Pub Date : 2024-01-03DOI: 10.3390/photonics11010050
Yongtao Zhang, Jiayi Yu
Both coherence and polarization are important inherent properties of light [...]
相干性和偏振都是光的重要固有特性 [...]
{"title":"Introduction to the Special Issue on Coherent and Polarization Optics","authors":"Yongtao Zhang, Jiayi Yu","doi":"10.3390/photonics11010050","DOIUrl":"https://doi.org/10.3390/photonics11010050","url":null,"abstract":"Both coherence and polarization are important inherent properties of light [...]","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"29 46","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139388715","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2024-01-03DOI: 10.3390/photonics11010048
P. Agruzov, M.V. Parfenov, I. Ilichev, A. Varlamov, A. Tronev, A. Shamrai
The influence of an operating point on the linearity of an integrated optical lithium niobate directional coupler modulator was studied. It was found that the optimal setting for the position of an operating point for suppressing the third-order intermodulation distortion depended on the power of the high-frequency modulation signal. Thus, despite the simple design of the device, the directional coupler modulator requires a complex algorithm for setting an operating point to achieve a high linearity of operation. An active system for setting an operating point based on the low-frequency pilot signal and zeroing its third harmonic was used to demonstrate the possibility of linearization when the amplitude of the modulation signal changes. The use of an operating point control system became possible after limiting the drift of the operating point by etching the dielectric buffer layer in the interelectrode gap. The results obtained look promising for high-performance analog optical links.
{"title":"The Optimal Operating Point for Linearizing an Integrated Optical Lithium Niobate Directional Coupler Modulator","authors":"P. Agruzov, M.V. Parfenov, I. Ilichev, A. Varlamov, A. Tronev, A. Shamrai","doi":"10.3390/photonics11010048","DOIUrl":"https://doi.org/10.3390/photonics11010048","url":null,"abstract":"The influence of an operating point on the linearity of an integrated optical lithium niobate directional coupler modulator was studied. It was found that the optimal setting for the position of an operating point for suppressing the third-order intermodulation distortion depended on the power of the high-frequency modulation signal. Thus, despite the simple design of the device, the directional coupler modulator requires a complex algorithm for setting an operating point to achieve a high linearity of operation. An active system for setting an operating point based on the low-frequency pilot signal and zeroing its third harmonic was used to demonstrate the possibility of linearization when the amplitude of the modulation signal changes. The use of an operating point control system became possible after limiting the drift of the operating point by etching the dielectric buffer layer in the interelectrode gap. The results obtained look promising for high-performance analog optical links.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"43 5","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451690","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Based on the application requirements of high spectral resolutions, high spatial resolutions and wide swatches, a new-generation, high-performance, spaceborne, hyperspectral imaging spectrometer (NGHSI) with a spatial resolution of 15 m and a swatch of 90 km is proposed. The optical system of the NGHSI has a focal length of 1128 mm, an F-number of three, a field of view (FOV) of 7.32° and a slit length of 144 mm. A new off-axis, multi-mirror telescope structure with intermediate images is put forward, which solves the design problem that realizes secondary imaging and good telecentricity at the same time. And a new off-axis lens-compensation Offner configuration is adopted to address the challenge of the high-fidelity design of spectral imaging systems with long slit lengths. The relationship between X-Y polynomials and aberration coefficients is analyzed, and the X-Y polynomial freeform surfaces are used to correct the off-axis aberrations. The design results show that the image quality of the telescope system is close to the diffraction limit. The smile, known as the spectral distortion along the line, and keystone, which is the magnification difference for different wavelengths, of the spectral imaging system are less than 1/10 pixel size. The complete optical system of the NGHSI, including the telescope system and the spectral imaging system, has excellent imaging quality and the layout is compact and reasonable, which realizes the miniaturization design.
{"title":"Design of a Spaceborne, Compact, Off-Axis, Multi-Mirror Optical System Based on Freeform Surfaces","authors":"Baohua Wang, Xiaoyong Wang, Huilin Jiang, Yuanyuan Wang, Chao Yang, Yao Meng","doi":"10.3390/photonics11010051","DOIUrl":"https://doi.org/10.3390/photonics11010051","url":null,"abstract":"Based on the application requirements of high spectral resolutions, high spatial resolutions and wide swatches, a new-generation, high-performance, spaceborne, hyperspectral imaging spectrometer (NGHSI) with a spatial resolution of 15 m and a swatch of 90 km is proposed. The optical system of the NGHSI has a focal length of 1128 mm, an F-number of three, a field of view (FOV) of 7.32° and a slit length of 144 mm. A new off-axis, multi-mirror telescope structure with intermediate images is put forward, which solves the design problem that realizes secondary imaging and good telecentricity at the same time. And a new off-axis lens-compensation Offner configuration is adopted to address the challenge of the high-fidelity design of spectral imaging systems with long slit lengths. The relationship between X-Y polynomials and aberration coefficients is analyzed, and the X-Y polynomial freeform surfaces are used to correct the off-axis aberrations. The design results show that the image quality of the telescope system is close to the diffraction limit. The smile, known as the spectral distortion along the line, and keystone, which is the magnification difference for different wavelengths, of the spectral imaging system are less than 1/10 pixel size. The complete optical system of the NGHSI, including the telescope system and the spectral imaging system, has excellent imaging quality and the layout is compact and reasonable, which realizes the miniaturization design.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"13 3","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139451581","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2024-01-03DOI: 10.3390/photonics11010049
Ilia Bardadin, Vladimir Petrov, Georgy Denisenko, Artashes G. Armaganov, A. Rubekina, Daria Kopytina, Vladimir Panov, P. Shatalov, Victoria Khoronenko, Petr Shegai, Andrey Kaprin, Andrey Shkoda, Boris Yakimov
Non-invasive methods for determining blood hemoglobin (Hb) concentration are urgently needed to avoid the painful and time-consuming process of invasive venous blood sampling. Many such methods rely on assessing the average attenuation of light over a tissue area where hemoglobin is the dominant chromophore, without separating those areas corresponding to vessels and bloodless tissue. In this study, we investigate whether it is possible to determine hemoglobin levels in the blood by assessing the changes in light intensity when passing through large vessels in comparison to adjacent tissues, using this as a Hb level predictor. Using Monte Carlo light transport modeling, we evaluate the accuracy of determining hemoglobin levels via light intensity contrast and vessel widths estimated in the transmittance illumination geometry and estimate the influence of physiologically significant parameters such as vessel depth, dermis vascularization, and melanin content in the epidermis on the blood Hb prediction error. The results show that physiological variations in tissue parameters limit the mean absolute error of this method to ~15 g/L for blood Hb levels varying in the 60–160 g/L range, which finding is also supported by experimental data obtained for volunteers with different total blood Hb levels that have been determined invasively. We believe the application of new approaches to the non-invasive assessment of Hb levels will lead to the creation of reliable and accurate devices that are applicable in point-of-care and clinical practice.
{"title":"Non-Invasive Hemoglobin Assessment with NIR Imaging of Blood Vessels in Transmittance Geometry: Monte Carlo and Experimental Evaluation","authors":"Ilia Bardadin, Vladimir Petrov, Georgy Denisenko, Artashes G. Armaganov, A. Rubekina, Daria Kopytina, Vladimir Panov, P. Shatalov, Victoria Khoronenko, Petr Shegai, Andrey Kaprin, Andrey Shkoda, Boris Yakimov","doi":"10.3390/photonics11010049","DOIUrl":"https://doi.org/10.3390/photonics11010049","url":null,"abstract":"Non-invasive methods for determining blood hemoglobin (Hb) concentration are urgently needed to avoid the painful and time-consuming process of invasive venous blood sampling. Many such methods rely on assessing the average attenuation of light over a tissue area where hemoglobin is the dominant chromophore, without separating those areas corresponding to vessels and bloodless tissue. In this study, we investigate whether it is possible to determine hemoglobin levels in the blood by assessing the changes in light intensity when passing through large vessels in comparison to adjacent tissues, using this as a Hb level predictor. Using Monte Carlo light transport modeling, we evaluate the accuracy of determining hemoglobin levels via light intensity contrast and vessel widths estimated in the transmittance illumination geometry and estimate the influence of physiologically significant parameters such as vessel depth, dermis vascularization, and melanin content in the epidermis on the blood Hb prediction error. The results show that physiological variations in tissue parameters limit the mean absolute error of this method to ~15 g/L for blood Hb levels varying in the 60–160 g/L range, which finding is also supported by experimental data obtained for volunteers with different total blood Hb levels that have been determined invasively. We believe the application of new approaches to the non-invasive assessment of Hb levels will lead to the creation of reliable and accurate devices that are applicable in point-of-care and clinical practice.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"136 49","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2024-01-02DOI: 10.3390/photonics11010047
Qi Yan, Yiwei Tian, Tianqi Zhang, Changjian Lv, Fanchao Meng, Z. Jia, Weiping Qin, G. Qin
Recent years have witnessed growing research interest in dual-wavelength mode-locked fiber lasers for their pivotal role in diverse applications and the exploration of nonlinear dynamics. Despite notable progress in their development, achieving reliable mode-locked dual-wavelength operation typically necessitates intricate manual adjustments of the cavity’s polarization components. In this article, we present the realization of automatic mode-locking in a dual-wavelength soliton fiber laser. To provide guidance for the algorithm design, we systematically investigated the impact of polarization configurations and initial states on the laser’s operation through numerical simulations and linear scan experiments. The results indicate that operational regimes can be finely adjusted around the wave plate position supporting the mode-locked dual-wavelength solution. Furthermore, the laser exhibits multiple stable states at the mode-locked dual-wavelength point, with critical dependence on the initial conditions. Accordingly, we developed a two-stage genetic algorithm that was demonstrated to be effective for realizing automatic dual-wavelength mode-locking. To further improve the performance of the algorithm, a feedforward neural network was trained and integrated into the algorithm, enabling accurate identification of the dual-wavelength states. This study provides valuable insights into understanding how polarization configurations and initial conditions impact the operational regimes of dual-wavelength mode-locked fiber lasers. The algorithm developed can be extended to optimize other systems with multiple stable states supported at the same parameter point.
{"title":"Machine Learning Based Automatic Mode-Locking of a Dual-Wavelength Soliton Fiber Laser","authors":"Qi Yan, Yiwei Tian, Tianqi Zhang, Changjian Lv, Fanchao Meng, Z. Jia, Weiping Qin, G. Qin","doi":"10.3390/photonics11010047","DOIUrl":"https://doi.org/10.3390/photonics11010047","url":null,"abstract":"Recent years have witnessed growing research interest in dual-wavelength mode-locked fiber lasers for their pivotal role in diverse applications and the exploration of nonlinear dynamics. Despite notable progress in their development, achieving reliable mode-locked dual-wavelength operation typically necessitates intricate manual adjustments of the cavity’s polarization components. In this article, we present the realization of automatic mode-locking in a dual-wavelength soliton fiber laser. To provide guidance for the algorithm design, we systematically investigated the impact of polarization configurations and initial states on the laser’s operation through numerical simulations and linear scan experiments. The results indicate that operational regimes can be finely adjusted around the wave plate position supporting the mode-locked dual-wavelength solution. Furthermore, the laser exhibits multiple stable states at the mode-locked dual-wavelength point, with critical dependence on the initial conditions. Accordingly, we developed a two-stage genetic algorithm that was demonstrated to be effective for realizing automatic dual-wavelength mode-locking. To further improve the performance of the algorithm, a feedforward neural network was trained and integrated into the algorithm, enabling accurate identification of the dual-wavelength states. This study provides valuable insights into understanding how polarization configurations and initial conditions impact the operational regimes of dual-wavelength mode-locked fiber lasers. The algorithm developed can be extended to optimize other systems with multiple stable states supported at the same parameter point.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"30 3","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139452173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2024-01-02DOI: 10.3390/photonics11010046
Andrei Ben Amar Baranga, G. Koganov, D. Levron, Gabriel Bialolenker, R. Shuker
Many quantum device signals are proportional to the number of the participating atoms that take part in the detection devices. Among these are optical magnetometers, atomic clocks, quantum communications and atom interferometers. One way to enhance the signal-to-noise ratio is to introduce atom entanglement that increases the signal in a super-radiant-like effect. A coherent em field inside a laser cavity is suggested to achieve atoms’ correlation/entanglement. This may also play an important role in the basic quantum arena of many-body physics. An initial novel experiment to test the realization of atoms’ correlation is described here. A Cs optical magnetometer is used as a tool to test the operation of a cell-in-cavity laser and its characteristics. A vapor cell is inserted into an elongated external cavity of the pump laser in Littrow configuration. Higher atom polarization and reduced laser linewidth are obtained leading to better magnetometer sensitivity and signal-to-noise ratio. The Larmor frequency changes of the Free Induction Decay of optically pumped Cs atomic polarization in the ambient earth magnetic field at room temperature is measured. Temporal changes in the magnetic field of less than 10 pT/√Hz are measured. The first-order dependence of the magnetic field on temperature and temperature gradients is eliminated, important in many practical applications. Single and gradiometric magnetometer configurations are presented.
{"title":"Quantum Applications of an Atomic Ensemble Inside a Laser Cavity","authors":"Andrei Ben Amar Baranga, G. Koganov, D. Levron, Gabriel Bialolenker, R. Shuker","doi":"10.3390/photonics11010046","DOIUrl":"https://doi.org/10.3390/photonics11010046","url":null,"abstract":"Many quantum device signals are proportional to the number of the participating atoms that take part in the detection devices. Among these are optical magnetometers, atomic clocks, quantum communications and atom interferometers. One way to enhance the signal-to-noise ratio is to introduce atom entanglement that increases the signal in a super-radiant-like effect. A coherent em field inside a laser cavity is suggested to achieve atoms’ correlation/entanglement. This may also play an important role in the basic quantum arena of many-body physics. An initial novel experiment to test the realization of atoms’ correlation is described here. A Cs optical magnetometer is used as a tool to test the operation of a cell-in-cavity laser and its characteristics. A vapor cell is inserted into an elongated external cavity of the pump laser in Littrow configuration. Higher atom polarization and reduced laser linewidth are obtained leading to better magnetometer sensitivity and signal-to-noise ratio. The Larmor frequency changes of the Free Induction Decay of optically pumped Cs atomic polarization in the ambient earth magnetic field at room temperature is measured. Temporal changes in the magnetic field of less than 10 pT/√Hz are measured. The first-order dependence of the magnetic field on temperature and temperature gradients is eliminated, important in many practical applications. Single and gradiometric magnetometer configurations are presented.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"49 26","pages":""},"PeriodicalIF":2.4,"publicationDate":"2024-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139390230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2023-12-31DOI: 10.3390/photonics11010042
P. Nikiforova, A. Bogatskaya, Alexander Popov
In this work, we consider the possibility of enhancing terahertz bolometric detection efficiency using resonant structures in the case of an inclined incidence of radiation. The structures are made of a sequence of doped and undoped semiconductors, including epsilon-near-zero areas. Undoped regions act as electromagnetic resonators, thus ensuring resonant signal penetration through the opaque (doped) regions of the structure. A set of epsilon-near-zero areas can ensure substantial enhancements to the electric field in the material. In the doped regions, absorption occurs. The structure described above can provide efficient resonant energy absorption for a wide range of angles of incidence. The numerical calculations based on the solution of the Helmholtz equation have shown that the studied resonant structures ensure the absorption of up to 50% of the incident radiation energy for a 60-degree incidence.
{"title":"Enhanced Bolometric Detection of THz Signals by a Resonant Structure for Inclined Radiation Incidence","authors":"P. Nikiforova, A. Bogatskaya, Alexander Popov","doi":"10.3390/photonics11010042","DOIUrl":"https://doi.org/10.3390/photonics11010042","url":null,"abstract":"In this work, we consider the possibility of enhancing terahertz bolometric detection efficiency using resonant structures in the case of an inclined incidence of radiation. The structures are made of a sequence of doped and undoped semiconductors, including epsilon-near-zero areas. Undoped regions act as electromagnetic resonators, thus ensuring resonant signal penetration through the opaque (doped) regions of the structure. A set of epsilon-near-zero areas can ensure substantial enhancements to the electric field in the material. In the doped regions, absorption occurs. The structure described above can provide efficient resonant energy absorption for a wide range of angles of incidence. The numerical calculations based on the solution of the Helmholtz equation have shown that the studied resonant structures ensure the absorption of up to 50% of the incident radiation energy for a 60-degree incidence.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":" 17","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139135786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2023-12-31DOI: 10.3390/photonics11010043
Zhigang Su, Chengxu Hu, Jingtang Hao, Peng Ge, Bing Han
To enhance the detection capability of weak targets and reduce the dependence of single-photon lidar target detection on the number of the time-correlated single-photon counting detection cycles, a convolutional neural network (CNN) based on the point cloud (CNN-PC) method is proposed in this paper for detecting targets in single-photon lidar. This approach utilizes the exceptional feature extraction capabilities offered by CNN. The CNN-PC method utilizes the feature extraction module of the trained CNN to simultaneously extract features from two-dimensional point cloud slices. Subsequently, it combines these features and feeds them into the classification module of the trained CNN for final target detection. By training the CNN using point cloud slices generated with a minimal number of detection cycles and employing a parallel structure to extract features from multiple point cloud slices, the CNN-PC method exhibits remarkable flexibility in adapting to varying numbers of detection cycles. Both simulation and experimental results demonstrate that the CNN-PC method outperforms the classical constant false alarm rate method in terms of the target detection probability at the same signal-to-noise ratio and in terms of the imaging rate and error rate at the same number of detection cycles.
{"title":"Target Detection in Single-Photon Lidar Using CNN Based on Point Cloud Method","authors":"Zhigang Su, Chengxu Hu, Jingtang Hao, Peng Ge, Bing Han","doi":"10.3390/photonics11010043","DOIUrl":"https://doi.org/10.3390/photonics11010043","url":null,"abstract":"To enhance the detection capability of weak targets and reduce the dependence of single-photon lidar target detection on the number of the time-correlated single-photon counting detection cycles, a convolutional neural network (CNN) based on the point cloud (CNN-PC) method is proposed in this paper for detecting targets in single-photon lidar. This approach utilizes the exceptional feature extraction capabilities offered by CNN. The CNN-PC method utilizes the feature extraction module of the trained CNN to simultaneously extract features from two-dimensional point cloud slices. Subsequently, it combines these features and feeds them into the classification module of the trained CNN for final target detection. By training the CNN using point cloud slices generated with a minimal number of detection cycles and employing a parallel structure to extract features from multiple point cloud slices, the CNN-PC method exhibits remarkable flexibility in adapting to varying numbers of detection cycles. Both simulation and experimental results demonstrate that the CNN-PC method outperforms the classical constant false alarm rate method in terms of the target detection probability at the same signal-to-noise ratio and in terms of the imaging rate and error rate at the same number of detection cycles.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"124 6","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139134916","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2023-12-31DOI: 10.3390/photonics11010045
Nikolay A. Aprelov, Ilya D. Vatnik, D. Kharenko, Alexey A. Redyuk
Dispersive Fourier transform (DFT) has emerged as a powerful technique, enabling the transformation of spectral information from an optical pulse into a temporal waveform. This advancement facilitates the implementation of absorption spectroscopy using a single-pixel photodetector and a pulsed laser, particularly effective when operating on wavelengths near the absorption lines of the gas under study. This paper introduces a DFT-spectrometer employing a mode-locked tunable fiber laser with the central wavelength of 1531.6 nm. We demonstrate fast acquisition NH3 absorption spectroscopy with a 0.2 nm spectral resolution, achieved through the utilization of the HITRAN database for estimating ammonia concentrations. Alongside the successful demonstration of NH3 absorption spectroscopy, we explore practical limiting factors influencing the system’s performance. Furthermore, we discuss potential avenues for enhancing sensitivity and spectral resolution, aiming to enable more robust and accurate gas sensing applications.
{"title":"Dispersive Fourier Transform Spectrometer Based on Mode-Locked Er-Doped Fiber Laser for Ammonia Sensing","authors":"Nikolay A. Aprelov, Ilya D. Vatnik, D. Kharenko, Alexey A. Redyuk","doi":"10.3390/photonics11010045","DOIUrl":"https://doi.org/10.3390/photonics11010045","url":null,"abstract":"Dispersive Fourier transform (DFT) has emerged as a powerful technique, enabling the transformation of spectral information from an optical pulse into a temporal waveform. This advancement facilitates the implementation of absorption spectroscopy using a single-pixel photodetector and a pulsed laser, particularly effective when operating on wavelengths near the absorption lines of the gas under study. This paper introduces a DFT-spectrometer employing a mode-locked tunable fiber laser with the central wavelength of 1531.6 nm. We demonstrate fast acquisition NH3 absorption spectroscopy with a 0.2 nm spectral resolution, achieved through the utilization of the HITRAN database for estimating ammonia concentrations. Alongside the successful demonstration of NH3 absorption spectroscopy, we explore practical limiting factors influencing the system’s performance. Furthermore, we discuss potential avenues for enhancing sensitivity and spectral resolution, aiming to enable more robust and accurate gas sensing applications.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"120 2","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139133173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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}
Pub Date : 2023-12-31DOI: 10.3390/photonics11010044
Lei Xin, Xiao Xu, Liuge Du, Jia Zhao
We propose an FSK/ASK orthogonal modulation system based on a novel noncoherent detection (NCD) scheme, aimed at expanding the system capacity for short-reach optical communications cost-effectively. In the transmitter, the FSK optical signal is generated by simple frequency modulation through a directly modulated distributed feedback laser. Subsequently, by utilizing a Mach–Zehnder modulator for ASK modulation, the FSK/ASK optical signal is obtained. The novel and low-complexity NCD receiver consists of an intensity detection branch and a frequency detection branch. The frequency detection branch is composed of an optical differentiator, a photodetector, and frequency extraction circuits. Notably, the proposed NCD scheme overcomes the limitation of the traditional FSK/ASK-NCD receiver stemming from the trade-off between the detected signal quality of the amplitude and frequency. Furthermore, electronic dispersion compensation (EDC) is available. Through numerical simulations, our findings demonstrate that the proposed FSK/ASK-NCD system, assisted by EDC, achieves a remarkable 100 km transmission span for both 40 Gbps 2FSK/2ASK and 60 Gbps 2FSK/4ASK modulation formats, which surpasses the 2ASK-DD and the 4ASK-DD systems, where the maximum achievable spans are limited to less than 20 km. These results underscore the potential of the proposed system as a robust candidate for future passive optical access networks.
{"title":"FSK/ASK Orthogonal Modulation System Based on Novel Noncoherent Detection and Electronic Dispersion Compensation for Short-Reach Optical Communications","authors":"Lei Xin, Xiao Xu, Liuge Du, Jia Zhao","doi":"10.3390/photonics11010044","DOIUrl":"https://doi.org/10.3390/photonics11010044","url":null,"abstract":"We propose an FSK/ASK orthogonal modulation system based on a novel noncoherent detection (NCD) scheme, aimed at expanding the system capacity for short-reach optical communications cost-effectively. In the transmitter, the FSK optical signal is generated by simple frequency modulation through a directly modulated distributed feedback laser. Subsequently, by utilizing a Mach–Zehnder modulator for ASK modulation, the FSK/ASK optical signal is obtained. The novel and low-complexity NCD receiver consists of an intensity detection branch and a frequency detection branch. The frequency detection branch is composed of an optical differentiator, a photodetector, and frequency extraction circuits. Notably, the proposed NCD scheme overcomes the limitation of the traditional FSK/ASK-NCD receiver stemming from the trade-off between the detected signal quality of the amplitude and frequency. Furthermore, electronic dispersion compensation (EDC) is available. Through numerical simulations, our findings demonstrate that the proposed FSK/ASK-NCD system, assisted by EDC, achieves a remarkable 100 km transmission span for both 40 Gbps 2FSK/2ASK and 60 Gbps 2FSK/4ASK modulation formats, which surpasses the 2ASK-DD and the 4ASK-DD systems, where the maximum achievable spans are limited to less than 20 km. These results underscore the potential of the proposed system as a robust candidate for future passive optical access networks.","PeriodicalId":20154,"journal":{"name":"Photonics","volume":"94 4","pages":""},"PeriodicalIF":2.4,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139131768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"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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