- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Characterization of a Low-Cost, Monolithically Integrated, Tunable 10G Transmitter for Wavelength Agile PONs
摘要： Dynamically reconfigurable passive optical networks (PONs) using time-division multiplexing and dense wavelength division multiplexing will require low-cost, high-performance customer premises equipment to be economically viable. In particular, substantial cost savings can be achieved through the use of efficient re-growth free, foundry-compatible fabrication techniques. Using this strategy, this paper presents the first detailed characterization of a monolithically integrated transmitter comprised of a discretely tunable slotted Fabry–Pérot ridge waveguide laser, an absorptive modulator and a semiconductor optical amplifier (SOA) produced using a standard off-the-shelf AlInGaAs/InP multiple quantum well epitaxial structure. This first generation device demonstrates a discrete single-mode tuning range of approximately 12 nm between 1551nm and 1563 nm with a side-mode suppression ratio ≥30 dB. Moreover, the integrated modulator section is shown to support transmission at 10 Gb/s using non-return to zero on-off keying with an extinction ratio in excess of 8 dB. Furthermore, using a time-resolved chirp measurement technique to examine dynamic deviations in the set carrier frequency, the modulator section exhibits a chirp contribution of <6 GHz using test patterns with high and low frequency content. In addition, the generation of optical bursts through the application of a gating function to the SOA section was found to shift the unmodulated carrier of a typical lasing mode by ≤8 GHz for gating periods comparable with a typical PON burst durations of 125 μs which are faster than the thermal response time of the transmitter material.
关键词： Optical communications,tunable semiconductor lasers,dense wavelength division multiplexing,passive optical networks,time division multiplexing,monolithic integration
更新于2025-09-23 15:21:01
-
Fast reconstruction of two-wavelength off-axis multiplexed holograms using division-multiplexing and critical sampling
摘要： Benefiting from two-wavelength information multiplexed into one hologram, two-wavelength off-axis holography can perform simultaneous quantitative phase imaging in an extended thickness range. However, its present phase processing still adopts the traditional Fourier-based method at the expense of the reconstruction speed. Hence, we propose a fast approach by combining critical sampling with division multiplexing. In our approach, the critical sampling is used to remove the redundant data, and the division multiplexing is developed to eliminate the redundant calculation processes. Experimental results illustrate that our approach can yield faster reconstruction with frame rates up to 46 fps even for one megapixel multiplexed holograms at two wavelengths on a single-core personal computer.
关键词： Critical sampling,Multiplex holography,Dual-wavelength digital holography,Fast phase retrieval
更新于2025-09-23 15:21:01
-
Poincaré sphere-based technique for tuning flat-top fiber comb filter
摘要： We propose a universal method for designing flat-top passband and wavelength tuning of transmission spectrum of a fiber comb filter based on a polarization-diversified loop structure using Poincaré sphere representation. The proposed method gives a clear visualization of the evolution of polarization state through birefringent optical elements comprising the filter, and the design results are experimentally verified. Our method can also suggest which optical components are necessary for a specifically desired transmission spectrum of the comb filter.
关键词： flat-top passband,polarization-diversified loop structure,fiber comb filter,Poincaré sphere,wavelength tuning
更新于2025-09-23 15:21:01
-
<p>532-nm Subthreshold Micropulse Laser for the Treatment of Chronic Central Serous Retinopathy</p>
摘要： Introduction: Subthreshold micropulse laser treatment with a 532 nm (532-SML) wavelength has been suggested as a treatment option for the treatment of chronic central serous retinopathy (cCSR). The objective is to present its effects and complications. Methods: We present a retrospective cohort study of cCSR patients submitted to 532-SML. Best-corrected visual acuity (BCVA) and spectral-domain optical coherence tomography (SD-OCT) parameters – central macular thickness, subfoveal outer nuclear layer, external limiting membrane, ellipsoid band, interdigitation band, subretinal ?uid and choroidal thickness – were evaluated before and 12 weeks after treatment. A power of 50%, a duty cycle of 5%, exposure time of 200 ms and a spot size of 160 μm were the applied laser parameters. Results: We included 26 eyes. Overall there were no signi?cant changes in visual acuity (median 0.20 (IQR 0) logMAR before and after treatment) or SD-OCT parameters. However, visual bene?ts occurred in 42.3% (n=11) of the patients and in half of the cases, subretinal ?uid was completely reabsorbed. There were no complications. Conclusion: In this study, 532-SML was overall ineffective on cCSR as it did not lead to signi?cant changes in the overall median visual acuity and SD-OCT parameters. However, some patients may have bene?ted functionally and anatomically from the treatment; further investigation is necessary to understand the potential of 532-SML.
关键词： 532 nm wavelength,subthreshold micropulse laser,outer retina bands,SD-OCT,central serous retinopathy
更新于2025-09-23 15:19:57
-
Preparation and characterization of carbon nanotubes by pulsed laser ablation in water for optoelectronic application
摘要： In the present work, preparation of multi-walled carbon nanotubes (MWCNTs) and carbon nanoparticles (CNPs) by using pulsed laser ablation of a graphite target in water without using catalyst was demonstrated. The effect of laser wavelength on the optical absorption and structural properties has been studied. X-ray diffraction (XRD) data shows the synthesized CNTs were polycrystalline and a peak related to the diamond structure was observed. Scanning electron microscope (SEM) investigation displays that the average diameter of CNTs synthesized with 532 nm was 20 nm and few micrometers in length, while the CNTs synthesized with 1064 nm have an average diameter of 75 nm and lengths of few sub-micrometers. Some of CNPs were noticed to deposit on the CNTs. Transmission electron microscope (TEM) was used to study the morphology of MWCNTs. Raman spectra confirm formation of MWCNTs during the presence of three peaks belonged to D-band, G-band and 2D-band. The intensity ratio of IG/ID is larger than unity for MWCTs prepared by two laser wavelengths. The colloidal MWCNTs prepared by 532 nm laser pulses showed higher absorption than that of MWCNTs prepared with 1064 nm. The current-voltage characteristics and responsivity of hybrid In/p-MWCNTs/n-Si heterojunction photodetectors prepared at different CNTs film thicknesses were investigated at room temperature. The responsivity of hybrid MWCNTs/n-Si photodetector has two peaks of response, the first peak was found at 650 nm and the second peak located at 850 nm. The maximum responsivity was 0.53 A/W at 532 nm was found for the photodetector fabricated with 532 nm laser. The energy band diagram of MWCNTs/Si heterojunction was constructed under illumination condition.
关键词： Hybrid photodetector,CNTs,Laser ablation,CNTs thickness,Laser wavelength
更新于2025-09-23 15:19:57
-
Transmission characteristics of 24.5??Gb/s atmospheric laser communication based on optical frequency comb
摘要： Through cascading Mach–Zehnder intensity modulator (MZIM) and phase modulator (PM), an optical frequency comb (OFC) with 7 flat comb teeth is produced. The frequency interval of the OFC is 25 GHz and the flatness is less than 1.5 dB. The 7 channels of the OFC are used as the carrier source of the one-to-many free-space optical (FSO) communication system, and the atmospheric turbulence simulation pool is used to simulate the turbulence intensity in the real atmosphere to verify its feasibility for FSO communication. In the experiment, the bit error rate (BER) and eye diagram are measured under the back-to-back (BTB) conditions, and the temperature difference of atmospheric turbulence simulation pool are 80 ?C, 150 ?C and 220 ?C. Each channel of the system can stably transmit the on–off keying (OOK) signal of 3.5 Gb/s, and the 7 channels can stably transmit the OOK signal of 24.5 Gb/s. Thereby, the OFC can be used in place of multiple lasers or laser arrays as a carrier source for a one-to-many FSO communication system.
关键词： Wavelength division multiplexing,Optical frequency comb,Atmospheric turbulence,Free-space optical communication
更新于2025-09-23 15:19:57
-
Orthogonally polarized dual-wavelength laser based totally on intrinsic birefringence of the gain crystal
摘要： Based totally on the intrinsic difference of polarizing emission spectra and birefringence of the a-cut Nd:YAP gain crystal, an orthogonally polarized 1079.5 and 1099 nm dual-wavelength laser is demonstrated. A specially designed dielectric Fabry–Perot filter is exploited as output coupler and gain balancer of the laser cavity. The maximum output power and slope conversion efficiency of the dual-wavelength laser is 976 mW and 7%, respectively. The experimental results show that the intrinsic birefringence of the laser gain material is the principle source for the generation of the orthogonal polarized laser. The competition between the two lasing wavelengths is analyzed and attributed to the stark energy levels involved. The method presented can be used to other biaxial laser gain crystals for the generation of orthogonal polarized dual-wavelength lasers.
关键词： intrinsic birefringence,orthogonally polarized,dual-wavelength laser
更新于2025-09-23 15:19:57
-
Study of high power Tm:YLF Innoslab wavelength-selected laser
摘要： In this study, a laser diode dual-end-pumped Tm:YLF slab laser has been developed. Without using a Fabry–Pérot etalon or a volume Bragg grating, the emission wavelength was selected by different transmissions of the output coupler. The single emission wavelength of 1908.6 nm (1886.4 nm) is selected by the T = 20% (T = 40%) transmission of the output coupler with an FWHM of approximately 1.36 nm (1.10 nm). The corresponding maximum continuous-wave output power of 213 W (173 W) was acquired. The output power stability is about 0.16% (0.23%) in 30 minutes. The optical-to-optical efficiency and slope efficiency are 35.8% (29%) and 43.7% (37.9%), respectively.
关键词： Tm:YLF slab,dual-end-pumped,wavelength-selected,power stability
更新于2025-09-23 15:19:57
-
High performance Zn-diffused planar mid-wavelength infrared type-II InAs/InAs <sub/>1a??x</sub> Sb <sub/>x</sub> superlattice photodetector by MOCVD
摘要： We report a Zn-diffused planar mid-wavelength infrared photodetector based on type-II InAs/InAs1?xSbx superlattices. Both the superlattice growth and Zn diffusion were performed in a metal-organic chemical vapor deposition system. At 77 K, the photodetector exhibits a peak responsivity of 0.70 A/W at 3.65 μm, corresponding to a quantum efficiency of 24% at zero bias without anti-reflection coating, with a 50% cutoff wavelength of 4.28 μm. With an R0A value of 3.2 × 105 Ω cm2 and a dark current density of 9.6 × 10?8 A/cm2 under an applied bias of ?20 mV at 77 K, the photodetector exhibits a specific detectivity of 2.9 × 1012 cm Hz1/2/W. At 150 K, the photodetector exhibits a dark current density of 9.1 × 10?6 A/cm2 and a quantum efficiency of 25%, resulting in a detectivity of 3.4 × 1011 cm Hz1/2/W.
关键词： specific detectivity,metal-organic chemical vapor deposition,type-II InAs/InAs1?xSbx superlattices,quantum efficiency,Zn-diffused planar mid-wavelength infrared photodetector
更新于2025-09-23 15:19:57
-
[IEEE 2019 Workshop on Recent Advances in Photonics (WRAP) - Guwahati, India (2019.12.13-2019.12.14)] 2019 Workshop on Recent Advances in Photonics (WRAP) - Quantum cascade laser-based in situ measurement of atmospheric CO and CO <sub/>2</sub> in Gandhinagar using 1f and 2f wavelength modulation spectroscopy
摘要： We report the design, development and field deployment of a quantum cascade laser-based tunable diode laser spectroscopy (TDLS) system for high-sensitivity measurement of atmospheric CO and CO2. Two distributed-feedback quantum cascade lasers are used to interrogate the rotational-vibrational transitions of CO at 4594.99 nm and CO2 at 4319.30 nm. The mean mole fraction values for CO and CO2 for the measurements made at Gandhinagar from 19-25 July 2019 are 477 ppb and 486 ppm respectively. The detection limit of the system is 3 ppb CO and 45 ppb CO2 for integration time of 17 s and 69 s respectively.
关键词： air quality monitoring,greenhouse gas monitoring,quantum cascade laser,wavelength modulation spectroscopy
更新于2025-09-23 15:19:57