in operation at input signal frequencies between 90 and 300 GHz.

Compact and efficient CW 473nm blue laser with LBO intracavity frequency doubling

NASA Astrophysics Data System (ADS)

Qi, Yan; Wang, Yu; Wang, Yanwei; Zhang, Jing; Yan, Boxia

2016-10-01

With diode end pumped Nd:YAG directly and LBO intracavity frequency doubling, a compact, high efficient continuous wave blue laser at 473nm is realized. When the incident pump power reach 6.2W, 630mW maximum output power of blue laser at 473nm is achieved with 15mm long LBO, the optical-to-optical conversion efficiency is as high as 10.2%.

Free electron lasers for transmission of energy in space

NASA Technical Reports Server (NTRS)

Segall, S. B.; Hiddleston, H. R.; Catella, G. C.

1981-01-01

A one-dimensional resonant-particle model of a free electron laser (FEL) is used to calculate laser gain and conversion efficiency of electron energy to photon energy. The optical beam profile for a resonant optical cavity is included in the model as an axial variation of laser intensity. The electron beam profile is matched to the optical beam profile and modeled as an axial variation of current density. Effective energy spread due to beam emittance is included. Accelerators appropriate for a space-based FEL oscillator are reviewed. Constraints on the concentric optical resonator and on systems required for space operation are described. An example is given of a space-based FEL that would produce 1.7 MW of average output power at 0.5 micrometer wavelength with over 50% conversion efficiency of electrical energy to laser energy. It would utilize a 10 m-long amplifier centered in a 200 m-long optical cavity. A 3-amp, 65 meV electrostatic accelerator would provide the electron beam and recover the beam after it passes through the amplifier. Three to five shuttle flights would be needed to place the laser in orbit.

Image-rotating, 4-mirror, ring optical parametric oscillator

DOEpatents

Smith, Arlee V.; Armstrong, Darrell J.

2004-08-10

A device for optical parametric amplification utilizing four mirrors oriented in a nonplanar configuration where the optical plane formed by two of the mirrors is orthogonal to the optical plane formed by the other two mirrors and with the ratio of lengths of the laser beam paths approximately constant regardless of the scale of the device. With a cavity length of less than approximately 110 mm, a conversion efficiency of greater than 45% can be achieved.

Photo-induced-heat localization on nanostructured metallic glasses

NASA Astrophysics Data System (ADS)

Uzun, Ceren; Kahler, Niloofar; Grave de Peralta, Luis; Kumar, Golden; Bernussi, Ayrton A.

2017-09-01

Materials with large photo-thermal energy conversion efficiency are essential for renewable energy applications. Photo-excitation is an effective approach to generate controlled and localized heat at relatively low excitation optical powers. However, lateral heat diffusion to the surrounding illuminated areas accompanied by low photo-thermal energy conversion efficiency remains a challenge for metallic surfaces. Surface nanoengineering has proven to be a successful approach to further absorption and heat generation. Here, we show that pronounced spatial heat localization and high temperatures can be achieved with arrays of amorphous metallic glass nanorods under infrared optical illumination. Thermography measurements revealed marked temperature contrast between illuminated and non-illuminated areas even under low optical power excitation conditions. This attribute allowed for generating legible photo-induced thermal patterns on textured metallic glass surfaces.

Multiscale Modeling of Plasmon-Enhanced Power Conversion Efficiency in Nanostructured Solar Cells.

PubMed

Meng, Lingyi; Yam, ChiYung; Zhang, Yu; Wang, Rulin; Chen, GuanHua

2015-11-05

The unique optical properties of nanometallic structures can be exploited to confine light at subwavelength scales. This excellent light trapping is critical to improve light absorption efficiency in nanoscale photovoltaic devices. Here, we apply a multiscale quantum mechanics/electromagnetics (QM/EM) method to model the current-voltage characteristics and optical properties of plasmonic nanowire-based solar cells. The QM/EM method features a combination of first-principles quantum mechanical treatment of the photoactive component and classical description of electromagnetic environment. The coupled optical-electrical QM/EM simulations demonstrate a dramatic enhancement for power conversion efficiency of nanowire solar cells due to the surface plasmon effect of nanometallic structures. The improvement is attributed to the enhanced scattering of light into the photoactive layer. We further investigate the optimal configuration of the nanostructured solar cell. Our QM/EM simulation result demonstrates that a further increase of internal quantum efficiency can be achieved by scattering light into the n-doped region of the device.

Enhanced optical-to-THz conversion efficiency of photoconductive antenna using dielectric nano-layer encapsulation

NASA Astrophysics Data System (ADS)

Gupta, Abhishek; Rana, Goutam; Bhattacharya, Arkabrata; Singh, Abhishek; Jain, Ravikumar; Bapat, Rudheer D.; Duttagupta, S. P.; Prabhu, S. S.

2018-05-01

Photoconductive antennas (PCAs) are among the most conventional devices used for emission as well as detection of terahertz (THz) radiation. However, due to their low optical-to-THz conversion efficiencies, applications of these devices in out-of-laboratory conditions are limited. In this paper, we report several factors of enhancement in THz emission efficiency from conventional PCAs by coating a nano-layer of dielectric (TiO2) on the active area between the electrodes of a semi-insulating GaAs-based device. Extensive experiments were done to show the effect of thicknesses of the TiO2 layer on the THz power enhancement with different applied optical power and bias voltages. Multiphysics simulations were performed to elucidate the underlying physics behind the enhancement of efficiency of the PCA. Additionally, this layer increases the robustness of the electrode gaps of the PCAs with high electrical insulation as well as protect it from external dust particles.

High-accurate optical vector analysis based on optical single-sideband modulation

NASA Astrophysics Data System (ADS)

Xue, Min; Pan, Shilong

2016-11-01

Most of the efforts devoted to the area of optical communications were on the improvement of the optical spectral efficiency. Varies innovative optical devices are thus developed to finely manipulate the optical spectrum. Knowing the spectral responses of these devices, including the magnitude, phase and polarization responses, is of great importance for their fabrication and application. To achieve high-resolution characterization, optical vector analyzers (OVAs) based on optical single-sideband (OSSB) modulation have been proposed and developed. Benefiting from the mature and highresolution microwave technologies, the OSSB-based OVA can potentially achieve a resolution of sub-Hz. However, the accuracy is restricted by the measurement errors induced by the unwanted first-order sideband and the high-order sidebands in the OSSB signal, since electrical-to-optical conversion and optical-to-electrical conversion are essentially required to achieve high-resolution frequency sweeping and extract the magnitude and phase information in the electrical domain. Recently, great efforts have been devoted to improve the accuracy of the OSSB-based OVA. In this paper, the influence of the unwanted-sideband induced measurement errors and techniques for implementing high-accurate OSSB-based OVAs are discussed.

Nonlinear Frequency Conversion in III-V Semiconductor Photonic Crystals

DTIC Science & Technology

2012-03-01

nanocavities, by localizing light into sub-cubic optical wavelength volumes with long photon storage times, can greatly enhance the efficiency of...dissertation shows how optical nanocavities, by localizing light into sub-cubic optical wavelength volumes with long photon storage times, can greatly...8.2.3 Lithographic localization of molecules to cavity region . . . . . 86 8.2.4 Low temperature spectroscopy of DNQDI . . . . . . . . . . . 89 8.2.5

Upconversion fiber-optic confocal microscopy under near-infrared pumping.

PubMed

Kim, Do-Hyun; Kang, Jin U; Ilev, Ilko K

2008-03-01

We present a simple upconversion fiber-optic confocal microscope design using a near-infrared laser for pumping of a rare-earth-doped glass powder. The nonlinear optical frequency conversion process is highly efficient with more than 2% upconversion fluorescence efficiency at a near-infrared pumping wavelength of 1.55 microm. The upconversion confocal design allows the use of conventional Si detectors and 1.55 microm near-infrared pump light. The lateral and axial resolutions of the system were equal to or better than 1.10 and 13.11 microm, respectively.

Design principles for single standing nanowire solar cells: going beyond the planar efficiency limits.

PubMed

Zeng, Yang; Ye, Qinghao; Shen, Wenzhong

2014-05-09

Semiconductor nanowires (NWs) have long been used in photovoltaic applications but restricted to approaching the fundamental efficiency limits of the planar devices with less material. However, recent researches on standing NWs have started to reveal their potential of surpassing these limits when their unique optical property is utilized in novel manners. Here, we present a theoretical guideline for maximizing the conversion efficiency of a single standing NW cell based on a detailed study of its optical absorption mechanism. Under normal incidence, a standing NW behaves as a dielectric resonator antenna, and its optical cross-section shows its maximum when the lowest hybrid mode (HE11δ) is excited along with the presence of a back-reflector. The promotion of the cell efficiency beyond the planar limits is attributed to two effects: the built-in concentration caused by the enlarged optical cross-section, and the shifting of the absorption front resulted from the excited mode profile. By choosing an optimal NW radius to support the HE11δ mode within the main absorption spectrum, we demonstrate a relative conversion-efficiency enhancement of 33% above the planar cell limit on the exemplary a-Si solar cells. This work has provided a new basis for designing and analyzing standing NW based solar cells.

Design principles for single standing nanowire solar cells: going beyond the planar efficiency limits

PubMed Central

Zeng, Yang; Ye, Qinghao; Shen, Wenzhong

2014-01-01

Semiconductor nanowires (NWs) have long been used in photovoltaic applications but restricted to approaching the fundamental efficiency limits of the planar devices with less material. However, recent researches on standing NWs have started to reveal their potential of surpassing these limits when their unique optical property is utilized in novel manners. Here, we present a theoretical guideline for maximizing the conversion efficiency of a single standing NW cell based on a detailed study of its optical absorption mechanism. Under normal incidence, a standing NW behaves as a dielectric resonator antenna, and its optical cross-section shows its maximum when the lowest hybrid mode (HE11δ) is excited along with the presence of a back-reflector. The promotion of the cell efficiency beyond the planar limits is attributed to two effects: the built-in concentration caused by the enlarged optical cross-section, and the shifting of the absorption front resulted from the excited mode profile. By choosing an optimal NW radius to support the HE11δ mode within the main absorption spectrum, we demonstrate a relative conversion-efficiency enhancement of 33% above the planar cell limit on the exemplary a-Si solar cells. This work has provided a new basis for designing and analyzing standing NW based solar cells. PMID:24810591

New Diamond Color Center for Quantum Communication

NASA Astrophysics Data System (ADS)

Huang, Ding; Rose, Brendon; Tyryshkin, Alexei; Sangtawesin, Sorawis; Srinivasan, Srikanth; Twitchen, Daniel; Markham, Matthew; Edmonds, Andrew; Gali, Adam; Stacey, Alastair; Wang, Wuyi; D'Haenens-Johansson, Ulrika; Zaitsev, Alexandre; Lyon, Stephen; de Leon, Nathalie

2017-04-01

Color centers in diamond are attractive for quantum communication applications because of their long electron spin coherence times and efficient optical transitions. Previous demonstrations of color centers as solid-state spin qubits were primarily focused on centers that exhibit either long coherence times or highly efficient optical interfaces. Recently, we developed a method to stabilize the neutral charge state of silicon-vacancy center in diamond (SiV0) with high conversion efficiency. We observe spin relaxation times exceeding 1 minute and spin coherence times of 1 ms for SiV0 centers. Additionally, the SiV0 center also has > 90 % of its emission into its zero-phonon line and a narrow inhomogeneous optical linewidth. The combination of a long spin coherence time and efficient optical interface make the SiV0 center a promising candidate for applications in long distance quantum communication.

Antenna-coupled photon emission from hexagonal boron nitride tunnel junctions.

PubMed

Parzefall, M; Bharadwaj, P; Jain, A; Taniguchi, T; Watanabe, K; Novotny, L

2015-12-01

The ultrafast conversion of electrical signals to optical signals at the nanoscale is of fundamental interest for data processing, telecommunication and optical interconnects. However, the modulation bandwidths of semiconductor light-emitting diodes are limited by the spontaneous recombination rate of electron-hole pairs, and the footprint of electrically driven ultrafast lasers is too large for practical on-chip integration. A metal-insulator-metal tunnel junction approaches the ultimate size limit of electronic devices and its operating speed is fundamentally limited only by the tunnelling time. Here, we study the conversion of electrons (localized in vertical gold-hexagonal boron nitride-gold tunnel junctions) to free-space photons, mediated by resonant slot antennas. Optical antennas efficiently bridge the size mismatch between nanoscale volumes and far-field radiation and strongly enhance the electron-photon conversion efficiency. We achieve polarized, directional and resonantly enhanced light emission from inelastic electron tunnelling and establish a novel platform for studying the interaction of electrons with strongly localized electromagnetic fields.

Time-reversed wave mixing in nonlinear optics

PubMed Central

Zheng, Yuanlin; Ren, Huaijin; Wan, Wenjie; Chen, Xianfeng

2013-01-01

Time-reversal symmetry is important to optics. Optical processes can run in a forward or backward direction through time when such symmetry is preserved. In linear optics, a time-reversed process of laser emission can enable total absorption of coherent light fields inside an optical cavity of loss by time-reversing the original gain medium. Nonlinearity, however, can often destroy such symmetry in nonlinear optics, making it difficult to study time-reversal symmetry with nonlinear optical wave mixings. Here we demonstrate time-reversed wave mixings for optical second harmonic generation (SHG) and optical parametric amplification (OPA) by exploring this well-known but underappreciated symmetry in nonlinear optics. This allows us to observe the annihilation of coherent beams. Our study offers new avenues for flexible control in nonlinear optics and has potential applications in efficient wavelength conversion, all-optical computing. PMID:24247906

Compact and efficient blue laser sheet for measurement

NASA Astrophysics Data System (ADS)

Qi, Yan; Wang, Yu; Wu, Bin; Wang, Yanwei; Yan, Boxia

2017-10-01

Compact and efficient blue laser sheet has important applications in the field of measurement, with laser diode end pumped Nd:YAG directly and LBO intracavity frequency doubling, a compact and efficient CW 473nm blue laser sheet composed of dual path liner blue laser is realized. At an incident pump power of 12.4W, up to 1.4W output power of the compound blue laser is achieved, the optical-to-optical conversion efficiency is as high as 11.3%.

Increasing EUV source efficiency via recycling of radiation power

NASA Astrophysics Data System (ADS)

Hassanein, Ahmed; Sizyuk, Valeryi; Sizyuk, Tatyana; Johnson, Kenneth C.

2018-03-01

EUV source power is critical for advanced lithography, for achieving economical throughput performance and also for minimizing stochastic patterning effects. Power conversion efficiency can be increased by recycling plasma-scattered laser radiation and other out-of-band radiation back to the plasma via retroreflective optics. Radiation both within and outside of the collector light path can potentially be recycled. For recycling within the collector path, the system uses a diffractive collection mirror that concomitantly filters all laser and out-of-band radiation out of the EUV output. In this paper we review the optical design concept for power recycling and present preliminary plasma-physics simulation results showing a potential gain of 60% in EUV conversion efficiency.

Compact and efficient 2μm Tm:YAP lasers with mechanical or passive Q-switching

NASA Astrophysics Data System (ADS)

Cole, Brian; Goldberg, Lew

2017-02-01

We describe compact and efficient Q-switched diode-pumped, Tm:YAP lasers operating at 1.94μm. Laser CW and Q-switched performance is compared, using both compact mechanical as well as passive Q-switching. For passive Q-switching using a Cr:ZnS saturable absorber (unsaturated transmission of 95%), the laser produced 0.5mJ pulses with an average power of 4.4W and 6.5kW peak power, and had an optical efficiency of 30%. A resonant mirror mechanical Q-switch resulted in a 4 kHz PRF pulse train, with an optical slope efficiency of 52% and an optical-to-optical conversion efficiency of 41%. The laser generated 1.5 mJ, 45 ns FWHM, 33kW peak power pulses, and 6.2W of average output. A second mechanically Q-switched laser operating at 10 kHz PRF produced 1mJ, 35kW peak power pulses, generating 11W average power with an optical efficiency of 46%, and a beam quality of 1.4x diffraction limit.

Plasma q -plate for generation and manipulation of intense optical vortices

NASA Astrophysics Data System (ADS)

Qu, Kenan; Jia, Qing; Fisch, Nathaniel J.

2017-11-01

An optical vortex is a light wave with a twisting wavefront around its propagation axis and null intensity in the beam center. Its unique spatial structure of field lends itself to a broad range of applications, including optical communication, quantum information, superresolution microscopy, and multidimensional manipulation of particles. However, accessible intensity of optical vortices have been limited to material ionization threshold. This limitation might be removed by using the plasma medium. Here we propose the design of suitably magnetized plasmas which, functioning as a q -plate, leads to a direct conversion from a high-intensity Gaussian beam into a twisted beam. A circularly polarized laser beam in the plasma accumulates an azimuthal-angle-dependent phase shift and hence forms a twisting wavefront. Our three-dimensional particle-in-cell simulations demonstrate extremely high-power conversion efficiency. The plasma q -plate can work in a large range of frequencies spanning from terahertz to the optical domain.

Broadband Gerchberg-Saxton algorithm for freeform diffractive spectral filter design.

PubMed

Vorndran, Shelby; Russo, Juan M; Wu, Yuechen; Pelaez, Silvana Ayala; Kostuk, Raymond K

2015-11-30

A multi-wavelength expansion of the Gerchberg-Saxton (GS) algorithm is developed to design and optimize a surface relief Diffractive Optical Element (DOE). The DOE simultaneously diffracts distinct wavelength bands into separate target regions. A description of the algorithm is provided, and parameters that affect filter performance are examined. Performance is based on the spectral power collected within specified regions on a receiver plane. The modified GS algorithm is used to design spectrum splitting optics for CdSe and Si photovoltaic (PV) cells. The DOE has average optical efficiency of 87.5% over the spectral bands of interest (400-710 nm and 710-1100 nm). Simulated PV conversion efficiency is 37.7%, which is 29.3% higher than the efficiency of the better performing PV cell without spectrum splitting optics.

Bidirectional microwave-mechanical-optical transducer in a dilution refrigerator

NASA Astrophysics Data System (ADS)

Burns, Peter S.; Higginbotham, Andrew P.; Peterson, Robert W.; Urmey, Maxwell D.; Kampel, Nir S.; Menke, Timothy; Cicak, Katarina; Simmonds, Raymond. W.; Regal, Cindy A.; Lehnert, Konrad W.

Transferring quantum states between microwave and optical networks would be a powerful resource for quantum communication and computation. Our approach is to simultaneously couple one mode of a micromechanical oscillator to a resonant microwave circuit and a high-finesse optical cavity. Building on previous work demonstrating bidirectional and efficient classical conversion at 4 K, a new microwave-to-optical transducer is operated at 0.1 K and preparations are underway to operate it in the quantum regime. To improve transfer efficiency, we characterize and implement wireless microwave access to the converter chip. Transfer efficiency of the device is measured, and loss in the LC circuit due to laser light is characterized. We acknowledge support from AFOSR MURI Grant FA9550-15-1-0015 and PFC National Science Foundation Grant 1125844.

Antireflective Paraboloidal Microlens Film for Boosting Power Conversion Efficiency of Solar Cells.

PubMed

Fang, Chaolong; Zheng, Jun; Zhang, Yaoju; Li, Yijie; Liu, Siyuan; Wang, Weiji; Jiang, Tao; Zhao, Xuesong; Li, Zhihong

2018-06-21

Microlens arrays can improve light transmittance in optical devices or enhance the photoelectrical conversion efficiency of photovoltaic devices. Their surface morphology (aspect ratio and packed density) is vital to photon management in solar cells. Here, we report a 100% packed density paraboloidal microlens array (PMLA), with a large aspect ratio, fabricated by direct-write UV laser photolithography coupled with soft imprint lithography. Optical characterization shows that the PMLA structure can remarkably decrease the front-side reflectance of solar cell device. The measured electrical parameters of the solar cell device clearly and consistently demonstrate that the PMLA film can considerably improve the photoelectrical conversion efficiency. In addition, the PMLA film has superhydrophobic properties, verified by measurement of a large water contact angle, and can enhance the self-cleaning capability of solar cell devices.

Chaos-assisted broadband momentum transformation in optical microresonators

NASA Astrophysics Data System (ADS)

Jiang, Xuefeng; Shao, Linbo; Zhang, Shu-Xin; Yi, Xu; Wiersig, Jan; Wang, Li; Gong, Qihuang; Lončar, Marko; Yang, Lan; Xiao, Yun-Feng

2017-10-01

The law of momentum conservation rules out many desired processes in optical microresonators. We report broadband momentum transformations of light in asymmetric whispering gallery microresonators. Assisted by chaotic motions, broadband light can travel between optical modes with different angular momenta within a few picoseconds. Efficient coupling from visible to near-infrared bands is demonstrated between a nanowaveguide and whispering gallery modes with quality factors exceeding 10 million. The broadband momentum transformation enhances the device conversion efficiency of the third-harmonic generation by greater than three orders of magnitude over the conventional evanescent-wave coupling. The observed broadband and fast momentum transformation could promote applications such as multicolor lasers, broadband memories, and multiwavelength optical networks.

Defect-mediated photoluminescence up-conversion in cadmium sulfide nanobelts (Conference Presentation)

NASA Astrophysics Data System (ADS)

Morozov, Yurii; Kuno, Masaru K.

2017-02-01

The concept of optical cooling of solids has existed for nearly 90 years ever since Pringsheim proposed a way to cool solids through the annihilation of phonons via phonon-assisted photoluminescence (PL) up-conversion. In this process, energy is removed from the solid by the emission of photons with energies larger than those of incident photons. However, actually realizing optical cooling requires exacting parameters from the condensed phase medium such as near unity external quantum efficiencies as well as existence of a low background absorption. Until recently, laser cooling has only been successfully realized in rare earth doped solids. In semiconductors, optical cooling has very recently been demonstrated in cadmium sulfide (CdS) nanobelts as well as in hybrid lead halide perovskites. For the former, large internal quantum efficiencies, sub-wavelength thicknesses, which decrease light trapping, and low background absorption, all make near unity external quantum yields possible. Net cooling by as much as 40 K has therefore been possible with CdS nanobelts. In this study, we describe a detailed investigation of the nature of efficient anti-Stokes photoluminescence (ASPL) in CdS nanobelts. Temperature-dependent PL up-conversion and optical absorption studies on individual NBs together with frequency-dependent up-converted PL intensity spectroscopies suggest that ASPL in CdS nanobelts is defect-mediated through involvement of defect levels below the band gap.

Optical analysis of down-conversion OLEDs

NASA Astrophysics Data System (ADS)

Krummacher, Benjamin; Klein, Markus; von Malm, Norwin; Winnacker, Albrecht

2008-02-01

Phosphor down-conversion of blue organic light-emitting diodes (OLEDs) is one approach to generate white light, which offers the possibility of easy color tuning, a simple device architecture and color stability over lifetime. In this article previous work on down-conversion devices in the field of organic solid state lighting is briefly reviewed. Further, bottom emitting down-conversion OLEDs are studied from an optical point of view. Therefore the physical processes occurring in the down-conversion layer are translated into a model which is implemented in a ray tracing simulation. By comparing its predictions to experimental results the model is confirmed. For the experiments a blue-emitting polymer OLED (PLED) panel optically coupled to a series of down-conversion layers is used. Based on results obtained from ray tracing simulation some of the implications of the model for the performance of down-conversion OLEDs are discussed. In particular it is analysed how the effective reflectance of the underlying blue OLED and the particle size distribution of the phosphor powder embedded in the matrix of the down-conversion layer influence extraction efficiency.

Developments in Coherent Perfect Polarization Rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Andrews, James; Zhou, Chaunhong; Baker, Michael

2015-05-01

Coherent Perfect Polarization Rotation (CPR) is a useful technique akin to Coherent Perfect Absorption (CPA, also known as the anti-laser) but that results in very high efficiency optical mode conversion. We describe the analysis of recent experimental data from our CPR testbed, the use of CPR in miniaturizing optical isolators and CPR phenomena in non-linear optics. Work supported by the N.S.F. under Grant No. ECCS-1360725.

Kinetic modelling of the optically stimulated conversion of peaks 5a and 5 to peak 4 in LiF:Mg,Ti (TLD-100).

PubMed

Weizman, Y; Horowitz, Y S; Oster, L

2002-01-01

The TC/LC conversion model for peaks 4, 5a and 5 in LiF:Mg,Ti (TLD-100) has been studied by solution of the coupled differential equations describing the charge carrier traffic following optical stimulation. Aspects of the model investigated were (i) the two-component exponential decay of the composite peak 5 TL intensity following the bleach, (ii) the role of retrapping during bleaching, (iii) the hole nature of peak 4 and (iv) the conversion of peak 5a traps to peak 4 traps. The high conversion efficiency is naturally explained due to the absence of conduction band competitive mechanisms in the optical ionisation of the electron in the e-h occupied structure corresponding to peak 5a and thereby leading to the hole-only occupied TC/LC leading to peak 4.

High-Performance Flexible Waveguiding Photovoltaics

PubMed Central

Chou, Chun-Hsien; Chuang, Jui-Kang; Chen, Fang-Chung

2013-01-01

The use of flat-plane solar concentrators is an effective approach toward collecting sunlight economically and without sun trackers. The optical concentrators are, however, usually made of rigid glass or plastics having limited flexibility, potentially restricting their applicability. In this communication, we describe flexible waveguiding photovoltaics (FWPVs) that exhibit high optical efficiencies and great mechanical flexibility. We constructed these FWPVs by integrating poly-Si solar cells, a soft polydimethylsiloxane (PDMS) waveguide, and a TiO2-doped backside reflector. Optical microstructures that increase the light harvesting ability of the FWPVs can be fabricated readily, through soft lithography, on the top surface of the PDMS waveguide. Our optimized structure displayed an optical efficiency of greater than 42% and a certified power conversion efficiency (PCE) of 5.57%, with a projected PCE as high as approximately 18%. This approach might open new avenues for the harvesting of solar energy at low cost with efficient, mechanically flexible photovoltaics. PMID:23873225

Compact high-efficiency 100-W-level diode-side-pumped Nd:YAG laser with linearly polarized TEM00 mode output.

PubMed

Xu, Yi-Ting; Xu, Jia-Lin; Guo, Ya-Ding; Yang, Feng-Tu; Chen, Yan-Zhong; Xu, Jian; Xie, Shi-Yong; Bo, Yong; Peng, Qin-Jun; Cui, Dafu; Xu, Zu-Yan

2010-08-20

We present a compact high-efficiency and high-average-power diode-side-pumped Nd:YAG rod laser oscillator operated with a linearly polarized fundamental mode. The oscillator resonator is based on an L-shaped convex-convex cavity with an improved module and a dual-rod configuration for birefringence compensation. Under a pump power of 344 W, a linearly polarized average output power of 101.4 W at 1064 nm is obtained, which corresponds to an optical-to-optical conversion efficiency of 29.4%. The laser is operated at a repetition rate of 400 Hz with a beam quality factor of M(2)=1.14. To the best of our knowledge, this is the highest optical-to-optical efficiency for a side-pumped TEM(00) Nd:YAG rod laser oscillator with a 100-W-level output ever reported.

Sunlight absorption engineering for thermophotovoltaics: contributions from the optical design.

PubMed

Míguez, Hernán

2015-03-01

Nowadays, solar thermophotovoltaic systems constitute a platform in which sophisticated optical material designs are put into practice with the aim of achieving the long sought after dream of developing an efficient energy conversion device based on this concept. Recent advances demonstrate that higher efficiencies are at reach using photonic nanostructures amenable to mass production and scale-up. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flat nonlinear optics: metasurfaces for efficient frequency mixing

NASA Astrophysics Data System (ADS)

Nookala, Nishant; Lee, Jongwon; Liu, Yingnan; Bishop, Wells; Tymchenko, Mykhailo; Gomez-Diaz, J. Sebastian; Demmerle, Frederic; Boehm, Gerhard; Amann, Markus-Christian; Wolf, Omri; Brener, Igal; Alu, Andrea; Belkin, Mikhail A.

2017-02-01

Gradient metasurfaces, or ultrathin optical components with engineered transverse impedance gradients along the surface, are able to locally control the phase and amplitude of the scattered fields over subwavelength scales, enabling a broad range of linear components in a flat, integrable platform1-4. On the contrary, due to the weakness of their nonlinear optical responses, conventional nonlinear optical components are inherently bulky, with stringent requirements associated with phase matching and poor control over the phase and amplitude of the generated beam. Nonlinear metasurfaces have been recently proposed to enable frequency conversion in thin films without phase-matching constraints and subwavelength control of the local nonlinear phase5-8. However, the associated optical nonlinearities are far too small to produce significant nonlinear conversion efficiency and compete with conventional nonlinear components for pump intensities below the materials damage threshold. Here, we report multi-quantum-well based gradient nonlinear metasurfaces with second-order nonlinear susceptibility over 106 pm/V for second harmonic generation at a fundamental pump wavelength of 10 μm, 5-6 orders of magnitude larger than traditional crystals. Further, we demonstrate the efficacy of this approach to designing metasurfaces optimized for frequency conversion over a large range of wavelengths, by reporting multi-quantum-well and metasurface structures optimized for a pump wavelength of 6.7 μm. Finally, we demonstrate how the phase of this nonlinearly generated light can be locally controlled well below the diffraction limit using the Pancharatnam-Berry phase approach5,7,9, opening a new paradigm for ultrathin, flat nonlinear optical components.

Quantum optical measurement with tripartite entangled photons generated by triple parametric down-conversion

NASA Astrophysics Data System (ADS)

Cho, Minhaeng

2018-05-01

Parametric down-conversion is a second-order nonlinear optical process annihilating a pump photon and creating a pair of photons in the signal and idler modes. Then, by using two parametric down-converters and introducing a path indistinguishability for the two generated idler modes, a quantum coherence between two conjugate signal beams can be induced. Such a double spontaneous or stimulated parametric down-conversion scheme has been used to demonstrate quantum spectroscopy and imaging with undetected idler photons via measuring one-photon interference between their correlated signal beams. Recently, we considered another quantum optical measurement scheme utilizing W-type tripartite entangled signal photons that can be generated by employing three spontaneous parametric down-conversion crystals and by inducing coherences or path-indistinguishabilities between their correlated idler beams and between quantum vacuum fields. Here, we consider an extended triple stimulated parametric down-conversion scheme for quantum optical measurement of sample properties with undetected idler and photons. Noting the real effect of vacuum field indistinguishability on the fringe visibility as well as the role of zero-point field energy in the interferometry, we show that this scheme is an ideal and efficient way to create a coherent state of W-type entangled signal photons. We anticipate that this scheme would be of critical use in further developing quantum optical measurements in spectroscopy and microscopy with undetected photons.

Quantum optical measurement with tripartite entangled photons generated by triple parametric down-conversion.

PubMed

Cho, Minhaeng

2018-05-14

Parametric down-conversion is a second-order nonlinear optical process annihilating a pump photon and creating a pair of photons in the signal and idler modes. Then, by using two parametric down-converters and introducing a path indistinguishability for the two generated idler modes, a quantum coherence between two conjugate signal beams can be induced. Such a double spontaneous or stimulated parametric down-conversion scheme has been used to demonstrate quantum spectroscopy and imaging with undetected idler photons via measuring one-photon interference between their correlated signal beams. Recently, we considered another quantum optical measurement scheme utilizing W-type tripartite entangled signal photons that can be generated by employing three spontaneous parametric down-conversion crystals and by inducing coherences or path-indistinguishabilities between their correlated idler beams and between quantum vacuum fields. Here, we consider an extended triple stimulated parametric down-conversion scheme for quantum optical measurement of sample properties with undetected idler and photons. Noting the real effect of vacuum field indistinguishability on the fringe visibility as well as the role of zero-point field energy in the interferometry, we show that this scheme is an ideal and efficient way to create a coherent state of W-type entangled signal photons. We anticipate that this scheme would be of critical use in further developing quantum optical measurements in spectroscopy and microscopy with undetected photons.

High efficiency, linearly polarized, directly diode-pumped Er:YAG laser at 1617  nm.

PubMed

Yu, Zhenzhen; Wang, Mingjian; Hou, Xia; Chen, Weibiao

2014-12-01

An efficient, directly diode-pumped Er:YAG laser at 1617 nm was demonstrated. A folding mirror with high reflectivity for the s-polarized light at the laser wavelength was used to achieve a linearly polarized laser. A maximum continuous-wave output power of 7.73 W was yielded under incident pump power of 50.57 W, and the optical conversion efficiency with respect to incident pump power was ∼15.28%, which was the highest optical conversion efficiency with directly diode-pumped Er:YAG lasers up to now; in Q-switched operation, the maximum pulse energy of 7.82 mJ was generated with pulse duration of about 80 ns at a pulse repetition frequency of 500 Hz.

Integrated liquid-core optical fibers for ultra-efficient nonlinear liquid photonics.

PubMed

Kieu, K; Schneebeli, L; Norwood, R A; Peyghambarian, N

2012-03-26

We have developed a novel integrated platform for liquid photonics based on liquid core optical fiber (LCOF). The platform is created by fusion splicing liquid core optical fiber to standard single-mode optical fiber making it fully integrated and practical - a major challenge that has greatly hindered progress in liquid-photonic applications. As an example, we report here the realization of ultralow threshold Raman generation using an integrated CS₂ filled LCOF pumped with sub-nanosecond pulses at 532 nm and 1064 nm. The measured energy threshold for the Stokes generation is 1nJ, about three orders of magnitude lower than previously reported values in the literature for hydrogen gas, a popular Raman medium. The integrated LCOF platform opens up new possibilities for ultralow power nonlinear optics such as efficient white light generation for displays, mid-IR generation, slow light generation, parametric amplification, all-optical switching and wavelength conversion using liquids that have orders of magnitude larger optical nonlinearities compared with silica glass.

All-fiber hybrid photon-plasmon circuits: integrating nanowire plasmonics with fiber optics.

PubMed

Li, Xiyuan; Li, Wei; Guo, Xin; Lou, Jingyi; Tong, Limin

2013-07-01

We demonstrate all-fiber hybrid photon-plasmon circuits by integrating Ag nanowires with optical fibers. Relying on near-field coupling, we realize a photon-to-plasmon conversion efficiency up to 92% in a fiber-based nanowire plasmonic probe. Around optical communication band, we assemble an all-fiber resonator and a Mach-Zehnder interferometer (MZI) with Q-factor of 6 × 10(6) and extinction ratio up to 30 dB, respectively. Using the MZI, we demonstrate fiber-compatible plasmonic sensing with high sensitivity and low optical power.

Effect of idler absorption in pulsed optical parametric oscillators.

PubMed

Rustad, Gunnar; Arisholm, Gunnar; Farsund, Øystein

2011-01-31

Absorption at the idler wavelength in an optical parametric oscillator (OPO) is often considered detrimental. We show through simulations that pulsed OPOs with significant idler absorption can perform better than OPOs with low idler absorption both in terms of conversion efficiency and beam quality. The main reason for this is reduced back conversion. We also show how the beam quality depends on the beam width and pump pulse length, and present scaling relations to use the example simulations for other pulsed nanosecond OPOs.

Research and evolution of mid-infrared optical source

NASA Astrophysics Data System (ADS)

Chen, Changshui; Hu, Hui; Xu, Lei

2016-10-01

3-5 μm mid-infrared wave band is in the atmosphere window, it has lots of promising applications on the spectroscopy, remote sensing, medical treatment, environmental protection and military affairs. So, it has been a hot topic around the world to research the lasers at this wave band. In recent years, adiabatic passage technology has been applied in frequency conversion area, which borrowed from atomic physics. In this paper we will introduce efficient nonlinear optics frequency conversion by suing this technology.

Low-frequency acousto-optic backscattering of Bessel light beams

NASA Astrophysics Data System (ADS)

Khilo, Nikolai A.; Belyi, Vladimir N.; Khilo, Petr A.; Kazak, Nikolai S.

2018-05-01

The use of Bessel light beams, as well as Bessel acoustic beams, substantially enhances the capabilities of acousto-optic methods for control of optical field. We present a theoretical study of the process of optical Bessel beams conversion by means of backward acousto-optic scattering on a Bessel acoustic field in a transversely isotropic crystal. It is shown that, with an appropriate choice of Bessel beams parameters, the backscattering in visible spectral range can be realized at relatively low acoustic frequencies less than one gigahertz. Under conditions of phase matching and transverse spatial synchronism, the efficiency of backscattering is sufficiently high, which is interesting, for example, for construction of acousto-optic spectral analyzers.

High-Power Single- and Dual-Wavelength Nd:GdVO4 Lasers with Potential Application for the Treatment of Telangiectasia

NASA Astrophysics Data System (ADS)

Chen, Lijuan; Wang, Zhengping; Yu, Haohai; Zhuang, Shidong; Han, Shuo; Zhao, Yongguang; Xu, Xinguang

2012-11-01

Diode-end-pumped high-power Nd:GdVO4 lasers at 1083 nm are presented. The maximum continuous-wave output power was 10.1 W with an optical conversion efficiency of 31.3%. For acoustooptic (AO) Q-switched operation, the largest pulse energy, shortest pulse width, and highest peak power were 111 µJ, 77 ns, and 1.44 kW, respectively. By decreasing the 1063 nm transmission of the output coupler, we also achieved efficient CW dual-wavelength operation at 1083 and 1063 nm. Their total output power reached 6.7 W, and the optical conversion efficiency reached 31.6%. These lasers have special requirements in the treatment of facial telangiectasia.

A path to practical Solar Pumped Lasers via Radiative Energy Transfer

DOE PAGES

Reusswig, Philip D.; Nechayev, Sergey; Scherer, Jennifer M.; ...

2015-10-05

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd 3+ -doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CWmore » solar lasing threshold of 23 W-cm -2, or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.« less

Liquid-crystal-based switchable polarizers for sensor protection.

PubMed

Wu, C S; Wu, S T

1995-11-01

Linear polarizers are generally employed in conjunction with advanced liquid-crystal filters for the protection of human eyes and optical sensors. For detection sensitivity under a no-threat condition to be maximized, the polarizer should remain in a clear state with a minimum insertion loss. When threats are present, it should be quickly switched to function as a linear polarizer with a high extinction ratio. Two types of switchable polarizer for sensor protection are demonstrated. The polarization conversion type exhibits a high optical efficiency in its clear state, a high extinction ratio in the linear polarizer state, and a fast switching speed, except that its field of view is limited to approximately ±10°. In contrast, an improved switchable dichroic polarizer functions effectively over a much wider field of view. However, its extinction ratio and optical efficiency in its clear state are lower than those of the polarization conversion type.

A path to practical Solar Pumped Lasers via Radiative Energy Transfer

PubMed Central

Reusswig, Philip D.; Nechayev, Sergey; Scherer, Jennifer M.; Hwang, Gyu Weon; Bawendi, Moungi G.; Baldo, Marc. A.; Rotschild, Carmel

2015-01-01

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd3+-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm−2, or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns. PMID:26434400

Liquid-crystal-based switchable polarizers for sensor protection

NASA Astrophysics Data System (ADS)

Wu, Chiung-Sheng; Wu, Shin-Tson

1995-11-01

Linear polarizers are generally employed in conjunction with advanced liquid-crystal filters for the protection of human eyes and optical sensors. For detection sensitivity under a no-threat condition to be maximized, the polarizer should remain in a clear state with a minimum insertion loss. When threats are present, it should be quickly switched to function as a linear polarizer with a high extinction ratio. Two types of switchable polarizer for sensor protection are demonstrated. The polarization conversion type exhibits a high optical efficiency in its clear state, a high extinction ratio in the linear polarizer state, and a fast switching speed, except that its field of view is limited to approximately +/-10 deg In contrast, an improved switchable dichroic polarizer functions effectively over a much wider field of view. However, its extinction ratio and optical efficiency in its clear state are lower than those of the polarization conversion type.

A path to practical Solar Pumped Lasers via Radiative Energy Transfer.

PubMed

Reusswig, Philip D; Nechayev, Sergey; Scherer, Jennifer M; Hwang, Gyu Weon; Bawendi, Moungi G; Baldo, Marc A; Rotschild, Carmel

2015-10-05

The optical conversion of incoherent solar radiation into a bright, coherent laser beam enables the application of nonlinear optics to solar energy conversion and storage. Here, we present an architecture for solar pumped lasers that uses a luminescent solar concentrator to decouple the conventional trade-off between solar absorption efficiency and the mode volume of the optical gain material. We report a 750-μm-thick Nd(3+)-doped YAG planar waveguide sensitized by a luminescent CdSe/CdZnS (core/shell) colloidal nanocrystal, yielding a peak cascade energy transfer of 14%, a broad spectral response in the visible portion of the solar spectrum, and an equivalent quasi-CW solar lasing threshold of 23 W-cm(-2), or approximately 230 suns. The efficient coupling of incoherent, spectrally broad sunlight in small gain volumes should allow the generation of coherent laser light from intensities of less than 100 suns.

Selective optical contacting for solar spectrum management

NASA Astrophysics Data System (ADS)

Yang, Jianfeng; Chen, Weijian; Wang, Bo; Zhang, Zhilong; Huang, Shujuan; Shrestha, Santosh; Wen, Xiaoming; Patterson, Robert; Conibeer, Gavin

2017-02-01

Solar spectrum management using up/down conversion is an important method to improve the photovoltaic energy conversion efficiency. It asks for a monochromatic luminescence absorption at the band edge of the photovoltaic device to reduce both the sub-band-gap and over-band-gap energy losses. Here, we demonstrate an energy selective optical contacting concept to improve the luminescence transfer efficiency for spectrum management. By increasing both the luminescence emission and re-absorption ability through photonic resonance, an efficient photon transfer channel could be established between the luminescence emitter and the photovoltaic component in a near-field region. This concept is not only able to compensate the insufficient band edge absorption ability of the photovoltaic device, but also to break the far-field limitation of luminescence radiation. The energy selection on the optical spectrum naturally imposed by the mode resonance is also helpful to improve the monochromaticity of the luminescence yield. In this paper, a photonic crystal cavity is used to realize the optical contacting concept between a thin silicon film and spectrum converter. The optical power and photon flux transferred between different components are calculated analytically using the electromagnetic Green's function. The corresponding radiative dipole moment is estimated by the fluctuation-dissipation theorem. The example shows an over 80 times enhancement in the luminescence absorbance by the silicon layer, illustrating the great potential of this concept to be applied on nano-structured photovoltaic devices.

Advanced laser architectures for high power eyesafe illuminators

NASA Astrophysics Data System (ADS)

Baranova, N.; Pati, B.; Stebbins, K.; Bystryak, I.; Rayno, M.; Ezzo, K.; DePriest, C.

2018-02-01

Q-Peak has demonstrated a novel pulsed eyesafe laser architecture operating with >50 mJ pulse energies at Pulse Repetition Frequencies (PRFs) as high as 320 Hz. The design leverages an Optical Parametric Oscillator (OPO) and Optical Parametric Amplifier (OPA) geometry, which provides the unique capability for high power in a comparatively compact package, while also offering the potential for additional eyesafe power scaling. The laser consists of a Commercial Off-the-Shelf (COTS) Q-switched front-end seed laser to produce pulse-widths around 10 ns at 1.06-μm, which is then followed by a pair of Multi-Pass Amplifier (MPA) architectures (comprised of side-pumped, multi-pass Nd:YAG slabs with a compact diode-pump-array imaging system), and finally involving two sequential nonlinear optical conversion architectures for transfer into the eyesafe regime. The initial seed beam is first amplified through the MPA, and then split into parallel optical paths. An OPO provides effective nonlinear conversion on one optical path, while a second MPA further amplifies the 1.06-μm beam for use in pumping an OPA on the second optical path. These paths are then recombined prior to seeding the OPA. Each nonlinear conversion subsystem utilizes Potassium Titanyl Arsenate (KTA) for effective nonlinear conversion with lower risk to optical damage. This laser architecture efficiently produces pulse energies of >50 mJ in the eyesafe band at PRFs as high as 320 Hz, and has been designed to fit within a volume of 4,500 in3 (0.074 m3 ). We will discuss theoretical and experimental details of the nonlinear optical system for achieving higher eyesafe powers.

Resonantly enhanced second-harmonic generation using III–V semiconductor all-dielectric metasurfaces

DOE PAGES

Liu, Sheng; Sinclair, Michael B.; Saravi, Sina; ...

2016-08-08

Nonlinear optical phenomena in nanostructured materials have been challenging our perceptions of nonlinear optical processes that have been explored since the invention of lasers. For example, the ability to control optical field confinement, enhancement, and scattering almost independently allows nonlinear frequency conversion efficiencies to be enhanced by many orders of magnitude compared to bulk materials. Also, the subwavelength length scale renders phase matching issues irrelevant. Compared with plasmonic nanostructures, dielectric resonator metamaterials show great promise for enhanced nonlinear optical processes due to their larger mode volumes. Here, we present, for the first time, resonantly enhanced second-harmonic generation (SHG) using galliummore » arsenide (GaAs) based dielectric metasurfaces. Using arrays of cylindrical resonators we observe SHG enhancement factors as large as 10 4 relative to unpatterned GaAs. At the magnetic dipole resonance, we measure an absolute nonlinear conversion efficiency of ~2 × 10 –5 with ~3.4 GW/cm 2 pump intensity. In conclusion, the polarization properties of the SHG reveal that both bulk and surface nonlinearities play important roles in the observed nonlinear process.« less

Refraction-Assisted Solar Thermoelectric Generator based on Phase-Change Lens

PubMed Central

Kim, Myoung-Soo; Kim, Min-Ki; Jo, Sung-Eun; Joo, Chulmin; Kim, Yong-Jun

2016-01-01

Solar thermoelectric generators (STEGs), which are used for various applications, (particularly small size electronic devices), have optical concentration systems for high energy conversion efficiency. In this study, a refraction-assisted STEG (R-STEG) is designed based on phase-change materials. As the phase-change material (PCM) changes phase from solid to liquid, its refractive index and transmittance also change, resulting in changes in the refraction of the sunlight transmitted through it, and concentration of solar energy in the phase-change lens. This innovative design facilitates double focusing the solar energy through the optical lens and a phase-change lens. This mechanism resulted in the peak energy conversion efficiencies of the R-STEG being 60% and 86% higher than those of the typical STEG at solar intensities of 1 kW m−2 and 1.5 kW m−2, respectively. In addition, the energy stored in PCM can help to generate steady electrical energy when the solar energy was removed. This work presents significant progress regarding the optical characteristic of PCM and optical concentration systems of STEGs. PMID:27283350

Refraction-Assisted Solar Thermoelectric Generator based on Phase-Change Lens.

PubMed

Kim, Myoung-Soo; Kim, Min-Ki; Jo, Sung-Eun; Joo, Chulmin; Kim, Yong-Jun

2016-06-10

Solar thermoelectric generators (STEGs), which are used for various applications, (particularly small size electronic devices), have optical concentration systems for high energy conversion efficiency. In this study, a refraction-assisted STEG (R-STEG) is designed based on phase-change materials. As the phase-change material (PCM) changes phase from solid to liquid, its refractive index and transmittance also change, resulting in changes in the refraction of the sunlight transmitted through it, and concentration of solar energy in the phase-change lens. This innovative design facilitates double focusing the solar energy through the optical lens and a phase-change lens. This mechanism resulted in the peak energy conversion efficiencies of the R-STEG being 60% and 86% higher than those of the typical STEG at solar intensities of 1 kW m(-2) and 1.5 kW m(-2), respectively. In addition, the energy stored in PCM can help to generate steady electrical energy when the solar energy was removed. This work presents significant progress regarding the optical characteristic of PCM and optical concentration systems of STEGs.

Design of a broadband reciprocal optical diode in multimode silicon waveguide by partial depth etching

NASA Astrophysics Data System (ADS)

Zhu, Danfeng; Zhang, Jinqiannan; Ye, Han; Yu, Zhongyuan; Liu, Yumin

2018-07-01

We propose a design of reciprocal optical diode based on asymmetric spatial mode conversion in multimode silicon waveguide on the silicon-on-insulator platform. The design possesses large bandwidth, high contrast ratio and high fabrication tolerance. The forward even-to-odd mode conversion and backward blockade of even mode are achieved by partial depth etching in the functional region. Simulated by three-dimension finite-difference time-domain method, the forward transmission efficiency is about -2.05 dB while the backward transmission efficiency is only -22.68 dB, reaching a highest contrast ratio of 0.983 at the wavelength of 1550 nm. The operational bandwidth is up to 200 nm (from 1450 nm to 1650 nm) with contrast ratio higher than 0.911. The numerical analysis also demonstrates that the proposed optical diode possesses high tolerance for geometry parameter errors which may be introduced in fabrication. The design based on partial depth etching is compatible with CMOS process and is expected to contribute to the silicon-based all-optical circuits.

Reactive granular optics for passive tracking of the sun

NASA Astrophysics Data System (ADS)

Frenkel, I.; Niv, A.

2017-08-01

The growing need for cost-effective renewable energy sources is hampered by the stagnation in solar cell technology, thus preventing a substantial reduction in the module and energy-production price. Lowering the energy-production cost could be achieved by using modules with efficiency. One of the possible means for increasing the module efficiency is concentrated photovoltaics (CPV). CPV, however, requires complex and accurate active tracking of the sun that reduces much of its cost-effectiveness. Here, we propose a passive tracking scheme based on a reactive optical device. The optical reaction is achieved by a new kind of light activated mechanical force that acts on micron-sized particles. This optical force allows the formation of granular disordered optical media that can be switched from being opaque to become transparent based on the intensity of light it interacts with. Such media gives rise to an efficient passive tracking scheme that when combined with an external optical cavity forms a new solar power conversion approach. Being external to the cell itself, this approach is indifferent to the type of semiconducting material that is used, as well as to other aspects of the cell design. This, in turn, liberates the cell layout from its optical constraints thus paving the way to higher efficiencies at lower module price.

Efficiency of Synchrotron Radiation from Rotation-powered Pulsars

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kisaka, Shota; Tanaka, Shuta J., E-mail: kisaka@phys.aoyama.ac.jp, E-mail: sjtanaka@center.konan-u.ac.jp

2017-03-01

Synchrotron radiation is widely considered to be the origin of the pulsed non-thermal emissions from rotation-powered pulsars in optical and X-ray bands. In this paper, we study the synchrotron radiation emitted by the created electron and positron pairs in the pulsar magnetosphere to constrain the energy conversion efficiency from the Poynting flux to the particle energy flux. We model two pair creation processes, two-photon collision, which efficiently works in young γ -ray pulsars (≲10{sup 6} year), and magnetic pair creation, which is the dominant process to supply pairs in old pulsars (≳10{sup 6} year). Using the analytical model, we derivemore » the maximum synchrotron luminosity as a function of the energy conversion efficiency. From the comparison with observations, we find that the energy conversion efficiency to the accelerated particles should be an order of unity in the magnetosphere, even though we make a number of the optimistic assumptions to enlarge the synchrotron luminosity. In order to explain the luminosity of the non-thermal X-ray/optical emission from pulsars with low spin-down luminosity L {sub sd} ≲ 10{sup 34} erg s{sup −1}, non-dipole magnetic field components should be dominant at the emission region. For the γ -ray pulsars with L {sub sd} ≲ 10{sup 35} erg s{sup −1}, observed γ -ray to X-ray and optical flux ratios are much higher than the flux ratio between curvature and the synchrotron radiations. We discuss some possibilities such as the coexistence of multiple accelerators in the magnetosphere as suggested from the recent numerical simulation results. The obtained maximum luminosity would be useful to select observational targets in X-ray and optical bands.« less

Phase Conjugated and Transparent Wavelength Conversions of Nyquist 16-QAM Signals Employing a Single-Layer Graphene Coated Fiber Device

PubMed Central

Hu, Xiao; Zeng, Mengqi; Long, Yun; Liu, Jun; Zhu, Yixiao; Zou, Kaiheng; Zhang, Fan; Fu, Lei; Wang, Jian

2016-01-01

We fabricate a nonlinear optical device based on a fiber pigtail cross-section coated with a single-layer graphene grown by chemical vapor deposition (CVD) method. Using the fabricated graphene-assisted nonlinear optical device and employing Nyquist 16-ary quadrature amplitude modulation (16-QAM) signal, we experimentally demonstrate phase conjugated wavelength conversion by degenerate four-wave mixing (FWM) and transparent wavelength conversion by non-degenerate FWM in graphene. We study the conversion efficiency as functions of the pump power and pump wavelength and evaluate the bit-error rate (BER) performance. We also compare the time-varying symbol sequence for graphene-assisted phase conjugated and transparent wavelength conversions of Nyquist 16-QAM signal. PMID:26932470

How nonlinear optics can merge interferometry for high resolution imaging

NASA Astrophysics Data System (ADS)

Ceus, D.; Reynaud, F.; Tonello, A.; Delage, L.; Grossard, L.

2017-11-01

High resolution stellar interferometers are very powerful efficient instruments to get a better knowledge of our Universe through the spatial coherence analysis of the light. For this purpose, the optical fields collected by each telescope Ti are mixed together. From the interferometric pattern, two expected information called the contrast Cij and the phase information φij are extracted. These information lead to the Vij, called the complex visibility, with Vij=Cijexp(jφij). For each telescope doublet TiTj, it is possible to get a complex visibility Vij. The Zernike Van Cittert theorem gives a relationship between the intensity distribution of the object observed and the complex visibility. The combination of the acquired complex visibilities and a reconstruction algorithm allows imaging reconstruction. To avoid lots of technical difficulties related to infrared optics (components transmission, thermal noises, thermal cooling…), our team proposes to explore the possibility of using nonlinear optical techniques. This is a promising alternative detection technique for detecting infrared optical signals. This way, we experimentally demonstrate that frequency conversion does not result in additional bias on the interferometric data supplied by a stellar interferometer. In this presentation, we report on wavelength conversion of the light collected by each telescope from the infrared domain to the visible. The interferometric pattern is observed in the visible domain with our, so called, upconversion interferometer. Thereby, one can benefit from mature optical components mainly used in optical telecommunications (waveguide, coupler, multiplexer…) and efficient low-noise detection schemes up to the single-photon counting level.

Extreme triple asymmetric (ETAS) epitaxial designs for increased efficiency at high powers in 9xx-nm diode lasers

NASA Astrophysics Data System (ADS)

Kaul, T.; Erbert, G.; Maaßdorf, A.; Martin, D.; Crump, P.

2018-02-01

Broad area lasers that are tailored to be most efficient at the highest achievable optical output power are sought by industry to decrease operation costs and improve system performance. Devices using Extreme-Double-ASymmetric (EDAS) epitaxial designs are promising candidates for improved efficiency at high optical output powers due to low series resistance, low optical loss and low carrier leakage. However, EDAS designs leverage ultra-thin p-side waveguides, meaning that the optical mode is shifted into the n-side waveguide, resulting in a low optical confinement in the active region, low gain and hence high threshold current, limiting peak performance. We introduce here explicit design considerations that enable EDAS-based devices to be developed with increased optical confinement in the active layer without changing the p-side layer thicknesses. Specifically, this is realized by introducing a third asymmetric component in the vicinity of the quantum well. We call this approach Extreme-Triple-ASymmetric (ETAS) design. A series of ETAS-based vertical designs were fabricated into broad area lasers that deliver up to 63% power conversion efficiency at 14 W CW optical output power from a 100 μm stripe laser, which corresponds to the operation point of a kW optical output power in a laser bar. The design process, the impact of structural changes on power saturation mechanisms and finally devices with improved performance will be presented.

Optical Time Reversal from Time-Dependent Epsilon-Near-Zero Media

NASA Astrophysics Data System (ADS)

Vezzoli, Stefano; Bruno, Vincenzo; DeVault, Clayton; Roger, Thomas; Shalaev, Vladimir M.; Boltasseva, Alexandra; Ferrera, Marcello; Clerici, Matteo; Dubietis, Audrius; Faccio, Daniele

2018-01-01

Materials with a spatially uniform but temporally varying optical response have applications ranging from magnetic field-free optical isolators to fundamental studies of quantum field theories. However, these effects typically become relevant only for time variations oscillating at optical frequencies, thus presenting a significant hurdle that severely limits the realization of such conditions. Here we present a thin-film material with a permittivity that pulsates (uniformly in space) at optical frequencies and realizes a time-reversing medium of the form originally proposed by Pendry [Science 322, 71 (2008), 10.1126/science.1162087]. We use an optically pumped, 500 nm thick film of epsilon-near-zero (ENZ) material based on Al-doped zinc oxide. An incident probe beam is both negatively refracted and time reversed through a reflected phase-conjugated beam. As a result of the high nonlinearity and the refractive index that is close to zero, the ENZ film leads to time reversed beams (simultaneous negative refraction and phase conjugation) with near-unit efficiency and greater-than-unit internal conversion efficiency. The ENZ platform therefore presents the time-reversal features required, e.g., for efficient subwavelength imaging, all-optical isolators and fundamental quantum field theory studies.

New strategy to promote conversion efficiency using high-index nanostructures in thin-film solar cells

PubMed Central

Wang, DongLin; Su, Gang

2014-01-01

Nano-scaled metallic or dielectric structures may provide various ways to trap light into thin-film solar cells for improving the conversion efficiency. In most schemes, the textured active layers are involved into light trapping structures that can provide perfect optical benefits but also bring undesirable degradation of electrical performance. Here we propose a novel approach to design high-performance thin-film solar cells. In our strategy, a flat active layer is adopted for avoiding electrical degradation, and an optimization algorithm is applied to seek for an optimized light trapping structure for the best optical benefit. As an example, we show that the efficiency of a flat a-Si:H thin-film solar cell can be promoted close to the certified highest value. It is also pointed out that, by choosing appropriate dielectric materials with high refractive index (>3) and high transmissivity in wavelength region of 350 nm–800 nm, the conversion efficiency of solar cells can be further enhanced. PMID:25418477

Plasma q -plate for generation and manipulation of intense optical vortices

DOE PAGES

Qu, Kenan; Jia, Qing; Fisch, Nathaniel J.

2017-11-28

An optical vortex is a light wave with a twisting wavefront around its propagation axis and null intensity in the beam center. Its unique spatial structure of field lends itself to a broad range of applications, including optical communication, quantum information, superresolution microscopy, and multidimensional manipulation of particles. However, accessible intensity of optical vortices have been limited to material ionization threshold. This limitation might be removed by using the plasma medium. Here in this paper, we propose the design of suitably magnetized plasmas which, functioning as a q-plate, leads to a direct conversion from a high-intensity Gaussian beam into amore » twisted beam. A circularly polarized laser beam in the plasma accumulates an azimuthal-angle-dependent phase shift and hence forms a twisting wavefront. Our three-dimensional particle-in-cell simulations demonstrate extremely high-power conversion efficiency. The plasma q-plate can work in a large range of frequencies spanning from terahertz to the optical domain.« less

High efficient photothermal energy conversion of topologic insulator Bi2Se3 nanosheets thin film

NASA Astrophysics Data System (ADS)

Liu, Yanling; Zhang, Yanbang; Zhao, Zejia; Jia, Guozhi

2018-05-01

The photothermal conversion has become rather attractive to realize the heat energy application. A simple, rapid and scalable optical-controlling Bi2Se3 nanosheets film heater is prepared by softly nondestructive rubbing technology and then transferring to PET substrate under the assistance of PVA. The optical-controlling film heater exhibits the excellent adjustability, accuracy and stability of temperature. The film heater is first tested by using laser irradiation at 410 mW and the corresponding temperature rapidly increased to the 53.2 °C for SThin film and 73.2 °C for SThick film during 50 seconds. The SThin and SThick film display a transmittance of 40% to 60% from the visible to near-IR region, respectively. As-prepared optical-controlling Bi2Se3 film heater can be easily integrated to optical or photo-electric device without preparation of electrode. These exotic properties of Bi2Se3 nanosheets optical-controlling heater suggest exciting prospects for the temperature-dependent flexible optoelectronics and electronic device.

Plasma q -plate for generation and manipulation of intense optical vortices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qu, Kenan; Jia, Qing; Fisch, Nathaniel J.

An optical vortex is a light wave with a twisting wavefront around its propagation axis and null intensity in the beam center. Its unique spatial structure of field lends itself to a broad range of applications, including optical communication, quantum information, superresolution microscopy, and multidimensional manipulation of particles. However, accessible intensity of optical vortices have been limited to material ionization threshold. This limitation might be removed by using the plasma medium. Here in this paper, we propose the design of suitably magnetized plasmas which, functioning as a q-plate, leads to a direct conversion from a high-intensity Gaussian beam into amore » twisted beam. A circularly polarized laser beam in the plasma accumulates an azimuthal-angle-dependent phase shift and hence forms a twisting wavefront. Our three-dimensional particle-in-cell simulations demonstrate extremely high-power conversion efficiency. The plasma q-plate can work in a large range of frequencies spanning from terahertz to the optical domain.« less

Electrical efficiency and droop in MQW LEDs

NASA Astrophysics Data System (ADS)

Malyutenko, V. K.

2014-02-01

It is believed that low power conversion efficiency in commercial MQW LEDs occurs as a result of efficiency droop, current-induced dynamic degradation of the internal quantum efficiency, injection efficiency, and extraction efficiency. Broadly speaking, all these "quenching" mechanisms could be referred to as the optical losses. The vast advances of high-power InGaN and AlGaInP MQW LEDs have been achieved by addressing these losses. In contrast to these studies, in this paper we consider an alternative approach to make high-power LEDs more efficient. We identify current-induced electrical efficiency degradation (EED) as a strong limiting factor of power conversion efficiency. We found that EED is caused by current crowding followed by an increase in current-induced series resistance of a device. By decreasing the current spreading length, EED also causes the optical efficiency to degrade and stands for an important aspect of LED performance. This paper gives scientists the opportunity to look for different attributes of EED.

Highly nonlinear organic crystal OHQ-T for efficient ultra-broadband terahertz wave generation beyond 10 THz.

PubMed

Kang, Bong Joo; Baek, In Hyung; Lee, Seung-Heon; Kim, Won Tae; Lee, Seung-Jun; Jeong, Young Uk; Kwon, O-Pil; Rotermund, Fabian

2016-05-16

We report on efficient generation of ultra-broadband terahertz (THz) waves via optical rectification in a novel nonlinear organic crystal with acentric core structure, i.e. 2-(4-hydroxystyryl)-1-methylquinolinium 4-methylbenzenesulfonate (OHQ-T), which possesses an ideal molecular structure leading to a maximized nonlinear optical response for near-infrared-pumped THz wave generation. By systematic studies on wavelength-dependent phase-matching conditions in OHQ-T crystals of different thicknesses we are able to generate coherent THz waves with a high peak-to-peak electric field amplitude of up to 650 kV/cm and an upper cut-off frequency beyond 10 THz. High optical-to-THz conversion efficiency of 0.31% is achieved by efficient index matching with a selective pumping at 1300 nm.

Maximizing the short circuit current of organic solar cells by partial decoupling of electrical and optical properties

NASA Astrophysics Data System (ADS)

Qarony, Wayesh; Hossain, Mohammad I.; Jovanov, Vladislav; Knipp, Dietmar; Tsang, Yuen Hong

2018-03-01

The partial decoupling of electronic and optical properties of organic solar cells allows for realizing solar cells with increased short circuit current and energy conversion efficiency. The proposed device consists of an organic solar cell conformally prepared on the surface of an array of single and double textured pyramids. The device geometry allows for increasing the optical thickness of the organic solar cell, while the electrical thickness is equal to the nominal thickness of the solar cell. By increasing the optical thickness of the solar cell, the short circuit current is distinctly increased. The quantum efficiency and short circuit current are determined using finite-difference time-domain simulations of the 3D solar cell structure. The influence of different solar cell designs on the quantum efficiency and short circuit current is discussed and optimal device dimensions are proposed.

Integrated optical signal processing with magnetostatic waves

NASA Technical Reports Server (NTRS)

Fisher, A. D.; Lee, J. N.

1984-01-01

Magneto-optical devices based on Bragg diffraction of light by magnetostatic waves (MSW's) offer the potential of large time-bandwidth optical signal processing at microwave frequencies of 1 to 20 GHz and higher. A thin-film integrated-optical configuration, with the interacting MSW and guided-optical wave both propagating in a common ferrite layer, is necessary to avoid shape-factor demagnetization effects. The underlying theory of the MSW-optical interaction is outlined, including the development of expressions for optical diffraction efficiency as a function of MSW power and other relevant parameters. Bradd diffraction of guided-optical waves by transversely-propagating magnetostatic waves and collinear TE/TM mode conversion included by MSW's have been demonstrated in yttrium iron garnet (YIG) thin films. Diffraction levels as large as 4% (7 mm interaction length) and a modulation dynamic range of approx 30 dB have been observed. Advantages of these MSW-based devices over the analogous acousto-optical devices include: much greater operating frequencies, tunability of the MSW dispersion relation by varying either the RF frequency or the applied bias magnetic field, simple broad-band MSW transducer structures (e.g., a single stripline), and the potential for very high diffraction efficiencies.

Numerical investigation of output beam quality in efficient broadband optical parametric chirped pulse amplification

NASA Astrophysics Data System (ADS)

Liu, Xiao-Di; Xu, Lu; Liang, Xiao-Yan

2017-01-01

We theoretically analyzed output beam quality of broad bandwidth non-collinear optical parametric chirped pulse amplification (NOPCPA) in LiB3O5 (LBO) centered at 800 nm. With a three-dimensional numerical model, the influence of the pump intensity, pump and signal spatial modulations, and the walk-off effect on the OPCPA output beam quality are presented, together with conversion efficiency and the gain spectrum. The pump modulation is a dominant factor that affects the output beam quality. Comparatively, the influence of signal modulation is insignificant. For a low-energy system with small beam sizes, walk-off effect has to be considered. Pump modulation and walk-off effect lead to asymmetric output beam profile with increased modulation. A special pump modulation type is found to optimize output beam quality and efficiency. For a high-energy system with large beam sizes, the walk-off effect can be neglected, certain back conversion is beneficial to reduce the output modulation. A trade-off must be made between the output beam quality and the conversion efficiency, especially when the pump modulation is large since. A relatively high conversion efficiency and a low output modulation are both achievable by controlling the pump modulation and intensity.

Broadband and high-efficiency vortex beam generator based on a hybrid helix array.

PubMed

Fang, Chaoqun; Wu, Chao; Gong, Zhijie; Zhao, Song; Sun, Anqi; Wei, Zeyong; Li, Hongqiang

2018-04-01

The vortex beam which carries the orbital angular momentum has versatile applications, such as high-resolution imaging, optical communications, and particle manipulation. Generating vortex beams with the Pancharatnam-Berry (PB) phase has drawn considerable attention for its unique spin-to-orbital conversion features. Despite the PB phase being frequency independent, an optical element with broadband high-efficiency circular polarization conversion feature is still needed for the broadband high-efficiency vortex beam generation. In this work, a broadband and high-efficiency vortex beam generator based on the PB phase is built with a hybrid helix array. Such devices can generate vortex beams with arbitrary topological charge. Moreover, vortex beams with opposite topological charge can be generated with an opposite handedness incident beam that propagates backward. The measured efficiency of our device is above 65% for a wide frequency range, with the relative bandwidth of 46.5%.

Comparative thermometric properties of bi-functional Er3+-Yb3+ doped rare earth (RE = Y, Gd and La) molybdates

NASA Astrophysics Data System (ADS)

Sinha, Shriya; Mahata, Manoj Kumar; Kumar, Kaushal

2018-02-01

The molybdate compounds as luminescent medium have received great attention of recent research due to their excellent intrinsic optical properties. Therefore, the investigation on the optical thermometry and nanoheating effect in Er3+-Yb3+ doped molybdates of yttrium (EYYMO), gadolinium (EYGMO) and lanthanum (EYLMO) nanophosphors is reported herein. The temperature dependent fluorescence intensity ratio of green (525 and 548 nm) emission bands of Er3+ ions were analyzed within 300-500 K temperature range to determine the thermal behavior. The comparative temperature sensitivity of the materials has been found to depend on the phonon energy of their own. The thermal sensitivity is higher in the materials with low phonon energy. The intensity ratio of the green emission bands has been found to alter with the laser excitation density, which can be used to estimate the induced temperature in the materials. Furthermore, the photothermal conversion efficiency is calculated in the water dispersed samples and the maximum photothermal conversion efficiency of 49.6% is achieved for EYGMO nanophosphor. Comparative experimental results explore unequal thermal sensing and induced optical heating in the three rare earth molybdates. The optical properties of the green emitting molybdates are interesting for temperature sensing and optical heating applications.

Light Extraction From Solution-Based Processable Electrophosphorescent Organic Light-Emitting Diodes

NASA Astrophysics Data System (ADS)

Krummacher, Benjamin C.; Mathai, Mathew; So, Franky; Choulis, Stelios; Choong, And-En, Vi

2007-06-01

Molecular dye dispersed solution processable blue emitting organic light-emitting devices have been fabricated and the resulting devices exhibit efficiency as high as 25 cd/A. With down-conversion phosphors, white emitting devices have been demonstrated with peak efficiency of 38 cd/A and luminous efficiency of 25 lm/W. The high efficiencies have been a product of proper tuning of carrier transport, optimization of the location of the carrier recombination zone and, hence, microcavity effect, efficient down-conversion from blue to white light, and scattering/isotropic remission due to phosphor particles. An optical model has been developed to investigate all these effects. In contrast to the common misunderstanding that light out-coupling efficiency is about 22% and independent of device architecture, our device data and optical modeling results clearly demonstrated that the light out-coupling efficiency is strongly dependent on the exact location of the recombination zone. Estimating the device internal quantum efficiencies based on external quantum efficiencies without considering the device architecture could lead to erroneous conclusions.

Design considerations for multi component molecular-polymeric nonlinear optical materials

NASA Astrophysics Data System (ADS)

Singer, K. D.; Kuzyk, M. G.; Fang, T.; Holland, W. R.; Cahill, P. A.

1990-08-01

We review our work on multi component polymeric nonlinear optical materials. These materials consist of nonlinear optical molecules incorporated in a polymeric host. A cross-linked triazine polymer incorporating a dicyanovinyl terminated azo dye was found to be relatively stable at 85 deg and possess an electro-optic coefficient of 11pm/V. We have also observed the zero dispersion condition in a new anomalous dispersion dye for phase matched second harmonic generation, and expect efficient conversion to the blue. A squarylium dye, ISQ, has been found to possess a large third order nonlinearity, and may display two-level behavior.

Efficient third harmonic generation of a CW-fibered 1.5 µm laser diode

NASA Astrophysics Data System (ADS)

Philippe, Charles; Chea, Erick; Nishida, Yoshiki; du Burck, Frédéric; Acef, Ouali

2016-10-01

We report on frequency tripling of CW-Telecom laser diode using two cascaded PPLN ridge nonlinear crystals, both used in single-pass configuration. All optical components used for this development are fibered, leading to a very compact and easy to use optical setup. We have generated up to 290 mW optical power in the green range, from 800 mW only of infrared power around 1.54 µm. This result corresponds to an optical conversion efficiency P 3 ω / P ω > 36 %. To our knowledge, this is best value ever demonstrated up today for a CW-third harmonic generation in single-pass configuration. This frequency tripling experimental setup was tested over more than 2 years of continuous operation, without any interruption. The compactness and the reliability of our device make it very suitable as a transportable optical oscillator. In particular, it paves the way for embedded applications thanks to the high level of long-term stability of the optical alignments.

Optical Amplifier Based Space Solar Power

NASA Technical Reports Server (NTRS)

Fork, Richard L.

2001-01-01

The objective was to design a safe optical power beaming system for use in space. Research was focused on identification of strategies and structures that would enable achievement near diffraction limited optical beam quality, highly efficient electrical to optical conversion, and high average power in combination in a single system. Efforts centered on producing high efficiency, low mass of the overall system, low operating temperature, precision pointing and tracking capability, compatibility with useful satellite orbits, component and system reliability, and long component and system life in space. A system based on increasing the power handled by each individual module to an optimum and the number of modules in the complete structure was planned. We were concerned with identifying the most economical and rapid path to commercially viable safe space solar power.

Chip-Scale Architectures for Precise Optical Frequency Synthesis

NASA Astrophysics Data System (ADS)

Yang, Jinghui

Scientists and engineers have investigated various types of stable and accurate optical synthesizers, where mode-locked laser based optical frequency comb synthesizers have been widely investigated. These frequency combs bridge the frequencies from optical domain to microwave domain with orders of magnitude difference, providing a metrological tool for various platforms. The demand for highly robust, scalable, compact and cost-effective femtosecond-laser synthesizers, however, are of great importance for applications in air- or space-borne platforms, where low cost and rugged packaging are particularly required. This has been afforded in the past several years due to breakthroughs in chip-scale nanofabrication, bringing advances in optical frequency combs down to semiconductor chips. These platforms, with significantly enhanced light-matter interaction, provide a fertile sandbox for research rich in nonlinear dynamics, and offer a reliable route towards low-phase noise photonic oscillators, broadband optical frequency synthesizers, miniaturized optical clockwork, and coherent terabit communications. The dissertation explores various types of optical frequency comb synthesizers based on nonlinear microresonators. Firstly, the fundamental mechanism of mode-locking in a high-quality factor microresonator is examined, supported by ultrafast optical characterizations, analytical closed-form solutions and numerical modeling. In the evolution of these frequency microcombs, the key nonlinear dynamical effect governing the comb state coherence is rigorously analyzed. Secondly, a prototype of chip-scale optical frequency synthesizer is demonstrated, with the laser frequency comb stabilized down to instrument-limited 50-mHz RF frequency inaccuracies and 10-16 fractional frequency inaccuracies, near the fundamental limits. Thirdly, a globally stable Turing pattern is achieved and characterized in these nonlinear resonators with high-efficiency conversion, subsequently generating coherent high-power terahertz radiation via plasmonic photomixers. Finally, a new universal modality of frequency combs is discussed, including satellite states, dynamical tunability, and high efficiency conversion towards direct chip-scale optical frequency synthesis at the precision metrology frontiers.

Electrical and optical modeling of poly(3-hexylthiophene):[6,6]-phenyl-C61 butyric acid methyl ester P3HT-PCBM bulk heterojunction solar cells

NASA Astrophysics Data System (ADS)

Brioua, Fathi; Remram, Mohamed; Nechache, Riad; Bourouina, Hicham

2017-11-01

In this work, we investigate a two-dimensional theoretical model for the photon conversion through an integration of the optical and electrical part of multilayer system in a bulk heterojunction solar cell based on poly(3-hexylthiophene) (P3HT)/6,6-phenyl C61-butyric acid methyl ester (PCBM) blend. The optical properties of the studied structure ITO/PEDOT:PSS/P3HT:PCBM/Ca/Al, such as the exciton generation rate and the electrical field distribution, are predicted at vicinity of the active layer and have been used to solve Poisson and continuity, drift-diffusion equations of the electrical model which characterize the electrical behavior of semiconductor device using finite element method (FEM). The electrical parameters such as power conversion efficiency (PCE), open voltage circuit ( V oc), short-circuit current density ( J sc) and fill factor (FF) are extracted from the current-voltage (J-V) characteristics under illumination and in dark conditions. Highest external quantum efficiency (IPCE), up to 60%, is obtained around 520 nm, while a power conversion efficiency (PCE) value of 3.62% is found to be in good agreement with the literature results. Integration of such theoretical approach into technological applications dealing with optoelectrical material performance will rapidly provide to the user accurate data outputs required for efficient validation of proof-of-concepts.

Resonantly pumped high efficiency Ho:YAG laser.

PubMed

Shen, Ying-Jie; Yao, Bao-Quan; Duan, Xiao-Ming; Dai, Tong-Yu; Ju, You-Lun; Wang, Yue-Zhu

2012-11-20

High-efficient CW and Q-switched Ho:YAG lasers resonantly dual-end-pumped by two diode-pumped Tm:YLF lasers at 1908 nm were investigated. A maximum slope efficiency of 74.8% in CW operation as well as a maximum output power of 58.7 W at 83.2 W incident pump power was achieved, which corresponded to an optical-to-optical conversion efficiency of 70.6%. The maximum pulse energy of 2.94 mJ was achieved, with a 31 ns FWHM pulse width and a peak power of approximately 94.7 kW.

Efficient high-power frequency doubling of distributed Bragg reflector tapered laser radiation in a periodically poled MgO-doped lithium niobate planar waveguide.

PubMed

Jedrzejczyk, Daniel; Güther, Reiner; Paschke, Katrin; Jeong, Woo-Jin; Lee, Han-Young; Erbert, Götz

2011-02-01

We report on efficient single-pass, high-power second-harmonic generation in a periodically poled MgO-doped LiNbO3 planar waveguide using a distributed Bragg reflector tapered diode laser as a pump source. A coupling efficiency into the planar waveguide of 73% was realized, and 1.07 W of visible laser light at 532 nm was generated. Corresponding optical and electro-optical conversion efficiencies of 26% and 8.4%, respectively, were achieved. Good agreement between the experimental data and the theoretical predictions was observed.

Ultrafast Plasmonic Control of Second Harmonic Generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.

Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-fieldmore » is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.« less

Ultrafast Plasmonic Control of Second Harmonic Generation

DOE PAGES

Davidson, Roderick B.; Yanchenko, Anna; Ziegler, Jed I.; ...

2016-06-01

Efficient frequency conversion techniques are crucial to the development of plasmonic metasurfaces for information processing and signal modulation. In principle, nanoscale electric-field confinement in nonlinear materials enables higher harmonic conversion efficiencies per unit volume than those attainable in bulk materials. Here we demonstrate efficient second-harmonic generation (SHG) in a serrated nanogap plasmonic geometry that generates steep electric field gradients on a dielectric metasurface. An ultrafast control pulse is used to control plasmon-induced electric fields in a thin-film material with inversion symmetry that, without plasmonic enhancement, does not exhibit an even-order nonlinear optical response. The temporal evolution of the plasmonic near-fieldmore » is characterized with ~100 as resolution using a novel nonlinear interferometric technique. The serrated nanogap is a unique platform in which to investigate optically controlled, plasmonically enhanced harmonic generation in dielectric materials on an ultrafast time scale. Lastly, this metamaterial geometry can also be readily extended to all-optical control of other nonlinear phenomena, such as four-wave mixing and sum- and difference-frequency generation, in a wide variety of dielectric materials.« less

Highly efficient non-degenerate four-wave mixing under dual-mode injection in InP/InAs quantum-dash and quantum-dot lasers at 1.55 μm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sadeev, T., E-mail: tagir@mailbox.tu-berlin.de; Arsenijević, D.; Huang, H.

2015-11-09

This work reports on non-degenerate four-wave mixing under dual-mode injection in metalorganic vapor phase epitaxy grown InP/InAs quantum-dash and quantum dot Fabry-Perot laser operating at 1550 nm. High values of normalized conversion efficiency of −18.6 dB, optical signal-to-noise ratio of 37 dB, and third order optical susceptibility normalized to material gain χ{sup (3)}/g{sub 0} of ∼4 × 10{sup −19} m{sup 3}/V{sup 3} are measured for 1490 μm long quantum-dash lasers. These values are similar to those obtained with distributed-feedback lasers and semiconductor optical amplifiers, which are much more complicated to fabricate. On the other hand, due to the faster gain saturation and enhanced modulation of carriermore » populations, quantum-dot lasers demonstrate 12 dB lower conversion efficiency and 4 times lower χ{sup (3)}/g{sub 0} compared to quantum dash lasers.« less

Phase conversion from hexagonal CuS(y)Se(1-y) to cubic Cu(2-x)S(y)Se(1-y): composition variation, morphology evolution, optical tuning, and solar cell applications.

PubMed

Xu, Jun; Yang, Xia; Yang, Qingdan; Zhang, Wenjun; Lee, Chun-Sing

2014-09-24

In this work, we report a simple and low-temperature approach for the controllable synthesis of ternary Cu-S-Se alloys featuring tunable crystal structures, compositions, morphologies, and optical properties. Hexagonal CuS(y)Se(1-y) nanoplates and face centered cubic (fcc) Cu(2-x)S(y)Se(1-y) single-crystal-like stacked nanoplate assemblies are synthesized, and their phase conversion mechanism is well investigated. It is found that both copper content and chalcogen composition (S/Se atomic ratio) of the Cu-S-Se alloys are tunable during the phase conversion process. Formation of the unique single-crystal-like stacked nanoplate assemblies is resulted from oriented stacking coupled with the Ostwald ripening effect. Remarkably, optical tuning for continuous red shifts of both the band-gap absorption and the near-infrared localized surface plasmon resonance are achieved. Furthermore, the novel Cu-S-Se alloys are utilized for the first time as highly efficient counter electrodes (CEs) in quantum dot sensitized solar cells (QDSSCs), showing outstanding electrocatalytic activity for polysulfide electrolyte regeneration and yielding a 135% enhancement in power conversion efficiency (PCE) as compared to the noble metal Pt counter electrode.

Engineered Quasi-Phase Matching for Nonlinear Quantum Optics in Waveguides

NASA Astrophysics Data System (ADS)

Van Camp, Mackenzie A.

Entanglement is the hallmark of quantum mechanics. Quantum entanglement--putting two or more identical particles into a non-factorable state--has been leveraged for applications ranging from quantum computation and encryption to high-precision metrology. Entanglement is a practical engineering resource and a tool for sidestepping certain limitations of classical measurement and communication. Engineered nonlinear optical waveguides are an enabling technology for generating entangled photon pairs and manipulating the state of single photons. This dissertation reports on: i) frequency conversion of single photons from the mid-infrared to 843nm as a tool for incorporating quantum memories in quantum networks, ii) the design, fabrication, and test of a prototype broadband source of polarization and frequency entangled photons; and iii) a roadmap for further investigations of this source, including applications in quantum interferometry and high-precision optical metrology. The devices presented herein are quasi-phase-matched lithium niobate waveguides. Lithium niobate is a second-order nonlinear optical material and can mediate optical energy conversion to different wavelengths. This nonlinear effect is the basis of both quantum frequency conversion and entangled photon generation, and is enhanced by i) confining light in waveguides to increase conversion efficiency, and ii) quasi-phase matching, a technique for engineering the second-order nonlinear response by locally altering the direction of a material's polarization vector. Waveguides are formed by diffusing titanium into a lithium niobate wafer. Quasi-phase matching is achieved by electric field poling, with multiple stages of process development and optimization to fabricate the delicate structures necessary for broadband entangled photon generation. The results presented herein update and optimize past fabrication techniques, demonstrate novel optical devices, and propose future avenues for device development. Quantum frequency conversion from 1848nm to 843nm is demonstrated for the first time, with >75% single-photon conversion efficiency. A new electric field poling methodology is presented, combining elements from multiple historical techniques with a new fast-feedback control system. This poling technique is used to fabricate the first chirped-and-apodized Type-II quasi-phase-matched structures in titanium-diffused lithium niobate waveguides, culminating in a measured phasematching spectrum that is predominantly Gaussian ( R2 = 0.80), nearly eight times broader than the unchirped spectrum, and agrees well with simulations.

Optical enhancement of a printed organic tandem solar cell using diffractive nanostructures.

PubMed

Mayer, Jan A; Offermans, Ton; Chrapa, Marek; Pfannmöller, Martin; Bals, Sara; Ferrini, Rolando; Nisato, Giovanni

2018-03-19

Solution processable organic tandem solar cells offer a promising approach to achieve cost-effective, lightweight and flexible photovoltaics. In order to further enhance the efficiency of optimized organic tandem cells, diffractive light-management nanostructures were designed for an optimal redistribution of the light as function of both wavelength and propagation angles in both sub-cells. As the fabrication of these optical structures is compatible with roll-to-roll production techniques such as hot-embossing or UV NIL imprinting, they present an optimal cost-effective solution for printed photovoltaics. Tandem cells with power conversion efficiencies of 8-10% were fabricated in the ambient atmosphere by doctor blade coating, selected to approximate the conditions during roll-to-roll manufacturing. Application of the light management structure onto an 8.7% efficient encapsulated tandem cell boosted the conversion efficiency of the cell to 9.5%.

Terahertz generation by difference frequency generation from a compact optical parametric oscillator

NASA Astrophysics Data System (ADS)

Li, Zhongyang; Wang, Silei; Wang, Mengtao; Wang, Weishu

2017-11-01

Terahertz (THz) generation by difference frequency generation (DFG) processes with dual idler waves is theoretically analyzed. The dual idler waves are generated by a compact optical parametric oscillator (OPO) with periodically poled lithium niobate (PPLN). The phase-matching conditions in a same PPLN for the optical parametric oscillation generating signal and idler waves and for the DFG generating THz waves can be simultaneously satisfied by selecting the poling period of PPLN. Moreover, 3-order cascaded DFG processes generating THz waves can be realized in the same PPLN. To take an example of 8.341 THz which locates in the vicinity of polariton resonances, THz intensities and quantum conversion efficiencies are calculated. Compared with non-cascaded DFG processes, THz intensities of 8.341 THz in 3-order cascaded DFG processes increase to 2.57 times. When the pump intensity equals to 20 MW/mm2, the quantum conversion efficiency of 106% in 3-order cascaded DFG processes can be realized, which exceeds the Manley-Rowe limit.

Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion.

PubMed

Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

2011-01-01

Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-μm-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s(-1).

Travelling-wave resonant four-wave mixing breaks the limits of cavity-enhanced all-optical wavelength conversion

PubMed Central

Morichetti, Francesco; Canciamilla, Antonio; Ferrari, Carlo; Samarelli, Antonio; Sorel, Marc; Melloni, Andrea

2011-01-01

Wave mixing inside optical resonators, while experiencing a large enhancement of the nonlinear interaction efficiency, suffers from strong bandwidth constraints, preventing its practical exploitation for processing broad-band signals. Here we show that such limits are overcome by the new concept of travelling-wave resonant four-wave mixing (FWM). This approach combines the efficiency enhancement provided by resonant propagation with a wide-band conversion process. Compared with conventional FWM in bare waveguides, it exhibits higher robustness against chromatic dispersion and propagation loss, while preserving transparency to modulation formats. Travelling-wave resonant FWM has been demonstrated in silicon-coupled ring resonators and was exploited to realize a 630-μm-long wavelength converter operating over a wavelength range wider than 60 nm and with 28-dB gain with respect to a bare waveguide of the same physical length. Full compatibility of the travelling-wave resonant FWM with optical signal processing applications has been demonstrated through signal retiming and reshaping at 10 Gb s−1 PMID:21540838

All-Solid-State UV Transmitter Development for Ozone Sensing Applications

NASA Technical Reports Server (NTRS)

Prasad, Narasimha S.; Singh, Upendra N.; Armstrong, Darrell Jr.

2009-01-01

In this paper, recent progress made in the development of an all-solid-state UV transmitter suitable for ozone sensing applications from space based platforms is discussed. A nonlinear optics based UV setup based on Rotated Image Singly Resonant Twisted Rectangle (RISTRA) optical parametric oscillator (OPO) module was effectively coupled to a diode pumped, single longitudinal mode, conductively cooled, short-pulsed, high-energy Nd:YAG laser operating at 1064 nm with 50 Hz PRF. An estimated 10 mJ/pulse with 10% conversion efficiency at 320 nm has been demonstrated limited only by the pump pulse spatial profile. The current arrangement has the potential for obtaining greater than 200 mJ/pulse. Previously, using a flash-lamp pumped Nd:YAG laser with round, top-hat profile, up to 24% IR-UV conversion efficiency was achieved with the same UV module. Efforts are underway to increase the IR-UV conversion efficiency of the all solid-state setup by modifying the pump laser spatial profile along with incorporating improved OPO crystals.

Enhancement of photovoltaic cell performance using periodic triangular gratings

NASA Astrophysics Data System (ADS)

Bordatchev, Evgueni; Tauhiduzzaman, Mohammed; Dey, Rajat

2014-01-01

The solar energy industry strives to produce more efficient and yet cost effective solar panels each consisting of an array of photovoltaic (PV) cells. The goal of this study was to enhance the performance of PV cells through increasing the cells' optical efficiency defined as a percentage of surface incident light that reaches the PV material. This was achieved through the reduction of waveguide decoupling loss and Fresnel reflection losses by integrating specific nonimaging micro-optical structures on the top surface of existing PV cells. Due to this integration, optical efficiency and performance were increased through the enhancement of light trapping, light guiding, and in-coupling functionalities. Periodic triangular gratings (PTGs) were designed, nonsequentially modeled, optimized, and fabricated in polydimethylsiloxane as proposed micro-optical structures. Then the performance of PV cells with and without integrated PTGs was evaluated and compared. Initial optical simulation results show that an original PV cell (without PTG) exhibits an average optical efficiency of 32.7% over a range of incident light angles between 15 and 90 deg. Integration of the PTG allows the capture of incoming sunlight by total internal reflection (TIR), whence it is reflected back onto the PV cell for multiple consecutive chances for absorption and PV conversion. Geometry of the PTG was optimized with respect to an angle of light incidence of {15, 30, 45, 60, 75, 90} deg. Optical efficiency of the geometrically optimized PTGs was then analyzed under the same set of incident light angles and a maximum optical efficiency of 54.1% was observed for a PV cell with integrated PTG optimized at 90 deg. This is a 53.3% relative improvement in optical performance when compared to an original PV cell. Functional PTG prototypes were then fabricated with optical surface quality (below 10 nm Ra) and integrated with PV cells demonstrating an increase in maximum power by 1.08 mW/cm (7.6% improvement in PV performance) and in short circuit current by 2.39 mA/cm (6.4% improvement).

Cascaded second-order processes for the efficient generation of narrowband terahertz radiation

NASA Astrophysics Data System (ADS)

Cirmi, Giovanni; Hemmer, Michael; Ravi, Koustuban; Reichert, Fabian; Zapata, Luis E.; Calendron, Anne-Laure; Çankaya, Hüseyin; Ahr, Frederike; Mücke, Oliver D.; Matlis, Nicholas H.; Kärtner, Franz X.

2017-02-01

The generation of high-energy narrowband terahertz radiation has gained heightened importance in recent years due to its potentially transformative impact on spectroscopy, high-resolution radar and more recently electron acceleration. Among various applications, such terahertz radiation is particularly important for table-top free electron lasers, which are at the moment a subject of extensive research. Second-order nonlinear optical methods are among the most promising techniques to achieve the required coherent radiation with energy > 10 mJ, peak field > 100 MV m-1, and frequency between 0.1 and 1 THz. However, they are conventionally thought to suffer from low efficiencies < ˜10-3, due to the high ratio between optical and terahertz photon energies, in what is known as the Manley-Rowe limitation. In this paper, we review the current second-order nonlinear optical methods for the generation of narrowband terahertz radiation. We explain how to employ spectral cascading to increase the efficiency beyond the Manley-Rowe limit and describe the first experimental results in the direction of a terahertz-cascaded optical parametric amplifier, a novel technique which promises to fully exploit spectral cascading to generate narrowband terahertz radiation with few percent optical-to-terahertz conversion efficiency.

Chaos-assisted broadband momentum transformation in optical microresonators.

PubMed

Jiang, Xuefeng; Shao, Linbo; Zhang, Shu-Xin; Yi, Xu; Wiersig, Jan; Wang, Li; Gong, Qihuang; Lončar, Marko; Yang, Lan; Xiao, Yun-Feng

2017-10-20

The law of momentum conservation rules out many desired processes in optical microresonators. We report broadband momentum transformations of light in asymmetric whispering gallery microresonators. Assisted by chaotic motions, broadband light can travel between optical modes with different angular momenta within a few picoseconds. Efficient coupling from visible to near-infrared bands is demonstrated between a nanowaveguide and whispering gallery modes with quality factors exceeding 10 million. The broadband momentum transformation enhances the device conversion efficiency of the third-harmonic generation by greater than three orders of magnitude over the conventional evanescent-wave coupling. The observed broadband and fast momentum transformation could promote applications such as multicolor lasers, broadband memories, and multiwavelength optical networks. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

Development of Optical Parametric Amplifier for Lidar Measurements of Trace Gases on Earth and Mars

NASA Technical Reports Server (NTRS)

Numata, Kenji; Riris, Haris; Li, Steve; Wu, Stewart; Kawa, Stephen R.; Krainak, Michael; Abshire, James

2011-01-01

Trace gases in planetary atmospheres offer important clues as to the origins of the planet's hydrology, geology. atmosphere. and potential for biology. Wc report on the development effort of a nanosecond-pulsed optical parametric amplifier (OPA) for remote trace gas measurements for Mars and Earth. The OP A output light is single frequency with high spectral purity and is widely tunable both at 1600 nm and 3300 nm with an optical-optical conversion efficiency of approximately 40%. We demonstrated open-path atmospheric measurements ofCH4 (3291 nm and 1651 nm). CO2 (1573 nm), H20 (1652 nm) with this laser source.

High-speed low-power photonic transistor devices based on optically-controlled gain or absorption to affect optical interference.

PubMed

Huang, Yingyan; Ho, Seng-Tiong

2008-10-13

We show that a photonic transistor device can be realized via the manipulation of optical interference by optically controlled gain or absorption in novel ways, resulting in efficient transistor signal gain and switching action. Exemplary devices illustrate two complementary device types with high operating speed, microm size, microW switching power, and switching gain. They can act in tandem to provide a wide variety of operations including wavelength conversion, pulse regeneration, and logical operations. These devices could have a Transistor Figure-of-Merits >10(5) times higher than current chi((3)) approaches and are highly attractive.

Third harmonic from air breakdown plasma induced by nanosecond laser pulses

NASA Astrophysics Data System (ADS)

Stafe, M.; Negutu, C.; Puscas, N. N.

2018-06-01

Harmonic generation is a nonlinear optical effect consisting in frequency up-conversion of intense laser radiation when phase-matching conditions are fulfilled. Here, we study the mechanisms involved in the third harmonic (TH) generation process, the conversion efficiency, and the properties of TH radiation generated in air by focusing infrared linearly polarized nanosecond laser pulses at intensities of the order of TW/cm2. By analyzing the emission from the air breakdown plasma, we demonstrate that filamentary breakdown plasma containing molecular nitrogen ions acts as an optical nonlinear medium enabling generation of TH radiation in the axial direction. The data reveal important properties of the TH radiation: maximum conversion efficiency of 0.04%, sinc2 dependence of the TH intensity on the square root of the pump intensity, and three times smaller divergence and pulse duration of TH as compared to the pump radiation.

Ultrabroadband phased-array radio frequency (RF) receivers based on optical techniques

NASA Astrophysics Data System (ADS)

Overmiller, Brock M.; Schuetz, Christopher A.; Schneider, Garrett; Murakowski, Janusz; Prather, Dennis W.

2014-03-01

Military operations require the ability to locate and identify electronic emissions in the battlefield environment. However, recent developments in radio detection and ranging (RADAR) and communications technology are making it harder to effectively identify such emissions. Phased array systems aid in discriminating emitters in the scene by virtue of their relatively high-gain beam steering and nulling capabilities. For the purpose of locating emitters, we present an approach realize a broadband receiver based on optical processing techniques applied to the response of detectors in conformal antenna arrays. This approach utilizes photonic techniques that enable us to capture, route, and process the incoming signals. Optical modulators convert the incoming signals up to and exceeding 110 GHz with appreciable conversion efficiency and route these signals via fiber optics to a central processing location. This central processor consists of a closed loop phase control system which compensates for phase fluctuations induced on the fibers due to thermal or acoustic vibrations as well as an optical heterodyne approach for signal conversion down to baseband. Our optical heterodyne approach uses injection-locked paired optical sources to perform heterodyne downconversion/frequency identification of the detected emission. Preliminary geolocation and frequency identification testing of electronic emissions has been performed demonstrating the capabilities of our RF receiver.

Optical rectification using geometrical field enhancement in gold nano-arrays

NASA Astrophysics Data System (ADS)

Piltan, S.; Sievenpiper, D.

2017-11-01

Conversion of photons to electrical energy has a wide variety of applications including imaging, solar energy harvesting, and IR detection. A rectenna device consists of an antenna in addition to a rectifying element to absorb the incident radiation within a certain frequency range. We designed, fabricated, and measured an optical rectifier taking advantage of asymmetrical field enhancement for forward and reverse currents due to geometrical constraints. The gold nano-structures as well as the geometrical parameters offer enhanced light-matter interaction at 382 THz. Using the Taylor expansion of the time-dependent current as a function of the external bias and oscillating optical excitation, we obtained responsivities close to quantum limit of operation. This geometrical approach can offer an efficient, broadband, and scalable solution for energy conversion and detection in the future.

Status and summary of laser energy conversion. [for space power transmission systems

NASA Technical Reports Server (NTRS)

Lee, G.

1978-01-01

This paper presents a survey of the status of laser energy converters. Since the inception of these devices in the early 1970's, significant advances have been made in understanding the basic conversion processes. Numerous theoretical and experimental studies have indicated that laser energy can be converted at wavelengths from the ultraviolet to the far-infrared. These converters can be classified into five general categories: photovoltaics, heat engines, thermoelectronic, optical diode, and photochemical. The conversion can be directly into electricity (such as the photovoltaic, thermoelectronic, and optical diode) or it can go through an intermediate stage of conversion to mechanical energy, as in the heat engines. The photochemical converters result in storable energy such as hydrogen. Projected conversion efficiencies range from about 30% for the photochemical to nearly 75% for the heat engines.

A High-Power Broadband Terahertz Source Enabled by Three-Dimensional Light Confinement in a Plasmonic Nanocavity.

PubMed

Yardimci, Nezih Tolga; Cakmakyapan, Semih; Hemmati, Soroosh; Jarrahi, Mona

2017-06-23

The scope and potential uses of time-domain terahertz imaging and spectroscopy are mainly limited by the low optical-to-terahertz conversion efficiency of photoconductive terahertz sources. State-of-the-art photoconductive sources utilize short-carrier-lifetime semiconductors to recombine carriers that cannot contribute to efficient terahertz generation and cause additional thermal dissipation. Here, we present a novel photoconductive terahertz source that offers a significantly higher efficiency compared with terahertz sources fabricated on short-carrier-lifetime substrates. The key innovative feature of this source is the tight three-dimensional confinement of the optical pump beam around the terahertz nanoantennas that are used as radiating elements. This is achieved by means of a nanocavity formed by plasmonic structures and a distributed Bragg reflector. Consequently, almost all of the photo-generated carriers can be routed to the terahertz nanoantennas within a sub-picosecond time-scale. This results in a very strong, ultrafast current that drives the nanoantennas to produce broadband terahertz radiation. We experimentally demonstrate that this terahertz source can generate 4 mW pulsed terahertz radiation under an optical pump power of 720 mW over the 0.1-4 THz frequency range. This is the highest reported power level for terahertz radiation from a photoconductive terahertz source, representing more than an order of magnitude of enhancement in the optical-to-terahertz conversion efficiency compared with state-of-the-art photoconductive terahertz sources fabricated on short-carrier-lifetime substrates.

A High-Power Broadband Terahertz Source Enabled by Three-Dimensional Light Confinement in a Plasmonic Nanocavity

DOE PAGES

Yardimci, Nezih Tolga; Cakmakyapan, Semih; Hemmati, Soroosh; ...

2017-06-23

The scope and potential uses of time-domain terahertz imaging and spectroscopy are mainly limited by the low optical-to-terahertz conversion efficiency of photoconductive terahertz sources. State-of-theart photoconductive sources utilize short-carrier-lifetime semiconductors to recombine carriers that cannot contribute to efficient terahertz generation and cause additional thermal dissipation. Here, we present a novel photoconductive terahertz source that offers a significantly higher efficiency compared with terahertz sources fabricated on short-carrier-lifetime substrates. The key innovative feature of this source is the tight three-dimensional confinement of the optical pump beam around the terahertz nanoantennas that are used as radiating elements. This is achieved by means ofmore » a nanocavity formed by plasmonic structures and a distributed Bragg reflector. Consequently, almost all of the photo-generated carriers can be routed to the terahertz nanoantennas within a sub-picosecond time-scale. This results in a very strong, ultrafast current that drives the nanoantennas to produce broadband terahertz radiation. We experimentally demonstrate that this terahertz source can generate 4 mW pulsed terahertz radiation under an optical pump power of 720 mW over the 0.1–4 THz frequency range. This is the highest reported power level for terahertz radiation from a photoconductive terahertz source, representing more than an order of magnitude of enhancement in the optical-to-terahertz conversion efficiency compared with state-of-the-art photoconductive terahertz sources fabricated on shortcarrier- lifetime substrates.« less

All-optical phase discrimination using SOA.

PubMed

Power, Mark J; Webb, Roderick P; Manning, Robert J

2013-11-04

We describe the first experimental demonstration of a novel all-optical phase discrimination technique, which can separate the two orthogonal phase components of a signal onto different frequencies. This method exploits nonlinear mixing in a semiconductor optical amplifier (SOA) to separate a 10.65 Gbaud QPSK signal into two 10.65 Gb/s BPSK signals which are then demodulated using a delay interferometer (DI). Eye diagrams and spectral measurements verify correct operation and a conversion efficiency greater than 9 dB is observed on both output BPSK channels when compared with the input QPSK signal.

Tunable error-free optical frequency conversion of a 4ps optical short pulse over 25 nm by four-wave mixing in a polarisation-maintaining optical fibre

NASA Astrophysics Data System (ADS)

Morioka, T.; Kawanishi, S.; Saruwatari, M.

1994-05-01

Error-free, tunable optical frequency conversion of a transform-limited 4.0 ps optical pulse signalis demonstrated at 6.3 Gbit/s using four-wave mixing in a polarization-maintaining optical fibre. The process generates 4.0-4.6 ps pulses over a 25nm range with time-bandwidth products of 0.31-0.43 and conversion power penalties of less than 1.5 dB.

Efficient semiconductor multicycle terahertz pulse source

NASA Astrophysics Data System (ADS)

Nugraha, P. S.; Krizsán, G.; Polónyi, Gy; Mechler, M. I.; Hebling, J.; Tóth, Gy; Fülöp, J. A.

2018-05-01

Multicycle THz pulse generation by optical rectification in GaP semiconductor nonlinear material is investigated by numerical simulations. It is shown that GaP can be an efficient and versatile source with up to about 8% conversion efficiency and a tuning range from 0.1 THz to about 7 THz. Contact-grating technology for pulse-front tilt can ensure an excellent focusability and scaling the THz pulse energy beyond 1 mJ. Shapeable infrared pump pulses with a constant intensity-modulation period can be delivered for example by a flexible and efficient dual-chirped optical parametric amplifier. Potential applications include linear and nonlinear THz spectroscopy and THz-driven acceleration of electrons.

High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling

PubMed Central

Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

2017-01-01

An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs. PMID:28211516

High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling

NASA Astrophysics Data System (ADS)

Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

2017-02-01

An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs.

High efficient OLED displays prepared with the air-gapped bridges on quantum dot patterns for optical recycling.

PubMed

Kim, Hyo-Jun; Shin, Min-Ho; Kim, Joo-Suc; Kim, Se-Eun; Kim, Young-Joo

2017-02-17

An optically efficient structure was proposed and fabricated to realize high brightness organic light emitting diode (OLED) displays based on a white OLED prepared with the air-gapped bridges on the quantum dot (QD) patterns. Compared with a conventional white OLED display, in our experiments, the optical intensity of the proposed OLED display shows the enhancement of 58.2% in the red color and 16.8% in the green color after applying the air-gapped bridge structure on QD patterns of 20 wt% concentration. This enhancement comes from the two facts that the QD patterns downconvert unnecessary blue or blue/green light to the required green or red light and the air-gapped bridges increase the color conversion efficiency of QDs by optical recycling using total internal reflection (TIR) at the interface. In addition, the color gamut of the proposed OLED display increases from 65.5 to 75.9% (NTSC x, y ratio) due to the narrow emission spectra of QDs.

Generation of tunable high-repetition rate middle infrared transform-limited picosecond pulses

NASA Astrophysics Data System (ADS)

Yakovlev, Vladislav V.; Ballmann, Charles W.; Petrov, Georgi I.

2018-03-01

Tunable middle infrared generation is now affordable through optical parametric generation and amplification in a number of infrared nonlinear crystals. However, maintaining narrow bandwidth, while achieving high conversion efficiency, remains a challenge. In this report, we propose and experimentally demonstrate a relatively simple setup, which utilizes a single-wavelength diode laser as a seed laser for an optical parametric amplifier.

Optical Frequency Optimization of a High Intensity Laser Power Beaming System Utilizing VMJ Photovoltaic Cells

NASA Technical Reports Server (NTRS)

Raible, Daniel E.; Dinca, Dragos; Nayfeh, Taysir H.

2012-01-01

An effective form of wireless power transmission (WPT) has been developed to enable extended mission durations, increased coverage and added capabilities for both space and terrestrial applications that may benefit from optically delivered electrical energy. The high intensity laser power beaming (HILPB) system enables long range optical 'refueling" of electric platforms such as micro unmanned aerial vehicles (MUAV), airships, robotic exploration missions and spacecraft platforms. To further advance the HILPB technology, the focus of this investigation is to determine the optimal laser wavelength to be used with the HILPB receiver, which utilizes vertical multi-junction (VMJ) photovoltaic cells. Frequency optimization of the laser system is necessary in order to maximize the conversion efficiency at continuous high intensities, and thus increase the delivered power density of the HILPB system. Initial spectral characterizations of the device performed at the NASA Glenn Research Center (GRC) indicate the approximate range of peak optical-to-electrical conversion efficiencies, but these data sets represent transient conditions under lower levels of illumination. Extending these results to high levels of steady state illumination, with attention given to the compatibility of available commercial off-the-shelf semiconductor laser sources and atmospheric transmission constraints is the primary focus of this paper. Experimental hardware results utilizing high power continuous wave (CW) semiconductor lasers at four different operational frequencies near the indicated band gap of the photovoltaic VMJ cells are presented and discussed. In addition, the highest receiver power density achieved to date is demonstrated using a single photovoltaic VMJ cell, which provided an exceptionally high electrical output of 13.6 W/sq cm at an optical-to-electrical conversion efficiency of 24 percent. These results are very promising and scalable, as a potential 1.0 sq m HILPB receiver of similar construction would be able to generate 136 kW of electrical power under similar conditions.

High coupling efficiency of foam spherical hohlraum driven by 2ω laser light

NASA Astrophysics Data System (ADS)

Chen, Yao-Hua; Lan, Ke; Zheng, Wanguo; Campbell, E. M.

2018-02-01

The majority of solid state laser facilities built for laser fusion research irradiate targets with third harmonic light (0.35 μm) up-converted from the fundamental Nd wavelength at 1.05 μm. The motivation for this choice of wavelength is improved laser-plasma coupling. Significant disadvantages to this choice of wavelength are the reduced damage threshold of optical components and the efficiency of energy conversion to third harmonic light. Both these issues are significantly improved if second harmonic (0.53 μm) radiation is used, but theory and experiments have shown lower optical to x-ray energy conversion efficiency and increased levels of laser-plasma instabilities, resulting in reduced laser-target coupling. In this letter, we propose to use a 0.53 μm laser for the laser ignition facilities and use a low density foam wall to increase the coupling efficiency from the laser to the capsule and present two-dimensional radiation-hydrodynamic simulations of 0.53 μm laser light irradiating an octahedral-spherical hohlraum with a low density foam wall. The simulations show that the reduced optical depth of the foam wall leads to an increased laser-light conversion into thermal x-rays and about 10% higher radiation flux on the capsule than that achieved with 0.35 μm light irradiating a solid density wall commonly used in laser indirect drive fusion research. The details of the simulations and their implications and suggestions for wavelength scaling coupled with innovative hohlraum designs will be discussed.

Semi-automatic engineering and tailoring of high-efficiency Bragg-reflection waveguide samples for quantum photonic applications

NASA Astrophysics Data System (ADS)

Pressl, B.; Laiho, K.; Chen, H.; Günthner, T.; Schlager, A.; Auchter, S.; Suchomel, H.; Kamp, M.; Höfling, S.; Schneider, C.; Weihs, G.

2018-04-01

Semiconductor alloys of aluminum gallium arsenide (AlGaAs) exhibit strong second-order optical nonlinearities. This makes them prime candidates for the integration of devices for classical nonlinear optical frequency conversion or photon-pair production, for example, through the parametric down-conversion (PDC) process. Within this material system, Bragg-reflection waveguides (BRW) are a promising platform, but the specifics of the fabrication process and the peculiar optical properties of the alloys require careful engineering. Previously, BRW samples have been mostly derived analytically from design equations using a fixed set of aluminum concentrations. This approach limits the variety and flexibility of the device design. Here, we present a comprehensive guide to the design and analysis of advanced BRW samples and show how to automatize these tasks. Then, nonlinear optimization techniques are employed to tailor the BRW epitaxial structure towards a specific design goal. As a demonstration of our approach, we search for the optimal effective nonlinearity and mode overlap which indicate an improved conversion efficiency or PDC pair production rate. However, the methodology itself is much more versatile as any parameter related to the optical properties of the waveguide, for example the phasematching wavelength or modal dispersion, may be incorporated as design goals. Further, we use the developed tools to gain a reliable insight in the fabrication tolerances and challenges of real-world sample imperfections. One such example is the common thickness gradient along the wafer, which strongly influences the photon-pair rate and spectral properties of the PDC process. Detailed models and a better understanding of the optical properties of a realistic BRW structure are not only useful for investigating current samples, but also provide important feedback for the design and fabrication of potential future turn-key devices.

Wood-Graphene Oxide Composite for Highly Efficient Solar Steam Generation and Desalination.

PubMed

Liu, Keng-Ku; Jiang, Qisheng; Tadepalli, Sirimuvva; Raliya, Ramesh; Biswas, Pratim; Naik, Rajesh R; Singamaneni, Srikanth

2017-03-01

Solar steam generation is a highly promising technology for harvesting solar energy, desalination and water purification. We introduce a novel bilayered structure composed of wood and graphene oxide (GO) for highly efficient solar steam generation. The GO layer deposited on the microporous wood provides broad optical absorption and high photothermal conversion resulting in rapid increase in the temperature at the liquid surface. On the other hand, wood serves as a thermal insulator to confine the photothermal heat to the evaporative surface and to facilitate the efficient transport of water from the bulk to the photothermally active space. Owing to the tailored bilayer structure and the optimal thermo-optical properties of the individual components, the wood-GO composite structure exhibited a solar thermal efficiency of ∼83% under simulated solar excitation at a power density of 12 kW/m 2 . The novel composite structure demonstrated here is highly scalable and cost-efficient, making it an attractive material for various applications involving large light absorption, photothermal conversion and heat localization.

Heralding efficiency and correlated-mode coupling of near-IR fiber-coupled photon pairs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixon, P. Ben; Rosenberg, Danna; Stelmakh, Veronika

We report on a systematic experimental study of heralding efficiency and generation rate of telecom-band infrared photon pairs generated by spontaneous parametric down-conversion and coupled to single mode optical fibers. We define the correlated-mode coupling efficiency--an inherent source efficiency--and explain its relation to heralding efficiency. For our experiment, we developed a reconfigurable computer controlled pump-beam and collection-mode optical apparatus which we used to measure the generation rate and correlated-mode coupling efficiency. The use of low-noise, high-efficiency superconducting-nanowire single-photon-detectors in this setup allowed us to explore focus configurations with low overall photon flux. The measured data agree well with theory andmore » we demonstrated a correlated-mode coupling efficiency of 97%±2%, which is the highest efficiency yet achieved for this type of system. These results confirm theoretical treatments and demonstrate that very high overall heralding efficiencies can, in principle, be achieved in quantum optical systems. We expect that these results and techniques will be widely incorporated into future systems that require, or benefit from, a high heralding efficiency.« less

Heralding efficiency and correlated-mode coupling of near-IR fiber-coupled photon pairs

DOE PAGES

Dixon, P. Ben; Rosenberg, Danna; Stelmakh, Veronika; ...

2014-10-06

We report on a systematic experimental study of heralding efficiency and generation rate of telecom-band infrared photon pairs generated by spontaneous parametric down-conversion and coupled to single mode optical fibers. We define the correlated-mode coupling efficiency--an inherent source efficiency--and explain its relation to heralding efficiency. For our experiment, we developed a reconfigurable computer controlled pump-beam and collection-mode optical apparatus which we used to measure the generation rate and correlated-mode coupling efficiency. The use of low-noise, high-efficiency superconducting-nanowire single-photon-detectors in this setup allowed us to explore focus configurations with low overall photon flux. The measured data agree well with theory andmore » we demonstrated a correlated-mode coupling efficiency of 97%±2%, which is the highest efficiency yet achieved for this type of system. These results confirm theoretical treatments and demonstrate that very high overall heralding efficiencies can, in principle, be achieved in quantum optical systems. We expect that these results and techniques will be widely incorporated into future systems that require, or benefit from, a high heralding efficiency.« less

Analysis of adjusting effects of mounting force on frequency conversion of mounted nonlinear optics.

PubMed

Su, Ruifeng; Liu, Haitao; Liang, Yingchun; Lu, Lihua

2014-01-10

Motivated by the need to increase the second harmonic generation (SHG) efficiency of nonlinear optics with large apertures, a novel mounting configuration with active adjusting function on the SHG efficiency is proposed and mechanically and optically studied. The adjusting effects of the mounting force on the distortion and stress are analyzed by the finite element methods (FEM), as well as the contribution of the distortion and stress to the change in phase mismatch, and the SHG efficiency are theoretically stated. Further on, the SHG efficiency is calculated as a function of the mounting force. The changing trends of the distortion, stress, and the SHG efficiency with the varying mounting force are obtained, and the optimal ones are figured out. Moreover, the mechanism of the occurrence of the optimal values is studied and the adjusting strategy is put forward. Numerical results show the robust adjustment of the mounting force, as well as the effectiveness of the mounting configuration, in increasing the SHG efficiency.

Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

DOEpatents

Brown, Edward J.; Baldasaro, Paul F.; Dziendziel, Randolph J.

1997-01-01

A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength .lambda..sub.IF approximately equal to the bandgap wavelength .lambda..sub.g of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5.lambda..sub.IF to .lambda..sub.IF and reflect from .lambda..sub.IF to about 2.lambda..sub.IF ; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5.lambda..sub.IF.

High-power diode-side-pumped rod Tm:YAG laser at 2.07 μm.

PubMed

Wang, Caili; Niu, Yanxiong; Du, Shifeng; Zhang, Chao; Wang, Zhichao; Li, Fangqin; Xu, Jialin; Bo, Yong; Peng, Qinjun; Cui, Dafu; Zhang, Jingyuan; Xu, Zuyan

2013-11-01

We report a high-power diode-laser (LD) side-pumped rod Tm:YAG laser of around 2 μm. The laser was water-cooled at 8°C and yielded a maximum output power of 267 W at 2.07 μm, which is the highest output power for an all solid-state cw 2.07 μm rod Tm:YAG laser reported as far as we know. The corresponding optical-optical conversion efficiency was 20.7%, and the slope efficiency was about 29.8%, respectively.

Improvements to tapered semiconductor MOPA laser design and testing

NASA Astrophysics Data System (ADS)

Beil, James A.; Shimomoto, Lisa; Swertfeger, Rebecca B.; Misak, Stephen M.; Campbell, Jenna; Thomas, Jeremy; Renner, Daniel; Mashanovitch, Milan; Leisher, Paul O.; Liptak, Richard W.

2018-02-01

This paper expands on previous work in the field of high power tapered semiconductor amplifiers and integrated master oscillator power amplifier (MOPA) devices. The devices are designed for watt-class power output and single-mode operation for free-space optical communication. This paper reports on improvements to the fabrication of these devices resulting in doubled electrical-to-optical efficiency, improved thermal properties, and improved spectral properties. A newly manufactured device yielded a peak power output of 375 mW continuous-wave (CW) at 3000 mA of current to the power amplifier and 300 mA of current to the master oscillator. This device had a peak power conversion efficiency of 11.6% at 15° C, compared to the previous device, which yielded a peak power conversion efficiency of only 5.0% at 15° C. The new device also exhibited excellent thermal and spectral properties, with minimal redshift up to 3 A CW on the power amplifier. The new device shows great improvement upon the excessive self-heating and resultant redshift of the previous device. Such spectral improvements are desirable for free-space optical communications, as variation in wavelength can degrade signal quality depending on the detectors being used and the medium of propagation.

Diode-side-pumped continuous wave Nd³⁺ : YVO₄ self-Raman laser at 1176 nm.

PubMed

Kores, Cristine Calil; Jakutis-Neto, Jonas; Geskus, Dimitri; Pask, Helen M; Wetter, Niklaus U

2015-08-01

Here we report, to the best of our knowledge, the first diode-side-pumped continuous wave (cw) Nd3+:YVO4 self-Raman laser operating at 1176 nm. The compact cavity design is based on the total internal reflection of the laser beam at the pumped side of the Nd3+:YVO4 crystal. Configurations with a single bounce and a double bounce of the laser beam at the pumped faced have been characterized, providing a quasi-cw peak output power of more than 8 W (multimode) with an optical conversion efficiency of 11.5% and 3.7 W (TEM00) having an optical conversion efficiency of 5.4%, respectively. Cw output power of 1.8 W has been demonstrated.

Digital optical conversion module

DOEpatents

Kotter, D.K.; Rankin, R.A.

1988-07-19

A digital optical conversion module used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer. 2 figs.

Digital optical conversion module

DOEpatents

Kotter, Dale K.; Rankin, Richard A.

1991-02-26

A digital optical conversion module used to convert an analog signal to a computer compatible digital signal including a voltage-to-frequency converter, frequency offset response circuitry, and an electrical-to-optical converter. Also used in conjunction with the digital optical conversion module is an optical link and an interface at the computer for converting the optical signal back to an electrical signal. Suitable for use in hostile environments having high levels of electromagnetic interference, the conversion module retains high resolution of the analog signal while eliminating the potential for errors due to noise and interference. The module can be used to link analog output scientific equipment such as an electrometer used with a mass spectrometer to a computer.

Magneto-Electric Conversion of Optical Energy to Electricity

DTIC Science & Technology

2015-07-06

thermodynamic limitations. The heat load accompanying magneto-electric rectification was theorized to be negligible, since the conversion process involves a...circles) and cross-polarized (filled circles) quasi-elastic light-scattering in Gadolinium Gallium Garnet (GGG). Right: Same data as on the left...of inertia and crystals achieved magnetic saturation at the lowest intensities. 4. Efficiency Limit – Thermodynamic limit of energy conversion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, H.; Schires, K.; Grillot, F.

Non-degenerate four-wave mixing in an InAs/InP quantum dot Fabry–Perot laser is investigated with an optical injection-locking scheme. Wavelength conversion is obtained for frequency detunings ranging from +2.5 THz to −3.5 THz. The normalized conversion efficiency is maintained above −40 dB between −1.5 and +0.5 THz with an optical signal-to-noise ratio above 20 dB and a maximal third-order nonlinear susceptibility normalized to material gain of 2 × 10{sup −19} m{sup 3}/V{sup 2}. In addition, we show that injection-locking at different positions in the gain spectrum has an impact on the nonlinear conversion process and the symmetry between up- and down- converted signals.

Plasmon-enhanced solar energy conversion in organic bulk heterojunction photovoltaics

NASA Astrophysics Data System (ADS)

Morfa, Anthony J.; Rowlen, Kathy L.; Reilly, Thomas H.; Romero, Manuel J.; van de Lagemaat, Jao

2008-01-01

Plasmon-active silver nanoparticle layers were included in solution-processed bulk-heterojunction solar cells. Nanoparticle layers were fabricated using vapor-phase deposition on indium tin oxide electrodes. Owing to the increase in optical electrical field inside the photoactive layer, the inclusion of such particle films lead to increased optical absorption and consequently increased photoconversion at solar-conversion relevant wavelengths. The resulting solar energy conversion efficiency for a bulk heterojunction photovoltaic device of poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester was found to increase from 1.3%±0.2% to 2.2%±0.1% for devices employing thin plasmon-active layers. Based on six measurements, the improvement factor of 1.7 was demonstrated to be statistically significant.

Plasmon-mediated Energy Conversion in Metal Nanoparticle-doped Hybrid Nanomaterials

NASA Astrophysics Data System (ADS)

Dunklin, Jeremy R.

Climate change and population growth demand long-term solutions for clean water and energy. Plasmon-active nanomaterials offer a promising route towards improved energetics for efficient chemical separation and light harvesting schemes. Two material platforms featuring highly absorptive plasmonic gold nanoparticles (AuNPs) are advanced herein to maximize photon conversion into thermal or electronic energy. Optical extinction, attributable to diffraction-induced internal reflection, was enhanced up to 1.5-fold in three-dimensional polymer films containing AuNPs at interparticle separations approaching the resonant wavelength. Comprehensive methods developed to characterize heat dissipation following plasmonic absorption was extended beyond conventional optical and heat transfer descriptions, where good agreement was obtained between measured and estimated thermal profiles for AuNP-polymer dispersions. Concurrently, in situ reduction of AuNPs on two-dimensional semiconducting tungsten disulfide (WS2) addressed two current material limitations for efficient light harvesting: low monolayer content and lack of optoelectronic tunability. Order-of-magnitude increases in WS2 monolayer content, enhanced broadband optical extinction, and energetic electron injection were probed using a combination of spectroscopic techniques and continuum electromagnetic descriptions. Together, engineering these plasmon-mediated hybrid nanomaterials to facilitate local exchange of optical, thermal, and electronic energy supports design and implementation into several emerging sustainable water and energy applications.

Creating Space Plasma from the Ground

DTIC Science & Technology

2016-05-12

estimated a GW ERP of rf energy would produce an ionosphere half that from an overhead sun, assuming ~15% efficiency conversion of rf energy to...rf energy would produce an ionosphere half that from an overhead sun, assuming ~15% efficiency conversion of rf energy to accelerated electron energy...altitudes along the HAARP field line indicated); images of artificial optical emissions as viewed looking upwards along the magnetic field line from

Conversion from non-orthogonally to orthogonally polarized optical single-sideband modulation using optically injected semiconductor lasers.

PubMed

Hung, Yu-Han; Tseng, Chin-Hao; Hwang, Sheng-Kwang

2018-06-01

This Letter investigates an optically injected semiconductor laser for conversion from non-orthogonally to orthogonally polarized optical single-sideband modulation. The underlying mechanism relies solely on nonlinear laser characteristics and, thus, only a typical semiconductor laser is required as the key conversion unit. This conversion can be achieved for a broadly tunable frequency range up to at least 65 GHz. After conversion, the microwave phase quality, including linewidth and phase noise, is mostly preserved, and simultaneous microwave amplification up to 23 dB is feasible.

Burst-mode optical label processor with ultralow power consumption.

PubMed

Ibrahim, Salah; Nakahara, Tatsushi; Ishikawa, Hiroshi; Takahashi, Ryo

2016-04-04

A novel label processor subsystem for 100-Gbps (25-Gbps × 4λs) burst-mode optical packets is developed, in which a highly energy-efficient method is pursued for extracting and interfacing the ultrafast packet-label to a CMOS-based processor where label recognition takes place. The method involves performing serial-to-parallel conversion for the label bits on a bit-by-bit basis by using an optoelectronic converter that is operated with a set of optical triggers generated in a burst-mode manner upon packet arrival. Here we present three key achievements that enabled a significant reduction in the total power consumption and latency of the whole subsystem; 1) based on a novel operation mechanism for providing amplification with bit-level selectivity, an optical trigger pulse generator, that consumes power for a very short duration upon packet arrival, is proposed and experimentally demonstrated, 2) the energy of optical triggers needed by the optoelectronic serial-to-parallel converter is reduced by utilizing a negative-polarity signal while employing an enhanced conversion scheme entitled the discharge-or-hold scheme, 3) the necessary optical trigger energy is further cut down by half by coupling the triggers through the chip's backside, whereas a novel lens-free packaging method is developed to enable a low-cost alignment process that works with simple visual observation.

WGM-Based Photonic Local Oscillators and Modulators

NASA Technical Reports Server (NTRS)

Matsko, Andrey; Maleki, Lute; Iltchenko, Vladimir; Savchenkov, Anatoliy

2007-01-01

Photonic local oscillators and modulators that include whispering-gallery mode (WGM) optical resonators have been proposed as power-efficient devices for generating and detecting radiation at frequencies of the order of a terahertz. These devices are intended especially to satisfy anticipated needs for receivers capable of detecting lowpower, narrow-band terahertz signals to be used for sensing substances of interest in scientific and military applications. At present, available terahertz-signal detectors are power-inefficient and do not afford the spectral and amplitude resolution needed for detecting such signals. The proposed devices would not be designed according to the conventional approach of direct detection of terahertz radiation. Instead, terahertz radiation would first be up-converted into the optical domain, wherein signals could be processed efficiently by photonic means and detected by optical photodetectors, which are more efficient than are photodetectors used in conventional direct detection of terahertz radiation. The photonic devices used to effect the up-conversion would include a tunable optical local oscillator and a novel electro-optical modulator. A local oscillator according to the proposal would be a WGM-based modelocked laser operating at a desired pulserepetition rate of the order of a terahertz. The oscillator would include a terahertz optical filter based on a WGM microresonator, a fiber-optic delay line, an optical amplifier (which could be either a semiconductor optical amplifier or an erbium-doped optical fiberamplifier), and a WGM Ka-band modulator. The terahertz repetition rate would be obtained through harmonic mode locking: for example, by modulating the light at a frequency of 33 GHz and locking each 33d optical mode, one would create a 1.089-THz pulse train. The high resonance quality factors (Q values) of WGM optical resonators should make it possible to decrease signal-generation threshold power levels significantly below those of other optical-signal-generation devices.

All-optical NRZ wavelength conversion based on a single hybrid III-V/Si SOA and optical filtering.

PubMed

Wu, Yingchen; Huang, Qiangsheng; Keyvaninia, Shahram; Katumba, Andrew; Zhang, Jing; Xie, Weiqiang; Morthier, Geert; He, Jian-Jun; Roelkens, Gunther

2016-09-05

We demonstrate all-optical wavelength conversion (AOWC) of non-return-to-zero (NRZ) signal based on cross-gain modulation in a single heterogeneously integrated III-V-on-silicon semiconductor optical amplifier (SOA) with an optical bandpass filter. The SOA is 500 μm long and consumes less than 250 mW electrical power. We experimentally demonstrate 12.5 Gb/s and 40 Gb/s AOWC for both wavelength up and down conversion.

Wide bandgap OPV polymers based on pyridinonedithiophene unit with efficiency >5%

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schneider, Alexander M.; Lu, Luyao; Manley, Eric F.

2015-06-04

We report the properties of a new series of wide band gap photovoltaic polymers based on the N-alkyl 2-pyridone dithiophene (PDT) unit. These polymers are effective bulk heterojunction solar cell materials when blended with phenyl-C 71-butyric acid methyl ester (PC 71BM). They achieve power conversion efficiencies (up to 5.33%) high for polymers having such large bandgaps, ca. 2.0 eV (optical) and 2.5 eV (electrochemical). As a result, grazing incidence wide-angle X-ray scattering (GIWAXS) reveals strong correlations between π–π stacking distance and regularity, polymer backbone planarity, optical absorption maximum energy, and photovoltaic efficiency.

WGM Resonators for Terahertz-to-Optical Frequency Conversion

NASA Technical Reports Server (NTRS)

Strekalov,Dmitry; Savchenkov, Anatoliy; Matsko, Andrey; Nu, Nan

2008-01-01

Progress has been made toward solving some practical problems in the implementation of terahertz-to-optical frequency converters utilizing whispering-gallery-mode (WGM) resonators. Such frequency converters are expected to be essential parts of non-cryogenic terahertz- radiation receivers that are, variously, under development or contemplated for a variety of applications in airborne and spaceborne instrumentation for astronomical and military uses. In most respects, the basic principles of terahertz-to-optical frequency conversion in WGM resonators are the same as those of microwave (sub-terahertz)-to-optical frequency conversion in WGM resonators, various aspects of which were discussed in the three preceeding articles. To recapitulate: In a receiver following this approach, a preamplified incoming microwave signal (in the present case, a terahertz signal) is up-converted to an optical signal by a technique that exploits the nonlinearity of the electromagnetic response of a whispering-gallery-mode (WGM) resonator made of LiNbO3 or another suitable electro-optical material. Upconversion takes place by three-wave mixing in the resonator. To ensure the required interaction among the optical and terahertz signals, the WGM resonator must be designed and fabricated to function as an electro-optical modulator while simultaneously exhibiting (1) resonance at the required microwave and optical operating frequencies and (2) phase matching among the microwave and optical signals circulating in the resonator. Downstream of the WGM resonator, the up-converted signal is processed photonically by use of a tunable optical filter or local oscillator and is then detected. The practical problems addressed in the present development effort are the following: Satisfaction of the optical and terahertz resonance-frequency requirement is a straightforward matter, inasmuch as the optical and terahertz spectra can be measured. However, satisfaction of the phase-matching requirement is more difficult. The approach followed in the present development is to perform computer simulations of the microwave and optical signals circulating in the resonator to test for phase matching. To enable excitation of the terahertz WGM resonator mode, it is also necessary to ensure phase matching between that mode and the incoming terahertz radiation. In the present development, the incoming signal is coupled into the WGM resonator via a tapered waveguide in the form of a fused silica rod. The phase-matching requirement is satisfied at one point along the taper; the rod is positioned with this point in proximity to the WGM resonator. To maximize the conversion efficiency, it is necessary to maximize the spatial overlap among the terahertz and optical modes in the WGM resonator. In the absence of a special design effort to address this issue, there would be little such overlap because, as a consequence of a large difference between wavelengths, the optical and terahertz modes would be concentrated at different depths from the rim of a WGM resonator. In the present development, overlap is ensured by constructing the WGM resonator as a ring (see figure) so thin that the optical and terahertz modes are effectively forced to overlap.

Bright broadband coherent fiber sources emitting strongly blue-shifted resonant dispersive wave pulses

PubMed Central

Tu, Haohua; Lægsgaard, Jesper; Zhang, Rui; Tong, Shi; Liu, Yuan; Boppart, Stephen A.

2013-01-01

We predict and realize the targeted wavelength conversion from the 1550-nm band of a fs Er:fiber laser to an isolated band inside 370-850 nm, corresponding to a blue-shift of 700-1180 nm. The conversion utilizes resonant dispersive wave generation in widely available optical fibers with good efficiency (~7%). The converted band has a large pulse energy (~1 nJ), high spectral brightness (~1 mW/nm), and broad Gaussian-like spectrum compressible to clean transform-limited ~17 fs pulses. The corresponding coherent fiber sources open up portable applications of optical parametric oscillators and dual-output synchronized ultrafast lasers. PMID:24104233

Enhanced efficiency of the second harmonic inhomogeneous component in an opaque cavity.

PubMed

Roppo, V; Raineri, F; Raj, R; Sagnes, I; Trull, J; Vilaseca, R; Scalora, M; Cojocaru, C

2011-05-15

In this Letter, we experimentally demonstrate the enhancement of the inhomogeneous second harmonic conversion in the opaque region of a GaAs cavity with efficiencies of the order of 0.1% at 612 nm, using 3 ps pump pulses having peak intensities of the order of 10 MW/cm(2). We show that the conversion efficiency of the inhomogeneous, phase-locked second harmonic component is a quadratic function of the cavity factor Q. © 2011 Optical Society of America

Nonlinear optical and multiphoton processes for in situ manipulation and conversion of photons: applications to energy and healthcare (Conference Presentation)

NASA Astrophysics Data System (ADS)

Prasad, Paras N.

2017-02-01

Chiral control of nonlinear optical functions holds a great promise for a wide range of applications including optical signal processing, bio-sensing and chiral bio-imaging. In chiral polyfluorene thin films, we demonstrated extremely large chiral nonlinearity. The physics of manipulating excitation dynamics for photon transformation will be discussed, along with nanochemistry control of upconversion in hierarchically built organic chromophore coupled-core-multiple shell nanostructures which enable introduce new, organic-inorganic energy transfer routes for broadband light harvesting and increased upconversion efficiency via multistep cascaded energy transfer. We are pursuing the applications of photon conversion technology in IR harvesting for photovoltaics, high contrast bioimaging, photoacoustic imaging, photodynamic therapy, and optogenetics. An important application is in Brain research and Neurophotonics for functional mapping and modulation of brain activities. Another new direction pursued is magnetic field control of light in in a chiral polymer nanocomposite to achieve large magneto-optic coefficient which can enable sensing of extremely weak magnetic field due to brain waves. Finally, we will consider the thought provoking concept of utilizing photons to quantify, through magneto-optics, and augment - through nanoptogenetics, the cognitive states, thus paving the path way to a quantified human paradigm.

Frequency-doubled DBR-tapered diode laser for direct pumping of Ti:sapphire lasers generating sub-20 fs pulses.

PubMed

Müller, André; Jensen, Ole Bjarlin; Unterhuber, Angelika; Le, Tuan; Stingl, Andreas; Hasler, Karl-Heinz; Sumpf, Bernd; Erbert, Götz; Andersen, Peter E; Petersen, Paul Michael

2011-06-20

For the first time a single-pass frequency doubled DBR-tapered diode laser suitable for pumping Ti:sapphire lasers generating ultrashort pulses is demonstrated. The maximum output powers achieved when pumping the Ti:sapphire laser are 110 mW (CW) and 82 mW (mode-locked) respectively at 1.2 W of pump power. This corresponds to a reduction in optical conversion efficiencies to 75% of the values achieved with a commercial diode pumped solid-state laser. However, the superior electro-optical efficiency of the diode laser improves the overall efficiency of the Ti:sapphire laser by a factor > 2. The optical spectrum emitted by the Ti:sapphire laser when pumped with our diode laser shows a spectral width of 112 nm (FWHM). Based on autocorrelation measurements, pulse widths of less than 20 fs can therefore be expected.

Hybrid photonic-plasmonic near-field probe for efficient light conversion into the nanoscale hot spot.

PubMed

Koshelev, Alexander; Munechika, Keiko; Cabrini, Stefano

2017-11-01

In this Letter, we present a design and simulations of the novel hybrid photonic-plasmonic near-field probe. Near-field optics is a unique imaging tool that provides optical images with resolution down to tens of nanometers. One of the main limitations of this technology is its low light sensitivity. The presented hybrid probe solves this problem by combining a campanile plasmonic probe with the photonic layer, consisting of the diffractive optic element (DOE). The DOE is designed to match the plasmonic field at the broad side of the campanile probe with the fiber mode. This makes it possible to optimize the size of the campanile tip to convert light efficiently into the hot spot. The simulations show that the hybrid probe is ∼540 times more efficient compared with the conventional campanile on average in the 600-900 nm spectral range.

Coherent Generation of Photo-Thermo-Acoustic Wave from Graphene Sheets

NASA Astrophysics Data System (ADS)

Tian, Yichao; Tian, He; Wu, Yanling; Zhu, Leilei; Tao, Luqi; Zhang, Wei; Shu, Yi; Xie, Dan; Yang, Yi; Wei, Zhiyi; Lu, Xinghua; Ren, Tian-Ling; Shih, Chih-Kang; Zhao, Jimin

Many remarkable properties of graphene are derived from its large energy window for Dirac-like electronic states and have been explored for applications in electronics and photonics. In addition, strong electron-phonon interaction in graphene has led to efficient photo-thermo energy conversions, which has been harnessed for energy applications. By combining the wavelength independent absorption property and the efficient photo-thermo energy conversion, here we report a new type of applications in sound wave generation underlined by a photo-thermo-acoustic energy conversion mechanism. Most significantly, by utilizing ultrafast optical pulses, we demonstrate the ability to control the phase of sound waves generated by the photo-thermal-acoustic process. Our finding paves the way for new types of applications for graphene, such as remote non-contact speakers, optical-switching acoustic devices, etc. National Basic Research Program of China MOST (2012CB821402), External Cooperation Program of Chinese Academy of Sciences (GJHZ1403), and National Natural Science Foundation of China (11274372).

Two and Three Beam Pumped Optical Parametric Amplifier of Chirped Pulses

NASA Astrophysics Data System (ADS)

Ališauskas, S.; Butkus, R.; Pyragaitė, V.; Smilgevičius, V.; Stabinis, A.; Piskarskas, A.

2010-04-01

We present two and three beam pumped optical parametric amplifier of broadband chirped pulses. The seed pulses from Ti:sapphire oscillator were stretched and amplified in a non-collinear geometry pumping with up to three beams derived from independent laser amplifiers. The signal with ˜90 nm bandwidth was amplified up to 0.72 mJ. The conversion efficiency dependence on intersection angles of pump beams is also revealed.

A novel optical waveguide LP01/LP02 mode converter

NASA Astrophysics Data System (ADS)

Shen, Dongya; Wang, Changhui; Ma, Chuan; Mellah, Hakim; Zhang, Xiupu; Yuan, Hong; Ren, Wenping

2018-07-01

A novel optical waveguide LP01 /LP02 mode converter is proposed using combination of bicone structure based on the coupled-mode theory. It is composed of a cladding, a tapered core and combined bicone structure. It is found that this mode converter can have operating bandwidth of 1350-1700 nm, i.e. 350 nm, with a conversion efficiency of ∼90% (∼0.5 dB) and low crosstalk from other modes

Photon energy lifter.

PubMed

Gaburro, Zeno; Ghulinyan, Mher; Riboli, Francesco; Pavesi, Lorenzo; Recati, Alessio; Carusotto, Iacopo

2006-08-07

We propose a time-dependent, spatially periodic photonic structure which is able to shift the carrier frequency of an optical pulse which propagates through it. Taking advantage of the slow group velocity of light in periodic photonic structures, the wavelength conversion process can be performed with an efficiency close to 1 and without affecting the shape and the coherence of the pulse. Quantitative Finite Difference Time Domain simulations are performed for realistic systems with optical parameters of conventional silicon technology.

Biological Effects of Laser Radiation. Volume IV. Optical Second Harmonic Generation in Biological Tissues.

DTIC Science & Technology

1978-10-17

characteristics for optical second- harmonic generation. The collage component of conective tissue may be the principal site for the observed harmonic...Generation in Tissue ; Second Harmonic Generation in Collage; Glutathione, 5MB; Mechanisms; Conversion Efficiency; Significance of order UL AIM UY#m~wmev...sclera, and skin on 694 im. Q-switched ruby laser irradiation. A possible source of this second-harmonic generation was tissue collagen; because of

Efficient magneto-optical mode converter on glass

NASA Astrophysics Data System (ADS)

Garayt, Jean Philippe; Parsy, François; Jamon, Damien; Neveu, Sophie; Royer, François; Ghibaudo, Elise; Broquin, Jean-Emmanuel

2014-03-01

The integration of magneto-optical materials to realize non-reciprocal functions is still a difficult problem, because classical magneto-optical materials require an annealing temperature as high as 700°C. In this framework, this study shows how it is possible to realize efficient magneto-optical mode converter using the association of a magnetic nanoparticles silica/zirconia composite with an ion-exchanged glass waveguide. Using a sol gel process, a silica/zirconia matrix is doped by magnetic nanoparticles (CoFe2O4) and coated on a glass substrate containing straight channel waveguides made by a silver/sodium ion exchange. The extremities of the guides were previously buried using electric field-assisted burial in order to facilitate light injection. Soft annealing (90°C) and UV treatment, both compatible with the ion exchange process, have been implemented to finalize the magneto-optical film. Depending on the amount of nanoparticles in the composite, on the spatial distribution of the field in the guide and on the modal birefringence of the hybrid structure, the TE-TM conversion varies from several degrees to several tens of degrees.

Two-step frequency conversion for connecting distant quantum memories by transmission through an optical fiber

NASA Astrophysics Data System (ADS)

Tamura, Shuhei; Ikeda, Kohei; Okamura, Kotaro; Yoshii, Kazumichi; Hong, Feng-Lei; Horikiri, Tomoyuki; Kosaka, Hideo

2018-06-01

Long-distance quantum communication requires entanglement between distant quantum memories. For this purpose, photon transmission is necessary to connect the distant memories. Here, for the first time, we develop a two-step frequency conversion process (from a visible wavelength to a telecommunication wavelength and back) involving the use of independent two-frequency conversion media where the target quantum memories are nitrogen-vacancy centers in diamonds (with an emission/absorption wavelength of 637.2 nm), and experimentally characterize the performance of this process acting on light from an attenuated CW laser. A total conversion efficiency of approximately 7% is achieved. The noise generated in the frequency conversion processes is measured, and the signal-to-noise ratio is estimated for a single photon signal emitted by a nitrogen-vacancy (NV) center. The developed frequency conversion system has future applications via transmission through a long optical fiber channel at a telecommunication wavelength for a quantum repeater network.

Efficient nonlinear optical conversion of 1.319-micron laser radiation

NASA Astrophysics Data System (ADS)

Byer, Robert L.; Eckardt, Robert C.

1993-01-01

The accomplishments of this program are in the development and application of periodically poled nonlinear optical materials for nonlinear frequency-conversion. We have demonstrated the use of periodically poled lithium niobate (PPLN) as a bulk material for external resonant cavity second-harmonic generation with continuous-wave (cw) output power of 1.7 W. Work that is following this investigation is showing that planar waveguides of PPLN may well be the most satisfactory method of generation of 10's of mW of the 659-nm harmonic of the 1.32-micrometer Nd:YAG laser. We encountered major obstacles obtaining multilayer dielectric coatings necessary to pursue our proposed design of monolithic bulk optical harmonic generators. Additional alternative approaches such as discrete component resonant second harmonic generation employing single domain and periodically poled bulk crystals and monolithic single domain resonators formed by total internal reflection remain under investigation.

Complex modulation using tandem polarization modulators

NASA Astrophysics Data System (ADS)

Hasan, Mehedi; Hall, Trevor

2017-11-01

A novel photonic technique for implementing frequency up-conversion or complex modulation is proposed. The proposed circuit consists of a sandwich of a quarter-wave plate between two polarization modulators, driven, respectively, by an in-phase and quadrature-phase signals. The operation of the circuit is modelled using a transmission matrix method. The theoretical prediction is then validated by simulation using an industry-standard software tool. The intrinsic conversion efficiency of the architecture is improved by 6 dB over a functionally equivalent design based on dual parallel Mach-Zehnder modulators. Non-ideal scenarios such as imperfect alignment of the optical components and power imbalances and phase errors in the electric drive signals are also analysed. As light travels, along one physical path, the proposed design can be implemented using discrete components with greater control of relative optical path length differences. The circuit can further be integrated in any material platform that offers electro-optic polarization modulators.

Scaling submillimeter single-cycle transients toward megavolts per centimeter field strength via optical rectification in the organic crystal OH1.

PubMed

Ruchert, Clemens; Vicario, Carlo; Hauri, Christoph P

2012-03-01

We present the generation of high-power single-cycle terahertz (THz) pulses in the organic salt crystal 2-[3-(4-hydroxystyryl)-5.5-dimethylcyclohex-2-enylidene]malononitrile or OH1. Broadband THz radiation with a central frequency of 1.5 THz (λ(c)=200 μm) and high electric field strength of 440 kV/cm is produced by optical rectification driven by the signal of a powerful femtosecond optical parametric amplifier. A 1.5% pump to THz energy conversion efficiency is reported, and pulse energy stability better than 1% RMS is achieved. An approach toward the realization of higher field strength is discussed. © 2012 Optical Society of America

Convergent optical wired and wireless long-reach access network using high spectral-efficient modulation.

PubMed

Chow, C W; Lin, Y H

2012-04-09

To provide broadband services in a single and low cost perform, the convergent optical wired and wireless access network is promising. Here, we propose and demonstrate a convergent optical wired and wireless long-reach access networks based on orthogonal wavelength division multiplexing (WDM). Both the baseband signal and the radio-over-fiber (ROF) signal are multiplexed and de-multiplexed in optical domain, hence it is simple and the operation speed is not limited by the electronic bottleneck caused by the digital signal processing (DSP). Error-free de-multiplexing and down-conversion can be achieved for all the signals after 60 km (long-reach) fiber transmission. The scalability of the system for higher bit-rate (60 GHz) is also simulated and discussed.

High efficiency and high-energy intra-cavity beam shaping laser

NASA Astrophysics Data System (ADS)

Yang, Hailong; Meng, Junqing; Chen, Weibiao

2015-09-01

We present a technology of intra-cavity laser beam shaping with theory and experiment to obtain a flat-top-like beam with high-pulse energy. A radial birefringent element (RBE) was used in a crossed Porro prism polarization output coupling resonator to modulate the phase delay radially. The reflectively of a polarizer used as an output mirror was variable radially. A flat-top-like beam with 72.5 mJ, 11 ns at 20 Hz was achieved by a side-pumped Nd:YAG zigzag slab laser, and the optical-to-optical conversion efficiency was 17.3%.

Optical Energy Transfer and Conversion System

NASA Technical Reports Server (NTRS)

Hogan, Bartholomew P. (Inventor); Stone, William C. (Inventor)

2015-01-01

An optical power transfer system comprising a fiber spooler, a fiber optic rotary joint mechanically connected to the fiber spooler, and an electrical power extraction subsystem connected to the fiber optic rotary joint with an optical waveguide. Optical energy is generated at and transferred from a base station through fiber wrapped around the spooler, through the rotary joint, and ultimately to the power extraction system at a remote mobility platform for conversion to another form of energy.

A Resonator for Low-Threshold Frequency Conversion

NASA Technical Reports Server (NTRS)

Iltchenko, Vladimir; Matsko, Andrey; Savchenkov, Anatoliy; Maleki, Lute

2004-01-01

A proposed toroidal or disklike dielectric optical resonator (dielectric optical cavity) would be made of an optically nonlinear material and would be optimized for use in parametric frequency conversion by imposition of a spatially periodic permanent electric polarization. The poling (see figure) would suppress dispersions caused by both the material and the geometry of the optical cavity, thereby effecting quasi-matching of the phases of high-resonance-quality (high-Q) whispering-gallery electromagnetic modes. The quasi-phase-matching of the modes would serve to maximize the interactions among them. Such a resonator might be a prototype of a family of compact, efficient nonlinear devices for operation over a broad range of optical wavelengths. A little background information is prerequisite to a meaningful description of this proposal: (1) Described in several prior NASA Tech Briefs articles, the whispering-gallery modes in a component of spheroidal, disklike, or toroidal shape are waveguide modes that propagate circumferentially and are concentrated in a narrow toroidal region centered on the equatorial plane and located near the outermost edge. (2) For the sake of completeness, it must be stated that even though optical resonators of the type considered here are solid dielectric objects and light is confined within them by total internal reflection at dielectric interfaces without need for mirrors, such components are sometimes traditionally called cavities because their effects upon the light propagating within them are similar to those of true cavities bounded by mirrors. (3) For a given set of electromagnetic modes interacting with each other in an optically nonlinear material (e.g., modes associated with the frequencies involved in a frequency-conversion scheme), the threshold power for oscillation depends on the mode volumes and the mode-overlap integral. (4) Whispering-gallery modes are attractive in nonlinear optics because they maximize the effects of nonlinearities by occupying small volumes and affording high Q values

High efficiency and good beam quality of electro-optic, cavity-dumped and double-end pumped Nd:YLF laser

NASA Astrophysics Data System (ADS)

Tang, X. X.; Fan, Z. W.; Qiu, J. S.; Lian, F. Q.; Zhang, X. L.

2012-06-01

In this paper, we describe a Nd:YLF laser based on high-speed RTP electro-optical cavity dumping technique. Two home-made 150 W fiber pump modules are used from both sides to pump Nd:YLF crystal. Coupling systems are the key elements in end-pumped solid-state lasers, the aberrations of which greatly affect the efficiency of the lasers. In order to get high efficient and good quality laser output, the optical software ZEMAX is used to design a four-piece coupling system. When the pumped energy is 32 mJ at the repetition rate of 1 Hz, the output energy is 6.5 mJ with 2.5 ns pulse width. When the pumped energy is 13.1 W at the repetition rate of 200 Hz, the output energy is 2.2 W with small M 2 factor where M {/x 2} is 1.04, and M {/y 2} is 1.05, and the light-light conversion efficiency is up to 16.8%.

Reduction of bonding resistance of two-terminal III-V/Si tandem solar cells fabricated using smart-stack technology

NASA Astrophysics Data System (ADS)

Baba, Masaaki; Makita, Kikuo; Mizuno, Hidenori; Takato, Hidetaka; Sugaya, Takeyoshi; Yamada, Noboru

2017-12-01

This paper describes a method that remarkably reduces the bonding resistance of mechanically stacked two-terminal GaAs/Si and InGaP/Si tandem solar cells, where the top and bottom cells are bonded using a Pd nanoparticle array. A transparent conductive oxide (TCO) layer, which partially covers the surface of the Si bottom cell below the electrodes of the III-V top cell, significantly enhances the fill factor (FF) and cell conversion efficiency. The partial TCO layer reduces the bonding resistance and thus, increases the FF and efficiency of InGaP/Si by factors of 1.20 and 1.11, respectively. Eventually, the efficiency exceeds 15%. Minimizing the optical losses at the bonding interfaces of the TCO layer is important in the fabrication of high-efficiency solar cells. To help facilitate this, the optical losses in the tandem solar cells are thoroughly characterized through optical simulations and experimental verifications.

Broadband and high efficiency all-dielectric metasurfaces for wavefront steering with easily obtained phase shift

NASA Astrophysics Data System (ADS)

Yang, Hui; Deng, Yan

2017-12-01

All-dielectric metasurfaces for wavefront deflecting and optical vortex generating with broadband and high efficiency are demonstrated. The unit cell of the metasurfaces is optimized to function as a half wave-plate with high polarization conversion efficiency (94%) and transmittance (94.5%) at the telecommunication wavelength. Under such a condition, we can get rid of the complicated parameter sweep process for phase shift selecting. Hence, a phase coverage ranges from 0 to 2 π can be easily obtained by introducing the Pancharatnam-Berry phase. Metasurfaces composed of the two pre-designed super cells are demonstrated for optical beam deflecting and vortex beam generating. It is found that the metasurfaces with more phase shift sampling points (small phase shift increment) exhibit better performance. Moreover, optical vortex beams can be generated by the designed metasurfaces within a wavelength range of 200 nm. These results will provide a viable route for designing broadband and high efficiency devices related to phase modulation.

Highly Selective Photothermal Therapy by a Phenoxylated-Dextran-Functionalized Smart Carbon Nanotube Platform.

PubMed

Han, Seungmin; Kwon, Taeyun; Um, Jo-Eun; Haam, Seungjoo; Kim, Woo-Jae

2016-05-01

Near-infrared (NIR) photothermal therapy using biocompatible single-walled carbon nanotubes (SWNTs) is advantageous because as-produced SWNTs, without additional size control, both efficiently absorb NIR light and demonstrate high photothermal conversion efficiency. In addition, covalent attachment of receptor molecules to SWNTs can be used to specifically target infected cells. However, this technique interrupts SWNT optical properties and inevitably lowers photothermal conversion efficiency and thus remains major hurdle for SWNT applications. This paper presents a smart-targeting photothermal therapy platform for inflammatory disease using newly developed phenoxylated-dextran-functionalized SWNTs. Phenoxylated dextran is biocompatible and efficiently suspends SWNTs by noncovalent π-π stacking, thereby minimizing SWNT bundle formations and maintaining original SWNT optical properties. Furthermore, it selectively targets inflammatory macrophages by scavenger-receptor binding without any additional receptor molecules; therefore, its preparation is a simple one-step process. Herein, it is experimentally demonstrated that phenoxylated dextran-SWNTs (pD-SWNTs) are also biocompatible, selectively penetrate inflammatory macrophages over normal cells, and exhibit high photothermal conversion efficiency. Consequently, NIR laser-triggered macrophage treatment can be achieved with high accuracy by pD-SWNT without damaging receptor-free cells. These smart targeting materials can be a novel photothermal agent candidate for inflammatory disease. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Novel D-π-A-π-D type organic chromophores for second harmonic generation and multi-photon absorption applications

NASA Astrophysics Data System (ADS)

Aditya, Pusala; Kumar, Hari; Kumar, Sunil; Rajashekar, Muralikrishna, M.; Muthukumar, V. Sai; Kumar, B. Siva; Sai, S. Siva Sankara; Rao, G. Nageshwar

2013-06-01

We report here the optical and non-linear optical properties of six different novel bis-chalcones of D-π-A-π-D derivatives of diarylideneacetone (DBA). These derivatives have been synthesized by Claisen-Schmidt condensation reaction and were well characterized by using FTIR, 1HNMR, 13CNMR, UV-Visible absorption and mass spectroscopic techniques. The optical bandgap for each of the DBA derivatives were determined both experimentally (UV-Visible spectra & Tauc Plot) and theoretically by ab intio DFT calculations using SIESTA software package. They were found to be in close agreement with each other. The Second Harmonic Generation from these organic chromophores were studied by standard Kurtz and Perry Powder SHG method at 1064 nm. They were found to have superior SHG conversion efficiency when compared to urea (standard sample). Further, we investigated the Multi-Photon absorption properties were using conventional open aperture z-scan technique. These DBA derivatives exhibited strong two photon absorption in the order of 1e-11m/W. Hence, these are potential candidate for various photonic applications like optical power limiting, photonic switching and frequency conversion.

Ultrastable, high efficiency picosecond green light generation using K3B6O10Br series nonlinear optical crystals

NASA Astrophysics Data System (ADS)

Hou, Z. Y.; Xia, M. J.; Wang, L. R.; Xu, B.; Yan, D. X.; Meng, L. P.; Liu, L. J.; Xu, D. G.; Zhang, L.; Wang, X. Y.; Li, R. K.; Chen, C. T.

2017-09-01

Two perovskite-structure K3B6O10Br1-x Cl x (x  =  0 and 0.5) series nonlinear optical crystals were thoroughly investigated for their picosecond 532 nm laser pulses abilities and high power outputs were achieved via second harmonic generation (SHG) technique for the first time. SHG conversion efficiency of 57.3% with a 13.2 mm length K3B6O10Br (KBB) crystal was achieved using a laser source of pulse repetition rate of 10 Hz and pulse width of 25 ps, which is the highest conversion efficiency of ps visible laser based on KBB crystal. And by employing an 80 MHz, 10 ps fundamental laser beam, maximum power outputs of 12 W with K3B6O10Br0.5Cl0.5 (KBBC) and 11.86 W with KBB crystals were successfully demonstrated. Furthermore, the standard deviation jitters of the average power outputs are less than 0.6% and 1.17% by KBB and KBBC, respectively, showing ultrastable power stabilities favorable for practical applications. In addition, the other optical parameters including acceptance angle and temperature bandwidth were also investigated.

Theoretical and experimental investigations of efficient light coupling with spatially varied all dielectric striped waveguides

NASA Astrophysics Data System (ADS)

Yilmaz, Y. A.; Tandogan, S. E.; Hayran, Z.; Giden, I. H.; Turduev, M.; Kurt, H.

2017-07-01

Integrated photonic systems require efficient, compact, and broadband solutions for strong light coupling into and out of optical waveguides. The present work investigates an efficient optical power transferring the problem between optical waveguides having different widths of in/out terminals. We propose a considerably practical and feasible concept to implement and design an optical coupler by introducing gradually index modulation to the coupler section. The index profile of the coupler section is modulated with a Gaussian function by the help of striped waveguides. The effective medium theory is used to replace the original spatially varying index profile with dielectric stripes of a finite length/width having a constant effective refractive index. 2D and 3D finite-difference time-domain analyzes are utilized to investigate the sampling effect of the designed optical coupler and to determine the parameters that play a crucial role in enhancing the optical power transfer performance. Comparing the coupling performance of conventional benchmark adiabatic and butt couplers with the designed striped waveguide coupler, the corresponding coupling efficiency increases from approximately 30% to 95% over a wide frequency interval. In addition, to realize the realistic optical coupler appropriate to integrated photonic applications, the proposed structure is numerically designed on a silicon-on-insulator wafer. The implemented SOI platform based optical coupler operates in the telecom wavelength regime (λ = 1.55 μm), and the dimensions of the striped coupler are kept as 9.77 μm (along the transverse to propagation direction) and 7.69 μm (along the propagation direction) where the unit distance is fixed to be 465 nm. Finally, to demonstrate the operating design principle, the microwave experiments are conducted and the spot size conversion ratio as high as 7.1:1 is measured, whereas a coupling efficiency over 60% in the frequency range of 5.0-16.0 GHz has been also demonstrated.

On-chip optical mode conversion based on dynamic grating in photonic-phononic hybrid waveguide

PubMed Central

Chen, Guodong; Zhang, Ruiwen; Sun, Junqiang

2015-01-01

We present a scheme for reversible and tunable on-chip optical mode conversion based on dynamic grating in a hybrid photonic-phononic waveguide. The dynamic grating is built up through the acousto-optic effect and the theoretical model of the optical mode conversion is developed by considering the geometrical deformation and refractive index change. Three kinds of mode conversions are able to be realized using the same hybrid waveguide structure in a large bandwidth by only changing the launched acoustic frequency. The complete mode conversion can be achieved by choosing a proper acoustic power under a given waveguide length. PMID:25996236

Segregated tandem filter for enhanced conversion efficiency in a thermophotovoltaic energy conversion system

DOEpatents

Brown, E.J.; Baldasaro, P.F.; Dziendziel, R.J.

1997-12-23

A filter system to transmit short wavelength radiation and reflect long wavelength radiation for a thermophotovoltaic energy conversion cell comprises an optically transparent substrate segregation layer with at least one coherent wavelength in optical thickness; a dielectric interference filter deposited on one side of the substrate segregation layer, the interference filter being disposed toward the source of radiation, the interference filter including a plurality of alternating layers of high and low optical index materials adapted to change from transmitting to reflecting at a nominal wavelength {lambda}{sub IF} approximately equal to the bandgap wavelength {lambda}{sub g} of the thermophotovoltaic cell, the interference filter being adapted to transmit incident radiation from about 0.5{lambda}{sub IF} to {lambda}{sub IF} and reflect from {lambda}{sub IF} to about 2{lambda}{sub IF}; and a high mobility plasma filter deposited on the opposite side of the substrate segregation layer, the plasma filter being adapted to start to become reflecting at a wavelength of about 1.5{lambda}{sub IF}. 10 figs.

CW and passively Q-switched laser performance of Nd:Lu2SiO5 crystal

NASA Astrophysics Data System (ADS)

Xu, Xiaodong; Di, Juqing; Zhang, Jian; Tang, Dingyuan; Xu, Jun

2016-01-01

We demonstrated an efficient and controllable dual-wavelength continuous-wave (CW) laser of Nd:Lu2SiO5 (Nd:LSO) crystal. The maximum output power was 3.02 W at wavelength of 1075 nm and 1079 nm, and with increasing of absorbed pump power, the ratio of 1079 nm laser rose. The slope efficiency of 65.6% and optical-to-optical conversion efficiency of 63.3% were obtained. The passively Q-switched laser properties of Nd:LSO were investigated for the first time. The shortest pulse, maximum pulse energy and peak power were 11.58 ns, 29.05 μJ and 2.34 kW, respectively.

Optical domain analog to digital conversion methods and apparatus

DOEpatents

Vawter, Gregory A

2014-05-13

Methods and apparatus for optical analog to digital conversion are disclosed. An optical signal is converted by mapping the optical analog signal onto a wavelength modulated optical beam, passing the mapped beam through interferometers to generate analog bit representation signals, and converting the analog bit representation signals into an optical digital signal. A photodiode receives an optical analog signal, a wavelength modulated laser coupled to the photodiode maps the optical analog signal to a wavelength modulated optical beam, interferometers produce an analog bit representation signal from the mapped wavelength modulated optical beam, and sample and threshold circuits corresponding to the interferometers produce a digital bit signal from the analog bit representation signal.

Performance scaling via passive pulse shaping in cavity-enhanced optical parametric chirped-pulse amplification.

PubMed

Siddiqui, Aleem M; Moses, Jeffrey; Hong, Kyung-Han; Lai, Chien-Jen; Kärtner, Franz X

2010-06-15

We show that an enhancement cavity seeded at the full repetition rate of the pump laser can automatically reshape small-signal gain across the interacting pulses in an optical parametric chirped-pulse amplifier for close-to-optimal operation, significantly increasing both the gain bandwidth and the conversion efficiency, in addition to boosting gain for high-repetition-rate amplification. Applied to a degenerate amplifier, the technique can provide an octave-spanning gain bandwidth.

Waveguide structures in anisotropic nonlinear crystals

NASA Astrophysics Data System (ADS)

Li, Da; Hong, Pengda; Meissner, Helmuth E.

2017-02-01

We report on the design and manufacturing parameters of waveguiding structures of anisotropic nonlinear crystals that are employed for harmonic conversions, using Adhesive-Free Bonding (AFB®). This technology enables a full range of predetermined refractive index differences that are essential for the design of single mode or low-mode propagation with high efficiency in anisotropic nonlinear crystals which in turn results in compact frequency conversion systems. Examples of nonlinear optical waveguides include periodically bonded walk-off corrected nonlinear optical waveguides and periodically poled waveguide components, such as lithium triborate (LBO), beta barium borate (β-BBO), lithium niobate (LN), potassium titanyl phosphate (KTP), zinc germanium phosphide (ZGP) and silver selenogallate (AGSE). Simulation of planar LN waveguide shows that when the electric field vector E lies in the k-c plane, the power flow is directed precisely along the propagation direction, demonstrating waveguiding effect in the planar waveguide. Employment of anisotropic nonlinear optical waveguides, for example in combination with AFB® crystalline fiber waveguides (CFW), provides access to the design of a number of novel high power and high efficiency light sources spanning the range of wavelengths from deep ultraviolet (as short as 200 nm) to mid-infrared (as long as about 18 μm). To our knowledge, the technique is the only generally applicable one because most often there are no compatible cladding crystals available to nonlinear optical cores, especially not with an engineer-able refractive index difference and large mode area.

2000W high beam quality diode laser for direct materials processing

NASA Astrophysics Data System (ADS)

Qin, Wen-bin; Liu, You-qiang; Cao, Yin-hua; Gao, Jing; Pan, Fei; Wang, Zhi-yong

2011-11-01

This article describes high beam quality and kilowatt-class diode laser system for direct materials processing, using optical design software ZEMAX® to simulate the diode laser optical path, including the beam shaping, collimation, coupling, focus, etc.. In the experiment, the diode laser stack of 808nm and the diode laser stack of 915nm were used for the wavelength coupling, which were built vertical stacks up to 16 bars. The threshold current of the stack is 6.4A, the operating current is 85A and the output power is 1280W. Through experiments, after collimating the diode laser beam with micro-lenses, the fast axis BPP of the stack is less than 60mm.mrad, and the slow-axis BPP of the stack is less than 75mm.mrad. After shaping the laser beam and improving the beam quality, the fast axis BPP of the stack is still 60mm.mrad, and the slow-axis BPP of the stack is less than 19mm.mrad. After wavelength coupling and focusing, ultimately the power of 2150W was obtained, focal spot size of 1.5mm * 1.2mm with focal length 300mm. The laser power density is 1.2×105W/cm2, and that can be used for metal remelting, alloying, cladding and welding. The total optical coupling conversion efficiency is 84%, and the total electrical - optical conversion efficiency is 50%.

Optical subcarrier processing for Nyquist SCM signals via coherent spectrum overlapping in four-wave mixing with coherent multi-tone pump.

PubMed

Lu, Guo-Wei; Luís, Ruben S; Mendinueta, José Manuel Delgado; Sakamoto, Takahide; Yamamoto, Naokatsu

2018-01-22

As one of the promising multiplexing and multicarrier modulation technologies, Nyquist subcarrier multiplexing (Nyquist SCM) has recently attracted research attention to realize ultra-fast and ultra-spectral-efficient optical networks. In this paper, we propose and experimentally demonstrate optical subcarrier processing technologies for Nyquist SCM signals such as frequency conversion, multicast and data aggregation of subcarriers, through the coherent spectrum overlapping between subcarriers in four-wave mixing (FWM) with coherent multi-tone pump. The data aggregation is realized by coherently superposing or combining low-level subcarriers to yield high-level subcarriers in the optical field. Moreover, multiple replicas of the data-aggregated subcarriers and the subcarriers carrying the original data are obtained. In the experiment, two 5 Gbps quadrature phase-shift keying (QPSK) subcarriers are coherently combined to generate a 10 Gbps 16 quadrature amplitude modulation (QAM) subcarrier with frequency conversions through the FWM with coherent multi-tone pump. Less than 1 dB optical signal-to-noise ratio (OSNR) penalty variation is observed for the synthesized 16QAM subcarriers after the data aggregation. In addition, some subcarriers are kept in the original formats, QPSK, with a power penalty of less than 0.4 dB with respect to the original input subcarriers. The proposed subcarrier processing technology enables flexibility for spectral management in future dynamic optical networks.

Photon energy conversion by near-zero permittivity nonlinear materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S.; Sinclair, Michael B.; Campione, Salvatore

Efficient harmonic light generation can be achieved with ultrathin films by coupling an incident pump wave to an epsilon-near-zero (ENZ) mode of the thin film. As an example, efficient third harmonic generation from an indium tin oxide nanofilm (.lamda./42 thick) on a glass substrate for a pump wavelength of 1.4 .mu.m was demonstrated. A conversion efficiency of 3.3.times.10.sup.-6 was achieved by exploiting the field enhancement properties of the ENZ mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Numerical analysis of СО laser frequency conversion efficiency in BaGa2GeSe6 crystal

NASA Astrophysics Data System (ADS)

Ionin, A. A.; Kinyaevskiy, I. O.; Mozhaeva, V. A.

2018-03-01

Non-linear optical characteristics of a new BaGa2GeSe6 crystal were numerically studied and compared with ones of the well-known mid-IR nonlinear crystal ZnGeP2 (ZGP). The calculations demonstrated the new crystal to be more efficient or, at least, competitive with the ZGP crystal for frequency conversion of CO- and CO2-laser radiation. It was found that a broadband two-stage frequency conversion of multi-line CO-laser radiation in this crystal is possible within the 2.5-9.0 µm wavelength range, with higher efficiency than in the ZGP crystal.

Cryogenic ultra-high power infrared diode laser bars

NASA Astrophysics Data System (ADS)

Crump, Paul; Frevert, C.; Hösler, H.; Bugge, F.; Knigge, S.; Pittroff, W.; Erbert, G.; Tränkle, G.

2014-02-01

GaAs-based high power diode lasers are the most efficient source of optical energy, and are in wide use in industrial applications, either directly or as pump sources for other laser media. Increased output power per laser is required to enable new applications (increased optical power density) and to reduce cost (more output per component leads to lower cost in $/W). For example, laser bars in the 9xx nm wavelength range with the very highest power and efficiency are needed as pump sources for many high-energy-class solid-state laser systems. We here present latest performance progress using a novel design approach that leverages operation at temperatures below 0°C for increases in bar power and efficiency. We show experimentally that operation at -55°C increases conversion efficiency and suppresses thermal rollover, enabling peak quasi-continuous wave bar powers of Pout > 1.6 kW to be achieved (1.2 ms, 10 Hz), limited by the available current. The conversion efficiency at 1.6 kW is 53%. Following on from this demonstration work, the key open challenge is to develop designs that deliver higher efficiencies, targeting > 80% at 1.6 kW. We present an analysis of the limiting factors and show that low electrical resistance is crucial, meaning that long resonators and high fill factor are needed. We review also progress in epitaxial design developments that leverage low temperatures to enable both low resistance and high optical performance. Latest results will be presented, summarizing the impact on bar performance and options for further improvements to efficiency will also be reviewed.

Chromatic effect in a novel THz generation scheme

NASA Astrophysics Data System (ADS)

Li, Bin; Zhang, Wenyan; Liu, Xiaoqing; Deng, Haixiao; Lan, Taihe; Liu, Bo; Liu, Jia; Wang, Xingtao; Zeng, Zhinan; Zhang, Lijian

2017-11-01

Deriving single or few cycle terahertz (THz) pulse by an intense femtosecond laser through cascaded optical rectification is a crucial technique in cutting-edge time-resolved spectroscopy to characterize micro-scale structures and ultrafast dynamics. Due to the broadband nature of the ultrafast driving laser, the chromatic effect limits the THz conversion efficiency in optical rectification crystals, especially for those implementing the pulse-front tilt scheme, e.g. lithium niobate (LN) crystal, has been prevalently used in the past decade. In this research we developed a brand new type of LN crystal utilizing Brewster coupling, and conducted systematically experimental and simulative investigation for the chromatic effect and multi-dimensionally entangled parameters in THz generation, predicting that an extreme conversion efficiency of ˜10% would be potentially achievable at the THz absorption coefficient of ˜0.5 cm-1. Moreover, we first discovered that the chirp of the driving laser plays a decisive role in the pulse-front tilt scheme, and the THz generation efficiency could be enhanced tremendously by applying an appropriate chirp.

Design of ultra-broadband terahertz polymer waveguide emitters for telecom wavelengths using coupled mode theory.

PubMed

Vallejo, Felipe A; Hayden, L Michael

2013-03-11

We use coupled mode theory, adequately incorporating optical losses, to model ultra-broadband terahertz (THz) waveguide emitters (0.1-20 THz) based on difference frequency generation of femtosecond infrared (IR) optical pulses. We apply the model to a generic, symmetric, five-layer, metal/cladding/core waveguide structure using transfer matrix theory. We provide a design strategy for an efficient ultra-broadband THz emitter and apply it to polymer waveguides with a nonlinear core composed of a poled guest-host electro-optic polymer composite and pumped by a pulsed fiber laser system operating at 1567 nm. The predicted bandwidths are greater than 15 THz and we find a high conversion efficiency of 1.2 × 10(-4) W(-1) by balancing both the modal phase-matching and effective mode attenuation.

Wavelength-tunable waveguides based on polycrystalline organic-inorganic perovskite microwires

NASA Astrophysics Data System (ADS)

Wang, Ziyu; Liu, Jingying; Xu, Zai-Quan; Xue, Yunzhou; Jiang, Liangcong; Song, Jingchao; Huang, Fuzhi; Wang, Yusheng; Zhong, Yu Lin; Zhang, Yupeng; Cheng, Yi-Bing; Bao, Qiaoliang

2016-03-01

Hybrid organic-inorganic perovskites have emerged as new photovoltaic materials with impressively high power conversion efficiency due to their high optical absorption coefficient and long charge carrier diffusion length. In addition to high photoluminescence quantum efficiency and chemical tunability, hybrid organic-inorganic perovskites also show intriguing potential for diverse photonic applications. In this work, we demonstrate that polycrystalline organic-inorganic perovskite microwires can function as active optical waveguides with small propagation loss. The successful production of high quality perovskite microwires with different halogen elements enables the guiding of light with different colours. Furthermore, it is interesting to find that out-coupled light intensity from the microwire can be effectively modulated by an external electric field, which behaves as an electro-optical modulator. This finding suggests the promising applications of perovskite microwires as effective building blocks in micro/nano scale photonic circuits.

Wavelength-tunable waveguides based on polycrystalline organic-inorganic perovskite microwires.

PubMed

Wang, Ziyu; Liu, Jingying; Xu, Zai-Quan; Xue, Yunzhou; Jiang, Liangcong; Song, Jingchao; Huang, Fuzhi; Wang, Yusheng; Zhong, Yu Lin; Zhang, Yupeng; Cheng, Yi-Bing; Bao, Qiaoliang

2016-03-28

Hybrid organic-inorganic perovskites have emerged as new photovoltaic materials with impressively high power conversion efficiency due to their high optical absorption coefficient and long charge carrier diffusion length. In addition to high photoluminescence quantum efficiency and chemical tunability, hybrid organic-inorganic perovskites also show intriguing potential for diverse photonic applications. In this work, we demonstrate that polycrystalline organic-inorganic perovskite microwires can function as active optical waveguides with small propagation loss. The successful production of high quality perovskite microwires with different halogen elements enables the guiding of light with different colours. Furthermore, it is interesting to find that out-coupled light intensity from the microwire can be effectively modulated by an external electric field, which behaves as an electro-optical modulator. This finding suggests the promising applications of perovskite microwires as effective building blocks in micro/nano scale photonic circuits.

Role of cationic size in the optical properties of the LiCl crystal surface: theoretical study.

PubMed

Abdel Halim, Wael Salah; Abdullah, Noha; Abdel-Aal, Safaa; Shalabi, A S

2012-06-01

The size of the cations (either Ca(2+), Sr(2+), Ga(+), or Au(+)) at the F(A1)-type color centers on the (100) surface of LiCl crystal plays an important role in the optical properties of this surface. In this work, double-well potentials at this surface were investigated using ab initio quantum mechanical methods. Quantum clusters were embedded in simulated Coulomb fields that closely approximate the Madelung fields of the host surface, and the ions that were the nearest neighbors to the F(A1) site were allowed to relax to equilibrium. The calculated Stokes-shifted optical transition bands, optical-optical conversion efficiency, and relaxed excited states of the defect-containing surface, as well as the orientational destruction of the color centers, recording sensitivity, exciton (energy) transfer, and the Glasner-Tompkins empirical relation were all found to be sensitive to the size of the dopant cation.

Polymer-Polymer Förster Resonance Energy Transfer Significantly Boosts the Power Conversion Efficiency of Bulk-Heterojunction Solar Cells.

PubMed

Gupta, Vinay; Bharti, Vishal; Kumar, Mahesh; Chand, Suresh; Heeger, Alan J

2015-08-01

Optically resonant donor polymers can exploit a wider range of the solar spectrum effectively without a complicated tandem design in an organic solar cell. Ultrafast Förster resonance energy transfer (FRET) in a polymer-polymer system that significantly improves the power conversion efficiency in bulk heterojunction polymer solar cells from 6.8% to 8.9% is demonstrated, thus paving the way to achieving 15% efficient solar cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Non-plasmonic nanoantennas for surface enhanced spectroscopies with ultra-low heat conversion

PubMed Central

Caldarola, Martín; Albella, Pablo; Cortés, Emiliano; Rahmani, Mohsen; Roschuk, Tyler; Grinblat, Gustavo; Oulton, Rupert F.; Bragas, Andrea V.; Maier, Stefan A.

2015-01-01

Nanoplasmonics has recently revolutionized our ability to control light on the nanoscale. Using metallic nanostructures with tailored shapes, it is possible to efficiently focus light into nanoscale field ‘hot spots'. High field enhancement factors have been achieved in such optical nanoantennas, enabling transformative science in the areas of single molecule interactions, highly enhanced nonlinearities and nanoscale waveguiding. Unfortunately, these large enhancements come at the price of high optical losses due to absorption in the metal, severely limiting real-world applications. Via the realization of a novel nanophotonic platform based on dielectric nanostructures to form efficient nanoantennas with ultra-low light-into-heat conversion, here we demonstrate an approach that overcomes these limitations. We show that dimer-like silicon-based single nanoantennas produce both high surface enhanced fluorescence and surface enhanced Raman scattering, while at the same time generating a negligible temperature increase in their hot spots and surrounding environments. PMID:26238815

High-order Stokes generation in a KTP Raman laser pumped by a passively Q-switched ND:YLF laser

NASA Astrophysics Data System (ADS)

Wang, Maorong; Zhong, Kai; Mei, Jialin; Guo, Shibei; Xu, Degang; Yao, Jianquan

2015-12-01

High-order Stokes wave was observed in an x-cut KTP crystal based on stimulated Raman scattering (SRS) pumped by a passively Q-switched Nd:YLF laser with a Cr4+:YAG saturable absorber. Output spectra including the fundamental wave at 1047 nm and six Stokes wavelengths at 1077 nm, 1110 nm, 1130 nm, 1143 nm, 1164 nm, 1180 nm based on two Raman frequency shift at 267.4 cm-1 and 693.0 cm-1 were obtained simultaneously. We also detected green light generation with output power of 12 mW from self frequency mixing in the KTP crystal. The maximum total output power reached 452 mW at the repetition frequency of 8.1 kHz, corresponding to the optical-to-optical conversion efficiency of 4.61% and pump-to-Raman conversion efficiency of 3.6%.

Non-plasmonic nanoantennas for surface enhanced spectroscopies with ultra-low heat conversion.

PubMed

Caldarola, Martín; Albella, Pablo; Cortés, Emiliano; Rahmani, Mohsen; Roschuk, Tyler; Grinblat, Gustavo; Oulton, Rupert F; Bragas, Andrea V; Maier, Stefan A

2015-08-04

Nanoplasmonics has recently revolutionized our ability to control light on the nanoscale. Using metallic nanostructures with tailored shapes, it is possible to efficiently focus light into nanoscale field 'hot spots'. High field enhancement factors have been achieved in such optical nanoantennas, enabling transformative science in the areas of single molecule interactions, highly enhanced nonlinearities and nanoscale waveguiding. Unfortunately, these large enhancements come at the price of high optical losses due to absorption in the metal, severely limiting real-world applications. Via the realization of a novel nanophotonic platform based on dielectric nanostructures to form efficient nanoantennas with ultra-low light-into-heat conversion, here we demonstrate an approach that overcomes these limitations. We show that dimer-like silicon-based single nanoantennas produce both high surface enhanced fluorescence and surface enhanced Raman scattering, while at the same time generating a negligible temperature increase in their hot spots and surrounding environments.

520-µJ mid-infrared femtosecond laser at 2.8 µm by 1-kHz KTA optical parametric amplifier

NASA Astrophysics Data System (ADS)

He, Huijun; Wang, Zhaohua; Hu, Chenyang; Jiang, Jianwang; Qin, Shuang; He, Peng; Zhang, Ninghua; Yang, Peilong; Li, Zhiyuan; Wei, Zhiyi

2018-02-01

We report on a 520-µJ, 1-kHz mid-infrared femtosecond optical parametric amplifier system driven by a Ti:sapphire laser system. The seeding signal was generated from white-light continuum in YAG plate and then amplified in four non-collinear amplification stages and the idler was obtained in the last stage with central wavelength at 2.8 µm and bandwidth of 525 nm. To maximize the bandwidth of the idler, a theoretical method was developed to give an optimum non-collinear angle and estimate the conversion efficiency and output spectrum. As an experimental result, laser pulse energy up to 1.8 mJ for signal wave and 520 µJ for idler wave were obtained in the last stage under 10-mJ pump energy, corresponding to a pump-to-idler conversion efficiency of 5.2%, which meets well with the numerical calculation.

Compact conductively cooled electro-optical Q-switched Nd:YAG laser

NASA Astrophysics Data System (ADS)

Li, Chaoyang; Lu, Chengqiang; Li, Chuan; Zang, Yannan; Yang, Zhen; Han, Song; Li, Ye; Yang, Ning; Shi, Junfeng; Zhou, Zewu

2017-11-01

We report on a compact conductively cooled high-repetition-rate nanosecond Nd:YAG laser. The oscillator was an laser diode side-pumped electro-optical (EO) Q-switched Nd:YAG rod laser adopting unstable cavity with a variable reflectivity mirror. A pulse train of 142 mJ with duration of 10 ns, repetition rate of 80 Hz at 1064 nm has been achieved. Maximum pulse energy was obtained at the pump energy of 1380 mJ, corresponding to the optical-optical conversion efficiency of 10.3%. The peak power was deduced to be 14.2 MW. The near-field pattern demonstrated a nearly super Gaussian flat top profile. To our knowledge, this is the highest repetition rate operation for a conductively cooled EO Q-switched Nd:YAG rod laser.

Characteristic analysis of a polarization output coupling Porro prism resonator

NASA Astrophysics Data System (ADS)

Yang, Hailong; Meng, Junqing; Chen, Weibiao

2015-02-01

An Electro-optical Q-switched Nd:YAG slab laser with a crossed misalignment Porro prism resonator for space applications has been theoretically and experimentally investigated. The phase shift induced by the combination of different wave plates and Porro prism azimuth angles have been studied for creating high loss condition prior to Q-switching. The relationship of the effective output coupling reflectivity and the employed Q-switch driving voltage is explored by using Jones matrix optics. In the experiment, the maximum output pulse energy of 93 mJ with 14-ns pulse duration is obtained at the repetition rate of 20 Hz and the optical-to-optical conversion efficiency is 16.8%. The beam quality factors are M 2 x = 2.5 and M 2y = 2.2, respectively.

High power telecommunication-compatible photoconductive terahertz emitters based on plasmonic nano-antenna arrays.

PubMed

Yardimci, Nezih Tolga; Lu, Hong; Jarrahi, Mona

2016-11-07

We present a high-power and broadband photoconductive terahertz emitter operating at telecommunication optical wavelengths, at which compact and high-performance fiber lasers are commercially available. The presented terahertz emitter utilizes an ErAs:InGaAs substrate to achieve high resistivity and short carrier lifetime characteristics required for robust operation at telecommunication optical wavelengths. It also uses a two-dimensional array of plasmonic nano-antennas to offer significantly higher optical-to-terahertz conversion efficiencies compared to the conventional photoconductive emitters, while maintaining broad operation bandwidths. We experimentally demonstrate pulsed terahertz radiation over 0.1-5 THz frequency range with the power levels as high as 300  μ W. This is the highest-reported terahertz radiation power from a photoconductive emitter operating at telecommunication optical wavelengths.

High power telecommunication-compatible photoconductive terahertz emitters based on plasmonic nano-antenna arrays

PubMed Central

Yardimci, Nezih Tolga; Lu, Hong; Jarrahi, Mona

2016-01-01

We present a high-power and broadband photoconductive terahertz emitter operating at telecommunication optical wavelengths, at which compact and high-performance fiber lasers are commercially available. The presented terahertz emitter utilizes an ErAs:InGaAs substrate to achieve high resistivity and short carrier lifetime characteristics required for robust operation at telecommunication optical wavelengths. It also uses a two-dimensional array of plasmonic nano-antennas to offer significantly higher optical-to-terahertz conversion efficiencies compared to the conventional photoconductive emitters, while maintaining broad operation bandwidths. We experimentally demonstrate pulsed terahertz radiation over 0.1–5 THz frequency range with the power levels as high as 300 μW. This is the highest-reported terahertz radiation power from a photoconductive emitter operating at telecommunication optical wavelengths. PMID:27916999

Pulse sequences for efficient multi-cycle terahertz generation in periodically poled lithium niobate.

PubMed

Ravi, Koustuban; Schimpf, Damian N; Kärtner, Franz X

2016-10-31

The use of laser pulse sequences to drive the cascaded difference frequency generation of high energy, high peak-power and multi-cycle terahertz pulses in cryogenically cooled (100 K) periodically poled Lithium Niobate is proposed and studied. Detailed simulations considering the coupled nonlinear interaction of terahertz and optical waves (or pump depletion), show that unprecedented optical-to-terahertz energy conversion efficiencies > 5%, peak electric fields of hundred(s) of mega volts/meter at terahertz pulse durations of hundred(s) of picoseconds can be achieved. The proposed methods are shown to circumvent laser induced damage limitations at Joule-level pumping by 1µm lasers to enable multi-cycle terahertz sources with pulse energies > 10 milli-joules. Various pulse sequence formats are proposed and analyzed. Numerical calculations for periodically poled structures accounting for cascaded difference frequency generation, self-phase-modulation, cascaded second harmonic generation and laser induced damage are introduced. The physics governing terahertz generation using pulse sequences in this high conversion efficiency regime, limitations and practical considerations are discussed. It is shown that varying the poling period along the crystal length and further reduction of absorption can lead to even higher energy conversion efficiencies >10%. In addition to numerical calculations, an analytic formulation valid for arbitrary pulse formats and closed-form expressions for important cases are presented. Parameters optimizing conversion efficiency in the 0.1-1 THz range, the corresponding peak electric fields, crystal lengths and terahertz pulse properties are furnished.

A trident dithienylethene-perylenemonoimide dyad with super fluorescence switching speed and ratio

NASA Astrophysics Data System (ADS)

Li, Chong; Yan, Hui; Zhao, Ling-Xi; Zhang, Guo-Feng; Hu, Zhe; Huang, Zhen-Li; Zhu, Ming-Qiang

2014-12-01

Photoswitchable fluorescent diarylethenes are promising in molecular optical memory and photonic devices. However, the performance of current diarylethenes is far from satisfactory because of the scarcity of high-speed switching capability and large fluorescence on-off ratio. Here we report a trident perylenemonoimide dyad modified by triple dithienylethenes whose photochromic fluorescence quenching ratio at the photostationary state exceeds 10,000 and the fluorescence quenching efficiency is close to 100% within seconds of ultraviolet irradiation. The highly sensitive fluorescence on/off switching of the trident dyad enables recyclable fluorescence patterning and all-optical transistors. The prototype optical device based on the trident dyad enables the optical switching of incident light and conversion from incident light wavelength to transmitted light wavelength, which is all-optically controlled, reversible and wavelength-convertible. In addition, the trident dyad-staining block copolymer vesicles are observed via optical nanoimaging with a sub-100 nm resolution, portending a potential prospect of the dithienylethene dyad in super-resolution imaging.

A trident dithienylethene-perylenemonoimide dyad with super fluorescence switching speed and ratio.

PubMed

Li, Chong; Yan, Hui; Zhao, Ling-Xi; Zhang, Guo-Feng; Hu, Zhe; Huang, Zhen-Li; Zhu, Ming-Qiang

2014-12-12

Photoswitchable fluorescent diarylethenes are promising in molecular optical memory and photonic devices. However, the performance of current diarylethenes is far from satisfactory because of the scarcity of high-speed switching capability and large fluorescence on-off ratio. Here we report a trident perylenemonoimide dyad modified by triple dithienylethenes whose photochromic fluorescence quenching ratio at the photostationary state exceeds 10,000 and the fluorescence quenching efficiency is close to 100% within seconds of ultraviolet irradiation. The highly sensitive fluorescence on/off switching of the trident dyad enables recyclable fluorescence patterning and all-optical transistors. The prototype optical device based on the trident dyad enables the optical switching of incident light and conversion from incident light wavelength to transmitted light wavelength, which is all-optically controlled, reversible and wavelength-convertible. In addition, the trident dyad-staining block copolymer vesicles are observed via optical nanoimaging with a sub-100 nm resolution, portending a potential prospect of the dithienylethene dyad in super-resolution imaging.

Electronic-To-Optical-To-Electronic Packet-Data Conversion

NASA Technical Reports Server (NTRS)

Monacos, Steve

1996-01-01

Space-time multiplexer (STM) cell-based communication system designed to take advantage of both high throughput attainable in optical transmission links and flexibility and functionality of electronic processing, storage, and switching. Long packets segmented and transmitted optically by wavelength-division multiplexing. Performs optoelectronic and protocol conversion between electronic "store-and-forward" protocols and optical "hot-potato" protocols.

Towards rewritable multilevel optical data storage in single nanocrystals.

PubMed

Riesen, Nicolas; Pan, Xuanzhao; Badek, Kate; Ruan, Yinlan; Monro, Tanya M; Zhao, Jiangbo; Ebendorff-Heidepriem, Heike; Riesen, Hans

2018-04-30

Novel approaches for digital data storage are imperative, as storage capacities are drastically being outpaced by the exponential growth in data generation. Optical data storage represents the most promising alternative to traditional magnetic and solid-state data storage. In this paper, a novel and energy efficient approach to optical data storage using rare-earth ion doped inorganic insulators is demonstrated. In particular, the nanocrystalline alkaline earth halide BaFCl:Sm is shown to provide great potential for multilevel optical data storage. Proof-of-concept demonstrations reveal for the first time that these phosphors could be used for rewritable, multilevel optical data storage on the physical dimensions of a single nanocrystal. Multilevel information storage is based on the very efficient and reversible conversion of Sm 3+ to Sm 2+ ions upon exposure to UV-C light. The stored information is then read-out using confocal optics by employing the photoluminescence of the Sm 2+ ions in the nanocrystals, with the signal strength depending on the UV-C fluence used during the write step. The latter serves as the mechanism for multilevel data storage in the individual nanocrystals, as demonstrated in this paper. This data storage platform has the potential to be extended to 2D and 3D memory for storage densities that could potentially approach petabyte/cm 3 levels.

Engineering quadratic nonlinear photonic crystals for frequency conversion of lasers

NASA Astrophysics Data System (ADS)

Chen, Baoqin; Hong, Lihong; Hu, Chenyang; Zhang, Chao; Liu, Rongjuan; Li, Zhiyuan

2018-03-01

Nonlinear frequency conversion offers an effective way to extend the laser wavelength range. Quadratic nonlinear photonic crystals (NPCs) are artificial materials composed of domain-inversion structures whose sign of nonlinear coefficients are modulated with desire to implement quasi-phase matching (QPM) required for nonlinear frequency conversion. These structures can offer various reciprocal lattice vectors (RLVs) to compensate the phase-mismatching during the quadratic nonlinear optical processes, including second-harmonic generation (SHG), sum-frequency generation and the cascaded third-harmonic generation (THG). The modulation pattern of the nonlinear coefficients is flexible, which can be one-dimensional or two-dimensional (2D), be periodic, quasi-periodic, aperiodic, chirped, or super-periodic. As a result, these NPCs offer very flexible QPM scheme to satisfy various nonlinear optics and laser frequency conversion problems via design of the modulation patterns and RLV spectra. In particular, we introduce the electric poling technique for fabricating QPM structures, a simple effective nonlinear coefficient model for efficiently and precisely evaluating the performance of QPM structures, the concept of super-QPM and super-periodically poled lithium niobate for finely tuning nonlinear optical interactions, the design of 2D ellipse QPM NPC structures enabling continuous tunability of SHG in a broad bandwidth by simply changing the transport direction of pump light, and chirped QPM structures that exhibit broadband RLVs and allow for simultaneous radiation of broadband SHG, THG, HHG and thus coherent white laser from a single crystal. All these technical, theoretical, and physical studies on QPM NPCs can help to gain a deeper insight on the mechanisms, approaches, and routes for flexibly controlling the interaction of lasers with various QPM NPCs for high-efficiency frequency conversion and creation of novel lasers.

Diode pumped CW and passively Q-switched Nd:LGGG laser at 1062 nm

NASA Astrophysics Data System (ADS)

Yang, H.; Jia, Z. T.; Zhang, B. T.; He, J. L.; Liu, S. D.; Yang, Y.; Tao, X. T.

2012-05-01

We report a Nd:LGGG laser at 1062 nm in the operations of the continuous-wave (CW) and passively Q-switching. The maximum CW output power of 5.62 W was obtained, corresponding to an optical-to-optical conversion efficiency of 49.0% and slope efficiency of 55.9%. By using Cr4+:YAG with initial transmission of 94% as the saturable absorber, for the first time, we got the maximum passively Q-switched output power of 1.21 W, accompanied with a highest pulse repetition rate of 27.1 kHz and a shortest pulse width of 9.1 ns.

Properties and Frequency Conversion of High-Brightness Diode-Laser Systems

NASA Astrophysics Data System (ADS)

Boller, Klaus-Jochen; Beier, Bernard; Wallenstein, Richard

An overview of recent developments in the field of high-power, high-brightness diode-lasers, and the optically nonlinear conversion of their output into other wavelength ranges, is given. We describe the generation of continuous-wave (CW) laser beams at power levels of several hundreds of milliwatts to several watts with near-perfect spatial and spectral properties using Master-Oscillator Power-Amplifier (MOPA) systems. With single- or double-stage systems, using amplifiers of tapered or rectangular geometry, up to 2.85 W high-brightness radiation is generated at wavelengths around 810nm with AlGaAs diodes. Even higher powers, up to 5.2W of single-frequency and high spatial quality beams at 925nm, are obtained with InGaAs diodes. We describe the basic properties of the oscillators and amplifiers used. A strict proof-of-quality for the diode radiation is provided by direct and efficient nonlinear optical conversion of the diode MOPA output into other wavelength ranges. We review recent experiments with the highest power levels obtained so far by direct frequency doubling of diode radiation. In these experiments, 100mW single-frequency ultraviolet light at 403nm was generated, as well as 1W of single-frequency blue radiation at 465nm. Nonlinear conversion of diode radiation into widely tunable infrared radiation has recently yielded record values. We review the efficient generation of widely tunable single-frequency radiation in the infrared with diode-pumped Optical Parametric Oscillators (OPOs). With this system, single-frequency output radiation with powers of more than 0.5W was generated, widely tunable around wavelengths of 2.1,m and 1.65,m and with excellent spectral and spatial quality. These developments are clear indicators of recent advances in the field of high-brightness diode-MOPA systems, and may emphasize their future central importance for applications within a vast range of optical wavelengths.

Integrated four-channel all-fiber up-conversion single-photon-detector with adjustable efficiency and dark count.

PubMed

Zheng, Ming-Yang; Shentu, Guo-Liang; Ma, Fei; Zhou, Fei; Zhang, Hai-Ting; Dai, Yun-Qi; Xie, Xiuping; Zhang, Qiang; Pan, Jian-Wei

2016-09-01

Up-conversion single photon detector (UCSPD) has been widely used in many research fields including quantum key distribution, lidar, optical time domain reflectrometry, and deep space communication. For the first time in laboratory, we have developed an integrated four-channel all-fiber UCSPD which can work in both free-running and gate modes. This compact module can satisfy different experimental demands with adjustable detection efficiency and dark count. We have characterized the key parameters of the UCSPD system.

Realization of rapid debugging for detection circuit of optical fiber gas sensor: Using an analog signal source

NASA Astrophysics Data System (ADS)

Tian, Changbin; Chang, Jun; Wang, Qiang; Wei, Wei; Zhu, Cunguang

2015-03-01

An optical fiber gas sensor mainly consists of two parts: optical part and detection circuit. In the debugging for the detection circuit, the optical part usually serves as a signal source. However, in the debugging condition, the optical part can be easily influenced by many factors, such as the fluctuation of ambient temperature or driving current resulting in instability of the wavelength and intensity for the laser; for dual-beam sensor, the different bends and stresses of the optical fiber will lead to the fluctuation of the intensity and phase; the intensity noise from the collimator, coupler, and other optical devices in the system will also result in the impurity of the optical part based signal source. In order to dramatically improve the debugging efficiency of the detection circuit and shorten the period of research and development, this paper describes an analog signal source, consisting of a single chip microcomputer (SCM), an amplifier circuit, and a voltage-to-current conversion circuit. It can be used to realize the rapid debugging detection circuit of the optical fiber gas sensor instead of optical part based signal source. This analog signal source performs well with many other advantages, such as the simple operation, small size, and light weight.

All-optical control of light on a graphene-on-silicon nitride chip using thermo-optic effect.

PubMed

Qiu, Ciyuan; Yang, Yuxing; Li, Chao; Wang, Yifang; Wu, Kan; Chen, Jianping

2017-12-06

All-optical signal processing avoids the conversion between optical signals and electronic signals and thus has the potential to achieve a power efficient photonic system. Micro-scale all-optical devices for light manipulation are the key components in the all-optical signal processing and have been built on the semiconductor platforms (e.g., silicon and III-V semiconductors). However, the two-photon absorption (TPA) effect and the free-carrier absorption (FCA) effect in these platforms deteriorate the power handling and limit the capability to realize complex functions. Instead, silicon nitride (Si 3 N 4 ) provides a possibility to realize all-optical large-scale integrated circuits due to its insulator nature without TPA and FCA. In this work, we investigate the physical dynamics of all-optical control on a graphene-on-Si 3 N 4 chip based on thermo-optic effect. In the experimental demonstration, a switching response time constant of 253.0 ns at a switching energy of ~50 nJ is obtained with a device dimension of 60 μm × 60 μm, corresponding to a figure of merit (FOM) of 3.0 nJ mm. Detailed coupled-mode theory based analysis on the thermo-optic effect of the device has been performed.

Optimization of mid-IR generation from a periodically poled MgO doped stoichiometric lithium tantalate optical parametric oscillator with intracavity difference frequency mixing

NASA Astrophysics Data System (ADS)

Hatano, Hideki; Slater, Richard; Takekawa, Shunji; Kusano, Masahiro; Watanabe, Makoto

2017-07-01

We demonstrate 43% slope efficiency for generation of ∼3200 nm light, a wavelength considered to be ideal for laser induced ultrasound generation in carbon fiber reinforced plastic. High slope efficiency was obtained by optimizing crystal lengths, cavity length and mirror reflectivity using a two crystal optical parametric oscillator+difference frequency mixing (OPO+DFM) nonlinear wavelength conversion scheme. Mid-IR output >12 mJ was obtained from a 1064 nm Nd:YAG pump laser with 12 ns pulse width (FWHM) and containing pulse energy of 43 mJ. A compact, single temperature crystal oven is described along with some suggestions for improving the slope efficiency.

Improvement of on/off ratio in single-shot multichannel demultiplexing by using an optical Kerr gate of a squarylium dye J aggregate film

NASA Astrophysics Data System (ADS)

Sato, Yasuhiro; Furuki, Makoto; Tian, Minquan; Iwasa, Izumi; Pu, Lyong Sun; Tatsuura, Satoshi

2002-04-01

We demonstrated ultrafast single-shot multichannel demultiplexing by using a squarylium dye J aggregate film as an optical Kerr medium. High efficiency and fast recovery of the optical Kerr responses were achieved when a signal-pulse wavelength was close to the absorption peak of the J aggregate film with off-resonant excitation. The on/off ratio in demultiplexing of 1 Tb/s signals was improved to be approximately 5. By introducing time delay to both horizontal and vertical directions, we succeeded in directly observing the conversion of 1 Tb/s serial signals into two-dimensionally arranged parallel signals.

Magneto-optical waveguides made of cobalt ferrite nanoparticles embedded in silica/zirconia organic-inorganic matrix

NASA Astrophysics Data System (ADS)

Choueikani, Fadi; Royer, François; Jamon, Damien; Siblini, Ali; Rousseau, Jean Jacques; Neveu, Sophie; Charara, Jamal

2009-02-01

This paper describes a way to develop magneto-optical waveguides via sol-gel process. They are made of cobalt ferrite nanoparticles embedded in a silica/zirconia matrix. Thin films are coated on glass substrate using the dip-coating technique. Annealing and UV treatment are applied to finalize sample preparation. Therefore, planar waveguides combining magneto-optical properties with a low refractive index (≈1,5) are obtained. M-lines and free space ellipsometry measurements show a specific Faraday rotation of 250°/cm and a modal birefringence of 1×10-4 at 820 nm. Thus, the mode conversion efficiency can reach a maximum value around 56%.

Molecular-Barrier-Enhanced Aromatic Fluorophores in Cocrystals with Unity Quantum Efficiency.

PubMed

Ye, Huanqing; Liu, Guangfeng; Liu, Sheng; Casanova, David; Ye, Xin; Tao, Xutang; Zhang, Qichun; Xiong, Qihua

2018-02-12

Singlet-triplet conversion in organic light-emitting materials introduces non-emissive (dark) and long-lived triplet states, which represents a significant challenge in constraining the optical properties. There have been considerable attempts at separating singlets and triplets in long-chain polymers, scavenging triplets, and quenching triplets with heavy metals; nonetheless, such triplet-induced loss cannot be fully eliminated. Herein, a new strategy of crafting a periodic molecular barrier into the π-conjugated matrices of organic aromatic fluorophores is reported. The molecular barriers effectively block the singlet-to-triplet pathway, resulting in near-unity photoluminescence quantum efficiency (PLQE) of the organic fluorophores. The transient optical spectroscopy measurements confirm the absence of the triplet absorption. These studies provide a general approach to preventing the formation of dark triplet states in organic semiconductors and bring new opportunities for the development of advanced organic optics and photonics. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Long-Distance Single Photon Transmission from a Trapped Ion via Quantum Frequency Conversion

NASA Astrophysics Data System (ADS)

Walker, Thomas; Miyanishi, Koichiro; Ikuta, Rikizo; Takahashi, Hiroki; Vartabi Kashanian, Samir; Tsujimoto, Yoshiaki; Hayasaka, Kazuhiro; Yamamoto, Takashi; Imoto, Nobuyuki; Keller, Matthias

2018-05-01

Trapped atomic ions are ideal single photon emitters with long-lived internal states which can be entangled with emitted photons. Coupling the ion to an optical cavity enables the efficient emission of single photons into a single spatial mode and grants control over their temporal shape. These features are key for quantum information processing and quantum communication. However, the photons emitted by these systems are unsuitable for long-distance transmission due to their wavelengths. Here we report the transmission of single photons from a single 40Ca+ ion coupled to an optical cavity over a 10 km optical fiber via frequency conversion from 866 nm to the telecom C band at 1530 nm. We observe nonclassical photon statistics of the direct cavity emission, the converted photons, and the 10 km transmitted photons, as well as the preservation of the photons' temporal shape throughout. This telecommunication-ready system can be a key component for long-distance quantum communication as well as future cloud quantum computation.

Ultrathin Organic Solar Cells with a Power Conversion Efficiency of Over ≈13.0%, Based on the Spatial Corrugation of the Metal Electrode-Cathode Fabry-Perot Cavity.

PubMed

In, Sungjun; Park, Namkyoo

2018-04-01

The application of nanophotonic structures for organic solar cells (OSCs) is quite popular and successful, and has led to increased optical absorption, better spectral overlap with solar irradiances, and improved charge collection. Significant improvements in the power conversion efficiency (PCE) have also been reported, exceeding 11%. Nonetheless, with the given material properties of OSCs with low optical absorption, narrow spectrum, short transport length of carriers, and nonuniform photocarrier generations resulting from the nanophotonic structure, the PCE of single-junction OSCs has been stagnant over the past few years, at a barrier of 12%. Here, an ultrathin inverted OSC structure with the highest efficiency of ≈13.0%, while being made from widely used organic materials, is demonstrated. By introducing a smooth spatial corrugation to the vertical plasmonic cavity enclosing the active layer, in-plane propagation modes and hybridized Fabry-Perot cavity modes inside the corrugated cavity are derived to achieve an ultralow Q , uniform coverage of optical absorption, in addition to uniform photocarrier generation and transport. As the first demonstration of ultra-broadband absorption with the introduction of spatial corrugation to the ultrathin metal film electrode-cathode Fabry-Perot cavity, future applications of the same concept in other light-harvesting devices utilizing different materials and structures are expected.

Nonlinear Dynamics of Photonics for Optical Signal Processing - Optical Frequency Conversion and Optical DSB-to-SSB Conversion

DTIC Science & Technology

2015-09-17

the literature, such as mode-locked lasers, optoelectronic oscillators , and laser optical heterodyne, our scheme is (1) up to 100 times better in... Optoelectronic oscillator : This scheme generates microwaves that are tunable only within a few gigahertz and that are stable with a linewidth down to 1 Hz... oscillation frequency, which can be easily adjusted by changing the power and frequency of the optical input. Tens to hundreds of GHz or even THz of

All-optical NRZ-to-RZ data format conversion with optically injected laser diode or semiconductor optical amplifier

NASA Astrophysics Data System (ADS)

Lin, Gong-Ru; Chang, Yung-Cheng; Yu, Kun-Chieh

2006-09-01

By injecting the optical NRZ data into a Fabry-Perot laser diode (FPLD) synchronously modulated at below threshold condition or a semiconductor optical amplifier (SOA) gain-depleted with a backward injected clock stream, the all-optical non-return to zero (NRZ) to return-to-zero (RZ) format conversion of a STM-64 date-stream for synchronous digital hierarchy (SDH) or an OC-192 data stream for synchronous optical network (SONET) in high-speed fiber-optic communication link can be performed. Without the assistance of any complicated RF electronic circuitry, the output RZ data-stream at bit rate of up to 10 Gbit/s is successfully transformed in the optically NRZ injection-locked FPLD, in which the incoming NRZ data induces gain-switching of the FPLD without DC driving current or at below threshold condition. A power penalty of 1.2 dB is measured after NRZ-to-RZ transformation in the FPLD. Alternatively, the all-optical 10Gbits/s NRZ-to-RZ format conversion can also be demonstrated in a semiconductor optical amplifier under a backward dark-optical-comb injection with its duty-cycle 70%, which is obtained by reshaping from the received data clock at 10 GHz. The incoming optical NRZ data-stream is transformed into a pulsed RZ data-stream with its duty-cycle, rms timing jitter, and conversion gain of 15%, 4ps, and 3dB, respectively. In contrast to the FPLD, the SOA based NRZ-to-RZ converter exhibits an enhanced extinction ratio from 7 to 13 dB, and BER of 10 -13 at -18.5 dBm. In particular, the power penalty of the received RZ data-stream has greatly improved by 5 dB as compared to that obtained from FPLD.

Optical rectenna operation: where Maxwell meets Einstein

NASA Astrophysics Data System (ADS)

Joshi, Saumil; Moddel, Garret

2016-07-01

Optical rectennas are antenna-coupled diode rectifiers that receive and convert optical-frequency electromagnetic radiation into DC output. The analysis of rectennas is carried out either classically using Maxwell’s wave-like approach, or quantum-mechanically using Einstein’s particle-like approach for electromagnetic radiation. One of the characteristics of classical operation is that multiple photons transfer their energy to individual electrons, whereas in quantum operation each photon transfers its energy to each electron. We analyze the correspondence between the two approaches by comparing rectenna response first to monochromatic illumination obtained using photon-assisted tunnelling theory and classical theory. Applied to broadband rectenna operation, this correspondence provides clues to designing a rectenna solar cell that has the potential to exceed the 44% quantum-limited conversion efficiency. The comparison of operating regimes shows how optical rectenna operation differs from microwave rectenna operation.

Acousto-optical Transducer with Surface Plasmons

NASA Astrophysics Data System (ADS)

Kolomenskii, A. A.; Surovic, E.; Schuessler, H. A.

2018-04-01

The surface plasmon resonance (SPR) is a sensitive technique for the detection of changes in dielectric parameters in close proximity to a metal film supporting surface plasmon waves. Here we study the application of the SPR effect to an efficient conversion of an acoustic signal into an optical one. Such a transducer potentially has a large bandwidth and good sensitivity. When an acoustic wave is incident onto a receiving plate positioned within the penetration depth of the surface plasmons, it creates displacements of the surface of the plate and, thus, modulates the dielectric properties in the proximity of the gold film. This modulation, in turn, modifies the light reflection under surface plasmon resonance conditions. We simulate characteristics of this acousto-optical transducer with surface plasmons and provide sets of parameters at the optical wavelength of 800 nm and 633 nm for its realization.

Experimental study of electro-optical Q-switched pulsed Nd:YAG laser

NASA Astrophysics Data System (ADS)

A, Maleki; M Kavosh, Tehrani; H, Saghafifar; M, H. Moghtader Dindarlu

2016-03-01

We report the specification of a compact and stable side diode-pumped Q-switched pulsed Nd:YAG laser. We experimentally study and compare the performance of the pulsed Nd:YAG laser in the free-running and Q-switched modes at different pulse repetition rates from 1 Hz to 100 Hz. The laser output energy is stabilized by using a special configuration of the optical resonator. In this laser, an unsymmetrical concave-concave resonator is used and this structure helps the mode volume to be nearly fixed when the pulse repetition rate is increased. According to the experimental results in the Q-switched operation, the laser output energy is nearly constant around 70 mJ with an FWHM pulse width of 7 ns at 100 Hz. The optical-to-optical conversion efficiency in the Q-switched regime is 17.5%.

Nonlinear optical and light emission studies of special organic molecules and crystals

NASA Astrophysics Data System (ADS)

Bhowmik, Achintya K.

The nonlinear optical properties and light emission characteristics of some special organic molecules and crystals have been studied in detail. The second-order nonlinear optical effects were measured in the single- crystal films of the materials. The crystallographic orientations of the films were determined using x-ray diffraction measurements. The second-order susceptibility tensor elements of 4-aminobenzophenone (ABP) and 8- (4'-acetylphenyl)-1,4-dioxa-8- azaspiro[4.5]decane (APDA) films were measured using polarization selective second-harmonic generation experiments. The d-coefficients of ABP are: d 23 = 7.3 +/- 0.4 pm/V and d22 = 0.73 +/- 0.04 pm/V, while those of APDA are: d33 = 54 +/- 6 pm/V and d15 = 18 +/- 3 pm/V at 1064 nm. Phase-matched propagation directions were identified on the films. The application of these films in measuring ultra-short laser pulse-width was demonstrated. Polarized optical absorption and photo- luminescence were measured in 4'- dimethylamino-N-methyl-4-stilbazolium tosylate (DAST). The electro-optic properties of single- crystal films of DAST and styryl pyridinium cyanine dye (SPCD) were studied over a broad range of wavelengths. The measured r-coefficients are the largest reported in any material. Thin-film electro-optic modulators were demonstrated using these films which have insignificant insertion and propagation losses compared to the traditional waveguide based devices. The response was observed to be flat over the measured frequency range (2 kHz-100 MHz), which indicates the origin of the electro-optic effect to be predominantly electronic. Thus these materials have significant potential for applications in high-speed optical signal processing. Spectral broadening of femtosecond laser pulses in poly- [2,4 hexadiyne-1,6 diol-bis-(p-toluene sulfonate)] (PTS) single-crystals due to self-phase modulation was studied. The magnitudes of the nonlinear refractive index were determined over the wavelength range of 720-1064 nm. The two-photon absorption spectrum, determined from nonlinear transmission measurements, was observed to have no discernible influence on the dispersion of the nonlinear index at these wavelengths. Highly efficient spectrally narrowed emission has been observed for the first time in strongly dipolar organic salts based on the stilbazolium chromophore. An unusually high conversion efficiency (40%) with a low excitation threshold (<1 μJ) has been observed despite a very low photoluminescence efficiency (~0.3%). The results are explained in terms of cooperative emission upon short-pulse optical excitation. These materials have a wide range of potential applications in photonics, including frequency conversion, high-speed electro-optic modulation, sensors, and novel laser-like light sources.

Optical frequency comb based multi-band microwave frequency conversion for satellite applications.

PubMed

Yang, Xinwu; Xu, Kun; Yin, Jie; Dai, Yitang; Yin, Feifei; Li, Jianqiang; Lu, Hua; Liu, Tao; Ji, Yuefeng

2014-01-13

Based on optical frequency combs (OFC), we propose an efficient and flexible multi-band frequency conversion scheme for satellite repeater applications. The underlying principle is to mix dual coherent OFCs with one of which carrying the input signal. By optically channelizing the mixed OFCs, the converted signal in different bands can be obtained in different channels. Alternatively, the scheme can be configured to generate multi-band local oscillators (LO) for widely distribution. Moreover, the scheme realizes simultaneous inter- and intra-band frequency conversion just in a single structure and needs only three frequency-fixed microwave sources. We carry out a proof of concept experiment in which multiple LOs with 2 GHz, 10 GHz, 18 GHz, and 26 GHz are generated. A C-band signal of 6.1 GHz input to the proposed scheme is successfully converted to 4.1 GHz (C band), 3.9 GHz (C band) and 11.9 GHz (X band), etc. Compared with the back-to-back (B2B) case measured at 0 dBm input power, the proposed scheme shows a 9.3% error vector magnitude (EVM) degradation at each output channel. Furthermore, all channels satisfy the EVM limit in a very wide input power range.

Hybrid silicon–carbon nanostructures for broadband optical absorption

DOE PAGES

Yang, Wen -Hua; Lu, Wen -Cai; Ho, K. M.; ...

2017-01-25

Proper design of nanomaterials for broadband light absorption is a key factor for improving the conversion efficiency of solar cells. Here we present a hybrid design of silicon–carbon nanostructures with silicon clusters coated by carbon cages, i.e., Si m@C 2n for potential solar cell application. The optical properties of these hybrid nanostructures were calculated based on time dependent density function theory (TDDFT). The results show that the optical spectra of Si m@C 2n are very different from those of pure Si m and C 2n clusters. While the absorption spectra of pure carbon cages and Si m clusters exhibit peaksmore » in the UV region, those of the Si m@C 2n nanostructures exhibit a significant red shift. Superposition of the optical spectra of various Si m@C 2n nanostructures forms a broad-band absorption, which extends to the visible light and infrared regions. As a result, the broadband adsorption of the assembled Si m@C 2n nanoclusters may provide a new approach for the design of high efficiency solar cell nanomaterials.« less

Suppressed power saturation due to optimized optical confinement in 9xx nm high-power diode lasers that use extreme double asymmetric vertical designs

NASA Astrophysics Data System (ADS)

Kaul, T.; Erbert, G.; Maaßdorf, A.; Knigge, S.; Crump, P.

2018-03-01

Broad area lasers with novel extreme double asymmetric structure (EDAS) vertical designs featuring increased optical confinement in the quantum well, Γ, are shown to have improved temperature stability without compromising series resistance, internal efficiency or losses. Specifically, we present here vertical design considerations for the improved continuous wave (CW) performance of devices operating at 940 nm, based on systematically increasing Γ from 0.26% to 1.1%, and discuss the impact on power saturation mechanisms. The results indicate that key power saturation mechanisms at high temperatures originate in high threshold carrier densities, which arise in the quantum well at low Γ. The characteristic temperatures, T 0 and T 1, are determined under short pulse conditions and are used to clarify the thermal contribution to power limiting mechanisms. Although increased Γ reduces thermal power saturation, it is accompanied by increased optical absorption losses in the active region, which has a significant impact on the differential external quantum efficiency, {η }{{diff}}. To quantify the impact of internal optical losses contributed by the quantum well, a resonator length-dependent simulation of {η }{{diff}} is performed and compared to the experiment, which also allows the estimation of experimental values for the light absorption cross sections of electrons and holes inside the quantum well. Overall, the analysis enables vertical designs to be developed, for devices with maximized power conversion efficiency at high CW optical power and high temperatures, in a trade-off between absorption in the well and power saturation. The best balance to date is achieved in devices using EDAS designs with {{Γ }}=0.54 % , which deliver efficiencies of 50% at 14 W optical output power at an elevated junction temperature of 105 °C.

Optical readout of displacements of nanowires along two mutually perpendicular directions

NASA Astrophysics Data System (ADS)

Fu, Chenghua

2017-05-01

Nanowires are good force transducers due to their low mass. The singleness of the direction of the motion detection in a certain system is an existing limitation, and to overcome the limitation is the key point in this article. Optical methods, such as polarized light interferometry and light scattering, are generally used for detecting the displacement of nanowires. Typically, either light interference or light scattering is considered when relating the displacement of a nanowire with the photodetector's measurements. In this work, we consider both the light interference along the optical axis and light scattering perpendicular to the optical axis of a micro-lens fiber optic interferometer. Identifying the displacement along the two directions and the corresponding vibration conversion efficiency coefficients for the nanowire is a significant part of our study. Our analysis shows that the optimal working point of the micro-lens fiber optic interferometer can realize the detection of displacement along the optical axis without the disturbance coming from the motion perpendicular to the optical axis, and vice versa. We use Mie scattering theory to calculate the scattering light for the reason that the size of the nanowire is comparable to the wavelength of light. Our results could provide a guide for optical readout experiments of the displacement of nanowires.

Biocular vehicle display optical designs

NASA Astrophysics Data System (ADS)

Chu, H.; Carter, Tom

2012-06-01

Biocular vehicle display optics is a fast collimating lens (f / # < 0.9) that presents the image of the display at infinity to both eyes of the viewer. Each eye captures the scene independently and the brain merges the two images into one through the overlapping portions of the images. With the recent conversion from analog CRT based displays to lighter, more compact active-matrix organic light-emitting diodes (AMOLED) digital image sources, display optical designs have evolved to take advantage of the higher resolution AMOLED image sources. To maximize the field of view of the display optics and fully resolve the smaller pixels, the digital image source is pre-magnified by relay optics or a coherent taper fiber optics plate. Coherent taper fiber optics plates are used extensively to: 1. Convert plano focal planes to spherical focal planes in order to eliminate Petzval field curvature. This elimination enables faster lens speed and/or larger field of view of eye pieces, display optics. 2. Provide pre-magnification to lighten the work load of the optics to further increase the numerical aperture and/or field of view. 3. Improve light flux collection efficiency and field of view by collecting all the light emitted by the image source and guiding imaging light bundles toward the lens aperture stop. 4. Reduce complexity of the optical design and overall packaging volume by replacing pre-magnification optics with a compact taper fiber optics plate. This paper will review and compare the performance of biocular vehicle display designs without and with taper fiber optics plate.

Optical Energy Transfer and Conversion System

NASA Technical Reports Server (NTRS)

Hogan, Bartholomew P. (Inventor); Stone, William C. (Inventor)

2018-01-01

An optical energy transfer and conversion system comprising a fiber spooler and an electrical power extraction subsystem connected to the spooler with an optical waveguide. Optical energy is generated at and transferred from a base station through fiber wrapped around the spooler, and ultimately to the power extraction system at a remote mobility platform for conversion to another form of energy. The fiber spooler may reside on the remote mobility platform which may be a vehicle, or apparatus that is either self-propelled or is carried by a secondary mobility platform either on land, under the sea, in the air or in space.

Optical Scanning for Retrospective Conversion of Information.

ERIC Educational Resources Information Center

Hein, Morten

1986-01-01

This discussion of the use of optical scanning and computer formatting for retrospective conversion focuses on a series of applications known as Optical Scanning for Creation of Information Databases (OSCID). Prior research in this area and the usefulness of OSCID for creating low-priced machine-readable data representing older materials are…

Midinfrared wavelength conversion in hydrogenated amorphous silicon waveguides

NASA Astrophysics Data System (ADS)

Wang, Jiang; Wang, Zhaolu; Huang, Nan; Han, Jing; Li, Yongfang; Liu, Hongjun

2017-10-01

Midinfrared (MIR) wavelength conversion based on degenerate four-wave mixing is theoretically investigated in hydrogenated amorphous silicon (a-Si:H) waveguides. The broadband phase mismatch is achieved in the normal group-velocity dispersion regime. The conversion bandwidth is extended to 900 nm, and conversion efficiency of up to -14 dB with a pump power of 70 mW in a 2-mm long a-Si:H rib waveguides is obtained. This low-power on-chip wavelength converter will have potential for application in a wide range of MIR nonlinear optic devices.

High-efficiency diode-pumped actively Q-switched ceramic Nd:YAG/BaWO₄ Raman laser operating at 1666 nm.

PubMed

Zhang, H N; Chen, X H; Wang, Q P; Zhang, X Y; Chang, J; Gao, L; Shen, H B; Cong, Z H; Liu, Z J; Tao, X T; Li, P

2014-05-01

A diode-pumped actively Q-switched Raman laser employing BaWO4 as the Raman active medium and a ceramic Nd:YAG laser operating at 1444 nm as the pump source is demonstrated. The first-Stokes-Raman generation at 1666 nm is achieved. With a pump power of 20.3 W and pulse repetition frequency rate of 5 kHz, a maximum output power of 1.21 W is obtained, which is the highest output power for a 1.6 μm Raman laser. The corresponding optical-to-optical conversion efficiency is 6%; the pulse energy and peak power are 242 μJ and 8.96 kW, respectively.

Passively mode-locked pulse generation in a c-cut Nd:LuVO4 laser at 1086 nm with a semiconductor saturable-absorber mirror

NASA Astrophysics Data System (ADS)

Lin, Ja-Hon; Yang, Pao-Keng; Lin, Wei-Cheng

2012-04-01

We demonstrate a diode-pumped passively mode-locked (ML) c-cut Nd:LuVO4 laser with central wavelength at 1086 nm by shifting the reflectance band of the SESAM into a longer wavelength to result in larger loss around 1068 nm. At 15 W absorbed pump power, the highest output power of the ML pulse was about 2.6 W that corresponded to the 17.3% optical-to-optical conversion efficiency and the slope efficiency of laser was about 22.9%. Using our ML laser as the light source, we have also successfully measured the saturation fluence of the SESAM at 1086 nm.

Highly efficient quantum dot-based photoconductive THz materials and devices

NASA Astrophysics Data System (ADS)

Rafailov, E. U.; Leyman, R.; Carnegie, D.; Bazieva, N.

2013-09-01

We demonstrate Terahertz (THz) signal sources based on photoconductive (PC) antenna devices comprising active layers of InAs semiconductor quantum dots (QDs) on GaAs. Antenna structures comprised of multiple active layers of InAs:GaAs PC materials are optically pumped using ultrashort pulses generated by a Ti:Sapphire laser and CW dualwavelength laser diodes. We also characterised THz output signals using a two-antenna coherent detection system. We discuss preliminary performance data from such InAs:GaAs THz devices which exhibit efficient emission of both pulsed and continuous wave (CW) THz signals and significant optical-to-THz conversion at both absorption wavelength ranges, <=850 nm and <=1300 nm.

H2RG Detector Characterization for RIMAS and Instrument Efficiencies

NASA Technical Reports Server (NTRS)

Toy, Vicki L.; Kutyrev, Alexander S.; Capone, John I.; Hams, Thomas; Robinson, F. David; Lotkin, Gennadiy N.; Veilleux, Sylvain; Moseley, Samuel H.; Gehrels, Neil A.; Vogel, Stuart N.

2016-01-01

The Rapid infrared IMAger-Spectrometer (RIMAS) is a near-infrared (NIR) imager and spectrometer that will quickly follow up gamma-ray burst afterglows on the 4.3-meter Discovery Channel Telescope (DCT). RIMAS has two optical arms which allows simultaneous coverage over two bandpasses (YJ and HK) in either imaging or spectroscopy mode. RIMAS utilizes two Teledyne HgCdTe H2RG detectors controlled by Astronomical Research Cameras, Inc. (ARC/Leach) drivers. We report the laboratory characterization of RIMAS's detectors: conversion gain, read noise, linearity, saturation, dynamic range, and dark current. We also present RIMAS's instrument efficiency from atmospheric transmission models and optics data (both telescope and instrument) in all three observing modes.

Micro-Welding of Copper Plate by Frequency Doubled Diode Pumped Pulsed Nd:YAG Laser

NASA Astrophysics Data System (ADS)

Nakashiba, Shin-Ichi; Okamoto, Yasuhiro; Sakagawa, Tomokazu; Takai, Sunao; Okada, Akira

A pulsed laser of 532 nm wavelength with ms range pulse duration was newly developed by second harmonic generation of diode pumped pulsed Nd:YAG laser. High electro-optical conversion efficiency more than 13% could be achieved, and 1.5 kW peak power green laser pulse was put in optical fiber of 100 μm in diameter. In micro- welding of 1.0 mm thickness copper plate, a keyhole welding was successfully performed by 1.0 kW peak power at spot diameter less than 200 μm. The frequency doubled pulsed laser improved the processing efficiency of copper welding, and narrow and deep weld bead was stably obtained.

E-beam deposited Ag-nanoparticles plasmonic organic solar cell and its absorption enhancement analysis using FDTD-based cylindrical nano-particle optical model.

PubMed

Kim, Richard S; Zhu, Jinfeng; Park, Jeung Hun; Li, Lu; Yu, Zhibin; Shen, Huajun; Xue, Mei; Wang, Kang L; Park, Gyechoon; Anderson, Timothy J; Pei, Qibing

2012-06-04

We report the plasmon-assisted photocurrent enhancement in Ag-nanoparticles (Ag-NPs) embedded PEDOT:PSS/P3HT:PCBM organic solar cells, and systematically investigate the causes of the improved optical absorption based on a cylindrical Ag-NPs optical model which is simulated with a 3-Dimensional finite difference time domain (FDTD) method. The proposed cylindrical Ag-NPs optical model is able to explain the optical absorption enhancement by the localized surface plasmon resonance (LSPR) modes, and to provide a further understanding of Ag-NPs shape parameters which play an important role to determine the broadband absorption phenomena in plasmonic organic solar cells. A significant increase in the power conversion efficiency (PCE) of the plasmonic solar cell was experimentally observed and compared with that of the solar cells without Ag-NPs. Finally, our conclusion was made after briefly discussing the electrical effects of the fabricated plasmonic organic solar cells.

On the use of photothermal techniques for the characterization of solar-selective coatings

NASA Astrophysics Data System (ADS)

Ramírez-Rincón, J. A.; Ares-Muzio, O.; Macias, J. D.; Estrella-Gutiérrez, M. A.; Lizama-Tzec, F. I.; Oskam, G.; Alvarado-Gil, J. J.

2018-03-01

The efficiency of the conversion of solar energy into thermal energy is determined by the optical and thermal properties of the selective coating, in particular, the solar absorptance and thermal emittance at the desired temperature of the specific application. Photothermal techniques are the most appropriate methods to explore these properties, however, a quantitative determination using photothermal radiometry, which is based on the measurement of emitted radiation caused by the heating generated by a modulated light source, has proven to be elusive. In this work, we present experimental results for selective coatings based on electrodeposited black nickel-nickel on both stainless steel and copper substrates, as well as for commercial TiNOX coatings on aluminum, illustrating that the radiation emitted by the surface depends on the optical absorption, thermal emissivity and on the light-into-heat energy conversion efficiency (quantum efficiency). We show that a combination of photothermal radiometry and photoacoustic spectroscopy can successfully account for these parameters, and provide values for the emissivity in agreement with values obtained by Fourier-transform infrared spectroscopy.

Photonic-Assisted mm-Wave and THz Wireless Transmission towards 100 Gbit/s Data Rate

NASA Astrophysics Data System (ADS)

Freire Hermelo, Maria; Chuenchom, Rattana; Rymanov, Vitaly; Kaiser, Thomas; Sheikh, Fawad; Czylwik, Andreas; Stöhr, Andreas

2017-09-01

This paper presents photonic-assisted 60 GHz mm-wave and 325 GHz system approaches that enable the transmission of spectral-efficient and high data rate signals over fiber and over air. First, we focus on generic channel characteristics within the mm-wave 60 GHz band and at the terahertz (THz) band around 325 GHz. Next, for generating the high data rate baseband signals, we present a technical solution for constructing an extreme bandwidth arbitrary waveform generator (AWG). We then report the development of a novel coherent photonic mixer (CPX) module for direct optic-to-RF conversion of extreme wideband optical signals, with a>5 dB higher conversion gain compared to conventional photodiodes. Finally, we experimentally demonstrate record spectral efficient wireless transmission for both bands. The achieved spectral efficiencies reach 10 bit/s/Hz for the 60 GHz band and 6 bit/s/Hz for the 325 GHz band. The maximum data rate transmitted at THz frequencies in the 325 GHz band is 59 Gbit/s using a 64-QAM-OFDM modulation format and a 10 GHz wide data signal.

Sub-nanosecond periodically poled lithium niobate optical parametric generator and amplifier pumped by an actively Q-switched diode-pumped Nd:YAG microlaser

NASA Astrophysics Data System (ADS)

Liu, L.; Wang, H. Y.; Ning, Y.; Shen, C.; Si, L.; Yang, Y.; Bao, Q. L.; Ren, G.

2017-05-01

A sub-nanosecond seeded optical parametric generator (OPG) based on magnesium oxide-doped periodically poled lithium niobate (MgO:PPLN) crystal is presented. Pumped by an actively Q-switched diode-pumped 1 kHz, 1064 nm, Nd:YAG microlaser and seeded with a low power distributed feedback (DFB) diode continuous-wave (CW) laser, the OPG generated an output energy of 41.4 µJ and 681 ps pulse duration for the signal at 1652.4 nm, achieving a quantum conversion efficiency of 61.2% and a slope efficiency of 41.8%. Signal tuning was achieved from 1651.0 to 1652.4 nm by tuning the seed-laser current. The FWHM of the signal spectrum was approximately from 35 nm to 0.5 nm by injection seed laser. The SHG doubled the frequency of OPG signal to produce a output energy of 12 µJ with the energy conversion efficiency of 29.0% and tunanble wavelength near 826 nm.

Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO2-ZrO2 nanocomposite

NASA Astrophysics Data System (ADS)

Tomar, Laxmi J.; Bhatt, Piyush J.; Desai, Rahul K.; Chakrabarty, B. S.; Panchal, C. J.

2016-05-01

TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X -ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphite coated conducting glass plate was used as counter electrode. The I - V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO2, TiO2-ZrO2 and Zn doped TiO2-ZrO2 nanocomposites were found 0.71%, 1.97% and 4.58% respectively.

Scalable UWB photonic generator based on the combination of doublet pulses.

PubMed

Moreno, Vanessa; Rius, Manuel; Mora, José; Muriel, Miguel A; Capmany, José

2014-06-30

We propose and experimentally demonstrate a scalable and reconfigurable optical scheme to generate high order UWB pulses. Firstly, various ultra wideband doublets are created through a process of phase-to-intensity conversion by means of a phase modulation and a dispersive media. In a second stage, doublets are combined in an optical processing unit that allows the reconfiguration of UWB high order pulses. Experimental results both in time and frequency domains are presented showing good performance related to the fractional bandwidth and spectral efficiency parameters.

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S.; De Ceglia, Domenico; Liu, Sheng

We demonstrate, through our experimentation, efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10 -6 is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. Furthermore, this nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Enhanced third harmonic generation from the epsilon-near-zero modes of ultrathin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luk, Ting S., E-mail: tsluk@sandia.gov; Liu, Sheng; Campione, Salvatore

We experimentally demonstrate efficient third harmonic generation from an indium tin oxide nanofilm (λ/42 thick) on a glass substrate for a pump wavelength of 1.4 μm. A conversion efficiency of 3.3 × 10{sup −6} is achieved by exploiting the field enhancement properties of the epsilon-near-zero mode with an enhancement factor of 200. This nanoscale frequency conversion method is applicable to other plasmonic materials and reststrahlen materials in proximity of the longitudinal optical phonon frequencies.

Optical Sidebands Multiplier

NASA Technical Reports Server (NTRS)

Strekalov, Dmitry V.; Yu, Nan

2010-01-01

Optical sidebands have been generated with relative frequency tens to hundreds of GHz by using optical sidebands that are generated in a cascade process in high-quality optical resonators with Kerr nonlinearity, such as whispering gallery mode (WGM) resonators. For this purpose, the WGM resonator needs to be optically pumped at two frequencies matching its resonances. These two optical components can be one or several free spectral ranges (FSRs), equal to approximately 12 GHz, in this example, apart from each other, and can be easily derived from a monochromatic pump with an ordinary EOM (electro-optic modulation) operating at half the FSR frequency. With sufficient nonlinearity, an optical cascade process will convert the two pump frequencies into a comb-like structure extending many FSRs around the carrier frequency. This has a demonstratively efficient frequency conversion of this type with only a few milliwatt optical pump power. The concept of using Kerr nonlinearity in a resonator for non-degenerate wave mixing has been discussed before, but it was a common belief that this was a weak process requiring very high peak powers to be observable. It was not thought possible for this approach to compete with electro-optical modulators in CW applications, especially those at lower optical powers. By using the high-Q WGM resonators, the effective Kerr nonlinearity can be made so high that, using even weak seeding bands available from a conventional EOM, one can effectively multiply the optical sidebands, extending them into an otherwise inaccessible frequency range.

Efficient quantum computing using coherent photon conversion.

PubMed

Langford, N K; Ramelow, S; Prevedel, R; Munro, W J; Milburn, G J; Zeilinger, A

2011-10-12

Single photons are excellent quantum information carriers: they were used in the earliest demonstrations of entanglement and in the production of the highest-quality entanglement reported so far. However, current schemes for preparing, processing and measuring them are inefficient. For example, down-conversion provides heralded, but randomly timed, single photons, and linear optics gates are inherently probabilistic. Here we introduce a deterministic process--coherent photon conversion (CPC)--that provides a new way to generate and process complex, multiquanta states for photonic quantum information applications. The technique uses classically pumped nonlinearities to induce coherent oscillations between orthogonal states of multiple quantum excitations. One example of CPC, based on a pumped four-wave-mixing interaction, is shown to yield a single, versatile process that provides a full set of photonic quantum processing tools. This set satisfies the DiVincenzo criteria for a scalable quantum computing architecture, including deterministic multiqubit entanglement gates (based on a novel form of photon-photon interaction), high-quality heralded single- and multiphoton states free from higher-order imperfections, and robust, high-efficiency detection. It can also be used to produce heralded multiphoton entanglement, create optically switchable quantum circuits and implement an improved form of down-conversion with reduced higher-order effects. Such tools are valuable building blocks for many quantum-enabled technologies. Finally, using photonic crystal fibres we experimentally demonstrate quantum correlations arising from a four-colour nonlinear process suitable for CPC and use these measurements to study the feasibility of reaching the deterministic regime with current technology. Our scheme, which is based on interacting bosonic fields, is not restricted to optical systems but could also be implemented in optomechanical, electromechanical and superconducting systems with extremely strong intrinsic nonlinearities. Furthermore, exploiting higher-order nonlinearities with multiple pump fields yields a mechanism for multiparty mediation of the complex, coherent dynamics.

Photonic generation of ultra-wide-band doublet pulse through monolithic integration of tapered directional coupler and quantum well waveguide.

PubMed

Kuo, Yu-Zheng; Wu, Jui-Pin; Wu, Tsu-Hsiu; Chiu, Yi-Jen

2012-10-22

We proposed and demonstrated a novel scheme of photonic ultra-wide-band (UWB) doublet pulse based on monolithic integration of tapered optical-direction coupler (TODC) and multiple-quantum-well (MQW) waveguide. TODC is formed by a top tapered MQW waveguide vertically integrating with an underneath passive waveguide. Through simultaneous field-driven optical index- and absorption- change in MQW, the partial optical coupling in TODC can be used to get a valley-shaped of optical transmission against voltage. Therefore, doublet-enveloped optical pulse can be realized by high-speed and high-efficient conversion of input electrical pulse. By just adjusting bias through MQW, 1530 nm photonic UWB doublet optical pulse with 75-ps pulse width, below -41.3 dBm power, 125% fractional bandwidth, and 7.5 GHz of -10 dB bandwidth has been demonstrated, fitted into FCC requirement (3.1 GHz~10.6 GHz). Doublet-pulse data transmission generated in optical fiber is also performed for further characterization, exhibiting a successful 1.25 Gb/s error-free transmission. It suggests such optoelectronic integration template can be applied for photonic UWB generation in fiber-based communications.

Ground Demonstration of Planetary Gas Lidar Based on Optical Parametric Amplifier

NASA Technical Reports Server (NTRS)

Numata, Kenji; Riris, Haris; Li, Steve; Wu, Stewart; Kawa, Stephen R.; Krainak, Michael; Abshire, James

2012-01-01

We report on the development effort of a nanosecond-pulsed optical parametric amplifier (OPA) for remote trace gas measurements for Mars and Earth. The OPA output has high spectral purity and is widely tunable both at near-infrared and mid-infrared wavelengths, with an optical-optica1 conversion efficiency of up to approx 39 %. Using this laser source, we demonstrated open-path measurements of CH4 (3291 nm and 1651 nm), CO2 (1573 nm), H2O (1652 nm), and CO (4764 nm) on the ground. The simplicity, tunability. and power scalability of the OPA make it a strong candidate for general planetary lidar instruments, which will offer important information on the origins of the planet's geology, atmosphere, and potential for biology,

High-power 266 nm ultraviolet generation in yttrium aluminum borate.

PubMed

Liu, Qiang; Yan, Xingpeng; Gong, Mali; Liu, Hua; Zhang, Ge; Ye, Ning

2011-07-15

A yttrium aluminum borate [YAl(3)(BO(3))(4)] (YAB) crystal with UV cutoff wavelength of 165 nm is used as the nonlinear optical crystal for fourth harmonic generation. The fundamental frequency laser at 1064 nm from an Nd:YVO(4) master oscillator power amplifier laser was frequency doubled to 532 nm. Using the type I phase-matching YAB crystal, a 5.05 W average power 266 nm UV laser was obtained at the pulse repetition frequency of 65 kHz, corresponding to the conversion efficiency of 12.3% from 532 to 266 nm. The experimental results show great potential for the application of using YAB as a nonlinear optical crystal to get high-power fourth harmonic generation. © 2011 Optical Society of America

Self-reverse-biased solar panel optical receiver for simultaneous visible light communication and energy harvesting.

PubMed

Shin, Won-Ho; Yang, Se-Hoon; Kwon, Do-Hoon; Han, Sang-Kook

2016-10-31

We propose a self-reverse-biased solar panel optical receiver for energy harvesting and visible light communication. Since the solar panel converts an optical component into an electrical component, it provides both energy harvesting and communication. The signal component can be separated from the direct current component, and these components are used for communication and energy harvesting. We employed a self-reverse-biased receiver circuit to improve the communication and energy harvesting performance. The reverse bias on the solar panel improves the responsivity and response time. The proposed system achieved 17.05 mbps discrete multitone transmission with a bit error rate of 1.1 x 10^-3 and enhanced solar energy conversion efficiency.

INTEGRATED AND FIBER OPTICS: Threshold of photoinduced conversion of the polarization of radiation in lithium niobate optical waveguides

NASA Astrophysics Data System (ADS)

Kazanskiĭ, P. G.

1989-02-01

A threshold of photoinduced conversion of an ordinary wave into an extraordinary one was discovered for lithium niobate optical waveguides. The threshold intensity of the radiation was determined for waveguides prepared under different conditions. The experimental results were compared with theoretical estimates.

Characteristics of optical parametric oscillator synchronously pumped by Yb:KGW laser and based on periodically poled potassium titanyl phosphate crystal

NASA Astrophysics Data System (ADS)

Vengelis, Julius; Tumas, Adomas; Pipinytė, Ieva; Kuliešaitė, Miglė; Tamulienė, Viktorija; Jarutis, Vygandas; Grigonis, Rimantas; Sirutkaitis, Valdas

2018-03-01

We present experimental data and numerical simulation results obtained during investigation of synchronously pumped optical parametric oscillator (SPOPO) pumped by femtosecond Yb:KGW laser (central wavelength at 1033 nm). The nonlinear medium for parametric generation was periodically poled potassium titanyl phosphate crystal (PPKTP). Maximum parametric light conversion efficiency from pump power to signal power was more than 37.5% at λs=1530 nm wavelength, whereas the achieved signal wave continuous tuning range was from 1470 nm to 1970 nm with signal pulse durations ranging from 91 fs to roughly 280 fs. We demonstrated wavelength tuning by changing cavity length and PPKTP crystal grating period and also discussed net cavity group delay dispersion (GDD) influence on SPOPO output radiation characteristics. The achieved high pump to signal conversion efficiency and easy wavelength tuning make this device a very promising alternative to Ti:sapphire based SPOPOs as a source of continuously tunable femtosecond laser radiation in the near and mid-IR range.

Dynamic tuning of optical absorbers for accelerated solar-thermal energy storage.

PubMed

Wang, Zhongyong; Tong, Zhen; Ye, Qinxian; Hu, Hang; Nie, Xiao; Yan, Chen; Shang, Wen; Song, Chengyi; Wu, Jianbo; Wang, Jun; Bao, Hua; Tao, Peng; Deng, Tao

2017-11-14

Currently, solar-thermal energy storage within phase-change materials relies on adding high thermal-conductivity fillers to improve the thermal-diffusion-based charging rate, which often leads to limited enhancement of charging speed and sacrificed energy storage capacity. Here we report the exploration of a magnetically enhanced photon-transport-based charging approach, which enables the dynamic tuning of the distribution of optical absorbers dispersed within phase-change materials, to simultaneously achieve fast charging rates, large phase-change enthalpy, and high solar-thermal energy conversion efficiency. Compared with conventional thermal charging, the optical charging strategy improves the charging rate by more than 270% and triples the amount of overall stored thermal energy. This superior performance results from the distinct step-by-step photon-transport charging mechanism and the increased latent heat storage through magnetic manipulation of the dynamic distribution of optical absorbers.

Uni-directional optical pulses, temporal propagation, and spatial and temporal dispersion

NASA Astrophysics Data System (ADS)

Kinsler, P.

2018-02-01

I derive a temporally propagated uni-directional optical pulse equation valid in the few cycle limit. Temporal propagation is advantageous because it naturally preserves causality, unlike the competing spatially propagated models. The exact coupled bi-directional equations that this approach generates can be efficiently approximated down to a uni-directional form in cases where an optical pulse changes little over one optical cycle. They also permit a direct term-to-term comparison of the exact bi-directional theory with its corresponding approximate uni-directional theory. Notably, temporal propagation handles dispersion in a different way, and this difference serves to highlight existing approximations inherent in spatially propagated treatments of dispersion. Accordingly, I emphasise the need for future work in clarifying the limitations of the dispersion conversion required by these types of approaches; since the only alternative in the few cycle limit may be to resort to the much more computationally intensive full Maxwell equation solvers.

Dual-tone optical vector millimeter wave signal generated by frequency-nonupling the radio frequency 16-star quadrature-amplitude-modulation signal

NASA Astrophysics Data System (ADS)

Wu, Tonggen; Ma, Jianxin

2017-12-01

This paper proposes an original scheme to generate the photonic dual-tone optical millimeter wave (MMW) carrying the 16-star quadrature-amplitude-modulation (QAM) signal via an optical phase modulator (PM) and an interleaver with adaptive photonic frequency-nonupling without phase precoding. To enable the generated optical vector MMW signal to resist the power fading effect caused by the fiber chromatic dispersion, the modulated -5th- and +4th-order sidebands are selected from the output of the PM, which is driven by the precoding 16-star QAM signal. The modulation index of the PM is optimized to gain the maximum opto-electrical conversion efficiency. A radio over fiber link is built by simulation, and the simulated constellations and the bit error rate graph demonstrate that the frequency-nonupling 16-star QAM MMW signal has good transmission performance. The simulation results agree well with our theoretical results.

Luminescent characteristics study of Mather-type dense plasma focus and applications to short-wavelength optical pumping. Final technical report, 1 May 1984-30 September 1985

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, K.K.

A Mather-type dense plasma focus (MDPF) system was designed, built, and tested specifically to study its luminescent characteristics and to assess its potential as a new light source of high-energy, short-wavelength lasers. The luminescence study of MDPF showed that the conversion efficiency from the electrical input to the optical output energies is at least 50%, up to the time the plasma compression is complete. Using the system, for the first time as an optical pump, laser activities were successfully obtained from a variety of liquid organic dyes. Diagnostic capabilities included an optical multichannel analyzer system complete with a computer control,more » a nitrogen-pumped tunable dye-laser system, a high-speed streak/framing camera, a digital laser energy meter, voltage and current probes, and a computer-based data-acquisition system.« less

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler.

PubMed

Kardaś, Tomasz M; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-22

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Full 3D modelling of pulse propagation enables efficient nonlinear frequency conversion with low energy laser pulses in a single-element tripler

NASA Astrophysics Data System (ADS)

Kardaś, Tomasz M.; Nejbauer, Michał; Wnuk, Paweł; Resan, Bojan; Radzewicz, Czesław; Wasylczyk, Piotr

2017-02-01

Although new optical materials continue to open up access to more and more wavelength bands where femtosecond laser pulses can be generated, light frequency conversion techniques are still indispensable in filling the gaps on the ultrafast spectral scale. With high repetition rate, low pulse energy laser sources (oscillators) tight focusing is necessary for a robust wave mixing and the efficiency of broadband nonlinear conversion is limited by diffraction as well as spatial and temporal walk-off. Here we demonstrate a miniature third harmonic generator (tripler) with conversion efficiency exceeding 30%, producing 246 fs UV pulses via cascaded second order processes within a single laser beam focus. Designing this highly efficient and ultra compact frequency converter was made possible by full 3-dimentional modelling of propagation of tightly focused, broadband light fields in nonlinear and birefringent media.

Cysteine optical sensing with an up-conversion host and two chemosensors derived from rhodamine: Construction, characterization and performance

NASA Astrophysics Data System (ADS)

Lin, Chen; Zhigang, Fang

2017-03-01

This paper focused on two rhodamine chemosensors for cysteine optical sensing. To minimize their photobleaching caused by excitation light, up-conversion NaYF4:Yb3 +/Er3 + nanocrystals were prepared and used as excitation host. Photophysical measurement on this host and the two chemosensors suggested that chemosensor absorption matched well with host emission. An efficient energy transfer between them was discussed and confirmed by their spectral analysis and emission lifetime comparison. Job's plot suggested that our chemosensors followed a simple recognition mechanism towards cysteine with binding stoichiometry of 1:1. Both chemosensors showed emission "off-on" effect triggered by cysteine and good photostability. Linear working curves with maximum sensitivity of 2.61 were obtained. S substituent was positive to improve selectivity.

Reversed Cherenkov emission of terahertz waves from an ultrashort laser pulse in a sandwich structure with nonlinear core and left-handed cladding.

PubMed

Bakunov, M I; Mikhaylovskiy, R V; Bodrov, S B; Luk'yanchuk, B S

2010-01-18

We propose a scheme for an experimental verification of the reversed Cherenkov effect in left-handed media. The scheme uses optical-to-terahertz conversion in a planar sandwichlike structure that consists of a nonlinear core cladded with a material that exhibits left-handedness at terahertz frequencies. The focused into a line femtosecond laser pulse propagates in the core and emits Cherenkov wedge of terahertz waves in the cladding. We developed a theory that describes terahertz generation in such a structure and calculated spatial distribution of the generated terahertz field, its energy spectrum, and optical-to-terahertz conversion efficiency. The proposed structure can be a useful tool for characterization of the electromagnetic properties of metamaterials in the terahertz frequency range.

Dual-pumped nondegenerate four-wave mixing in semiconductor laser with a built-in external cavity

NASA Astrophysics Data System (ADS)

Wu, Jian-Wei; Qiu, Qi; Hyub Won, Yong

2017-04-01

In this paper, a semiconductor laser system consisting of a conventional multimode Fabry-Pérot laser diode with a built-in external cavity is presented and demonstrated. More than two resonance modes, whose peak levels are significantly higher than other residual modes, are simultaneously supported and output by adjusting the bias current and operating temperature of the active region. Based on this device, dual-pumped nondegenerate four-wave mixing—in which two pump waves and a single signal wave are simultaneously fed into the laser, and the injection power and wavelength of the injected pump and signal waves are changed—is observed and discussed thoroughly. The results show that while the wavelengths of pump wave A and signal wave S are kept constant, the other pump wave B jumps from about 1535 nm to 1578 nm, generating conversion signals with changed wavelengths. The achieved conversion bandwidth between the primary signal and the converted signal waves is broadly tunable in the range of several terahertz frequencies. Both the conversion efficiency and optical signal-to-noise ratio of the newly generated conversion signals are adopted to evaluate the performance of the proposed four-wave mixing process, and are strongly dependent on the wavelength and power of the injected waves. Here, the attained maximum conversion efficiency and optical signal-to-noise ratio are close to -22 dB and 15 dB, respectively.

Broadband High Efficiency Fractal-Like and Diverse Geometry Silicon Nanowire Arrays for Photovoltaic Applications

NASA Astrophysics Data System (ADS)

AL-Zoubi, Omar H.

Solar energy has many advantages over conventional sources of energy. It is abundant, clean and sustainable. One way to convert solar energy directly into electrical energy is by using the photovoltaic solar cells (PVSC). Despite PVSC are becoming economically competitive, they still have high cost and low light to electricity conversion efficiency. Therefore, increasing the efficiency and reducing the cost are key elements for producing economically more competitive PVSC that would have significant impact on energy market and saving environment. A significant percentage of the PVSC cost is due to the materials cost. For that, thin films PVSC have been proposed which offer the benefits of the low amount of material and fabrication costs. Regrettably, thin film PVSC show poor light to electricity conversion efficiency because of many factors especially the high optical losses. To enhance conversion efficiency, numerous techniques have been proposed to reduce the optical losses and to enhance the absorption of light in thin film PVSC. One promising technique is the nanowire (NW) arrays in general and the silicon nanowire (SiNW) arrays in particular. The purpose of this research is to introduce vertically aligned SiNW arrays with enhanced and broadband absorption covering the entire solar spectrum while simultaneously reducing the amount of material used. To this end, we apply new concept for designing SiNW arrays based on employing diversity of physical dimensions, especially radial diversity within certain lattice configurations. In order to study the interaction of light with SiNW arrays and compute their optical properties, electromagnetic numerical modeling is used. A commercial numerical electromagnetic solver software package, high frequency structure simulation (HFSS), is utilized to model the SiNW arrays and to study their optical properties. We studied different geometries factors that affect the optical properties of SiNW arrays. Based on this study, we found that the optical properties of SiNW arrays are strongly affected by the radial diversity, the arrangement of SiNW in a lattice, and the configuration of such lattice. The proper selection of these parameters leads to broaden and enhance the light absorption of the SiNW arrays. Inspired by natural configurations, fractal geometry and diamond lattice structures, we introduced two lattice configurations: fractal-like array (FLA) that is inspired by fractal geometry, and diamond-like array (DLA) that is inspired by diamond crystal lattice structure. Optimization, using parametric analysis, of the introduced arrays parameters for the light absorption level and the amount of used material has been performed. Both of the introduced SiNW arrays show broadband, strong light absorption coupled with reduction of the amount of the used material. DLA in specific showed significantly enhanced absorption covering the entire solar spectrum of interest, where near-unity absorption spectrum could be achieved. We studied the optical properties of complete PVSC devices that are based on SiNW array. Moreover, the performance of PVSC device that is based on SiNW has been investigated by using numerical modeling. SILVACO software package is used for performing the numerical simulation of the PVSC device performance, which can simultaneously handle the different coupled physical mechanisms contributing to the photovoltaic effect. The effect of the geometry of PVSC device that is based on SiNW is investigated, which shows that the geometry of such PVSC has a role in enhancing its electrical properties. The outcome of this study introduces new SiNW array configurations that have enhanced optical properties using a low amount of material that can be utilized for producing higher efficiency thin film PVCS. The overall conclusion of this work is that a weak absorption indirect band gap material, silicon, in the form of properly designed SiNW and SiNC arrays has the potentials to achieve near-unity ideal absorption spectrum using reduced amount of material, which can lead to produce new generation of lower cost and enhanced efficiency thin film PVSC.

Scaling vectors of attoJoule per bit modulators

NASA Astrophysics Data System (ADS)

Sorger, Volker J.; Amin, Rubab; Khurgin, Jacob B.; Ma, Zhizhen; Dalir, Hamed; Khan, Sikandar

2018-01-01

Electro-optic modulation performs the conversion between the electrical and optical domain with applications in data communication for optical interconnects, but also for novel optical computing algorithms such as providing nonlinearity at the output stage of optical perceptrons in neuromorphic analog optical computing. While resembling an optical transistor, the weak light-matter-interaction makes modulators 105 times larger compared to their electronic counterparts. Since the clock frequency for photonics on-chip has a power-overhead sweet-spot around tens of GHz, ultrafast modulation may only be required in long-distance communication, not for short on-chip links. Hence, the search is open for power-efficient on-chip modulators beyond the solutions offered by foundries to date. Here, we show scaling vectors towards atto-Joule per bit efficient modulators on-chip as well as some experimental demonstrations of novel plasmonic modulators with sub-fJ/bit efficiencies. Our parametric study of placing different actively modulated materials into plasmonic versus photonic optical modes shows that 2D materials overcompensate their miniscule modal overlap by their unity-high index change. Furthermore, we reveal that the metal used in plasmonic-based modulators not only serves as an electrical contact, but also enables low electrical series resistances leading to near-ideal capacitors. We then discuss the first experimental demonstration of a photon-plasmon-hybrid graphene-based electro-absorption modulator on silicon. The device shows a sub-1 V steep switching enabled by near-ideal electrostatics delivering a high 0.05 dB V-1 μm-1 performance requiring only 110 aJ/bit. Improving on this demonstration, we discuss a plasmonic slot-based graphene modulator design, where the polarization of the plasmonic mode aligns with graphene’s in-plane dimension; where a push-pull dual-gating scheme enables 2 dB V-1 μm-1 efficient modulation allowing the device to be just 770 nm short for 3 dB small signal modulation. Lastly, comparing the switching energy of transistors to modulators shows that modulators based on emerging materials and plasmonic-silicon hybrid integration perform on-par relative to their electronic counter parts. This in turn allows for a device-enabled two orders-of-magnitude improvement of electrical-optical co-integrated network-on-chips over electronic-only architectures. The latter opens technological opportunities in cognitive computing, dynamic data-driven applications systems, and optical analog computer engines including neuromorphic photonic computing.

10Gbit/s all-optical NRZ to RZ conversion based on TOAD

NASA Astrophysics Data System (ADS)

Yan, Yumei; Yin, Lina; Zhou, Yunfeng; Liu, Guoming; Wu, Jian; Lin, Jintong

2006-01-01

Future network will include wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM) technologies. All-optical format conversion between their respective preferable data formats, non-return-to-zero (NRZ) and return-to-zero (RZ), may become an important technology. In this paper, 10Gbit/s all-optical NRZ-to-RZ conversion is demonstrated based on terahertz optical asymmetric demultiplexer (TOAD) using clock all-optically recovered from the NRZ signal for the first time. The clock component is enhanced in an SOA and the pseudo-return-to-zero (PRZ) signal is filtered. The PRZ signal is input into an injection mode-locked fiber ring laser for clock recovery. The recovered clock and the NRZ signal are input into TOAD as pump signal and probe signal, respectively, and format conversion is performed. The quality of the converted RZ signal is determined by that of the recovered clock and the NRZ signal, whereas hardly influenced by gain recovery time of the SOA. In the experimental demonstration, the obtained RZ signal has an extinction ratio of 8.7dB and low pattern dependency. After conversion, the spectrum broadens obviously and shows multimode structure with spectrum interval of 0.08nm, which matches with the bit rate 10Gbit/s. Furthermore, this format conversion method has some tolerance on the pattern dependency of the clock signal.

10 GHz Standing-Wave Coplanar Stripline on LiNbO3 Crystal for Radio to Optical-Wave Conversion

NASA Astrophysics Data System (ADS)

Darwis, F.; Wijayanto, Y. N.; Setiawan, A.; Mahmudin, D.; Rahman, A. N.; Daud, P.

2018-04-01

Recently, X-band radar systems are used widely for surveillance and navigation applications. Especially in archipelago or maritime country, the surveillance/navigation radar systems are required to monitoring critical areas and managing marine traffic. Accurate detection and fast analysis should be improved furthermore to provide security and safety condition. Therefore, several radar systems should be installed in many places to coverage the critical areas within radar networks. The radar network can be connected using optical fibers since it has extremely low propagation loss with optical-wave to carry-out the radar-wave. One important component in the scenario is a radio to optical-wave conversion component. In this paper, we report a 10 GHz radio to optical-wave conversion component using standing-wave coplanar stripline (CPS) on LiNbO3 optical crystal as the substrate. The standing-wave CPS electrodes with narrow slot are arranged in an array structure. An optical waveguide is located close to the narrow slot. The CPS electrodes were analysed using electromagnetic analysis software for 10 GHz operational frequency. Responses for slot width and electrode length variation are reported. As results, return loss of -14.580 dB and -19.517 dB are obtained for single and array CPS electrodes respectively. Optimization of the designed radio to optical-wave conversion devices was also done.

All-optical 40Gbit/s format conversion from NRZ to RZ based on SFG in a PPLN waveguide

NASA Astrophysics Data System (ADS)

Wang, Jian; Sun, Junqiang

2006-01-01

A novel all-optical 40Gbit/s NRZ-to-RZ data format conversion scheme based on sum-frequency generation (SFG) interaction in a periodically poled LiNbO 3 (PPLN) waveguide is presented for the first time, using a Mach-Zehnder interferometer (MZI). The conversion mechanism relies on the combination of attenuation and nonlinear phase shift Φ NL induced on the signal field. The performance of the conversion is numerically evaluated, with the result showing that it is more effective to yield Φ NL when appropriately phase mismatched for SFG process but Φ NL~0 when quasi-phase-matching (QPM). Compared with the cascaded second-order nonlinear interactions (SHG+DFG) with the influence of walk-off effect, a high conversion efficiency and good performance are achieved with peak power 500mw and width 2ps of the pump, which can be used in super high-speed situation (40Gbit/s and above). Finally, the inverse process of SFG and corresponding walk-off effect are analyzed and the optimum arrangement of power is proposed, showing that proper power, pump width, and waveguide length are necessary for achieving a satisfied conversion effect.

Optical and Electrical Performance of MOS-Structure Silicon Solar Cells with Antireflective Transparent ITO and Plasmonic Indium Nanoparticles under Applied Bias Voltage.

PubMed

Ho, Wen-Jeng; Sue, Ruei-Siang; Lin, Jian-Cheng; Syu, Hong-Jang; Lin, Ching-Fuh

2016-08-10

This paper reports impressive improvements in the optical and electrical performance of metal-oxide-semiconductor (MOS)-structure silicon solar cells through the incorporation of plasmonic indium nanoparticles (In-NPs) and an indium-tin-oxide (ITO) electrode with periodic holes (perforations) under applied bias voltage. Samples were prepared using a plain ITO electrode or perforated ITO electrode with and without In-NPs. The samples were characterized according to optical reflectance, dark current voltage, induced capacitance voltage, external quantum efficiency, and photovoltaic current voltage. Our results indicate that induced capacitance voltage and photovoltaic current voltage both depend on bias voltage, regardless of the type of ITO electrode. Under a bias voltage of 4.0 V, MOS cells with perforated ITO and plain ITO, respectively, presented conversion efficiencies of 17.53% and 15.80%. Under a bias voltage of 4.0 V, the inclusion of In-NPs increased the efficiency of cells with perforated ITO and plain ITO to 17.80% and 16.87%, respectively.

Optical and Electrical Performance of MOS-Structure Silicon Solar Cells with Antireflective Transparent ITO and Plasmonic Indium Nanoparticles under Applied Bias Voltage

PubMed Central

Ho, Wen-Jeng; Sue, Ruei-Siang; Lin, Jian-Cheng; Syu, Hong-Jang; Lin, Ching-Fuh

2016-01-01

This paper reports impressive improvements in the optical and electrical performance of metal-oxide-semiconductor (MOS)-structure silicon solar cells through the incorporation of plasmonic indium nanoparticles (In-NPs) and an indium-tin-oxide (ITO) electrode with periodic holes (perforations) under applied bias voltage. Samples were prepared using a plain ITO electrode or perforated ITO electrode with and without In-NPs. The samples were characterized according to optical reflectance, dark current voltage, induced capacitance voltage, external quantum efficiency, and photovoltaic current voltage. Our results indicate that induced capacitance voltage and photovoltaic current voltage both depend on bias voltage, regardless of the type of ITO electrode. Under a bias voltage of 4.0 V, MOS cells with perforated ITO and plain ITO, respectively, presented conversion efficiencies of 17.53% and 15.80%. Under a bias voltage of 4.0 V, the inclusion of In-NPs increased the efficiency of cells with perforated ITO and plain ITO to 17.80% and 16.87%, respectively. PMID:28773801

Proposal of optical mode switch

NASA Astrophysics Data System (ADS)

Takakura, Ryuta; Jizodo, Makoto; Fujino, Asuka; Tanaka, Tatsushi; Hamamoto, Kiichi

2014-08-01

Here, we propose a novel optical mode switch, which is a new concept of the optical switch. It can overcome the matrix size limitation issue, which has been a general issue for the waveguide optical space switch, because of its simple fiber coupling configuration. In addition, it contributes to the lossless mux/demux function such as wavelength multiplexing with powerless mode conversion unlike wavelength conversion. In this paper, we propose the principle of the optical mode switch. The simulation results showed less than -30 dB mode crosstalk, with less than only 0.1 dB excess loss for a two-mode optical switch. Moreover, the scalable configuration up to four modes is also proposed in this paper.

A Methoxydiphenylamine-Substituted Carbazole Twin Derivative: An Efficient Hole-Transporting Material for Perovskite Solar Cells.

PubMed

Gratia, Paul; Magomedov, Artiom; Malinauskas, Tadas; Daskeviciene, Maryte; Abate, Antonio; Ahmad, Shahzada; Grätzel, Michael; Getautis, Vytautas; Nazeeruddin, Mohammad Khaja

2015-09-21

The small-molecule-based hole-transporting material methoxydiphenylamine-substituted carbazole was synthesized and incorporated into a CH3NH3PbI3 perovskite solar cell, which displayed a power conversion efficiency of 16.91%, the second highest conversion efficiency after that of Spiro-OMeTAD. The investigated hole-transporting material was synthesized in two steps from commercially available and relatively inexpensive starting reagents. Various electro-optical measurements (UV/Vis, IV, thin-film conductivity, hole mobility, DSC, TGA, ionization potential) have been carried out to characterize the new hole-transporting material. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Light manipulation for organic optoelectronics using bio-inspired moth's eye nanostructures.

PubMed

Zhou, Lei; Ou, Qing-Dong; Chen, Jing-De; Shen, Su; Tang, Jian-Xin; Li, Yan-Qing; Lee, Shuit-Tong

2014-02-10

Organic-based optoelectronic devices, including light-emitting diodes (OLEDs) and solar cells (OSCs) hold great promise as low-cost and large-area electro-optical devices and renewable energy sources. However, further improvement in efficiency remains a daunting challenge due to limited light extraction or absorption in conventional device architectures. Here we report a universal method of optical manipulation of light by integrating a dual-side bio-inspired moth's eye nanostructure with broadband anti-reflective and quasi-omnidirectional properties. Light out-coupling efficiency of OLEDs with stacked triple emission units is over 2 times that of a conventional device, resulting in drastic increase in external quantum efficiency and current efficiency to 119.7% and 366 cd A(-1) without introducing spectral distortion and directionality. Similarly, the light in-coupling efficiency of OSCs is increased 20%, yielding an enhanced power conversion efficiency of 9.33%. We anticipate this method would offer a convenient and scalable way for inexpensive and high-efficiency organic optoelectronic designs.

Slow-Photon-Effect-Induced Photoelectrical-Conversion Efficiency Enhancement for Carbon-Quantum-Dot-Sensitized Inorganic CsPbBr3 Inverse Opal Perovskite Solar Cells.

PubMed

Zhou, Shujie; Tang, Rui; Yin, Longwei

2017-11-01

All-inorganic cesium lead halide perovskite is suggested as a promising candidate for perovskite solar cells due to its prominent thermal stability and comparable light absorption ability. Designing textured perovskite films rather than using planar-architectural perovskites can indeed optimize the optical and photoelectrical conversion performance of perovskite photovoltaics. Herein, for the first time, this study demonstrates a rational strategy for fabricating carbon quantum dot (CQD-) sensitized all-inorganic CsPbBr 3 perovskite inverse opal (IO) films via a template-assisted, spin-coating method. CsPbBr 3 IO introduces slow-photon effect from tunable photonic band gaps, displaying novel optical response property visible to naked eyes, while CQD inlaid among the IO frameworks not only broadens the light absorption range but also improves the charge transfer process. Applied in the perovskite solar cells, compared with planar CsPbBr 3 , slow-photon effect of CsPbBr 3 IO greatly enhances the light utilization, while CQD effectively facilitates the electron-hole extraction and injection process, prolongs the carrier lifetime, jointly contributing to a double-boosted power conversion efficiency (PCE) of 8.29% and an increased incident photon-to-electron conversion efficiency of up to 76.9%. The present strategy on CsPbBr 3 IO to enhance perovskite PCE can be extended to rationally design other novel optoelectronic devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Efficiency of magnetorheological fluid finishing on the elimination of defects in fused silica optics

NASA Astrophysics Data System (ADS)

Catrin, R.; Taroux, D.; Cormont, P.; Maunier, C.; Corbineau, T.; Razé, G.; Néauport, J.

2013-09-01

The MegaJoule laser being constructed at the CEA near Bordeaux (France) is designed to focus more than 1 MJ of energy of UV light, on a millimeter scale target in the centre of an experiment chamber. After amplification and transport at the wavelength of 1053 nm, frequency conversion at 351 nm is done with KH2PO4 crystals. The final optic assembly of this system is made up of large fused silica optics, working in transmission, that are used to convey, focus or shape the laser beam. When exposed to fluences of some joules per square centimeter at 351 nm within nanosecond pulse duration, fused silica optics can exhibit localized damage. Damage sites grow exponentially after further laser exposition and therefore dramatically limit the optic lifetime. The nature of the surface finishing process has been established to determine the lifetime of these components under high UV fluences (i.e. more than 5 J/cm2 for 3 ns pulses). Being able to reduce or eliminate the damage initiators such as subsurface cracks present in subsurface damage (SSD) layer of conventionally polished optical components aims this study. Magneto-rheological fluid finishing (MRF) is chosen as a final polishing tool to remove layers of material without inducing further damages. MRF enables to process optics with very small normal stresses applied to the surface during material removal and thus permits the elimination of the residual subsurface cracks. This study offers a better understanding of the efficiency of MRF polishing on the elimination of subsurface cracks in SSD layers.

A CW green laser emission by self-sum-frequency-mixing in Nd:GdCOB crystal

NASA Astrophysics Data System (ADS)

Shao, Y.; Jin, H. J.; Lin, J.; Zhang, D.; Tao, Z. H.; Zhang, T. Y.; Li, Y. L.; Ruan, Q. R.

2011-10-01

A compact and efficient green laser light at 538 nm produced by self-sum-frequency-mixing of both fundamental infrared laser waves (1061 and 1091 nm) in Nd:GdCa4O(BO3)3 (Nd:GdCOB) crystal is demonstrated. With 18.2 W of diode pump power, a maximum output power of 1.73 W in the green spectral range at 538 nm has been achieved, corresponding to an optical-to-optical conversion efficiency of 9.5%; the output power stability over 30 min is better than 3%. To the best of our knowledge, this is first work on self-sum-frequency-mixing of a diode pumped Nd:GdCOB laser.

Continuous-wave ultraviolet generation at 320 nm by intracavity frequency doubling of red-emitting Praseodymium lasers

NASA Astrophysics Data System (ADS)

Richter, A.; Pavel, N.; Heumann, E.; Huber, G.; Parisi, D.; Toncelli, A.; Tonelli, M.; Diening, A.; Seelert, W.

2006-04-01

We describe a new approach for the generation of coherent ultraviolet radiation. Continuous-wave ultraviolet light at 320 nm has been obtained by intracavity frequency doubling of red-emitting Praseodymium lasers. Lasing at the 640-nm fundamental wavelength in Pr:LiYF4 and Pr:BaY2F8 was realized by employing an optically pumped semiconductor laser at 480 nm as pump source.Using LiB3O5 as nonlinear medium, ~19 mW of ultraviolet radiation with ~9% optical efficiency with respect to absorbed power was reached for both laser crystals; the visible-to-ultraviolet conversion efficiency was 26% and 35% for Pr:LiYF4 and Pr:BaY2F8, respectively.

A continuous-wave and passively Q-switched Nd:LaGGG laser at 937 nm

NASA Astrophysics Data System (ADS)

Li, Z.-Y.; Ying, H.-Y.; Yang, H.; He, J.-L.

2013-10-01

A diode-end-pumped continuous-wave (CW) and passively Q-switched Nd:LaGGG (GGG: gadolinium gallium garnet) laser at about 937 nm was demonstrated for the first time. The maximum CW output power of 540 mW was obtained with the optical-optical conversion efficiency of 3.2% and the slope efficiency of 4.4%. A V3+:YAG (yttrium aluminum garnet) saturable absorber with the initial transmission of 97% was used for the passive Q-switching regime. The shortest pulse width was achieved as 500 ns with the pulse repetition rate of 96 kHz. The corresponding single-pulse energy and pulse peak power were determined as 1.56 μJ and 3.12 W, respectively.

Nonlinear Fano-Resonant Dielectric Metasurfaces

DOE PAGES

Yang, Yuanmu; Wang, Wenyi; Boulesbaa, Abdelaziz; ...

2015-10-26

Strong nonlinear light matter interaction is highly sought-after for a variety of applications including lasing and all-optical light modulation. Recently, resonant plasmonic structures have been considered promising candidates for enhancing nonlinear optical processes due to their ability to greatly enhance the optical near-field; however, their small mode volumes prevent the inherently large nonlinear susceptibility of the metal from being efficiently exploited. We present an alternative approach that utilizes a Fano-resonant silicon metasurface. The metasurface results in strong near-field enhancement within the volume of the silicon resonator while minimizing two photon absorption. Here, we measure a third harmonic generation enhancement factormore » of 1.5 105 with respect to an unpatterned silicon film and an absolute conversion efficiency of 1.2 10 6 with a peak pump intensity of 3.2 GW cm 2. The enhanced nonlinearity, combined with a sharp linear transmittance spectrum, results in transmission modulation with a modulation depth of 36%. Finally, the modulation mechanism is studied by pump probe experiments« less

Design of a sector bowtie nano-rectenna for optical power and infrared detection

NASA Astrophysics Data System (ADS)

Wang, Kai; Hu, Haifeng; Lu, Shan; Guo, Lingju; He, Tao

2015-10-01

We designed a sector bowtie nanoantenna integrated with a rectifier (Au-TiO x -Ti diode) for collecting infrared energy. The optical performance of the metallic bowtie nanoantenna was numerically investigated at infrared frequencies (5-30 μm) using three-dimensional frequency-domain electromagnetic field calculation software based on the finite element method. The simulation results indicate that the resonance wavelength and local field enhancement are greatly affected by the shape and size of the bowtie nanoantenna, as well as the relative permittivity and conductivity of the dielectric layer. The output current of the rectified nano-rectenna is substantially at nanoampere magnitude with an electric field intensity of 1 V/m. Moreover, the power conversion efficiency for devices with three different substrates illustrates that a substrate with a larger refractive index yields a higher efficiency and longer infrared response wavelength. Consequently, the optimized structure can provide theoretical support for the design of novel optical rectennas and fabrication of optoelectronic devices.

Al-/Ga-Doped ZnO Window Layers for Highly Efficient Cu₂ZnSn(S,Se)₄ Thin Film Solar Cells.

PubMed

Seo, Se Won; Seo, Jung Woo; Kim, Donghwan; Cheon, Ki-Beom; Lee, Doh-Kwon; Kim, Jin Young

2018-09-01

The successful use of Al-/Ga-doped ZnO (AGZO) thin films as a transparent conducting oxide (TCO) layer of a Cu2ZnSn(S,Se)4 (CZTSSe) thin film solar cell is demonstrated. The AGZO thin films were prepared by radio frequency (RF) sputtering. The structural, crystallographic, electrical, and optical properties of the AGZO thin films were systematically investigated. The photovoltaic properties of CZTSSe thin film solar cells incorporating the AGZO-based TCO layer were also reported. It has been found that the RF power and substrate temperature of the AGZO thin film are important factors determining the electrical, optical, and structural properties. The optimization process involving the RF power and the substrate temperature leads to good electrical and optical transmittance of the AGZO thin films. Finally, the CZTSSe solar cell with the AGZO TCO layer demonstrated a high conversion efficiency of 9.68%, which is higher than that of the conventional AZO counterpart by 12%.

Ultralow power continuous-wave frequency conversion in hydrogenated amorphous silicon waveguides.

PubMed

Wang, Ke-Yao; Foster, Amy C

2012-04-15

We demonstrate wavelength conversion through nonlinear parametric processes in hydrogenated amorphous silicon (a-Si:H) with maximum conversion efficiency of -13 dB at telecommunication data rates (10 GHz) using only 15 mW of pump peak power. Conversion bandwidths as large as 150 nm (20 THz) are measured in continuous-wave regime at telecommunication wavelengths. The nonlinear refractive index of the material is determined by four-wave mixing (FWM) to be n(2)=7.43×10(-13) cm(2)/W, approximately an order of magnitude larger than that of single crystal silicon. © 2012 Optical Society of America

Piezoelectric Nanoparticle-Polymer Composite Materials

NASA Astrophysics Data System (ADS)

McCall, William Ray

Herein we demonstrate that efficient piezoelectric nanoparticle-polymer composite materials can be synthesized and fabricated into complex microstructures using sugar-templating methods or optical printing techniques. Stretchable foams with excellent tunable piezoelectric properties are created by incorporating sugar grains directly into polydimethylsiloxane (PDMS) mixtures containing barium titanate (BaTiO3 -- BTO) nanoparticles and carbon nanotubes (CNTs), followed by removal of the sugar after polymer curing. Porosities and elasticity are tuned by simply adjusting the sugar/polymer mass ratio and the electrical performance of the foams showed a direct relationship between porosity and the piezoelectric outputs. User defined 2D and 3D optically printed piezoelectric microstructures are also fabricated by incorporating BTO nanoparticles into photoliable polymer solutions such as polyethylene glycol diacrylate (PEGDA) and exposing to digital optical masks that can be dynamically altered. Mechanical-to-electrical conversion efficiency of the optically printed composite is enhanced by chemically altering the surface of the BTO nanoparticles with acrylate groups which form direct covalent linkages with the polymer matrix under light exposure. Both of these novel materials should find exciting uses in a variety of applications including energy scavenging platforms, nano- and microelectromechanical systems (NEMS/MEMS), sensors, and acoustic actuators.

Non-linear optical properties of arylfuranylpropenones

NASA Astrophysics Data System (ADS)

Holla, B. Shivarama; Veerendra, B.; Indira, J.

2003-05-01

A series of arylfuranylpropenones 3a-i were synthesized by the reaction of 5-(2-nitro-4-methoxyphenyl)-2-furfural 1 with various acetophenones 2 by Claisen-Schmidt condensation. All the newly synthesized chalcones were characterized by elemental analysis and spectral studies. Most of them showed SHG conversion efficiency in powder form.

Down-conversion IM-DD RF photonic link utilizing MQW MZ modulator.

PubMed

Xu, Longtao; Jin, Shilei; Li, Yifei

2016-04-18

We present the first down-conversion intensity modulated-direct detection (IM-DD) RF photonic link that achieves frequency down-conversion using the nonlinear optical phase modulation inside a Mach-Zehnder (MZ) modulator. The nonlinear phase modulation is very sensitive and it can enable high RF-to-IF conversion efficiency. Furthermore, the link linearity is enhanced by canceling the nonlinear distortions from the nonlinear phase modulation and the MZ interferometer. Proof-of-concept measurement was performed. The down-conversion IM-DD link demonstrated 28dB improvement in distortion levels over that of a conventional IM-DD link using a LiNbO₃ MZ modulator.

Towards a versatile active wavelength converter for all-optical networks based on quasi-phase matched intra-cavity difference-frequency generation.

PubMed

Torregrosa, Adrián J; Maestre, Haroldo; Capmany, Juan

2013-11-18

The availability of reconfigurable all-optical wavelength converters for an efficient and flexible use of optical resources in WDM (wavelength division multiplexing) networks is still lacking at present. We propose and report preliminary results on a versatile active technique for multiple and tunable wavelength conversions in the 1500-1700 nm spectral region. The technique is based on combining broadband quasi-phase matched intra-cavity parametric single-pass difference-frequency generation close to degeneracy in a diode-pumped tunable laser. A periodically poled stoichiometric lithium tantalate crystal is used as the nonlinear medium, with a parametric pump wave generated in a continuous-wave self-injection locked Cr3+:LiCAF tunable laser operating at around 800 nm.

Continuous-wave, single-frequency 229  nm laser source for laser cooling of cadmium atoms.

PubMed

Kaneda, Yushi; Yarborough, J M; Merzlyak, Yevgeny; Yamaguchi, Atsushi; Hayashida, Keitaro; Ohmae, Noriaki; Katori, Hidetoshi

2016-02-15

Continuous-wave output at 229 nm for the application of laser cooling of Cd atoms was generated by the fourth harmonic using two successive second-harmonic generation stages. Employing a single-frequency optically pumped semiconductor laser as a fundamental source, 0.56 W of output at 229 nm was observed with a 10-mm long, Brewster-cut BBO crystal in an external cavity with 1.62 W of 458 nm input. Conversion efficiency from 458 nm to 229 nm was more than 34%. By applying a tapered amplifier (TA) as a fundamental source, we demonstrated magneto-optical trapping of all stable Cd isotopes including isotopes Cd111 and Cd113, which are applicable to optical lattice clocks.

Call for Papers: Photonics in Switching

NASA Astrophysics Data System (ADS)

Wosinska, Lena; Glick, Madeleine

2006-04-01

Call for Papers: Photonics in Switching

Guest Editors:

Lena Wosinska, Royal Institute of Technology (KTH) / ICT Sweden Madeleine Glick, Intel Research, Cambridge, UK

Scope of Submission

• WDM node architectures
• Novel device technologies enabling photonics in switching, such as optical switch fabrics, optical memory, and wavelength conversion
• Routing protocols
• WDM switching and routing
• Quality of service
• Performance measurement and evaluation
• Next-generation optical networks: architecture, signaling, and control
• Traffic measurement and field trials
• Optical burst and packet switching
• OBS/OPS node architectures
• Burst/Packet scheduling and routing algorithms
• Contention resolution/avoidance strategies
• Services and applications for OBS/OPS (e.g., grid networks, storage-area networks, etc.)
• Burst assembly and ingress traffic shaping
• Hybrid OBS/TDM or OBS/wavelength routing

Manuscript Submission

13.2% efficiency Si nanowire/PEDOT:PSS hybrid solar cell using a transfer-imprinted Au mesh electrode

PubMed Central

Park, Kwang-Tae; Kim, Han-Jung; Park, Min-Joon; Jeong, Jun-Ho; Lee, Jihye; Choi, Dae-Geun; Lee, Jung-Ho; Choi, Jun-Hyuk

2015-01-01

In recent years, inorganic/organic hybrid solar cell concept has received growing attention for alternative energy solution because of the potential for facile and low-cost fabrication and high efficiency. Here, we report highly efficient hybrid solar cells based on silicon nanowires (SiNWs) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) using transfer-imprinted metal mesh front electrodes. Such a structure increases the optical absorption and shortens the carrier transport distance, thus, it greatly increases the charge carrier collection efficiency. Compared with hybrid cells formed using indium tin oxide (ITO) electrodes, we find an increase in power conversion efficiency from 5.95% to 13.2%, which is attributed to improvements in both the electrical and optical properties of the Au mesh electrode. Our fabrication strategy for metal mesh electrode is suitable for the large-scale fabrication of flexible transparent electrodes, paving the way towards low-cost, high-efficiency, flexible solar cells. PMID:26174964

Effect of intrinsic surface roughness on the efficiency of intermodal phase matching in silica optical nanofibers.

PubMed

Khudus, Muhammad I M Abdul; Lee, Timothy; Horak, Peter; Brambilla, Gilberto

2015-04-01

We investigate the effect of intrinsic surface roughness associated to frozen thermal oscillations from the fiber fabrication process on the efficiency of third-harmonic generation via intermodal phase matching in silica nanofibers. Already a periodic wave with roughness of 0.2 nm reduces the efficiency by roughly 50% in a 1-mm optical nanofiber, with the divergence growing quadratically with distance. The surface wave period does not exhibit a large impact on the efficiency, due to averaging effects. However, both the location of the surface waves with respect to the phase matching radius as well as the surface wave amplitude have substantial effect on the efficiency, with the former presenting the possibility of transferring the power back to the pump wavelength. Simulations with a realistic superposition of random surface waves indicate that the conversion efficiency increases only for a few mm of propagation and reaches a maximum of less than 1%.

Power scaling of supercontinuum seeded megahertz-repetition rate optical parametric chirped pulse amplifiers.

PubMed

Riedel, R; Stephanides, A; Prandolini, M J; Gronloh, B; Jungbluth, B; Mans, T; Tavella, F

2014-03-15

Optical parametric chirped-pulse amplifiers with high average power are possible with novel high-power Yb:YAG amplifiers with kW-level output powers. We demonstrate a compact wavelength-tunable sub-30-fs amplifier with 11.4 W average power with 20.7% pump-to-signal conversion efficiency. For parametric amplification, a beta-barium borate crystal is pumped by a 140 W, 1 ps Yb:YAG InnoSlab amplifier at 3.25 MHz repetition rate. The broadband seed is generated via supercontinuum generation in a YAG crystal.

Laser beam combining and cleanup by stimulated Brillouin scattering in a multimode optical fiber.

PubMed

Rodgers, B C; Russell, T H; Roh, W B

1999-08-15

A new technique for combining low-power laser beams has been demonstrated by use of semiconductor diode lasers. The technique, which is appropriate for any single-longitudinal-mode laser, is based on stimulated Brillouin scattering (SBS) in long multimode optical fibers. It produces a clean Gaussian-like beam that corresponds to the fundamental fiber mode, irrespective of the profile of the pump. Coherent as well as incoherent combining was demonstrated, and conversion slope efficiencies as high as 67% and 83% were shown to be achievable for the single-pass and ring-cavity SBS geometries, respectively.

Generation conditions of CW Diode Laser Sustained Plasma

NASA Astrophysics Data System (ADS)

Nishimoto, Koji; Matsui, Makoto; Ono, Takahiro

2016-09-01

Laser sustained plasma was generated using 1 kW class continuous wave diode laser. The laser beam was focused on the seed plasma generated by arc discharge in 1 MPa xenon lamp. The diode laser has advantages of high energy conversion efficiency of 80%, ease of maintenance, compact size and availability of conventional quartz based optics. Therefore, it has a prospect of further development compared with conventional CO2 laser. In this study, variation of the plasma shape caused by laser power is observed and also temperature distribution in the direction of plasma radius is measured by optical emission spectroscopy.

Distinct enhancement of sub-bandgap photoresponse through intermediate band in high dose implanted ZnTe:O alloys

NASA Astrophysics Data System (ADS)

Li, Jing; Ye, Jiandong; Ren, Fangfang; Tang, Dongming; Yang, Yi; Tang, Kun; Gu, Shulin; Zhang, Rong; Zheng, Youdou

2017-03-01

The demand for high efficiency intermediate band (IB) solar cells is driving efforts in producing high quality IB photovoltaic materials. Here, we demonstrate ZnTe:O highly mismatched alloys synthesized by high dose ion implantation and pulsed laser melting exhibiting optically active IB states and efficient sub-gap photoresponse, as well as investigate the effect of pulsed laser melting on the structural and optical recovery in detail. The structural evolution and vibrational dynamics indicates a significant structural recovery of ZnTe:O alloys by liquid phase epitaxy during pulsed laser melting process, but laser irradiation also aggravates the segregation of Te in ZnTe:O alloys. A distinct intermediate band located at 1.8 eV above valence band is optically activated as evidenced by photoluminescence, absorption and photoresponse characteristics. The carrier dynamics indicates that carriers in the IB electronic states have a relatively long lifetime, which is beneficial for the fast separation of carriers excited by photons with sub-gap energy and thus the improved overall conversion efficiency. The reproducible capability of implantation and laser annealing at selective area enable the realization of high efficient lateral junction solar cells, which can ensure extreme light trapping and efficient charge separation.

Developments in photonic and mm-wave component technology for fiber radio

NASA Astrophysics Data System (ADS)

Iezekiel, Stavros

2013-01-01

A review of photonic component technology for fiber radio applications at 60 GHz will be given. We will focus on two architectures: (i) baseband-over-fiber and (ii) RF-over-fiber. In the first approach, up-conversion to 60 GHz is performed at the picocell base stations, with data being transported over fiber, while in the second both the data and rum­ wave carrier are transported over fiber. For the baseband-over-fiber scheme, we examine techniques to improve the modulation efficiency of directly­ modulated fiber links. These are based on traveling-wave structures applied to series cascades of lasers. This approach combines the improvement in differential quantum efficiency with the ability to tailor impedance matching as required. In addition, we report on various base station transceiver architectures based on optically-controlled :tvfMIC self­ oscillating mixers, and their application to 60 GHz fiber radio. This approach allows low cost optoelectronic transceivers to be used for the baseband fiber link, whilst minimizing the impact of dispersion. For the RF-over-fiber scheme, we report on schemes for optical generation of 100 GHz. These use modulation of a Mach-Zehnder modulator at Vπ bias in cascade with a Mach-Zehnder driven by 1.25 Gb/s data. One of the issues in RF-over-fiber is dispersion, while reduced modulation efficiency due to the presence of the optical carrier is also problematic. We examine the use of silicon nitride micro-ring resonators for the production of optical single sideband modulation in order to combat dispersion, and for the reduction of optical carrier power in order to improve link modulation efficiency.

A continuous-wave, widely tunable, intra-cavity, singly resonant, magnesium-doped, periodically poled lithium niobate optical parametric oscillator

NASA Astrophysics Data System (ADS)

Li, Z. P.; Duan, Y. M.; Wu, K. R.; Zhang, G.; Zhu, H. Y.; Wang, X. L.; Chen, Y. H.; Xue, Z. Q.; Lin, Q.; Song, G. C.; Su, H.

2013-05-01

We report a continuous-wave (CW), intra-cavity singly resonant optical parametric oscillator (OPO), based on periodically poled MgO:LiNbO3 pumped by a diode-end-pumped CW Nd:YVO4 laser, and calculate the gain of optical parametric amplification as a function of pump beam waist (at 1064 nm) in the singly resonant OPO (SRO) cavity, to balance the mode-matching and the intensity for the higher gain of a signal wave in the operation of the SRO. In order to achieve maximum gain, we use a convex lens to limit the 1064 nm beam waist. In the experiment, a tunable signal output from 1492 to 1614 nm and an idler output from 3122 to 3709 nm are obtained. For an 808 nm pump power of 11.5 W, a maximum signal output power of up to 2.48 W at 1586 nm and an idler output power of 1.1 W at 3232 nm are achieved with a total optical-to-optical conversion efficiency of 31%.

All-optical switching of silicon disk resonator based on photothermal effect in metal-insulator-metal absorber.

PubMed

Shi, Yuechun; Chen, Xi; Lou, Fei; Chen, Yiting; Yan, Min; Wosinski, Lech; Qiu, Min

2014-08-01

Efficient narrowband light absorption by a metal-insulator-metal (MIM) structure can lead to high-speed light-to-heat conversion at a micro- or nanoscale. Such a MIM structure can serve as a heater for achieving all-optical light control based on the thermo-optical (TO) effect. Here we experimentally fabricated and characterized a novel all-optical switch based on a silicon microdisk integrated with a MIM light absorber. Direct integration of the absorber on top of the microdisk reduces the thermal capacity of the whole device, leading to high-speed TO switching of the microdisk resonance. The measurement result exhibits a rise time of 2.0 μs and a fall time of 2.6 μs with switching power as low as 0.5 mW; the product of switching power and response time is only about 1.3  mW·μs. Since no auxiliary elements are required for the heater, the switch is structurally compact, and its fabrication is rather easy. The device potentially can be deployed for new kinds of all-optical applications.

Multi-optical-axis measurement of freeform progressive addition lenses using a Hartmann-Shack wavefront sensor

NASA Astrophysics Data System (ADS)

Xiang, Huazhong; Guo, Hang; Fu, Dongxiang; Zheng, Gang; Zhuang, Songlin; Chen, JiaBi; Wang, Cheng; Wu, Jie

2018-05-01

To precisely measure the whole-surface characterization of freeform progressive addition lenses (PALs), considering the multi-optical-axis conditions is becoming particularly important. Spherical power and astigmatism (cylinder) measurements for freeform PALs, using a Hartmann-Shack wavefront sensor (HSWFS) are proposed herein. Conversion formulas for the optical performance results were provided as HSWFS Zernike polynomial expansions. For each selected zone, the studied PALs were placed and tilted to simulate the multi-optical-axis conditions. The results of two tested PALs were analyzed using MATLAB programs and represented as contour plots of the spherical equivalent and cylinder of the whole-surface. The proposed experimental setup can provide a high accuracy as well as a possibility of choosing 12 lines and positions of 193 measurement zones on the entire surface. This approach to PAL analysis is potentially an efficient and useful method to objectively evaluate the optical performances, in which the full lens surface is defined and expressed as the contour plots of power in different regions (i.e., the distance region, progressive region, and near region) of the lens for regions of interest.

Superluminescence from an optically pumped molecular tunneling junction by injection of plasmon induced hot electrons

PubMed Central

Braun, Kai; Wang, Xiao; Kern, Andreas M; Adler, Hilmar; Peisert, Heiko; Chassé, Thomas; Zhang, Dai

2015-01-01

Summary Here, we demonstrate a bias-driven superluminescent point light-source based on an optically pumped molecular junction (gold substrate/self-assembled molecular monolayer/gold tip) of a scanning tunneling microscope, operating at ambient conditions and providing almost three orders of magnitude higher electron-to-photon conversion efficiency than electroluminescence induced by inelastic tunneling without optical pumping. A positive, steadily increasing bias voltage induces a step-like rise of the Stokes shifted optical signal emitted from the junction. This emission is strongly attenuated by reversing the applied bias voltage. At high bias voltage, the emission intensity depends non-linearly on the optical pump power. The enhanced emission can be modelled by rate equations taking into account hole injection from the tip (anode) into the highest occupied orbital of the closest substrate-bound molecule (lower level) and radiative recombination with an electron from above the Fermi level (upper level), hence feeding photons back by stimulated emission resonant with the gap mode. The system reflects many essential features of a superluminescent light emitting diode. PMID:26171286

Limitations to THz generation by optical rectification using tilted pulse fronts.

PubMed

Ravi, Koustuban; Huang, W Ronny; Carbajo, Sergio; Wu, Xiaojun; Kärtner, Franz

2014-08-25

Terahertz (THz) generation by optical rectification (OR) using tilted-pulse-fronts is studied. A one-dimensional (1-D) model which simultaneously accounts for (i) the nonlinear coupled interaction of the THz and optical radiation, (ii) angular and material dispersion, (iii) absorption, iv) self-phase modulation and (v) stimulated Raman scattering is presented. We numerically show that the large experimentally observed cascaded frequency down-shift and spectral broadening (cascading effects) of the optical pump pulse is a direct consequence of THz generation. In the presence of this large spectral broadening, the large angular dispersion associated with tilted-pulse-fronts which is ~15-times larger than material dispersion, accentuates phase mismatch and degrades THz generation. Consequently, this cascading effect in conjunction with angular dispersion is shown to be the strongest limitation to THz generation in lithium niobate for pumping at 1 µm. It is seen that the exclusion of these cascading effects in modeling OR, leads to a significant overestimation of the optical-to-THz conversion efficiency. The results are verified with calculations based on a 2-D spatial model. The simulation results are supported by experiments.

Periodic density modulation for quasi-phase-matching of optical frequency conversion is inefficient under shallow focusing and constant ambient pressure.

PubMed

Hadas, Itai; Bahabad, Alon

2016-09-01

The two main mechanisms of a periodic density modulation relevant to nonlinear optical conversion in a gas medium are spatial modulations of the index of refraction and of the number of emitters. For a one-dimensional model neglecting focusing and using a constant ambient pressure, it is shown theoretically and demonstrated numerically that the effects of these two mechanisms during frequency conversion cancel each other exactly. Under the considered conditions, this makes density modulation inefficient for quasi-phase-matching an optical frequency conversion process. This result is particularly relevant for high-order harmonic generation.

Improved conversion efficiency of dye sensitized solar cell using Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomar, Laxmi J., E-mail: laxmi-tomar86@yahoo.com; Bhatt, Piyush J.; Desai, Rahul K.

TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were prepared by hydrothermal method for dye sensitized solar cell (DSSC) application. The structural and optical properties were investigated by X –ray diffraction (XRD) and UV-Visible spectroscopy respectively. XRD results revealed the formation of material in nano size. The average crystallite size is 22.32 nm, 17.41 nm and 6.31 nm for TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites respectively. The optical bandgap varies from 2.04 eV to 3.75 eV. Dye sensitized solar cells were fabricated using the prepared material. Pomegranate juice was used as a sensitizer and graphitemore » coated conducting glass plate was used as counter electrode. The I – V characteristics were recorded to measure photo response of DSSC. Photovoltaic parameter like open circuit voltage, power conversion efficiency, and fill factor were evaluated for fabricated solar cell. The power conversion efficiency of DSSC fabricated with TiO{sub 2}, TiO{sub 2}-ZrO{sub 2} and Zn doped TiO{sub 2}-ZrO{sub 2} nanocomposites were found 0.71%, 1.97% and 4.58% respectively.« less

Growth and characterization of a new nonlinear optical organic crystal: 2,4,6-Trimethylacetanilide

NASA Astrophysics Data System (ADS)

Upadhyaya, V.; Prabhu, Sharada G.

2015-09-01

A new nonlinear optical organic material, 2,4,6-trimethylacetanilide (246TMAA), also known as N-[2,4,6- trimethylphenyl]acetamide, has been synthesized and grown as a single crystal by the slow evaporation technique by organic solvents. The grown crystals have been characterized by morphology study. The crystals are prismatic. Surface examination shows granular dendritic pattern in optical micrograph. The Scanning Electron Micrograph shows the layered growth of the crystal. The Differential Scanning Calorimeter plot shows no phase change until melting point (219°C). The density of the crystals is 1.1g/cc and the crystals are soft. The crystals are transparent in the visible region and in the ultra-violet region till 280 nm. 246TMAA crystallizes with 2 molecules in a monoclinic unit cell in the noncentrosymmetric point group m, space group Pn. Refractive indices of this optically biaxial crystal along the three crystallophysical axes have been measured at 633 nm. The optical second harmonic generation efficiency of the crystal at 1064 nm is about half that of the urea crystal, measured by powder method using Nd:YAG laser. The results show that the 246TMAA crystal can efficiently be used for up-conversion of infrared radiation into visible green light. The powder X-ray diffraction spectrum of the crystal has been obtained.

Efficient preparation of enantiopure D-phenylalanine through asymmetric resolution using immobilized phenylalanine ammonia-lyase from Rhodotorula glutinis JN-1 in a recirculating packed-bed reactor.

PubMed

Zhu, Longbao; Zhou, Li; Huang, Nan; Cui, Wenjing; Liu, Zhongmei; Xiao, Ke; Zhou, Zhemin

2014-01-01

An efficient enzymatic process was developed to produce optically pure D-phenylalanine through asymmetric resolution of the racemic DL-phenylalanine using immobilized phenylalanine ammonia-lyase (RgPAL) from Rhodotorula glutinis JN-1. RgPAL was immobilized on a modified mesoporous silica support (MCM-41-NH-GA). The resulting MCM-41-NH-GA-RgPAL showed high activity and stability. The resolution efficiency using MCM-41-NH-GA-RgPAL in a recirculating packed-bed reactor (RPBR) was higher than that in a stirred-tank reactor. Under optimal operational conditions, the volumetric conversion rate of L-phenylalanine and the productivity of D-phenylalanine reached 96.7 mM h⁻¹ and 0.32 g L⁻¹ h⁻¹, respectively. The optical purity (eeD) of D-phenylalanine exceeded 99%. The RPBR ran continuously for 16 batches, the conversion ratio did not decrease. The reactor was scaled up 25-fold, and the productivity of D-phenylalanine (eeD>99%) in the scaled-up reactor reached 7.2 g L⁻¹ h⁻¹. These results suggest that the resolution process is an alternative method to produce highly pure D-phenylalanine.

Efficient Preparation of Enantiopure D-Phenylalanine through Asymmetric Resolution Using Immobilized Phenylalanine Ammonia-Lyase from Rhodotorula glutinis JN-1 in a Recirculating Packed-Bed Reactor

PubMed Central

Huang, Nan; Cui, Wenjing; Liu, Zhongmei; Xiao, Ke; Zhou, Zhemin

2014-01-01

An efficient enzymatic process was developed to produce optically pure D-phenylalanine through asymmetric resolution of the racemic DL-phenylalanine using immobilized phenylalanine ammonia-lyase (RgPAL) from Rhodotorula glutinis JN-1. RgPAL was immobilized on a modified mesoporous silica support (MCM-41-NH-GA). The resulting MCM-41-NH-GA-RgPAL showed high activity and stability. The resolution efficiency using MCM-41-NH-GA-RgPAL in a recirculating packed-bed reactor (RPBR) was higher than that in a stirred-tank reactor. Under optimal operational conditions, the volumetric conversion rate of L-phenylalanine and the productivity of D-phenylalanine reached 96.7 mM h−1 and 0.32 g L−1 h−1, respectively. The optical purity (ee D) of D-phenylalanine exceeded 99%. The RPBR ran continuously for 16 batches, the conversion ratio did not decrease. The reactor was scaled up 25-fold, and the productivity of D-phenylalanine (ee D>99%) in the scaled-up reactor reached 7.2 g L−1 h−1. These results suggest that the resolution process is an alternative method to produce highly pure D-phenylalanine. PMID:25268937

Optical data packet synchronization and multiplexing using a tunable optical delay based on wavelength conversion and inter-channel chromatic dispersion.

PubMed

Fazal, Irfan; Yilmaz, Omer; Nuccio, Scott; Zhang, Bo; Willner, Alan E; Langrock, Carsten; Fejer, Martin M

2007-08-20

10 Gb/s non-return-to-zero (NRZ) on-off keyed (OOK) optical data packets are synchronized and time-multiplexed using a 26-ns tunable all-optical delay line. The delay element is based on wavelength conversion in periodically poled lithium niobate (PPLN) waveguides, inter-channel chromatic dispersion in dispersion compensating fiber (DCF) and intra-channel dispersion compensation with a chirped fiber Bragg grating (FBG). Delay reconfiguration time is measured to be less than 300 ps.

Elastic all-optical multi-hop interconnection in data centers with adaptive spectrum allocation

NASA Astrophysics Data System (ADS)

Hong, Yuanyuan; Hong, Xuezhi; Chen, Jiajia; He, Sailing

2017-01-01

In this paper, a novel flex-grid all-optical interconnect scheme that supports transparent multi-hop connections in data centers is proposed. An inter-rack all-optical multi-hop connection is realized with an optical loop employed at flex-grid wavelength selective switches (WSSs) in an intermediate rack rather than by relaying through optical-electric-optical (O-E-O) conversions. Compared with the conventional O-E-O based approach, the proposed all-optical scheme is able to off-load the traffic at intermediate racks, leading to a reduction of the power consumption and cost. The transmission performance of the proposed flex-grid multi-hop all-optical interconnect scheme with various modulation formats, including both coherently detected and directly detected approaches, are investigated by Monte-Carlo simulations. To enhance the spectrum efficiency (SE), number-of-hop adaptive bandwidth allocation is introduced. Numerical results show that the SE can be improved by up to 33.3% at 40 Gbps, and by up to 25% at 100 Gbps. The impact of parameters, such as targeted bit error rate (BER) level and insertion loss of components, on the transmission performance of the proposed approach are also explored. The results show that the maximum SE improvement of the adaptive approach over the non-adaptive one is enhanced with the decrease of the targeted BER levels and the component insertion loss.

Quadruple multi-wavelength conversion for access network scalability based on cross-phase modulation in an SOA-MZI

NASA Astrophysics Data System (ADS)

Ab-Rahman, Mohammad Syuhaimi; Swedan, Abdulhameed Almabrok

2017-12-01

The emergence of new services and data exchange applications has increased the demand for bandwidth among individuals and commercial business users at the access area. Thus, vendors of optical access networks should achieve a high-capacity system. This study demonstrates the performance of an integrated configuration of one to four multi-wavelength conversions at 10 Gb/s based on cross-phase modulation using semiconductor optical amplifier integrated with Mach-Zehnder interferometer. The Opti System simulation tool is used to simulate and demonstrate one to four wavelength conversions using one modulated wavelength and four probes of continuous wave sources. The wavelength converter processes are confirmed through investigation of the input and output characteristics, optical signal-to-noise ratio, conversion efficiency, and extinction ratio of new modulated channels after separation by demultiplexing. The outcomes of the proposed system using single channel indicate that the capacity can increase from 10 Gb/s to 50 Gb/s with a maximum number of access points increasing from 64 to 320 (each point with 156.25 Mb/s bandwidth). The splitting ratio of 1:16 provides each client with 625 Mb/s for the total number of 80 users. The Q-factor and bit error rate curves are investigated to confirm and validate the modified scheme and prove the system performance of the full topology of 25 km with 1/64 splitter. The outcomes are within the acceptable range to provide the system scalability.

Optical-to-optical interface device

NASA Technical Reports Server (NTRS)

Jacobson, A. D.; Bleha, W. P.; Miller, L.; Grinberg, J.; Fraas, L.; Margerum, D.

1975-01-01

An investigation was conducted to develop an optical-to-optical interface device capable of performing real-time incoherent-to-incoherent optical image conversion. The photoactivated liquid crystal light valve developed earlier represented a prototype liquid crystal light valve device capable of performing these functions. A device was developed which had high performance and extended lifetime.

Sinusoidal nanotextures for light management in silicon thin-film solar cells.

PubMed

Köppel, G; Rech, B; Becker, C

2016-04-28

Recent progresses in liquid phase crystallization enabled the fabrication of thin wafer quality crystalline silicon layers on low-cost glass substrates enabling conversion efficiencies up to 12.1%. Because of its indirect band gap, a thin silicon absorber layer demands for efficient measures for light management. However, the combination of high quality crystalline silicon and light trapping structures is still a critical issue. Here, we implement hexagonal 750 nm pitched sinusoidal and pillar shaped nanostructures at the sun-facing glass-silicon interface into 10 μm thin liquid phase crystallized silicon thin-film solar cell devices on glass. Both structures are experimentally studied regarding their optical and optoelectronic properties. Reflection losses are reduced over the entire wavelength range outperforming state of the art anti-reflective planar layer systems. In case of the smooth sinusoidal nanostructures these optical achievements are accompanied by an excellent electronic material quality of the silicon absorber layer enabling open circuit voltages above 600 mV and solar cell device performances comparable to the planar reference device. For wavelengths smaller than 400 nm and higher than 700 nm optical achievements are translated into an enhanced quantum efficiency of the solar cell devices. Therefore, sinusoidal nanotextures are a well-balanced compromise between optical enhancement and maintained high electronic silicon material quality which opens a promising route for future optimizations in solar cell designs for silicon thin-film solar cells on glass.

Multicast routing for wavelength-routed WDM networks with dynamic membership

NASA Astrophysics Data System (ADS)

Huang, Nen-Fu; Liu, Te-Lung; Wang, Yao-Tzung; Li, Bo

2000-09-01

Future broadband networks must support integrated services and offer flexible bandwidth usage. In our previous work, we explore the optical link control layer on the top of optical layer that enables the possibility of bandwidth on-demand service directly over wavelength division multiplexed (WDM) networks. Today, more and more applications and services such as video-conferencing software and Virtual LAN service require multicast support over the underlying networks. Currently, it is difficult to provide wavelength multicast over the optical switches without optical/electronic conversions although the conversion takes extra cost. In this paper, based on the proposed wavelength router architecture (equipped with ATM switches to offer O/E and E/O conversions when necessary), a dynamic multicast routing algorithm is proposed to furnish multicast services over WDM networks. The goal is to joint a new group member into the multicast tree so that the cost, including the link cost and the optical/electronic conversion cost, is kept as less as possible. The effectiveness of the proposed wavelength router architecture as well as the dynamic multicast algorithm is evaluated by simulation.

Direct electrical-to-optical conversion and light modulation in micro whispering-gallery-mode resonators

NASA Technical Reports Server (NTRS)

Maleki, Lute (Inventor); Levi, Anthony F. J. (Inventor)

2005-01-01

Techniques for directly converting an electrical signal into an optical signal by using a whispering gallery mode optical resonator formed of a dielectric material that allows for direct modulation of optical absorption by the electrical signal.

High-efficiency second harmonic generation from a single hybrid ZnO nanowire/Au plasmonic nano-oligomer.

PubMed

Grinblat, Gustavo; Rahmani, Mohsen; Cortés, Emiliano; Caldarola, Martín; Comedi, David; Maier, Stefan A; Bragas, Andrea V

2014-11-12

We introduce a plasmonic-semiconductor hybrid nanosystem, consisting of a ZnO nanowire coupled to a gold pentamer oligomer by crossing the hot-spot. It is demonstrated that the hybrid system exhibits a second harmonic (SH) conversion efficiency of ∼3 × 10(-5)%, which is among the highest values for a nanoscale object at optical frequencies reported so far. The SH intensity was found to be ∼1700 times larger than that from the same nanowire excited outside the hot-spot. Placing high nonlinear susceptibility materials precisely in plasmonic confined-field regions to enhance SH generation opens new perspectives for highly efficient light frequency up-conversion on the nanoscale.

Enhanced conversion efficiency in wide-bandgap GaNP solar cells

DOE PAGES

Sukrittanon, Supanee; Liu, Ren; Ro, Yun Goo; ...

2015-10-12

In this study, we demonstrate –2.05 eV dilute nitride GaNP solar cells on GaP substrates for potential use as the top junction in dual-junction integrated cells on Si. By adding a small amount of N into indirect-bandgap GaP, GaNP has several extremely important attributes: a direct-bandgap that is also tunable, and easily attained lattice-match with Si. Our best GaNP solar cell ([N] –1.8%, E g –2.05 eV) achieves an efficiency of 7.9%, even in the absence of a window layer. This GaNP solar cell's efficiency is 3× higher than the most efficient GaP solar cell to date and higher thanmore » other solar cells with similar direct bandgap (InGaP, GaAsP). Through a systematic study of the structural, electrical, and optical properties of the device, efficient broadband optical absorption and enhanced solar cell performance are demonstrated.« less

Ultrafast laser direct hard-mask writing for high efficiency c-Si texture designs

NASA Astrophysics Data System (ADS)

Kumar, Kitty; Lee, Kenneth K. C.; Nogami, Jun; Herman, Peter R.; Kherani, Nazir P.

2013-03-01

This study reports a high-resolution hard-mask laser writing technique to facilitate the selective etching of crystalline silicon (c-Si) into an inverted-pyramidal texture with feature size and periodicity on the order of the wavelength which, thus, provides for both anti-reflection and effective light-trapping of infrared and visible light. The process also enables engineered positional placement of the inverted-pyramid thereby providing another parameter for optimal design of an optically efficient pattern. The proposed technique, a non-cleanroom process, is scalable for large area micro-fabrication of high-efficiency thin c-Si photovoltaics. Optical wave simulations suggest the fabricated textured surface with 1.3 μm inverted-pyramids and a single anti-reflective coating increases the relative energy conversion efficiency by 11% compared to the PERL-cell texture with 9 μm inverted pyramids on a 400 μm thick wafer. This efficiency gain is anticipated to improve further for thinner wafers due to enhanced diffractive light trapping effects.

Highly efficient periodically poled KTP-isomorphs with large apertures and extreme domain aspect-ratios

NASA Astrophysics Data System (ADS)

Canalias, Carlota; Zukauskas, Andrius; Tjörnhamman, Staffan; Viotti, Anne-Lise; Pasiskevicius, Valdas; Laurell, Fredrik

2018-02-01

Since the early 1990's, a substantial effort has been devoted to the development of quasi-phased-matched (QPM) nonlinear devices, not only in ferroelectric oxides like LiNbO3, LiTaO3 and KTiOPO4 (KTP), but also in semiconductors as GaAs, and GaP. The technology to implement QPM structures in ferroelectric oxides has by now matured enough to satisfy the most basic frequency-conversion schemes without substantial modification of the poling procedures. Here, we present a qualitative leap in periodic poling techniques that allows us to demonstrate devices and frequency conversion schemes that were deemed unfeasible just a few years ago. Thanks to our short-pulse poling and coercive-field engineering techniques, we are able to demonstrate large aperture (5 mm) periodically poled Rb-doped KTP devices with a highly-uniform conversion efficiency over the whole aperture. These devices allow parametric conversion with energies larger than 60 mJ. Moreover, by employing our coercive-field engineering technique we fabricate highlyefficient sub-µm periodically poled devices, with periodicities as short as 500 nm, uniform over 1 mm-thick crystals, which allow us to realize mirrorless optical parametric oscillators with counter-propagating signal and idler waves. These novel devices present unique spectral and tuning properties, superior to those of conventional OPOs. Furthermore, our techniques are compatible with KTA, a KTP isomorph with extended transparency in the mid-IR range. We demonstrate that our highly-efficient PPKTA is superior both for mid-IR and for green light generation - as a result of improved transmission properties in the visible range. Our KTP-isomorph poling techniques leading to highly-efficient QPM devices will be presented. Their optical performance and attractive damage thresholds will be discussed.

Reduced Dimensionality Lithium Niobate Microsystems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eichenfield, Matt

2017-01-01

The following report describes work performed under the LDRD program at Sandia National Laboratories October 2014 and September 2016. The work presented demonstrates the ability of Sandia Labs to develop state-of-the-art photonic devices based on thin film lithium niobate (LiNbO 3 ). Section 1 provides an introduction to integrated LiNbO 3 devices and motivation for developing thin film nonlinear optical systems. Section 2 describes the design, fabrication, and photonic performance of thin film optical microdisks fabricated from bulk LiNbO 3 using a bulk implantation method developed at Sandia. Sections 3 and 4 describe the development of similar thin film LiNbOmore » 3 structures fabricated from LiNbO 3 on insulator (LNOI) substrates and our demonstration of optical frequency conversion with state-of-the-art efficiency. Finally, Section 5 describes similar microdisk resonators fabricated from LNOI wafers with a buried metal layer, in which we demonstrate electro-optic modulation.« less

Mid-infrared optical frequency combs at 2.5 μm based on crystalline microresonators

PubMed Central

Wang, C. Y.; Herr, T.; Del’Haye, P.; Schliesser, A.; Hofer, J.; Holzwarth, R.; Hänsch, T. W.; Picqué, N.; Kippenberg, T. J.

2013-01-01

The mid-infrared spectral range (λ~2–20 μm) is of particular importance as many molecules exhibit strong vibrational fingerprints in this region. Optical frequency combs—broadband optical sources consisting of equally spaced and mutually coherent sharp lines—are creating new opportunities for advanced spectroscopy. Here we demonstrate a novel approach to create mid-infrared optical frequency combs via four-wave mixing in a continuous-wave pumped ultra-high Q crystalline microresonator made of magnesium fluoride. Careful choice of the resonator material and design made it possible to generate a broadband, low-phase noise Kerr comb at λ=2.5 μm spanning 200 nm (≈10 THz) with a line spacing of 100 GHz. With its distinguishing features of compactness, efficient conversion, large mode spacing and high power per comb line, this novel frequency comb source holds promise for new approaches to molecular spectroscopy and is suitable to be extended further into the mid-infrared. PMID:23299895

Effect of back reflectors on photon absorption in thin-film amorphous silicon solar cells

NASA Astrophysics Data System (ADS)

Hossain, Mohammad I.; Qarony, Wayesh; Hossain, M. Khalid; Debnath, M. K.; Uddin, M. Jalal; Tsang, Yuen Hong

2017-10-01

In thin-film solar cells, the photocurrent conversion productivity can be distinctly boosted-up utilizing a proper back reflector. Herein, the impact of different smooth and textured back reflectors was explored and effectuated to study the optical phenomena with interface engineering strategies and characteristics of transparent contacts. A unique type of wet-chemically textured glass-substrate 3D etching mask used in superstrate (p-i-n) amorphous silicon-based solar cell along with legitimated back reflector permits joining the standard light-trapping methodologies, which are utilized to upgrade the energy conversion efficiency (ECE). To investigate the optical and electrical properties of solar cell structure, the optical simulations in three-dimensional measurements (3D) were performed utilizing finite-difference time-domain (FDTD) technique. This design methodology allows to determine the power losses, quantum efficiencies, and short-circuit current densities of various layers in such solar cell. The short-circuit current densities for different reflectors were varied from 11.50 to 13.27 and 13.81 to 16.36 mA/cm2 for the smooth and pyramidal textured solar cells, individually. Contrasted with the comparable flat reference cell, the short-circuit current density of textured solar cell was increased by around 24%, and most extreme outer quantum efficiencies rose from 79 to 86.5%. The photon absorption was fundamentally improved in the spectral region from 600 to 800 nm with no decrease of photocurrent shorter than 600-nm wavelength. Therefore, these optimized designs will help to build the effective plans next-generation amorphous silicon-based solar cells.

Simultaneous parametric generation and up-conversion of entangled optical images

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saygin, M. Yu., E-mail: mihasyu@gmail.com; Chirkin, A. S., E-mail: aschirkin@rambler.r

A quantum theory of parametric amplification and frequency conversion of an optical image in coupled nonlinear optical processes that include one parametric amplification process at high-frequency pumping and two up-conversion processes in the same pump field is developed. The field momentum operator that takes into account the diffraction and group velocities of the waves is used to derive the quantum equations related to the spatial dynamics of the images during the interaction. An optical scheme for the amplification and conversion of a close image is considered. The mean photon number density and signal-to-noise ratio are calculated in the fixed-pump-field approximationmore » for images at various frequencies. It has been established that the signal-to-noise ratio decreases with increasing interaction length in the amplified image and increases in the images at the generated frequencies, tending to asymptotic values for all interacting waves. The variance of the difference of the numbers of photons is calculated for various pairs of frequencies. The quantum entanglement of the optical images formed in a high-frequency pump field is shown to be converted to higher frequencies during the generation of sum frequencies. Thus, two pairs of entangled optical images are produced in the process considered.« less

A low-latency optical switch architecture using integrated μm SOI-based contention resolution and switching

NASA Astrophysics Data System (ADS)

Mourgias-Alexandris, G.; Moralis-Pegios, M.; Terzenidis, N.; Cherchi, M.; Harjanne, M.; Aalto, T.; Vyrsokinos, K.; Pleros, N.

2018-02-01

The urgent need for high-bandwidth and high-port connectivity in Data Centers has boosted the deployment of optoelectronic packet switches towards bringing high data-rate optics closer to the ASIC, realizing optical transceiver functions directly at the ASIC package for high-rate, low-energy and low-latency interconnects. Even though optics can offer a broad range of low-energy integrated switch fabrics for replacing electronic switches and seamlessly interface with the optical I/Os, the use of energy- and latency-consuming electronic SerDes continues to be a necessity, mainly dictated by the absence of integrated and reliable optical buffering solutions. SerDes undertakes the role of optimally synergizing the lower-speed electronic buffers with the incoming and outgoing optical streams, suggesting that a SerDes-released chip-scale optical switch fabric can be only realized in case all necessary functions including contention resolution and switching can be implemented on a common photonic integration platform. In this paper, we demonstrate experimentally a hybrid Broadcast-and-Select (BS) / wavelength routed optical switch that performs both the optical buffering and switching functions with μm-scale Silicon-integrated building blocks. Optical buffering is carried out in a silicon-integrated variable delay line bank with a record-high on-chip delay/footprint efficiency of 2.6ns/mm2 and up to 17.2 nsec delay capability, while switching is executed via a BS design and a silicon-integrated echelle grating, assisted by SOA-MZI wavelength conversion stages and controlled by a FPGA header processing module. The switch has been experimentally validated in a 3x3 arrangement with 10Gb/s NRZ optical data packets, demonstrating error-free switching operation with a power penalty of <5dB.

Performance characteristics of proximity focused ultraviolet image converters

NASA Technical Reports Server (NTRS)

Williams, J. T.; Feibelman, W. A.

1973-01-01

Performance characteristics of Bendix type BX 8025-4522 proximity focused image tubes for ultraviolet to visible light conversion are presented. Quantum efficiency, resolution, background, geometric distortion, and environmental test results are discussed. The converters use magnesium fluoride input windows with Cs - Te photocathodes, and P-11 phosphors on fiber optic output windows.

Performance characteristics of proximity focused ultraviolet image converters

NASA Technical Reports Server (NTRS)

Williams, J. T.; Feibelman, W. A.

1973-01-01

Performance characteristics of Bendix type BX 8025-4522 proximity focused image tubes for UV to visible light conversion are presented. Quantum efficiency, resolution, background, geometric distortion, and environmental test results are discussed. The converters use magnesium fluoride input windows with Cs-Te photocathodes and P-11 phosphors on fiber optic output windows.

All-optical wavelength conversion for mode division multiplexed superchannels.

PubMed

Gong, Jiaxin; Xu, Jing; Luo, Ming; Li, Xiang; Qiu, Ying; Yang, Qi; Zhang, Xinliang; Yu, Shaohua

2016-04-18

We report in this work the first all-optical wavelength conversion (AOWC) of a mode division multiplexed (MDM) superchannel consisting of 2N modes by dividing the superchannel into N single-mode (SM) tributaries, wavelength converting N SM signals using well developed SM-AOWC techniques, and finally combining the N SM tributaries back to an MDM superchannel at the converted wavelength, inspired by the idea of using SM filtering techniques to filter multimode signals in astronomy. The conversions between multimode and SM are realized by 3D laser-writing photonic lanterns and SM-AOWCs are realized based on polarization insensitive four wave mixing (FWM) configuration in N semiconductor optical amplifiers (SOAs). As a proof of concept demonstration, the conversion of a 6-mode MDM superchannel with each mode modulated with orthogonal frequency division multiplexed (OFDM) quadrature phase-shift keying (QPSK)/16 quadrature amplitude modulation (QAM) signals is demonstrated in this work, indicating that the scheme is transparent to data format, polarization and compatible with multi-carrier signals. Data integrity of the converted superchannel has been verified by using coherent detection and digital signal processing (DSP). Bit error rates (BERs) below the forward error correction (FEC) hard limit (3.8 × 10^-3) have been obtained for QPSK modulation at a net bitrate of 104.2 Gbit/s and BERs below the soft decision FEC threshold (1.98 × 10^-2) have been achieved for 16-QAM format, giving a total aggregate bit rate of 185.8 Gbit/s when taking 20% coding overhead into account. Add and drop functionalities that usually come along with wavelength conversion in flexible network nodes have also been demonstrated. The working conditions of the SOAs, especially the pump and signal power levels, are critical for the quality of the converted signal and have been thoroughly discussed. The impact of imbalanced FWM conversion efficiency among different SM tributaries has also been analyzed. This work illustrates a promising way to perform all-optical signal processing for MDM superchannels.

Optical, electrical, and photovoltaic properties of PbS thin films by anionic and cationic dopants

NASA Astrophysics Data System (ADS)

Cheraghizade, Mohsen; Jamali-Sheini, Farid; Yousefi, Ramin

2017-06-01

Lead sulfide (PbS) thin films were deposited by CVD method to examine the effects of anionic and cationic dopants on optical and electrical properties for photovoltaic applications. XRD diffractograms verified the formation of cubic phase of multicrystalline PbS thin films. FESEM images showed surface morphologies in nano-dimensions (rods and flowers). UV-Vis-NIR spectrum revealed absorbance in the visible and NIR regions for all samples, in which dopants decreased the intensity of absorbance. Se as an anionic dopant for PbS thin films increased electrical resistance, acceptor concentrations, and crystallite defects, and decreased flat-band voltage and depletion width. Finally, photovoltaic measurements indicated that Zn-doped PbS thin film, as a photovoltaic cell, exhibited higher conversion efficiency and external quantum efficiency (EQE).

Passively Q-switched Nd:YAG/Cr(4+):YAG bonded crystal microchip laser operating at 1112  nm and its application for second-harmonic generation.

PubMed

Fu, S G; Ouyang, X Y; Liu, X J

2015-10-10

A passively Q-switched Nd:YAG/Cr⁴⁺:YAG microchip laser operating at 1112 nm is demonstrated. Under a pump power of 5.5 W, a maximum average output power of 623 mW was obtained with T=6% output coupler, corresponding to an optical-to-optical conversion efficiency of 11.3% and a slope efficiency of 19.5%. The minimum pulse width was 2.8 ns, the pulse energy and peak power were 39.3 μJ and 14 kW, respectively. Additionally, based on the 1112 nm laser, a 230 mW 556 nm green-yellow laser was achieved within an LBO crystal.

Orbit-induced localized spin angular momentum in strong focusing of optical vectorial vortex beams

NASA Astrophysics Data System (ADS)

Li, Manman; Cai, Yanan; Yan, Shaohui; Liang, Yansheng; Zhang, Peng; Yao, Baoli

2018-05-01

Light beams may carry optical spin or orbital angular momentum, or both. The spin and orbital parts manifest themselves by the ellipticity of the state of polarization and the vortex structure of phase of light beams, separately. Optical spin and orbit interaction, arising from the interaction between the polarization and the spatial structure of light beams, has attracted enormous interest recently. The optical spin-to-orbital angular momentum conversion under strong focusing is well known, while the converse process, orbital-to-spin conversion, has not been reported so far. In this paper, we predict in theory that the orbital angular momentum can induce a localized spin angular momentum in strong focusing of a spin-free azimuthal polarization vortex beam. This localized longitudinal spin of the focused field can drive the trapped particle to spin around its own axis. This investigation provides a new degree of freedom for spinning particles by using a vortex phase, which may have considerable potentials in optical spin and orbit interaction, light-beam shaping, or optical manipulation.

Incident light adjustable solar cell by periodic nanolens architecture

PubMed Central

Yun, Ju-Hyung; Lee, Eunsongyi; Park, Hyeong-Ho; Kim, Dong-Wook; Anderson, Wayne A.; Kim, Joondong; Litchinitser, Natalia M.; Zeng, Jinwei; Yi, Junsin; Kumar, M. Melvin David; Sun, Jingbo

2014-01-01

Could nanostructures act as lenses to focus incident light for efficient utilization of photovoltaics? Is it possible, in order to avoid serious recombination loss, to realize periodic nanostructures in solar cells without direct etching in a light absorbing semiconductor? Here we propose and demonstrate a promising architecture to shape nanolenses on a planar semiconductor. Optically transparent and electrically conductive nanolenses simultaneously provide the optical benefit of modulating the incident light and the electrical advantage of supporting carrier transportation. A transparent indium-tin-oxide (ITO) nanolens was designed to focus the incident light-spectrum in focal lengths overlapping to a strong electric field region for high carrier collection efficiency. The ITO nanolens effectively broadens near-zero reflection and provides high tolerance to the incident light angles. We present a record high light-conversion efficiency of 16.0% for a periodic nanostructured Si solar cell. PMID:25371099

High efficiency carrier multiplication in PbSe nanocrystals: implications for solar energy conversion.

PubMed

Schaller, R D; Klimov, V I

2004-05-07

We demonstrate for the first time that impact ionization (II) (the inverse of Auger recombination) occurs with very high efficiency in semiconductor nanocrystals (NCs). Interband optical excitation of PbSe NCs at low pump intensities, for which less than one exciton is initially generated per NC on average, results in the formation of two or more excitons (carrier multiplication) when pump photon energies are more than 3 times the NC band gap energy. The generation of multiexcitons from a single photon absorption event is observed to take place on an ultrafast (picosecond) time scale and occurs with up to 100% efficiency depending upon the excess energy of the absorbed photon. Efficient II in NCs can be used to considerably increase the power conversion efficiency of NC-based solar cells.

DiPOLE: a 10 J, 10 Hz cryogenic gas cooled multi-slab nanosecond Yb:YAG laser.

PubMed

Banerjee, Saumyabrata; Ertel, Klaus; Mason, Paul D; Phillips, P Jonathan; De Vido, Mariastefania; Smith, Jodie M; Butcher, Thomas J; Hernandez-Gomez, Cristina; Greenhalgh, R Justin S; Collier, John L

2015-07-27

The Diode Pumped Optical Laser for Experiments (DiPOLE) project at the Central Laser Facility aims to develop a scalable, efficient high pulse energy diode pumped laser amplifier system based on cryogenic gas cooled, multi-slab ceramic Yb:YAG technology. We present recent results obtained from a scaled down prototype laser system designed for operation at 10 Hz pulse repetition rate. At 140 K, the system generated 10.8 J of energy in a 10 ns pulse at 1029.5 nm when pumped by 48 J of diode energy at 940 nm, corresponding to an optical to optical conversion efficiency of 22.5%. To our knowledge, this represents the highest pulse energy obtained from a cryo cooled Yb laser to date and the highest efficiency achieved by a multi-Joule diode pumped solid state laser system. Additionally, we demonstrated shot-to-shot energy stability of 0.85% rms for the system operated at 7 J, 10 Hz during several runs lasting up to 6 hours, with more than 50 hours in total. We also demonstrated pulse shaping capability and report on beam, wavefront and focal spot quality.

Electrical and Optical Characterization of Sputtered Silicon Dioxide, Indium Tin Oxide, and Silicon Dioxide/Indium Tin Oxide Antireflection Coating on Single-Junction GaAs Solar Cells

PubMed Central

Ho, Wen-Jeng; Lin, Jian-Cheng; Liu, Jheng-Jie; Bai, Wen-Bin; Shiao, Hung-Pin

2017-01-01

This study characterized the electrical and optical properties of single-junction GaAs solar cells coated with antireflective layers of silicon dioxide (SiO2), indium tin oxide (ITO), and a hybrid layer of SiO2/ITO applied using Radio frequency (RF) sputtering. The conductivity and transparency of the ITO film were characterized prior to application on GaAs cells. Reverse saturation-current and ideality factor were used to evaluate the passivation performance of the various coatings on GaAs solar cells. Optical reflectance and external quantum efficiency response were used to evaluate the antireflective performance of the coatings. Photovoltaic current-voltage measurements were used to confirm the efficiency enhancement obtained by the presence of the anti-reflective coatings. The conversion efficiency of the GaAs cells with an ITO antireflective coating (23.52%) exceeded that of cells with a SiO2 antireflective coating (21.92%). Due to lower series resistance and higher short-circuit current-density, the carrier collection of the GaAs cell with ITO coating exceeded that of the cell with a SiO2/ITO coating. PMID:28773063

Neutral Silicon-Vacancy Center in Diamond: Spin Polarization and Lifetimes

NASA Astrophysics Data System (ADS)

Green, B. L.; Mottishaw, S.; Breeze, B. G.; Edmonds, A. M.; D'Haenens-Johansson, U. F. S.; Doherty, M. W.; Williams, S. D.; Twitchen, D. J.; Newton, M. E.

2017-09-01

We demonstrate optical spin polarization of the neutrally charged silicon-vacancy defect in diamond (SiV0 ), an S =1 defect which emits with a zero-phonon line at 946 nm. The spin polarization is found to be most efficient under resonant excitation, but nonzero at below-resonant energies. We measure an ensemble spin coherence time T2>100 μ s at low-temperature, and a spin relaxation limit of T1>25 s . Optical spin-state initialization around 946 nm allows independent initialization of SiV0 and NV- within the same optically addressed volume, and SiV0 emits within the telecoms down-conversion band to 1550 nm: when combined with its high Debye-Waller factor, our initial results suggest that SiV0 is a promising candidate for a long-range quantum communication technology.

Normal dispersion femtosecond fiber optical parametric oscillator.

PubMed

Nguyen, T N; Kieu, K; Maslov, A V; Miyawaki, M; Peyghambarian, N

2013-09-15

We propose and demonstrate a synchronously pumped fiber optical parametric oscillator (FOPO) operating in the normal dispersion regime. The FOPO generates chirped pulses at the output, allowing significant pulse energy scaling potential without pulse breaking. The output average power of the FOPO at 1600 nm was ∼60  mW (corresponding to 1.45 nJ pulse energy and ∼55% slope power conversion efficiency). The output pulses directly from the FOPO were highly chirped (∼3  ps duration), and they could be compressed outside of the cavity to 180 fs by using a standard optical fiber compressor. Detailed numerical simulation was also performed to understand the pulse evolution dynamics around the laser cavity. We believe that the proposed design concept is useful for scaling up the pulse energy in the FOPO using different pumping wavelengths.

Plasmonic mode converter for controlling optical impedance and nanoscale light-matter interaction.

PubMed

Hung, Yun-Ting; Huang, Chen-Bin; Huang, Jer-Shing

2012-08-27

To enable multiple functions of plasmonic nanocircuits, it is of key importance to control the propagation properties and the modal distribution of the guided optical modes such that their impedance matches to that of nearby quantum systems and desired light-matter interaction can be achieved. Here, we present efficient mode converters for manipulating guided modes on a plasmonic two-wire transmission line. The mode conversion is achieved through varying the path length, wire cross section and the surrounding index of refraction. Instead of pure optical interference, strong near-field coupling of surface plasmons results in great momentum splitting and modal profile variation. We theoretically demonstrate control over nanoantenna radiation and discuss the possibility to enhance nanoscale light-matter interaction. The proposed converter may find applications in surface plasmon amplification, index sensing and enhanced nanoscale spectroscopy.

Applied nonlinear optics in the journal 'Quantum Electronics'

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grechin, Sergei G; Dmitriev, Valentin G; Chirkin, Anatolii S

2011-12-31

A brief historical review of the experimental and theoretical works on nonlinear optical frequency conversion (generation of harmonics, up- and down-conversion, parametric oscillation), which have been published in the journal 'Quantum Electronics' for the last 40 years, is presented.

Broadband wavelength conversion in hydrogenated amorphous silicon waveguide with silicon nitride layer

NASA Astrophysics Data System (ADS)

Wang, Jiang; Li, Yongfang; Wang, Zhaolu; Han, Jing; Huang, Nan; Liu, Hongjun

2018-01-01

Broadband wavelength conversion based on degenerate four-wave mixing is theoretically investigated in a hydrogenated amorphous silicon (a-Si:H) waveguide with silicon nitride inter-cladding layer (a-Si:HN). We have found that enhancement of the non-linear effect of a-Si:H waveguide nitride intermediate layer facilitates broadband wavelength conversion. Conversion bandwidth of 490 nm and conversion efficiency of 11.4 dB were achieved in a numerical simulation of a 4 mm-long a-Si:HN waveguide under 1.55 μm continuous wave pumping. This broadband continuous-wave wavelength converter has potential applications in photonic networks, a type of readily manufactured low-cost highly integrated optical circuits.

Tunable all-optical signal regenerator with a semiconductor optical amplifier and a Sagnac loop: principles of operation

NASA Astrophysics Data System (ADS)

Granot, Er'el; Zaibel, Reuven; Narkiss, Niv; Ben-Ezra, Shalva; Chayet, Haim; Shahar, Nir; Sternklar, Shmuel; Tsadka, Sagie; Prucnal, Paul R.

2005-12-01

In this paper we investigate the wavelength conversion and regeneration properties of a tunable all-optical signal regenerator (TASR). In the TASR, the wavelength conversion is done by a semiconductor optical amplifier, which is incorporated in an asymmetric Sagnac loop (ASL). We demonstrate both theoretically and experimentally that the ASL regenerates the incident signal's bit pattern, reduces its noise, increases the extinction ratio (which in many aspects is equivalent to noise reduction) and improves its bit-error rate. We also demonstrate the general behavior of the TASR with a numerical simulation.

A material combination principle for highly efficient polymer solar cells investigated by mesoscopic phase heterogeneity

NASA Astrophysics Data System (ADS)

Yan, Han; Li, Denghua; He, Chang; Wei, Zhixiang; Yang, Yanlian; Li, Yongfang

2013-11-01

Organic solar cells have become a promising energy conversion candidate because of their unique advantages. Novel fullerene derivatives, as a common acceptor, can increase power conversion efficiency (PCE) by increasing the open-circuit voltage. As a representative acceptor, Indene-C60 bisadduct (ICBA) can reach high efficiency with poly(3-hexylthiophene) (P3HT). On the other hand, the novel synthesized polymers mainly aimed to broaden the optical absorption range have steadily promoted efficiency to higher than 9%. However, it is challenging to obtain the desired result by simply combining ICBA with other high-efficiency donors. Thus, P3HT or a high-efficiency polymer PBDTTT-C-T (copolymer of thienyl-substituted BDT with substituted TT) is used as donor and PCBM or ICBA as acceptor in this article to clarify the mechanism behind these materials. The optical and photovoltaic properties of the materials are studied for pair-wise combination. Among these four material groups, the highest PCE of 6.2% is obtained for the PBDTTT-C-T/PCBM combination while the lowest PCE of 3.5% is obtained for the PBDTTT-C-T/ICBA combination. The impact of the mesoscopic heterogeneity on the local mesoscopic photoelectric properties is identified by photo-conductive AFM (pc-AFM), and the consistence between the mesoscopic properties and the macroscopic device performances is also observed. Based on these results, an interface combined model is proposed based on the mesoscopic phase heterogeneity. This study provides a new view on the rational selection of photovoltaic materials, where, aside from the traditional energy level and absorption spectrum matching, the matching of mesoscopic heterogeneity must also be considered.Organic solar cells have become a promising energy conversion candidate because of their unique advantages. Novel fullerene derivatives, as a common acceptor, can increase power conversion efficiency (PCE) by increasing the open-circuit voltage. As a representative acceptor, Indene-C60 bisadduct (ICBA) can reach high efficiency with poly(3-hexylthiophene) (P3HT). On the other hand, the novel synthesized polymers mainly aimed to broaden the optical absorption range have steadily promoted efficiency to higher than 9%. However, it is challenging to obtain the desired result by simply combining ICBA with other high-efficiency donors. Thus, P3HT or a high-efficiency polymer PBDTTT-C-T (copolymer of thienyl-substituted BDT with substituted TT) is used as donor and PCBM or ICBA as acceptor in this article to clarify the mechanism behind these materials. The optical and photovoltaic properties of the materials are studied for pair-wise combination. Among these four material groups, the highest PCE of 6.2% is obtained for the PBDTTT-C-T/PCBM combination while the lowest PCE of 3.5% is obtained for the PBDTTT-C-T/ICBA combination. The impact of the mesoscopic heterogeneity on the local mesoscopic photoelectric properties is identified by photo-conductive AFM (pc-AFM), and the consistence between the mesoscopic properties and the macroscopic device performances is also observed. Based on these results, an interface combined model is proposed based on the mesoscopic phase heterogeneity. This study provides a new view on the rational selection of photovoltaic materials, where, aside from the traditional energy level and absorption spectrum matching, the matching of mesoscopic heterogeneity must also be considered. Electronic Supplementary Information (ESI) available. See DOI: 10.1039/c3nr03165a

Characterization and cysteine sensing performance of nanocomposites based on up-conversion excitation host and rhodamine-derived probes

NASA Astrophysics Data System (ADS)

Yuqing, Zhao; Yi, Xing; Lihua, Li; Juanjuan, Ma

2018-02-01

Optical sensing for cysteine (Cys) recognition is an interesting topic due to Cys biological participation. In this paper, two rhodamine-based chemosensors were designed for Cys optical sensing. For chemosensor photostability improvement, up-conversion nanocrystals were synthesized and used as excitation host. These nanocrystals were modified with a phase transfer reagent α-cyclodextrin (α-CD) to improve their compatibility with chemosensors. An efficient energy transfer from these nanocrystals to chemosensors under 980 nm radiation was observed and confirmed by spectral match analysis, energy transfer radius calculation and emission decay lifetime comparison. A direct bonding mechanism between Cys and chemosensors with bonding stoichiometry of 1:1 was established by Job's plot experiment. Given the presence of Cys, chemosensor emission was increased, showing emission turn on effect. These two chemosensors showed good selectivity, improved photostability and linear sensing response towards Cys.

Conversion efficiency limits and bandgap designs for multi-junction solar cells with internal radiative efficiencies below unity.

PubMed

Zhu, Lin; Mochizuki, Toshimitsu; Yoshita, Masahiro; Chen, Shaoqiang; Kim, Changsu; Akiyama, Hidefumi; Kanemitsu, Yoshihiko

2016-05-16

We calculated the conversion-efficiency limit ηsc and the optimized subcell bandgap energies of 1 to 5 junction solar cells without and with intermediate reflectors under 1-sun AM1.5G and 1000-sun AM1.5D irradiations, particularly including the impact of internal radiative efficiency (ηint) below unity for realistic subcell materials on the basis of an extended detailed-balance theory. We found that the conversion-efficiency limit ηsc significantly drops when the geometric mean ηint* of all subcell ηint in the stack reduces from 1 to 0.1, and that ηsc degrades linearly to logηint* for ηint* below 0.1. For ηint*<0.1 differences in ηsc due to additional intermediate reflectors became very small if all subcells are optically thick for sun light. We obtained characteristic optimized bandgap energies, which reflect both ηint* decrease and AM1.5 spectral gaps. These results provide realistic efficiency targets and design principles.

Diode pumped passively Q-switched Nd:LuAG laser at 1442.6 nm

NASA Astrophysics Data System (ADS)

Guan, Chen; Liu, Zhaojun; Cong, Zhenhua; Liu, Yang; Xu, Xiaodong; Xu, Jun; Huang, Qingjie; Rao, Han; Chen, Xia; Zhang, Yanmin; Wu, Qianwen; Bai, Fen; Zhang, Sasa

2017-02-01

A diode-end-pumped passively Q-switched Nd:LuAG laser at 1442.6 nm was demonstrated with a V3+:YAG crystal as the saturable absorber. Under continuous-wave (CW) operation, the maximum output power of 1.83 W was obtained with an absorbed pumping power of 11.1 W. The corresponding optical-to-optical conversion efficiency was 16.5%. Under Q-switched operation, the maximum average output power of 424 mW was obtained at the same pumping power. The pulse duration and pulse repetition rate were 72 ns and 17.4 kHz, respectively.

Multi-wavelength and multiband RE-doped optical fiber source array for WDM-GPON applications

NASA Astrophysics Data System (ADS)

Perez-Sanchez, G. G.; Bertoldi-Martins, I.; Gallion, P.; Gosset, C.; Álvarez-Chávez, J. A.

2013-12-01

In this paper, a multiband, multi-wavelength, all-fibre source array consisting of an 810nm pump laser diode, thretwo fiber splitters and three segments of Er-, Tm- and Nd-doped fiber is proposed for PON applications. In the set-up, cascaded pairs of standard fiber gratings are used for extracting the required multiple wavelengths within their corresponding bands. A thorough design parameter description, optical array details and full simulation results, such as: full multi-wavelength spectrum, peak and average powers for each generated wavelength, linewidth at FWHM for each generated signal, and individual and overall conversion efficiency, will be included in the manuscript.

High-Power Nd:GdVO4 Innoslab Continuous-Wave Laser under Direct 880 nm Pumping

NASA Astrophysics Data System (ADS)

Deng, Bo; Zhang, Heng-Li; Xu, Liu; Mao, Ye-Fei; He, Jing-Liang; Xin, Jian-Guo

2014-11-01

A high-power cw end-pumped laser device is demonstrated with a slab crystal of Nd:GdVO4 operating at 1063 nm. Diode laser stacks at 880 nm are used to pump Nd:GdVO4 into emitting level 4F3/2. The 149 W output power is presented when the absorbed pump power is 390 W and the optical-to-optical conversion efficiency is 38.2%. When the output power is 120 W, the M2 factors are 2.3 in both directions. Additionally, mode overlap inside the resonator is analyzed to explain the beam quality deterioration.

Reconfigurable radio-over-fiber system based on optical switch and tunable filter

NASA Astrophysics Data System (ADS)

Li, Xiao; Yin, Rui; Ji, Wei; Sun, Kai; Zhang, Shicheng

2017-09-01

As the best candidate for wireless-access networks, radio-over-fiber (RoF) technology can carry a variety of business. It is necessary to provide differentiated services for different users, so the network needs to produce signals with different modulation formats and different frequencies. A reconfigurable RoF system based on a switch and tunable optical filter that can realize modulation format conversion and multiple frequency signal switching functions is designed. It has a good performance in terms of bit error rate and an eye diagram. The design can help to use radio frequency resources efficiently and make dynamic bandwidth resources controllable.

Effects of chirp of pump pulses on broadband terahertz pulse spectra generated by optical rectification

NASA Astrophysics Data System (ADS)

Hamazaki, Junichi; Furusawa, Kentaro; Sekine, Norihiko; Kasamatsu, Akifumi; Hosako, Iwao

2016-11-01

The effects of the chirp of the pump pulse in broadband terahertz (THz) pulse generation by optical rectification (OR) in GaP were systematically investigated. It was found that the pre-compensation for the dispersion of GaP is important for obtaining smooth and single-peaked THz spectra as well as high power-conversion efficiency. It was also found that an excessive amount of chirp leads to distortions in THz spectra, which can be quantitatively analyzed by using a simple model. Our results highlight the importance of accurate control over the chirp of the pump pulse for generating broadband THz pulses by OR.

107 Gb/s coherent optical OFDM transmission over 1000-km SSMF fiber using orthogonal band multiplexing.

PubMed

Shieh, W; Yang, Q; Ma, Y

2008-04-28

Coherent optical OFDM (CO-OFDM) has emerged as an attractive modulation format for the forthcoming 100 Gb/s Ethernet. However, even the spectral-efficient implementation of CO-OFDM requires digital-to-analog converters (DAC) and analog-to-digital converters (ADC) to operate at the bandwidth which may not be available today or may not be cost-effective. In order to resolve the electronic bandwidth bottleneck associated with DAC/ADC devices, we propose and elucidate the principle of orthogonal-band-multiplexed OFDM (OBM-OFDM) to subdivide the entire OFDM spectrum into multiple orthogonal bands. With this scheme, the DAC/ADCs do not need to operate at extremely high sampling rate. The corresponding mapping to the mixed-signal integrated circuit (IC) design is also revealed. Additionally, we show the proof-of-concept transmission experiment through optical realization of OBM-OFDM. To the best of our knowledge, we present the first experimental demonstration of 107 Gb/s QPSK-encoded CO-OFDM signal transmission over 1000 km standard-single- mode-fiber (SSMF) without optical dispersion compensation and without Raman amplification. The demonstrated system employs 2x2 MIMO-OFDM signal processing and achieves high electrical spectral efficiency with direct-conversion at both transmitter and receiver.

Thermal, spectroscopic and laser properties of Nd3+ in gadolinium scandium gallium garnet crystal produced by optical floating zone method

NASA Astrophysics Data System (ADS)

Tian, Li; Wang, Shuxian; Wu, Kui; Wang, Baolin; Yu, Haohai; Zhang, Huaijin; Cai, Huaqiang; Huang, Hui

2013-12-01

A neodymium-doped gadolinium scandium gallium garnet (Nd:GSGG) single crystal with dimensions of Φ 5 × 20 mm2 has been grown by means of optical floating zone (OFZ). X-ray powder diffraction (XRPD) result shows that the as-grown Nd:GSGG crystal possesses a cubic structure with space group Ia3d and a cell parameter of a = 1.2561 nm. Effective elemental segregation coefficients of the Nd:GSGG as-grown crystal were calculated by using X-ray fluorescence (XRF). The thermal properties of the Nd:GSGG crystal were systematically studied by measuring the specific heat, thermal expansion and thermal diffusion coefficient, and the thermal conductivity of this crystal was calculated. The absorption and luminescence spectra of Nd:GSGG were measured at room temperature (RT). By using the Judd-Ofelt (J-O) theory, the theoretical radiative lifetime was calculated and compared with the experimental result. Continuous wave (CW) laser performance was achieved with the Nd:GSGG at the wavelength of 1062 nm when it was pumped by a laser diode (LD). A maximum output power of 0.792 W at 1062 nm was obtained with a slope efficiency of 11.89% under a pump power of 7.36 W, and an optical-optical conversion efficiency of 11.72%.

Photoassisted electrolysis of water - Conversion of optical to chemical energy

NASA Technical Reports Server (NTRS)

Wrighton, M. S.; Bolts, J. M.; Kaiser, S. W.; Ellis, A. B.

1976-01-01

A description is given of devices, termed photoelectrochemical cells, which can, in principle, be used to directly convert light to fuels and/or electricity. The fundamental principles on which the photoelectrochemical cell is based are related to the observation that irradiation of a semiconductor electrode in an electrochemical cell can result in the flow of an electric current in the external circuit. Attention is given to the basic mechanisms involved, the energy conversion efficiency, the advantages of photoelectrochemical cells, and the results of investigations related to the study of energy conversion via photoelectrochemical cells.

Reversible Structural Swell-Shrink and Recoverable Optical Properties in Hybrid Inorganic-Organic Perovskite.

PubMed

Zhang, Yupeng; Wang, Yusheng; Xu, Zai-Quan; Liu, Jingying; Song, Jingchao; Xue, Yunzhou; Wang, Ziyu; Zheng, Jialu; Jiang, Liangcong; Zheng, Changxi; Huang, Fuzhi; Sun, Baoquan; Cheng, Yi-Bing; Bao, Qiaoliang

2016-07-26

Ion migration in hybrid organic-inorganic perovskites has been suggested to be an important factor for many unusual behaviors in perovskite-based optoelectronics, such as current-voltage hysteresis, low-frequency giant dielectric response, and the switchable photovoltaic effect. However, the role played by ion migration in the photoelectric conversion process of perovskites is still unclear. In this work, we provide microscale insights into the influence of ion migration on the microstructure, stability, and light-matter interaction in perovskite micro/nanowires by using spatially resolved optical characterization techniques. We observed that ion migration, especially the migration of MA(+) ions, will induce a reversible structural swell-shrink in perovskites and recoverably affect the reflective index, quantum efficiency, light-harvesting, and photoelectric properties. The maximum ion migration quantity in perovskites was as high as approximately 30%, resulting in lattice swell or shrink of approximately 4.4%. Meanwhile, the evidence shows that ion migration in perovskites could gradually accelerate the aging of perovskites because of lattice distortion in the reversible structural swell-shrink process. Knowledge regarding reversible structural swell-shrink and recoverable optical properties may shed light on the development of optoelectronic and converse piezoelectric devices based on perovskites.

Nonlinear optical detection of terahertz-wave radiation from resonant tunneling diodes.

PubMed

Takida, Yuma; Nawata, Kouji; Suzuki, Safumi; Asada, Masahiro; Minamide, Hiroaki

2017-03-06

The sensitive detection of terahertz (THz)-wave radiation from compact sources at room temperature is crucial for real-world THz-wave applications. Here, we demonstrate the nonlinear optical detection of THz-wave radiation from continuous-wave (CW) resonant tunneling diodes (RTDs) at 0.58, 0.78, and 1.14 THz. The up-conversion process in a MgO:LiNbO₃ crystal under the noncollinear phase-matching condition offers efficient wavelength conversion from a THz wave to a near-infrared (NIR) wave that is detected using a commercial NIR photodetector. The minimum detection limit of CW THz-wave power is as low as 5 nW at 1.14 THz, corresponding to 2-aJ energy and 2.7 × 10³ photons within the time window of a 0.31-ns pump pulse. Our results show that the input frequency and power of RTD devices can be calibrated by measuring the output wavelength and energy of up-converted waves, respectively. This optical detection technique for compact electronic THz-wave sources will open up a new opportunity for the realization of real-world THz-wave applications.

Efficient THZ Source Based on Cascaded Optical Down-Conversion in Orientation-Patterned GaAs Structures

DTIC Science & Technology

2008-11-20

techniques for generating THz radiation [5], none of them provides a THz source which is simultaneously ( i ) compact, (ii) highly efficient, (iii...are very attractive for QPM THz-wave generation because of several appealing properties, namely ( i ) small THz absorption coefficient (smaller by an...with periodically- inverted crystalline orientation were used for QPM THz generation: ( i ) diffusion-bonded GaAs (DB-GaAs) [49], produced by

Optical ultra-wide-band pulse bipolar and shape modulation based on a symmetric PM-IM conversion architecture.

PubMed

Wang, Shiguang; Chen, Hongwei; Xin, Ming; Chen, Minghua; Xie, Shizhong

2009-10-15

A simple and feasible technique for ultra-wide-band (UWB) pulse bipolar modulation (PBM) and pulse shape modulation (PSM) in the optical domain is proposed and demonstrated. The PBM and PSM are performed using a symmetric phase modulation to intensity modulation conversion architecture, including a couple of phase modulators and an optical bandpass filter (OBPF). Two optical carriers, which are separately phase modulated by two appropriate electrical pulse patterns, are at the long- and short-wavelength linear slopes of the OBPF spectrum, respectively. The high-speed PBM and PSM without limit of chip length, polarity, and shape are implemented in simulation and are also verified by experiment. (c) 2009 Optical Society of America.

Rare-earth doped transparent nano-glass-ceramics: a new generation of photonic integrated devices

NASA Astrophysics Data System (ADS)

Rodríguez-Armas, Vicente Daniel; Tikhomirov, Victor K.; Méndez-Ramos, Jorge; Yanes, Angel C.; Del-Castillo, Javier; Furniss, David; Seddon, Angela B.

2007-05-01

We report on optical properties and prospect applications on rare-earth doped oxyfluoride precursor glass and ensuing nano-glass-ceramics. We find out the spectral optical gain of the nano-glass-ceramics and show that its flatness and breadth are advantageous as compared to contemporary used erbium doped optical amplifiers. We present the possibility of flat gain cross-section erbium doped waveguide amplifiers as short 'chip', all-optical, devices capable of dense wavelength division multiplexing, including the potential for direct writing of these devices inside bulk glasses for three-dimensional photonic integration. We carried out a comparative study of the up-conversion luminescence in Er 3+-doped and Yb 3+-Er 3+-Tm 3+ co-doped samples, which indicates that these materials can be used as green/red tuneable up-conversion phosphors and white light simulation respectively. Observed changes in the spectra of the up-conversion luminescence provide a tool for tuning the colour opening the way for producing 3-dimensional optical recording.

Measuring parameters of large-aperture crystals used for generating optical harmonics

DOE Office of Scientific and Technical Information (OSTI.GOV)

English, R. E.; Hibbard, R. L.; Michie, R. B.

1999-02-23

The purpose of this project was to develop tools for understanding the influence of crystal quality and crystal mounting on harmonic-generation efficiency at high irradiance. Measuring the homogeneity of crystals interferometrically, making detailed physics calculations of conversion efficiency, performing finite- element modeling of mounted crystals, and designing a new optical metrology tool were key elements in obtaining that understanding. For this work, we used the following frequency-tripling scheme: type I second- harmonic generation followed by type II sum-frequency mixing of the residual fundamental and the second harmonic light. The doubler was potassium dihydrogen phosphate (KDP), and the tripler was deuteratedmore » KDP (KD*P). With this scheme, near-infrared light (1053 nm) can be frequency tripled (to 351 nm) at high efficiency (theoretically >90%) for high irradiance (>3 GW/cm²). Spatial variations in the birefringence of the large crystals studied here (37 to 41 cm square by about 1 cm thick) imply that the ideal phase-matching orientation of the crystal with respect to the incident laser beam varies across the crystal. We have shown that phase-measuring interferometry can be used to measure these spatial variations. We observed transmitted wavefront differences between orthogonally polarized interferograms of {lambda}/50 to {lambda}/100, which correspond to index variations of order 10 -6. On some plates that we measured, the standard deviation of angular errors is 22-23 µrad; this corresponds to a 1% reduction in efficiency. Because these conversion crystals are relatively thin, their surfaces are not flat (deviate by k2.5 urn from flat). A crystal is mounted against a precision-machined surface that supports the crystal on four edges. This mounting surface is not flat either (deviates by +2.5 µm from flat). A retaining flange presses a compliant element against the crystal. The load thus applied near the edges of the crystal surface holds it in place. We performed detailed finite-element modeling to predict the resulting shape of the mounted crystal. The prediction agreed with measurements of mounted crystals. We computed the physics of the frequency-conversion process to better quantify the effects on efficiency of variation in the crystal' s axis, changes in the shape of the crystal, and mounting-induced stress. We were able to accurately predict the frequency-conversion performance of 37-cm square crystals on Beamlet, a one-beam scientific prototype of the NIF laser architecture, using interferometric measurements of the mounted crystals and the model. In a 2{omega} measurement campaign, the model predicted 64.9% conversion efficiency; 64.1% was observed. When detuned by 640 µrad, the model and measurement agreement is even better (both were 10.4%). Finally, we completed the design and initial testing of a new optical metrology tool to measure the spatial variation of frequency conversion. This system employs a high-power subaperture beam from a commercial laser oscillator and rod amplifier. The beam interrogates the crystal' s aperture by moving the crystal horizontally on a translation stage and translating the laser beam vertically on an optical periscope. Precision alignment is maintained by means of a full-aperture reference mirror, a precision-machined surface on the crystal mount, and autocollimators (the goal for angular errors is 10 µrad). The autocollimators track the mounting angle of the crystal and the direction of the laser beam with respect to the reference mirror. The conversion efficiency can be directly measured by recording l{omega}, 2{omega}, 3{omega} energy levels during the scan and by rocking (i.e., tilting) the crystal mount over an angular range.« less

BPSK optical mm-wave signal generation by septupling frequency via a single optical phase modulator

NASA Astrophysics Data System (ADS)

Wu, Peng; Ma, Jianxin

2016-09-01

In this paper, we have proposed a novel and simple scheme to generate the BPSK optical millimeter wave (MMW) signal with frequency septupling by using an optical phase modulator (PM) and a wavelength selective switch (WSS). In this scheme, the PM is driven by a radio frequency (RF) BPSK signal at the optimized modulation index of 4.89 to assure the 4th and 3rd-order sidebands have equal amplitudes. An wavelength selective switch (WSS) is used to abstract the -4th and +3rd-order sidebands from the spectrum generated by RF BPSK signal modulating the lightwave to form the BPSK optical MMW signal with frequency septupling the driving RF signal. In these two tones, only the +3rd-order sideband bears the BPSK signal while the -4th-order sideband is unmodulated since the phase information is canceled by the even times multiplication of the phase of BPSK signal. The MMW signal can avoid the pulse walk-off effect and the amplitude fading effect caused by the fiber chromatic dispersion. By adjusting the modulation index to assure the two tones have equal amplitude, the generated optical MMW signal has the maximal opto-electrical conversion efficiency and good transmission performance.

Demonstration of a 100-mJ OPO/OPA for future lidar applications and laser-induced damage threshold testing of optical components for MERLIN

NASA Astrophysics Data System (ADS)

Elsen, Florian; Livrozet, Marie; Strotkamp, Michael; Wüppen, Jochen; Jungbluth, Bernd; Kasemann, Raphael; Löhring, Jens; Meissner, Ansgar; Meyer, Rudolf; Hoffmann, Hans-Dieter; Poprawe, Reinhart

2018-02-01

In the field of atmospheric research, lidar is a powerful technology that can measure gas or aerosol concentrations, wind speed, or temperature profiles remotely. To conduct such measurements globally, spaceborne systems are advantageous. Pulse energies in the 100-mJ range are required to achieve highly accurate, longitudinal resolved measurements. Measuring concentrations of specific gases, such as CH4 or CO2, requires output wavelengths in the IR-B, which can be addressed by optical-parametric frequency conversion. An OPO/OPA frequency conversion setup was designed and built as a demonstration module to address the 1.6-μm range. The pump laser is an Nd:YAG-MOPA system, consisting of a stable oscillator and two subsequent Innoslab-based amplifier stages that deliver up to 500 mJ of output pulse energy at 100 Hz repetition frequency. The OPO is inherited from the OPO design for the CH4 lidar instrument on the French-German climate satellite methane remote-sensing lidar mission (MERLIN). To address the 100-mJ regime, the OPO output beam is amplified in a subsequent multistage OPA. With potassium titanyl phosphate as nonlinear medium, the OPO/OPA delivered more than 100 mJ of output energy at 1645 nm from 450 mJ of the pump energy and a pump pulse duration of 30 ns. This corresponds to a quantum conversion efficiency of about 25%. In addition to demonstrating optical performance for future lidar systems, this laser will be part of a laser-induced damage thresholds test facility, which will be used to qualify optical components especially for the MERLIN.

High output power of differently cut Nd:MgO:LiTaO3 CW lasers

NASA Astrophysics Data System (ADS)

Sun, D. H.; Liu, S. D.; Wang, D. Z.; Sang, Y. H.; Kang, X. L.; Liu, H.; Bi, Y.; Yan, B. X.; He, J. L.; Wang, J. Y.

2013-04-01

A high-quality Nd3+ and Mg2+ co-doped LiTaO3 (Nd:MgO:LT) crystal was grown by the Czochralski method. The polarized absorption spectra and fluorescence spectra were studied, and the absorption cross section was calculated by Judd-Ofelt (J-O) theory. The laser performance with different sample cuts of the crystal was investigated for the first time, and it was found that Nd:MgO:LT crystal with different cutting directions (a and c) exhibits different laser properties. By optimizing a partial reflectivity mirror in the laser experimental setting, a high continuous wave output power of 3.58 W was obtained at 1092 and 1076 nm with an optical-to-optical conversion efficiency of 22.78% and slope efficiency of 26.06%. The results indicate that Nd:MgO:LT crystal is a promising candidate for the manufacture of Nd3+ doped periodically poled MgO:LiTaO3 crystal (Nd:PPMgOLT), which should have considerable applications in self-frequency doubling and optical parametric oscillation laser devices.

A Q-switched Ho:YAG laser with double anti-misalignment corner cubes pumped by a diode-pumped Tm:YLF laser

NASA Astrophysics Data System (ADS)

Wang, Y. P.; Dai, T. Y.; Wu, J.; Ju, Y. L.; Yao, B. Q.

2018-06-01

We report the acousto-optically Q-switched Ho:YAG laser with double anti-misalignment corner cubes pumped by a diode-pumped Tm:YLF laser. In the continuous-wave operation of Ho:YAG laser, the maximum s-polarized output power of 3.2 W at 2090.3 nm was obtained under the absorbed pump power of 12.9 W by rotating the fast axis of quarter-wave plate to change the output transmission of laser cavity. The corresponding optical-to-optical conversion efficiency was 24.8% and the slope efficiency was 55.7%. When one of the corner cubes was rotated to 11.8° around vertical direction or 6.7° around horizontal direction, the laser could still operate stably. For the Q-switched operation, the pulse energy of Ho:YAG laser was 9.9 mJ with a pulse width of 53 ns at the repetition rate of 100 Hz, resulting in a peak power of 186.8 kW. The beam quality factor M2 of Ho:YAG laser was 1.3.

Jerusalem artichoke powder: a useful material in producing high-optical-purity l-lactate using an efficient sugar-utilizing thermophilic Bacillus coagulans strain.

PubMed

Wang, Limin; Xue, Zhangwei; Zhao, Bo; Yu, Bo; Xu, Ping; Ma, Yanhe

2013-02-01

Jerusalem artichoke is a low-requirement crop, which does not interfere with food chain, and is a promising carbon source for industrial fermentation. Microbial conversion of such a renewable raw material to useful products, such as lactic acid, is an important objective in industrial biotechnology. In this study, high-optical-purity l-lactate was efficiently produced from the hydrolysates of Jerusalem artichoke powder by a thermophilic bacterium, Bacillus coagulans XZL4. High l-lactate production (134gl(-1)) was obtained using 267gl(-1) Jerusalem artichoke powder (total reducing sugars of 140gl(-1)) and 10gl(-1) of corn steep powder in fed-batch fermentation, with an average productivity of 2.5gl(-1)h(-1) and a yield of 0.96gg(-1) reducing sugars. The final product optical purity is 99%, which meets the requirement of lactic acid polymerization. Our study represents a cost-effective and promising method for polymer-grade l-lactate production using a cheap raw bio-resource. Copyright © 2012 Elsevier Ltd. All rights reserved.

Efficient generation of 509 nm light by sum-frequency mixing between two tapered diode lasers

NASA Astrophysics Data System (ADS)

Tawfieq, Mahmoud; Jensen, Ole Bjarlin; Hansen, Anders Kragh; Sumpf, Bernd; Paschke, Katrin; Andersen, Peter E.

2015-03-01

We demonstrate a concept for visible laser sources based on sum-frequency generation of beam combined tapered diode lasers. In this specific case, a 1.7 W sum-frequency generated green laser at 509 nm is obtained, by frequency adding of 6.17 W from a 978 nm tapered diode laser with 8.06 W from a 1063 nm tapered diode laser, inside a periodically poled MgO doped lithium niobate crystal. This corresponds to an optical to optical conversion efficiency of 12.1%. As an example of potential applications, the generated nearly diffraction-limited green light is used for pumping a Ti:sapphire laser, thus demonstrating good beam quality and power stability. The maximum output powers achieved when pumping the Ti:sapphire laser are 226 mW (CW) and 185 mW (mode-locked) at 1.7 W green pump power. The optical spectrum emitted by the mode-locked Ti:sapphire laser shows a spectral width of about 54 nm (FWHM), indicating less than 20 fs pulse width.

Steric engineering of metal-halide perovskites with tunable optical band gaps

NASA Astrophysics Data System (ADS)

Filip, Marina R.; Eperon, Giles E.; Snaith, Henry J.; Giustino, Feliciano

2014-12-01

Owing to their high energy-conversion efficiency and inexpensive fabrication routes, solar cells based on metal-organic halide perovskites have rapidly gained prominence as a disruptive technology. An attractive feature of perovskite absorbers is the possibility of tailoring their properties by changing the elemental composition through the chemical precursors. In this context, rational in silico design represents a powerful tool for mapping the vast materials landscape and accelerating discovery. Here we show that the optical band gap of metal-halide perovskites, a key design parameter for solar cells, strongly correlates with a simple structural feature, the largest metal-halide-metal bond angle. Using this descriptor we suggest continuous tunability of the optical gap from the mid-infrared to the visible. Precise band gap engineering is achieved by controlling the bond angles through the steric size of the molecular cation. On the basis of these design principles we predict novel low-gap perovskites for optimum photovoltaic efficiency, and we demonstrate the concept of band gap modulation by synthesising and characterising novel mixed-cation perovskites.

Optical determination of Shockley-Read-Hall and interface recombination currents in hybrid perovskites

PubMed Central

Sarritzu, Valerio; Sestu, Nicola; Marongiu, Daniela; Chang, Xueqing; Masi, Sofia; Rizzo, Aurora; Colella, Silvia; Quochi, Francesco; Saba, Michele; Mura, Andrea; Bongiovanni, Giovanni

2017-01-01

Metal-halide perovskite solar cells rival the best inorganic solar cells in power conversion efficiency, providing the outlook for efficient, cheap devices. In order for the technology to mature and approach the ideal Shockley-Queissier efficiency, experimental tools are needed to diagnose what processes limit performances, beyond simply measuring electrical characteristics often affected by parasitic effects and difficult to interpret. Here we study the microscopic origin of recombination currents causing photoconversion losses with an all-optical technique, measuring the electron-hole free energy as a function of the exciting light intensity. Our method allows assessing the ideality factor and breaks down the electron-hole recombination current into bulk defect and interface contributions, providing an estimate of the limit photoconversion efficiency, without any real charge current flowing through the device. We identify Shockley-Read-Hall recombination as the main decay process in insulated perovskite layers and quantify the additional performance degradation due to interface recombination in heterojunctions. PMID:28317883

Study of series-connected polymer tandem solar cells based on a highly efficient donor material of PTB7-Th

NASA Astrophysics Data System (ADS)

Zang, Yue; Gao, Xiumin; Xin, Qing; Lin, Jun; Zhao, Jufeng

2017-06-01

A highly efficient donor polymer, PTB7-Th, combined with acceptor fullerene PC71BM was introduced as the subcell in the series-connected tandem devices to achieve high-performance polymer tandem solar cells. Design of the device architecture was investigated using modeling and simulation methods to identify the optimal structure and to predict performance of the tandem cells. To address the challenge of current matching between the constituent subcells, the effect of active layer thickness, different device structure, and use of ultrathin Ag film were analyzed. It was found that the distribution of optical intensity in the tandem structure can be optimized through the optical spacer effect of interfacial layers and micro-cavity effect derived from the embedded ultrathin Ag film. Our results indicate that the efficient light utilization with appropriate subcells can allow achievement of power conversion efficiency of 12%, which can be 25% higher than that of a single cell of PTB7-Th.

Overview of optical rectennas for solar energy harvesting

NASA Astrophysics Data System (ADS)

Zhu, Zixu; Joshi, Saumil; Pelz, Bradley; Moddel, Garret

2013-09-01

Although the concept of using optical rectenna for harvesting solar energy was first introduced four decades ago, only recently has it invited a surge of interest, with dozens of laboratories around the world working on various aspects of the technology. An optical rectenna couples an ultra-high-speed diode to a submicron antenna so that the incoming radiation received by the antenna is rectified by the diode to produce a DC power output. The result is a technology that can be efficient and inexpensive, requiring only low-cost materials. Conventional classical rectification theory does not apply at optical frequencies, necessitating the application of quantum photon-assisted tunneling theory to describe the device operation. At first glance it would appear that the ultimate conversion efficiency is limited only by the Landsberg limit of 93%, but a more sober analysis that includes limitation due to the coherence of solar radiation leads to a result that coincides with the Trivich-Flinn limit of 44%. Innovative antenna designs are required to achieve high efficiency at frequencies where resistive losses in metal are substantial. The diode most often considered for rectennas make use of electron tunneling through ultra-thin insulators in metal-insulator-metal (MIM) diodes. The most severe constraint is that the impedances of the antenna and diodes must match for efficient power transfer. The consequence is an RC time constant that cannot be achieved with parallel-plate MIM diodes, leading to the need for real innovations in diode structures. Technologies under consideration include sharp-tip and traveling-wave MIM diodes, and graphene geometric diodes. We survey the technologies under consideration.

New preemptive scheduling for OBS networks considering cascaded wavelength conversion

NASA Astrophysics Data System (ADS)

Gao, Xingbo; Bassiouni, Mostafa A.; Li, Guifang

2009-05-01

In this paper we introduce a new preemptive scheduling technique for next generation optical burst-switched networks considering the impact of cascaded wavelength conversions. It has been shown that when optical bursts are transmitted all optically from source to destination, each wavelength conversion performed along the lightpath may cause certain signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough, the receiver would not be able to recover the original data. Accordingly, subject to this practical impediment, we improve a recently proposed fair channel scheduling algorithm to deal with the fairness problem and aim at burst loss reduction simultaneously in optical burst switching. In our scheme, the dynamic priority associated with each burst is based on a constraint threshold and the number of already conducted wavelength conversions among other factors for this burst. When contention occurs, a new arriving superior burst may preempt another scheduled one according to their priorities. Extensive simulation results have shown that the proposed scheme further improves fairness and achieves burst loss reduction as well.

NASA Tech Briefs, October 2007

NASA Technical Reports Server (NTRS)

2007-01-01

Topics covered include; Wirelessly Interrogated Position or Displacement Sensors; Ka-Band Radar Terminal Descent Sensor; Metal/Metal Oxide Differential Electrode pH Sensors; Improved Sensing Coils for SQUIDs; Inductive Linear-Position Sensor/Limit-Sensor Units; Hilbert-Curve Fractal Antenna With Radiation- Pattern Diversity; Single-Camera Panoramic-Imaging Systems; Interface Electronic Circuitry for an Electronic Tongue; Inexpensive Clock for Displaying Planetary or Sidereal Time; Efficient Switching Arrangement for (N + 1)/N Redundancy; Lightweight Reflectarray Antenna for 7.115 and 32 GHz; Opto-Electronic Oscillator Using Suppressed Phase Modulation; Alternative Controller for a Fiber-Optic Switch; Strong, Lightweight, Porous Materials; Nanowicks; Lightweight Thermal Protection System for Atmospheric Entry; Rapid and Quiet Drill; Hydrogen Peroxide Concentrator; MMIC Amplifiers for 90 to 130 GHz; Robot Would Climb Steep Terrain; Measuring Dynamic Transfer Functions of Cavitating Pumps; Advanced Resistive Exercise Device; Rapid Engineering of Three-Dimensional, Multicellular Tissues With Polymeric Scaffolds; Resonant Tunneling Spin Pump; Enhancing Spin Filters by Use of Bulk Inversion Asymmetry; Optical Magnetometer Incorporating Photonic Crystals; WGM-Resonator/Tapered-Waveguide White-Light Sensor Optics; Raman-Suppressing Coupling for Optical Parametric Oscillator; CO2-Reduction Primary Cell for Use on Venus; Cold Atom Source Containing Multiple Magneto- Optical Traps; POD Model Reconstruction for Gray-Box Fault Detection; System for Estimating Horizontal Velocity During Descent; Software Framework for Peer Data-Management Services; Autogen Version 2.0; Tracking-Data-Conversion Tool; NASA Enterprise Visual Analysis; Advanced Reference Counting Pointers for Better Performance; C Namelist Facility; and Efficient Mosaicking of Spitzer Space Telescope Images.

Non-contact fiber-optical trapping of motile bacteria: dynamics observation and energy estimation

PubMed Central

Xin, Hongbao; Liu, Qingyuan; Li, Baojun

2014-01-01

The dynamics and energy conversion of bacteria are strongly associated with bacterial activities, such as survival, spreading of bacterial diseases and their pathogenesis. Although different discoveries have been reported on trapped bacteria (i.e. immobilized bacteria), the investigation on the dynamics and energy conversion of motile bacteria in the process of trapping is highly desirable. Here, we report a non-contact optical trapping of motile bacteria using a modified tapered optical fiber. Using Escherichia coli as an example, both single and multiple motile bacteria have been trapped and manipulated in a non-contact manner. Bacterial dynamics has been observed and bacterial energy has been estimated in the trapping process. This non-contact optical trapping provides a new opportunity for better understanding the bacterial dynamics and energy conversion at the single cell level. PMID:25300713

Heterogeneously Nd3+ doped single nanoparticles for NIR-induced heat conversion, luminescence, and thermometry.

PubMed

Marciniak, Lukasz; Pilch, Aleksandra; Arabasz, Sebastian; Jin, Dayong; Bednarkiewicz, Artur

2017-06-22

The current frontier in nanomaterials engineering is to intentionally design and fabricate heterogeneous nanoparticles with desirable morphology and composition, and to integrate multiple functionalities through highly controlled epitaxial growth. Here we show that heterogeneous doping of Nd 3+ ions following a core-shell design already allows three optical functions, namely efficient (η > 72%) light-to-heat conversion, bright NIR emission, and sensitive (S R > 0.1% K -1 ) localized temperature quantification, to be built within a single ca. 25 nm nanoparticle. Importantly, all these optical functions operate within the transparent biological window of the NIR spectral region (λ exc ∼ 800 nm, λ emi ∼ 860 nm), in which light scattering and absorption by tissues and water are minimal. We find NaNdF 4 as a core is efficient in absorbing and converting 808 nm light to heat, while NaYF 4 :1%Nd 3+ as a shell is a temperature sensor based on the ratio-metric luminescence reading but an intermediate inert spacer shell, e.g. NaYF 4 , is necessary to insulate the heat convertor and thermometer by preventing the possible Nd-Nd energy relaxation. Moreover, we notice that while temperature sensitivity and luminescence intensity are optically stable, increased excitation intensity to generate heat above room temperature may saturate the sensing capacity of temperature feedback. We therefore propose a dual beam photoexcitation scheme as a solution for possible light-induced hyperthermia treatment.

Efficiency enhancement of silicon nanowire solar cells by using UV/Ozone treatments and micro-grid electrodes

NASA Astrophysics Data System (ADS)

Chen, Junyi; Subramani, Thiyagu; Sun, Yonglie; Jevasuwan, Wipakorn; Fukata, Naoki

2018-05-01

Silicon nanowire solar cells were fabricated by metal catalyzed electroless etching (MCEE) followed by thermal chemical vapor deposition (CVD). In this study, we investigated two effects, a UV/ozone treatment and the use of a micro-grid electrodes, to enhance light absorption and reduce the optic losses in the solar cell device. The UV/ozone treatment successfully improved the conversion efficiency. The micro-grid electrodes were then applied in solar cell devices subjected to a back surface field (BSF) treatment and rapid thermal annealing (RTA). These effects improved the conversion efficiency from 9.4% to 10.9%. Moreover, to reduce surface recombination and improve the continuity of front electrodes, we optimized the etching time of the MCEE process, giving a high efficiency of 12.3%.

Design and implementation of novel nonlinear processes in bulk and waveguide periodic structures

NASA Astrophysics Data System (ADS)

Kajal, Meenu

The telecommunication networks are facing increasing demand to implement all-optical network infrastructure for enabling the wide deployment of new triple play high-speed services (e.g. IPTV, Video On Demand, Voice over IP). One of the challenges with such video broadcasting applications is that these are much more distributed and multi-point in nature unlike the traditional point-to-point communication networks. Currently deployed high-speed electronic components in the optical networks are incapable of handling the unprecedented bandwidth demand for real-time multimedia based broadcasting. The solution essentially lies in increasing the transparency of networks i.e. by replacing high speed signal processing electronics with all-optical signal processors capable of performing signal manipulations such as wavelength switching, time and wavelength division multiplexing, optical pulse compression etc. all in optical domain. This thesis aims at providing an all-optical solution for broadband wavelength conversion and tunable broadcasting, a crucial optical network component, based on quasi-phase-matched wave mixing in nonlinear materials. The quasi phase matching (QPM) technique allows phase matching in long crystal lengths by employing domain-inverted gratings to periodically reverse the sign of nonlinearity, known as periodic poling. This results into new frequency components with high conversion efficiency and has been successfully implemented towards various processes such as second harmonic generation (SHG), sum- and difference- frequency generation (SFG and DFG). Conventionally, the optical networks has an operation window of ˜35 nm centered at 1.55 mum, known as C-band. The wavelength conversion of a signal channel in C-band to an output channel also in the C-band has been demonstrated in periodically poled lithium niobate (PPLN) waveguides via the process of difference frequency mixing, cascaded SHG/DFG and cascaded SFG/DFG. While a DFG process utilized a pump wavelength in 775nm regime, it suffered from low efficiency due to mode mismatch between the pump and the signal wavelengths; whereas the technique based on cSHG/DFG or cSFG/DFG eliminated the mode mismatch problem with pump(s) lying in the 1.55 mum wavelength regime. In this thesis, for the first time a flattened bandwidth of cSFG/DFG have been experimentally realized by slight detuning of the pump wavelengths from their phase matching condition. Moreover, employing two closely spaced pumps in a cSFG/DFG process in a PPLN waveguide, a signal has been broadcast to three idlers in C-band. Although a uniform period PPLN grating increases efficiency by the use of highest nonlinearity tensor coefficient via QPM, it suffers from the limitation of a narrow bandwidth of frequency doubling. The narrow bandwidth restricts the choice of pump wavelengths in a cascaded conversion process and consequently the converted signal wavelength is also fixed for a given signal wavelength. Enhancing the frequency doubling bandwidth is necessary for mainly two reasons: firstly, to achieve the tunability of wavelength conversion of a signal to any channel in the communication band; and secondly, to broadcast a signal to several channels simultaneously by employing multiple pump lasers within its broad bandwidth. The first engineered PPLN device proposed and demonstrated in this thesis for broadband wavelength conversion has an aperiodic domain in the center of an otherwise periodic grating. This phase-shifted or aperiodic (a-) PPLN has a dual-peak SH response with an increase in bandwidth compared to a uniform PPLN. It has also been shown that using temperature tuning, the phase matching conditions of the aPPLN can be varied and its SH bandwidth can be further enhanced. The triple-idler broadcasting is shown and for the first time, the idlers are tuned across 40 channels in C-band with flexible location and mutual spacing in the WDM grid assisted with pump detuning and temperature tuning. Although the temperature-tuning scheme solves the problem of narrow SH bandwidth and tunability of conversion, the slow speed of temperature change makes it inadequate for ultra-fast WDM applications. Therefore, a temperature-independent broadband device has been demonstrated for the first time in this dissertation, using a step-chirped grating (SCG), which has an inherent 30-nm SH bandwidth overlapping the C-band. This device obviates the need of temperature tuning and leads to tunable wavelength conversion and flexible broadcasting. Employing a single tuned pump wavelength in the SC-PPLN, conversion of a signal in C-band to tunable dual idlers via cSHG/DFG process is demonstrated for the first time. Also by taking advantage of the broad SH-SF bandwidth, for the first time, agile broadcasting of a signal to seven idlers spanning across C-band with variable position in the grid is realized based on cSHG/DFG and cSFG/DFG processes. By tuning the two pump wavelengths over less than 6 nm, broadcasting is achieved across ˜70 WDM channels within the 50 GHz spacing WDM grid. (Abstract shortened by UMI.).

Monolithically integrated solid state laser and waveguide using spin-on glass

DOEpatents

Ashby, C.I.H.; Hohimer, J.P.; Neal, D.R.; Vawter, G.A.

1995-10-31

A monolithically integrated photonic circuit is disclosed combining a semiconductor source of excitation light with an optically active waveguide formed on the substrate. The optically active waveguide is preferably formed of a spin-on glass to which are added optically active materials which can enable lasing action, optical amplification, optical loss, or frequency conversion in the waveguide, depending upon the added material. 4 figs.

2 W quasi-white-light based on idler-resonant optical parametric oscillation cascading sum-frequency generation with PPSLT

NASA Astrophysics Data System (ADS)

Zhao, L. N.; Liu, J.; Yuan, Y.; Hu, X. P.; Zhao, G.; Gao, Z. D.; Zhu, S. N.

2012-03-01

We present a high power red-green-blue (RGB) laser light source based on cascaded quasi-phasematched wavelength conversions in a single stoichiometric lithium tantalate. The superiority of the experimental setup is: the facula of the incident beam is elliptical to increase interaction volume, and the cavity was an idler resonant configuration for realizing more efficient red and blue light output. An average power of 2 W of quasi-white-light was obtained by proper combination of the RGB three colors. The conversion efficiency for the power of the quasi-white-light over pump power reached 36%. This efficiency and powerful RGB laser light source has potential applications in laser-based projection display et al.

Efficient near-infrared up-conversion photoluminescence in carbon nanotubes

PubMed Central

Akizuki, Naoto; Aota, Shun; Mouri, Shinichiro; Matsuda, Kazunari; Miyauchi, Yuhei

2015-01-01

Photoluminescence phenomena normally obey Stokes' law of luminescence according to which the emitted photon energy is typically lower than its excitation counterparts. Here we show that carbon nanotubes break this rule under one-photon excitation conditions. We found that the carbon nanotubes exhibit efficient near-infrared photoluminescence upon photoexcitation even at an energy lying >100–200 meV below that of the emission at room temperature. This apparently anomalous phenomenon is attributed to efficient one-phonon-assisted up-conversion processes resulting from unique excited-state dynamics emerging in an individual carbon nanotube with accidentally or intentionally embedded localized states. These findings may open new doors for energy harvesting, optoelectronics and deep-tissue photoluminescence imaging in the near-infrared optical range. PMID:26568250

Synergistic plasmonic and photonic crystal light-trapping: architectures for optical up-conversion in thin-film solar cells.

PubMed

Le, Khai Q; John, Sajeev

2014-01-13

We demonstrate, numerically, that with a 60 nanometer layer of optical up-conversion material, embedded with plasmonic core-shell nano-rings and placed below a sub-micron silicon conical-pore photonic crystal it is possible to absorb sunlight well above the Lambertian limit in the 300-1100 nm range. With as little as 500 nm, equivalent bulk thickness of silicon, the maximum achievable photo-current density (MAPD) is about 36 mA/cm2, using above-bandgap sunlight. This MAPD increases to about 38 mA/cm2 for one micron of silicon. Our architecture also provides solar intensity enhancement by a factor of at least 1400 at the sub-bandgap wavelength of 1500 nm, due to plasmonic and photonic crystal resonances, enabling a further boost of photo-current density from up-conversion of sub-bandgap sunlight. With an external solar concentrator, providing 100 suns, light intensities sufficient for significant nonlinear up-conversion can be realized. Two-photon absorption of sub-bandgap sunlight is further enhanced by the large electromagnetic density of states in the photonic crystal at the re-emission wavelength near 750 nm. It is suggested that this synergy of plasmonic and photonic crystal resonances can lead to unprecedented power conversion efficiency in ultra-thin-film silicon solar cells.

Integrated optical modulator for signal up-conversion over radio-on-fiber link.

PubMed

Kim, Woo-Kyung; Kwon, Soon-Woo; Jeong, Woo-Jin; Son, Geun-Sik; Lee, Kwang-Hyun; Choi, Woo-Young; Yang, Woo-Seok; Lee, Hyung-Man; Lee, Han-Young

2009-02-16

An integrated optical modulator, which consists of a dual-sideband suppressed carrier (DSB-SC) modulator cascaded with a single-sideband (SSB) modulator, is proposed for signal up-conversion over Radio-on-Fiber. Utilizing a single-drive domain inverted structure in both modulators, balanced modulations were obtained without complicated radio frequency (RF) driving circuits and delicate RF phase adjustments. Intermediate frequency (IF) band signal was up-conversed to 60GHz band by using the fabricated device and was transmitted over optical fiber. Experiment results show that the proposed device enables millimeter wave generation and signal transmission without any power penalty caused by chromatic dispersion.

Conversion of the optical orbital angular momentum in a plasmon-assisted second-harmonic generation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yongmei; Wei, Dunzhao; Zhu, Yunzhi

We experimentally demonstrate the plasmon-assisted second-harmonic generation of an optical orbital angular momentum (OAM) beam. Because of the shape resonance, the plasmons in a periodic array of rectangular metal holes greatly enhance the nonlinear optical conversion of an OAM state. The OAM conservation (i.e., 2l{sub 1} = l{sub 2} with l{sub 1} and l{sub 2} being the OAM numbers of the fundamental and second-harmonic waves, respectively) holds well under our experimental configuration. Our results provide a potential way to realize nonlinear optical manipulation of an OAM mode in a nano-photonic device.

Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites

PubMed Central

Yang, Jianfeng; Wen, Xiaoming; Xia, Hongze; Sheng, Rui; Ma, Qingshan; Kim, Jincheol; Tapping, Patrick; Harada, Takaaki; Kee, Tak W.; Huang, Fuzhi; Cheng, Yi-Bing; Green, Martin; Ho-Baillie, Anita; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Conibeer, Gavin

2017-01-01

The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I−/Br−) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials. PMID:28106061

Diode-side-pumped 131 W, 1319 nm single-wavelength cw Nd:YAG laser.

PubMed

Haiyong, Zhu; Ge, Zhang; Chenghui, Huang; Yong, Wei; Lingxiong, Huang; Jing, Chen; Weidong, Chen; Zhenqiang, Chen

2007-01-20

A diode-side-pumped high-power 1319 nm single-wavelength Nd:YAG continuous wave (cw) laser is described. Through reasonable coating design of the cavity mirrors, the 1064 nm strongest line as well as the 1338 nm one have been successfully suppressed. The laser output powers corresponding to four groups of different output couplers operating at 1319 nm single wavelength have been compared. The output coupler with the transmission T=5.3% has the highest output power, and a 131 W cw output power was achieved at the pumping power of 555 W. The optical-optical conversion efficiency is 23.6%, and the slope efficiency is 46%. The output power is higher than the total output power of the dual-wavelength laser operating at 1319 nm and 1338 nm in the experiment.

High-power narrow-linewidth quasi-CW diode-pumped TEM00 1064 nm Nd:YAG ring laser.

PubMed

Liu, Yuan; Wang, Bao-shan; Xie, Shi-yong; Bo, Yong; Wang, Peng-yuan; Zuo, Jun-wei; Xu, Yi-ting; Xu, Jia-lin; Peng, Qin-jun; Cui, Da-fu; Xu, Zu-yan

2012-04-01

We demonstrated a high average power, narrow-linewidth, quasi-CW diode-pumped Nd:YAG 1064 nm laser with near-diffraction-limited beam quality. A symmetrical three-mirror ring cavity with unidirectional operation elements and an etalon was employed to realize the narrow-linewidth laser output. Two highly efficient laser modules and a 90° quartz rotator for birefringence compensation were used for the high output power. The maximum average output power of 62.5 W with the beam quality factor M(2) of 1.15 was achieved under a pump power of 216 W at a repetition rate of 500 Hz, corresponding to the optical-to-optical conversion efficiency of 28.9%. The linewidth of the laser at the maximum output power was measured to be less than 0.2 GHz.

All-solid-state continuous-wave frequency doubling Nd:LuVO4/LBO laser with 2.17 W output power at 543 nm

NASA Astrophysics Data System (ADS)

Li, B.; Zhao, L.; Zhang, Y. B.; Zheng, Q.; Zhao, Y.; Yao, Y.

2013-03-01

Efficient and compact green-yellow laser output at 543 nm is generated by intracavity frequency doubling of a CW diode-pumped Nd:LuVO4 laser at 1086 nm under the condition of suppressing the higher gain transition near 1064 nm. With 16 W of diode pump power and the frequency-doubling crystal LBO, as high as 2.17 W of CW output power at 543 nm is achieved, corresponding to an optical-to-optical conversion efficiency of 13.6% and the output power stability over 8 hours is better than 2.86%. To the best of our knowledge, this is the highest watt-level laser at 543 nm generated by intracavity frequency doubling of a diode pumped Nd:LuVO4 laser at 1086 nm.

High beam quality of a Q-switched 2-µm Tm,Ho:LuVO4 laser

NASA Astrophysics Data System (ADS)

Wang, Wei; Yang, Xining; Shen, Yingjie; Li, Linjun; Zhou, Long; Yang, Yuqiang; Bai, Yunfeng; Xie, Wenqiang; Ye, Guangchao; Yu, Xiaoyang

2018-05-01

A diode-end-pumped 2.05-µm Q-switched Tm,Ho:LuVO4 laser is reported in this paper. The cryogenic Tm3+ (5.0 at.%),Ho3+ (0.5 at.%):LuVO4 crystal was pumped by an 800-nm laser diode. At a pulse repetition frequency of 10 kHz, the maximum average output power of 3.77 W was achieved at 77 K when an incident pump power of 14.7 W was used. The slope efficiency and optical-optical conversion efficiency were 28.3 and 25.6%, respectively. The maximum per pulse energy was 2.54 mJ for a pulse duration of 69.9 ns. The beam quality factor Mx 2 was approximately 1.17 and My 2 was approximately 1.01 for the Tm,Ho:LuVO4 laser.

Optical and Photovoltaic Properties of Thieno[3,2-b]thiophene-Based Push-Pull Organic Dyes with Different Anchoring Groups for Dye-Sensitized Solar Cells.

PubMed

Fernandes, Sara S M; Castro, M Cidália R; Pereira, Ana Isabel; Mendes, Adélio; Serpa, Carlos; Pina, João; Justino, Licínia L G; Burrows, Hugh D; Raposo, M Manuela M

2017-12-31

The effect of anchoring groups on the optical and electrochemical properties of triphenylamine-thienothiophenes, and on the photovoltaic performance of DSSCs photosensitized with the prepared dyes, was studied using newly synthesized compounds with cyanoacetic acid or rhodanine-3-acetic acid groups. Precursor aldehydes were synthesized through Suzuki cross-coupling, whereas Knoevenagel condensation of these with 2-cyanoacetic acid or rhodanine-3-acetic acid afforded the final push-pull dyes. A comprehensive photophysical study was performed in solution and in the solid state. The femtosecond time-resolved transient absorption spectra for the synthesized dyes were obtained following photoexcitation in solution and for the dyes adsorbed to TiO 2 mesoporous films. Information on conformation, electronic structure, and electron distribution was obtained by density functional theory (DFT) and time-dependent DFT calculations. Triphenylamine-thienothiophene functionalized with a cyanoacetic acid anchoring group displayed the highest conversion efficiency (3.68%) as the dye sensitizer in nanocrystalline TiO 2 solar cells. Coadsorption studies were performed for this dye with the ruthenium-based N719 dye, and they showed dye power conversion efficiencies enhanced by 20-64%. The best cell performance obtained with the coadsorbed N719 and cyanoacetic dye showed an efficiency of 6.05%.

Limitations of Cs3Bi2I9 as lead-free photovoltaic absorber materials.

PubMed

Ghosh, Biplab; Wu, Bo; Mulmudi, Hemant Kumar; Guet, Claude; Weber, Klaus; Sum, Tze Chien; Mhaisalkar, Subodh G; Mathews, Nripan

2018-01-17

Lead (Pb) halide perovskites have attracted tremendous attention in recent years due to their rich optoelectronic properties, which have resulted in more than 22% power conversion efficient photovoltaics. Nevertheless, Pb-metal toxicity remains a huge hurdle for extensive applications of these compounds. Thus, alternative compounds with similar optoelectronic properties need to be developed. Bismuth possesses similar electronic structure as that of lead with the presence of ns2 electrons that exhibit rich structural variety as well as interesting optical and electronic properties. Herein, we critically assess Cs3Bi2I9 as a candidate for thin-film solar cell absorber. Despite a reasonable optical bandgap (~2eV) and absorption coefficient, the power conversion efficiency of the Cs3Bi2I9 mesoscopic solar cells was found to be severely lacking, limited by poor photocurrent density. The efficiency of the Cs3Bi2I9 solar cell can be slightly improved by changing the stoichiometry of the precursor solutions. We have investigated the possible reasons behind the poor performance of Cs3Bi2I9 by transient absorption and luminescence spectroscopy. Comparison between thin-films and single crystals highlights the presence of intrinsic defects in thin-films which act as nonradiative recombination centers.

Optical and Photovoltaic Properties of Thieno[3,2-b]thiophene-Based Push–Pull Organic Dyes with Different Anchoring Groups for Dye-Sensitized Solar Cells

PubMed Central

2017-01-01

The effect of anchoring groups on the optical and electrochemical properties of triphenylamine-thienothiophenes, and on the photovoltaic performance of DSSCs photosensitized with the prepared dyes, was studied using newly synthesized compounds with cyanoacetic acid or rhodanine-3-acetic acid groups. Precursor aldehydes were synthesized through Suzuki cross-coupling, whereas Knoevenagel condensation of these with 2-cyanoacetic acid or rhodanine-3-acetic acid afforded the final push–pull dyes. A comprehensive photophysical study was performed in solution and in the solid state. The femtosecond time-resolved transient absorption spectra for the synthesized dyes were obtained following photoexcitation in solution and for the dyes adsorbed to TiO2 mesoporous films. Information on conformation, electronic structure, and electron distribution was obtained by density functional theory (DFT) and time-dependent DFT calculations. Triphenylamine–thienothiophene functionalized with a cyanoacetic acid anchoring group displayed the highest conversion efficiency (3.68%) as the dye sensitizer in nanocrystalline TiO2 solar cells. Coadsorption studies were performed for this dye with the ruthenium-based N719 dye, and they showed dye power conversion efficiencies enhanced by 20–64%. The best cell performance obtained with the coadsorbed N719 and cyanoacetic dye showed an efficiency of 6.05%. PMID:29302638

Sugar apple-shaped TiO2 hierarchical spheres for highly efficient dye-sensitized solar cells

NASA Astrophysics Data System (ADS)

Lei, Bing-Xin; Zeng, Li-Li; Zhang, Ping; Qiao, He-Kang; Sun, Zhen-Fan

2014-05-01

The sugar apple-shaped TiO2 hierarchical spheres are prepared by a facile hydrothermal method using polyethylene glycol 600 as stabilized reagent, (NH4)2TiF6 and urea as starting materials at 180 °C. The characterizations show that the TiO2 hierarchical sphere has well-defined pyramid-shaped crystal facets. The as-prepared TiO2 hierarchical spheres are crystalline of the anatase phase, with a diameter of about 2-4 μm and a surface area of 36.846 m2 g-1. The optical investigation evidences that the sugar apple-shaped TiO2 hierarchical sphere film exhibits a prominent light scattering effect at a wavelength range of 600-800 nm due to the unique hierarchical morphology. Furthermore, the sugar apple-shaped TiO2 hierarchical spheres are deposited as the scattering layer to balance the dye adsorption and light scattering effect in DSSCs and a 7.20% solar energy conversion efficiency is demonstrated, indicating an improvement compared with the P25 cell (6.68%). Based on the optical and electrochemical investigations, the high conversion efficiency is mainly due to the effective suppression of the back reaction of the injected electron with the I3- in the electrolyte and excellent light scattering ability.

Photovoltaic Performance of Inverted Polymer Solar Cells Using Hybrid Carbon Quantum Dots and Absorption Polymer Materials

NASA Astrophysics Data System (ADS)

Lim, Hwain; Lee, Kyu Seung; Liu, Yang; Kim, Hak Yong; Son, Dong Ick

2018-05-01

We report the synthesis and characterization of the carbon quantum dots (C-dots) easily obtained from citric acid and ethanediamine, and also investigated structural, optical and electrical properties. The C-dots have extraordinary optical and electrical features such as absorption of ultraviolet range and effective interface for charge separation and transport in active layer, which make them attractive materials for applications in photovoltaic devices (PV). The C-dots play important roles in charge extraction in the PV structures, they can be synthesized by a simple method and used to insert in active layer of polymer solar cells. In this study, we demonstrate that improve charge transport properties of inverted polymer solar cells (iPSCs) with C-dots and structural, optical and electrical properties of C-dots. As a result, iPSCs with C-dots showed enhancement of more than 30% compared with that of the contrast device in power conversion efficiency.

Optical circulation in a multimode optomechanical resonator.

PubMed

Ruesink, Freek; Mathew, John P; Miri, Mohammad-Ali; Alù, Andrea; Verhagen, Ewold

2018-05-04

Breaking the symmetry of electromagnetic wave propagation enables important technological functionality. In particular, circulators are nonreciprocal components that can route photons directionally in classical or quantum photonic circuits and offer prospects for fundamental research on electromagnetic transport. Developing highly efficient circulators thus presents an important challenge, especially to realise compact reconfigurable implementations that do not rely on magnetic fields to break reciprocity. We demonstrate optical circulation utilising radiation pressure interactions in an on-chip multimode optomechanical system. Mechanically mediated optical mode conversion in a silica microtoroid provides a synthetic gauge bias for light, enabling four-port circulation that exploits tailored interference between appropriate light paths. We identify two sideband conditions under which ideal circulation is approached. This allows to experimentally demonstrate ~10 dB isolation and <3 dB insertion loss in all relevant channels. We show the possibility of actively controlling the circulator properties, enabling ideal opportunities for reconfigurable integrated nanophotonic circuits.

Time-reversal symmetry breaking with acoustic pumping of nanophotonic circuits

NASA Astrophysics Data System (ADS)

Sohn, Donggyu B.; Kim, Seunghwi; Bahl, Gaurav

2018-02-01

Achieving non-reciprocal light propagation via stimuli that break time-reversal symmetry, without magneto-optics, remains a major challenge for integrated nanophotonic devices. Recently, optomechanical microsystems in which light and vibrational modes are coupled through ponderomotive forces have demonstrated strong non-reciprocal effects through a variety of techniques, but always using optical pumping. None of these approaches has demonstrated bandwidth exceeding that of the mechanical system, and all of them require optical power; these are both fundamental and practical issues. Here, we resolve both challenges by breaking time-reversal symmetry using a two-dimensional acoustic pump that simultaneously provides a non-zero overlap integral for light-sound interaction and also satisfies the necessary phase-matching. We use this technique to produce a non-reciprocal modulator (a frequency shifting isolator) by means of indirect interband scattering. We demonstrate mode conversion asymmetry up to 15 dB and efficiency as high as 17% over a bandwidth exceeding 1 GHz.

Guided-wave phase-matched second-harmonic generation in KTiOPO4 waveguide produced by swift heavy-ion irradiation

NASA Astrophysics Data System (ADS)

Cheng, Yazhou; Jia, Yuechen; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

2014-11-01

We report on the guided-wave second-harmonic generation in a KTiOPO4 nonlinear optical waveguide fabricated by a 17 MeV O5+ ion irradiation at a fluence of 1.5×1015 ions/cm2. The waveguide guides light along both TE and TM polarizations, which is suitable for phase-matching frequency doubling. Second harmonics of green light at a wavelength of 532 nm have been generated through the KTiOPO4 waveguide platform under an optical pump of fundamental wave at 1064 nm in both continuous-wave and pulsed regimes, reaching optical conversion efficiencies of 5.36%/W and 11.5%, respectively. The propagation losses have been determined to be ˜3.1 and ˜5.7 dB/cm for the TE and TM polarizations at a wavelength of 632.8 nm, respectively.

A novel method for retinal optic disc detection using bat meta-heuristic algorithm.

PubMed

Abdullah, Ahmad S; Özok, Yasa Ekşioğlu; Rahebi, Javad

2018-05-09

Normally, the optic disc detection of retinal images is useful during the treatment of glaucoma and diabetic retinopathy. In this paper, the novel preprocessing of a retinal image with a bat algorithm (BA) optimization is proposed to detect the optic disc of the retinal image. As the optic disk is a bright area and the vessels that emerge from it are dark, these facts lead to the selected segments being regions with a great diversity of intensity, which does not usually happen in pathological regions. First, in the preprocessing stage, the image is fully converted into a gray image using a gray scale conversion, and then morphological operations are implemented in order to remove dark elements such as blood vessels, from the images. In the next stage, a bat algorithm (BA) is used to find the optimum threshold value for the optic disc location. In order to improve the accuracy and to obtain the best result for the segmented optic disc, the ellipse fitting approach was used in the last stage to enhance and smooth the segmented optic disc boundary region. The ellipse fitting is carried out using the least square distance approach. The efficiency of the proposed method was tested on six publicly available datasets, MESSIDOR, DRIVE, DIARETDB1, DIARETDB0, STARE, and DRIONS-DB. The optic disc segmentation average overlaps and accuracy was in the range of 78.5-88.2% and 96.6-99.91% in these six databases. The optic disk of the retinal images was segmented in less than 2.1 s per image. The use of the proposed method improved the optic disc segmentation results for healthy and pathological retinal images in a low computation time. Graphical abstract ᅟ.

Multicasting based optical inverse multiplexing in elastic optical network.

PubMed

Guo, Bingli; Xu, Yingying; Zhu, Paikun; Zhong, Yucheng; Chen, Yuanxiang; Li, Juhao; Chen, Zhangyuan; He, Yongqi

2014-06-16

Optical multicasting based inverse multiplexing (IM) is introduced in spectrum allocation of elastic optical network to resolve the spectrum fragmentation problem, where superchannels could be split and fit into several discrete spectrum blocks in the intermediate node. We experimentally demonstrate it with a 1-to-7 optical superchannel multicasting module and selecting/coupling components. Also, simulation results show that, comparing with several emerging spectrum defragmentation solutions (e.g., spectrum conversion, split spectrum), IM could reduce blocking performance significantly but without adding too much system complexity as split spectrum. On the other hand, service fairness for traffic with different granularity of these schemes is investigated for the first time and it shows that IM performs better than spectrum conversion and almost as well as split spectrum, especially for smaller size traffic under light traffic intensity.

n-Type silicon photoelectrochemistry in methanol: Design of a 10.1% efficient semiconductor/liquid junction solar cell

PubMed Central

Gronet, Chris M.; Lewis, Nathan S.; Cogan, George; Gibbons, James

1983-01-01

n-Type Si electrodes in MeOH solvent with 0.2 M (1-hydroxyethyl)ferrocene, 0.5 mM (1-hydroxyethyl)ferricenium, and 1.0 M LiClO4 exhibit air mass 2 conversion efficiencies of 10.1% for optical energy into electricity. We observe open-circuit voltages of 0.53 V and short-circuit quantum efficiencies for electron flow of nearly unity. The fill factor of the cell does not decline significantly with increases in light intensity, indicating substantial reduction in efficiency losses in MeOH solvent compared to previous nonaqueous n-Si systems. Matte etch texturing of the Si surface decreases surface reflectivity and increases photocurrent by 50% compared to shiny, polished Si samples. The high values of the open-circuit voltage observed are consistent with the presence of a thin oxide layer, as in a Schottky metal-insulator-semiconductor device, which yields decreased surface recombination and increased values of open-circuit voltage and short-circuit current. The n-Si system was shown to provide sustained photocurrent at air mass 2 levels (20 mA/cm2) for charge through the interface of >2,000 C/cm2. The n-Si/MeOH system represents a liquid junction cell that has exceeded the 10% barrier for conversion of optical energy into electricity. PMID:16593280

High diffraction efficiency of three-layer diffractive optics designed for wide temperature range and large incident angle.

PubMed

Mao, Shan; Cui, Qingfeng; Piao, Mingxu; Zhao, Lidong

2016-05-01

A mathematical model of diffraction efficiency and polychromatic integral diffraction efficiency affected by environment temperature change and incident angle for three-layer diffractive optics with different dispersion materials is put forward, and its effects are analyzed. Taking optical materials N-FK5 and N-SF1 as the substrates of multilayer diffractive optics, the effect on diffraction efficiency and polychromatic integral diffraction efficiency with intermediate materials POLYCARB is analyzed with environment temperature change as well as incident angle. Therefore, three-layer diffractive optics can be applied in more wide environmental temperature ranges and larger incident angles for refractive-diffractive hybrid optical systems, which can obtain better image quality. Analysis results can be used to guide the hybrid imaging optical system design for optical engineers.

Efficient nonlinear metasurface based on nonplanar plasmonic nanocavities

DOE PAGES

Wang, Feng; Martinson, Alex B. F.; Harutyunyan, Hayk

2017-04-03

Since their discovery in the 1960s, nonlinear optical effects have revolutionized optical technologies and laser industry. Development of efficient nanoscale nonlinear sources will pave the way for new applications in photonic circuitry, quantum optics and biosensing. However, nonlinear signal generation at dimensions smaller than the wavelength of light brings new challenges. The fundamental difficulty of designing an efficient nonlinear source is that some of the contributing factors involved in nonlinear wave-mixing at the nanoscale are often hard to satisfy simultaneously. Here, we overcome these limitations by developing a new type of nonplanar plasmonic metasurfaces, which can greatly enhance the secondmore » harmonic generation (SHG) at visible frequencies and achieve conversion efficiency of ~6 × 10 -5 at a peak pump intensity of ~0.5 GW/cm 2. This is 4-5 orders of magnitude larger than the efficiencies observed for nonlinear thin films and doubly resonant plasmonic antennas. The proposed metasurface consists of an array of metal-dielectric-metal (MDM) nanocavities formed by conformally cross-linked nanowires separated by an ultrathin nonlinear material layer. The nonplanar MDM geometry minimizes the destructive interference of nonlinear emission into the far-field, provides strongly enhanced independently tunable resonances both for fundamental and harmonic frequencies, a good mutual overlap of the modes and a strong interaction with the nonlinear spacer. Lastly, our findings enable the development of efficient nanoscale single photon sources, integrated frequency converters, and other nonlinear devices.« less

Novel tunable dynamic tweezers using dark-bright soliton collision control in an optical add/drop filter.

PubMed

Teeka, Chat; Jalil, Muhammad Arif; Yupapin, Preecha P; Ali, Jalil

2010-12-01

We propose a novel system of the dynamic optical tweezers generated by a dark soliton in the fiber optic loop. A dark soliton known as an optical tweezer is amplified and tuned within the microring resonator system. The required tunable tweezers with different widths and powers can be controlled. The analysis of dark-bright soliton conversion using a dark soliton pulse propagating within a microring resonator system is analyzed. The dynamic behaviors of soliton conversion in add/drop filter is also analyzed. The control dark soliton is input into the system via the add port of the add/drop filter. The dynamic behavior of the dark-bright soliton conversion is observed. The required stable signal is obtained via a drop and throughput ports of the add/drop filter with some suitable parameters. In application, the trapped light/atom and transportation can be realized by using the proposed system.

Imaged Document Optical Correlation and Conversion System (IDOCCS)

NASA Astrophysics Data System (ADS)

Stalcup, Bruce W.; Dennis, Phillip W.; Dydyk, Robert B.

1999-03-01

Today, the paper document is fast becoming a thing of the past. With the rapid development of fast, inexpensive computing and storage devices, many government and private organizations are archiving their documents in electronic form (e.g., personnel records, medical records, patents, etc.). In addition, many organizations are converting their paper archives to electronic images, which are stored in a computer database. Because of this, there is a need to efficiently organize this data into comprehensive and accessible information resources. The Imaged Document Optical Correlation and Conversion System (IDOCCS) provides a total solution to the problem of managing and retrieving textual and graphic information from imaged document archives. At the heart of IDOCCS, optical correlation technology provides the search and retrieval capability of document images. The IDOCCS can be used to rapidly search for key words or phrases within the imaged document archives and can even determine the types of languages contained within a document. In addition, IDOCCS can automatically compare an input document with the archived database to determine if it is a duplicate, thereby reducing the overall resources required to maintain and access the document database. Embedded graphics on imaged pages can also be exploited, e.g., imaged documents containing an agency's seal or logo, or documents with a particular individual's signature block, can be singled out. With this dual capability, IDOCCS outperforms systems that rely on optical character recognition as a basis for indexing and storing only the textual content of documents for later retrieval.

Spectrum splitting metrics and effect of filter characteristics on photovoltaic system performance.

PubMed

Russo, Juan M; Zhang, Deming; Gordon, Michael; Vorndran, Shelby; Wu, Yuechen; Kostuk, Raymond K

2014-03-10

During the past few years there has been a significant interest in spectrum splitting systems to increase the overall efficiency of photovoltaic solar energy systems. However, methods for comparing the performance of spectrum splitting systems and the effects of optical spectral filter design on system performance are not well developed. This paper addresses these two areas. The system conversion efficiency is examined in detail and the role of optical spectral filters with respect to the efficiency is developed. A new metric termed the Improvement over Best Bandgap is defined which expresses the efficiency gain of the spectrum splitting system with respect to a similar system that contains the highest constituent single bandgap photovoltaic cell. This parameter indicates the benefit of using the more complex spectrum splitting system with respect to a single bandgap photovoltaic system. Metrics are also provided to assess the performance of experimental spectral filters in different spectrum splitting configurations. The paper concludes by using the methodology to evaluate spectrum splitting systems with different filter configurations and indicates the overall efficiency improvement that is possible with ideal and experimental designs.

Detecting a pronounced delocalized state in third-harmonic generation phenomenon; a quantum chaos approach

NASA Astrophysics Data System (ADS)

Behnia, S.; Ziaei, J.; Khodavirdizadeh, M.

2018-06-01

Nonlinear optics (NLO) deserves special attention in new optical devices, making it possible to generate coherent light more efficiently. Among the various NLO phenomena the third-harmonic generation (THG) is at the core of the effective operating mechanism of broadband wavelength conversion, in all-optical devices. Here, we aim to understand how the third-order susceptibility and the electric field may be effectively effect on the localization properties of the light in the THG process when included in a two-mode cavity coherently perturbed by a classical field. We address a stable-unstable transition due to the combination effect of the aforementioned factors. We report a reliable evidence confirming the appearance of chaos in THG under suitable conditions. By tracing the signatures of adjacent-spectral-spacing-ratio (ASSR) distribution and participation ratio, we also find a critical point (ɛc ,κc) =(3 . 1 , 0 . 35) for which a pronounced delocalized response is seen. This study may have profound findings for practical devices, and ushers in new opportunities for practical exploitation of the electric field and the third-order susceptibility effect in nonlinear optical devices.

Nonlinear silicon photonics

NASA Astrophysics Data System (ADS)

Tsia, Kevin K.; Jalali, Bahram

2010-05-01

An intriguing optical property of silicon is that it exhibits a large third-order optical nonlinearity, with orders-ofmagnitude larger than that of silica glass in the telecommunication band. This allows efficient nonlinear optical interaction at relatively low power levels in a small footprint. Indeed, we have witnessed a stunning progress in harnessing the Raman and Kerr effects in silicon as the mechanisms for enabling chip-scale optical amplification, lasing, and wavelength conversion - functions that until recently were perceived to be beyond the reach of silicon. With all the continuous efforts developing novel techniques, nonlinear silicon photonics is expected to be able to reach even beyond the prior achievements. Instead of providing a comprehensive overview of this field, this manuscript highlights a number of new branches of nonlinear silicon photonics, which have not been fully recognized in the past. In particular, they are two-photon photovoltaic effect, mid-wave infrared (MWIR) silicon photonics, broadband Raman effects, inverse Raman scattering, and periodically-poled silicon (PePSi). These novel effects and techniques could create a new paradigm for silicon photonics and extend its utility beyond the traditionally anticipated applications.

Numerical and experimental study of a high port-density WDM optical packet switch architecture for data centers.

PubMed

Di Lucente, S; Luo, J; Centelles, R Pueyo; Rohit, A; Zou, S; Williams, K A; Dorren, H J S; Calabretta, N

2013-01-14

Data centers have to sustain the rapid growth of data traffic due to the increasing demand of bandwidth-hungry internet services. The current intra-data center fat tree topology causes communication bottlenecks in the server interaction process, power-hungry O-E-O conversions that limit the minimum latency and the power efficiency of these systems. In this paper we numerically and experimentally investigate an optical packet switch architecture with modular structure and highly distributed control that allow configuration times in the order of nanoseconds. Numerical results indicate that the candidate architecture scaled over 4000 ports, provides an overall throughput over 50 Tb/s and a packet loss rate below 10(-6) while assuring sub-microsecond latency. We present experimental results that demonstrate the feasibility of a 16x16 optical packet switch based on parallel 1x4 integrated optical cross-connect modules. Error-free operations can be achieved with 4 dB penalty while the overall energy consumption is of 66 pJ/b. Based on those results, we discuss feasibility to scale the architecture to a much larger port count.

Si-rich SiNx based Kerr switch enables optical data conversion up to 12 Gbit/s

PubMed Central

Lin, Gong-Ru; Su, Sheng-Pin; Wu, Chung-Lun; Lin, Yung-Hsiang; Huang, Bo-Ji; Wang, Huai-Yung; Tsai, Cheng-Ting; Wu, Chih-I; Chi, Yu-Chieh

2015-01-01

Silicon photonic interconnection on chip is the emerging issue for next-generation integrated circuits. With the Si-rich SiNx micro-ring based optical Kerr switch, we demonstrate for the first time the wavelength and format conversion of optical on-off-keying data with a bit-rate of 12 Gbit/s. The field-resonant nonlinear Kerr effect enhances the transient refractive index change when coupling the optical data-stream into the micro-ring through the bus waveguide. This effectively red-shifts the notched dip wavelength to cause the format preserved or inversed conversion of data carried by the on-resonant or off-resonant probe, respectively. The Si quantum dots doped Si-rich SiNx strengthens its nonlinear Kerr coefficient by two-orders of magnitude higher than that of bulk Si or Si3N4. The wavelength-converted and cross-amplitude-modulated probe data-stream at up to 12-Gbit/s through the Si-rich SiNx micro-ring with penalty of −7 dB on transmission has shown very promising applicability to all-optical communication networks. PMID:25923653

Si-rich SiNx based Kerr switch enables optical data conversion up to 12 Gbit/s.

PubMed

Lin, Gong-Ru; Su, Sheng-Pin; Wu, Chung-Lun; Lin, Yung-Hsiang; Huang, Bo-Ji; Wang, Huai-Yung; Tsai, Cheng-Ting; Wu, Chih-I; Chi, Yu-Chieh

2015-04-29

Silicon photonic interconnection on chip is the emerging issue for next-generation integrated circuits. With the Si-rich SiNx micro-ring based optical Kerr switch, we demonstrate for the first time the wavelength and format conversion of optical on-off-keying data with a bit-rate of 12 Gbit/s. The field-resonant nonlinear Kerr effect enhances the transient refractive index change when coupling the optical data-stream into the micro-ring through the bus waveguide. This effectively red-shifts the notched dip wavelength to cause the format preserved or inversed conversion of data carried by the on-resonant or off-resonant probe, respectively. The Si quantum dots doped Si-rich SiNx strengthens its nonlinear Kerr coefficient by two-orders of magnitude higher than that of bulk Si or Si3N4. The wavelength-converted and cross-amplitude-modulated probe data-stream at up to 12-Gbit/s through the Si-rich SiNx micro-ring with penalty of -7 dB on transmission has shown very promising applicability to all-optical communication networks.

Rapidly reconfigurable all-optical universal logic gate

DOEpatents

Goddard, Lynford L.; Bond, Tiziana C.; Kallman, Jeffrey S.

2010-09-07

A new reconfigurable cascadable all-optical on-chip device is presented. The gate operates by combining the Vernier effect with a novel effect, the gain-index lever, to help shift the dominant lasing mode from a mode where the laser light is output at one facet to a mode where it is output at the other facet. Since the laser remains above threshold, the speed of the gate for logic operations as well as for reprogramming the function of the gate is primarily limited to the small signal optical modulation speed of the laser, which can be on the order of up to about tens of GHz. The gate can be rapidly and repeatedly reprogrammed to perform any of the basic digital logic operations by using an appropriate analog optical or electrical signal at the gate selection port. Other all-optical functionality includes wavelength conversion, signal duplication, threshold switching, analog to digital conversion, digital to analog conversion, signal routing, and environment sensing. Since each gate can perform different operations, the functionality of such a cascaded circuit grows exponentially.

Thin film solar cells grown by organic vapor phase deposition

NASA Astrophysics Data System (ADS)

Yang, Fan

Organic solar cells have the potential to provide low-cost photovoltaic devices as a clean and renewable energy resource. In this thesis, we focus on understanding the energy conversion process in organic solar cells, and improving the power conversion efficiencies via controlled growth of organic nanostructures. First, we explain the unique optical and electrical properties of organic materials used for photovoltaics, and the excitonic energy conversion process in donor-acceptor heterojunction solar cells that place several limiting factors of their power conversion efficiency. Then, strategies for improving exciton diffusion and carrier collection are analyzed using dynamical Monte Carlo models for several nanostructure morphologies. Organic vapor phase deposition is used for controlling materials crystallization and film morphology. We improve the exciton diffusion efficiency while maintaining good carrier conduction in a bulk heterojunction solar cell. Further efficiency improvement is obtained in a novel nanocrystalline network structure with a thick absorbing layer, leading to the demonstration of an organic solar cell with 4.6% efficiency. In addition, solar cells using simultaneously active heterojunctions with broad spectral response are presented. We also analyze the efficiency limits of single and multiple junction organic solar cells, and discuss the challenges facing their practical implementations.

Efficient extreme-UV-to-extreme-UV conversion by four-wave mixing with intense near-IR pulses in highly charged ion plasmas

NASA Astrophysics Data System (ADS)

Chu, Hsu-hsin; Wang, Jyhpyng

2018-05-01

Nonlinear optics in the extreme-ultraviolet (EUV) has been limited by lack of transparent media and small conversion efficiency. To overcome this problem we explore the advantage of using multiply charged ion plasmas as the interacting media between EUV and intense near-infrared (NIR) pulses. Such media are transparent to EUV and can withstand intense NIR driving pulses without damage. We calculate the third-order nonlinear polarizabilities of Ar2 + and Ar3 + ions for EUV and NIR four-wave mixing by using the well-proven Cowan code and find that the EUV-to-EUV conversion efficiency as high as 26% can be expected for practical experimental configurations using multi-terawatt NIR lasers. Such a high efficiency is possible because the driving pulse intensity can be scaled up to several orders of magnitude higher than in conventional nonlinear media, and the group-velocity and phase mismatch are insignificant at the experimental plasma densities. This effective scheme of wave mixing can be utilized for ultrafast EUV waveform measurement and control as well as wavelength conversion.

Pulsed and cw laser oscillations in LiF:F-2 color center crystal under laser diode pumping.

PubMed

Basiev, Tasoltan T; Vassiliev, Sergey V; Konjushkin, Vasily A; Gapontsev, Valentin P

2006-07-15

Continuous-wave laser oscillations in LiF:F-2 crystal optically pumped by a laser diode at 970 nm were demonstrated for what is believed to be the first time. The slope efficiency of 14% and conversion efficiency of 5.5% were achieved for 80 micros pump pulse duration and 5 Hz pulse repetition rate. An efficiency twice as low was measured at a 6.25 kHz pulse repetition rate (50% off-duty factor) and in cw mode of laser operation.

Narrowband, tunable, 2 µm optical parametric master-oscillator power amplifier with large-aperture periodically poled Rb:KTP

NASA Astrophysics Data System (ADS)

Coetzee, R. S.; Zheng, X.; Fregnani, L.; Laurell, F.; Pasiskevicius, V.

2018-06-01

A high-energy, ns, narrow-linewidth optical parametric oscillator and amplifier system based on large-aperture periodically poled Rb:KTP is presented. The 2 µm seed source is a singly resonant OPO locked with a transversely chirped volume Bragg grating, allowing a wavelength tuning of 21 nm and output linewidth of 0.56 nm. A maximum output energy of 52 mJ and conversion efficiency of 36% was obtained from the amplifier for a pump energy of 140 mJ. The high-energy and the robust and narrow dual-wavelength spectra obtained make this system an ideal pump source for difference frequency generation-based THz generation schemes.

High resolution kilometric range optical telemetry in air by radio frequency phase measurement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guillory, Joffray; García-Márquez, Jorge; Truong, Daniel

2016-07-15

We have developed an optical Absolute Distance Meter (ADM) based on the measurement of the phase accumulated by a Radio Frequency wave during its propagation in the air by a laser beam. In this article, the ADM principle will be described and the main results will be presented. In particular, we will emphasize how the choice of an appropriate photodetector can significantly improve the telemeter performances by minimizing the amplitude to phase conversion. Our prototype, tested in the field, has proven its efficiency with a resolution better than 15 μm for a measurement time of 10 ms and distances upmore » to 1.2 km.« less

Simulation and analysis of OOK-to-BPSK format conversion based on gain-transparent SOA used as optical phase-modulator.

PubMed

Hong, Wei; Huang, Dexiu; Zhang, Xinliang; Zhu, Guangxi

2007-12-24

All-optical on-off keying (OOK) to binary phase-shift keying (BPSK) modulation format conversion based on gain-transparent semiconductor optical amplifier (GT-SOA) is simulated and analyzed, where GT-SOA is used as an all-optical phase-modulator (PM). Numerical simulation of the phase modulation effect of GT-SOA is performed using a wideband dynamic model of GT-SOA and the quality of the BPSK signal is evaluated using the differential-phase-Q factor. Performance improvement by holding light injection is analyzed and non-return-to-zero (NRZ) and return-to-zero (RZ) modulation formats of the OOK signal are considered.

High photon-to-heat conversion efficiency in the wavelength region of 250–1200 nm based on a thermoelectric Bi2Te3 film structure

PubMed Central

Hu, Er-Tao; Yao, Yuan; Zang, Kai-Yan; Liu, Xin-Xing; Jiang, An-Qing; Zheng, Jia-Jin; Yu, Ke-Han; Wei, Wei; Zheng, Yu-Xiang; Zhang, Rong-Jun; Wang, Song-You; Zhao, Hai-Bin; Yoshie, Osamu; Lee, Young-Pak; Wang, Cai-Zhuang; Lynch, David W.; Guo, Jun-Peng; Chen, Liang-Yao

2017-01-01

In this work, 4-layered SiO2/Bi2Te3/SiO2/Cu film structures were designed and fabricated and the optical properties investigated in the wavelength region of 250–1200 nm for their promising applications for direct solar-thermal-electric conversion. A typical 4-layered film sample with the structure SiO2 (66.6 nm)/Bi2Te3 (7.0 nm)/SiO2 (67.0 nm)/Cu (>100.0 nm) was deposited on a Si or K9-glass substrate by magnetron sputtering. The experimental results agree well with the simulated ones showing an average optical absorption of 96.5%, except in the shorter wavelength region, 250–500 nm, which demonstrates the superior absorption property of the 4-layered film due to the randomly rough surface of the Cu layer resulting from the higher deposition power. The high reflectance of the film structure in the long wavelength region of 2–20 μm will result in a low thermal emittance, 0.064 at 600 K. The simpler 4-layered structure with the thermoelectric Bi2Te3 used as the absorption layer may provide a straightforward way to obtain solar-thermal-electric conversion more efficiently through future study. PMID:28300178

Optical Analysis of Transparent Polymeric Material Exposed to Simulated Space Environment

NASA Technical Reports Server (NTRS)

Edwards, David L.; Finckenor, Miria M.

1999-01-01

Transparent polymeric materials are being designed and utilized as solar concentrating lenses for spacecraft power and propulsion systems. These polymeric lenses concentrate solar energy onto energy conversion devices such as solar cells and thermal energy systems. The conversion efficiency is directly related to the transmissivity of the polymeric lens. The Environmental Effects Group of the Marshall Space Flight Center's Materials, Processes, and Manufacturing Department exposed a variety of materials to a simulated space environment and evaluated them for an, change in optical transmission. These materials include Lexan(TM), polyethylene terephthalate (PET). several formulations of Tefzel(TM). and Teflon(TM), and silicone DC 93-500. Samples were exposed to a minimum of 1000 Equivalent Sun Hours (ESH) of near-UV radiation (250 - 400 nm wavelength). Data will be presented on materials exposed to charged particle radiation equivalent to a five-year dose in geosynchronous orbit. These exposures were performed in MSFC's Combined Environmental Effects Test Chamber, a unique facility with the capability to expose materials simultaneously or sequentially to protons, low-energy electrons, high-energy electrons, near UV radiation and vacuum UV radiation.Prolonged exposure to the space environment will decrease the polymer film's transmission and thus reduce the conversion efficiency. A method was developed to normalize the transmission loss and thus rank the materials according to their tolerance to space environmental exposure. Spectral results and the material ranking according to transmission loss are presented.

Photoelectrochemical Cell of Hybrid Regioregular POLY(3-HEXYLTHIOPHENE-2,5-DIYL) and Molybdenum Disulfide Film

NASA Astrophysics Data System (ADS)

Abdelmola, Fatmaelzahraa M.; Ram, Manoj K.; Takshi, Arash; Stafanakos, Elias; Kumar, Ashok; Goswami, D. Yogi

The photoelectrochemical cell attracts attention worldwide due to conversion of optical energy into electricity, production of hydrogen through water splitting and use in photodetector and photo-sensor applications. We have been working on the photochemical cell based on regioregular polyhexylthiophenes hybrid-structured films for photoelectrochemical and photovoltaic applications. This paper discusses the hybrid film studies on regioregular poly(3-hexylthiophene-2,5-diyl) (P3HT) with 2D molybdenum disulfide (MoS2) for photoelectrochemical cell. The hybrid P3HT/MoS2 films deposited over indium tin oxide (ITO)-coated glass plate or n-type silicon substrates were characterized using FTIR, UV/vis, electrochemical and scanning electron microscopy (SEM) techniques. The optical measurements showed a higher absorption magnitude with low reflection properties of P3HT/MoS2 hybrid films revealing a superior photocurrent compared to both P3HT and MoS2 films. The P3HT/MoS2 hybrid-based photoelectrochemical cell yielded a short-circuit current (Isc) of 183.16μAṡcm-2, open-circuit voltage (Voc) of 0.92V, fill factor (FF) of 25% and power conversion efficiency (η) of 0.18% under the light intensity of 242Wṡm-2. The estimated power conversion efficiency and fill factor are comparable to organic-based photovoltaic devices.

Direct measurement of optoacoustic induced ultrasonic waves

NASA Astrophysics Data System (ADS)

Kuo, C.-Y.; Patel, C. K. N.

1984-04-01

A two-beam optically induced photoacoustic grating and its low frequency ultrasonic waves are measured with a thin film transducer in low concentration dye solution. The acoustic power generated is measured for a weakly absorbing medium to be equal to about 5 W sq cm, indicating high conversion efficiency. Application of this direct detection as a laser beam profiler is also discussed.

Process simulation in digital camera system

NASA Astrophysics Data System (ADS)

Toadere, Florin

2012-06-01

The goal of this paper is to simulate the functionality of a digital camera system. The simulations cover the conversion from light to numerical signal and the color processing and rendering. We consider the image acquisition system to be linear shift invariant and axial. The light propagation is orthogonal to the system. We use a spectral image processing algorithm in order to simulate the radiometric properties of a digital camera. In the algorithm we take into consideration the transmittances of the: light source, lenses, filters and the quantum efficiency of a CMOS (complementary metal oxide semiconductor) sensor. The optical part is characterized by a multiple convolution between the different points spread functions of the optical components. We use a Cooke triplet, the aperture, the light fall off and the optical part of the CMOS sensor. The electrical part consists of the: Bayer sampling, interpolation, signal to noise ratio, dynamic range, analog to digital conversion and JPG compression. We reconstruct the noisy blurred image by blending different light exposed images in order to reduce the photon shot noise, also we filter the fixed pattern noise and we sharpen the image. Then we have the color processing blocks: white balancing, color correction, gamma correction, and conversion from XYZ color space to RGB color space. For the reproduction of color we use an OLED (organic light emitting diode) monitor. The analysis can be useful to assist students and engineers in image quality evaluation and imaging system design. Many other configurations of blocks can be used in our analysis.

Impact of hydrogen dilution on optical properties of intrinsic hydrogenated amorphous silicon films prepared by high density plasma chemical vapor deposition for solar cell applications

NASA Astrophysics Data System (ADS)

Chen, Huai-Yi; Lee, Yao-Jen; Chang, Chien-Pin; Koo, Horng-Show; Lai, Chiung-Hui

2013-01-01

P-i-n single-junction hydrogenated amorphous silicon (a-Si:H) thin film solar cells were successfully fabricated in this study on a glass substrate by high density plasma chemical vapor deposition (HDP-CVD) at low power of 50 W, low temperature of 200°C and various hydrogen dilution ratios (R). The open circuit voltage (Voc ), short circuit current density (Jsc ), fill factor (FF) and conversion efficiency (η) of the solar cell as well as the refractive index (n) and absorption coefficient (α) of the i-layer at 600 nm wavelength rise with increasing R until an abrupt drop at high hydrogen dilution, i.e. R > 0.95. However, the optical energy bandgap (Eg ) of the i-layer decreases with the R increase. Voc and α are inversely correlated with Eg . The hydrogen content affects the i-layer and p/i interface quality of the a-Si:H thin film solar cell with an optimal value of R = 0.95, which corresponds to solar cell conversion efficiency of 3.85%. The proposed a-Si:H thin film solar cell is expected to be improved in performance.

Mode-locked Yb:YAG thin-disk oscillator with 41 µJ pulse energy at 145 W average infrared power and high power frequency conversion.

PubMed

Bauer, Dominik; Zawischa, Ivo; Sutter, Dirk H; Killi, Alexander; Dekorsy, Thomas

2012-04-23

We demonstrate the generation of 1.1 ps pulses containing more than 41 µJ of energy directly out of an Yb:YAG thin-disk without any additional amplification stages. The laser oscillator operates in ambient atmosphere with a 3.5 MHz repetition rate and 145 W of average output power at a fundamental wavelength of 1030 nm. An average output power of 91.5 W at 515 nm was obtained by frequency doubling with a conversion efficiency exceeding 65%. Third harmonic generation resulted in 34 W at 343 nm at 34% efficiency. © 2012 Optical Society of America

> 6 MW peak power at 532 nm from passively Q-switched Nd:YAG/Cr4+:YAG microchip laser.

PubMed

Bhandari, Rakesh; Taira, Takunori

2011-09-26

Megawatt peak power, giant pulse microchip lasers are attractive for wavelength conversion, provided their output is linearly polarized. We use a [110] cut Cr(4+):YAG for passively Q-switched Nd:YAG microchip laser to obtain a stable, linearly polarized output. Further, we optimize the conditions for second harmonic generation at 532 nm wavelength to achieve > 6 MW peak power, 1.7 mJ, 265 ps, 100 Hz pulses with a conversion efficiency of 85%. © 2011 Optical Society of America

Simultaneous wavelength and format conversion in SDN/NFV for flexible optical network based on FWM in SOA

NASA Astrophysics Data System (ADS)

Zhan, Yueying; Wang, Danshi; Zhang, Min

2018-04-01

We propose an all-optical wavelength and format conversion model (CM) for a dynamic data center interconnect node and coherent passive optical network (PON) optical network unit (ONU) in software-defined networking and network function virtualization system based on four-wave mixing in a semiconductor optical amplifier. Five wavelength converted DQPSK signals and two format converted DPSK signals are generated; the performances of the generated signals for two strategies of setting CM in the data center interconnect node and coherent PON ONU, which are over 10 km fiber transmission, have been verified. All of the converted signals are with a power penalty less than 2.2 dB at FEC threshold of 3.8 × 10 - 3, and the optimum bias current of SOA is 300 mA.

Nonreciprocal Transverse Photonic Spin and Magnetization-Induced Electromagnetic Spin-Orbit Coupling

PubMed Central

Levy, Miguel; Karki, Dolendra

2017-01-01

We present a formulation of electromagnetic spin-orbit coupling in magneto-optic media, and propose an alternative source of spin-orbit coupling to non-paraxial optics vortices. Our treatment puts forth a formulation of nonreciprocal transverse-spin angular-momentum-density shifts for evanescent waves in magneto-optic waveguide media. It shows that magnetization-induced electromagnetic spin-orbit coupling is possible, and that it leads to unequal spin to orbital angular momentum conversion in magneto-optic media evanescent waves in opposite propagation-directions. Generation of free-space helicoidal beams based on this conversion is shown to be spin-helicity- and magnetization-dependent. We show that transverse-spin to orbital angular momentum coupling into magneto-optic waveguide media engenders spin-helicity-dependent unidirectional propagation. This unidirectional effect produces different orbital angular momenta in opposite directions upon excitation-spin-helicity reversals. PMID:28059120

Effective preemptive scheduling scheme for optical burst-switched networks with cascaded wavelength conversion consideration

NASA Astrophysics Data System (ADS)

Gao, Xingbo

2010-03-01

We introduce a new preemptive scheduling technique for next-generation optical burst switching (OBS) networks considering the impact of cascaded wavelength conversions. It has been shown that when optical bursts are transmitted all optically from source to destination, each wavelength conversion performed along the lightpath may cause certain signal-to-noise deterioration. If the distortion of the signal quality becomes significant enough, the receiver would not be able to recover the original data. Accordingly, subject to this practical impediment, we improve a recently proposed fair channel scheduling algorithm to deal with the fairness problem and aim at burst loss reduction simultaneously in OBS environments. In our scheme, the dynamic priority associated with each burst is based on a constraint threshold and the number of already conducted wavelength conversions among other factors for this burst. When contention occurs, a new arriving superior burst may preempt another scheduled one according to their priorities. Extensive simulation results have shown that the proposed scheme further improves fairness and achieves burst loss reduction as well.

Hyperbola-parabola primary mirror in Cassegrain optical antenna to improve transmission efficiency.

PubMed

Zhang, Li; Chen, Lu; Yang, HuaJun; Jiang, Ping; Mao, Shengqian; Caiyang, Weinan

2015-08-20

An optical model with a hyperbola-parabola primary mirror added in the Cassegrain optical antenna, which can effectively improve the transmission efficiency, is proposed in this paper. The optimum parameters of a hyperbola-parabola primary mirror and a secondary mirror for the optical antenna system have been designed and analyzed in detail. The parabola-hyperbola primary structure optical antenna is obtained to improve the transmission efficiency of 10.60% in theory, and the simulation efficiency changed 9.359%. For different deflection angles to the receiving antenna with the emit antenna, the coupling efficiency curve of the optical antenna has been obtained.

Transparent nickel selenide alloy counter electrodes for bifacial dye-sensitized solar cells exceeding 10% efficiency.

PubMed

Duan, Yanyan; Tang, Qunwei; He, Benlin; Li, Ru; Yu, Liangmin

2014-11-07

In the current work, we report a series of bifacial dye-sensitized solar cells (DSSCs) that provide power conversion efficiencies of more than 10% from bifacial irradiation. The device comprises an N719-sensitized TiO2 anode, a transparent nickel selenide (Ni-Se) alloy counter electrode (CE), and liquid electrolyte containing I(-)/I3(-) redox couples. Because of the high optical transparency, electron conduction ability, electrocatalytic activity of Ni-Se CEs, as well as dye illumination, electron excitation and power conversion efficiency have been remarkably enhanced. Results indicate that incident light from a transparent CE has a compensation effect to the light from the anode. The impressive efficiency along with simple preparation of the cost-effective Ni-Se alloy CEs highlights the potential application of bifacial illumination technique in robust DSSCs.

High-yield, ultrafast, surface plasmon-enhanced, Au nanorod optical field electron emitter arrays.

PubMed

Hobbs, Richard G; Yang, Yujia; Fallahi, Arya; Keathley, Philip D; De Leo, Eva; Kärtner, Franz X; Graves, William S; Berggren, Karl K

2014-11-25

Here we demonstrate the design, fabrication, and characterization of ultrafast, surface-plasmon enhanced Au nanorod optical field emitter arrays. We present a quantitative study of electron emission from Au nanorod arrays fabricated by high-resolution electron-beam lithography and excited by 35 fs pulses of 800 nm light. We present accurate models for both the optical field enhancement of Au nanorods within high-density arrays, and electron emission from those nanorods. We have also studied the effects of surface plasmon damping induced by metallic interface layers at the substrate/nanorod interface on near-field enhancement and electron emission. We have identified the peak optical field at which the electron emission mechanism transitions from a 3-photon absorption mechanism to strong-field tunneling emission. Moreover, we have investigated the effects of nanorod array density on nanorod charge yield, including measurement of space-charge effects. The Au nanorod photocathodes presented in this work display 100-1000 times higher conversion efficiency relative to previously reported UV triggered emission from planar Au photocathodes. Consequently, the Au nanorod arrays triggered by ultrafast pulses of 800 nm light in this work may outperform equivalent UV-triggered Au photocathodes, while also offering nanostructuring of the electron pulse produced from such a cathode, which is of interest for X-ray free-electron laser (XFEL) development where nanostructured electron pulses may facilitate more efficient and brighter XFEL radiation.

Contemporaneous Ultraviolet and Optical Observations of Direct and Raman-scattered O VI Lines in Symbiotic Stars

NASA Astrophysics Data System (ADS)

Birriel, Jennifer J.; Espey, Brian R.; Schulte-Ladbeck, Regina E.

2000-12-01

Symbiotic stars are binary systems consisting of a hot star, typically a white dwarf, and a cool giant companion. The wind from the cool star is ionized by the radiation from the hot star, resulting in the characteristic combination of sharp nebular emission lines and stellar molecular absorption bands in the optical spectrum. Most of the emission lines are readily identifiable with common ions. However, two strong, broad emission lines at 6825 and 7082 Å defied identification with known atoms and ions. In 1989 Schmid made the case that these long unidentified emission lines resulted from the Raman scattering of the O VI resonance photons at 1032, 1038 Å by neutral hydrogen. We present contemporaneous far-UV and optical observations of direct and Raman-scattered O VI lines for nine symbiotic stars obtained with the Hopkins Ultraviolet Telescope (Astro-2) and various ground-based optical telescopes. The O VI emission lines are present in every instance in which the λλ6825, 7082 lines are present, in support of the Schmid Raman-scattering model. We calculate the scattering efficiencies and discuss the results in terms of the Raman-scattering model. Additionally, we measure the flux of the Fe II fluorescence line at 1776 Å, which is excited by the O VI line at 1032 Å, and calculate the first estimates of the conversion efficiencies for this process.

Ka-Band Link Study and Analysis for a Mars Hybrid RF/Optical Software Defined Radio

NASA Technical Reports Server (NTRS)

Zeleznikar, Daniel J.; Nappier, Jennifer M.; Downey, Joseph A.

2014-01-01

The integrated radio and optical communications (iROC) project at the NASA Glenn Research Center (GRC) is investigating the feasibility of a hybrid RF and optical communication subsystem for future deep space missions. The hybrid communications subsystem enables the advancement of optical communications while simultaneously mitigating the risk of infusion by combining an experimental optical transmitter and telescope with a reliable Ka-band RF transmitter and antenna. The iROC communications subsystem seeks to maximize the total data return over the course of a potential 2-year mission in Mars orbit beginning in 2021. Although optical communication by itself offers potential for greater data return over RF, the reliable Ka-band link is also being designed for high data return capability in this hybrid system. A daily analysis of the RF link budget over the 2-year span is performed to optimize and provide detailed estimates of the RF data return. In particular, the bandwidth dependence of these data return estimates is analyzed for candidate waveforms. In this effort, a data return modeling tool was created to analyze candidate RF modulation and coding schemes with respect to their spectral efficiency, amplifier output power back-off, required digital to analog conversion (DAC) sampling rates, and support by ground receivers. A set of RF waveforms is recommended for use on the iROC platform.

Virtually assisted optical colonoscopy

NASA Astrophysics Data System (ADS)

Marino, Joseph; Qiu, Feng; Kaufman, Arie

2008-03-01

We present a set of tools used to enhance the optical colonoscopy procedure in a novel manner with the aim of improving both the accuracy and efficiency of this procedure. In order to better present the colon information to the gastroenterologist performing a conventional (optical) colonoscopy, we undistort the radial distortion of the fisheye view of the colonoscope. The radial distortion is modeled with a function that converts the fisheye view to the perspective view, where the shape and size of polyps can be more readily observed. The conversion, accelerated on the graphics processing unit and running in real-time, calculates the corresponding position in the fisheye view of each pixel on the perspective image. We also merge our previous work in computer-aided polyp detection for virtual colonoscopy into the optical colonoscopy environment. The physical colonoscope path in the optical colonoscopy is approximated with the hugging corner shortest path, which is correlated with the centerline in the virtual colonoscopy. With the estimated distance that the colonoscope has been inserted, we are able to provide the gastroenterologist with visual cues along the observation path as to the location of possible polyps found by the detection process. In order to present the information to the gastroenterologist in a non-intrusive manner, we have developed a friendly user interface to enhance the optical colonoscopy without being cumbersome, distracting, or resulting in a more lackadaisical inspection by the gastroenterologist.

All-optical analog comparator.

PubMed

Li, Pu; Yi, Xiaogang; Liu, Xianglian; Zhao, Dongliang; Zhao, Yongpeng; Wang, Yuncai

2016-08-23

An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical '1' or '0' by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function.

All-optical analog comparator

PubMed Central

Li, Pu; Yi, Xiaogang; Liu, Xianglian; Zhao, Dongliang; Zhao, Yongpeng; Wang, Yuncai

2016-01-01

An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical ‘1’ or ‘0’ by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function. PMID:27550874

All-optical analog comparator

NASA Astrophysics Data System (ADS)

Li, Pu; Yi, Xiaogang; Liu, Xianglian; Zhao, Dongliang; Zhao, Yongpeng; Wang, Yuncai

2016-08-01

An analog comparator is one of the core units in all-optical analog-to-digital conversion (AO-ADC) systems, which digitizes different amplitude levels into two levels of logical ‘1’ or ‘0’ by comparing with a defined decision threshold. Although various outstanding photonic ADC approaches have been reported, almost all of them necessitate an electrical comparator to carry out this binarization. The use of an electrical comparator is in contradiction to the aim of developing all-optical devices. In this work, we propose a new concept of an all-optical analog comparator and numerically demonstrate an implementation based on a quarter-wavelength-shifted distributed feedback laser diode (QWS DFB-LD) with multiple quantum well (MQW) structures. Our results show that the all-optical comparator is very well suited for true AO-ADCs, enabling the whole digital conversion from an analog optical signal (continuous-time signal or discrete pulse signal) to a binary representation totally in the optical domain. In particular, this all-optical analog comparator possesses a low threshold power (several mW), high extinction ratio (up to 40 dB), fast operation rate (of the order of tens of Gb/s) and a step-like transfer function.

Exceeding the solar cell Shockley-Queisser limit via thermal up-conversion of low-energy photons

NASA Astrophysics Data System (ADS)

Boriskina, Svetlana V.; Chen, Gang

2014-03-01

Maximum efficiency of ideal single-junction photovoltaic (PV) cells is limited to 33% (for 1 sun illumination) by intrinsic losses such as band edge thermalization, radiative recombination, and inability to absorb below-bandgap photons. This intrinsic thermodynamic limit, named after Shockley and Queisser (S-Q), can be exceeded by utilizing low-energy photons either via their electronic up-conversion or via the thermophotovoltaic (TPV) conversion process. However, electronic up-conversion systems have extremely low efficiencies, and practical temperature considerations limit the operation of TPV converters to the narrow-gap PV cells. Here we develop a conceptual design of a hybrid TPV platform, which exploits thermal up-conversion of low-energy photons and is compatible with conventional silicon PV cells by using spectral and directional selectivity of the up-converter. The hybrid platform offers sunlight-to-electricity conversion efficiency exceeding that imposed by the S-Q limit on the corresponding PV cells across a broad range of bandgap energies, under low optical concentration (1-300 suns), operating temperatures in the range 900-1700 K, and in simple flat panel designs. We demonstrate maximum conversion efficiency of 73% under illumination by non-concentrated sunlight. A detailed analysis of non-ideal hybrid platforms that allows for up to 15% of absorption/re-emission losses yields limiting efficiency value of 45% for Si PV cells.

Structure, spectroscopic properties and laser performance of Nd:YNbO4 at 1066 nm

NASA Astrophysics Data System (ADS)

Ding, Shoujun; Peng, Fang; Zhang, Qingli; Luo, Jianqiao; Liu, Wenpeng; Sun, Dunlu; Dou, Renqin; Sun, Guihua

2016-12-01

We have demonstrated continuous wave (CW) laser operation of Nd:YNbO4 crystal at 1066 nm for the first time. A maximum output power of 1.12 W with the incident power of 5.0 W is successfully achieved corresponding to an optical-to-optical conversion efficiency of 22.4% and a slope efficiency of 24.0%. The large absorption cross section (8.7 × 10-20 cm2) and wide absorption band (6 nm) at around 808 nm indicates the good pumping efficiency by laser diodes (LD). The small emission cross section (29 × 10-20 cm2) and relative long lifetime of the 4F3/2 → 4I11/2 transition indicates good energy storage capacity of Nd:YNbO4. Moreover, the raw materials of Nd:YNbO4 are stable, thus, it can grow high-quality and large-size by Czochralski (CZ) method. Therefore the Nd:YNbO4 crystal is a potentially new laser material suitable for LD pumping.

Investigative study of a diode-pumped continuous-wave Tm:YAP laser as an efficient 1.94 μm pump source

NASA Astrophysics Data System (ADS)

Kwiatkowski, Jacek; Zendzian, Waldemar; Jabczynski, Jan K.

2016-12-01

A detailed study of a Tm:YAP laser in continuous-wave (CW), single-pass end-pumped by a 793 nm diode laser is presented. The laser based on c-cut 3 at. % Tm:YAP crystal was experimentally examined and presented in the dependence on transmittance and radius of curvature of output coupling mirrors. A detailed spectral analysis was presented. The influence of a heat-sink cooling water temperature on the laser performance was studied. At room temperature, for an output coupling transmission of 19.5%, the maximum CW output power of 4.53 W was achieved, corresponding to a slope efficiency of 41.5% and an optical-to-optical conversion efficiency of 25.7% with respect to the incident pump power, respectively. We have shown that the output spectrum at a certain wavelength (e.g. 1940 nm) for a given pump power can be realized via the change of resonator parameters (OC transmittance, mode size).

Broadband Solar Energy Harvesting in Single Nanowire Resonators

NASA Astrophysics Data System (ADS)

Yang, Yiming; Peng, Xingyue; Hyatt, Steven; Yu, Dong

2015-03-01

Sub-wavelength semiconductor nanowires (NWs) can have optical absorption cross sections far beyond their physical sizes at resonance frequencies, offering a powerful method to simultaneously lower the material consumption and enhance photovoltaic performance. The degree of absorption enhancement is expected to substantially increase in materials with high refractive indices, but this has not yet been experimentally demonstrated. Here, we show that the absorption efficiency can be significantly improved in high-index NWs, by a direct observation of 350% external quantum efficiency (EQE) in lead sulfide (PbS) NWs. Broadband absorption enhancement is also realized in tapered NWs, where light of different wavelength is absorbed at segments with different diameters analogous to a tandem solar cell. Our results quantitatively agree with the finite-difference-time-domain (FDTD) simulations. Overall, our single PbS NW Schottky solar cells taking advantage of optical resonance, near bandgap open circuit voltage, and long minority carrier diffusion length exhibit power conversion efficiency comparable to single Si NW coaxial p-n junction cells, while the fabrication complexity is greatly reduced.

Down-conversion emission of Ce3+-Tb3+ co-doped CaF2 hollow spheres and application for solar cells

NASA Astrophysics Data System (ADS)

Cheng, Yufei; Wang, Yongbo; Teng, Feng; Dong, Hua; Chen, Lida; Mu, Jianglong; Sun, Qian; Fan, Jun; Hu, Xiaoyun; Miao, Hui

2018-03-01

Luminescent downconversion is a promising way to harvest ultraviolet sunlight and transform it into visible light that can be absorbed by solar cells, and has potential to improve their photoelectric conversion efficiency. In this work, the uniform hollow spheres and well dispersed CaF2 phosphors doped with rare-earth Ce3+ and Tb3+ ions are prepared by a one-step hydrothermal synthesis method. Benefiting from the stronger ability of absorption and emission and excellent transparency property, we demonstrate that the application of the doped nanocrystals can efficiently improve visible light transmittance. The chosen phosphors are added in the SiO2 sols so as to get the anti-reflection coatings with wavelength conversion bi-functional films, promoting the optical transmittance in the visible and near-infrared range which matches with the range of the band gap energy of silicon semiconductor. Optimized photoelectric conversion efficiency of 14.35% and the external quantum efficiency over 70% from 450 to 950 nm are obtained through the silicon solar cells with 0.10 g phosphors coating. Compared with the pure glass devices, the photoelectric conversion efficiency is enhanced by 0.69%. This work indicates that fluorescent downconversion not only can serve as proof of principles for improving photoelectric conversion efficiency of solar cells but also may be helpful to practical application in the future.

A reconfigurable all-optical VPN based on XGM effect of SOA in WDM PON

NASA Astrophysics Data System (ADS)

Hu, Xiaofeng; Zhang, Liang; Cao, Pan; Wang, Tao; Su, Yikai

2010-12-01

We propose and experimentally demonstrate a reconfigurable all-optical VPN scheme enabling intercommunications among different ONUs in a WDM PON. Reconfiguration is realized by dynamically setting wavelength conversion of optical VPN signal using a SOA in the OLT.

Quasi-phase-matched χ(3 )-parametric interactions in sinusoidally tapered waveguides

NASA Astrophysics Data System (ADS)

Saleh, Mohammed F.

2018-01-01

In this article, I show how periodically tapered waveguides can be employed as efficient quasi-phase-matching schemes for four-wave mixing parametric processes in third-order nonlinear materials. As an example, a thorough study of enhancing third-harmonic generation in sinusoidally tapered fibers has been conducted. The quasi-phase-matching condition has been obtained for nonlinear parametric interactions in these structures using Fourier-series analysis. The dependencies of the conversion efficiency of the third harmonic on the modulation amplitude, tapering period, longitudinal-propagation direction, and pump wavelength have been studied. In comparison to uniform waveguides, the conversion efficiency has been enhanced by orders of magnitudes. I envisage that this work will have a great impact in the field of guided nonlinear optics using centrosymmetric materials.

Modelling and characterization of photothermal effects assisted with gold nanorods in ex vivo samples and in a murine model

NASA Astrophysics Data System (ADS)

Lamela Rivera, Horacio; Rodríguez Jara, Félix; Cunningham, Vincent

2011-03-01

We discuss in this article the implementation of a laser-tissue interaction and bioheat-transfer 2-D finite-element model for Photothermal Therapy assisted with Gold Nanorods. We have selected Gold Nanorods as absorbing nanostructures in order to improve the efficiency of using compact diode lasers because of their high opto-thermal conversion efficiency at 808 and 850 nm. The goal is to model the distribution of the optical energy among the tissue including the skin absorption effects and the tissue thermal response, with and without the presence of Gold Nanorods. The heat generation due to the optical energy absorption and the thermal propagation will be computationally modeled and optimized. The model has been evaluated and compared with experimental ex-vivo data in fresh chicken muscle samples and in-vivo BALB/c mice animal model.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jaekwang; Huang, Jingsong; Sumpter, Bobby G.

Compared with their bulk counterparts, 2D materials can sustain much higher elastic strain at which optical quantities such as bandgaps and absorption spectra governing optoelectronic device performance can be modified with relative ease. Using first-principles density functional theory and quasiparticle GW calculations, we demonstrate how uniaxial tensile strain can be utilized to optimize the electronic and optical properties of transition metal dichalcogenide lateral (in-plane) heterostructures such as MoX 2/WX 2 (X = S, Se, Te). We find that these lateral-type heterostructures may facilitate efficient electron–hole separation for light detection/harvesting and preserve their type II characteristic up to 12% of uniaxialmore » strain. Based on the strain-dependent bandgap and band offset, we show that uniaxial tensile strain can significantly increase the power conversion efficiency of these lateral heterostructures. Our results suggest that these strain-engineered lateral heterostructures are promising for optimizing optoelectronic device performance by selectively tuning the energetics of the bandgap.« less

Synthesis, crystal growth and studies on non-linear optical property of new chalcones

NASA Astrophysics Data System (ADS)

Sarojini, B. K.; Narayana, B.; Ashalatha, B. V.; Indira, J.; Lobo, K. G.

2006-09-01

The synthesis, crystal growth and non-linear optical (NLO) property of new chalcone derivatives are reported. 4-Propyloxy and 4-butoxy benzaldehydes were made to under go Claisen-Schmidt condensation with 4-methoxy, 4-nitro and 4-phenoxy acetophenones to form corresponding chalcones. The newly synthesized compounds were characterized by analytical and spectral data. The Second harmonic generation (SHG) efficiency of these compounds was measured by powder technique using Nd:YAG laser. Among tested compounds three chalcones showed NLO property. The chalcone 1-(4-methoxyphenyl)-3-(4-propyloxy phenyl)-2-propen-1-one exhibited SHG conversion efficiency 2.7 times that of urea. The bulk crystal of 1-(4-methoxyphenyl)-3-(4-butoxyphenyl)-2-propen-1-one (crystal size 65×28×15 mm 3) was grown by slow-evaporation technique from acetone. Microhardness of the crystal was tested by Vicker's microhardness method.

Compact 151 W green laser with U-type resonator for prostate surgery

NASA Astrophysics Data System (ADS)

Bazyar, Hossein; Aghaie, Mohammad; Daemi, Mohammad Hossein; Bagherzadeh, Seyed Morteza

2013-04-01

We analyzed, designed and fabricated a U-type resonator for intra-cavity frequency doubling of a diode-side-pumped Q-switched Nd:YAG rod laser with high power and high stability for surgery of prostatic tissue. The resonator stability conditions were analyzed graphically in the various configurations for a U-type resonator. We obtained green light at 532 nm using a single KTP crystal, with average output power of 151 W at 10 kHz repetition rate, and with 113 ns pulse duration at 810 W input pump power. We achieved 1064-532 nm conversion efficiency of 75.8%, and pump-to-green optical-optical efficiency of 18.6%. The green power fluctuation was ±1.0% and pointing stability was better than 4 μrad. The green laser output was coupled to a side-firing medical fiber to transfer the laser beam to the prostatic tissue.

Design of a terahertz parametric oscillator based on a resonant cavity in a terahertz waveguide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saito, K., E-mail: k-saito@material.tohoku.ac.jp; Oyama, Y.; Tanabe, T.

We demonstrate ns-pulsed pumping of terahertz (THz) parametric oscillations in a quasi-triply resonant cavity in a THz waveguide. The THz waves, down converted through parametric interactions between the pump and signal waves at telecom frequencies, are confined to a GaP single mode ridge waveguide. By combining the THz waveguide with a quasi-triply resonant cavity, the nonlinear interactions can be enhanced. A low threshold pump intensity for parametric oscillations can be achieved in the cavity waveguide. The THz output power can be maximized by optimizing the quality factors of the cavity so that an optical to THz photon conversion efficiency, η{submore » p}, of 0.35, which is near the quantum-limit level, can be attained. The proposed THz optical parametric oscillator can be utilized as an efficient and monochromatic THz source.« less

Broadband and wide-angle light harvesting by ultra-thin silicon solar cells with partially embedded dielectric spheres.

PubMed

Yang, Zhenhai; Shang, Aixue; Qin, Linling; Zhan, Yaohui; Zhang, Cheng; Gao, Pingqi; Ye, Jichun; Li, Xiaofeng

2016-04-01

We propose a design of crystalline silicon thin-film solar cells (c-Si TFSCs, 2 μm-thick) configured with partially embedded dielectric spheres on the light-injecting side. The intrinsic light trapping and photoconversion are simulated by the complete optoelectronic simulation. It shows that the embedding depth of the spheres provides an effective way to modulate and significantly enhance the optical absorption. Compared to the conventional planar and front sphere systems, the optimized partially embedded sphere design enables a broadband, wide-angle, and strong optical absorption and efficient carrier transportation. Optoelectronic simulation predicts that a 2 μm-thick c-Si TFSC with half-embedded spheres shows an increment of more than 10  mA/cm² in short-circuit current density and an enhancement ratio of more than 56% in light-conversion efficiency, compared to the conventional planar counterparts.

Probing Photocurrent Nonuniformities in the Subcells of Monolithic Perovskite/Silicon Tandem Solar Cells.

PubMed

Song, Zhaoning; Werner, Jérémie; Shrestha, Niraj; Sahli, Florent; De Wolf, Stefaan; Niesen, Björn; Watthage, Suneth C; Phillips, Adam B; Ballif, Christophe; Ellingson, Randy J; Heben, Michael J

2016-12-15

Perovskite/silicon tandem solar cells with high power conversion efficiencies have the potential to become a commercially viable photovoltaic option in the near future. However, device design and optimization is challenging because conventional characterization methods do not give clear feedback on the localized chemical and physical factors that limit performance within individual subcells, especially when stability and degradation is a concern. In this study, we use light beam induced current (LBIC) to probe photocurrent collection nonuniformities in the individual subcells of perovskite/silicon tandems. The choices of lasers and light biasing conditions allow efficiency-limiting effects relating to processing defects, optical interference within the individual cells, and the evolution of water-induced device degradation to be spatially resolved. The results reveal several types of microscopic defects and demonstrate that eliminating these and managing the optical properties within the multilayer structures will be important for future optimization of perovskite/silicon tandem solar cells.

Wavelength-tunable thulium-doped fiber laser by employing a self-made Fabry-Perot filter

NASA Astrophysics Data System (ADS)

Wang, Y. P.; Ju, Y. L.; Wu, C. T.; Liu, W.; Yang, C.

2017-06-01

In this demonstration, we proposed a novel wavelength-tunable thulium-doped fiber laser (TDFL) with a self-made Fabry-Perot (F-P) filter. When the F-P filter was not inserted, the maximum output power of 11.1 W was achieved when the pump power was 70.2 W. The corresponding optical-to-optical conversion efficiency was 15.8% and the slope efficiency was 22.1%. When the F-P filter was inserted, the output wavelength could be tuned from 1952.9 to 1934.9 nm with the change of cavity length of F-P filter which was fixed on a piezoelectric ceramic transducer (PZT) controlled by the voltage applied to it. The full width at half maximum (FWHM) was no more than 0.19 nm. Furthermore, the wavelength fluctuations of the tunable fiber laser were kept within  ±0.2 nm.

Full spectral optical modeling of quantum-dot-converted elements for light-emitting diodes considering reabsorption and reemission effect.

PubMed

Li, Jia-Sheng; Tang, Yong; Li, Zong-Tao; Cao, Kai; Yan, Cai-Man; Ding, Xin-Rui

2018-07-20

Quantum dots (QDs) have attracted significant attention in light-emitting diode (LED) illumination and display applications, owing to their high quantum yield and unique spectral properties. However, an effective optical model of quantum-dot-converted elements (QDCEs) for (LEDs) that entirely considers the reabsorption and reemission effect is lacking. This suppresses the design of QDCE structures and further investigation of light-extraction/conversion mechanisms in QDCEs. In this paper, we proposed a full spectral optical modeling method for QDCEs packaged in LEDs, entirely considering the reabsorption and reemission effect, and its results are compared with traditional models without reabsorption or reemission. The comparisons indicate that the QDCE absorption loss of QD emission light is a major factor decreasing the radiant efficacy of LEDs, which should be considered when designing QDCE structures. According to the measurements of fabricated LEDs, only calculation results that entirely consider reabsorption and reemission show good agreement with experimental radiant efficacy, spectra, and peak wavelength at the same down-conversion efficiency. Consequently, it is highly expected that QDCE will be modeled considering the reabsorption and reemission events. This study provides a simple and effective modeling method for QDCEs, which shows great potential for their structure designs and fundamental investigations.

Full spectral optical modeling of quantum-dot-converted elements for light-emitting diodes considering reabsorption and reemission effect

NASA Astrophysics Data System (ADS)

Li, Jia-Sheng; Tang, Yong; Li, Zong-Tao; Cao, Kai; Yan, Cai-Man; Ding, Xin-Rui

2018-07-01

Quantum dots (QDs) have attracted significant attention in light-emitting diode (LED) illumination and display applications, owing to their high quantum yield and unique spectral properties. However, an effective optical model of quantum-dot-converted elements (QDCEs) for (LEDs) that entirely considers the reabsorption and reemission effect is lacking. This suppresses the design of QDCE structures and further investigation of light-extraction/conversion mechanisms in QDCEs. In this paper, we proposed a full spectral optical modeling method for QDCEs packaged in LEDs, entirely considering the reabsorption and reemission effect, and its results are compared with traditional models without reabsorption or reemission. The comparisons indicate that the QDCE absorption loss of QD emission light is a major factor decreasing the radiant efficacy of LEDs, which should be considered when designing QDCE structures. According to the measurements of fabricated LEDs, only calculation results that entirely consider reabsorption and reemission show good agreement with experimental radiant efficacy, spectra, and peak wavelength at the same down-conversion efficiency. Consequently, it is highly expected that QDCE will be modeled considering the reabsorption and reemission events. This study provides a simple and effective modeling method for QDCEs, which shows great potential for their structure designs and fundamental investigations.

Optical fiber sources and transmission controls for multi-Tb/s systems

NASA Astrophysics Data System (ADS)

Nowak, George Adelbert

The accelerating demand for bandwidth capacity in backbone links of terrestrial communications systems is projected to exceed 1Tb/s by 2002. Lightwave carrier frequencies and fused-silica optical fibers provide the natural combination of high passband frequencies and low- loss medium to satisfy this evolving demand for bandwidth capacity. This thesis addresses three key technologies for enabling multi-Tb/s optical fiber communication systems. The first technology is a broadband source based on supercontinuum generation in optical fiber. Using a single modelocked laser with output pulsewidths of 0.5psec pulses, we generate in ~2m of dispersion-shifted fiber more that 200nm of spectral continuum in the vicinity of 1550nm that is flat to better than +/- 0.5 dB over more than 60nm. The short fiber length prevents degradation of timing jitter of the seed pulses and preserves coherence of the continuum by inhibiting environmental perturbations and mapping of random noise from the vicinity of the input pulse across the continuum. Through experiments and simulations, we find that the continuum characteristics result from 3rd order dispersion effects on higher-order soliton compression. We determine optimal fiber properties to provide desired continuum broadness and flatness for given input pulsewidth and energy conditions. The second technology is a novel delay-shifted nonlinear optical loop mirror (DS-NOLM) that performs a transmission control function by serving as an intensity filter and frequency compensator for <5psec soliton transmission systems. A theoretical and experimental study of the DS-NOLM as a transmission control element in a periodically amplified soliton transmission system is presented. We show that DS-NOLMs enable 4ps soliton transmission over 75km of standard dispersion fiber, with 25km spacing between amplifiers, by filtering the dispersive waves and compensating for Raman-induced soliton self-frequency shift. The third technology is all-fiber wavelength conversion employing induced modulational instability. We obtain wavelength conversion over 40nm with a peak conversion efficiency of 28dB using 600mW pump pulses in 720m of high-nonlinearity optical fiber. We show that the high- nonlinearity fiber enhances the phase-matching bandwidth as well as reducing the required fiber lengths and pump powers.

160-Gb/s all-optical phase-transparent wavelength conversion through cascaded SFG-DFG in a broadband linear-chirped PPLN waveguide.

PubMed

Lu, Guo-Wei; Shinada, Satoshi; Furukawa, Hideaki; Wada, Naoya; Miyazaki, Tetsuya; Ito, Hiromasa

2010-03-15

We experimentally demonstrated ultra-fast phase-transparent wavelength conversion using cascaded sum- and difference-frequency generation (cSFG-DFG) in linear-chirped periodically poled lithium niobate (PPLN). Error-free wavelength conversion of a 160-Gb/s return-to-zero differential phase-shift keying (RZ-DPSK) signal was successfully achieved. Thanks to the enhanced conversion bandwidth in the PPLN with linear-chirped periods, no optical equalizer was required to compensate the spectrum distortion after conversion, unlike a previous demonstration of 160-Gb/s RZ on-off keying (OOK) using fixed-period PPLN.

Micro Solar Cells with Concentration and Light Trapping Optics

NASA Astrophysics Data System (ADS)

Li, Lanfang; Breuckner, Eric; Corcoran, Christopher; Yao, Yuan; Xu, Lu; Nuzzo, Ralph

2013-03-01

Compared with conventional bulk plate semiconductor solar cells, micro solar cells provide opportunity for novel design geometry and provide test bed for light trapping at the device level as well as module level. Surface recombination, however, will have to be addressed properly as the much increased surface area due to the reduced dimension is more prominent in these devices than conventional solar cells. In this poster, we present experimental demonstration of silicon micro solar cells with concentration and light trapping optics. Silicon micro solar cell with optimized surface passivation and doping profile that exhibit high efficiency is demonstrated. Effective incorporation of high quantum yield fluorescent centers in the polymer matrix into which micro solar cell was encapsulated was investigated for luminescent solar concentration application. Micro-cell on a semi-transparent, nanopatterned reflector formed by soft-imprint lithography was investigated for near field effect related solar conversion performance enhancement. This work is supported by the DOE `Light-Material Interactions in Energy Conversion' Energy Frontier Research Center under grant DE-SC0001293

Cascade photonic integrated circuit architecture for electro-optic in-phase quadrature/single sideband modulation or frequency conversion.

PubMed

Hasan, Mehedi; Hall, Trevor

2015-11-01

A photonic integrated circuit architecture for implementing frequency upconversion is proposed. The circuit consists of a 1×2 splitter and 2×1 combiner interconnected by two stages of differentially driven phase modulators having 2×2 multimode interference coupler between the stages. A transfer matrix approach is used to model the operation of the architecture. The predictions of the model are validated by simulations performed using an industry standard software tool. The intrinsic conversion efficiency of the proposed design is improved by 6 dB over the alternative functionally equivalent circuit based on dual parallel Mach-Zehnder modulators known in the prior art. A two-tone analysis is presented to study the linearity of the proposed circuit, and a comparison is provided over the alternative. The proposed circuit is suitable for integration in any platform that offers linear electro-optic phase modulation such as LiNbO(3), silicon, III-V, or hybrid technology.

Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12)

PubMed Central

Li, Ji-Guang; Sakka, Yoshio

2015-01-01

This review article summarizes the recent achievements in stabilization of the metastable lattice of gadolinium aluminate garnet (Gd3Al5O12, GAG) and the related developments of advanced optical materials, including down-conversion phosphors, up-conversion phosphors, transparent ceramics, and single crystals. Whenever possible, the materials are compared with their better known YAG and LuAG counterparts to demonstrate the merits of the GAG host. It is shown that novel emission features and significantly improved luminescence can be attained for a number of phosphor systems with the more covalent GAG lattice and the efficient energy transfer from Gd3+ to the activator. Ce3+ doped GAG-based single crystals and transparent ceramics are also shown to simultaneously possess the advantages of high theoretical density, fast scintillation decay, and high light yields, and hold great potential as scintillators for a wide range of applications. The unresolved issues are also pointed out. PMID:27877750

Small signal analysis of four-wave mixing in InAs/GaAs quantum-dot semiconductor optical amplifiers

NASA Astrophysics Data System (ADS)

Ma, Shaozhen; Chen, Zhe; Dutta, Niloy K.

2009-02-01

A model to study four-wave mixing (FWM) wavelength conversion in InAs-GaAs quantum-dot semiconductor optical amplifier is proposed. Rate equations involving two QD states are solved to simulate the carrier density modulation in the system, results show that the existence of QD excited state contributes to the ultra fast recover time for single pulse response by serving as a carrier reservoir for the QD ground state, its speed limitations are also studied. Nondegenerate four-wave mixing process with small intensity modulation probe signal injected is simulated using this model, a set of coupled wave equations describing the evolution of all frequency components in the active region of QD-SOA are derived and solved numerically. Results show that better FWM conversion efficiency can be obtained compared with the regular bulk SOA, and the four-wave mixing bandwidth can exceed 1.5 THz when the detuning between pump and probe lights is 0.5 nm.

Recent progress in advanced optical materials based on gadolinium aluminate garnet (Gd3Al5O12)

NASA Astrophysics Data System (ADS)

Li, Ji-Guang; Sakka, Yoshio

2015-02-01

This review article summarizes the recent achievements in stabilization of the metastable lattice of gadolinium aluminate garnet (Gd3Al5O12, GAG) and the related developments of advanced optical materials, including down-conversion phosphors, up-conversion phosphors, transparent ceramics, and single crystals. Whenever possible, the materials are compared with their better known YAG and LuAG counterparts to demonstrate the merits of the GAG host. It is shown that novel emission features and significantly improved luminescence can be attained for a number of phosphor systems with the more covalent GAG lattice and the efficient energy transfer from Gd3+ to the activator. Ce3+ doped GAG-based single crystals and transparent ceramics are also shown to simultaneously possess the advantages of high theoretical density, fast scintillation decay, and high light yields, and hold great potential as scintillators for a wide range of applications. The unresolved issues are also pointed out.

Microlens array induced light absorption enhancement in polymer solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Yuqing; Elshobaki, Moneim; Ye, Zhuo

2013-01-24

Over the last decade, polymer solar cells (PSCs) have attracted a lot of attention and highest power conversion efficiencies (PCE) are now close to 10%. Here we employ an optical structure – the microlens array (MLA) – to increase light absorption inside the active layer, and PCE of PSCs increased even for optimized devices. Normal incident light rays are refracted at the MLA and travel longer optical paths inside the active layers. Two PSC systems – poly(3-hexylthiophene-2,5-diyl):(6,6)-phenyl C61 butyric acid methyl ester (P3HT:PCBM) and poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl]:(6,6)-phenyl C71 butyric acid methyl ester (PCDTBT:PC70BM) – were investigated. In the P3HT:PCBM system, MLA increasedmore » the absorption, absolute external quantum efficiency, and the PCE of an optimized device by [similar]4.3%. In the PCDTBT:PC70BM system, MLA increased the absorption, absolute external quantum efficiency, and PCE by more than 10%. In addition, simulations incorporating optical parameters of all structural layers were performed and they support the enhancement of absorption in the active layer with the assistance of MLA. Our results show that utilizing MLA is an effective strategy to further increase light absorption in PSCs, in which optical losses account for [similar]40% of total losses. MLA also does not pose materials processing challenges to the active layers since it is on the other side of the transparent substrate.« less

Polymer bulk heterojunction solar cells with PEDOT:PSS bilayer structure as hole extraction layer.

PubMed

Kim, Wanjung; Kim, Namhun; Kim, Jung Kyu; Park, Insun; Choi, Yeong Suk; Wang, Dong Hwan; Chae, Heeyeop; Park, Jong Hyeok

2013-06-01

A high current density obtained in a limited, nanometer-thick region is important for high efficiency polymer solar cells (PSCs). The conversion of incident photons to charge carriers only occurs in confined active layers; therefore, charge-carrier extraction from the active layer within the device by using solar light has an important impact on the current density and the related to power conversion efficiency. In this study, we observed a surprising result, that is, extracting the charge carrier generated in the active layer of a PSC device, with a thickness-controlled PEDOT:PSS bilayer that acted as a hole extraction layer (HEL), yielded a dramatically improved power conversion efficiency in two different model systems (P3HT:PC₆₀BM and PCDTBT:PC₇₀BM). To understand this phenomenon, we conducted optical strength simulation, photocurrent-voltage measurements, incident photon to charge carrier efficiency measurements, ultraviolet photoelectron spectroscopy, and AFM studies. The results revealed that approximately 60 nm was the optimum PEDOT:PSS bilayer HEL thickness in PSCs for producing the maximum power conversion efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electronic structures and enhanced optical properties of blue phosphorene/transition metal dichalcogenides van der Waals heterostructures.

PubMed

Peng, Qiong; Wang, Zhenyu; Sa, Baisheng; Wu, Bo; Sun, Zhimei

2016-08-24

As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices.

Design of a hybrid As₂S₃-Ti:LiNbO₃ optical waveguide for phase-matched difference frequency generation at mid-infrared.

PubMed

Wang, Xin; Madsen, Christi K

2014-11-03

Based on arsenic tri-sulfide films on titanium-diffused lithium niobate, we designed a hybrid optical waveguide for efficient mid-infrared emission by phase-matched difference frequency generation (DFG). The hybrid waveguide structure possesses a low-index magnesium fluoride buffer layer sandwiched between two high-index As(2)S(3) slabs, so that pump and signal waves are tightly confined by titanium-diffused waveguide while the DFG output idler wave at mid-infrared is confined by the whole hybrid waveguide structure. On a 1 mm-long hybrid waveguide pumped at 50 mW powers, a normalized power conversion efficiency of 20.52%W(-1)cm(-2) was theoretically predicted, which is the highest record for mid-infrared DFG waveguides based on lithium niobate crystal, to the best of our knowledge. Using a tunable near-infrared pump laser at 1.38-1.47 µm or a tunable signal laser at 1.95-2.15 µm, a broad mid-infrared tuning range from 4.0 µm to 4.9 µm can be achieved. Such hybrid optical waveguides are feasible for mid-infrared emission with mW powers and sub-nanometer linewidths.

A Photonic Crystal Laser from Solution Based Organo-Lead Iodide Perovskite Thin Films.

PubMed

Chen, Songtao; Roh, Kwangdong; Lee, Joonhee; Chong, Wee Kiang; Lu, Yao; Mathews, Nripan; Sum, Tze Chien; Nurmikko, Arto

2016-04-26

Perovskite semiconductors are actively investigated for high performance solar cells. Their large optical absorption coefficient and facile solution-based, low-temperature synthesis of thin films make perovskites also a candidate for light-emitting devices across the visible and near-infrared. Specific to their potential as optical gain medium for lasers, early work has demonstrated amplified spontaneous emission and lasing at attractively low thresholds of photoexcitation. Here, we take an important step toward practically usable perovskite lasers where a solution-processed thin film is embedded within a two-dimensional photonic crystal resonator. We demonstrate high degree of temporally and spatially coherent lasing whereby well-defined directional emission is achieved near 788 nm wavelength at optical pumping energy density threshold of 68.5 ± 3.0 μJ/cm(2). The measured power conversion efficiency and differential quantum efficiency of the perovskite photonic crystal laser are 13.8 ± 0.8% and 35.8 ± 5.4%, respectively. Importantly, our approach enables scalability of the thin film lasers to a two-dimensional multielement pixelated array of microlasers which we demonstrate as a proof-of-concept for possible projection display applications.

Modulation and multiplexing in ultra-broadband photonic internet: Part II

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2011-06-01

In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

Ultra-broadband photonic internet

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2011-06-01

In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

Modulation and multiplexing in ultra-broadband photonic internet: Part I

NASA Astrophysics Data System (ADS)

Romaniuk, Ryszard S.

2011-06-01

In this paper, there is presented a review of our today's understanding of the ultimately broadband photonic Internet. A simple calculation is presented showing the estimate of the throughput of the core photonic network branches. Optoelectronic components, circuits, systems and signals, together with analogous electronic entities and common software layers, are building blocks of the contemporary Internet. Participation of photonics in development of the physical layer in the future Internet will probably increase. The photonics leads now to a better usage of the available bandwidth (increase of the spectral efficiency measured in Bit/s/Hz), increase in the transmission rate (from Gbps, via Tbps up to probably Pbps), increase in the transmission distance without signal regeneration (in distortion compensated active optical cables), increase in energy/power efficiency measured in W/Gbps, etc. Photonics may lead, in the future, to fully transparent optical networks and, thus, to essential increase in bandwidth and network reliability. It is expected that photonics (with biochemistry, electronics and mechatronics) may build psychological and physiological interface for humans to the future global network. The following optical signal multiplexing methods were considered, which are possible without O/E/O conversion: TDM-OTDM, FDM-CO-OFDM, OCDM-OCDMA, WDM-DWDM.

Polymer taper bridge for silicon waveguide to single mode waveguide coupling

NASA Astrophysics Data System (ADS)

Kruse, Kevin; Middlebrook, Christopher T.

2016-03-01

Coupling of optical power from high-density silicon waveguides to silica optical fibers for signal routing can incur high losses and often requires complex end-face preparation/processing. Novel coupling device taper structures are proposed for low coupling loss between silicon photonic waveguides and single mode fibers are proposed and devices are fabricated and measured in terms of performance. Theoretical mode conversion models for waveguide tapers are derived for optimal device structure design and performance. Commercially viable vertical and multi-layer taper designs using polymer waveguide materials are proposed as innovative, cost-efficient, and mass-manufacturable optical coupling devices. The coupling efficiency for both designs is determined to evaluate optimal device dimensions and alignment tolerances with both silicon rib waveguides and silicon nanowire waveguides. Propagation loss as a function of waveguide roughness and metallic loss are determined and correlated to waveguide dimensions to obtain total insertion loss for the proposed taper designs. Multi-layer tapers on gold-sputtered substrates are fabricated through photolithography as proof-of-concept devices and evaluated for device loss optimization. Tapered waveguide coupling loss with Si WGs (2.74 dB) was experimentally measured with high correlation to theoretical results.

High-power, continuous-wave, tunable mid-IR, higher-order vortex beam optical parametric oscillator

NASA Astrophysics Data System (ADS)

Aadhi, A.; Sharma, Varun; Samanta, G. K.

2018-05-01

We report on a novel experimental scheme to generate continuous-wave (cw), high power, and higher-order optical vortices tunable across mid-IR wavelength range. Using cw, two-crystal, singly resonant optical parametric oscillator (T-SRO) and pumping one of the crystals with Gaussian beam and the other crystal with optical vortices of orders, lp = 1 to 6, we have directly transferred the vortices at near-IR to the mid-IR wavelength range. The idler vortices of orders, li = 1 to 6, are tunable across 2276-3576 nm with a maximum output power of 6.8 W at order of, li = 1, for the pump power of 25 W corresponding to a near-IR vortex to mid-IR vortex conversion efficiency as high as 27.2%. Unlike the SROs generating optical vortices restricted to lower orders due to the elevated operation threshold with pump vortex orders, here, the coherent energy coupling between the resonant signals of the crystals of T-SRO facilitates the transfer of pump vortex of any order to the idler wavelength without stringent operation threshold condition. The generic experimental scheme can be used in any wavelength range across the electromagnetic spectrum and in all time scales from cw to ultrafast regime.

Reconfigurable optical-to-optical frequency conversion method and apparatus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zortman, William A.; Lentine, Anthony L.

A photonic device is provided for impressing a modulation pattern on an optical carrier. The device includes a unit in which a photodetector and an optical microresonator are monolithically integrated. The device further includes an optical waveguide evanescently coupled to the optical microresonator and having at least an upstream portion configured to carry at least one optical carrier toward the microresonator. The optical microresonator is tunable so as to resonate with the optical carrier frequency. The optical microresonator and the photodetector are mutually coupled such that in operation, charge carriers photogenerated in the photodetector are injected into the microresonator, wheremore » the photocurrent changes the resonant conditions. In some embodiments the device is operable as an optical-to-optical frequency converter. In other embodiments the device is operable as an oscillator.« less