Mitrofanov, A., VSidorov-Biryukov, D. A.Voronin, A. A.Nazarov, M. M....
7页
查看更多>>摘要：ABSTR A C T We demonstrate a multicompartment, power-scalable beam-line design in which sub-40-fs, terawatt field waveforms are tailored in space and time for downstream pulse compression to few-cycle pulse widths attained right at the site where the intense laser field interacts with a target. An accurate field-waveform characterization performed at multiple locations along the beam path shows that, despite all the complexity of their upstream nonlinear electrodynamics, field waveforms shorter than three field cycles can be delivered to a laser-matter interaction site in such a system, enabling a vast class of ultrafast strong-field laser-matter interaction studies.
查看更多>>摘要：Amplification of single channel and three Wavelength division multiplexing (WDM) channels with 16 and 64QAM modulated signals is demonstrated using an SOA with holding beam in the non-transparency wavelength to minimize phase distortion. We demonstrate an optical gain of 10 dB for single channel and for each channel in WDM operation. We also show that, the performance with holding beam can provide with minimal phase distortions a better bit-error rate value when compared to the linear regime of SOA operation for the same output power level.
查看更多>>摘要：We propose a method for designing the multilayer diffractive optical elements (MLDOEs) to improve the polychromatic integral diffraction efficiency (PIDE) in wide angle of incidence. By comparing and analyzing the characteristic angle weighted PIDE (CAW-PIDE) in the whole angles of incidence, the optimal microstructure height combination of the MLDOE can be obtained. The optimization process and simulation examples for the single-band and multi-band MLDOE are given. Compared to the conventional method, the PIDE is obviously improved in wide angle of incidence by our method. This optimization method can be applied to different working wavebands, and the image quality of the hybrid optical system with the MLDOE can be improved in wide angle of incidence.
Ahmed, NorizanOmar, SuzianaZulkipli, Nur FarhanahJusoh, Zulzilawati...
6页
查看更多>>摘要：In this paper, a new saturable absorber (SA) based on Lanthanum Hexaboride (LaB6) is used to produce Q -switched and mode-locked laser pulses. In constructing the SA, the prepared LaB6 powder is dispersed in polyvinyl alcohol (PVA) solution before the mixture is dried to form a thin film. A small piece of the film is placed between two fiber ferrules to form a LaB6 PVA SA and added to a laser cavity of an erbium-doped fiber laser (EDFL) to produce Q-switched and mode-locked pulses. The Q-switched laser operates at 1531 nm. The pulse width of the pulses can be varied between 4.32 to 2.46 ps with a corresponding repetition rate of 62.0 to 89.6 kHz when the pump power is increased from 45.4 to 97.6 mW. At the maximum output power of 4.31 mW, the highest pulse energy of 48.1 nJ was obtained. A passively mode locked EDFL was also successfully realized with LaB6 SA by adding 100 m long single mode fiber inside the cavity. A stable mode-locked laser operating at 1559.1 nm was achieved at the threshold pump power of 102.8 mW with a pulse rate of 1.88 MHz. The pulse energy of 5.6 nJ and output power of 10.54 mW were obtained at a maximum pump power of 144.6 mW. To the best of our knowledge, this is the first demonstration of utilizing LaB6 material as SA to produce pulses in the 1.5 pm region.
查看更多>>摘要：Speckle modulation in the laser beam projection scenarios such as adaptive optics, remote sensing, and active imaging has been a long-standing challenge that causes intensity fluctuation and further degrades the performance of the system. Speckle statistical characteristics coupled with the feature of the laser beam intensity distribution can be obtained by analyzing the speckle variation through a single point detector or an image sensor. A single point detector has the advantage in high sampling rate but may lose speckle spatial information, while the image sensor has a high spatial resolution but slow sampling rate. In this paper, we defined a dynamic speckle metric based on a linear array detector to estimate the encircled energy of the far field spot on the diffuse target, which well balanced the trade-off between sampling rate and spatial resolution. The potential of the metric is analyzed using a physics-based speckle simulation and experimental verification. Both results agree with each other, showing that the metrics based on the speckle-field spatiotemporal spectrum analysis are monotonically dependent on the target focused-spot size.
查看更多>>摘要：A volume Bragg grating-based external cavity diode laser array produced more than 100 W output power for metastable argon atoms pumping centered at 811.53 nm with a 0.15 nm spectral linewidth (FWHM). The device has only 4.6 % loss compared to the free-running case operating at full power and a spectral contrast of 40 dB. The emission spectrum can be precisely tuned to 811.53 nm and has an over 200 pm tuning range. Pump absorption was demonstrated by using a repetitively pulsed glow discharge operating with 620 Torr Ar/He mixture, and an average absorption of 24 % of the pump radiation was realized.
查看更多>>摘要：ABSTR A C T A novel diffusion double-ended bonded structure (DEBS) consisting of F2 glass, Er3+/Yb3+: glass and Co2+:MgAl2O4 was reported, for human eye-safety micro-ranging lasers. Compared with single-ended bonding structure (SEBS) and single glass structure (SGS) by the thermal analysis, its thermal focal length increased by 53.8% over the latter two. It was noted that the DEBS could effectively reduce the thermal effect of the gain medium. Under the identical experimental conditions, the DEBS's laser performance characteristics were significantly better than the other two. The peak power and laser stability of the DEBS could be dramatically improved more 45.4% and 100%, respectively. Finally, the DEBS laser delivered 340 mu J pulse energy with 10 Hz repetition rate, 5.5 ns pulse duration and 1.4 of beam quality factors M-2. Such an eye-safe compact laser can be applied in ranging systems, such as drones and low-altitude missiles.
查看更多>>摘要：Based on the Huygens-Fresnel integral and second-order intensity moments, analytical expressions for paraxial propagation, and the beam propagation factor (M-2) of a circular cosine hyperbolic-Gaussian beam (CiChGB) have been derived. The propagation properties of a CiChGB in free-space including the beam width and M-2 factor, and the beam focusing by a thin lens are numerically demonstrated. It is found that the profile of the beam at the initial plane and its propagation characteristics are closely related to its decentered parameter b. The focal shift and M-2 factor of a CiChGB are shown to be smaller when the parameter b is larger. The obtained results could be beneficial for applications of CiChGBs in beam shaping, optical trapping.
查看更多>>摘要：A transmitted optical fiber sensing system based on orthogonal demodulation algorithm is used for hydrogen detection in this paper. WO3/Pt fabricated by sol-gel method was used as sensing material. WO3 film reacts with hydrogen by the catalysis of Pt and refractive index of the sensing film changed, by measuring the transmitted optical power the concentration of hydrogen can be detected. Orthogonal demodulation algorithm was used to demodulate the weak transmitted optical intensity signals. Compared with the traditional ratiotype transmitted optical fiber hydrogen sensing system, the noise reduced by 28 times. The limit of detection is 495ppm and with good repeatability and stability. In order to improve the sensitivity of the system, three pieces of sensing film were used to increase the interaction length of the sensing material with hydrogen and the sensitivity increased by 2.592 times. With the orthogonal demodulated technique and multi pieces of sensing film, high sensitivity, fast response and low cost hydrogen sensing system was implemented and is very promising for the monitoring of hydrogen leakage in the field of hydrogen production, transportation, and storage.
查看更多>>摘要：A method for the generation of tunable multi-degree-of-freedom rotations of vector beams on demand along a propagation direction is theoretically proposed. This generation can be achieved by a suitable vector superposition of three monochromatic non-coplanar beams, including a plane wave with elliptical polarization and two Bessel-Hermite-Gauss (BHG) beams with orthogonal polarization, the parameters of which were systematically chosen to obtain the different longitudinal characteristics of the field, i.e., the state of polarization (SoP), phase, and intensity. On one hand, both the incidence angles of the two BHG beams and the additional phase of the plane wave affect the rotation of the beam intensity and phase, but the incidence angle does not affect the rotation of the SoP. Moreover, the additional phase can lead to a change of the rotation angle of the SoP. On the other hand, the weight coefficients of the two BHG beams periodically change the beam intensity distribution along the propagation direction. Interestingly, the beam is non-diffracting, which means that energy is only exchanged internally and is conserved as a whole. This approach may find applications in dynamic multi-beam optical tweezers, atom guiding, materials processing, microscopy, and optical communications.
NSTL
Elsevier