JournalTOCs

Applied Physics B: Lasers and Optics
Journal Prestige (SJR): 0.74

Citation Impact (citeScore): 2
Number of Followers: 34

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0946-2171 - ISSN (Online) 1432-0649
Published by Springer-Verlag

[2467 journals]

Investigation of compression grating misalignment in ultra-high peak power
femtosecond laser systems
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  Abstract: Abstract The misalignment of the gratings in pulse compressor can introduce residual angular chirp and finally result in a reduction of focused intensity, especially for high peak power femtosecond laser systems with large beam size and broadband spectrum. In this work, we study the angular chirp produced by grating misalignment in different dimensions and comprehensively investigate the various effects on the deterioration of the spatiotemporal characteristics of focused beam. Moreover, two representative ultra-high peak power femtosecond laser systems, featuring with 10 PW peak power/500 mm beam diameter/100 nm spectral width and 50 PW peak power/640 mm beam diameter/200 nm spectral width, are studied. For a drop of effective focused intensity smaller than 10%, the numerical results show that the misalignment of gratings must be kept below ~ 2 μrad and ~ 1 μrad for aforesaid 10 PW and 50 PW lasers, respectively. This work provides meaningful guidelines for the design and construction of the grating compressors in ultra-high peak power femtosecond laser systems.
  PubDate: 2023-03-21
Holographic ultraviolet nanosecond laser processing using adaptive optics
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  Abstract: Abstract Fabrication of a through hole in a polyimide film (PI) was demonstrated by holographic ultraviolet (UV) nanosecond laser processing with a computer-generated hologram displayed on a phase-only spatial light modulator (SLM). The UV laser was directly modulated into a Bessel beam by a diffractive axicon displayed on the SLM. The direct modulation contributed to improved light-utilization efficiency of the UV laser and a simplified optical setup compared to the conventional method based on a combination of an SLM and harmonic generation using a nonlinear optical crystal. The Bessel beam reduced the number of pulse shots required for through-hole fabrication to 1/5 compared to the Gaussian beam near the ablation threshold energy of the PI film. Furthermore, adaptive optics was implemented in holographic laser processing to compensate for aberrations in the optical setup. The aberration was reduced to 1/5 compared with before the compensation. The proposed method is suitable for improving the throughput and accuracy of drilling, cutting, and additive manufacturing using UV lasers with industrial requirements.
  PubDate: 2023-03-18
Optical pressure sensing at MHz rates via collisional line broadening of
carbon monoxide: uncertainty quantification in reacting flows
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  Abstract: Abstract An optical method for high-speed line-of-sight pressure measurements using infrared laser absorption spectroscopy is presented with detailed uncertainty analysis related to thermodynamic and compositional variation in combustion environments. The technique exploits simultaneous sub-microsecond sensing of temperature and mole fraction to extract pressure from collisional line broadening at MHz rates. A distributed-feedback quantum-cascade laser near 5 \(\upmu \) m in a bias-tee circuit is used to spectrally resolve multiple rovibrational transitions in the P-branch of the fundamental band of carbon monoxide, which may be seeded or nascent to reacting flows. A comprehensive approach for estimating collisional line broadening in complex combustion gas mixtures is presented. Uncertainty is quantified for a wide range of conditions, reflecting different fuels, equivalence ratios, reaction progress, and combustion modes (deflagration and detonation), which influence gas composition and temperature. The sensor was evaluated for accuracy and precision in both a high-enthalpy shock-tube facility in hydrocarbon–air ignition experiments and behind ethylene–oxygen detonation waves in a detonation-impulse tube facility at temperatures from 1500 to 3000 K and pressures from 0.5 to 10 bar. Pressure measurements were compared to measurements by piezoelectric pressure transducers and to theoretical estimates from normal-shock and Chapman-Jouguet simulations. The high-speed path-integrated optical pressure measurement offers an alternative to traditional electromechanical transducers that are constrained to values at wall boundaries and have proven unreliable in some harsh reacting flows.
  PubDate: 2023-03-17
Clusters of rotating beams with autofocusing and transformation properties
generated by a spatial light modulator
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  Abstract: Abstract We theoretically, numerically, and experimentally investigate new types of laser beams with autofocusing, rotating and/or transformation properties. A spatial light modulator generates these laser beams as clusters/sets of shifted vortex Laguerre-Gaussian beams and their superpositions with additional phase distribution. We demonstrate the formation of the clusters of rotating beams with controlled individual autofocusing trajectories as well as different transformations (topological/positional and interference redistribution) and rotation of the entire clusters as complex structures. Moreover, we investigate the possibility of astigmatic transformation of the propagating laser beams clusters. Thus, the proposed techniques provide additional control of the three-dimensional trajectories of the structured laser beams with predetermined intensity and phase distributions and can be used in laser manipulation, laser material processing, and optical microscopy.
  PubDate: 2023-03-13
Radiation of a plasma generated by laser pulse on CO2, CHF3, and CF4
gas-jet targets in the “water transparency window” 2.3–4.4 nm
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  Abstract: Abstract The paper considers the emission spectra and dependences of the emission intensity of a number of carbon lines in absolute units for laser plasma generated by laser pulse on CO2, CHF3, and CF4 gas jets on the gas pressure at the nozzle inlet. A pulsed Nd:YAG laser, λ = 1064 nm, τ = 5.2 ns, Eimp = 0.8 J was used. Gas-jet targets were formed by a supersonic conical nozzle, the pressure at the nozzle inlet varied in the range of 5–25 bar. The emission spectra of the investigated gases were compared and the reasons for the different dependences of the radiation intensity on the gas pressure at the nozzle inlet were analyzed.
  PubDate: 2023-03-07
Study of short-wavelength red semiconductor laser using high Ga
composition GaInP quantum well based on Ge/SiGe substrate
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  Abstract: Abstract To meet the increasing demand of short-wavelength red lasers for laser display technology and medical applications, we propose a new short-wavelength red semiconductor laser structure. The laser uses Ge/SiGe as the substrate and GaInP, AlInP and other group III-V materials as the main structural layers. The composition of Ge is adjusted to change the lattice constant of the SiGe layer according to the needs of GaInP strain quantum well design to achieve a short-wavelength red laser. A semiconductor laser with a wavelength of 620 nm is used as an example, and the effect of both the interfacial state and the GaInP-strained quantum well on the device characteristics is discussed through simulation. It is found that the laser structure has the optimal output characteristics when the quantum well is subjected to 0.32% compressive strain under the conditions of the interfacial state, which indicates the feasibility of this laser structure design scheme.
  PubDate: 2023-03-03
Power-scaled CW Alexandrite lasers
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  Abstract: Abstract We present several strategies for increasing the output laser power of near-diffraction limited continuous-wave Alexandrite lasers pumped by fibre-coupled red laser diodes. Laser mode size control using a convex mirror with the varying thermal lens is shown to be an efficient method for generating record levels of output power from a diode-pumped Alexandrite laser. 8.6 W is obtained with \(M^{2}<1.1\) and an optical efficiency of 27%. 735–790 nm wavelength tuning is demonstrated with \(> {2.5}\,\hbox {W}\) and a record dual-wavelength output power of 4.2 W. In a ring-cavity geometry, 5.1 W is obtained with \(M^{2}<1.1\) showing promising potential for multi-watt single-longitudinal-mode operation. Detailed laser cavity modelling including thermal lens analysis is also provided.
  PubDate: 2023-03-01
Analogy of harmonic modelocked pulses to trapped Brownian particles
improves laser performance
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  Abstract: Abstract High-repetition-rate ultrafast lasers are needed for diverse applications. Harmonic modelocking, where multiple identical, equidistant pulses circulate in the cavity, reaches beyond the practical limitations of reducing the cavity length. However, it suffers from stochastic deviations that manifest as supermodes in the radio-frequency spectrum and difficulties in maintaining the same harmonic state, often coupled with trade-offs in pulse energy, duration, or noise performance. Here, we first show that deviations in the temporal positions of the pulses contribute disproportionately more to the supermodes than deviations in their amplitudes. Then, we argue that these fluctuations are analogous to those of trapped Brownian particles. This analogy reveals that supermodes are suppressed by stronger spectral filtering, which corresponds to fluid viscosity, and higher pulse energy reduces the noise, akin to lower temperature. Guided by this intuitive picture, we construct a Yb-fibre laser incorporating strong filtering and high intracavity energies by limiting nonlinear polarisation evolution to a short section of ordinary fibre. The rest of the all-fibre cavity comprises polarisation-maintaining fibre, which additionally improves environmental robustness. We report record-high supermode suppression ratios, reaching 80 dB, excellent long-term and environmental stability, and pulse energy, duration, and noise characteristics that are similar to fundamentally modelocked lasers.
  PubDate: 2023-02-28
Experimentally simulating the beam shaping capabilities of piston-type
deformable mirrors using a liquid crystal spatial light modulator
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  Abstract: Abstract The number of mirror segments, mirror geometry and orientation are essential parameters when assessing the beam-shaping capabilities of deformable mirrors. Here, we use a Liquid Crystal on Silicon Spatial Light Modulator (LCoS-SLM) to mimic the mechanical design of a deformable mirror and quantitatively analyse the effect of the number of mirror segments and their geometrical structure on resulting structured modes. Our approach can be used as a test bed prior to designing a deformable mirror for high power beam shaping.
  PubDate: 2023-02-28
High-performance graphene–PbS quantum dots hybrid photodetector with
broadband response and long-time stability
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  Abstract: Abstract In this work, a graphene photodetector hybrid with lead sulfide quantum dots (PbS QDs) is introduced, aiming to take both the advantages of broad-spectrum absorption of PbS QDs and ultrafast carrier mobility of graphene. Through coating the PbS QDs on the graphene, a hybrid photodetector was successfully fabricated, and the optical response of this device to the photo illumination was observed from 405 to 980 nm. The experimental results show that the photoresponsivity of the hybrid photodetector is 7.7 × 102 A·W−1, 6.4 × 102 A·W−1, 5.4 × 102 A·W−1 and 2 × 102 A·W−1 under 0.16 mW/cm2 laser illumination of 405 nm, 515 nm, 650 nm and 980 nm, respectively. The maximum photoresponsivity of this device is 7.7 × 102 A·W−1 (8.93 × 109 Jones). The photoconductive gain is 3 × 107. Moreover, the device can maintain steady photoresponse for more than 250 s and 25 on/off switching cycles at least. It is believed that such a device fabricated by controllable graphene film and PbS QDs with long-time photoresponse stability in broadband spectrum will stimulate the development of novel graphene photodetectors.
  PubDate: 2023-02-22
Conjugate symmetric extension Fourier computer-generated holography with
controllable reconstruction focus
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  Abstract: Abstract A conjugate symmetric extension Fourier computer-generated holography algorithm with controllable reconstruction focus is proposed. The real function can be directly generated by the inverse Fourier transform of the target object after conjugating symmetric extension. Subsequently, it is mapped to 0–2π linearly and superimposed with a quadratic phase term that carries the reconstruction focus to obtain a phase-only hologram that contains the amplitude, phase and reconstruction focus information of the target object. Numerical reconstruction and optical reconstruction results show that the target object can have a good reconstruction effect at a given distance. The algorithm contains only one inverse Fourier transform, which improves the efficiency of holographic coding significantly and can be used for a real-time 3D holographic display.
  PubDate: 2023-02-22
Experimental X-ray emission doses from GHz repetitive burst laser
irradiation at 100 kHz repetition rate
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  Abstract: Abstract Material processing with high repetition rate ultra-short laser pulses with intensities higher than 10 \(^{13}\) W/cm \(^{2}\) may lead to the X-ray emission dose exceeding allowed dose limits. We have investigated a worse-case exposure scenario, in which laser processing parameters were tuned to maximize X-ray yield. Use of double pulse regime leads to increase of the X-ray yield up to two orders of magnitude compared with the single pulse regime. \(H^{\prime }\) (0.07) and H*(10) dose rates were measured using X-ray spectrometer and electronic dosimeter. Maximum dose rates at 35 cm distance from the X-ray source calculated using spectrometer data exceeded 1 Sv/h and 9 mSv/h, respectively. Dose rates measured using the dosimeter were lower. The difference is attributed to narrower X-ray spectral range detectable by dosimeters, which may lead to underestimation of exposure doses in the laser processing laboratories. The presented method might be used as an example to evaluate X-ray yield and optimize measures of radiation protection.
  PubDate: 2023-02-16
Cryogenic Tm:LiYF4 laser around 2 µm
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  Abstract: Abstract We present the laser characteristics of a 5 at.% Tm:YLF crystal using a modular setup at cryogenic temperatures emitting around 2 µm. Continuous-wave laser operation was achieved by pumping the laser crystal using a Volume Bragg Grating-stabilized laser diode emitting at 793 nm. A maximum output power of 6.5 W was achieved at 80 K corresponding to a slope efficiency of 66.0% with respect to the absorbed power with excellent beam quality.
  PubDate: 2023-02-15
Femtosecond tunable-wavelength photoassisted cold field emission
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  Abstract: Abstract We demonstrate photoassisted cold field emission (PFE) from a tungsten tip induced by tunable-wavelength low-power femtosecond laser excitation. The emission current from the apex of the (310)-oriented single-crystalline emitter is shown to linearly depend on the incident laser power, while the effective work function is reduced by the respective photon energy. Our results promote the implementation of the linear regime in laser-triggered cold field emission for ultrafast transmission electron microscopy.
  PubDate: 2023-02-15
Electro-optic tunable grating-assisted optical waveguide directional
coupler in lithium niobate
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  Abstract: Abstract In this paper, a high-performance electro-optical tunable grating-assisted directional coupler (GADC) is proposed and demonstrated experimentally. Our proposed GADC consists of a two-mode waveguide (TMW) and a single-mode waveguide (SMW) formed with lithium niobate (LN). By introducing a long-period waveguide grating into the side-wall of the TMW to compensate for the phase mismatch of the fundamental modes of the SMW and TMW, the fundamental modes of the two waveguides can be coupled efficiently each other at a specific wavelength. Furthermore, push–pull electrode structure is introduced to achieve the electro-optic (EO) tuning function featuring high speed, low driving voltage, and large tuning range. The best LN GADC we fabricated on x-cut LN substrate using annealing proton exchange process shows a high isolation of ~ 34 dB at 1532.9 nm wavelength, quite large EO tuning efficiency of 1.195 nm/V (1526.4–1549.1 nm) or 1.736 nm/V (1576.1–1602.2 nm), and a thermo-optic tuning efficiency of 0.128 nm/°C (22–60 °C). Our proposed LN GADC can find applications in the fields of high-speed tunable wavelength filtering, mode filtering, and EO modulation.
  PubDate: 2023-02-13
Optical tweezers based on nonlinear focusing
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  Abstract: Abstract Recently, some authors have proposed to add an optical Kerr effect (OKE) while focusing the Gaussian beam (GB) enlightening an optical trap. These authors conclude that the introduction of a nonlinear lensing (NL) is benefit to the optical trapping capacity. The proposed modelling was based on the Gaussian approximation (GA) which assimilates the Kerr lensing effect to a pure lensing effect free from any aberration. In this paper, we evaluate the longitudinal and radial figures of merit of the optical trap based on NL using a diffraction integral taking into account the aberration associated with the OKE. The conclusion is that the GA modelling underestimates (overestimates) the improving of the longitudinal (radial) trapping ability of the optical trap. In summary, what is gained in the longitudinal efficiency of the nonlinear trap is lost in the radial force which decreases, thereby reducing the possibility to keep trapped the particle.
  PubDate: 2023-02-10
Heating rate measurement and characterization of a prototype
surface-electrode trap for optical frequency metrology
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  Abstract: Abstract We present the characterization of a prototype surface-electrode trap as a first step towards the realization of a compact, single-ion optical clock based on Yb \(^+\) . The use of a SE trap will be a key factor to benefit from clean-room fabrication techniques and technological advances made in the field of quantum information processing. We successfully demonstrated trapping at a 500 \({\upmu }\) m electrodes distance and characterized our trap in terms of lifetime and heating rate. This is to our knowledge the highest distance achieved for heating rates measurements in SE traps. This simple 5-wire design realized with simple materials yields a heating rate of \(8\times 10^3\) phonons/s. We provide an analysis of the performances of this prototype trap for optical frequency metrology.
  PubDate: 2023-02-07
Wind retrieval for genetic algorithm-based coherent Doppler wind lidar
employing airborne platform
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  Abstract: Abstract The method of the maximum function of accumulated spectra based on the genetic algorithm is applied for the first time to three-dimensional (3D) wind field retrieval by Doppler wind lidar on an airborne platform. The algorithm can obtain the 3D wind field directly from the origin spectra of different directions regardless of the radial wind velocity inversion accuracy. To validate the reliability of this algorithm for application on an airborne platform, a 1.54-μm all-fiber airborne pulsed coherent Doppler lidar was installed on an aircraft to conduct field experiments. The measured wind fields were compared with those obtained through the sounding balloon and the ground-based lidar. For the sounding balloon, the average errors of wind speed and the wind direction are 0.539 m/s and 5.12°; while for the ground-based lidar, the average errors are 0.504 m/s and 4.18°, respectively. In addition, the two inversion results are in good consistency by comparison with the least square method. The genetic algorithm shows higher accuracy even though the detectability is low. The proposed algorithm, as an efficient and accurate calculation model, would be a good tool in the airborne platform for wind retrieval.
  PubDate: 2023-02-05
High-performance all-optical 3 × 8 photonic crystal decoder using
nonlinear micro-ring resonators
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  Abstract: Abstract In this paper, we proposed that a 3 × 8 all-optical decoder operates around 1.55 µm. We combined a 3-input port mixer (A1, A2, and A3) with an excitation port (E) and an 8-output port switch to create the proposed structure. The mixer is a square array of GaAs dielectric rods with a refractive index of 3.37. The switch is a square network of GaAs with a linear refractive index equal to 3.37 and a nonlinear Kerr coefficient equal to 1.6 × 10–17 m2/w. We controlled the switch’s optical behavior via the applied optical power intensity. The switch insertion loss values are between − 0.043 and − 0.6 dB, and the maximum cross talk is between − 7.96 and − 14.62 dB. The intensity applied to the combiner input ports is 600 w/m2. In order to activate the decoder, we excited it to a power of 100 w/m2. To perform the necessary simulations, we used the finite-element method implemented in COMSOL Multiphysics software. The proposed structure works completely in the optical domain without any electronics.
  PubDate: 2023-02-04
Design of ZnO/Ag dimer/porous silicon sandwich structures and theoretical
investigation on its fluorescence emission mechanism
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  Abstract: Abstract Based on ZnO, Ag nanoparticles (NPs) and porous silicon (PS), ZnO/Ag/PS sandwich structures with different Ag nanostructures including Ag NP array, Ag NP dimer array, Ag cone array, and Ag cone dimer array are constructed using wave optics module of Comsol Multiphysics. Under S-polarization and P-polarization, the effect of different Ag nanostructures on electric field distribution, absorption, and fluorescence emission of the sandwich structures is investigated. Results indicate that compared with the sandwich structures with Ag NP array, the fluorescence emission of that with Ag NP dimer array is greatly enhanced. The fluorescence intensity under S-polarization is different from that under P-polarization, but the peak positions are same. Finally, the electron transport mechanism in the sandwich structures is proposed. We discuss the electron transfer, the resonance peak positions of different Ag nanostructures and the overlapping area between ZnO and Ag to further confirm the fluorescence emission mechanism. It provides a new design idea for highly efficient optoelectronic devices.
  PubDate: 2023-02-02