Yanzhao Guo, John P. Hadden, Federico Gorrini, Giulio Coccia, Vibhav Bharadwaj, Vinaya Kumar Kavatamane, Mohammad Sahnawaz Alam, Roberta Ramponi, Paul E. Barclay, Andrea Chiappini, Maurizio Ferrari, Alexander Kubanek, Angelo Bifone, Shane M. Eaton, Anthony J. Bennett
Quantum emitters, such as the negatively charged nitrogen-vacancy center in diamond, are attractive for quantum technologies, such as nano-sensing, quantum information processing, and as a non-classical light source. However, it is still challenging to position individual emitters in photonic structures while preserving the spin coherence properties of the defect. In this paper, we investigate single and ensemble waveguide-integrated nitrogen-vacancy centers in diamond fabricated by femtosecond laser writing followed by thermal annealing. Their spin coherence properties are systematically investigated and are shown to be comparable to native nitrogen-vacancy centers in diamond. This method paves the way for the fabrication of coherent spins integrated within photonic devices.
{"title":"Laser-written waveguide-integrated coherent spins in diamond","authors":"Yanzhao Guo, John P. Hadden, Federico Gorrini, Giulio Coccia, Vibhav Bharadwaj, Vinaya Kumar Kavatamane, Mohammad Sahnawaz Alam, Roberta Ramponi, Paul E. Barclay, Andrea Chiappini, Maurizio Ferrari, Alexander Kubanek, Angelo Bifone, Shane M. Eaton, Anthony J. Bennett","doi":"10.1063/5.0209294","DOIUrl":"https://doi.org/10.1063/5.0209294","url":null,"abstract":"Quantum emitters, such as the negatively charged nitrogen-vacancy center in diamond, are attractive for quantum technologies, such as nano-sensing, quantum information processing, and as a non-classical light source. However, it is still challenging to position individual emitters in photonic structures while preserving the spin coherence properties of the defect. In this paper, we investigate single and ensemble waveguide-integrated nitrogen-vacancy centers in diamond fabricated by femtosecond laser writing followed by thermal annealing. Their spin coherence properties are systematically investigated and are shown to be comparable to native nitrogen-vacancy centers in diamond. This method paves the way for the fabrication of coherent spins integrated within photonic devices.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"15 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141517030","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}
Giuseppe Fumero, Giovanni Batignani, Edoardo Cassetta, Carino Ferrante, Stefano Giagu, Tullio Scopigno
Noise manifests ubiquitously in nonlinear spectroscopy, where multiple sources contribute to experimental signals generating interrelated unwanted components, from random point-wise fluctuations to structured baseline signals. Mitigating strategies are usually heuristic, depending on subjective biases such as the setting of parameters in data analysis algorithms and the removal order of the unwanted components. We propose a data-driven frequency-domain denoiser based on a convolutional neural network to extract authentic vibrational features from a nonlinear background in noisy spectroscopic raw data. The different spectral scales in the problem are treated in parallel by means of filters with multiple kernel sizes, which allow the receptive field of the network to adapt to the informative features in the spectra. We test our approach by retrieving asymmetric peaks in stimulated Raman spectroscopy, an ideal test-bed due to its intrinsic complex spectral features combined with a strong background signal. By using a theoretical perturbative toolbox, we efficiently train the network with simulated datasets resembling the statistical properties and lineshapes of the experimental spectra. The developed algorithm is successfully applied to experimental data to obtain noise- and background-free stimulated Raman spectra of organic molecules and prototypical heme proteins.
{"title":"Retrieving genuine nonlinear Raman responses in ultrafast spectroscopy via deep learning","authors":"Giuseppe Fumero, Giovanni Batignani, Edoardo Cassetta, Carino Ferrante, Stefano Giagu, Tullio Scopigno","doi":"10.1063/5.0198013","DOIUrl":"https://doi.org/10.1063/5.0198013","url":null,"abstract":"Noise manifests ubiquitously in nonlinear spectroscopy, where multiple sources contribute to experimental signals generating interrelated unwanted components, from random point-wise fluctuations to structured baseline signals. Mitigating strategies are usually heuristic, depending on subjective biases such as the setting of parameters in data analysis algorithms and the removal order of the unwanted components. We propose a data-driven frequency-domain denoiser based on a convolutional neural network to extract authentic vibrational features from a nonlinear background in noisy spectroscopic raw data. The different spectral scales in the problem are treated in parallel by means of filters with multiple kernel sizes, which allow the receptive field of the network to adapt to the informative features in the spectra. We test our approach by retrieving asymmetric peaks in stimulated Raman spectroscopy, an ideal test-bed due to its intrinsic complex spectral features combined with a strong background signal. By using a theoretical perturbative toolbox, we efficiently train the network with simulated datasets resembling the statistical properties and lineshapes of the experimental spectra. The developed algorithm is successfully applied to experimental data to obtain noise- and background-free stimulated Raman spectra of organic molecules and prototypical heme proteins.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"30 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141502407","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}
A. R. Bowman, J. Ma, F. Kiani, G. García Martínez, G. Tagliabue
The fraction of light absorbed in a material is a key parameter for a wide range of optoelectronic and energy devices, including solar cells, light emitting diodes, and photo(electro)chemical devices. It can reveal detailed performance information and establish a material’s theoretical efficiency limits. However, measuring absorption accurately is challenging, especially due to scattering effects at the macroscale and achieving perpendicular illumination over a small area at the microscale. In this tutorial, we present concepts and best practices in measuring absorption at both the macro- and micro-scale. We also give examples of using absorption to reveal critical optoelectronic information in energy devices. This work aims at standardizing the recording of absorption measurements across a number of fields, allowing for improved microscale understanding of a wide range of samples.
{"title":"Best practices in measuring absorption at the macro- and microscale","authors":"A. R. Bowman, J. Ma, F. Kiani, G. García Martínez, G. Tagliabue","doi":"10.1063/5.0210830","DOIUrl":"https://doi.org/10.1063/5.0210830","url":null,"abstract":"The fraction of light absorbed in a material is a key parameter for a wide range of optoelectronic and energy devices, including solar cells, light emitting diodes, and photo(electro)chemical devices. It can reveal detailed performance information and establish a material’s theoretical efficiency limits. However, measuring absorption accurately is challenging, especially due to scattering effects at the macroscale and achieving perpendicular illumination over a small area at the microscale. In this tutorial, we present concepts and best practices in measuring absorption at both the macro- and micro-scale. We also give examples of using absorption to reveal critical optoelectronic information in energy devices. This work aims at standardizing the recording of absorption measurements across a number of fields, allowing for improved microscale understanding of a wide range of samples.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"46 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141502495","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}
Mark E. Turiansky, Kamyar Parto, Galan Moody, Chris G. Van de Walle
Single-photon emitters are an essential component of quantum networks, and defects or impurities in semiconductors are a promising platform to realize such quantum emitters. Here, we present a model that encapsulates the essential physics of coupling to phonons, which governs the behavior of real single-photon emitters, and critically evaluate several approximations that are commonly utilized. Emission in the telecom wavelength range is highly desirable, but our model shows that nonradiative processes are greatly enhanced at these low photon energies, leading to a decrease in efficiency. Our results suggest that reducing the phonon frequency is a fruitful avenue to enhance the efficiency.
{"title":"Rational design of efficient defect-based quantum emitters","authors":"Mark E. Turiansky, Kamyar Parto, Galan Moody, Chris G. Van de Walle","doi":"10.1063/5.0203366","DOIUrl":"https://doi.org/10.1063/5.0203366","url":null,"abstract":"Single-photon emitters are an essential component of quantum networks, and defects or impurities in semiconductors are a promising platform to realize such quantum emitters. Here, we present a model that encapsulates the essential physics of coupling to phonons, which governs the behavior of real single-photon emitters, and critically evaluate several approximations that are commonly utilized. Emission in the telecom wavelength range is highly desirable, but our model shows that nonradiative processes are greatly enhanced at these low photon energies, leading to a decrease in efficiency. Our results suggest that reducing the phonon frequency is a fruitful avenue to enhance the efficiency.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"13 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141517031","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}
Peco Myint, Ashish Tripathi, Michael J. Wojcik, Junjing Deng, Mathew J. Cherukara, Nicholas Schwarz, Suresh Narayanan, Jin Wang, Miaoqi Chu, Zhang Jiang
Many nanodevices and quantum devices, with their sizes often spanning from millimeters down to sub-nanometer, have intricate low-dimensional, non-uniform, or hierarchical structures on surfaces and interfaces. Since their functionalities are dependent on these structures, high-resolution surface-sensitive characterization becomes imperative to gain a comprehensive understanding of the function–structure relationship. We thus developed hard x-ray ptychographic reflectometry imaging, a new technique that merges the high-resolution two-dimensional imaging capabilities of hard x-ray ptychography for extended objects, with the high-resolution depth profiling capabilities of x-ray reflectivity for layered structures. The synergy of these two methods fully leverages both amplitude and phase information from ptychography reconstruction to not only reveal surface topography and localized structures, such as shapes and electron densities, but also yields statistical details, such as interfacial roughness that is not readily accessible through coherent imaging solely. The hard x-ray ptychographic reflectometry imaging is well-suited for three-dimensional imaging of mesoscopic samples, particularly those comprising planar or layered nanostructures on opaque supports, and could also offer a high-resolution surface metrology and defect analysis on semiconductor devices, such as integrated nanocircuits and lithographic photomasks for microchip fabrications.
许多纳米器件和量子设备的尺寸通常从毫米到亚纳米不等，其表面和界面具有错综复杂的低维、非均匀或分层结构。由于其功能依赖于这些结构，因此必须进行高分辨率的表面敏感表征，以全面了解功能与结构之间的关系。因此，我们开发了硬 X 射线层析反射成像技术，这种新技术融合了硬 X 射线层析成像技术对延伸物体的高分辨率二维成像能力，以及 X 射线反射成像技术对层状结构的高分辨率深度剖面成像能力。这两种方法的协同作用充分利用了层析成像重建的振幅和相位信息，不仅揭示了表面形貌和局部结构（如形状和电子密度），还产生了统计细节，如仅通过相干成像不易获得的界面粗糙度。硬 X 射线层析反射成像非常适合中观样品的三维成像，特别是那些在不透明支撑物上包含平面或层状纳米结构的样品，还可以对半导体器件（如集成纳米电路和用于微芯片制造的光刻光掩模）进行高分辨率表面计量和缺陷分析。
{"title":"Three-dimensional hard X-ray ptychographic reflectometry imaging on extended mesoscopic surface structures","authors":"Peco Myint, Ashish Tripathi, Michael J. Wojcik, Junjing Deng, Mathew J. Cherukara, Nicholas Schwarz, Suresh Narayanan, Jin Wang, Miaoqi Chu, Zhang Jiang","doi":"10.1063/5.0204240","DOIUrl":"https://doi.org/10.1063/5.0204240","url":null,"abstract":"Many nanodevices and quantum devices, with their sizes often spanning from millimeters down to sub-nanometer, have intricate low-dimensional, non-uniform, or hierarchical structures on surfaces and interfaces. Since their functionalities are dependent on these structures, high-resolution surface-sensitive characterization becomes imperative to gain a comprehensive understanding of the function–structure relationship. We thus developed hard x-ray ptychographic reflectometry imaging, a new technique that merges the high-resolution two-dimensional imaging capabilities of hard x-ray ptychography for extended objects, with the high-resolution depth profiling capabilities of x-ray reflectivity for layered structures. The synergy of these two methods fully leverages both amplitude and phase information from ptychography reconstruction to not only reveal surface topography and localized structures, such as shapes and electron densities, but also yields statistical details, such as interfacial roughness that is not readily accessible through coherent imaging solely. The hard x-ray ptychographic reflectometry imaging is well-suited for three-dimensional imaging of mesoscopic samples, particularly those comprising planar or layered nanostructures on opaque supports, and could also offer a high-resolution surface metrology and defect analysis on semiconductor devices, such as integrated nanocircuits and lithographic photomasks for microchip fabrications.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"67 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141517032","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}
Automatic polarization controllers find broad applications in various fields, including optical communication, quantum optics, optical sensing, and biomedicine. Currently, the predominant integrated automatic polarization controllers employ either lithium niobate or silicon platforms. Devices based on lithium niobate platforms exhibit excellent performance; however, their fabrication complexity hinders widespread commercial deployment. In contrast, silicon-based integrated automatic polarization controllers benefit from complementary metal–oxide–semiconductor compatibility and reduced fabrication costs. Nevertheless, these silicon automatic polarization controllers suffer from low tracking speeds, peaking at merely 1.256 krad/s. In this study, we demonstrated a silicon high-speed automatic polarization controller, incorporating innovative thermal tuning units combined with a sophisticated control algorithm. The response time of these thermal tuning units has been markedly decreased to 3.2 µs. In addition, we have implemented a novel automatic polarization control algorithm, utilizing gradient descent techniques, on a field-programmable gate array control board. The synergy of the rapid thermal tuning unit and the advanced control algorithm has enabled us to attain an unprecedented polarization control speed of up to 20 krad/s, with this rate being solely limited by the capabilities of our characterization equipment. To our knowledge, this speed is the fastest yet reported for a silicon-based integrated automatic polarization control chip. The proposed device represents a significant breakthrough in the field of silicon-based automatic polarization controllers, paving the way for the future integration of additional polarization management devices. Such an advancement would mark a substantial leap in the realm of integrated photonics, bridging the gap between performance efficiency, cost-effectiveness, and technological integration.
{"title":"CMOS-compatible high-speed endless automatic polarization controller","authors":"Weiqin Wang, Ziwen Zhou, Yifan Zeng, Jingze Liu, Gengqi Yao, Hao Wu, Yunhong Ding, Siyan Zhou, Siqi Yan, Ming Tang","doi":"10.1063/5.0198227","DOIUrl":"https://doi.org/10.1063/5.0198227","url":null,"abstract":"Automatic polarization controllers find broad applications in various fields, including optical communication, quantum optics, optical sensing, and biomedicine. Currently, the predominant integrated automatic polarization controllers employ either lithium niobate or silicon platforms. Devices based on lithium niobate platforms exhibit excellent performance; however, their fabrication complexity hinders widespread commercial deployment. In contrast, silicon-based integrated automatic polarization controllers benefit from complementary metal–oxide–semiconductor compatibility and reduced fabrication costs. Nevertheless, these silicon automatic polarization controllers suffer from low tracking speeds, peaking at merely 1.256 krad/s. In this study, we demonstrated a silicon high-speed automatic polarization controller, incorporating innovative thermal tuning units combined with a sophisticated control algorithm. The response time of these thermal tuning units has been markedly decreased to 3.2 µs. In addition, we have implemented a novel automatic polarization control algorithm, utilizing gradient descent techniques, on a field-programmable gate array control board. The synergy of the rapid thermal tuning unit and the advanced control algorithm has enabled us to attain an unprecedented polarization control speed of up to 20 krad/s, with this rate being solely limited by the capabilities of our characterization equipment. To our knowledge, this speed is the fastest yet reported for a silicon-based integrated automatic polarization control chip. The proposed device represents a significant breakthrough in the field of silicon-based automatic polarization controllers, paving the way for the future integration of additional polarization management devices. Such an advancement would mark a substantial leap in the realm of integrated photonics, bridging the gap between performance efficiency, cost-effectiveness, and technological integration.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"1 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141516976","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}
We propose an all-optical approach to generating space–time wave packets in a multimode slab waveguide via the multilevel interband stimulated Brillouin scattering process. Two pump sources and a single-mode signal are fed into the waveguide. The pumps generate a single-mode acoustic wave through the electrostrictive process. The acoustic wave then induces an indirect interband photonic transition from the signal wave, resulting in a light bullet, that is, a space–time wave packet that does not change its spatial and temporal shape as it propagates through the waveguide.
{"title":"Light bullet generation via stimulated Brillouin scattering","authors":"Der-Han Huang, Cheng Guo, Shanhui Fan","doi":"10.1063/5.0201756","DOIUrl":"https://doi.org/10.1063/5.0201756","url":null,"abstract":"We propose an all-optical approach to generating space–time wave packets in a multimode slab waveguide via the multilevel interband stimulated Brillouin scattering process. Two pump sources and a single-mode signal are fed into the waveguide. The pumps generate a single-mode acoustic wave through the electrostrictive process. The acoustic wave then induces an indirect interband photonic transition from the signal wave, resulting in a light bullet, that is, a space–time wave packet that does not change its spatial and temporal shape as it propagates through the waveguide.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"15 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141517033","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}
Pattern-illuminated Fourier ptychography (piFP) is an elegant combination of structured illumination imaging and a Fourier ptychographic algorithm with the ability to image beyond the diffraction limit of the employed optics. Artifact-free piFP super-resolution reconstruction requires a high level of stability in the illumination pattern. However, unpredictable pattern variation occurs in the presence of environment perturbation, intensity fluctuation, and pointing instability at the source, leading to declines in image reconstruction quality. To address this issue, we present an efficient and robust piFP algorithm based on low-rank approximation (LRA-piFP), which relaxes the requirement for the stability of illumination patterns. This LRA-piFP method can model frame-wise pattern variation during a full scan, thus improve the reconstruction quality significantly. We take numerical simulations and proof-of-principle experiments with both long-range imaging and microscopy for demonstrations. Results show that the LRA-piFP method can handle different kinds of pattern variation and outperforms other state-of-the-art techniques in terms of reconstruction quality and resolution improvement. Our method provides effective experimental robustness to piFP with a natural algorithmic extension, paving the way for its application in both macroscopic and microscopic imaging.
{"title":"Toward robust super-resolution imaging: A low-rank approximation approach for pattern-illuminated Fourier ptychography","authors":"Junhao Zhang, Weilong Wei, Kaiyuan Yang, Qiang Zhou, Haotong Ma, Ge Ren, Zongliang Xie","doi":"10.1063/5.0200549","DOIUrl":"https://doi.org/10.1063/5.0200549","url":null,"abstract":"Pattern-illuminated Fourier ptychography (piFP) is an elegant combination of structured illumination imaging and a Fourier ptychographic algorithm with the ability to image beyond the diffraction limit of the employed optics. Artifact-free piFP super-resolution reconstruction requires a high level of stability in the illumination pattern. However, unpredictable pattern variation occurs in the presence of environment perturbation, intensity fluctuation, and pointing instability at the source, leading to declines in image reconstruction quality. To address this issue, we present an efficient and robust piFP algorithm based on low-rank approximation (LRA-piFP), which relaxes the requirement for the stability of illumination patterns. This LRA-piFP method can model frame-wise pattern variation during a full scan, thus improve the reconstruction quality significantly. We take numerical simulations and proof-of-principle experiments with both long-range imaging and microscopy for demonstrations. Results show that the LRA-piFP method can handle different kinds of pattern variation and outperforms other state-of-the-art techniques in terms of reconstruction quality and resolution improvement. Our method provides effective experimental robustness to piFP with a natural algorithmic extension, paving the way for its application in both macroscopic and microscopic imaging.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"145 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141528919","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}
The statistical mechanical behavior of weakly nonlinear multimoded optical settings has been attracting increased interest over the last few years. The main purpose of this work is to numerically investigate the main factors that affect the thermalization process in photonic lattices. In particular, we find that lattices with identically selected properties (such as temperature, coupling coefficient, lattice size, and excitation conditions) can exhibit very different thermalization dynamics and, thus, thermalization distances. Our investigation is focused on two different two-dimensional lattices: the honeycomb lattice and the triangular lattice. Our numerical results show that, independently of the excitation conditions, the honeycomb lattice always thermalizes faster than the triangular lattice. We mainly explain this behavior by the quasilinear spectrum that promotes wave-mixing in the honeycomb lattice in comparison to the power-like spectrum of the triangular lattice. In addition, we investigate the combined effects of temperature as well as the sign and magnitude of the nonlinearity. Switching either the sign of the Kerr nonlinear coefficient or the sign of the temperature can lead to significant differences in the thermalization dynamics, a phenomenon that can be physically explained in terms of wave instabilities. Larger absolute values of the temperature |T| result in more uniform distributions for the power occupation numbers and faster thermalization speeds. Finally, as expected, increasing the magnitude of the nonlinearity results in accelerated thermalization. Our findings provide valuable insights into optical thermalization in discrete systems, where experimental realization may bring about new possibilities for light manipulation and applications.
{"title":"Thermalization dynamics in photonic lattices of different geometries","authors":"Guowen Yang, Domenico Bongiovanni, Daohong Song, Roberto Morandotti, Zhigang Chen, Nikolaos K. Efremidis","doi":"10.1063/5.0205202","DOIUrl":"https://doi.org/10.1063/5.0205202","url":null,"abstract":"The statistical mechanical behavior of weakly nonlinear multimoded optical settings has been attracting increased interest over the last few years. The main purpose of this work is to numerically investigate the main factors that affect the thermalization process in photonic lattices. In particular, we find that lattices with identically selected properties (such as temperature, coupling coefficient, lattice size, and excitation conditions) can exhibit very different thermalization dynamics and, thus, thermalization distances. Our investigation is focused on two different two-dimensional lattices: the honeycomb lattice and the triangular lattice. Our numerical results show that, independently of the excitation conditions, the honeycomb lattice always thermalizes faster than the triangular lattice. We mainly explain this behavior by the quasilinear spectrum that promotes wave-mixing in the honeycomb lattice in comparison to the power-like spectrum of the triangular lattice. In addition, we investigate the combined effects of temperature as well as the sign and magnitude of the nonlinearity. Switching either the sign of the Kerr nonlinear coefficient or the sign of the temperature can lead to significant differences in the thermalization dynamics, a phenomenon that can be physically explained in terms of wave instabilities. Larger absolute values of the temperature |T| result in more uniform distributions for the power occupation numbers and faster thermalization speeds. Finally, as expected, increasing the magnitude of the nonlinearity results in accelerated thermalization. Our findings provide valuable insights into optical thermalization in discrete systems, where experimental realization may bring about new possibilities for light manipulation and applications.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"36 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141516978","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}
Kabish Wisal, Chun-Wei Chen, Hui Cao, A. Douglas Stone
Transverse Mode Instability (TMI) that results from dynamic nonlinear thermo-optical scattering is the primary limitation to power scaling in high-power fiber lasers and amplifiers. It has been proposed that TMI can be suppressed by exciting multiple modes in a highly multimode fiber. We derive a semi-analytic frequency-domain theory of the threshold for the onset of TMI in narrowband fiber amplifiers under arbitrary multimode input excitation for general fiber geometries. Our detailed model includes the effect of gain saturation, pump depletion, and mode-dependent gain. We show that TMI results from the exponential growth of noise in all the modes at downshifted frequencies due to the thermo-optical coupling. The noise growth rate in each mode is given by the sum of signal powers in various modes weighted by pairwise thermo-optical coupling coefficients. We calculate thermo-optical coupling coefficients for all ∼104 pairs of modes in a standard circular multimode fiber and show that modes with large transverse spatial frequency mismatch are weakly coupled, resulting in a banded coupling matrix. This short-range behavior is due to the diffusive nature of the heat propagation, which mediates the coupling and leads to a lower noise growth rate upon multimode excitation compared to a single mode, resulting in significant TMI suppression. We find that the TMI threshold scales linearly with the number of modes that are excited asymptotically, leading to roughly an order of magnitude increase in the TMI threshold in an 82-mode fiber amplifier.
{"title":"Theory of transverse mode instability in fiber amplifiers with multimode excitations","authors":"Kabish Wisal, Chun-Wei Chen, Hui Cao, A. Douglas Stone","doi":"10.1063/5.0206859","DOIUrl":"https://doi.org/10.1063/5.0206859","url":null,"abstract":"Transverse Mode Instability (TMI) that results from dynamic nonlinear thermo-optical scattering is the primary limitation to power scaling in high-power fiber lasers and amplifiers. It has been proposed that TMI can be suppressed by exciting multiple modes in a highly multimode fiber. We derive a semi-analytic frequency-domain theory of the threshold for the onset of TMI in narrowband fiber amplifiers under arbitrary multimode input excitation for general fiber geometries. Our detailed model includes the effect of gain saturation, pump depletion, and mode-dependent gain. We show that TMI results from the exponential growth of noise in all the modes at downshifted frequencies due to the thermo-optical coupling. The noise growth rate in each mode is given by the sum of signal powers in various modes weighted by pairwise thermo-optical coupling coefficients. We calculate thermo-optical coupling coefficients for all ∼104 pairs of modes in a standard circular multimode fiber and show that modes with large transverse spatial frequency mismatch are weakly coupled, resulting in a banded coupling matrix. This short-range behavior is due to the diffusive nature of the heat propagation, which mediates the coupling and leads to a lower noise growth rate upon multimode excitation compared to a single mode, resulting in significant TMI suppression. We find that the TMI threshold scales linearly with the number of modes that are excited asymptotically, leading to roughly an order of magnitude increase in the TMI threshold in an 82-mode fiber amplifier.","PeriodicalId":8198,"journal":{"name":"APL Photonics","volume":"29 1","pages":""},"PeriodicalIF":5.6,"publicationDate":"2024-06-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141516977","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}
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