Band Laser Research Articles

Remote sensing of backward reflection from stimulated axion decay

We propose a method for remotely detecting backward reflection via induced decay of cold dark matter such as axion in the background of a propagating coherent photon field. This method can be particularly useful for probing concentrated dark matter streams by Earth’s gravitational lensing effect. Formulae for the stimulated reflection process and the expected sensitivities in local and remote experimental approaches are provided for testing eV scale axion models using broad band lasers. The generic axion-photon coupling is expected to be explorable up to O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(10−12) GeV−1 and O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(10−22) GeV−1 for the idealized local and remote setups, respectively.

Simultaneous transmission of multi-format signals in the mid-infrared over free space

Mid-infrared (MIR) light within the 3–5 μm spectrum offers distinct advantages over the 1.5 μm band, particularly in adverse atmospheric conditions, rendering it a favorable option for free-space optical (FSO) communication. The transmission capacity within the 3–5 μm band is relatively low due to the immature state of its devices. In this study, we demonstrate multi-format signals FSO transmission with a total of 40 Gbps capacity in the 3 μm band, utilizing our developed MIR transmitter and receiver modules. These modules facilitate wavelength conversion between the 1.5 μm and 3 μm bands through the utilization of difference-frequency generation (DFG) effect. The MIR transmitter effectively produces three MIR signals: On-Off Keying (OOK), Binary Phase Shift Keying (BPSK), and Quadrature Phase Shift Keying (QPSK) optical signals. The generated MIR power is 7.8 dBm, covering a wavelength range from 3.5864 to 3.5885 μm. The MIR receiver regenerates the three format signals with a power of −29.6 dBm. Relevant results of regenerated signal demodulation have been collected in detail, including bit error ratio (BER), constellation diagram, and eye diagram. The required powers for the 10 Gbps OOK, BPSK, and QPSK are −37.82, −40.24, and −39.4 dBm at BER of 1 × 10−6. It is expected to further push the data capacity to the terabit-per-second level by adding more 1.5 μm band laser sources and using wider-bandwidth chirped nonlinear crystals.

Direct Drive Laser Fusion Facility and Pilot Plant

Direct-drive laser inertial fusion is a potential producer of baseline power that has increased credibility following the achievement at the National Ignition Facility of ignition and net gain using indirect-drive via laser-produced X-rays. Ultraviolet broad band lasers such as argon fluoride, at 193 nm and 10 THz, are predicted by hydrocode simulations to enable energy gains greater than 100 with laser energies less than 0.5 MJ, stimulating renewed reactor design effort in anticipation of experimental verification. The present study attempts to create a reactor design with very few unknowns in materials, corrosion, first wall viability, tritium breeding and ease of servicing. A new variant of magnetic intervention has an increased ion dump surface area combined with a simple structure. Around an inner vacuum vessel an all-ceramic tritium breeder blanket is possible in an unconstrained volume, allowing helium coolant to be used without excessive pressure or flow power. The case is made for development of a lead (Pb) ceramic as the neutron multiplier.

Laser Hemorrhoidoplasty Using Reusable Bare Fiber Combined Mucopexy on Grade IV Internal Hemorrhoid: A Case Report

Background: Hemorrhoids are the most common anorectal disease, affecting millions worldwide. Hemorrhoids are categorized as "internal" or "external" based on their proximity to the pectinate line, which separates the upper 2/3 and lower 1/3 of the anus. The hemorrhoidal disease can be treated in various ways, from non-invasive methods like rubber band ligation, cryotherapy, sclerotherapy, laser photocoagulation, and phototherapy to invasive methods like surgical excision for patients with severe symptoms, grade III or IV hemorrhoids, or persistent bleeding. This study described the results of Laser Hemorrhoidoplasty (LHP) using reusable bare fiber combined mucopexy, a diode laser with wavelengths of 980 nm and 1470 nm, specifically gallium aluminum arsenide (GaAIAs). Methods: a case of a 28-year-old male with complaints of rectal prolapse mass one day ago and could not be reinserted with a finger, bleeding while passing stool, and rectal pain with a Visual analog scale was 7. The patient had experienced similar symptoms and had a sclerobanding procedure four years ago. However, it has reappeared in the past year. The patient was diagnosed with grade 4 internal hemorrhoids and underwent Conclusion: Laser hemorrhoidoplasty using reusable bare fiber with combined mucopexy. After the laser hemorrhoidoplasty procedure on day 4, the patient felt no pain, rectal bleeding, rectal lumps, or soiling.

1.3 μm InAs/GaAs quantum-dot lasers grown on planar on-axis Si (001) substrates with high slope-efficiency and low differential resistance

We report electrically pumped continuous-wave (CW) InAs/GaAs quantum dot lasers monolithically grown on planar on-axis Si (001) substrates. Combining an asymmetric waveguide epitaxy structure with aluminium-free upper cladding layers and a symmetrical cathode chip structure, 1.3 μm band lasers with low differential resistance and high slope-efficiency have been achieved. Moreover, the optimized symmetrical cathode structure of the laser chips is used to improve the slope-efficiency by reducing the differential resistance and waste heat. The Fabry–Perot broad-stripe edge-emitting lasers with 2000 μm cavity length and 15 μm stripe width achieve a single-facet output power of 73 mW, a single-facet slope efficiency of 0.165 W A−1, and a differential resistance of 1.31 Ω at ∼1.31 μm wavelength under CW conditions at room temperature (25 °C). Importantly, these results provide an effective strategy to achieve 1.3 μm wavelength band single-mode distributed feedback lasers directly on planar on-axis Si (001) substrates with high efficiency.

Epitaxial growth of high-quality GaAs on Si(001) using ultrathin buffer layers

The direct growth of III–V semiconductors on silicon holds tremendous potential for photonics applications. However, the inherent differences in their properties lead to defects in the epitaxial layer, including threading dislocations (TDs), antiphase boundaries (APBs), and thermal cracks, significantly impacting device performance. Current processes struggle to suppress these defects simultaneously, necessitating the development of methods to inhibit TDs and APBs in a thin buffer on silicon. This study introduces a GaSb buffer layer during GaAs epitaxy on a silicon (001) substrate. This approach successfully suppresses defect formation by promoting the formation of interfacial misfit dislocation arrays at both the AlSb/Si and GaAs/GaSb interfaces. The resulting GaAs layer exhibits a step-flow surface with a rough mean square of ∼3.8 nm and a full width at half maximum of 158 arcsec. Remarkably, the growth is achieved without any observable interfacial intermixing. Building on this platform, InAs/GaAs quantum dots are grown with a density of 3.8 × 1010 cm−2, emitting at a wavelength of 1288 nm. This breakthrough holds immense promise for developing high-quality GaAs films with reduced defect densities on silicon for O band lasers, laying the foundation for the mass production of silicon-based integrated circuits.

Influence of PEG content on optical band gap and laser damage characteristics of porous films

Influence of PEG content on optical band gap and laser damage characteristics of porous films

Lasing properties, Judd-Ofelt and band gap investigation of cool green emanating Tb3+ complexes for solid and solution state luminescence

Optical and photophysical characteristics of six green emanating terbium complexes which have been prepared by eco-efficient solvent assisted grinding process. The prepared complexes display bright green luminescence with a prominent peak at 548 nm accredited to 5D4 → 7F5 transition of terbium ions, as examined by PL emission spectra monitored at 355 nm excitation wavelength. Spectroscopic investigation of these synthesised complexes was explored. Photometric features such as CIE coordinate, CCT and %CP asserted their green luminescence and are found in agreement with brilliant green light. Lasing properties, optoelectronic and thermal analysis of terbium complexes were performed. To determine the coordination environment around the metal ion, JO parameter (Ω2, Ω4, Ω6) and intensity ratio were also determined. The research offers a glowing cool green emitting constituent for the manufacturing of OLEDs and innovative optoelectronic devices. Antioxidant and antimicrobial properties were also examined. Computational studied of complexes were carried out successfully.

Development of the 2.7 μm to 3 μm Erbium-Doped Laser

The 3 μm wavelength band laser is located on the strong absorption peak of water and the atmospheric transmission window. The 3 μm laser with high single pulse energy is used in medical treatment for cutting soft tissues and bones during surgery. It is used as a pump source for optical parametric oscillators, and Fe lasers can realize 3~5 μm or 8~14 μm laser output, which has an irreplaceable role in certain areas (e.g., optoelectronic countermeasures, LIDAR, atmospheric monitoring, etc.). Commercial semiconductor-pumped Er lasers are capable of achieving 3 μm laser output of 600 mJ with the maturation of a 970 nm semiconductor laser. The conversion efficiency is significantly improved. However, the energy is lower than a flash-lamp-pumped Er laser. There are still serious crystal thermal effects and an inefficient conversion process. In this paper, the energy-level systems of 3 μm Er-doped lasers are discussed. A summary of the current state of research on Er lasers using different matrices and the commercialization of Er-doped lasers with wavelengths ranging from 2.7 μm to 3 μm is also provided. Several technical means are given to enhance laser performance. Furthermore, the development of Er-doped solid-state lasers with wavelengths between 2.7 and 3 μm is envisaged in the near future.

Synchronous multi-wavelength mode-locked laser at 2-μm based on Mamyshev cavity

In recent years, 2-μm band lasers have developed rapidly due to their wide range of usage. It is a challenging problem to realize the synchronization of multi-wavelength multi-channel ultrashort pulses for many important applications. In this paper, a 2-μm synchronous multi-wavelength fiber laser is proposed. The laser was constructed based on cascaded Mamyshev regenerators. The multi-cascade nonlinear broadening and offset filtering can act as a saturable absorber, enabling mode locking, and resolving the issues of gain competition and synchronous output encountered in traditional multi-wavelength lasers. A stable synchronous multi-wavelength mode-locked laser was realized through numerical simulation. The laser can provide six-channel ultrashort pulses with a wavelength interval of 5 nm (the central wavelengths range from 2000 nm to 2025 nm). The peak power and duration of the output pulses are respectively 0.1–0.25 kW (intracavity peak power 0.4–1.1 kW for coupler ratio is 20:80) and ∼1.1 ps. Design principles and the effects of various parameters such as the filter, the fiber length, etc., on the optimization of the laser are analyzed and discussed.

150 Gbps multi-wavelength FSO transmission with 25-GHz ITU-T grid in the mid-infrared region.

The 3∼5 µm mid-infrared (mid-IR) light has several exceptional benefits in the case of adverse atmospheric conditions compared to the 1.5 µm band, so it is a promising candidate for optical carriers for free-space communication (FSO) through atmospheric channels. However, the transmission capacity in the mid-IR band is constrained in the lower range due to the immaturity of its devices. In this work, to replicate the 1.5 µm band dense wavelength division multiplexing (DWDM) technology to the 3 µm band for high-capacity transmission, we demonstrate a 12-channel 150 Gbps FSO transmission in the 3 µm band based on our developed mid-IR transmitter and receiver modules. These modules enable wavelength conversion between the 1.5 µm and 3 µm bands based on the effect of difference-frequency generation (DFG). The mid-IR transmitter effectively generates up to 12 optical channels ranging from 3.5768 µm to 3.5885 µm with a power of 6.6 dBm, and each channel carries 12.5 Gbps binary phase shift keying (BPSK) modulated data. The mid-IR receiver regenerates the 1.5 µm band DWDM signal with a power of -32.1 dBm. Relevant results of regenerated signal demodulation have been collected in detail, including bit error ratio (BER), constellation diagram, and eye diagram. The power penalties of the 6th to 8th channels selected from the regenerated signal are lower than 2.2 dB compared with back-to-back (BTB) DWDM signal at a bit error ratio (BER) of 1E-6, and other channels can also achieve good transmission quality. It is expected to further push the data capacity to the terabit-per-second level by adding more 1.5 µm band laser sources and using wider-bandwidth chirped nonlinear crystals.

Stand-off detection of ethanol gas in turbulent state using a 1.7 μm/1.5 μm near-infrared spectroscopy system

Considering that the stand-off detection of ethanol gas is significant for monitoring ethanol-free occasions, we propose and experimentally demonstrate a 1.7 μm/1.5 μm near-infrared spectroscopy system. Then based on the generated laser signals and the system, the ethanol gas and ethanol solution was stand-off detected and researched. Firstly, we measured the absorption characteristics of ethanol solution in the near-infrared band for wavelength selection. Secondly, the Tm-doped fiber laser in the system was achieved based on a ring cavity and a customized FBG; its output laser wavelength was 1728.45 nm. The linewidth of the 1.7 μm band signal was about 0.18 nm and the side mode suppression ratio (SMSR) was about 57 dB. Thirdly, ethanol gas and ethanol solution were stand-offs detected using the established 1.7 μm/1.5 μm near-infrared spectroscopy system. The concentration of ethanol solution was measured by 1.7 μm band laser, and the R-Square of the linear fit was 0.98. However, the concentration of ethanol gas in a turbulence state cannot be easily measured due to scintillation. Therefore, we detected the ethanol gas a turbulence state using a 1.7 μm/1.5 μm dual-band system, R-Square of the linear fit was 0.83 when the power jitter variance was 2.35. the experimental results offer a technical reference for stand-off detection of ethanol gas.

Atomically Precise Ni Nanoclusters for Improving Hydrogen Evolution Reaction Performance

The generation of green hydrogen via electrocatalytic water splitting is an emerging strategy in the prospect of developing future energy devices. Herein, we designed water-soluble atomically precise Ni nanoclusters (NCs) on MoSe2 nanosheets (NSs) to enhance the hydrogen evolution reaction (HER) performance. The strong UV–vis absorption band and matrix-assisted laser deposition ionization (MALDI) time-of-flight mass spectra confirm the formation of Ni7 NCs. The energy-dispersive X-ray spectroscopy mapping confirms the homogeneous distribution of Ni, Mo, and Se throughout the surface of the ultrathin NS. X-ray photoelectron spectroscopy study reveals the strong interfacial interaction between Ni NCs and MoSe2 in the nanocomposite by substantial electron density transferring from Ni NCs to the MoSe2 NSs. It is seen that the 5 wt % Ni/MoSe2 composite structure exhibits the most notable HER efficiency with an overpotential of 170 mV vs reversible hydrogen electrode @ 10 mA/cm2 which is significantly lower than that of bare MoSe2 NSs (350 mV). The significantly lower Tafel slope of the Ni/MoSe2 nanocomposite indicates that the HER kinetics of MoSe2 is accelerated in the presence of Ni NCs. The charge-transfer resistance of the nanocomposite is significantly low compared to pristine MoSe2, confirming the enhanced interfacial charge transfer. This work opens up further opportunities to design efficient and low-cost electrocatalysts for improving the HER performance by incorporating the advantages of both non-precious atomically precise metal NCs and transition-metal dichalcogenides in one system.

One- and two-photon lasing from a TCF-based AIE dye

The aggregation of a TCF-based dye exhibiting AIE is used to enhance the random lasing emission intensity up to 170 times. The transition from small aggregates to crystals forms a second lasing band and is responsible for 2-photon pumped lasing.

Intra-Cavity Raman Laser Operating at 1193 nm Based on Graded-Index Fiber

Nonlinear Raman frequency conversion is an important technical scheme to obtain special optical band lasers based on conventional ion-doped lasers. In our work, we designed an intra-cavity Raman fiber laser based on graded index fiber (GRIF) as the Raman gain medium. Based on the fundamental-frequency 1080-nanometer laser, efficient first-order and second-order Stokes Raman lasers were obtained, respectively. When the power of the fundamental-frequency 1080-nanometer laser was 33.4 W, the output power of the second-order 1193-nanometer laser was 11.39 W. The corresponding conversion efficiency was 34.1%. To our knowledge, this is the first report of a second-order Raman output based on a GRIF and intra-cavity structure. In the experiment, the spectrum-purification process with the increase in power was also observed. Our experimental results prove that the intracavity Raman-laser system based on graded index fiber with a high optical conversion efficiency has important application potential for obtaining new special-application bands.

Demonstration of ultraviolet-B AlGaN-based laser diode operation with a peak light output power of 150 mW by improving injection efficiency through polarization charge modulation

In this study, AlGaN-based ultraviolet-B band laser diodes with 150-mW peak output power in pulsed operation were demonstrated at room temperature. The oscillation wavelength, differential quantum efficiency, and slope efficiency of a laser diode were 300 nm, 3.6%, and 0.15 W/A, respectively. These results were obtained by increasing the injection efficiency and decreasing the positive fixed polarization charge formed at the interface between a p-side waveguide layer and an electron blocking layer when polarization doping is formed in a p-AlGaN cladding layer.

10-Watt-Level 1.7 μm Random Fiber Laser with Super-High Spectral Purity in a Cost-Effective and Robust Structure

The 1.7 μm band eye-safe laser sources have recently received lots of attention thanks to the development of various applications. Although a variety of lasing configurations operating in this band have been demonstrated, one still needs to seek a good candidate for particular applications with a reasonable compromise between the relative performance targets (e.g., stability, output power, and spectral purity) and the construction cost. Here, we demonstrate a high-power 1694 nm random fiber laser (RFL) in a cost-effective structure pumped by a high-powered 1565 nm RFL. The maximum output power reached the 10 W level, and the output showed extremely low-intensity fluctuations for both the short-time and long-time regimes. Meanwhile, an excellent spectral purity as high as 26.9 dB was also realized. This work provides one of the most attractive approaches for constructing high-performance 1.7 μm band laser sources for practical applications.

Outcomes of Rubber Band Ligation in Haemorrhoids Among Outdoor Patients.

Out of all anorectal diseases, haemorrhoids are the most common benign disease. Haemorrhoids can be treated by various treatment modalities like medical, surgical, and instrumental. Instrumental treatment comprises rubber band ligation, sclerotherapy, and infrared and laser therapy. Out of these modalities, the rubber band ligation technique is the least invasive with a reduced rate of complications and without the need for hospitalization. Hence, the current study was conducted to evaluate the outcomes with respect to the effectiveness of rubber band ligation in grade II and III internal haemorrhoids along with the magnitude and pattern of post-procedural complications. This is a prospective observational study, conducted on a sample of 100 patients who presented to our outdoor patient's department and were diagnosed with haemorrhoids, either grade II or III. All enrolled study patients having haemorrhoids were banded with rubber band by Barron Ligator (Precise, Canada) with local anaesthetic agent xylocaine jelly in a single session. All patients were followed on the 10th day, 1st month, and 6th month after the procedure to assess symptomatic improvement. The endpoint of this study is to know the effectiveness of rubber band ligation in different clinical parameters such as post-ligation pain or discomfort, the requirement of analgesic, any complication, and time off work. Out of 100 patients 17 patients had grade II and 83 patients had grade III haemorrhoids. Among them, 89% were symptomatically relieved after rubber band ligation whereas the rest 11% of patients had residual symptoms. Thus, we conclude that rubber band ligation for grade II and III haemorrhoids is simple, safer, easy-to-perform daycare procedure with lesser requirements of analgesics and without any need for anaesthesia.

Structure and Luminescence Properties of Ho:(Y1−xScx)2O3 Ceramics

Ho‐doped sesquioxide is one of the most important laser gain media for 2 micron wavelength band laser applications. It is hard to be transparent by sintering because of its high melting point. Herein, the structural and spectral properties of 0.5 at% Ho:(Y1−xScx)2O3 (x = 0, 0.3, 0.5, 0.7, 1.0) ceramics fabricated by vacuum pressureless sintering are studied. Then, 0.5 at% Ho:(Y0.7Sc0.3)2O3 transparent ceramics with 1.0 at% ZrO2 as a sintering aid are prepared by vacuum pressureless presintering (1680 °C for 4 h) combined with hot isostatic pressing sintering treatment (1600 °C/190 MPa for 3 h). The transmittance of Ho:(Y0.7Sc0.3)2O3 ceramic reaches 80.8% at 1100 nm (6 mm in thickness), which is close to its theoretic value. The addition of ZrO2 has no significant influence on spectroscopic properties of 0.5 at% Ho:(Y0.7Sc0.3)2O3 ceramics.

(Digital Presentation) Monitoring and Controlling Tautomerization in Phthalocyanines, Porphyrines and Porphycenes By Optical Single-Molecule Imaging and Spectroscopy

Tautomerization is an intramolecular chemical reaction defined as structural interconversion of a molecule between two isomers separated by a low energy barrier. Tautomerization in free base phthalocyanines, porphyrins or porphycenes has fascinated and attracted chemists and physicists alike over the last decades for its fundamental importance in various chemical and biological systems and many applications in technology [1,2]. Particularly interesting is the reaction rate which can range over orders of magnitude depending on the temperature and the local environment. In solution, this reaction in porphycenes occurs usually in several picoseconds or even faster, as determined via anisotropy studies by ultrafast transient absorption spectroscopy [3] and in porphyrins at cryogenic temperatures it can last for hours or days as determined form the live time of narrow spectral holes photochemically burned in the inhomogeneously broadened absorption band with a narrow band laser [4]. However, a spectacular and unexpected observation has been made by optical single molecule imaging and spectroscopy [5]. Examining a large number of single molecules embedded at low concentration in various polymer matrices at room temperature has revealed unquestionably that the rate in these molecules can vary dramatically over time such that tautomerization can be frozen for seconds and longer under ambient conditions[6]. The interconversion of the inner protons of phthalocyanine changes the orientation of the transition dipole moment by 90o degrees with respect to the molecular structure. Hence, if these molecules are embedded with a fixed orientation in a transparent solid polymer film at high dilution and tautomerization is frozen, the orientation of their transition dipole moments can be determined by polarization spectroscopy.Here we report on our recent experimental and theoretical studies of monitoring tautomerization by fluorescence imaging of single molecules of phthalocyanines, porphyrins, or porphycenes excited in the tightly focused azimuthally and radially polarized laser beam with a sample scanning confocal optical microscope equipped with single photon counting electronics and a fluorescence spectrometer. This technique has been used to determine the transition dipole moment orientation of single molecules, the polarizability of plasmonic nanoparticles or the dimensionality of single quantum dots. Different diffraction limited fluorescence intensity patterns are observed for molecules that undergo tautomerization and for those that do not. The latter corresponds to a molecule with a fixed transition dipole moment direction, whereas the tautomerizing molecule can be treated as the superposition of two emitters with different transition dipole moment orientations.Previous studies have shown that tautomerization in porphyrins or phthalocyanines can occur via ground state tunneling and is frozen at low temperatures, particularly at cryogenic temperatures. The structural heterogeneity in a polymer matrix leads to a distribution of asymmetrically distorted ground state double well potential and hence can lead to long residence times in the deeper energy minimum. However, even at helium temperatures tautomerization can be induced by electronic excitation to the first excited state, making photochemical spectral hole-burning possible. Recently we could demonstrate in a single-molecule study that the tautomerization rate of phthalocyanine tetrasulfonate embedded in a thin PVA-film at room temperature could be controlled in a tunable λ/2 Fabry Perot resonator by weak coupling between the electronically excited state and the vacuum electromagnetic field of a resonant cavity mode.