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2020
Volume: 8 Issue 10
17 Article(s)
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PEROVSKITE PHOTONICS
Two-step solvent post-treatment on PTAA for highly efficient and stable inverted perovskite solar cells
Yang Li, Chao Liang, Gaopeng Wang, Jielei Li, Shi Chen, Shihe Yang, Guichuan Xing, and Hui Pan
Modifying the surface of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) with toluene during the high-speed spin-coating process of dimethylformamide considerably improves the wettability and morphology of PTAA and results in improvement of the crystallinity and absorption of perovskite film. The hole mobility and ohm contact have also been improved accordingly. Combined with these improved parameters, inverted perovskite solar cells with high efficiency of 19.13% and long-term stability could be achieved, which are much better than those with untreated PTAA. Importantly, our devices can keep 88.4% of the initial power conversion efficiency after 30 days of storage in ambient air.
Modifying the surface of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) with toluene during the high-speed spin-coating process of dimethylformamide considerably improves the wettability and morphology of PTAA and results in improvement of the crystallinity and absorption of perovskite film. The hole mobility and ohm contact have also been improved accordingly. Combined with these improved parameters, inverted perovskite solar cells with high efficiency of 19.13% and long-term stability could be achieved, which are much better than those with untreated PTAA. Importantly, our devices can keep 88.4% of the initial power conversion efficiency after 30 days of storage in ambient air.
.Photonics Research
- Publication Date: Sep. 18, 2020
- Vol. 8, Issue 10, A39 (2020)
Exciton binding energy and effective mass of CsPbCl3: a magneto-optical study
Michal Baranowski, Paulina Plochocka, Rui Su, Laurent Legrand, Thierry Barisien, Frederick Bernardot, Qihua Xiong, Christophe Testelin, and Maria Chamarro
High magnetic field spectroscopy has been performed on lead chloride-based perovskite, a material that attracts significant interest for photovoltaic and photonic applications within the past decades. Optical properties being mainly driven by the exciton states, we have measured the fundamental parameters, such as the exciton binding energy, effective mass, and dielectric constant. Among the inorganic halide perovskites, CsPbCl3 owns the largest exciton binding energy and effective mass. This blue emitting compound has also been compared with lower band gap energy perovskites and other semiconducting phases, showing comparable band gap dependences for binding energy and Bohr radius.
High magnetic field spectroscopy has been performed on lead chloride-based perovskite, a material that attracts significant interest for photovoltaic and photonic applications within the past decades. Optical properties being mainly driven by the exciton states, we have measured the fundamental parameters, such as the exciton binding energy, effective mass, and dielectric constant. Among the inorganic halide perovskites,
Photonics Research
- Publication Date: Sep. 25, 2020
- Vol. 8, Issue 10, A50 (2020)
TOPOLOGICAL PHOTONICS AND BEYOND
Disorder-protected quantum state transmission through helical coupled-resonator waveguides
JungYun Han, Andrey A. Sukhorukov, and Daniel Leykam
We predict the preservation of temporal indistinguishability of photons propagating through helical coupled-resonator optical waveguides (H-CROWs). H-CROWs exhibit a pseudospin-momentum locked dispersion, which we show suppresses on-site disorder-induced backscattering and group velocity fluctuations. We simulate numerically the propagation of two-photon wave packets, demonstrating that they exhibit almost perfect Hong–Ou–Mandel dip visibility and then can preserve their quantum coherence even in the presence of moderate disorder, in contrast with regular CROWs, which are highly sensitive to disorder. As indistinguishability is the most fundamental resource of quantum information processing, H-CROWs may find applications for the implementation of robust optical links and delay lines in the emerging quantum photonic communication and computational platforms.
We predict the preservation of temporal indistinguishability of photons propagating through helical coupled-resonator optical waveguides (H-CROWs). H-CROWs exhibit a pseudospin-momentum locked dispersion, which we show suppresses on-site disorder-induced backscattering and group velocity fluctuations. We simulate numerically the propagation of two-photon wave packets, demonstrating that they exhibit almost perfect Hong–Ou–Mandel dip visibility and then can preserve their quantum coherence even in the presence of moderate disorder, in contrast with regular CROWs, which are highly sensitive to disorder. As indistinguishability is the most fundamental resource of quantum information processing, H-CROWs may find applications for the implementation of robust optical links and delay lines in the emerging quantum photonic communication and computational platforms.
.Photonics Research
- Publication Date: Sep. 28, 2020
- Vol. 8, Issue 10, B15 (2020)
Reviews
Fiber Optics and Optical Communications
High absorption large-mode area step-index fiber for tandem-pumped high-brightness high-power lasers
Kang-Jie Lim, Samuel Kai-Wen Seah, Joash Yong’En Ye, Wendy Weiying Lim, Chu-Perng Seah, Yunn-Boon Tan, Suting Tan, Huiting Lim, Raghuraman Sidharthan, Arumugam Rajendra Prasadh, Chen-Jian Chang, Seongwoo Yoo, and Song-Liang Chua
A short absorption length ytterbium (Yb)-doped large-mode area (LMA) fiber is presented as a step forward to mitigate the stern problem of nonlinear scatterings in a tandem pumping scheme adopted for high-power fiber laser. The short absorption length was realized by incorporating high Yb concentration in the fiber core. Furthermore, by replacing the inherent silica cladding with a Ge-doped cladding, we were able to obtain low core numerical aperture (NA) and negate the detrimental effect of index-raising by high Yb concentrations. This overcomes the long-standing limitation in step-index Yb-doped fibers (YDFs) where high cladding absorption inevitably results in high NA, thus hampering single-mode operation. We report an LMA (～575 μm2) YDF with NA of 0.04 and absorption of 27 dB/m at 976 nm—both traits promote power scaling of single-mode tandem pumped fiber lasers. To our knowledge, this is the highest cladding absorption attained in a low-NA step-index fiber to date. An all-fiber tandem-pumped amplifier was built using only ～14 m of the YDF. The amplifier delivered a near-Gaussian beam (M2～1.27) at 836 W output power (pump power limited) with a high slope efficiency of ～83%. Thanks to the short length and the tandem pumping, no indication of limiting factors such as stimulated Raman scattering, photodarkening, and transverse mode instability was observed.A short absorption length ytterbium (Yb)-doped large-mode area (LMA) fiber is presented as a step forward to mitigate the stern problem of nonlinear scatterings in a tandem pumping scheme adopted for high-power fiber laser. The short absorption length was realized by incorporating high Yb concentration in the fiber core. Furthermore, by replacing the inherent silica cladding with a Ge-doped cladding, we were able to obtain low core numerical aperture (NA) and negate the detrimental effect of index-raising by high Yb concentrations. This overcomes the long-standing limitation in step-index Yb-doped fibers (YDFs) where high cladding absorption inevitably results in high NA, thus hampering single-mode operation. We report an LMA (
Photonics Research
- Publication Date: Sep. 22, 2020
- Vol. 8, Issue 10, 1599 (2020)
Research Articles
Image Processing and Image Analysis
Learning-based phase imaging using a low-bit-depth pattern
Zhenyu Zhou, Jun Xia, Jun Wu, Chenliang Chang, Xi Ye, Shuguang Li, Bintao Du, Hao Zhang, and Guodong Tong
Phase imaging always deals with the problem of phase invisibility when capturing objects with existing light sensors. However, there is a demand for multiplane full intensity measurements and iterative propagation process or reliance on reference in most conventional approaches. In this paper, we present an end-to-end compressible phase imaging method based on deep neural networks, which can implement phase estimation using only binary measurements. A thin diffuser as a preprocessor is placed in front of the image sensor to implicitly encode the incoming wavefront information into the distortion and local variation of the generated speckles. Through the trained network, the phase profile of the object can be extracted from the discrete grains distributed in the low-bit-depth pattern. Our experiments demonstrate the faithful reconstruction with reasonable quality utilizing a single binary pattern and verify the high redundancy of the information in the intensity measurement for phase recovery. In addition to the advantages of efficiency and simplicity compared to now available imaging methods, our model provides significant compressibility for imaging data and can therefore facilitate the low-cost detection and efficient data transmission.Phase imaging always deals with the problem of phase invisibility when capturing objects with existing light sensors. However, there is a demand for multiplane full intensity measurements and iterative propagation process or reliance on reference in most conventional approaches. In this paper, we present an end-to-end compressible phase imaging method based on deep neural networks, which can implement phase estimation using only binary measurements. A thin diffuser as a preprocessor is placed in front of the image sensor to implicitly encode the incoming wavefront information into the distortion and local variation of the generated speckles. Through the trained network, the phase profile of the object can be extracted from the discrete grains distributed in the low-bit-depth pattern. Our experiments demonstrate the faithful reconstruction with reasonable quality utilizing a single binary pattern and verify the high redundancy of the information in the intensity measurement for phase recovery. In addition to the advantages of efficiency and simplicity compared to now available imaging methods, our model provides significant compressibility for imaging data and can therefore facilitate the low-cost detection and efficient data transmission..
Photonics Research
- Publication Date: Sep. 28, 2020
- Vol. 8, Issue 10, 1624 (2020)
Imaging Systems, Microscopy, and Displays
Design and analysis of extended depth of focus metalenses for achromatic computational imaging
Luocheng Huang, James Whitehead, Shane Colburn, and Arka Majumdar
Metasurface optics have demonstrated vast potential for implementing traditional optical components in an ultracompact and lightweight form factor. Metasurfaces, however, suffer from severe chromatic aberrations, posing serious limitations on their practical use. Existing approaches for circumventing this involving dispersion engineering are limited to small apertures and often entail multiple scatterers per unit cell with small feature sizes. Here, we present an alternative technique to mitigate chromatic aberration and demonstrate high-quality, full-color imaging using extended depth of focus (EDOF) metalenses and computational reconstruction. Previous EDOF metalenses have relied on cubic phase masks, where the image quality suffers from asymmetric artefacts. Here we demonstrate the use of rotationally symmetric masks, including logarithmic-aspherical, and shifted axicon masks, to mitigate this problem. Our work will inspire further development in achromatic metalenses beyond dispersion engineering and hybrid optical–digital metasurface systems.Metasurface optics have demonstrated vast potential for implementing traditional optical components in an ultracompact and lightweight form factor. Metasurfaces, however, suffer from severe chromatic aberrations, posing serious limitations on their practical use. Existing approaches for circumventing this involving dispersion engineering are limited to small apertures and often entail multiple scatterers per unit cell with small feature sizes. Here, we present an alternative technique to mitigate chromatic aberration and demonstrate high-quality, full-color imaging using extended depth of focus (EDOF) metalenses and computational reconstruction. Previous EDOF metalenses have relied on cubic phase masks, where the image quality suffers from asymmetric artefacts. Here we demonstrate the use of rotationally symmetric masks, including logarithmic-aspherical, and shifted axicon masks, to mitigate this problem. Our work will inspire further development in achromatic metalenses beyond dispersion engineering and hybrid optical–digital metasurface systems..
Photonics Research
- Publication Date: Sep. 25, 2020
- Vol. 8, Issue 10, 1613 (2020)
Integrated Optics
High-gain waveguide amplifiers in Si3N4 technology via double-layer monolithic integration | On the Cover
Jinfeng Mu, Meindert Dijkstra, Jeroen Korterik, Herman Offerhaus, and Sonia M. García-Blanco
Silicon nitride (Si3N4)-on-SiO2 attracts increasing interest in integrated photonics owing to its low propagation loss and wide transparency window, extending from ～400 nm to 2350 nm. Scalable integration of active devices such as amplifiers and lasers on the Si3N4 platform will enable applications requiring optical gain and a much-needed alternative to hybrid integration, which suffers from high cost and lack of high-volume manufacturability. We demonstrate a high-gain optical amplifier in Al2O3:Er3+ monolithically integrated on the Si3N4 platform using a double photonic layer approach. The device exhibits a net Si3N4-to-Si3N4 gain of 18.1±0.9 dB at 1532 nm, and a broadband gain operation over 70 nm covering wavelengths in the S-, C- and L-bands. This work shows that rare-earth-ion-doped materials and in particular, rare-earth-ion-doped Al2O3, can provide very high net amplification for the Si3N4 platform, paving the way to the development of different active devices monolithically integrated in this passive platform.Silicon nitride
Photonics Research
- Publication Date: Sep. 28, 2020
- Vol. 8, Issue 10, 1634 (2020)
Lasers and Laser Optics
Breathing dissipative soliton explosions in a bidirectional ultrafast fiber laser
Yi Zhou, Yu-Xuan Ren, Jiawei Shi, and Kenneth K. Y. Wong
Soliton explosions, among the most exotic dynamics, have been extensively studied on parameter invariant stationary solitons. However, the explosion dynamics are still largely unexplored in breathing dissipative solitons as a dynamic solution to many nonlinear systems. Here, we report on the first observation of a breathing dissipative soliton explosion in a net-normal-dispersion bidirectional ultrafast fiber laser. The breathing soliton explosions could be stimulated by the soliton buildup process or alteration of polarization settings. Transient breathing soliton pairs with intensive repulsion that is sensitive to initial conditions can also be triggered by multiple soliton explosions in the soliton buildup process instead of being triggered by varying polarization settings. The high behavior similarity also exists in the breathing soliton buildup and explosion process owing to the common gain and loss modulation. In addition, dissipative rogue waves were detected in the breathing soliton explosion, and the collision of breathing soliton significantly enhanced the amplitude of rogue waves, which is characteristic of the breathing solitons in a bidirectional fiber laser. These results shed new insights into complex dissipative soliton dynamics.Soliton explosions, among the most exotic dynamics, have been extensively studied on parameter invariant stationary solitons. However, the explosion dynamics are still largely unexplored in breathing dissipative solitons as a dynamic solution to many nonlinear systems. Here, we report on the first observation of a breathing dissipative soliton explosion in a net-normal-dispersion bidirectional ultrafast fiber laser. The breathing soliton explosions could be stimulated by the soliton buildup process or alteration of polarization settings. Transient breathing soliton pairs with intensive repulsion that is sensitive to initial conditions can also be triggered by multiple soliton explosions in the soliton buildup process instead of being triggered by varying polarization settings. The high behavior similarity also exists in the breathing soliton buildup and explosion process owing to the common gain and loss modulation. In addition, dissipative rogue waves were detected in the breathing soliton explosion, and the collision of breathing soliton significantly enhanced the amplitude of rogue waves, which is characteristic of the breathing solitons in a bidirectional fiber laser. These results shed new insights into complex dissipative soliton dynamics..
Photonics Research
- Publication Date: Sep. 15, 2020
- Vol. 8, Issue 10, 1566 (2020)
Extraction of internal phase motions in femtosecond soliton molecules using an orbital-angular-momentum-resolved method | Editors' Pick
Yuwei Zhao, Jintao Fan, Youjian Song, Uwe Morgner, and Minglie Hu
Internal motions in femtosecond soliton molecules provide insight into universal collective dynamics in various nonlinear systems. Here we introduce an orbital-angular-momentum (OAM)-resolved method that maps the relative phase motion within a femtosecond soliton molecule into the rotational movement of the interferometric beam profile of two optical vortices. By this means, long-term relative phase evolutions of doublet and triplet soliton molecules generated in an all-polarization-maintaining mode-locked Er-fiber laser are revealed. This simple and practical OAM-resolved method represents a promising way to directly visualize the complex phase dynamics in a diversity of multisoliton structures.Internal motions in femtosecond soliton molecules provide insight into universal collective dynamics in various nonlinear systems. Here we introduce an orbital-angular-momentum (OAM)-resolved method that maps the relative phase motion within a femtosecond soliton molecule into the rotational movement of the interferometric beam profile of two optical vortices. By this means, long-term relative phase evolutions of doublet and triplet soliton molecules generated in an all-polarization-maintaining mode-locked Er-fiber laser are revealed. This simple and practical OAM-resolved method represents a promising way to directly visualize the complex phase dynamics in a diversity of multisoliton structures..
Photonics Research
- Publication Date: Sep. 18, 2020
- Vol. 8, Issue 10, 1580 (2020)
Fast and wide-band tuning single-mode microlaser based on fiber Fabry–Pérot microcavities
Xin-Xia Gao, Jin-Ming Cui, Zhi-Hao Hu, Chun-Hua Dong, Jian Wang, Yun-Feng Huang, Chuan-Feng Li, and Guang-Can Guo
A narrow-linewidth laser operating at the telecommunications band combined with both fast and wide-band tuning features will have promising applications. Here we demonstrate a single-mode (both transverse and longitudinal mode) continuous microlaser around 1535 nm based on a fiber Fabry–Pérot microcavity, which achieves wide-band tuning without mode hopping to the 1.3 THz range and fast tuning rate to 60 kHz and yields a frequency scan rate of 1.6×1017 Hz/s. Moreover, the linewidth of the laser is measured as narrow as 3.1 MHz. As the microlaser combines all these features into one fiber component, it can serve as the seed laser for versatile applications in optical communication, sensing, frequency-modulated continuous-wave radar, and high-resolution imaging.A narrow-linewidth laser operating at the telecommunications band combined with both fast and wide-band tuning features will have promising applications. Here we demonstrate a single-mode (both transverse and longitudinal mode) continuous microlaser around 1535 nm based on a fiber Fabry–Pérot microcavity, which achieves wide-band tuning without mode hopping to the 1.3 THz range and fast tuning rate to 60 kHz and yields a frequency scan rate of
Photonics Research
- Publication Date: Sep. 29, 2020
- Vol. 8, Issue 10, 1642 (2020)
Nanophotonics and Photonic Crystals
Design of a multichannel photonic crystal dielectric laser accelerator
Zhexin Zhao, Dylan S. Black, R. Joel England, Tyler W. Hughes, Yu Miao, Olav Solgaard, Robert L. Byer, and Shanhui Fan
To be useful for most scientific and medical applications, compact particle accelerators will require much higher average current than enabled by current architectures. For this purpose, we propose a photonic crystal architecture for a dielectric laser accelerator, referred to as a multi-input multi-output silicon accelerator (MIMOSA), that enables simultaneous acceleration of multiple electron beams, increasing the total electron throughput by at least 1 order of magnitude. To achieve this, we show that the photonic crystal must support a mode at the Γ point in reciprocal space, with a normalized frequency equal to the normalized speed of the phase-matched electron. We show that the figure of merit of the MIMOSA can be inferred from the eigenmodes of the corresponding infinitely periodic structure, which provides a powerful approach to design such devices. Additionally, we extend the MIMOSA architecture to electron deflectors and other electron manipulation functionalities. These additional functionalities, combined with the increased electron throughput of these devices, permit all-optical on-chip manipulation of electron beams in a fully integrated architecture compatible with current fabrication technologies, which opens the way to unconventional electron beam shaping, imaging, and radiation generation.To be useful for most scientific and medical applications, compact particle accelerators will require much higher average current than enabled by current architectures. For this purpose, we propose a photonic crystal architecture for a dielectric laser accelerator, referred to as a multi-input multi-output silicon accelerator (MIMOSA), that enables simultaneous acceleration of multiple electron beams, increasing the total electron throughput by at least 1 order of magnitude. To achieve this, we show that the photonic crystal must support a mode at the
Photonics Research
- Publication Date: Sep. 21, 2020
- Vol. 8, Issue 10, 1586 (2020)
Optical and Photonic Materials
Room temperature synthesis of stable silica-coated CsPbBr3 quantum dots for amplified spontaneous emission
Qionghua Mo, Tongchao Shi, Wensi Cai, Shuangyi Zhao, Dongdong Yan, Juan Du, and Zhigang Zang
All-inorganic cesium lead bromide (CsPbBr3) perovskite quantum dots (QDs) with excellent optical properties have been regarded as good gain materials for amplified spontaneous emission (ASE). However, the poor stability as the results of the high sensitivity to heat and moisture limits their further applications. Here, we report a facile one-pot approach to synthesize CsPbBr3@SiO2 QDs at room temperature. Due to the effective defects passivation using SiO2, as-prepared CsPbBr3@SiO2 QDs present an enhanced photoluminescence quantum yield (PLQY) and chemical stability. The PLQY of CsPbBr3@SiO2 QDs reaches 71.6% which is higher than 46% in pure CsPbBr3 QDs. The PL intensity of CsPbBr3@SiO2 QDs maintains 84% while remaining 24% in pure CsPbBr3 after 80 min heating at 60°C. The ASE performance of the films is also studied under a two-photon-pumped laser. Compared with the films using pure CsPbBr3 QDs, those with as-prepared CsPbBr3@SiO2 QDs exhibit a reduced threshold of ASE. The work suggests that room-temperature-synthesized SiO2-coated perovskites QDs are promising candidates for laser devices.All-inorganic cesium lead bromide (
Photonics Research
- Publication Date: Sep. 22, 2020
- Vol. 8, Issue 10, 1605 (2020)
Optical Devices
Flexible microbubble-based Fabry–Pérot cavity for sensitive ultrasound detection and wide-view photoacoustic imaging
Jun Ma, Yang He, Xue Bai, Li-Peng Sun, Kai Chen, Kyunghwan Oh, and Bai-Ou Guan
Interaction of acoustic waves and microbubbles occurs in numerous biomedical applications including ultrasound imaging, drug delivery, lithotripsy treatment, and cell manipulation, wherein the acoustically driven microbubbles routinely act as active microscale oscillators or actuators. In contrast, microbubbles were utilized here as passive receivers to detect broadband ultrasound waves in aqueous environments. The microbubble was photothermally generated on a microstructured optical fiber (MOF) tip, forming a flexible Fabry–Pérot cavity whose gas–water interface was sensitive to ultrasound waves. The MOF severed as both a low-loss waveguide and a compact light condenser, allowing high-efficiency generation and stabilization of ultrasmall microbubbles. Integrated with all-fiber interferometry, a 10 μm diameter microbubble exhibited a low noise-equivalent pressure level of ～3.4 mPa/Hz1/2 and a broad bandwidth of ～0.8 MHz, capable of detecting weak ultrasounds emitted from red blood cells irradiated by pulsed laser light. With advantages of high sensitivity, compact size, and low cost, the microbubble-based ultrasound sensor has great potential in biomedical imaging and sensing applications.Interaction of acoustic waves and microbubbles occurs in numerous biomedical applications including ultrasound imaging, drug delivery, lithotripsy treatment, and cell manipulation, wherein the acoustically driven microbubbles routinely act as active microscale oscillators or actuators. In contrast, microbubbles were utilized here as passive receivers to detect broadband ultrasound waves in aqueous environments. The microbubble was photothermally generated on a microstructured optical fiber (MOF) tip, forming a flexible Fabry–Pérot cavity whose gas–water interface was sensitive to ultrasound waves. The MOF severed as both a low-loss waveguide and a compact light condenser, allowing high-efficiency generation and stabilization of ultrasmall microbubbles. Integrated with all-fiber interferometry, a 10 μm diameter microbubble exhibited a low noise-equivalent pressure level of
Photonics Research
- Publication Date: Sep. 10, 2020
- Vol. 8, Issue 10, 1558 (2020)
Quantum Optics
Quantum-enhanced stochastic phase estimation with the SU(1,1) interferometer
Kaimin Zheng, Minghao Mi, Ben Wang, Liang Xu, Liyun Hu, Shengshuai Liu, Yanbo Lou, Jietai Jing, and Lijian Zhang
Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters. Similar to the estimation of a constant phase, there is a standard quantum limit for stochastic phase estimation, which can be obtained with the Mach–Zehnder interferometer and coherent input state. Recently, it has been shown that the stochastic standard quantum limit can be surpassed with nonclassical resources such as squeezed light. However, practical methods to achieve quantum enhancement in the stochastic phase estimation remain largely unexplored. Here we propose a method utilizing the SU(1,1) interferometer and coherent input states to estimate a stochastic optical phase. As an example, we investigate the Ornstein–Uhlenback stochastic phase. We analyze the performance of this method for three key estimation problems: prediction, tracking, and smoothing. The results show significant reduction of the mean square error compared with the Mach–Zehnder interferometer under the same photon number flux inside the interferometers. In particular, we show that the method with the SU(1,1) interferometer can achieve fundamental quantum scaling, achieve stochastic Heisenberg scaling, and surpass the precision of the canonical measurement.Quantum stochastic phase estimation has many applications in the precise measurement of various physical parameters. Similar to the estimation of a constant phase, there is a standard quantum limit for stochastic phase estimation, which can be obtained with the Mach–Zehnder interferometer and coherent input state. Recently, it has been shown that the stochastic standard quantum limit can be surpassed with nonclassical resources such as squeezed light. However, practical methods to achieve quantum enhancement in the stochastic phase estimation remain largely unexplored. Here we propose a method utilizing the SU(1,1) interferometer and coherent input states to estimate a stochastic optical phase. As an example, we investigate the Ornstein–Uhlenback stochastic phase. We analyze the performance of this method for three key estimation problems: prediction, tracking, and smoothing. The results show significant reduction of the mean square error compared with the Mach–Zehnder interferometer under the same photon number flux inside the interferometers. In particular, we show that the method with the SU(1,1) interferometer can achieve fundamental quantum scaling, achieve stochastic Heisenberg scaling, and surpass the precision of the canonical measurement..
Photonics Research
- Publication Date: Sep. 29, 2020
- Vol. 8, Issue 10, 1653 (2020)
Silicon Photonics
Widely tunable, heterogeneously integrated quantum-dot O-band lasers on silicon | Spotlight on Optics
Aditya Malik, Joel Guo, Minh A. Tran, Geza Kurczveil, Di Liang, and John E. Bowers
Heterogeneously integrated lasers in the O-band are a key component in realizing low-power optical interconnects for data centers and high-performance computing. Quantum-dot-based materials have been particularly appealing for light generation due to their ultralow lasing thresholds, small linewidth enhancement factor, and low sensitivity to reflections. Here, we present widely tunable quantum-dot lasers heterogeneously integrated on silicon-on-insulator substrate. The tuning mechanism is based on Vernier dual-ring geometry, and a 47 nm tuning range with 52 dB side-mode suppression ratio is observed. These parameters show an increase to 52 nm and 58 dB, respectively, when an additional wavelength filter in the form of a Mach–Zehnder interferometer is added to the cavity. The Lorentzian linewidth of the lasers is measured as low as 5.3 kHz.Heterogeneously integrated lasers in the O-band are a key component in realizing low-power optical interconnects for data centers and high-performance computing. Quantum-dot-based materials have been particularly appealing for light generation due to their ultralow lasing thresholds, small linewidth enhancement factor, and low sensitivity to reflections. Here, we present widely tunable quantum-dot lasers heterogeneously integrated on silicon-on-insulator substrate. The tuning mechanism is based on Vernier dual-ring geometry, and a 47 nm tuning range with 52 dB side-mode suppression ratio is observed. These parameters show an increase to 52 nm and 58 dB, respectively, when an additional wavelength filter in the form of a Mach–Zehnder interferometer is added to the cavity. The Lorentzian linewidth of the lasers is measured as low as 5.3 kHz..
Photonics Research
- Publication Date: Sep. 10, 2020
- Vol. 8, Issue 10, 1551 (2020)
56 Gbps high-speed Ge electro-absorption modulator
Zhi Liu, Xiuli Li, Chaoqun Niu, Jun Zheng, Chunlai Xue, Yuhua Zuo, and Buwen Cheng
A high-speed evanescent-coupled Ge waveguide electro-absorption modulator (EAM) with simple fabrication processes was realized on a silicon-on-insulator platform with a 220 nm top Si layer. Selectively grown Ge with a triangle shape was directly used for Ge waveguides of the EAM. An asymmetric p-i-n junction was designed in the Ge waveguide to provide a strong electric field for Franz–Keldysh effect. The insertion loss of the Ge EAM was 6.2 dB at 1610 nm. The EAM showed the high electro-optic bandwidth of 36 GHz at -1 V. Clear open 56 Gbps eye diagrams were observed at 1610 nm with a dynamic extinction ratio of 2.7 dB and dynamic power consumption of 45 fJ/bit for voltage swing of 3Vpp.A high-speed evanescent-coupled Ge waveguide electro-absorption modulator (EAM) with simple fabrication processes was realized on a silicon-on-insulator platform with a 220 nm top Si layer. Selectively grown Ge with a triangle shape was directly used for Ge waveguides of the EAM. An asymmetric p-i-n junction was designed in the Ge waveguide to provide a strong electric field for Franz–Keldysh effect. The insertion loss of the Ge EAM was 6.2 dB at 1610 nm. The EAM showed the high electro-optic bandwidth of 36 GHz at
Photonics Research
- Publication Date: Sep. 29, 2020
- Vol. 8, Issue 10, 1648 (2020)
Surface Optics and Plasmonics
Strong optical force of a molecule enabled by the plasmonic nanogap hot spot in a tip-enhanced Raman spectroscopy system
Li Long, Jianfeng Chen, Huakang Yu, and Zhi-Yuan Li
Tip-enhanced Raman spectroscopy (TERS) offers a powerful means to enhance the Raman scattering signal of a molecule as the localized surface plasmonic resonance will induce a significant local electric field enhancement in the nanoscale hot spot located within the nanogap of the TERS system. In this work, we theoretically show that this nanoscale hot spot can also serve as powerful optical tweezers to tightly trap a molecule. We calculate and analyze the local electric field and field gradient distribution of this nanogap plasmon hot spot. Due to the highly localized electric field, a three-dimensional optical trap can form at the hot spot. Moreover, the optical energy density and optical force acting on a molecule can be greatly enhanced to a level far exceeding the conventional single laser beam optical tweezers. Calculations show that for a single H2TBPP organic molecule, which is modeled as a spherical molecule with a radius of rm=1 nm, a dielectric coefficient ε=3, and a polarizability α=4.5×10-38 C·m2/V, the stiffness of the hot-spot trap can reach a high value of about 2 pN/[(W/cm2)·m] and 40 pN/[(W/cm2)·m] in the direction perpendicular and parallel to the TERS tip axis, which is far larger than the stiffness of single-beam tweezers, ～0.4 pN/[(W/cm2)·m]. This hard-stiffness will enable the molecules to be stably captured in the plasmon hot spot. Our results indicate that TERS can become a promising tool of optical tweezers for trapping a microscopic object like molecules while implementing Raman spectroscopic imaging and analysis at the same time.Tip-enhanced Raman spectroscopy (TERS) offers a powerful means to enhance the Raman scattering signal of a molecule as the localized surface plasmonic resonance will induce a significant local electric field enhancement in the nanoscale hot spot located within the nanogap of the TERS system. In this work, we theoretically show that this nanoscale hot spot can also serve as powerful optical tweezers to tightly trap a molecule. We calculate and analyze the local electric field and field gradient distribution of this nanogap plasmon hot spot. Due to the highly localized electric field, a three-dimensional optical trap can form at the hot spot. Moreover, the optical energy density and optical force acting on a molecule can be greatly enhanced to a level far exceeding the conventional single laser beam optical tweezers. Calculations show that for a single
Photonics Research
- Publication Date: Sep. 18, 2020
- Vol. 8, Issue 10, 1573 (2020)
About the Cover
Wafer-scale monolithically integrated optical waveguide amplifier die via double-layer active-passive platform in the silicon nitride technology.
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