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Tunable vector vortex beam generation using phase change metasurfaces [Invited]
Xinyi Ding, Zerong Li, Jiahui Ren, Ziwei Zheng, Fei Ding, and Shiwei Tang
Vector vortex beams (VVBs), novel structured optical fields that combine the polarization properties of vector beams and phase characteristics of vortex beams, have garnered widespread attention in the photonics community. Capitalizing on recently developed metasurfaces, miniaturized VVB generators with advanced properties have been implemented. However, metasurface-empowered VVB generators remain static and can only generate one pre-designed structured light. Here, we propose a kind of phase change metasurface for tunable vector beam generation by utilizing anisotropic Ge2Sb2Se4Te1 (GSST) unit cells with tunable phase retardation when GSST transits between two different phase states. By properly rotating the orientations of the tunable GSST unit structures that transit between quarter-wave plates and half-wave plates, we can effectively transform incident plane waves into vector beams with distinct topological charges and polarization states. When GSST is in the amorphous state, the designed metasurface can transmit circularly polarized light into VVBs. In the crystalline state, the same GSST metasurface converts linearly polarized light into second-order radially polarized (RP) and azimuthally polarized (AP) beams. Our phase-change metasurface paves the way for precise control over the polarization patterns and vortex characteristics of beams, thereby enabling the exact manipulation of beam structures through the alteration of their phase states.Vector vortex beams (VVBs), novel structured optical fields that combine the polarization properties of vector beams and phase characteristics of vortex beams, have garnered widespread attention in the photonics community. Capitalizing on recently developed metasurfaces, miniaturized VVB generators with advanced properties have been implemented. However, metasurface-empowered VVB generators remain static and can only generate one pre-designed structured light. Here, we propose a kind of phase change metasurface for tunable vector beam generation by utilizing anisotropic Ge2Sb2Se4Te1 (GSST) unit cells with tunable phase retardation when GSST transits between two different phase states. By properly rotating the orientations of the tunable GSST unit structures that transit between quarter-wave plates and half-wave plates, we can effectively transform incident plane waves into vector beams with distinct topological charges and polarization states. When GSST is in the amorphous state, the designed metasurface can transmit circularly polarized light into VVBs. In the crystalline state, the same GSST metasurface converts linearly polarized light into second-order radially polarized (RP) and azimuthally polarized (AP) beams. Our phase-change metasurface paves the way for precise control over the polarization patterns and vortex characteristics of beams, thereby enabling the exact manipulation of beam structures through the alteration of their phase states.
- Nov. 06, 2024
- Chinese Optics Letters
- Vol. 22, Issue 11, 113601 (2024)
- DOI:10.3788/COL202422.113601
Advanced optical modulation for integrated computing and networking toward 6G requirement
Zhou He, Hao Huang, Peng Zhang, Dongrong Ma, Binghua Shi, Tong Wang, Yuanyuan Huang, and Jia Guo
The 6G transport network will be intricately designed as an integrated carrier, seamlessly integrating computing and networking capabilities. Leveraging the network as its foundation, it aims to deliver differentiated computing power services through supercomputing/intelligent computing and capability resource pooling. This study proposes an advanced modulation format, alternating polarization chirped return-to-zero frequency shift keying (Apol-CRZ-FSK), specifically designed to meet the integrated computing and networking carrying requirements of future 6G. Furthermore, comprehensive comparison and analysis of the transmission performance of 100 Gbps Apol-CRZ-FSK, CRZ-FSK, and differential quadrature phase shift keying (DQPSK) are conducted under identical conditions. The research indicates the high nonlinearity resistance capability exhibited by Apol-CRZ-FSK, highlighting its superior transmission performance.The 6G transport network will be intricately designed as an integrated carrier, seamlessly integrating computing and networking capabilities. Leveraging the network as its foundation, it aims to deliver differentiated computing power services through supercomputing/intelligent computing and capability resource pooling. This study proposes an advanced modulation format, alternating polarization chirped return-to-zero frequency shift keying (Apol-CRZ-FSK), specifically designed to meet the integrated computing and networking carrying requirements of future 6G. Furthermore, comprehensive comparison and analysis of the transmission performance of 100 Gbps Apol-CRZ-FSK, CRZ-FSK, and differential quadrature phase shift keying (DQPSK) are conducted under identical conditions. The research indicates the high nonlinearity resistance capability exhibited by Apol-CRZ-FSK, highlighting its superior transmission performance.
- Nov. 06, 2024
- Chinese Optics Letters
- Vol. 23, Issue 11, 110603 (2024)
- DOI:10.3788/COL202422.110603
Tunable X-ray frequency comb generation at the Shanghai soft X-ray Free-Electron Laser facility
Lanpeng Ni, Yaozong Xiao, Zheng Qi, Chao Feng, and Zhentang Zhao
X-ray frequency combs (XFCs) are of great interest in many scientific research areas. In this study, we investigate the generation of high-power tunable XFCs at the Shanghai soft X-ray Free-Electron Laser facility (SXFEL). To achieve this, a chirped frequency-beating laser is employed as the seed laser for echo-enabled harmonic generation of free-electron lasers. This approach enables the formation of an initial bunching of combs and ultimately facilitates the generation of XFCs under optimized conditions. We provide an optical design for the chirped frequency-beating seed laser system and outline a method to optimize and set the key parameters that meets the critical requirements for generating continuously tunable XFCs. Three-dimensional simulations using realistic parameters of the SXFEL demonstrate that it is possible to produce XFCs with peak power reaching 1.5 GW, central photon energy at the carbon K edge (~284 eV) and tunable repetition frequencies ranging from 7 to 12 THz. Our proposal opens up new possibilities for resonant inelastic X-ray scattering experiments at X-ray free-electron laser facilities.X-ray frequency combs (XFCs) are of great interest in many scientific research areas. In this study, we investigate the generation of high-power tunable XFCs at the Shanghai soft X-ray Free-Electron Laser facility (SXFEL). To achieve this, a chirped frequency-beating laser is employed as the seed laser for echo-enabled harmonic generation of free-electron lasers. This approach enables the formation of an initial bunching of combs and ultimately facilitates the generation of XFCs under optimized conditions. We provide an optical design for the chirped frequency-beating seed laser system and outline a method to optimize and set the key parameters that meets the critical requirements for generating continuously tunable XFCs. Three-dimensional simulations using realistic parameters of the SXFEL demonstrate that it is possible to produce XFCs with peak power reaching 1.5 GW, central photon energy at the carbon K edge (~284 eV) and tunable repetition frequencies ranging from 7 to 12 THz. Our proposal opens up new possibilities for resonant inelastic X-ray scattering experiments at X-ray free-electron laser facilities.
- Nov. 06, 2024
- High Power Laser Science and Engineering
- Vol. 12, Issue 5, 05000e60 (2024)
- DOI:10.1017/hpl.2024.37
Characterization of blast waves induced by femtosecond laser irradiation in solid targets
Katarzyna Liliana Batani, Sophia Malko, Michael Touati, Jean-Luc Feugeas, Amit D. Lad, Kamalesh Jana, G. Ravindra Kumar, Didier Raffestin, Olena Turianska, Dimitri Khaghani, Alessandro Tentori, Donaldi Mancelli, Artem S. Martynenko, Sergey Pikuz, Roberto Benocci, Luca Volpe, Ghassan Zeraouli, Jose Antonio Perez Hernandez, Enrique Garcia, Venkatakrishnan Narayanan, Joao Santos, and Dimitri Batani
Blast waves have been produced in solid target by irradiation with short-pulse high-intensity lasers. The mechanism of production relies on energy deposition from the hot electrons produced by laser–matter interaction, producing a steep temperature gradient inside the target. Hot electrons also produce preheating of the material ahead of the blast wave and expansion of the target rear side, which results in a complex blast wave propagation dynamic. Several diagnostics have been used to characterize the hot electron source, the induced preheating and the velocity of the blast wave. Results are compared to numerical simulations. These show how blast wave pressure is initially very large (more than 100 Mbar), but it decreases very rapidly during propagation.Blast waves have been produced in solid target by irradiation with short-pulse high-intensity lasers. The mechanism of production relies on energy deposition from the hot electrons produced by laser–matter interaction, producing a steep temperature gradient inside the target. Hot electrons also produce preheating of the material ahead of the blast wave and expansion of the target rear side, which results in a complex blast wave propagation dynamic. Several diagnostics have been used to characterize the hot electron source, the induced preheating and the velocity of the blast wave. Results are compared to numerical simulations. These show how blast wave pressure is initially very large (more than 100 Mbar), but it decreases very rapidly during propagation.
- Nov. 06, 2024
- High Power Laser Science and Engineering
- Vol. 12, Issue 5, 05000e59 (2024)
- DOI:10.1017/hpl.2024.36
Sub-100 fs pulse generation from dispersion-managed mode-locked Er:ZBLAN fiber laser at 2.8 μm
Xiabing Zhou, Zhipeng Qin, and Guoqiang Xie
We demonstrate the sub-100 fs pulse generation from a dispersion-managed mode-locked Er:ZBLAN fiber laser at 2.8 μm. Both numerical simulation and experiment demonstrate that stretched-pulse and dissipative soliton mode lockings coexist in the near-zero-dispersion region of a fluoride fiber laser. With fine dispersion management, the shortest pulse of 95 fs was obtained from the stretched-pulse mode-locked Er:ZBLAN fiber laser, with an average power of 280 mW and repetition rate of 52 MHz. To the best of our knowledge, this is the shortest pulse to date directly generated from a mid-infrared mode-locked fluoride fiber laser.We demonstrate the sub-100 fs pulse generation from a dispersion-managed mode-locked Er:ZBLAN fiber laser at 2.8 μm. Both numerical simulation and experiment demonstrate that stretched-pulse and dissipative soliton mode lockings coexist in the near-zero-dispersion region of a fluoride fiber laser. With fine dispersion management, the shortest pulse of 95 fs was obtained from the stretched-pulse mode-locked Er:ZBLAN fiber laser, with an average power of 280 mW and repetition rate of 52 MHz. To the best of our knowledge, this is the shortest pulse to date directly generated from a mid-infrared mode-locked fluoride fiber laser.
- Nov. 06, 2024
- High Power Laser Science and Engineering
- Vol. 12, Issue 5, 05000e58 (2024)
- DOI:10.1017/hpl.2024.35
Large-scale parallel chaotic sources utilizing reconstruction-equivalent chirp technique
Kaifei Tang, Zhenzhen Xu, Jiahui Liu, Wenxuan Wang, Zhouying Wang, Yuxin Ma, Ling Wang, Pan Dai, Zhenxing Sun, and Xiangfei Chen
We experimentally developed massive parallel chaotic sources for random bit generation, based on a monolithically integrated amplified-feedback laser (AFL) array using the reconstruction-equivalent chirp technique. Proof-of-concept experiments demonstrate that using our method, eight independent random bit streams with 100 GSa/s and uniform wavelength spacing could be obtained. In addition, there is a low correlation between different bit-stream channels. Our approach enables scalable integration for large-scale parallel chaotic channels, potentially achieving throughput capacities of up to Tb/s for random bit generation.We experimentally developed massive parallel chaotic sources for random bit generation, based on a monolithically integrated amplified-feedback laser (AFL) array using the reconstruction-equivalent chirp technique. Proof-of-concept experiments demonstrate that using our method, eight independent random bit streams with 100 GSa/s and uniform wavelength spacing could be obtained. In addition, there is a low correlation between different bit-stream channels. Our approach enables scalable integration for large-scale parallel chaotic channels, potentially achieving throughput capacities of up to Tb/s for random bit generation.
- Nov. 04, 2024
- Chinese Optics Letters
- Vol. 22, Issue 11, 111301 (2024)
- DOI:10.3788/COL202422.111301
Direct measurement of intermodal nonlinear coefficient with continuous-wave lasers
Xiaoshan Huang, Zhijie Deng, Gai Zhou, Jilong Li, Meng Xiang, Di Lin, Songnian Fu, and Yuwen Qin
The intermodal nonlinear coefficient is an important parameter to analytically describe few-mode fiber (FMF) nonlinearity when the nonlinear interaction arising in the FMF is exploited for various applications. Here, we experimentally characterize the intermodal nonlinear coefficient based on continuous-wave cross-phase modulation, without a priori knowledge of the intramodal nonlinear coefficient for the FMF under test. Based on the derived equation, we examine the impact of the pump modulation scheme and the wavelength spacing between the probe and pump on the precise measurement of the intermodal nonlinear coefficient. Compared with double sideband (DSB) modulation, the pump modulated with carrier-suppressed DSB scheme leads to an underestimation of measurement results, due to the coexistence of unnecessary nonlinear interactions. Finally, the intermodal nonlinear coefficient of a 1.9-km FMF supporting two mode groups is experimentally characterized and is in good agreement with the theoretically calculated values. Due to the random birefringence fluctuation, the average value of 4/3 to describe the intermodal nonlinear interaction arising in weakly coupled FMF by the commonly used Manakov equation is experimentally verified.The intermodal nonlinear coefficient is an important parameter to analytically describe few-mode fiber (FMF) nonlinearity when the nonlinear interaction arising in the FMF is exploited for various applications. Here, we experimentally characterize the intermodal nonlinear coefficient based on continuous-wave cross-phase modulation, without a priori knowledge of the intramodal nonlinear coefficient for the FMF under test. Based on the derived equation, we examine the impact of the pump modulation scheme and the wavelength spacing between the probe and pump on the precise measurement of the intermodal nonlinear coefficient. Compared with double sideband (DSB) modulation, the pump modulated with carrier-suppressed DSB scheme leads to an underestimation of measurement results, due to the coexistence of unnecessary nonlinear interactions. Finally, the intermodal nonlinear coefficient of a 1.9-km FMF supporting two mode groups is experimentally characterized and is in good agreement with the theoretically calculated values. Due to the random birefringence fluctuation, the average value of 4/3 to describe the intermodal nonlinear interaction arising in weakly coupled FMF by the commonly used Manakov equation is experimentally verified.
- Nov. 04, 2024
- Chinese Optics Letters
- Vol. 22, Issue 11, 110601 (2024)
- DOI:10.3788/COL202422.110601
Reducing statistical noise in frequency ratio measurement between Ca+ and Sr optical clocks with a frequency-synthesized local oscillator from a Sr optical clock
Haosen Shi, Bingkun Lu, Huaqing Zhang, Ruming Hu, Yuan Qian, Yao Huang, Tao Yang, Yuan Yao, Hongfu Yu, Zhanjun Fang, Kelin Gao, Hua Guan, Yige Lin, Yanyi Jiang, and Longsheng Ma
Optical frequency ratio measurement between optical atomic clocks is essential to precision measurement as well as the redefinition of the second. Currently, the statistical noise in frequency ratio measurement of most ion clocks is limited by the frequency instability of ion clocks. In this work, we reduce the statistical noise in the frequency ratio measurement between a transportable Ca+ optical clock and a Sr optical lattice clock down to 2.2×10-15/τ. The local oscillator of the Ca+ optical clock is frequency-synthesized from the Sr optical lattice clock, enabling a longer probe time for Ca+ clock transition. Compared to previous measurement using independent local oscillators, we achieve 10-fold reduction in comparison campaign duration.Optical frequency ratio measurement between optical atomic clocks is essential to precision measurement as well as the redefinition of the second. Currently, the statistical noise in frequency ratio measurement of most ion clocks is limited by the frequency instability of ion clocks. In this work, we reduce the statistical noise in the frequency ratio measurement between a transportable optical clock and a Sr optical lattice clock down to . The local oscillator of the optical clock is frequency-synthesized from the Sr optical lattice clock, enabling a longer probe time for clock transition. Compared to previous measurement using independent local oscillators, we achieve 10-fold reduction in comparison campaign duration.
- Nov. 01, 2024
- Photonics Research
- Vol. 12, Issue 11, 2741 (2024)
- DOI:10.1364/PRJ.539892
Linear and nonlinear coupling of light in twin-resonators with Kerr nonlinearity
Arghadeep Pal, Alekhya Ghosh, Shuangyou Zhang, Lewis Hill, Haochen Yan, Hao Zhang, Toby Bi, Abdullah Alabbadi, and Pascal Del’Haye
Nonlinear effects in microresonators are efficient building blocks for all-optical computing and telecom systems. With the latest advances in microfabrication, coupled microresonators are used in a rapidly growing number of applications. In this work, we investigate the coupling between twin-resonators in the presence of Kerr nonlinearity. We use an experimental setup with controllable coupling between two high-Q resonators and discuss the effects caused by the simultaneous presence of linear and nonlinear coupling between the optical fields. Linear-coupling-induced mode splitting is observed at low input powers, with the controllable coupling leading to a tunable mode splitting. At high input powers, the hybridized resonances show spontaneous symmetry breaking (SSB) effects, in which the optical power is unevenly distributed between the resonators. Our experimental results are supported by a detailed theoretical model of nonlinear twin-resonators. With the recent interest in coupled resonator systems for neuromorphic computing, quantum systems, and optical frequency comb generation, our work provides important insights into the behavior of these systems at high circulating powers.Nonlinear effects in microresonators are efficient building blocks for all-optical computing and telecom systems. With the latest advances in microfabrication, coupled microresonators are used in a rapidly growing number of applications. In this work, we investigate the coupling between twin-resonators in the presence of Kerr nonlinearity. We use an experimental setup with controllable coupling between two high-Q resonators and discuss the effects caused by the simultaneous presence of linear and nonlinear coupling between the optical fields. Linear-coupling-induced mode splitting is observed at low input powers, with the controllable coupling leading to a tunable mode splitting. At high input powers, the hybridized resonances show spontaneous symmetry breaking (SSB) effects, in which the optical power is unevenly distributed between the resonators. Our experimental results are supported by a detailed theoretical model of nonlinear twin-resonators. With the recent interest in coupled resonator systems for neuromorphic computing, quantum systems, and optical frequency comb generation, our work provides important insights into the behavior of these systems at high circulating powers.
- Nov. 01, 2024
- Photonics Research
- Vol. 12, Issue 11, 2733 (2024)
- DOI:10.1364/PRJ.535301
Measuring the OAM spectrum of a fractional helical beam in a single shot
Tushar Sarkar, Jiapeng Cai, Xiang Peng, and Wenqi He
We propose and experimentally demonstrate a new technique, to our knowledge, to precisely measure the orbital angular momentum (OAM) spectrum of the fractional helical beam in a single shot. This is realized using a single-path interferometer scheme combined with space division multiplexing and polarization phase-shifting. Such a combination enables the single-shot recording of multiple phase-shifted interferograms, which leads to extracting the phase profile of the incident fractional helical beam. Furthermore, by adopting an orthogonal projection method, this measured phase is utilized to evaluate the corresponding OAM spectrum. To test the efficacy, a set of simulations and experiments for different fractional helical beams is demonstrated. The proposed method shows enormous potential to characterize the OAM spectrum in real time.We propose and experimentally demonstrate a new technique, to our knowledge, to precisely measure the orbital angular momentum (OAM) spectrum of the fractional helical beam in a single shot. This is realized using a single-path interferometer scheme combined with space division multiplexing and polarization phase-shifting. Such a combination enables the single-shot recording of multiple phase-shifted interferograms, which leads to extracting the phase profile of the incident fractional helical beam. Furthermore, by adopting an orthogonal projection method, this measured phase is utilized to evaluate the corresponding OAM spectrum. To test the efficacy, a set of simulations and experiments for different fractional helical beams is demonstrated. The proposed method shows enormous potential to characterize the OAM spectrum in real time.
- Nov. 01, 2024
- Photonics Research
- Vol. 12, Issue 11, 2726 (2024)
- DOI:10.1364/PRJ.538320
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