| 1. |
- Aghaeipour, Mahtab, et al.
(författare)
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Considering symmetry properties of inp nanowire/light incidence systems to gain broadband absorption
- 2017
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Ingår i: IEEE Photonics Journal. - Piscataway : IEEE. - 1943-0655. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Geometrically designed III-V nanowire arrays are promising candidates for disruptive optoelectronics due to the possibility of obtaining a strongly enhanced absorption resulting from nanophotonic resonance effects. With normally incident light on such vertical nanowire arrays, the absorption spectra exhibit peaks that originate from excitation of HE1m waveguide modes in the constituent nanowires. However, the absorption spectra typically show dips between the absorption peaks. Conventionally, such weak absorption has been counteracted by either making the nanowires longer or by decreasing the pitch of the array, both alternatives effectively increasing the volume of absorbing material in the array. Here, we first study two approaches for compensating the absorption dips by exciting additional Mie resonances: 1) oblique light incidence on vertical InP nanowire arrays and 2) normal light incidence on inclined InP nanowire arrays. We then show that branched nanowires offer a novel route to achieve broadband absorption by taking advantage of simultaneous excitations of Mie resonances in the branches and guided HE1m modes in the stem. Finite element method calculations show that the absorption efficiency is enhanced from 0.72 for vertical nanowires to 0.78 for branched nanowires under normal light incidence. Our work provides new insight for the development of novel efficient photovoltaics with high efficiency and reduced active material volume.
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| 2. |
- Alkabani, Yousra, 1981-, et al.
(författare)
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OE-CAM : A Hybrid Opto-Electronic Content Addressable Memory
- 2020
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Ingår i: IEEE Photonics Journal. - Piscataway, NJ : IEEE. - 1943-0655. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- A content addressable memory (CAM) is a type of memory that implements a parallel search engine at its core. A CAM takes as an input a value and outputs the address where this value is stored in case of a match. CAMs are used in a wide range of applications including networking, cashing, neuromorphic associative memories, multimedia, and data analytics. Here, we introduce a novel opto-electronic CAM (OE-CAM) utilizing the integrated silicon photonic platform. In our approach, we explore the performance of an experimental OE-CAM and verify the efficiency of the device at 25 Gbit/s while maintaining the bit integrity under noise conditions. We show that OE-CAM enables a) two orders of magnitude faster search functionality resulting in b) a five orders of magnitude lower power-delay-product compared to CAMs implementations based on other emerging technologies. This remarkable performance potential is achieved by utilizing i) a high parallelism of wavelength-division-multiplexing in the optical domain, combined with ii) 10's of GHz-fast opto-electronic components, packaged in iii) integrated photonics for 10-100's ps-short communication delays. We further verify the upper optical input power limit of this OE-CAM to be given by parasitic nonlinearities inside the silicon waveguides, and the minimal detectable optical power at the back-end photoreceiver's responsivity given channel noise. Such energy-efficient and short-delay OE-CAMs could become a key component of functional photonic-augmented ASICS, co-processors, or smart sensors. © IEEE
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| 3. |
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| 4. |
- Borgentun, Carl, 1979, et al.
(författare)
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Widely Tunable High-Power Semiconductor Disk Laser With Nonresonant AR-Assisted Gain Element on Diamond Heat Spreader
- 2011
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 3:5, s. 946-953
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Tidskriftsartikel (refereegranskat)abstract
- We report on an optically pumped semiconductor disk laser with a wide wavelength tuning range and a high peak output power. This was achieved using a combination of efficient thermal management and a broadband gain element (GE) with carefully engineered spectral gain characteristics. For heat removal, a flip-chip bonding scheme on diamond was used. To provide high active mirror reflectance over a large wavelength region, the layered structure of the GE formed a nonresonant subcavity assisted by an antireflective structure. A peak output power of more than 7.5 W and a tuning range of 32 nm around the center wavelength of 995 nm were obtained.
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| 5. |
- Brydegaard, Mikkel, et al.
(författare)
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Photobleaching-Insensitive Fluorescence Diagnostics in Skin and Brain Tissue
- 2011
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers. - 1943-0655. ; 3:3, s. 407-421
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate the possibility of using accurate prediction models for the prediction of protoporphyrin bleaching dynamics to achieve photobleaching-insensitive methods to improve the evaluation of data in an existing clinical fluorescence-guided resection technique. To simulate the scenario, measurements were carried out in vivo on skin of healthy volunteers using a compact fiber-based fluorescence spectroscopy system. We have developed an effective method for the parameterization of sequences of bleaching spectra. We analyze convergence and decay rates with respect to initial conditions and excitation irradiance. We also discuss the consequences and the potential for bleaching-insensitive measurements and their applicability in a few examples from in vivo open brain surgery.
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| 6. |
- Caut, Alexander, 1994, et al.
(författare)
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Polarization-insensitive silicon nitride photonic receiver at 1 μm for optical interconnects
- 2024
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 16:3, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- This paper demonstrates with FDTD simulations a silicon nitride polarization independent coarse wavelength division multiplexing (CWDM) receiver platform based on square waveguides for optical interconnects at 1 μm. Here, the channel spacing of the demultiplexers is much smaller than standard CWDM systems (25 nm) and is set to 8 nm. To avoid high waveguide propagation and radiation losses, several waveguide dimensions were considered. The 450 nm (width) x 450 nm (height) waveguide presented a good tradeoff between low loss and single-mode behavior and was therefore selected. The demultiplexer has a simulated polarization dependence on the waveguide's width variations of 0.17 nm/nm. In addition, we present edge coupler designs with coupling loss within 2.5 dB for TE and TM polarization.
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| 7. |
- Caut, Alexander, 1994, et al.
(författare)
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Polarization-Insensitive Silicon Nitride Photonic Receiver Based on Thin Waveguides for Optical Interconnects At 1 μm
- 2024
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 16:2, s. 1-7
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Tidskriftsartikel (refereegranskat)abstract
- This paper demonstrates with simulations two polarization independent wavelength division multiplexing receiver platforms based on thin silicon nitride waveguides for optical interconnects at 1 μm. The chosen waveguide base geometry (width = 900 nm × height = 160 nm) is a good tradeoff between mode confinement and propagation loss. We first propose a design using a polarization splitter with an 1×4 demultiplexer based on an arrayed waveguide grating (AWG). This receiver has a reduced size and requires only one etching step. We later propose another simplified receiver design using a polarization splitter-rotator with two identical 1×4 demultiplexers based on cascaded Mach-Zehnder interferometers. The rotator is based on a thicker waveguide (width = 500 nm × height = 400 nm) and is partially etched to rotate the electric field by 90°. Thus, it requires the use of mode size converters at the in/output ports. To keep the fabrication complexity as low as possible for the second design, we limited ourselves to only two etching steps. Therefore, the thickness of the slab of the mode converters and of the rotator is the same as for the main 900 nm (wide) × 160 nm (thick) waveguide. The simulated extinction ratio of the polarization splitter at 1035 nm is 18 dB and the calculated TM-TE and TE-TM polarization conversion efficiency of the polarization rotator at 1035 nm is 99.9%.
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| 8. |
- Chen, Hongzhi, et al.
(författare)
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Terahertz Polarization Splitters Based on Total and Partial Coupling in Dual Slotted Core Polymer Fiber : Comparison and Analysis
- 2017
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 9:3
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Tidskriftsartikel (refereegranskat)abstract
- Two terahertz (THz) polarization splitters based on dual slotted core polymer fiber are proposed and numerically investigated. The splitter structures are based on dual cores composed of subwavelength-scale air slots that are independently suspended within the fiber, which not only allows for single-mode propagation for the two orthogonal polarization modes with low absorption losses but enables them to couple with each other as well. Polarization splitters based on both symmetric and asymmetric dual slotted core structures, respectively, based on total and partial coupling are proposed and analyzed. The transmission modes, splitting lengths, and pertinent performance parameters of the two polarization splitters are investigated and numerically analyzed at a center-frequency of 1.0 THz. Comparisons of the two splitters with similar structural parameters are also carried out, which shows a comparably short splitting length of similar to 1 cm and an ultra-low transmission loss of 0.4 dB with the asymmetric structure having a broader bandwidth and better extinction ratios.
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| 9. |
- da Silva, Edson P., et al.
(författare)
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Combined Optical and Electrical Spectrum Shaping for High-Baud-Rate Nyquist-WDM Transceivers
- 2016
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- We discuss the benefits and limitations of optical time-division multiplexing (OTDM) techniques based on the optical generation of a periodic train of sinc pulses for wavelength-division multiplexing (WDM) transmission at high baud rates. It is shown how the modulated OTDM spectrum bandwidth is related to the optical comb parameters and the pulse shaping of the modulating waveforms in the electrical domain. Such dependence may result in broadening of the modulated spectra, which can degrade the performance of Nyquist-WDM systems due to interchannel crosstalk penalties. However, it is shown and experimentally demonstrated that the same technique of optical pulse train generation can be allied with digital pulse shaping to improve the confinement of the modulated spectrum toward the Nyquist limit independently of the number of OTDM tributaries used. To investigate the benefits of the proposed approach, we demonstrate the first WDM Nyquist-OTDM signal generation based on the periodic train of sinc pulses and electrical spectrum shaping. Straight line transmission of five 112.5-Gbd Nyquist-OTDM dual-polarization quadrature phase-shift keying (QPSK) channels is demonstrated over a dispersion uncompensated link up to 640 km, with full-field coherent detection at the receiver. It is shown that such a design strategy effectively improves the spectral confinement of the modulated OTDM signal, providing a minimum intercarrier crosstalk penalty of 1.5 dB in baud-rate-spaced Nyquist-WDM systems.
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| 10. |
- Du, Ji, et al.
(författare)
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A Comprehensive Performance Comparison of DFT-S DMT and QAM-DMT in UOWC System in Different Water Environments
- 2021
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 13:1
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we experimentally demonstrate a 450-nm laser underwater optical wireless transmission system, in which a comprehensive investigation is made to show the significant performance improvement of the discrete Fourier transform spread discrete multi-tone (DFT-S DMT) as compared to the conventional quadrature amplitude modulation discrete multi-tone (QAM-DMT) modulation. DFT-S DMT outperforms QAM-DMT in terms of bit error rate (BER) performance due to low peak-to-average-power ratio (PAPR) and capability of counteracting high frequency fading in a band-limited underwater optical wireless communication (UOWC) system. In order to avoid signal-to-noise-ratio (SNR) degradation at fringe subcarriers, several zeros are padded at the edge of each block before DFT-S operation. The experimental results show the superiority of DFT-S DMT compared with QAM-DMT in different water environments, including turbidities, bubbles, and water flow. Data rates of similar to 16.16 Gbps and similar to 13.96 Gbps at a BER of 3.8 x 10(-3) are achieved by 16-QAM DFT-S DMT and 16-QAM-DMT over a 5-m water channel, respectively, which indicates that capacity enhancement of similar to 2.2 Gbps is obtained by the DFT-S DMT. Meanwhile, over 3-dB receiver sensitivity improvement can always be achieved by the DFT-S DMT at the tested underwater transmission distances. Combined with adaptive bit-power loading, 20.04 Gbps over a 5-m "clear ocean" channel transmission with a single laser diode (LD) is demonstrated. For a 35-m water link, the distance-data rate product reaches 498.4 Gbps*m. To the best of our knowledge, both the data rate and distance-data rate product are the largest among all the results reported for a single visible LD. Aimed at high-speed deep ocean applications, the studies are promising for future UOWC research.
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| 11. |
- Du, Kaikai, et al.
(författare)
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Wavelength and Thermal Distribution Selectable Microbolometers Based on Metamaterial Absorbers
- 2015
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 7:3
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Tidskriftsartikel (refereegranskat)abstract
- An uncooled microbolometer based on metamaterial absorbers is investigated. The absorption peak reaches 90%, and the peak wavelength can be tailored from 2.4 to 10.2 mu m with corresponding bandwidth varying from 0.5 to 1.5 mu m by tuning the geometric parameters of the absorbers, covering two atmosphere windows (3-5 mu m and 8-14 mu m). The thermal distribution in the microbolometer can be adjusted to realize a strong thermal response. In the given situation with a pixel size of 25.07 mu m, the temperature response of the detector reaches 1.3 K. The microbolometer can be potentially used in thermal imaging at selected wavelengths in the mid-infrared and far-infrared regimes.
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| 12. |
- Ebadi, Seyed Morteza, et al.
(författare)
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A Multipurpose and Highly-Compact Plasmonic Filter based on Metal-Insulator-Metal Waveguides
- 2020
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 12:3
-
Tidskriftsartikel (refereegranskat)abstract
- A multipurpose and ultra-compact nanoplasmonic wavelength filter based on stub structure in a metal-insulator-metal (MIM) waveguide is suggested and numerically investigated. A novel approach of connecting two stepped-like apertures to both input and output ports is applied to form Fabry-Perot (FP) cavities, which enabled the structure to act as a dual band-pass filter at wavelengths 1310 nm and 1550 nm. It is shown that the variation in cavities’ length allows to realize a long-wavelength cutoff filter, and cutoff wavelength can be easily tuned by adjusting the length of the cavities. Furthermore, it is revealed that increasing the gap between the stepped-like apertures and the cavities provides a triple band-pass at telecom wavelengths, e.g. 1267.5nm, 1414.19 nm, and 1644.7 nm. The tunable broadband high-pass wavelength filter is then achieved while the lengths of stepped-like apertures and stub resonators are set to be identical. Finally, a tunable nearly perfect absorber can be obtained by varying the width of stub resonators. Therefore, because of functionality, size, as well as efficiency the proposed plasmonic filter may greatly contribute to miniaturization of next generation of photonic integrated circuits (PICs), and find applications in on-chip integration and wavelength-division multiplexing (WDM) in optical communication systems.
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| 13. |
- Elshaari, Ali W., et al.
(författare)
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Thermo-Optic Characterization of Silicon Nitride Resonators for Cryogenic Photonic Circuits
- 2016
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Ingår i: IEEE Photonics Journal. - : IEEE. - 1943-0655. ; 8:3
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, we characterize the Thermo-optic properties of silicon nitride ring resonators between 18 and 300 K. The Thermo-optic coefficients of the silicon nitride core and the oxide cladding are measured by studying the temperature dependence of the resonance wavelengths. The resonant modes show low temperature dependence at cryogenic temperatures and higher dependence as the temperature increases. We find the Thermo-optic coefficients of PECVD silicon nitride and silicon oxide to be 2.51 +/- 0.08 E-5 K-1 and 0.96 +/- 0.09 E-5 K-1 at room temperature while decreasing by an order of magnitude when cooling to 18 K. To show the effect of variations in the thermo-optic coefficients on device performance, we study the tuning of a fully integrated electrically tunable filter as a function of voltage for different temperatures. The presented results provide new practical guidelines in designing photonic circuits for studying low-temperature optical phenomena.
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| 14. |
- Eriksson, Tobias, 1986, et al.
(författare)
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Experimental Investigation of Crosstalk Penalties in Multicore Fiber Transmission Systems
- 2015
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- We experimentally study the impact of crosstalk in multicore fibers, using polarization-multiplexed quadrature phase-shift keying signals. Using a 7-core fiber, we perform single-span transmission experiments, where the level of crosstalk to the core under test can be varied. We find the penalty in the required optical signal-to-noise ratio (OSNR), compared to a system with no crosstalk, for different signal-to-crosstalk ratios and at different pre-forward-error-correction target bit-error rates (BERs). We show that, for a 1-dB penalty, a 15.7-dB signal-to-crosstalk ratio can be tolerated at BER = 1 x 10(-3). We also perform recirculating loop experiments with varying amount of crosstalk per span to find the impact on the achievable transmission distance.
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| 15. |
- Fan, Yuchuan, et al.
(författare)
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Linear Regression vs. Deep Learning for Signal Quality Monitoring in Coherent Optical Systems
- 2022
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers Inc.. - 1943-0655. ; 14:4
-
Tidskriftsartikel (refereegranskat)abstract
- Error vector magnitude (EVM) is a metric for assessing the quality of m-ary quadrature amplitude modulation (mQAM) signals. Recently proposed deep learning techniques, e.g., feedforward neural networks (FFNNs) -based EVM estimation scheme leverage fast signal quality monitoring in coherent optical communication systems. Such a scheme estimates EVM from amplitude histograms (AHs) of short signal sequences captured before carrier phase recovery (CPR). In this work, we explore further complexity reduction by proposing a simple linear regression (LR) -based EVM monitoring method. We systematically compare the performance of the proposed method with the FFNN-based scheme and demonstrate its capability to infer EVM from an AH when the modulation format information is known in advance. We perform both simulation and experiment to show that the LR-based EVM estimation method achieves a comparable accuracy as the FFNN-based scheme. The technique can be embedded with modulation format identification modules to provide comprehensive signal information. Therefore, this work paves the way to design a fast-learning scheme with parsimony as a future intelligent OPM enabler.
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| 16. |
- Feng, Zhenhua, et al.
(författare)
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Multicore-Fiber-Enabled WSDM Optical Access Network With Centralized Carrier Delivery and RSOA-Based Adaptive Modulation
- 2015
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Ingår i: IEEE PHOTONICS JOURNAL. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 7:4
-
Tidskriftsartikel (refereegranskat)abstract
- We proposed and experimentally demonstrated a wavelength-space division multiplexing (WSDM) optical access network architecture with centralized optical carrier delivery utilizing multicore fibers (MCFs) and adaptive modulation based on reflective semiconductor amplifier (RSOA). In our experiment, five of the outer cores are used for undirectional downstream (DS) transmission only, whereas the remaining outer core is utilized as a dedicated channel to transmit upstream (US) signals. Optical carriers for US are delivered from the optical line terminal (OLT) to the optical network unit (ONU) via the inner core and then transmitted back to the OLT after amplification and modulation by the RSOA in the colorless ONU side. The mobile backhaul (MB) service is also supported by the inner core. Wavelengths used in US transmission should be different from that of the MB in order to avoid the Rayleigh backscattering effect in bidirectional transmission. With quadrature phase-shift keying-orthogonal frequency-division multiplexing (QPSK-OFDM) modulation format, the aggregation DS capacity reaches 250 Gb/s using five outer cores and ten wavelengths, and it can be further scaled to 1 Tb/s using 20 wavelengths modulated with 16 QAM-OFDM. For US transmission, 2.5 Gb/s QPSK-OFDM transmission can be achieved just using a low-bandwidth RSOA, and adaptive modulation is applied to the RSOA to further enhance the US data rate to 3.12 Gb/s. As an emulation of high-speed MB transmission, 48 Gb/s inphase and quadrature (IQ) modulated popularization division multiplexing (PDM)-QPSK signal is transmitted in the inner core of MCF and coherently detected in the OLT side. Both DS and US optical signals exhibit acceptable performance with sufficient power budget.
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| 17. |
- Fougstedt, Christoffer, 1990, et al.
(författare)
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Filter Implementation for Power-Efficient Chromatic Dispersion Compensation
- 2018
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 10:4
-
Tidskriftsartikel (refereegranskat)abstract
- Chromatic dispersion (CD) compensation in coherent fiber-optic systems represents a very significant DSP block in terms of power dissipation. Since spectrally efficient coherent systems are expected to find a wider deployment in systems shorter than long haul, it becomes relevant to investigate filter implementation aspects of CD compensation in the context of systems with low-to-moderate amounts of accumulated dispersion. The investigation we perform in this paper has an emphasis on implementation aspects such as power dissipation and area usage, it deals with both time-domain and frequency-domain CD compensations, and it considers both A/D-conversion quantization and fixed-point filter design aspects. To enable an accurate analysis on power dissipation and chip area, the evaluated filters are implemented in a 28-nm fully depleted silicon-on-insulator (FD-SOI) process technology. We show that an optimization of the filter response that takes pulse shaping into account can significantly reduce power dissipation and area usage of time-domain implementations, making them a viable alternative to frequency-domain implementations.
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| 18. |
- Gong, H., et al.
(författare)
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Photothermal Switching Based on Silicon Mach-Zehnder Interferometer Integrated with Light Absorber
- 2016
-
Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 8:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present an all-optical switch based on photothermal effects in a silicon Mach-Zehnder interferometer (MZI) integrated with a light absorber. The metal-insulator-metal light absorber located near the longer arm of the asymmetric MZI efficiently converts infrared light to heat. Pumped by a continuous-wave 1064-nm laser, the spectral transmittance of the fully etched strip waveguide (half-etched rib waveguide) MZI can be tuned with an efficiency of 38 pm/mW (98.5 pm/mW). Dynamic switching experiments show that the rise/fall time constant of the output probe light is 11.45/10.98 μs (8.25/7.13 μs) for the fully etched (half-etched) MZI.
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| 19. |
- Gong, Hanmo, et al.
(författare)
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Photothermal switching based on silicon mach–zehnder interferometer integrated with light absorber
- 2016
-
Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 8:2
-
Tidskriftsartikel (refereegranskat)abstract
- We present an all-optical switch based on photothermal effects in a silicon Mach-Zehnder interferometer (MZI) integrated with a light absorber. The metal-insulator-metal light absorber located near the longer arm of the asymmetric MZI efficiently converts infrared light to heat. Pumped by a continuous-wave 1064-nm laser, the spectral transmittance of the fully etched strip waveguide (half-etched rib waveguide) MZI can be tuned with an efficiency of 38 pm/mW (98.5 pm/mW). Dynamic switching experiments show that the rise/fall time constant of the output probe light is 11.45/10.98 μs (8.25/7.13 μs) for the fully etched (half-etched) MZI.
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| 20. |
- Hoa, Nguyen Thi Quynh, et al.
(författare)
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Numerical Study of a Wide-Angle and Polarization-Insensitive Ultrabroadband Metamaterial Absorber in Visible and Near-Infrared Region
- 2019
-
Ingår i: IEEE Photonics Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1943-0655. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- An ultrabroadband metamaterial absorber structure based on a periodic array of metallic-dielectric multilayered conical frustums is numerically investigated and proposed. The metamaterial absorber indicated an absorptivity of higher than 90%, which covered the visible and near-infrared region at 480-1480 nm, and a relative absorption bandwidth of 102%. The high absorptivity can be maintained with large incident angles up to 60 degrees under both transverse electric and transverse magnetic polarizations. Furthermore, the proposed absorber exhibits polarization insensitivity owing to its rotational symmetry structure. Compared with the previously reported ultrabroadband metamaterial absorbers, the design in this work indicates high practical feasibility in terms of a compact structure for a large bandwidth, a wide incident angle, and polarization insensitivity, thereby suggesting its promising application, for example, in solar cells and thermal emitters.
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| 21. |
- Huang, Lingchen, et al.
(författare)
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Design and Analysis of a CO-OFDM Transmitter With Limited Modulator Extinction Ratio
- 2014
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 6:3, s. 7200207-
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we consider the design and analysis of a coherent optical OFDM (CO-OFDM) transmitter using an optical in-phase/quadrature (I/Q) modulator with limited extinction ratio (ER) under four modulation formats. The transmitter-side digital signal processing (DSP), including hard clipping and predistortion, is introduced to combat the penalty induced by the limited ER of the modulator and the quantization noise of the digital-to-analog converter (DAC). The DAC resolution needed for transmitters using modulators with various ER values are examined. The peak-to-peak driving voltage (Vpp) and the clipping ratio (CR) of the transmitted signals are also optimized with respect to minimizing the Q-factor penalty for the modulator with different ER values. The simulation results show that, unlike previous work using modulators with an infinite ER, the optimum Vpp and CR values vary with different ERs and modulation levels.
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| 22. |
- Jiang, Tao, et al.
(författare)
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Investigation of DC-Biased Optical OFDM With Precoding Matrix for Visible Light Communications : Theory, Simulations, and Experiments
- 2018
-
Ingår i: IEEE Photonics Journal. - : IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC. - 1943-0655. ; 10:5
-
Tidskriftsartikel (refereegranskat)abstract
- Orthogonal frequency-division-multiplexing (OFDM) technology is widely used in visible light communication (VLC) to achieve high data rate transmission. However, the traditional direct-current (DC)-biased optical OFDM (DCO-OFDM) VLC systems suffer from the high peak-to-average power ratio (PAPR) which causes signal clipping distortion, and, thus, performance degradation. Furthermore, severe high-frequency fading due to the limited system bandwidth results in poor bit error rate (BER) performance. Precoding matrix (PM) techniques have been proposed to enhance the performance of VLC OFDM transmission, but a little or no work has been carried out in investigating the theory of PM used in OFDM VLC systems. In this paper, we aim to reveal the theory of PM-DCO-OFDM for a VLC system. To figure out the intrinsic laws of a PM method, we investigate the principles of PAPR reduction, clipping distortion optimization, and signal-to-noise ratio (SNR) distribution equalization. Based on the analysis of PAPR, we theoretically proved the simplicity of PM as a method to reduce the possibility of high PAPR by improving the autocorrelation performance of input symbols. The clipping distortion could be improved due to the reduction of high PAPR. Moreover, the relatively uniform SNR distribution can be achieved by PM through equalizing the clipping and channel noise, which is beneficial to improve the BER performance in high-frequency constrained systems. However, the PM method used in a DCO-OFDM VLC system should consider the transmitting power, modulation format, and transmission distance as a whole to achieve the transmission performance improvement. The simulation results demonstrate the complementary cumulative distribution function of PAPR can be reduced similar to 3 dB, while the performance of clipping distortion power and clipping error probability are significantly improved. Furthermore, experiment is carried out with results showing that the PM method can improve the BER performance in the case that VLC OFDM transmission has enough transmitting power, but with the low transmitting power, the PM also can damage the BER performance. The simulation and experiment results are consistent with our theoretical analysis.
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| 23. |
- Kores, Cristine Calil, et al.
(författare)
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Accumulation of Distributed Phase Shift in Distributed-Feedback Resonators
- 2019
-
Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 11:1
-
Tidskriftsartikel (refereegranskat)abstract
- Distributed-feedback waveguide lasers based on Bragg-grating resonators generate ultranarrow-linewidth emission. Oscillation at the center of the reflection band ensures maximum reflectivity, hence minimum linewidth. The required pi/2 phase shift is often introduced by a distributed change in effective refractive index, e.g., by widening the waveguide. Despite careful design and fabrication, the experimentally observed resonance wavelength deviates from the designed wavelength. Even when thermally induced chirp or fabrication errors are negligible, this deviation is still present. Here, we show theoretically and experimentally that this deviation is of fundamental nature. The decay of light intensity during propagation from the phase-shift center into both sides of the Bragg grating due to reflection by the periodic grating and the refractive index change causes an incomplete accumulation of designed phase shift, thereby systematically shifting the resonance to a shorter wavelength. Considering the overlap integral between the distributed phase shift and light intensity in the design provides the desired performance.
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| 24. |
- Kumari, Sulakshna, et al.
(författare)
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Design of an 845-nm GaAs Vertical-Cavity Silicon-Integrated Laser with an Intracavity Grating for Coupling to a SiN Waveguide Circuit
- 2017
-
Ingår i: IEEE Photonics Journal. - 1943-0655. ; 9:4, s. 1504109-
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Tidskriftsartikel (refereegranskat)abstract
- A short-wavelength hybrid GaAs vertical-cavity silicon-integrated laser (VCSIL) with in-plane waveguide coupling has been designed and optimized using numerical simulations. A shallow etched silicon nitride (SiN) grating is placed inside the cavity of the hybrid vertical-cavity silicon-integrated laser to both set the polarization state of the resonant optical field and to enable output coupling to a SiN waveguide with high efficiency. The numerical simulations predict that for apertures of 4 and 6-μm oxide-confined VCSILs operating at 845-nm wavelength, a slope efficiency for the light coupled to the waveguide of 0.18 and 0.22 mW/mA is achievable, respectively, while maintaining a low threshold gain of 583 and 589 cm−1, respectively, for the lasing.
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| 25. |
- Lebedev, Alexander, et al.
(författare)
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Feasibility study and experimental verification of simplified fiber-supported 60-GHz picocell mobile backhaul links
- 2013
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 5:4, s. 7200913-7200913
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Tidskriftsartikel (refereegranskat)abstract
- We propose and experimentally demonstrate a fiber-wireless transmission system for optimized delivery of 60-GHz radio frequency (RF) signals through picocell mobile backhaul connections. We identify advantages of 60-GHz links for utilization in short-range mobile backhaul through feasibility analysis and comparison with an alternative E-band (60-90 GHz) technology. The 60-GHz fiber-wireless-fiber setup is then introduced: two spans of up to 20 km of optical fiber are deployed and bridged by up to 4 m of wireless distance. The 60-GHz radio-over-fiber technology is utilized in the first span of fiber transmission. The system is simplified and tailored for delivery of on-off keying data signals by employing a single module for lightwave generation and modulation combined with a simplified RF downconversion technique by envelope detection. Data signals of 1.25 Gb/s are transmitted, and a bit-error-rate performance below the 7% overhead forward-error-correction limit is achieved for a range of potential fiber deployment scenarios. A spurious free dynamic range of 73 dB-Hz2/3 is attained for a frequency-doubling photonic RF upconversion technique. The power budget margin that is required to extend the wireless transmission distance from 4 m to a few hundred meters has been taken into account in the setup design, and the techniques to extend the wireless distance are analyzed.
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| 26. |
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| 27. |
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| 28. |
- Liu, Shih-Chia, et al.
(författare)
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Size Scaling of Photonic Crystal Surface Emitting Lasers on Silicon Substrates
- 2018
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 10:3
-
Tidskriftsartikel (refereegranskat)abstract
- We report here the lateral cavity size scaling and confinement effects on the lasing performance in defect-free photonic crystal surface-emitting lasers (PCSEL) on silicon substrates Hybrid PCSELs with different lateral cavity sizes and different lateral confinement geometries have been fabricated using transfer printing technology and controlled selective etching The measured lasing properties show a strong dependence on the lateral cavity size below 100 mu m. In particular, the finite lateral dimension significantly affects the laser threshold and side mode suppression ratio (SMSR) of the PCSEL devices On the other hand, by controlling the lateral confinement using vertical etching, a reduction of the laser threshold is observed The experimental results agree well with theoretical predictions The work presented here can lead to ultra-compact PCSELs for on-chip integration with excellent energy efficiency.
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| 29. |
- Menon, L., et al.
(författare)
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Heterogeneously Integrated InGaAs and Si Membrane Four-Color Photodetector Arrays
- 2016
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- We report the design and fabrication of heterogeneously integrated silicon and InGaAs membrane photodetector arrays. Visible and near-infrared (NIR) detection can be achieved by transfer printing a silicon membrane on InGaAs substrate. Based on the penetration-depth-dependent absorption of different wavelengths, filter-free visible color detection can be obtained via three-junction photocurrent measurement for silicon, and NIR can be detected by InGaAs. The measurements show good agreement with the optical behavior predicted by the design and simulation.
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| 30. |
- Odeh, Mutasem, et al.
(författare)
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Mode Sensitivity Analysis of Subwavelength Grating Slot Waveguides
- 2019
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we investigate the mode sensitivity (S-mode) of subwavelength grating slot (SWGS) waveguides. S-mode is an important parameter in various waveguide-based photonic circuits such as sensors, modulators, and thermally-controlled devices. It is a measure of the sensitivity of the waveguide effective index towards the refractive index perturbations in the cladding medium. The SWGS waveguide exhibits high mode sensitivity, as it combines sensitivity enhancement features of both slot and subwavelength grating waveguides. Finite-difference time-domain simulations are performed for the analysis, design, and optimization of the hybrid structure. The SWGS waveguide is incorporated into a Mach-Zehnder interferometer and fabricated on a silicon-on-insulator platform for the experimental estimation of S-mode. The measured S-mode value of 79% is consistent with the theoretical prediction of 83%.
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| 31. |
- Pang, Xiaodan, 1986-, et al.
(författare)
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25 Gbit/s QPSK Hybrid Fiber-Wireless Transmission in the W-Band (75–110 GHz) With Remote Antenna Unit for In-Building Wireless Networks
- 2012
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Ingår i: IEEE Photonics Journal. - : IEEE. - 1943-0655. ; 4:3, s. 691-698
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we demonstrate a photonic up-converted 25 Gbit/s fiber-wireless quadrature phase shift-keying (QPSK) data transmission link at the W-band (75-110 GHz). By launching two free-running lasers spaced at 87.5 GHz into a standard single-mode fiber (SSMF) at the central office, a W-band radio-over-fiber (RoF) signal is generated and distributed to the remote antenna unit (RAU). One laser carries 12.5 Gbaud optical baseband QPSK data, and the other acts as a carrier frequency generating laser. The two signals are heterodyne mixed at a photodetector in the RAU, and the baseband QPSK signal is transparently up-converted to the W-band. After the wireless transmission, the received signal is first down-converted to an intermediate frequency (IF) at 13.5 GHz at an electrical balanced mixer before being sampled and converted to the digital domain. A digital-signal-processing (DSP)-based receiver is employed for offline digital down-conversion and signal demodulation. We successfully demonstrate a 25 Gbit/s QPSK wireless data transmission link over a 22.8 km SSMF plus up to 2.13 m air distance with a bit-error-rate performance below the 2 x 10(-3) forward error correction (FEC) limit. The proposed system may have the potential for the integration of the in-building wireless networks with the fiber access networks, e. g., fiber-to-the-building (FTTB).
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| 32. |
- Puttnam, Benjamin, et al.
(författare)
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Impact of Intercore Crosstalk on the Transmission Distance of QAM Formats in Multicore Fibers
- 2016
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 8:2
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the impact of intercore crosstalk on the achievable transmission distance of three square quadrature amplitude modulation (QAM) formats. We show that increasing intercore crosstalk across an 18 dB range starting from -43.4 dB/100 km reduces the achievable transmission distance for all formats, with a greater impact on higher order modulation formats. For a crosstalk level arising from equal signal launch power in each core of a homogeneous 7-core fiber, we measure a reduced transmission distance at BER = 1.5 × 10-2 of 24%, 38% and 54%, for polarization-division-multiplexed-quadrature phase-shift keying (PDM-QPSK), PDM-16QAM, and PDM-64QAM, respectively. Finally, we investigate the potential impact that dynamic crosstalk variation could have in transmission systems based on multicore fiber and estimate the achievable reach for an outage probability of 1 × 10-5 in the presence of dynamically varying intercore crosstalk.
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| 33. |
- Ryu, Jae Ha, et al.
(författare)
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Reverse-Taper Mid-Infrared Quantum Cascade Lasers for Coherent Power Scaling
- 2022
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 14:3
-
Tidskriftsartikel (refereegranskat)abstract
- We present a reverse-taper quantum cascade laser (QCL) emitting at 4.6 mu m, a novel-geometry device that can scale the output power while maintaining good beam quality. Buried-ridge waveguides with tapered and straight regions were formed by ICP etching and HVPE regrowth - the tapered region scales the output power, while the emitting facet is located at the narrow-end taper section, which provides mode filtering by suppressing high-order spatial modes. Beam profiles were observed under quasi-continuous-wave (QCW)/CW operation and beam quality (M-2) measurements along with beam-stability measurements were performed - a small degree of collimated-beam centroid movement (<0.46 mrad, peak-to-peak) was observed, along with M-2 values close to 1 up to similar to 1 W QCW power. Devices of shorter cavity lengths were also investigated, indicating that the output power scales with the core-region volume but results in a small increase in angular deviation.
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| 34. |
- Soares, Francisco M., et al.
(författare)
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Monolithic InP 100-Channel X 10-GHz Device for Optical Arbitrary Waveform Generation
- 2011
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 3:6, s. 975-985
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate monolithic integration of a 100-channel arrayed-waveguide grating (AWG) with 10-GHz channel spacing and 100 optically controlled Michelson-interferometer-based phase and amplitude modulators. The high-resolution AWG showed better than -15-dB crosstalk, and the modulator extinction ratio was better than 20 dB with either electrical or optical modulation control. The twin-integrated devices comprise a 50-mm diameter InP wafer with 1200 independent optoelectronic components.
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| 35. |
- Soltanmoradi, Reyhaneh, et al.
(författare)
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Transmission of Infrared Radiation Through Metallic Photonic Crystal Structures
- 2013
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 5:5, s. 4500608-
-
Tidskriftsartikel (refereegranskat)abstract
- Monolithic integration of a metallic photonic crystal (mPhC) structure onto semiconductor infrared (IR) photodetectors can enhance the detector performances. In order to experimentally investigate the parameters involved in optimizing the transmission spectra of the mPhC structures matching the detector operating wavelength in mid- and long-wave IR (MWIR and LWIR) regimes, square thin gold (Au) hole arrays having periodicities of 4.0, 3.6, 2.4, and 1.8 mu m with various fill factors were fabricated on Si or GaAs substrates in a wafer scale. The thicknesses of the Au films are 50, 100, and 200 nm, respectively. Through this systemic study, suitable mPhC structures were revealed that can be readily integrated onto our type-II InGaSb-based quantum dot MWIR and LWIR photodetectors.
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| 36. |
- Tian, Jiahan, et al.
(författare)
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Wide-Field-of-View Modulating Retro-Reflector System Based on a Telecentric Lens for High-Speed Free-Space Optical Communication
- 2023
-
Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 15:5
-
Tidskriftsartikel (refereegranskat)abstract
- Modulating retro-reflector (MRR) free-space optical (FSO) communication technology presents a bright future for realizing the small size, weight, and power (SWaP) design of one end of the optical link, facilitating the further application of the FSO communication to the small platforms. However, the limited field-of-view (FOV) of MRR impedes its wide employment. In this article, a novel wide-FOV MRR using an image space telecentric lens is proposed and a bidirectional FSO communication system is experimentally demonstrated using this MRR with a single light source. The performance of the telecentric lens between the transceiver and terminal is assessed by simulation and also validated by experimental results, with a coupling loss less than 9.1 dB within a FOV of 110 degrees. Both 10-Gbit/s on-off keying (OOK) downstream and upstream signals for free space communication at different incident angles are successfully realized using this designed wide-FOV MRR. The experimental results validate the proposed MRR has a FOV of up to 110 degrees where the measured bit error rate (BER) is lower than 3.8 x 10-3 for both downstream and upstream signals. To the best of our knowledge, this is the largest FOV ever reported for MRRs in high-speed bidirectional FSO communication systems.
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| 37. |
- Wang, Liang, et al.
(författare)
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Distributed Temperature Sensing Using Stimulated-Brillouin-Scattering-Based Slow Light
- 2013
-
Ingår i: IEEE Photonics Journal. - 1943-0655. ; 5:6, s. 6648635-
-
Tidskriftsartikel (refereegranskat)abstract
- Distributed temperature sensing has been achieved by spatially resolved measurement of the probe time delay resulted from stimulated-Brillouin-scattering slow light. The temperature of a particular fiber section can be monitored by setting an appropriate relative delay between the pump and probe pulses. By controlling the relative delay, we have achieved distributed profiling of the temperature along the whole sensing fiber. This scheme provides an alternative way for distributed temperature sensing with the potential of real-time temperature monitoring. A relatively high-temperature resolution of 0.7 degrees C is obtained.
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| 38. |
- Wang, Ruoxu, et al.
(författare)
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Demonstration of Programmable In-Band OSNR Monitoring Using LCFBG With Commercial Thermal Printer Head
- 2015
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Ingår i: IEEE PHOTONICS JOURNAL. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 7:4
-
Tidskriftsartikel (refereegranskat)abstract
- We proposed and experimentally demonstrated a programmable optical signal-to-noise ratio (OSNR) monitoring scheme by using linearly chirped fiber Bragg grating (LCFBG) and a commercial thermal printer head. For the coherent optical orthogonal frequency-division multiplexing (CO-OFDM) transmission system, the monitor's working wavelength can be flexibly software-controlled from 1530 to 1538 nm to support standard ITU-T grid or flex-grid operation. The linear OSNR monitoring range has been achieved from 9 to 26 dB for a 16-quadrature amplitude modulation (QAM) OFDM transmission system with negligible errors, respectively. Neither chromatic dispersion nor polarization mode dispersion affect the monitoring accuracy of our system.
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| 39. |
- Wang, R., et al.
(författare)
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Electrically programmable all-fiber structured second order optical temporal differentiator
- 2015
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Ingår i: IEEE Photonics Journal. - 1943-0655. ; 7:3
-
Tidskriftsartikel (refereegranskat)abstract
- We propose and experimentally demonstrate an electrically programmable second order optical temporal differentiator (OTD) based on linearly chirped fiber Bragg grating (LCFBG) and digital thermal print head (TPH). For the high-speed optical signal with 25-GHz repetition rate, an efficient second-order OTD has been achieved for arbitrary wavelength and bandwidth with the software-defined TPH configurations. By optimizing the thermooptic effect induced optical phase change in the LCFBG, the central wavelength of the differentiator can be reconfigured flexibly from 1543.5 to 1561.7 nm, with a step size of 0.114 nm. By dynamically controlling the heating elements bonded with the LCFBG, optical pulses with 0.55- and 0.8-nm 3-dB bandwidths have been successfully processed with acceptable deviation compared with the theoretical calculations.
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| 40. |
- Ye, Xiaoling, et al.
(författare)
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High Performance Self-Powered Photodetectors Based on Graphene Nanoribbons/Al2O3/InGaZnO Heterojunctions
- 2024
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Ingår i: IEEE Photonics Journal. - : Institute of Electrical and Electronics Engineers (IEEE). - 1943-0655. ; 16:3
-
Tidskriftsartikel (refereegranskat)abstract
- Self-powered photodetectors which operate without external power sources hold immense promise in future photodetection systems. To achieve high-performance self-powered optoelectronic devices, efficient electron-hole pair separation is critical to generate high photocurrents. In this work, we successfully synthesized semiconducting graphene nanoribbons (GNRs) with a direct bandgap of 1.80 eV and employed them to construct a high-performance GNR/Al2O3/IGZO heterostructure photodetector. The built-in electric field in the heterojunctions enables this photodetector to exhibit remarkable performance, showing a responsivity of up to 68 mA/W, a detectivity of 8.34 x 1010 Jones, and rapid response times of 21/20 ms at zero bias. Furthermore, the photodetector features a wide spectral detection range of 405 to 1550 nm. These results highlight the promising potential of GNR/IGZO p-n heterojunction-based self-powered photodetectors in optoelectronic applications.
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| 41. |
- Zhou, Bin, et al.
(författare)
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Cladding-Mode-Recoupling-Based Tilted Fiber Bragg Grating Sensor With a Core-Diameter-Mismatched Fiber Section
- 2010
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Ingår i: IEEE PHOTONICS J. - 1943-0655. ; 2:2, s. 152-157
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a reflective fiber-optic sensor with a core-diameter-mismatched fiber section and cladding-mode recoupling in a tilted fiber Bragg grating (TFBG). High-order cladding modes are efficiently excited by either a multimode fiber or a thin-core fiber section and recoupled back to the core mode by the TFBG. A special reflection spectrum with recoupling of cladding mode is then obtained to exploit the applications of evanescent waves in an optical fiber. Experimental results of the sensor to measure the external refractive index are presented.
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