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Photonics, Volume 2, Issue 4 (December 2015), Pages 1027-1201

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Research

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Open AccessArticle Assessment of Gate Width Size on Lifetime-Based Förster Resonance Energy Transfer Parameter Estimation
Photonics 2015, 2(4), 1027-1042; doi:10.3390/photonics2041027
Received: 28 August 2015 / Revised: 22 September 2015 / Accepted: 23 September 2015 / Published: 28 September 2015
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Abstract
Förster Resonance Energy Transfer (FRET) enables the observation of interactions at the nanoscale level through the use of fluorescence optical imaging techniques. In FRET, fluorescence lifetime imaging can be used to quantify the fluorescence lifetime changes of the donor molecule, which are associated
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Förster Resonance Energy Transfer (FRET) enables the observation of interactions at the nanoscale level through the use of fluorescence optical imaging techniques. In FRET, fluorescence lifetime imaging can be used to quantify the fluorescence lifetime changes of the donor molecule, which are associated with proximity between acceptor and donor molecules. Among the FRET parameters derived from fluorescence lifetime imaging, the percentage of donor that interacts with the acceptor (in proximity) can be estimated via model-based fitting. However, estimation of the lifetime parameters can be affected by the acquisition parameters such as the temporal characteristics of the imaging system. Herein, we investigate the effect of various gate widths on the accuracy of estimation of FRET parameters with focus on the near-infrared spectral window. Experiments were performed in silico, in vitro, and in vivo with gate width sizes ranging from 300 ps to 1000 ps in intervals of 100 ps. For all cases, the FRET parameters were retrieved accurately and the imaging acquisition time was decreased three-fold. These results indicate that increasing the gate width up to 1000 ps still allows for accurate quantification of FRET interactions even in the case of short lifetimes such as those encountered with near-infrared FRET pairs. Full article
Open AccessArticle Material Exchange Property of Organo Lead Halide Perovskite with Hole-Transporting Materials
Photonics 2015, 2(4), 1043-1053; doi:10.3390/photonics2041043
Received: 4 September 2015 / Revised: 24 September 2015 / Accepted: 28 September 2015 / Published: 2 October 2015
Cited by 4 | PDF Full-text (783 KB) | HTML Full-text | XML Full-text
Abstract
Using X-ray diffraction (XRD), it was confirmed that the deposition of hole-transporting materials (HTM) on a CH3NH3PbI3 perovskite layer changed the CH3NH3PbI3 perovskite crystal, which was due to the material exchanging phenomena between
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Using X-ray diffraction (XRD), it was confirmed that the deposition of hole-transporting materials (HTM) on a CH3NH3PbI3 perovskite layer changed the CH3NH3PbI3 perovskite crystal, which was due to the material exchanging phenomena between the CH3NH3PbI3 perovskite and HTM layers. The solvent for HTM also changed the perovskite crystal. In order to suppress the crystal change, doping by chloride ion, bromide ion and 5-aminovaleric acid was attempted. However, the doping was unable to stabilize the perovskite crystal against HTM deposition. It can be concluded that the CH3NH3PbI3 perovskite crystal is too soft and flexible to stabilize against HTM deposition. Full article
(This article belongs to the Special Issue Perovskite Photovoltaic and Optoelectronics)
Open AccessArticle Oxide-Free Bonding of III-V-Based Material on Silicon and Nano-Structuration of the Hybrid Waveguide for Advanced Optical Functions
Photonics 2015, 2(4), 1054-1064; doi:10.3390/photonics2041054
Received: 30 September 2015 / Revised: 22 October 2015 / Accepted: 26 October 2015 / Published: 29 October 2015
Cited by 1 | PDF Full-text (448 KB) | HTML Full-text | XML Full-text
Abstract
Oxide-free bonding of III-V-based materials for integrated optics is demonstrated on both planar Silicon (Si) surfaces and nanostructured ones, using Silicon on Isolator (SOI) or Si substrates. The hybrid interface is characterized electrically and mechanically. A hybrid InP-on-SOI waveguide, including a bi-periodic nano
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Oxide-free bonding of III-V-based materials for integrated optics is demonstrated on both planar Silicon (Si) surfaces and nanostructured ones, using Silicon on Isolator (SOI) or Si substrates. The hybrid interface is characterized electrically and mechanically. A hybrid InP-on-SOI waveguide, including a bi-periodic nano structuration of the silicon guiding layer is demonstrated to provide wavelength selective transmission. Such an oxide-free interface associated with the nanostructured design of the guiding geometry has great potential for both electrical and optical operation of improved hybrid devices. Full article
Open AccessArticle A Thermally Tunable 1 × 4 Channel Wavelength Demultiplexer Designed on a Low-Loss Si3N4 Waveguide Platform
Photonics 2015, 2(4), 1065-1080; doi:10.3390/photonics2041065
Received: 4 October 2015 / Revised: 31 October 2015 / Accepted: 3 November 2015 / Published: 6 November 2015
Cited by 2 | PDF Full-text (715 KB) | HTML Full-text | XML Full-text
Abstract
A thermally tunable 1 × 4 channel optical demultiplexer was designed using an ultra low-loss Si3N4 (propagation loss ~3.1 dB/m) waveguide. The demultiplexer has three 2 × 2 Mach-Zehnder interferometers (MZI), where each of the MZI contains two 2 ×
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A thermally tunable 1 × 4 channel optical demultiplexer was designed using an ultra low-loss Si3N4 (propagation loss ~3.1 dB/m) waveguide. The demultiplexer has three 2 × 2 Mach-Zehnder interferometers (MZI), where each of the MZI contains two 2 × 2 general interference based multimode interference (MMI) couplers. The MMI couplers exhibit −3.3 dB to −3.7 dB power division ratios over a 50 nm wavelength range from 1530 nm to 1580 nm. The chrome-based (Cr) heaters placed on the delay arms of the MZI filters enable thermal tuning to control the optical phase shift in the MZI delay arms. This facilitates achieving moderately low crosstalk (14.5 dB) between the adjacent channels. The optical insertion loss of the demultiplexer per channel is between 1.5 dB to 2.2 dB over the 1550 nm to 1565 nm wavelength range. Error free performance (BER of 10−12) is obtained for all four 40 Gb/s data rate channels. The optical demultiplexer is an important tool towards building photonic integrated circuits with complex optical signal processing functionalities in the low-loss Si3N4 waveguide platform. Full article
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Open AccessArticle Transient Response of Organo-Metal-Halide Solar Cells Analyzed by Time-Resolved Current-Voltage Measurements
Photonics 2015, 2(4), 1101-1115; doi:10.3390/photonics2041101
Received: 3 November 2015 / Revised: 18 November 2015 / Accepted: 19 November 2015 / Published: 24 November 2015
Cited by 4 | PDF Full-text (924 KB) | HTML Full-text | XML Full-text
Abstract
The determination of the power conversion efficiency of solar cells based on organo-metal-halides is subject to an ongoing debate. As solar cell devices may exhibit very slow transient response, current-voltage scans in different directions may not be congruent, which is an effect often
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The determination of the power conversion efficiency of solar cells based on organo-metal-halides is subject to an ongoing debate. As solar cell devices may exhibit very slow transient response, current-voltage scans in different directions may not be congruent, which is an effect often referred to as hysteresis. We here discuss time-resolved current-voltage measurements as a means to evaluate appropriate delay times (voltage settling times) to be used in current-voltage measurements of solar cells. Furthermore, this method allows the analysis of transient current response to extract time constants that can be used to compare characteristic differences between devices of varying architecture types, selective contacts and changes in devices due to storage or degradation conditions. Full article
(This article belongs to the Special Issue Perovskite Photovoltaic and Optoelectronics)
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Open AccessArticle Double-Slot Hybrid Plasmonic Ring Resonator Used for Optical Sensors and Modulators
Photonics 2015, 2(4), 1116-1130; doi:10.3390/photonics2041116
Received: 15 October 2015 / Revised: 11 November 2015 / Accepted: 19 November 2015 / Published: 25 November 2015
Cited by 6 | PDF Full-text (968 KB) | HTML Full-text | XML Full-text
Abstract
An ultra-high sensitivity double-slot hybrid plasmonic (DSHP) ring resonator, used for optical sensors and modulators, is developed. Due to high index contrast, as well as plasmonic enhancement, a considerable part of the optical energy is concentrated in the narrow slots between Si and
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An ultra-high sensitivity double-slot hybrid plasmonic (DSHP) ring resonator, used for optical sensors and modulators, is developed. Due to high index contrast, as well as plasmonic enhancement, a considerable part of the optical energy is concentrated in the narrow slots between Si and plasmonic materials (silver is used in this paper), which leads to high sensitivity to the infiltrating materials. By partial opening of the outer plasmonic circular sheet of the DSHP ring, a conventional side-coupled silicon on insulator (SOI) bus waveguide can be used. Experimental results demonstrate ultra-high sensitivity (687.5 nm/RIU) of the developed DSHP ring resonator, which is about five-times higher than for the conventional Si ring with the same geometry. Further discussions show that a very low detection limit (5.37 × 10−6 RIU) can be achieved after loaded Q factor modifications. In addition, the plasmonic metal structures offer also the way to process optical and electronic signals along the same hybrid plasmonic circuits with small capacitance (~0.275 fF) and large electric field, which leads to possible applications in compact high-efficiency electro-optic modulators, where no extra electrodes for electronic signals are required. Full article
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Open AccessArticle Optical Characteristics of a Multichannel Hybrid Integrated Light Source for Ultra-High-Bandwidth Optical Interconnections
Photonics 2015, 2(4), 1131-1138; doi:10.3390/photonics2041131
Received: 31 October 2015 / Revised: 18 November 2015 / Accepted: 19 November 2015 / Published: 25 November 2015
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Abstract
The optical characteristics of a multi-channel hybrid integrated light source were described for an optical interconnection with a bandwidth of over 10 Tbit/s. The power uniformity of the relative intensity of a 1000-channel light source was shown, and the minimum standard deviation s
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The optical characteristics of a multi-channel hybrid integrated light source were described for an optical interconnection with a bandwidth of over 10 Tbit/s. The power uniformity of the relative intensity of a 1000-channel light source was shown, and the minimum standard deviation s of the optical power of the 200 output ports at each 25-channel laser diode (LD) array was estimated to be 0.49 dB. This hybrid integrated light source is expected to be easily adaptable to a photonics-electronics convergence system for ultra-high-bandwidth interchip interconnections. Full article
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Open AccessArticle InP-Based Waveguide Triple Transit Region Photodiodes for Hybrid Integration with Passive Optical Silica Waveguides
Photonics 2015, 2(4), 1152-1163; doi:10.3390/photonics2041152
Received: 15 October 2015 / Revised: 24 November 2015 / Accepted: 3 December 2015 / Published: 7 December 2015
Cited by 4 | PDF Full-text (584 KB) | HTML Full-text | XML Full-text
Abstract
We report on a novel InP-based 1.55 μm waveguide triple transit region photodiode (TTR-PD) structure for hybrid integration with passive optical silica waveguides. Using the beam propagation method, numerical analyses reveal that, for evanescent optical coupling between a passive silica waveguide and the
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We report on a novel InP-based 1.55 μm waveguide triple transit region photodiode (TTR-PD) structure for hybrid integration with passive optical silica waveguides. Using the beam propagation method, numerical analyses reveal that, for evanescent optical coupling between a passive silica waveguide and the InP-based waveguide TTR-PD, a coupling efficiency of about 90% can be obtained. In addition to that, an absorption of about 50% is simulated within a TTR-PD length of 30 µm. For fabricated TTR-PD chips, a polarization dependent loss (PDL) of less than 0.9 dB is achieved within the complete optical C-band. At the operational wavelength of 1.55 µm, a reasonable PDL of 0.73 dB is measured. The DC responsivity and the RF responsivity are achieved on the order of 0.52 A/W and 0.24 A/W, respectively. Further, a 3 dB bandwidth of 132 GHz is experimentally demonstrated and high output-power levels exceeding 0 dBm are obtained. Even at the 3 dB cut-off frequency, no saturation effects occur at a photocurrent of 15.5 mA and an RF output power of −4.6 dBm is achieved. In addition to the numerical and experimental achievements, we propose a scheme for a hybrid-integrated InP/silicon-based photonic millimeter wave transmitter. Full article
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Review

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Open AccessReview Transfer Printed Nanomembranes for Heterogeneously Integrated Membrane Photonics
Photonics 2015, 2(4), 1081-1100; doi:10.3390/photonics2041081
Received: 30 October 2015 / Revised: 9 November 2015 / Accepted: 11 November 2015 / Published: 13 November 2015
Cited by 2 | PDF Full-text (1470 KB) | HTML Full-text | XML Full-text
Abstract
Heterogeneous crystalline semiconductor nanomembrane (NM) integration is investigated for single-layer and double-layer Silicon (Si) NM photonics, III-V/Si NM lasers, and graphene/Si NM total absorption devices. Both homogeneous and heterogeneous integration are realized by the versatile transfer printing technique. The performance of these integrated
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Heterogeneous crystalline semiconductor nanomembrane (NM) integration is investigated for single-layer and double-layer Silicon (Si) NM photonics, III-V/Si NM lasers, and graphene/Si NM total absorption devices. Both homogeneous and heterogeneous integration are realized by the versatile transfer printing technique. The performance of these integrated membrane devices shows, not only intact optical and electrical characteristics as their bulk counterparts, but also the unique light and matter interactions, such as Fano resonance, slow light, and critical coupling in photonic crystal cavities. Such a heterogeneous integration approach offers tremendous practical application potentials on unconventional, Si CMOS compatible, and high performance optoelectronic systems. Full article
Open AccessReview Stability Issues on Perovskite Solar Cells
Photonics 2015, 2(4), 1139-1151; doi:10.3390/photonics2041139
Received: 3 November 2015 / Revised: 24 November 2015 / Accepted: 25 November 2015 / Published: 27 November 2015
Cited by 30 | PDF Full-text (612 KB) | HTML Full-text | XML Full-text
Abstract
Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3) and formamidinium lead iodide (HC(NH2)2PbI3) show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite
[...] Read more.
Organo lead halide perovskite materials like methylammonium lead iodide (CH3NH3PbI3) and formamidinium lead iodide (HC(NH2)2PbI3) show superb opto-electronic properties. Based on these perovskite light absorbers, power conversion efficiencies of the perovskite solar cells employing hole transporting layers have increased from 9.7% to 20.1% within just three years. Thus, it is apparent that perovskite solar cell is a promising next generation photovoltaic technology. However, the unstable nature of perovskite was observed when exposing it to continuous illumination, moisture and high temperature, impeding the commercial development in the long run and thus becoming the main issue that needs to be solved urgently. Here, we discuss the factors affecting instability of perovskite and give some perspectives about further enhancement of stability of perovskite solar cell. Full article
(This article belongs to the Special Issue Perovskite Photovoltaic and Optoelectronics)
Open AccessReview Low-Temperature Bonding for Silicon-Based Micro-Optical Systems
Photonics 2015, 2(4), 1164-1201; doi:10.3390/photonics2041164
Received: 7 November 2015 / Revised: 10 December 2015 / Accepted: 11 December 2015 / Published: 15 December 2015
Cited by 2 | PDF Full-text (1368 KB) | HTML Full-text | XML Full-text
Abstract
Silicon-based integrated systems are actively pursued for sensing and imaging applications. A major challenge to realize highly sensitive systems is the integration of electronic, optical, mechanical and fluidic, all on a common platform. Further, the interface quality between the tiny optoelectronic structures and
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Silicon-based integrated systems are actively pursued for sensing and imaging applications. A major challenge to realize highly sensitive systems is the integration of electronic, optical, mechanical and fluidic, all on a common platform. Further, the interface quality between the tiny optoelectronic structures and the substrate for alignment and coupling of the signals significantly impacts the system’s performance. These systems also have to be low-cost, densely integrated and compatible with current and future mainstream technologies for electronic-photonic integration. To address these issues, proper selection of the fabrication, integration and assembly technologies is needed. In this paper, wafer level bonding with advanced features such as surface activation and passive alignment for vertical electrical interconnections are identified as candidate technologies to integrate different electronics, optical and photonic components. Surface activated bonding, superior to other assembly methods, enables low-temperature nanoscaled component integration with high alignment accuracy, low electrical loss and high transparency of the interface. These features are preferred for the hybrid integration of silicon-based micro-opto-electronic systems. In future, new materials and assembly technologies may emerge to enhance the performance of these micro systems and reduce their cost. The article is a detailed review of bonding techniques for electronic, optical and photonic components in silicon-based systems. Full article
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