Optical frequency combs, which consist of precisely controlled spectral lines covering a wide range, have played a crucial role in enabling numerous scientific advancements. Beyond the conventional approach that relies on mode-locked lasers, microcombs generated from microresonators pumped at a single frequency have arguably given rise to a new field within cavity nonlinear photonics, which has led to a robust exchange of ideas and research between theoretical, experimental, and technological aspects. Microcombs are extremely attractive in applications requiring a compact footprint, low cost, good energy efficiency, large comb spacing, and access to nonconventional spectral regions. The recently arising microcombs based on fiber Fabry–Pérot microresonators provide unique opportunities for ultralow noise and high-dimensional nonlinear optics. In this review, we comprehensively examine the recent progress of fiber Kerr microcombs and discuss how various phenomena in fibers can be utilized to enhance the microcomb performances that benefit a plethora of applications.
{"title":"Microcombs in fiber Fabry–Pérot cavities","authors":"Jonathan Musgrave, Shu-Wei Huang, Mingming Nie","doi":"10.1063/5.0177134","DOIUrl":"https://doi.org/10.1063/5.0177134","url":null,"abstract":"Optical frequency combs, which consist of precisely controlled spectral lines covering a wide range, have played a crucial role in enabling numerous scientific advancements. Beyond the conventional approach that relies on mode-locked lasers, microcombs generated from microresonators pumped at a single frequency have arguably given rise to a new field within cavity nonlinear photonics, which has led to a robust exchange of ideas and research between theoretical, experimental, and technological aspects. Microcombs are extremely attractive in applications requiring a compact footprint, low cost, good energy efficiency, large comb spacing, and access to nonconventional spectral regions. The recently arising microcombs based on fiber Fabry–Pérot microresonators provide unique opportunities for ultralow noise and high-dimensional nonlinear optics. In this review, we comprehensively examine the recent progress of fiber Kerr microcombs and discuss how various phenomena in fibers can be utilized to enhance the microcomb performances that benefit a plethora of applications.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"1 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138558457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jie Zhao, Xiaoting Li, Ting-Chen Hu, Ayed Al Sayem, Haochuan Li, Alaric Tate, Kwangwoong Kim, Rose Kopf, Pouria Sanjari, Mark Earnshaw, Nicolas K. Fontaine, Cheng Wang, Andrea Blanco-Redondo
Thin-film lithium niobate (TFLN) based frequency doublers have widely been recognized as an essential component for both classical and quantum optical communications. Nonetheless, the efficiency (unit: %/W) of these devices is hindered by imperfections present in the quasi-phase matching (QPM) spectrum. In this report, we present a thorough experimental study of spectral imperfections in TFLN frequency doublers with varying lengths, ranging from 5 to 15 mm. A non-destructive diagnostic method based on scattered light imaging is proposed and employed to identify the waveguide sections and primary waveguide parameters contributing to the imperfections in the QPM spectrum. By applying this method, we obtain the evolution of the QPM spectrum along the waveguide’s length. Correlating this information with the measurements of the relevant geometric parameters along the waveguides suggests that the TFLN film thickness variation is the primary source for the measured spectral distortions. Furthermore, we numerically reproduce the QPM spectra with the mapped TFLN film thickness across the entire waveguiding regions. These findings align with and complement the simulation results from previous numerical studies, providing further evidence of the effectiveness of the developed diagnostic method. This comprehensive investigation offers valuable insights into the identification and mitigation of spectral imperfections in TFLN-based frequency doublers, paving the way for the realization of nonlinear optical devices with enhanced efficiency and improved spectral fidelity.
{"title":"Unveiling the origins of quasi-phase matching spectral imperfections in thin-film lithium niobate frequency doublers","authors":"Jie Zhao, Xiaoting Li, Ting-Chen Hu, Ayed Al Sayem, Haochuan Li, Alaric Tate, Kwangwoong Kim, Rose Kopf, Pouria Sanjari, Mark Earnshaw, Nicolas K. Fontaine, Cheng Wang, Andrea Blanco-Redondo","doi":"10.1063/5.0171106","DOIUrl":"https://doi.org/10.1063/5.0171106","url":null,"abstract":"Thin-film lithium niobate (TFLN) based frequency doublers have widely been recognized as an essential component for both classical and quantum optical communications. Nonetheless, the efficiency (unit: %/W) of these devices is hindered by imperfections present in the quasi-phase matching (QPM) spectrum. In this report, we present a thorough experimental study of spectral imperfections in TFLN frequency doublers with varying lengths, ranging from 5 to 15 mm. A non-destructive diagnostic method based on scattered light imaging is proposed and employed to identify the waveguide sections and primary waveguide parameters contributing to the imperfections in the QPM spectrum. By applying this method, we obtain the evolution of the QPM spectrum along the waveguide’s length. Correlating this information with the measurements of the relevant geometric parameters along the waveguides suggests that the TFLN film thickness variation is the primary source for the measured spectral distortions. Furthermore, we numerically reproduce the QPM spectra with the mapped TFLN film thickness across the entire waveguiding regions. These findings align with and complement the simulation results from previous numerical studies, providing further evidence of the effectiveness of the developed diagnostic method. This comprehensive investigation offers valuable insights into the identification and mitigation of spectral imperfections in TFLN-based frequency doublers, paving the way for the realization of nonlinear optical devices with enhanced efficiency and improved spectral fidelity.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"33 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138548259","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alon Bernstein, Elad Zehavi, Yosef London, Mirit Hen, Rafael Suna, Shai Ben-Ami, Avi Zadok
Forward Brillouin scattering fiber sensors can detect and analyze media outside the cladding of standard fibers, where guided light does not reach. Nearly all such sensors reported to-date have relied on the radially symmetric guided acoustic modes of the fiber. Wave motion in these modes is strictly dilatational. However, forward Brillouin scattering also takes place through torsional–radial guided acoustic modes of the fiber. Torsional–radial modes exhibit more complex tensor characteristics, and they consist of both dilatational and shear wave contributions. In this work, we show that forward Brillouin sensing through torsional–radial acoustic modes is qualitatively different from processes based on the radial ones. While dilatational wave components may dissipate toward liquids outside the fiber cladding, shear waves do not. Consequently, the effect of outside liquids varies among torsional–radial modes. Those modes that are dominated by their dilatational components undergo faster decay rates, whereas other modes with large shear contributions decay at much slower rates in the same liquid. The difference in decay rates may reach a factor of seven. Experimental observations are well supported by the analysis. The differences among modes are also found with liquid outside specific coating layers. Large changes in decay rates are observed when a phase transition between solid and liquid occurs outside the cladding boundary. The monitoring of multiple mode categories provides more complete assessment of outside media and enhances the capabilities of forward Brillouin scattering fiber sensors.
{"title":"Tensor characteristics of forward Brillouin sensors in bare and coated fibers","authors":"Alon Bernstein, Elad Zehavi, Yosef London, Mirit Hen, Rafael Suna, Shai Ben-Ami, Avi Zadok","doi":"10.1063/5.0169789","DOIUrl":"https://doi.org/10.1063/5.0169789","url":null,"abstract":"Forward Brillouin scattering fiber sensors can detect and analyze media outside the cladding of standard fibers, where guided light does not reach. Nearly all such sensors reported to-date have relied on the radially symmetric guided acoustic modes of the fiber. Wave motion in these modes is strictly dilatational. However, forward Brillouin scattering also takes place through torsional–radial guided acoustic modes of the fiber. Torsional–radial modes exhibit more complex tensor characteristics, and they consist of both dilatational and shear wave contributions. In this work, we show that forward Brillouin sensing through torsional–radial acoustic modes is qualitatively different from processes based on the radial ones. While dilatational wave components may dissipate toward liquids outside the fiber cladding, shear waves do not. Consequently, the effect of outside liquids varies among torsional–radial modes. Those modes that are dominated by their dilatational components undergo faster decay rates, whereas other modes with large shear contributions decay at much slower rates in the same liquid. The difference in decay rates may reach a factor of seven. Experimental observations are well supported by the analysis. The differences among modes are also found with liquid outside specific coating layers. Large changes in decay rates are observed when a phase transition between solid and liquid occurs outside the cladding boundary. The monitoring of multiple mode categories provides more complete assessment of outside media and enhances the capabilities of forward Brillouin scattering fiber sensors.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"55 5","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138523788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Within Reststrahlen bands of polar semiconductors, surface phonon–plasmon coupling is of great interest in infrared nanophotonics. Here, we demonstrate an active long-wavelength infrared device of graphene integrated with an AlN/SiC polar heterostructure. As a low-loss dielectric design, the subwavelength structure device takes advantage of interfacial photogating effect on electrostatic doping of the graphene and the interfaced SiC, and the tunable spectral behavior is originated from the hybridization of the doping-dependent surface phonon–plasmon resonances. This finding provides a steady-state manipulating method to the surface modes for the low-loss nanophotonic devices on SiC platform, and the graphene Fermi level tunable to cross the Dirac point in a steady response even makes the intrinsic graphene photodetectors feasible.
{"title":"Tunable infrared surface phonon–plasmon coupling in graphene-integrated polar semiconductor heterostructure","authors":"Ye Zhang, Xiangyu Gao, Hui Xia, Junjie Mei, Zihui Cui, Jianjun Lai, Changhong Chen","doi":"10.1063/5.0169414","DOIUrl":"https://doi.org/10.1063/5.0169414","url":null,"abstract":"Within Reststrahlen bands of polar semiconductors, surface phonon–plasmon coupling is of great interest in infrared nanophotonics. Here, we demonstrate an active long-wavelength infrared device of graphene integrated with an AlN/SiC polar heterostructure. As a low-loss dielectric design, the subwavelength structure device takes advantage of interfacial photogating effect on electrostatic doping of the graphene and the interfaced SiC, and the tunable spectral behavior is originated from the hybridization of the doping-dependent surface phonon–plasmon resonances. This finding provides a steady-state manipulating method to the surface modes for the low-loss nanophotonic devices on SiC platform, and the graphene Fermi level tunable to cross the Dirac point in a steady response even makes the intrinsic graphene photodetectors feasible.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"26 2","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138523798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chiroptical signals, including optical rotation (OR) and circular dichroism (CD), are widely utilized as potent probes for investigating the structure and properties of chiral molecules. However, acquiring both coexisting weak OR and CD signals simultaneously in a single measurement process with a high precision remains a challenge for conventional setups. In this article, a high-precision yet easy-to-set-up method for simultaneous detection of OR and CD signals based on weak measurement is theoretically and experimentally demonstrated. In addition, the chiroptical signals are detected using two new intensity-contrast-ratio pointers, which provide an expanded measurement range compared with the shift of the mean value pointer. The proposed method has been validated through a spin Hall effect light based experiment, with precision reaching the order of 10−7 and 10−6 rad for the detection of OR and CD, respectively. These results may serve as a catalyst for further studies of fast, multi-parameter biosensing technologies with ultra-precision.
{"title":"Complete chiroptical signal detection using weak measurement with intensity-contrast-ratio pointers","authors":"Yunhan Wang, Shaojie Yang, Qianli Zhang, Yanyu Chen, Xiaolong Hu, Hong Zhang, Zhiyou Zhang","doi":"10.1063/5.0164781","DOIUrl":"https://doi.org/10.1063/5.0164781","url":null,"abstract":"Chiroptical signals, including optical rotation (OR) and circular dichroism (CD), are widely utilized as potent probes for investigating the structure and properties of chiral molecules. However, acquiring both coexisting weak OR and CD signals simultaneously in a single measurement process with a high precision remains a challenge for conventional setups. In this article, a high-precision yet easy-to-set-up method for simultaneous detection of OR and CD signals based on weak measurement is theoretically and experimentally demonstrated. In addition, the chiroptical signals are detected using two new intensity-contrast-ratio pointers, which provide an expanded measurement range compared with the shift of the mean value pointer. The proposed method has been validated through a spin Hall effect light based experiment, with precision reaching the order of 10−7 and 10−6 rad for the detection of OR and CD, respectively. These results may serve as a catalyst for further studies of fast, multi-parameter biosensing technologies with ultra-precision.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"62 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138523801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Structured photons are a crucial resource in both classical and quantum technologies, particularly in spin–orbit hybrid photons, enabling various practical applications ranging from ultra-sensitive metrology techniques to quantum-enhanced information processing tasks. However, the two-photon interference of spin–orbit hybrid photons, which combines polarization modes and complex transverse spatial structures across the beam profile, remains unexplored. Here, we present an experimental observation of Hong–Ou–Mandel (HOM) interference of spin–orbit hybrid photons. The tunable q-plates that work as spin–orbit coupler devices are used to prepare various forms of spin–orbit hybrid entangled photons. By harnessing the match degree in the temporal domain, the coalescence and anti-coalescence effects resulting from the symmetric and anti-symmetric properties of the incident quantum states are observed. Moreover, we demonstrated the feasibility of quantum-enhanced photon polarization gears through HOM interference and theoretically analyze the noise-resilient advantages based on coherent HOM measurements. These results provide an alternative route toward quantum experiments with structured photons that allows for controlling their quantum interference in a compact, stable, and efficient way.
{"title":"Hong–Ou–Mandel interference of spin–orbit hybrid entangled photons","authors":"Ling Hong, Xiyue Cao, Yuanyuan Chen, Lixiang Chen","doi":"10.1063/5.0167016","DOIUrl":"https://doi.org/10.1063/5.0167016","url":null,"abstract":"Structured photons are a crucial resource in both classical and quantum technologies, particularly in spin–orbit hybrid photons, enabling various practical applications ranging from ultra-sensitive metrology techniques to quantum-enhanced information processing tasks. However, the two-photon interference of spin–orbit hybrid photons, which combines polarization modes and complex transverse spatial structures across the beam profile, remains unexplored. Here, we present an experimental observation of Hong–Ou–Mandel (HOM) interference of spin–orbit hybrid photons. The tunable q-plates that work as spin–orbit coupler devices are used to prepare various forms of spin–orbit hybrid entangled photons. By harnessing the match degree in the temporal domain, the coalescence and anti-coalescence effects resulting from the symmetric and anti-symmetric properties of the incident quantum states are observed. Moreover, we demonstrated the feasibility of quantum-enhanced photon polarization gears through HOM interference and theoretically analyze the noise-resilient advantages based on coherent HOM measurements. These results provide an alternative route toward quantum experiments with structured photons that allows for controlling their quantum interference in a compact, stable, and efficient way.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"18 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138523784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jiaqi Zhang, Yuji Kosugi, Makoto Ogasawara, Koto Ariu, A. Otomo, Toshiki Yamada, Y. Nakano, Takuo Tanemura
Free-space electro-optic (EO) modulators operating at gigahertz and beyond are attractive for a wide range of emerging applications, including high-speed imaging, free-space optical communication, microwave photonics, and diffractive computing. Here, we experimentally demonstrate a high-speed plasmonic metasurface EO modulator operating in a near-infrared wavelength range with a gigahertz modulation bandwidth. To achieve efficient intensity modulation of reflected light from an ultrathin metasurface layer, we utilize the bimodal plasmonic resonance inside a subwavelength metal–insulator–metal grating, which is precisely tuned to satisfy the critical coupling condition. As a result, perfect absorption of −27 dB (99.8%) and a high quality (Q) factor of 113 are obtained at a resonant wavelength of 1650 nm. By incorporating an EO polymer inside the grating, we achieve a modulation depth of up to 9.5 dB under an applied voltage of ±30 V. The 3-dB modulation bandwidth is confirmed to be 1.25 GHz, which is primarily limited by the undesired contact resistance and the output impedance of the driver. Owing to the high electrical conductivity of metallic gratings and a compact device structure with a minimal parasitic capacitance, the demonstrated device can potentially operate at several tens of gigahertz, which opens up exciting opportunities for ultrahigh-speed active metasurface devices in various applications.
自由空间光电（EO）调制器的工作频率可达千兆赫兹或更高，对高速成像、自由空间光通信、微波光子学和衍射计算等各种新兴应用具有吸引力。在这里，我们通过实验展示了一种在近红外波长范围内工作、具有千兆赫调制带宽的高速等离子体元表面 EO 调制器。为了实现对超薄超表面层反射光的高效强度调制，我们利用了亚波长金属-绝缘体-金属光栅内的双模质子共振，并对其进行了精确调谐以满足临界耦合条件。因此，在共振波长为 1650 nm 时，可获得 -27 dB（99.8%）的完美吸收和 113 的高质量（Q）因子。通过在光栅内加入环氧乙烷聚合物，我们在±30 V 的外加电压下实现了高达 9.5 dB 的调制深度。经证实，3 dB 调制带宽为 1.25 GHz，这主要受到非预期接触电阻和驱动器输出阻抗的限制。由于金属光栅的高导电性和寄生电容极小的紧凑型器件结构，所演示的器件有可能在几十千兆赫的频率下工作，这为超高速有源元表面器件在各种应用中的发展提供了令人兴奋的机会。
{"title":"High-speed metasurface modulator using perfectly absorptive bimodal plasmonic resonance","authors":"Jiaqi Zhang, Yuji Kosugi, Makoto Ogasawara, Koto Ariu, A. Otomo, Toshiki Yamada, Y. Nakano, Takuo Tanemura","doi":"10.1063/5.0173216","DOIUrl":"https://doi.org/10.1063/5.0173216","url":null,"abstract":"Free-space electro-optic (EO) modulators operating at gigahertz and beyond are attractive for a wide range of emerging applications, including high-speed imaging, free-space optical communication, microwave photonics, and diffractive computing. Here, we experimentally demonstrate a high-speed plasmonic metasurface EO modulator operating in a near-infrared wavelength range with a gigahertz modulation bandwidth. To achieve efficient intensity modulation of reflected light from an ultrathin metasurface layer, we utilize the bimodal plasmonic resonance inside a subwavelength metal–insulator–metal grating, which is precisely tuned to satisfy the critical coupling condition. As a result, perfect absorption of −27 dB (99.8%) and a high quality (Q) factor of 113 are obtained at a resonant wavelength of 1650 nm. By incorporating an EO polymer inside the grating, we achieve a modulation depth of up to 9.5 dB under an applied voltage of ±30 V. The 3-dB modulation bandwidth is confirmed to be 1.25 GHz, which is primarily limited by the undesired contact resistance and the output impedance of the driver. Owing to the high electrical conductivity of metallic gratings and a compact device structure with a minimal parasitic capacitance, the demonstrated device can potentially operate at several tens of gigahertz, which opens up exciting opportunities for ultrahigh-speed active metasurface devices in various applications.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"20 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139019786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ziyi Tang, Zhenyu Wan, Han Cao, Yize Liang, Wei Zhou, Yuchen Zhang, Liang Fang, Jian Wang
Recently, the rotational Doppler effect has attracted broad attention in detecting rotational motion. However, the presently proposed detection techniques based on the rotational Doppler effect are generally configured relying on discrete components in free space, resulting in cumbersome and inflexible systems, which brings challenges to practical applications. In this paper, we demonstrate a fiber-based configuration on rotational Doppler measurements for the detection of a rotational object using an ultra-broadband mode-selective coupler to convert the superposed vortices. Remarkably, the results show the broadband operating range of the fiber-based measurement system intuitively through wavelength scanning. The refinement of rotational Doppler detection techniques is of great significance for lowering the cost, reducing system complexity, improving system integration, and industrial manufacturing. This fiber-based scheme might be a promising candidate for facilitating the rotational Doppler effect applied as novel motion monitoring and sensing equipment in engineering and industry.
{"title":"Fiber-based broadband detection of a rotational object with superposed vortices","authors":"Ziyi Tang, Zhenyu Wan, Han Cao, Yize Liang, Wei Zhou, Yuchen Zhang, Liang Fang, Jian Wang","doi":"10.1063/5.0167478","DOIUrl":"https://doi.org/10.1063/5.0167478","url":null,"abstract":"Recently, the rotational Doppler effect has attracted broad attention in detecting rotational motion. However, the presently proposed detection techniques based on the rotational Doppler effect are generally configured relying on discrete components in free space, resulting in cumbersome and inflexible systems, which brings challenges to practical applications. In this paper, we demonstrate a fiber-based configuration on rotational Doppler measurements for the detection of a rotational object using an ultra-broadband mode-selective coupler to convert the superposed vortices. Remarkably, the results show the broadband operating range of the fiber-based measurement system intuitively through wavelength scanning. The refinement of rotational Doppler detection techniques is of great significance for lowering the cost, reducing system complexity, improving system integration, and industrial manufacturing. This fiber-based scheme might be a promising candidate for facilitating the rotational Doppler effect applied as novel motion monitoring and sensing equipment in engineering and industry.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"141 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138523793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Ashtiani, M. H. Idjadi, T. C. Hu, S. Grillanda, D. Neilson, M. Earnshaw, M. Cappuzzo, R. Kopf, A. Tate, A. Blanco-Redondo
Optical neural networks (ONNs) enable high speed, parallel, and energy efficient processing compared to their conventional digital electronic counterparts. However, realizing large scale ONN systems is an open problem. Among various integrated and non-integrated ONNs, free-space diffractive ONNs benefit from a large number of pixels of spatial light modulators to realize millions of neurons. However, a significant fraction of computation time and energy is consumed by the nonlinear activation function that is typically implemented using a camera sensor. Here, we propose a novel surface-normal photodetector (SNPD) with an optical-in–electrical-out (O–E) nonlinear response to replace the camera sensor that enables about three orders of magnitude faster (5.7 µs response time) and more energy efficient (less than 10 nW/pixel) response. Direct efficient vertical optical coupling, polarization insensitivity, inherent nonlinearity with no control electronics, low optical power requirements, and the possibility of implementing large scale arrays make the SNPD a promising O–E nonlinear activation function for diffractive ONNs. To show the applicability of the proposed neural nonlinearity, successful classification simulations of the MNIST and Fashion MNIST datasets using the measured response of SNPD with accuracy comparable to that of an ideal ReLU function are demonstrated.
{"title":"A surface-normal photodetector as nonlinear activation function in diffractive optical neural networks","authors":"F. Ashtiani, M. H. Idjadi, T. C. Hu, S. Grillanda, D. Neilson, M. Earnshaw, M. Cappuzzo, R. Kopf, A. Tate, A. Blanco-Redondo","doi":"10.1063/5.0168959","DOIUrl":"https://doi.org/10.1063/5.0168959","url":null,"abstract":"Optical neural networks (ONNs) enable high speed, parallel, and energy efficient processing compared to their conventional digital electronic counterparts. However, realizing large scale ONN systems is an open problem. Among various integrated and non-integrated ONNs, free-space diffractive ONNs benefit from a large number of pixels of spatial light modulators to realize millions of neurons. However, a significant fraction of computation time and energy is consumed by the nonlinear activation function that is typically implemented using a camera sensor. Here, we propose a novel surface-normal photodetector (SNPD) with an optical-in–electrical-out (O–E) nonlinear response to replace the camera sensor that enables about three orders of magnitude faster (5.7 µs response time) and more energy efficient (less than 10 nW/pixel) response. Direct efficient vertical optical coupling, polarization insensitivity, inherent nonlinearity with no control electronics, low optical power requirements, and the possibility of implementing large scale arrays make the SNPD a promising O–E nonlinear activation function for diffractive ONNs. To show the applicability of the proposed neural nonlinearity, successful classification simulations of the MNIST and Fashion MNIST datasets using the measured response of SNPD with accuracy comparable to that of an ideal ReLU function are demonstrated.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"59 5","pages":""},"PeriodicalIF":5.6,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138523796","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yijia Cai, Ronit Sohanpal, Yuan Luo, Alexander M. Heidt, Zhixin Liu
Optical frequency combs (OFCs) have become increasingly pervasive in recent years, with their advantageous frequency coherence properties enabling significant developments in numerous fields, such as optical communications, spectroscopy, and microwave signal processing. Recent interest in OFC development emphasizes minimizing and mitigating phase noise of individual comb lines for high-quality signal generation, processing, and detection. Cavity-less electro-optic combs and parametric combs are attractive sources for these applications in that they permit flat spectra, tunable tone spacing, and robustness to temperature variations. Although previous research has demonstrated broadband parametric OFC generation, the scaling of the phase noise has not been systematically investigated. Here, we demonstrate a 25 GHz-spacing cavity-less parametric OFC generator and investigate the interaction between electronic and optical noise sources that affect its phase noise and linewidth. In addition, we study the optimal design of a nonlinear amplified loop mirror based pulse shaper with a focus on the impact of pump power on the signal-to-pedestal power ratio, which ultimately influences the spectral flatness and the optical signal-to-noise ratio (OSNR) after the parametric expansion. Notably, we design the OFC using all polarization-maintaining (PM) components, demonstrating the performance of PM highly nonlinear fibers in parametric comb generation. This results in a PM cavity-less comb with <9 dB power variation over 110 nm, >0 dBm power per tone, <10 kHz linewidth, and >23 dB OSNR. These characteristics make it highly desirable for application in communication and signal processing.
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