Contents
2019
Volume: 7 Issue 10
12 Article(s)
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Reviews
Fiber Optics and Optical Communications
LED-based fiber quantum key distribution: toward low-cost applications
Xiu-Xiu Xia, Zhen Zhang, Hong-Bo Xie, Xiao Yuan... and Jian-Wei Pan|Show fewer author(s)
We report a quantum key distribution (QKD) system that uses light-emitting-diodes (LEDs) at 1310 nm as optical sources. Compared to the normally used laser diodes (LDs), LEDs are easier to manufacture and integrate, and thus have the potential to reduce the costs of practical systems. To demonstrate the feasibility of a low-cost, integratable QKD system that aims at meeting the demand of the last-mile secure communication, we utilize LEDs at 1310 nm as the optical sources, while using only passive optical components and only one single photon detector at the receiver’s side. With a repetition rate of 10 MHz, we obtain secure key rates of 10.9 kbps within the experimental time of 1000 s over a fiber length of 1 km.We report a quantum key distribution (QKD) system that uses light-emitting-diodes (LEDs) at 1310 nm as optical sources. Compared to the normally used laser diodes (LDs), LEDs are easier to manufacture and integrate, and thus have the potential to reduce the costs of practical systems. To demonstrate the feasibility of a low-cost, integratable QKD system that aims at meeting the demand of the last-mile secure communication, we utilize LEDs at 1310 nm as the optical sources, while using only passive optical components and only one single photon detector at the receiver’s side. With a repetition rate of 10 MHz, we obtain secure key rates of 10.9 kbps within the experimental time of 1000 s over a fiber length of 1 km..
Photonics Research
- Publication Date: Oct. 01, 2019
- Vol. 7, Issue 10, 1169 (2019)
Optical Devices
Droplet Raman laser coupled to a standard fiber
Shai Maayani, and Tal Carmon
We fabricate a tapered fiber coupler, position it near an ultrahigh-Q resonator made from a microdroplet, and experimentally measure stimulated Raman emission. We then calculate the molecular vibrational mode associated with each of the Raman lines and present it in a movie. Our Raman laser lines show themselves at a threshold of 160 μW input power, the cold-cavity quality factor is 250 million, and mode volume is 23 μm3. Both pump and Raman laser modes overlap with the liquid phase instead of just residually extending to the fluid.We fabricate a tapered fiber coupler, position it near an ultrahigh-
Photonics Research
- Publication Date: Oct. 01, 2019
- Vol. 7, Issue 10, 1188 (2019)
Research Articles
Integrated Optics
Monolithic integration of MoS2-based visible detectors and GaN-based UV detectors | On the Cover
You Wu, Zhiwen Li, Kah-Wee Ang, Yuping Jia... and Dabing Li|Show fewer author(s)
With the increasing demand for high integration and multi-color photodetection for both military and civilian applications, the research of multi-wavelength detectors has become a new research hotspot. However, current research has been mainly in visible dual- or multi-wavelength detectors, while integration of both visible light and ultraviolet (UV) dual-wavelength detectors has rarely been studied. In this work, large-scale and high-quality monolayer MoS2 was grown by the chemical vapor deposition method on transparent free-standing GaN substrate. Monolithic integration of MoS2-based visible detectors and GaN-based UV detectors was demonstrated using common semiconductor fabrication technologies such as photolithography, argon plasma etching, and metal deposition. High performance of a 280 nm and 405 nm dual-wavelength photodetector was realized. The responsivity of the UV detector reached 172.12 A/W, while that of the visible detector reached 17.5 A/W. Meanwhile, both photodetectors achieved high photocurrent gain, high external quantum efficiency, high normalized detection rate, and low noise equivalent power. Our study extends the future application of dual-wavelength detectors for image sensing and optical communication.With the increasing demand for high integration and multi-color photodetection for both military and civilian applications, the research of multi-wavelength detectors has become a new research hotspot. However, current research has been mainly in visible dual- or multi-wavelength detectors, while integration of both visible light and ultraviolet (UV) dual-wavelength detectors has rarely been studied. In this work, large-scale and high-quality monolayer
Photonics Research
- Publication Date: Sep. 10, 2019
- Vol. 7, Issue 10, 1127 (2019)
Lasers and Laser Optics
Solid-state Mamyshev oscillator
Mingming Nie, Jiarong Wang, and Shu-Wei Huang
We present the first design and analysis of a solid-state Mamyshev oscillator. We utilize the phase-mismatched cascaded quadratic nonlinear process in a periodically poled lithium niobate waveguide to generate substantial spectral broadening for Mamyshev mode locking. The extensive spectral broadening bridges the two narrowband gain media in the two arms of the same cavity, leading to a broadband mode locking not attainable with either gain medium alone. Two pulses are coupled out of the cavity, and each of the output pulses carries a pulse energy of 25.3 nJ at a repetition rate of 100 MHz. The 10 dB bandwidth of 2.1 THz supports a transform-limited pulse duration of 322 fs, more than 5 times shorter than what can be achieved with either gain medium alone. Finally, effects of group velocity mismatch, group velocity dispersion, and nonlinear saturation on the performance of Mamyshev mode locking are numerically discussed in detail.We present the first design and analysis of a solid-state Mamyshev oscillator. We utilize the phase-mismatched cascaded quadratic nonlinear process in a periodically poled lithium niobate waveguide to generate substantial spectral broadening for Mamyshev mode locking. The extensive spectral broadening bridges the two narrowband gain media in the two arms of the same cavity, leading to a broadband mode locking not attainable with either gain medium alone. Two pulses are coupled out of the cavity, and each of the output pulses carries a pulse energy of 25.3 nJ at a repetition rate of 100 MHz. The 10 dB bandwidth of 2.1 THz supports a transform-limited pulse duration of 322 fs, more than 5 times shorter than what can be achieved with either gain medium alone. Finally, effects of group velocity mismatch, group velocity dispersion, and nonlinear saturation on the performance of Mamyshev mode locking are numerically discussed in detail..
Photonics Research
- Publication Date: Oct. 01, 2019
- Vol. 7, Issue 10, 1175 (2019)
Nanophotonics and Photonic Crystals
Coherent couplings between magnetic dipole transitions of quantum emitters and dielectric nanostructures
Qian Zhao, Zhong-Jian Yang, and Jun He
Here we study theoretically the optical responses of hybrid structures composed of dielectric nanostructures and quantum emitters with magnetic dipole transitions. Coherent couplings between magnetic dipole transitions and magnetic modes can occur, leading to giant modifications of the extinction spectra of the constituents in the hybrid structures. For a given hybrid structure, the extinction-cross-section spectra show linear or nonlinear behaviors depending on the strength of the excitation field. For a weak excitation, the extinction of the quantum emitters is greatly enhanced. The hybrid structure shows a dip on its extinction spectrum. For a strong excitation, the resonant extinction of the quantum emitters is weakly enhanced while the extinction spectrum is broadened obviously. The hybrid structure shows a Fano-like line shape on its extinction spectrum, which is different from that with a weak excitation. This difference is highly related to the behaviors of the magnetic polarizabilities of the quantum emitters in the hybrid structure. The optical responses of hybrid structures can be largely tuned by varying the geometric and material parameters.Here we study theoretically the optical responses of hybrid structures composed of dielectric nanostructures and quantum emitters with magnetic dipole transitions. Coherent couplings between magnetic dipole transitions and magnetic modes can occur, leading to giant modifications of the extinction spectra of the constituents in the hybrid structures. For a given hybrid structure, the extinction-cross-section spectra show linear or nonlinear behaviors depending on the strength of the excitation field. For a weak excitation, the extinction of the quantum emitters is greatly enhanced. The hybrid structure shows a dip on its extinction spectrum. For a strong excitation, the resonant extinction of the quantum emitters is weakly enhanced while the extinction spectrum is broadened obviously. The hybrid structure shows a Fano-like line shape on its extinction spectrum, which is different from that with a weak excitation. This difference is highly related to the behaviors of the magnetic polarizabilities of the quantum emitters in the hybrid structure. The optical responses of hybrid structures can be largely tuned by varying the geometric and material parameters..
Photonics Research
- Publication Date: Sep. 18, 2019
- Vol. 7, Issue 10, 1142 (2019)
Nonlinear Optics
Strong nonlinear optical effects in micro-confined atmospheric air
Benoit Debord, Martin Maurel, Frederic Gerome, Luca Vincetti... and Fetah Benabid|Show fewer author(s)
Historically, nonlinear optical phenomena such as spectral broadening by harmonic generation have been associated with crystals owing to their strong nonlinear refractive indices, which are in the range of ～10 14 cm2/W. This show moreHistorically, nonlinear optical phenomena such as spectral broadening by harmonic generation have been associated with crystals owing to their strong nonlinear refractive indices, which are in the range of
Photonics Research
- Publication Date: Sep. 18, 2019
- Vol. 7, Issue 10, 1134 (2019)
Optical and Photonic Materials
Direction controllable inverse transition radiation from the spatial dispersion in a graphene-dielectric stack
Sen Gong, Min Hu, Zhenhua Wu, Hang Pan... and Shenggang Liu|Show fewer author(s)
Transition radiation (TR) induced by electron–matter interaction usually demands vast accelerating voltages, and the radiation angle cannot be controlled. Here we present a mechanism of direction controllable inverse transition radiation (DCITR) in a graphene-dielectric stack excited by low-velocity electrons. The revealed mechanism shows that the induced hyperbolic-like spatial dispersion and the superposition of the individual bulk graphene plasmons (GPs) modes make the fields, which are supposed to be confined on the surface, radiate in the stack along a special radiation angle normal to the Poynting vector. By adjusting the chemical potential of the graphene sheets, the radiation angle can be controlled. And owing to the excitation of bulk GPs, only hundreds of volts for the accelerating voltage are required and the field intensity is dramatically enhanced compared with that of the normal TR. Furthermore, the presented mechanism can also be applied to the hyperbolic stack based on semiconductors in the infrared region as well as noble metals in the visible and ultraviolet region. Accordingly, the presented mechanism of DCITR is of great significance in particle detection, radiation emission, and so on.Transition radiation (TR) induced by electron–matter interaction usually demands vast accelerating voltages, and the radiation angle cannot be controlled. Here we present a mechanism of direction controllable inverse transition radiation (DCITR) in a graphene-dielectric stack excited by low-velocity electrons. The revealed mechanism shows that the induced hyperbolic-like spatial dispersion and the superposition of the individual bulk graphene plasmons (GPs) modes make the fields, which are supposed to be confined on the surface, radiate in the stack along a special radiation angle normal to the Poynting vector. By adjusting the chemical potential of the graphene sheets, the radiation angle can be controlled. And owing to the excitation of bulk GPs, only hundreds of volts for the accelerating voltage are required and the field intensity is dramatically enhanced compared with that of the normal TR. Furthermore, the presented mechanism can also be applied to the hyperbolic stack based on semiconductors in the infrared region as well as noble metals in the visible and ultraviolet region. Accordingly, the presented mechanism of DCITR is of great significance in particle detection, radiation emission, and so on..
Photonics Research
- Publication Date: Sep. 18, 2019
- Vol. 7, Issue 10, 1154 (2019)
Zeolite templated carbon nanodots for broadband ultrafast pulsed fiber laser generation
Xintong Xu, Jiaqi Chen, Wentao Shi, Dalin Sun... and Zikang Tang|Show fewer author(s)
Carbon nanodots (C-dots) with a uniform size of about 2 nm are synthesized via in situ pyrolysis of n-propylamine that is confined in the nanochannels of zeolite Linde Type A (LTA). The as-synthesized C-dots@LTA composite shows nonlinear optical saturable absorption properties in a broad wavelength band and can be used as saturable absorber (SA) to generate ultrafast pulsed fiber lasers. By inserting a zeolite LTA single crystal hosting C-dots into the fiber laser cavity, mode-locked fiber lasers with long-term operation stability at 1.5 μm and 1 μm are achieved. These results show that the C-dots@LTA are a promising SA material for ultrafast pulsed fiber laser generation in a broad wavelength band. To the best of our knowledge, this is the first demonstration of a C-dots@LTA-based mode-locked fiber laser.Carbon nanodots (C-dots) with a uniform size of about 2 nm are synthesized via in situ pyrolysis of n-propylamine that is confined in the nanochannels of zeolite Linde Type A (LTA). The as-synthesized C-dots@LTA composite shows nonlinear optical saturable absorption properties in a broad wavelength band and can be used as saturable absorber (SA) to generate ultrafast pulsed fiber lasers. By inserting a zeolite LTA single crystal hosting C-dots into the fiber laser cavity, mode-locked fiber lasers with long-term operation stability at 1.5 μm and 1 μm are achieved. These results show that the C-dots@LTA are a promising SA material for ultrafast pulsed fiber laser generation in a broad wavelength band. To the best of our knowledge, this is the first demonstration of a C-dots@LTA-based mode-locked fiber laser..
Photonics Research
- Publication Date: Oct. 01, 2019
- Vol. 7, Issue 10, 1182 (2019)
Broadband mid-infrared second harmonic generation using epitaxial polydomain barium titanate thin films | Editors' Pick
Junchao Zhou, Wenrui Zhang, Mingzhao Liu, and Pao Tai Lin
The mid-infrared (mid-IR) second-order optical nonlinearity of the barium titanate (BTO) thin films was characterized by second harmonic generation (SHG). The epitaxial BTO thin films were grown on strontium titanate substrates by pulsed-laser deposition. From the azimuthal-dependent polarized SHG measurements, the tensorial optical nonlinear coefficients, dij, and ferroelectric domain fraction ratio, δAY/δAz, were resolved. Strong SHG signals were obtained at the pumping laser wavelength λ between 3.0 and 3.6 μm. The SHG intensity was linearly dependent upon the square of the pumping laser power. The broadband mid-IR optical nonlinearity enables BTO thin films for applications in chip-scale quantum optics and nonlinear integrated photonic circuits.The mid-infrared (mid-IR) second-order optical nonlinearity of the barium titanate (BTO) thin films was characterized by second harmonic generation (SHG). The epitaxial BTO thin films were grown on strontium titanate substrates by pulsed-laser deposition. From the azimuthal-dependent polarized SHG measurements, the tensorial optical nonlinear coefficients,
Photonics Research
- Publication Date: Oct. 01, 2019
- Vol. 7, Issue 10, 1193 (2019)
Optoelectronics
Ultrafast and low-power optoelectronic infrared-to-visible upconversion devices
Zhao Shi, He Ding, Hao Hong, Dali Cheng... and Xing Sheng|Show fewer author(s)
Photon upconversion with transformation of low-energy photons to high-energy photons has been widely studied and especially applied in biomedicine for sensing, stimulation, and imaging. Conventional upconversion materials rely on nonlinear luminescence processes, suffering from long decay lifetime or high excitation power. Here, we present a microscale, optoelectronic infrared-to-visible upconversion device design that can be excited at low power (1–100 mW/cm2). By manipulating device geometry, illumination position, and temperature, the device luminescence decay lifetime can be tuned from tens to hundreds of nanoseconds. Based on carrier transportation and circuit dynamics, theoretical models are established to understand the transient behaviors. Compared with other mechanisms, the optoelectronic upconversion approach demonstrates the shortest luminescence lifetime with the lowest required excitation power, owing to its unique photon–electron conversion process. These features are expected to empower the device with essential capabilities for versatile applications as high-performance light emitters.Photon upconversion with transformation of low-energy photons to high-energy photons has been widely studied and especially applied in biomedicine for sensing, stimulation, and imaging. Conventional upconversion materials rely on nonlinear luminescence processes, suffering from long decay lifetime or high excitation power. Here, we present a microscale, optoelectronic infrared-to-visible upconversion device design that can be excited at low power (
Photonics Research
- Publication Date: Oct. 01, 2019
- Vol. 7, Issue 10, 1161 (2019)
Silicon Photonics
CMOS-compatible high-index doped silica waveguide with an embedded silicon-nanocrystal strip for all-optical analog-to-digital conversion | Editors' Pick
Yuhua Li, Kun Zhu, Zhe Kang, Wai Lok Ho... and Sai Tak Chu|Show fewer author(s)
Passive all-optical signal processors that overcome the electronic bottleneck can potentially be the enabling components for the next-generation high-speed and lower power consumption systems. Here, we propose and experimentashow morePassive all-optical signal processors that overcome the electronic bottleneck can potentially be the enabling components for the next-generation high-speed and lower power consumption systems. Here, we propose and experimentally demonstrate a CMOS-compatible waveguide and its application to the all-optical analog-to-digital converter (ADC) under the nonlinear spectral splitting and filtering scheme. As the key component of the proposed ADC, a 50 cm long high-index doped silica glass spiral waveguide is composed of a thin silicon-nanocrystal (Si-nc) layer embedded in the core center for enhanced nonlinearity. The device simultaneously possesses low loss (0.16 dB/cm at 1550 nm), large nonlinearity (
Photonics Research
- Publication Date: Oct. 01, 2019
- Vol. 7, Issue 10, 1200 (2019)
Surface Optics and Plasmonics
Plasmonic metasurface Luneburg lens
C. E. Garcia-Ortiz, R. Cortes, J. E. Gómez-Correa, E. Pisano... and V. Coello|Show fewer author(s)
We present a new design of a plasmonic Luneburg lens made from a gradient-index metasurface that was constructed with an array of nanometer-sized holes in a dielectric thin film. The fabricated structure consists of a planar lens with a diameter of 8.7 μm composed of a rectangular array of holes with a periodicity of 300 nm. The experimental characterization includes leakage-radiation microscopy imaging in the direction and frequency space. The former allows for characterization of the point spread function and phase distribution, whereas the latter grants access to qualitative measurements of the effective mode indices inside the plasmonic lens. The experimental results presented here are in good agreement with the expected average performance predicted by the numerical calculations. Nevertheless, the robustness of the characterization techniques presented here is also exploited to determine deviations from the design parameters.We present a new design of a plasmonic Luneburg lens made from a gradient-index metasurface that was constructed with an array of nanometer-sized holes in a dielectric thin film. The fabricated structure consists of a planar lens with a diameter of 8.7 μm composed of a rectangular array of holes with a periodicity of 300 nm. The experimental characterization includes leakage-radiation microscopy imaging in the direction and frequency space. The former allows for characterization of the point spread function and phase distribution, whereas the latter grants access to qualitative measurements of the effective mode indices inside the plasmonic lens. The experimental results presented here are in good agreement with the expected average performance predicted by the numerical calculations. Nevertheless, the robustness of the characterization techniques presented here is also exploited to determine deviations from the design parameters..
Photonics Research
- Publication Date: Sep. 04, 2019
- Vol. 7, Issue 10, 1112 (2019)
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