-
Comparison between the Propagation Properties of Bessel–Gauss and Generalized Laguerre–Gauss Beams
-
Assessment of the Impact of Nanowarming on Microstructure of Cryopreserved Fibroblast-Containing 3D Tissue Models Using Mueller Polarimetry
-
Laser Output Performance and Temporal Quality Enhancement at the J-KAREN-P Petawatt Laser Facility
-
Development and Calibration of a Vertical High-Speed Mueller Matrix Ellipsometer
-
Stable Emissions from a Four-Rod Nd:YAG Solar Laser with ±0.5° Tracking Error Compensation Capacity
Journal Description
Photonics
Photonics
is an international, scientific, peer-reviewed, open access journal on the science and technology of optics and photonics, published monthly online by MDPI.
- Open Access— free for readers, with article processing charges (APC) paid by authors or their institutions.
- High Visibility: indexed within Scopus, SCIE (Web of Science), Inspec, CAPlus / SciFinder, and other databases.
- Rapid Publication: manuscripts are peer-reviewed and a first decision is provided to authors approximately 15.7 days after submission; acceptance to publication is undertaken in 2.8 days (median values for papers published in this journal in the first half of 2023).
- Recognition of Reviewers: reviewers who provide timely, thorough peer-review reports receive vouchers entitling them to a discount on the APC of their next publication in any MDPI journal, in appreciation of the work done.
- Companion journal: Optics.
Impact Factor:
2.4 (2022);
5-Year Impact Factor:
2.4 (2022)
Latest Articles
Generation of a Flat Optical Frequency Comb via a Cascaded Dual-Parallel Mach–Zehnder Modulator and Phase Modulator without Using the Fundamental Tone
Photonics 2023, 10(12), 1340; https://doi.org/10.3390/photonics10121340 - 04 Dec 2023
Abstract
Under the conventional scheme to generate an optical frequency comb (OFC) using an electro-optic modulator (EOM), the frequency interval of the OFC is determined via the frequency of the fundamental tone of the radio frequency (RF) driving signals. In this work, we use
[...] Read more.
Under the conventional scheme to generate an optical frequency comb (OFC) using an electro-optic modulator (EOM), the frequency interval of the OFC is determined via the frequency of the fundamental tone of the radio frequency (RF) driving signals. In this work, we use two harmonics without the fundamental tone to drive two EOMs, where the frequency interval of the generated flat OFC is the frequency of the fundamental tone. The orders of the two harmonics are coprime. Specifically, one harmonic drives the first branch of the dual-parallel Mach–Zehnder modulator (DPMZM) only, and the other harmonic drives the phase modulator (PM). The flatness of the OFC is achieved by adjusting the amplitude and phase of the RF driving harmonics as well as the bias of the EOM. Both a simulation and an experiment were carried out to verify the effectiveness of the proposed scheme. When the second harmonic drives the DPMZM and the third harmonic drives the PM, an 11-comb line OFC is generated, where the flatness of the OFC was 0.63 dB and 0.65 dB under the simulation and experiment, respectively. When the third harmonic drives the DPMZM and the second harmonic drives the PM, a 13-comb line OFC is generated, where the flatness of the OFC was 0.62 dB and 0.95 dB under the simulation and experiment, respectively. We also investigate the performance of the generated OFC when one harmonic drives two branches of the DPMZM and the other harmonic drives the PM. The comparison of the OFCs’ performance demonstrates the effectiveness of the proposed scheme.
Full article
(This article belongs to the Special Issue Microwave Photonics and Applications)
►
Show Figures
Open AccessArticle
Experimental Study on the Temporal Evolution Parameters of Laser–Produced Tin Plasma under Different Laser Pulse Energies for LPP–EUV Source
Photonics 2023, 10(12), 1339; https://doi.org/10.3390/photonics10121339 - 04 Dec 2023
Abstract
►▼
Show Figures
The laser–produced plasma extreme ultraviolet (LPP–EUV) source is the sole light source currently available for commercial EUVL (extreme ultraviolet lithography) machines. The plasma parameters, such as the electron temperature and electron density, affect the conversion efficiency (CE) of extreme ultraviolet radiation and other
[...] Read more.
The laser–produced plasma extreme ultraviolet (LPP–EUV) source is the sole light source currently available for commercial EUVL (extreme ultraviolet lithography) machines. The plasma parameters, such as the electron temperature and electron density, affect the conversion efficiency (CE) of extreme ultraviolet radiation and other critical parameters of LPP–EUV source directly. In this paper, the optical emission spectroscopy (OES) was employed to investigate the time–resolved plasma parameters generated by an Nd:YAG laser irradiation on a planar tin target. Assuming that the laser–produced tin plasma satisfies the local thermodynamic equilibrium (LTE) condition, the electron temperature and electron density of the plasma were calculated by the Saha–Boltzmann plot and Stark broadening methods. The experimental results revealed that during the early stage of plasma formation (delay time < 50 ns), there was a significant presence of continuum emission. Subsequently, the intensity of the continuum emission gradually decreased, while line spectra emerged and became predominant at a delay time of 300 ns. In addition, the evolution trend of plasma parameters, with the incident laser pulse energy set at 300 mJ, was characterized by a rapid initial decrease followed by a gradual decline as the delay time increased. Furthermore, with an increase in the incident laser pulse energy from 300 mJ to 750 mJ, the electron temperature and electron density of laser–produced tin plasma exhibiting a monotonically showed increasing trend at the same delay time.
Full article

Figure 1
Open AccessArticle
Speckle-Reduced Optical Coherence Tomography Using a Tunable Quasi-Supercontinuum Source
Photonics 2023, 10(12), 1338; https://doi.org/10.3390/photonics10121338 - 03 Dec 2023
Abstract
Optical coherence tomography (OCT), which has long been used for fine-scale structure imaging with higher resolution, larger penetration depth, and more detailed information, is a fast-growing technique for biological tissue imaging. However, speckle is an inherent property in OCT, appearing as bright and
[...] Read more.
Optical coherence tomography (OCT), which has long been used for fine-scale structure imaging with higher resolution, larger penetration depth, and more detailed information, is a fast-growing technique for biological tissue imaging. However, speckle is an inherent property in OCT, appearing as bright and dark granular patterns, and hinders the visibility of the fine-scale structure. For the first time, we demonstrated speckle-reduced high-resolution imaging using a tunable quasi-supercontinuum (SC) source. OCT images with uncorrelated speckle patterns could be obtained by several quasi-SC spectra and compounded to improve the image quality. We confirmed that the implementation of a quasi-SC source enables us to reduce speckle noise for better observation of fine-scale structure.
Full article
(This article belongs to the Section Biophotonics and Biomedical Optics)
►▼
Show Figures

Figure 1
Open AccessArticle
Fast and Accurate Measurement of Hole Systems in Curved Surfaces
Photonics 2023, 10(12), 1337; https://doi.org/10.3390/photonics10121337 - 02 Dec 2023
Abstract
Curved surface structural parts with hole systems are widely used, and accurate measurement of the hole systems is crucial for assembly and functionality. This study presents a novel approach using machine vision and structural science principles to accurately measure spherical hole systems. We
[...] Read more.
Curved surface structural parts with hole systems are widely used, and accurate measurement of the hole systems is crucial for assembly and functionality. This study presents a novel approach using machine vision and structural science principles to accurately measure spherical hole systems. We introduce key technologies, including measurement parameter definition, system design, and error modeling, in the paper. Our approach overcomes the limitations of existing methods, offering flexibility, precision, and automation measurement of the hole system. Experimental results demonstrate an accuracy of 0.348′ (arcminutes). This research contributes to the optical measurement of curved surface hole systems and improves their alignment and functionality.
Full article
(This article belongs to the Special Issue State-of-the-Art Optical Inspection Technology)
►▼
Show Figures

Figure 1
Open AccessArticle
UV Absorption Spectrum for Dissolved Oxygen Monitoring: A Low-Cost Proposal for Water Quality Monitoring
Photonics 2023, 10(12), 1336; https://doi.org/10.3390/photonics10121336 - 01 Dec 2023
Abstract
One of the key indicators of water quality is dissolved oxygen. Even though oxygen is important in environmental monitoring, the sensors for dissolved oxygen are expensive and require periodic maintenance due to the use of membranes. In this paper, we propose using ultraviolet
[...] Read more.
One of the key indicators of water quality is dissolved oxygen. Even though oxygen is important in environmental monitoring, the sensors for dissolved oxygen are expensive and require periodic maintenance due to the use of membranes. In this paper, we propose using ultraviolet light absorption to estimate dissolved oxygen saturation in water samples. The absorption spectrum of dissolved oxygen in the ultraviolet range is investigated over a water matrix with different levels of complexity. First, the difference between different water matrixes is studied. The results indicate similar variations between river water and tap water matrices for comparative purposes. Both samples present much higher absorbance signals than distilled water. Thus, the rest of the tests were performed with only three water matrixes (ultrapure, distilled, and river water). By aerating, water samples were completely saturated. Then, nitrogen gas was used to remove dissolved oxygen from samples to obtain saturations of 75, 50, 25, and 3%. The absorption was measured from 190 to 380 nm, using LLG-uniSPEC 2. The obtained data were used to generate regression models for selected wavelengths (190, 210, 240, and 250 nm). The differences beyond 260 nm for the studied dissolved oxygen saturations were null. The generated models had correlation coefficients from 0.99 to 0.97 for ultrapure water, 0.98 to 0.95 for distilled water, and 0.90 to 0.83 for river water. The maximum differences were found between samples with 75 and 100% of saturation.
Full article
(This article belongs to the Special Issue Editorial Board Members’ Collection Series: Photonics Sensors)
►▼
Show Figures

Figure 1
Open AccessReview
The 5P3/2→6PJ(J=1/2,3/2) Electric Dipole Forbidden Transitions in Rubidium
by
, , , , , , , , and
Photonics 2023, 10(12), 1335; https://doi.org/10.3390/photonics10121335 - 01 Dec 2023
Abstract
This paper presents a general review of the results of the experimental and theoretical work carried out by our research group to study the electric quadrupole transition in atomic rubidium. The experiments were carried
[...] Read more.
This paper presents a general review of the results of the experimental and theoretical work carried out by our research group to study the electric quadrupole transition in atomic rubidium. The experiments were carried out with room-temperature atoms in an absorption cell. A steady-state population of atoms in the excited state is produced by a a narrow-bandwidth preparation laser locked to the D2 transition. A second CW laser is used to produce the forbidden transition with resolution of the hyperfine states of both rubidium isotopes. The process is detected by recording the 420(422) nm fluorescence that occurs when the atoms in the state decay directly into the ground state. The fluorescence spectra show a strong dependence on the relative polarization directions of the preparation laser and the beam producing the forbidden transition. This dependence is directly related to a strong anisotropy in the populations of the intermediate magnetic substates, and also to the electric quadrupole selection rules over magnetic quantum numbers. A calculation based on the rate equations that includes velocity and detuning dependent transition rates is adequate to reproduce these results. The forbidden transition is also shown to be an ideal probe to measure the Autler–Townes splitting generated in the preparation of the state. Examples of spectra obtained with cold atoms in a magneto-optical trap (MOT) are also presented. These spectra show the expected Autler–Townes doublet structure with asymmetric line profiles that result as a consequence of the red-detuning of the trapping laser in the MOT.
Full article
(This article belongs to the Special Issue Precision Atomic Spectroscopy)
►▼
Show Figures

Figure 1
Open AccessReview
Optical Neuroimaging in Delirium
Photonics 2023, 10(12), 1334; https://doi.org/10.3390/photonics10121334 - 01 Dec 2023
Abstract
Delirium persists as the most common neuropsychiatric syndrome among medically ill hospitalized patients, yet its neural mechanisms remain poorly understood. The development of neuroimaging biomarkers has been difficult primarily due to the complexities of imaging patients experiencing delirium. Optical imaging techniques, including near-infrared
[...] Read more.
Delirium persists as the most common neuropsychiatric syndrome among medically ill hospitalized patients, yet its neural mechanisms remain poorly understood. The development of neuroimaging biomarkers has been difficult primarily due to the complexities of imaging patients experiencing delirium. Optical imaging techniques, including near-infrared spectroscopy (NIRS) and diffuse optical tomography (DOT), offer promising avenues for investigating delirium’s pathophysiology. These modalities uniquely stand out for delirium exploration due to their blend of spatiotemporal resolution, bedside applicability, cost-effectiveness, and potential for real-time monitoring. In this review, we examine the emergence of optical imaging modalities and their pioneering utility in delirium research. With further investment and research efforts, they will become instrumental in our understanding of delirium’s pathophysiology and the development of preventive, predictive, and therapeutic strategies.
Full article
(This article belongs to the Special Issue Progress in Neurophotonics and Its Future Perspectives)
Open AccessArticle
The Flatness Error Evaluation of Metal Workpieces Based on Line Laser Scanning Digital Imaging Technology
Photonics 2023, 10(12), 1333; https://doi.org/10.3390/photonics10121333 - 30 Nov 2023
Abstract
With the development of intelligent manufacturing, the production and assembly accuracy of components in factories is increasing in line with growing demand. However, the traditional manual quality inspection is inefficient, inaccurate, and costly. To this end, digital and optical imaging techniques are used
[...] Read more.
With the development of intelligent manufacturing, the production and assembly accuracy of components in factories is increasing in line with growing demand. However, the traditional manual quality inspection is inefficient, inaccurate, and costly. To this end, digital and optical imaging techniques are used to achieve intelligent quality inspection. However, during the reconstruction process, the high reflectivity of object materials affects the speed and accuracy of reconstruction results. To overcome these problems, this study investigated the three-dimensional (3D) digital imaging techniques based on line laser scanning. It advances a novel methodology for image segmentation, underpinned by deep learning algorithms, to augment the precision of the reconstruction results while simultaneously enhancing processing velocity. After the reconstruction phase, the research assesses flatness tolerance using point cloud registration technology. Finally, we constructed a measurement platform with a cost of less than CNY 100,000 (about USD 14,000) and obtained a measurement accuracy of 30 microns.
Full article
(This article belongs to the Special Issue Emerging Topics in Structured Light)
►▼
Show Figures

Figure 1
Open AccessArticle
Modeling of Subwavelength Gratings: Near-Field Behavior
Photonics 2023, 10(12), 1332; https://doi.org/10.3390/photonics10121332 - 30 Nov 2023
Abstract
Subwavelength gratings have received considerable attention in the fields of photonics, optoelectronics, and image sensing. This paper presents simple analytical expressions for the near-field intensity distribution of radiation scattered by these gratings. Our proposed methodology employs a 2D point dipole model and a
[...] Read more.
Subwavelength gratings have received considerable attention in the fields of photonics, optoelectronics, and image sensing. This paper presents simple analytical expressions for the near-field intensity distribution of radiation scattered by these gratings. Our proposed methodology employs a 2D point dipole model and a specialized version of perturbation theory. By validating our models via numerical techniques including boundary and finite element methods, we demonstrate their effectiveness, even for narrow slits.
Full article
(This article belongs to the Section New Applications Enabled by Photonics Technologies and Systems)
►▼
Show Figures

Figure 1
Open AccessArticle
Optical Wireless Fronthaul-Enhanced High-Throughput FC-AE-1553 Space Networks
Photonics 2023, 10(12), 1331; https://doi.org/10.3390/photonics10121331 - 30 Nov 2023
Abstract
Existing space application networks in space stations are mainly fiber-optic cable-based networks due to their low size, weight, and power (SWaP) values. While fiber networks in space stations offer data transmission at high speeds with minimal signal loss, their major disadvantage is the
[...] Read more.
Existing space application networks in space stations are mainly fiber-optic cable-based networks due to their low size, weight, and power (SWaP) values. While fiber networks in space stations offer data transmission at high speeds with minimal signal loss, their major disadvantage is the lack of flexibility and mobility when new and unplanned space scientific equipment is added to the network. To enhance the flexibility of space networks while increasing their throughput, this paper introduces the hybrid space network (HSN), a new space network architecture that incorporates an optical wireless link, to meet the ever-increasing demands for larger bandwidth and higher mobile access capabilities in space scientific experiments. To best utilize the HSN’s system performance, we propose a multi-priority-based network scheduling scheme, which can dynamically adapt to the requirements of mass tasks and select the best transmission procedure. Through simulations, we find that by adding optical wireless communication (OWC) links to the state-of-the-art deterministic FC-AE-1553 space network, the HSN’s bandwidth can be increased by 20 times with an average latency reduction of 87.3%. We believe that the proposed HSN’s architecture may ultimately shape the future of space stations’ wireless connectivity, and in the meantime, innovate many advanced space applications with larger data rates and mobility requirements.
Full article
(This article belongs to the Special Issue Enabling Technologies for Optical Communications and Networking)
►▼
Show Figures

Figure 1
Open AccessArticle
Self-Phase Modulation-Induced Instability of High-Power Narrow-Linewidth Fiber Amplifiers
Photonics 2023, 10(12), 1330; https://doi.org/10.3390/photonics10121330 - 30 Nov 2023
Abstract
►▼
Show Figures
In this study, we investigated the effect of self-phase modulation (SPM)-induced modulation instability (MI) on the spectral purity of high-power narrow-linewidth fiber amplifiers and established a spectral evolution model for SPM-induced MI in those amplifiers. The spectral evolution process of MI under different
[...] Read more.
In this study, we investigated the effect of self-phase modulation (SPM)-induced modulation instability (MI) on the spectral purity of high-power narrow-linewidth fiber amplifiers and established a spectral evolution model for SPM-induced MI in those amplifiers. The spectral evolution process of MI under different laser powers was simulated and analyzed. The results show that, at low power (100 W), SPM can cause a dynamic change in the spectral sideband secondary peak and the spectral wingspan. An increase in laser power led to the cascade effect of MI, forming a zigzag secondary sideband with a larger spectral width and causing the spectral main peak and spectral broadening to split. Experiments based on the fiber Bragg grating (FBG) of oscillating seed sources were carried out on high-power narrow-linewidth laser amplifiers, and the above spectral evolution phenomenon was observed. The experimental results indicate that the spectral evolution model based on SPM-induced MI can effectively explain the dynamic change in the spectral secondary peak, spectral wingspan and zigzag broadening phenomenon in the power amplification process of narrow-linewidth lasers.
Full article

Figure 1
Open AccessArticle
Design and Experimental Validation of an Optical Autofocusing System with Improved Accuracy
Photonics 2023, 10(12), 1329; https://doi.org/10.3390/photonics10121329 - 30 Nov 2023
Abstract
This study proposes a modified optical design to improve the issue of autofocus accuracy in existing optical systems. The proposed system uses lens offset to convert incident light into non-parallel light, achieving a focus shift and avoiding severe deformation of the light spot
[...] Read more.
This study proposes a modified optical design to improve the issue of autofocus accuracy in existing optical systems. The proposed system uses lens offset to convert incident light into non-parallel light, achieving a focus shift and avoiding severe deformation of the light spot near the focal point of the objective lens. Based on triangulation theory and optical focusing theories such as the centroid method, the proposed optical design improves the shortcomings of existing technology. Experimental results demonstrate that the proposed optical autofocusing system has better autofocus accuracy than traditional systems while also reducing the difficulty of image processing. In summary, the proposed optical system is not only an effective autofocusing technology but also a highly valuable optical inspection and industrial application technology. This system has broader application and development opportunities for future research and practice.
Full article
(This article belongs to the Special Issue Advanced Photonic Sensing and Measurement II)
►▼
Show Figures

Figure 1
Open AccessArticle
The Growth Mechanism, Luminescence, and Lasing of Polyhedral ZnO Microcrystals with Whispering-Gallery Modes
Photonics 2023, 10(12), 1328; https://doi.org/10.3390/photonics10121328 - 29 Nov 2023
Abstract
This work studies the features of the formation of isometric polyhedral ZnO microcrystals that provide stimulated emission and whispering-gallery-mode (WGM) lasing in the near-UV range. For this purpose, the growth stages of such crystals in the process of gas-transport synthesis and the luminescent
[...] Read more.
This work studies the features of the formation of isometric polyhedral ZnO microcrystals that provide stimulated emission and whispering-gallery-mode (WGM) lasing in the near-UV range. For this purpose, the growth stages of such crystals in the process of gas-transport synthesis and the luminescent properties of the structures obtained at each stage were investigated. It was shown that the growth of laser microcrystals begins with the formation of microspheroids with thin ZnO shells. Such spheroids exhibit mainly white luminescence with a small contribution of near-UV emission. Increasing the synthesis duration results in thickening and faceting of the spheroid shells, as well as a decrease in the contribution of the yellow–red component to the luminescence spectrum. At the same time, ZnO microcrystallites nucleate and grow inside the spheroids, using as a material the remains of a liquid zinc drop and oxygen entering the spheroids through their shells. Such growth conditions allow them to take on an equilibrium polyhedral shape. Eventually, upon destruction of the spheroid shell, a polyhedral ZnO microcrystal supporting WGMs is observed.
Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Photonics)
►▼
Show Figures

Figure 1
Open AccessArticle
Ultra-Broadband, Compact Arbitrary-Ratio Multimode Power Splitter Based on Tilted Subwavelength Gratings
by
, , , , , , and
Photonics 2023, 10(12), 1327; https://doi.org/10.3390/photonics10121327 - 29 Nov 2023
Abstract
►▼
Show Figures
Mode division multiplexing (MDM) technology is an effective solution for high-capacity optical interconnection, and multimode power splitters, as essential components in MDM systems, have attracted widespread attention. However, supporting a wide range of modes and arbitrary power splitting ratios with large bandwidth in
[...] Read more.
Mode division multiplexing (MDM) technology is an effective solution for high-capacity optical interconnection, and multimode power splitters, as essential components in MDM systems, have attracted widespread attention. However, supporting a wide range of modes and arbitrary power splitting ratios with large bandwidth in power splitters remains a significant challenge. In this paper, we designed a power splitter based on a subwavelength grating (SWG) structure with tilted placement on a silicon-on-insulator (SOI) substrate. We achieve arbitrary TE0–TE9 mode-insensitive power distribution by altering the filling coefficient of the SWG. Thanks to our specific selection of cladding materials and compensatory design for the optical wave transmission and reflection shifts induced by SWG, our device demonstrates low additional loss (EL < 1.1 dB) and inter-mode crosstalk (−18.8 < CT < −60 dB) for optical modes ranging from TE0 to TE9, covering a wavelength range from 1200 nm to 1700 nm. Furthermore, our proposed device can be easily extended to higher-order modes with little loss of device performance, offering significant potential in MDM platforms.
Full article

Figure 1
Open AccessArticle
Degradation- and Thermal-Related Changes in Selected Electro-Optical Parameters of High-Power 270–280 nm LEDs
Photonics 2023, 10(12), 1326; https://doi.org/10.3390/photonics10121326 - 29 Nov 2023
Abstract
Recently, the rapid development of LED sources emitting high-power radiation in the UVC range has been observed, and there is a growing interest in using these LED sources in practical solutions. The innovative constructions of disinfection and sterilization devices depend on the effectiveness
[...] Read more.
Recently, the rapid development of LED sources emitting high-power radiation in the UVC range has been observed, and there is a growing interest in using these LED sources in practical solutions. The innovative constructions of disinfection and sterilization devices depend on the effectiveness and reliability of UVC radiation sources. At the same time, the literature reports that deep experimental analysis of degradation of high-power LEDs is limited. The aim of this research is to contribute to existing knowledge through a comparative assessment of the changes in optical power, spectral power distribution, and forward voltage drop in time and temperature of exemplary high-power UVC LEDs. For this purpose, a controlled 1500 h degradation of six different high-power UVC LEDs was performed, based on which we determined their expected lifetimes L70, L80, and L90. According to our results, the L80 varies from 180 h to 1500 h. Stronger degradation of optical power was observed with lower current. No significant impact on the spectral parameters was observed. The results also indicate the low influence of temperature on the voltage (<0.12%/°C), optical power (<0.22%/°C), and spectral parameters (peak wavelength Δλ and full width at half maximum ΔFWHM < 0.025 nm/°C).
Full article
(This article belongs to the Section Lasers, Light Sources and Sensors)
►▼
Show Figures

Figure 1
Open AccessArticle
Stable Acoustic Pulling in Two-Dimensional Phononic Crystal Waveguides Based on Mode Manipulation
by
, , , , , , , , , , , and
Photonics 2023, 10(12), 1325; https://doi.org/10.3390/photonics10121325 - 29 Nov 2023
Abstract
Acoustic manipulation is a set of versatile platforms with excellent manipulation capabilities. In recent years, researchers have increasingly achieved specific manipulations beyond the translation and capture of particles. Here, we focus on the acoustic field momentum mechanism that generates an acoustic radiation force
[...] Read more.
Acoustic manipulation is a set of versatile platforms with excellent manipulation capabilities. In recent years, researchers have increasingly achieved specific manipulations beyond the translation and capture of particles. Here, we focus on the acoustic field momentum mechanism that generates an acoustic radiation force (ARF). A phononic crystal (PC) waveguide is established to amplify the forward momentum of the acoustic beam through the mode conversion of the acoustic field. Based on the conservation of momentum, the object gains reverse momentum. Thus, acoustic pulling can be achieved through the mode conversion of the acoustic field. Furthermore, we analyze the ARFs of two identical objects. It turns out that they can be manipulated separately by opposing forces. Our study provides a new way to achieve stable long-range acoustic pulling, and will explore, beneficially, the interaction between acoustic waves and matter.
Full article
(This article belongs to the Special Issue Nanoscale Optical Manipulation: Fundamentals, Current Advancements and Future Prospects)
►▼
Show Figures

Figure 1
Open AccessCommunication
Trajectories of Depressive Individual Symptoms over Time during Transcranial Photobiomodulation
by
, , , , , and
Photonics 2023, 10(12), 1324; https://doi.org/10.3390/photonics10121324 - 29 Nov 2023
Abstract
Transcranial photobiomodulation (t-PBM) is an innovative, non-invasive treatment for depression. This study aimed to investigate the changes in individual depressive symptoms during t-PBM treatment and identify the symptoms that improved in those who responded to treatment. The research analyzed data from two trials,
[...] Read more.
Transcranial photobiomodulation (t-PBM) is an innovative, non-invasive treatment for depression. This study aimed to investigate the changes in individual depressive symptoms during t-PBM treatment and identify the symptoms that improved in those who responded to treatment. The research analyzed data from two trials, the Evaluation of Light-emitting diodes Therapeutic Effect in Depression-2 and -3, focusing on patients with major depressive disorder. The patients received t-PBM treatment on the F3 and F4 regions of the scalp over eight weeks, with symptoms assessed weekly using the Quick Inventory for Depression Symptomatology (QIDS). A response was defined as a 50% or greater reduction in the QIDS score at eight weeks from baseline. Out of the 21 patients analyzed, 4 responded at eight weeks. Neurovegetative symptoms, including sleep disturbances and change in appetite, improved in ≥50% of the patients who had these symptoms at baseline. However, core depressive symptoms, including a depressed mood and lack of energy, persisted in about 80–90% of the patients. The responders showed a more than 75% improvement in these core depressive symptoms. These findings suggest that t-PBM treatment may uniquely alleviate certain neurovegetative symptoms in depression, and the improvement in core depressive symptoms might be linked to a clinical response to this treatment.
Full article
(This article belongs to the Special Issue Brain Photobiomodulation: Searching for Predictive Target Engagement)
►▼
Show Figures

Figure 1
Open AccessReview
Rare-Earth-Doped Selenide Glasses as Laser Materials for the 5–6 μm Spectral Range
by
, , , , , , , and
Photonics 2023, 10(12), 1323; https://doi.org/10.3390/photonics10121323 - 29 Nov 2023
Abstract
This paper provides an overview of mid-infrared lasers based on rare-earth-ion-doped selenide glasses. Laser action was demonstrated at the transitions between the first excited and the ground levels of Ce3+, Pr3+, Nd3+ and Tb3+ ions. The highest
[...] Read more.
This paper provides an overview of mid-infrared lasers based on rare-earth-ion-doped selenide glasses. Laser action was demonstrated at the transitions between the first excited and the ground levels of Ce3+, Pr3+, Nd3+ and Tb3+ ions. The highest output parameters for bulk glass lasers (over 40 mJ of output energy) and wavelength tuning in the range of 4.6–5.6 microns were obtained with Ce3+-doped glass. The highest output parameters for fiber lasers (150 mW at 5.1–5.3 μm under continuous pumping) were demonstrated with Tb3+ ions. The longest lasing wavelengths for any glass laser and tunability within the 5.56–6.01 µm spectral band were shown with Nd3+ ions in a Tb3+-Nd3+ co-doped system.
Full article
(This article belongs to the Special Issue Advanced Solid-State and Fiber Mid-IR Lasers: Novel Materils, Components, Systems and Applications)
►▼
Show Figures

Figure 1
Open AccessArticle
Determining the Orbital Angular Momentum of a Vortex Beam Using Strong Field Ionization
Photonics 2023, 10(12), 1322; https://doi.org/10.3390/photonics10121322 - 29 Nov 2023
Abstract
While interferometric methods exist for classifying vortex states of light, these techniques usually require destroying the beam of interest to determine the light’s OAM. A recent two-color pump-probe experiment employed strong field ionization and beam sculpting to classify vortex beams. Here, we propose
[...] Read more.
While interferometric methods exist for classifying vortex states of light, these techniques usually require destroying the beam of interest to determine the light’s OAM. A recent two-color pump-probe experiment employed strong field ionization and beam sculpting to classify vortex beams. Here, we propose an alternative strong-field method for distinguishing OAM states of light which does not require beam sculpting and instead utilizes a noncollinear terahertz standing wave to probe ionized electrons. We then use classical trajectory Monte Carlo (CTMC) methods to simulate strong-field ionization of helium under this configuration with the terahertz field both on and off. We find that the resulting electron momenta distributions can be used to extract the OAM of the beam, as long as the vortex beam spot size does not exceed 1/4 the terahertz pulse’s wavelength.
Full article
(This article belongs to the Special Issue Atomic and Molecular Processes in Strong Laser Fields)
►▼
Show Figures

Figure 1
Open AccessCommunication
Design of a Novel Broadband Antenna for Photomixer Chips in the Terahertz Frequency Range
Photonics 2023, 10(12), 1321; https://doi.org/10.3390/photonics10121321 - 29 Nov 2023
Abstract
►▼
Show Figures
A novel broadband antenna designed for the terahertz (THz) frequency range is proposed and developed for the THz emitter on a photomixer chip. This THz emitter comprises an ultra-high-speed indium phosphide photodetector integrated with a planar THz antenna. This paper presents a novel
[...] Read more.
A novel broadband antenna designed for the terahertz (THz) frequency range is proposed and developed for the THz emitter on a photomixer chip. This THz emitter comprises an ultra-high-speed indium phosphide photodetector integrated with a planar THz antenna. This paper presents a novel broadband antenna configuration comprising a combination of bowtie and circular patch elements designed for the frequency range of 150 GHz to 500 GHz. Detailed parametric analysis of the antenna’s design parameters is also provided. The simulation results demonstrate that the optimized antenna achieves an impedance bandwidth of 350 GHz, satisfying the |S11| ≤ −10 dB condition, and exhibits a relative bandwidth of 107% within the 150 GHz to 500 GHz frequency range. This novel broadband terahertz antenna showcases an exceptional wideband performance and is highly suitable for high-speed transmission systems.
Full article

Figure 1

Journal Menu
► ▼ Journal Menu-
- Photonics Home
- Aims & Scope
- Editorial Board
- Reviewer Board
- Topical Advisory Panel
- Instructions for Authors
- Special Issues
- Topics
- Sections & Collections
- Article Processing Charge
- Indexing & Archiving
- Editor’s Choice Articles
- Most Cited & Viewed
- Journal Statistics
- Journal History
- Journal Awards
- Conferences
- Editorial Office
Journal Browser
► ▼ Journal BrowserHighly Accessed Articles
Latest Books
E-Mail Alert
News
Topics
Topic in
Applied Sciences, BDCC, Photonics, Processes, Remote Sensing, Automation
Advances in AI-Empowered Beamline Automation and Data Science in Advanced Photon Sources
Topic Editors: Yi Zhang, Xiaogang Yang, Chunpeng Wang, Junrong ZhangDeadline: 20 December 2023
Topic in
Applied Sciences, Sensors, Electronics, Photonics, JSAN, Telecom
Machine Learning in Communication Systems and Networks
Topic Editors: Yichuang Sun, Haeyoung Lee, Oluyomi SimpsonDeadline: 31 December 2023
Topic in
Entropy, Photonics, Physics, Plasma, Universe, Fractal Fract, Condensed Matter
Applications of Photonics, Laser, Plasma and Radiation Physics
Topic Editors: Viorel-Puiu Paun, Eugen Radu, Maricel Agop, Mircea OlteanuDeadline: 30 March 2024
Topic in
Drones, Electronics, Land, Photonics, Remote Sensing, Sensors
Hyperspectral Imaging and Signal Processing
Topic Editors: Yinnian Liu, Bing Zhang, Liangpei Zhang, Chenchao Xiao, Yueming Wang, Yongguang Zhang, Qingli Li, Yuwei Chen, Jianxin Jia, Mingyang ZhangDeadline: 31 March 2024

Conferences
Special Issues
Special Issue in
Photonics
Application of Adaptive Optics Theory and Technology in Optical Wireless Communication
Guest Editor: Xizheng KeDeadline: 15 December 2023
Special Issue in
Photonics
Recent Trends in Computational Photonics
Guest Editors: Yuntian Chen, Wei E. I. ShaDeadline: 20 December 2023
Special Issue in
Photonics
Integrated Waveguide-Based Photonic Devices
Guest Editors: Qiancheng Zhao, Li ShenDeadline: 31 December 2023
Special Issue in
Photonics
Mechanisms, Applications and Development of Microstructure-Based Fiber Devices
Guest Editors: Guiyao Zhou, Jinghua Sun, Boyao LiDeadline: 1 January 2024
Topical Collections
Topical Collection in
Photonics
Advances in 3OM: Opto-Mechatronics, Opto-Mechanics, and Optical Metrology
Collection Editors: Virgil-Florin Duma, Guillermo Garcia-Torales, Tomohiko Hayakawa