Design and Analysis of Highly Efficient Reflective 1x3 Splitting Grating with Triangular Structure

A highly efficient reflective 1x3 splitting grating with triangular structure operating in 1.064 mu m wavelength under normal incidence for TE polarization is designed. The schematic of the grating has four layers. The first layer with SiO2 is triangular structure. Rigorous coupled wave analysis (RCWA) and Simulated Annealing (SA) algorithm are adopted to design and analyze the properties. The theoretical efficiency is nearly about 99%. The bigger error tolerance is also analyzed by rigorous coupled wave analysis. These reflective gratings as splitters should be useful optical elements in the field of high-power laser as well as other reflective applications

Three-dimensional edge extraction in optical scanning holography

Edge extraction has found applications in various image processing fields, such as in pattern recognition. In this paper, a new method is proposed for edge extraction of three-dimensional objects in optical scanning holography (OSH). Isotropic and anisotropic edge extraction of 3D objects is simulated using spiral phase plates in OSH operating in an incoherent mode. We propose to use a delta function and a spiral phase plate as the pupil functions to realize isotropic and anisotropic edge extraction. Our computer simulations show the capability of extracting the edges of a given 3D object by spiral phase filtering in OSH

Numerical simulations of 1 kHz, high-energy, broadband multipass amplification for a Ho:YLF chirped pulse amplification system

We demonstrate the high-gain of two double-pass Ho:YLF amplifiers with high-energy seed pulses injection via a modified population inversion Frantz-Nodvik model by numerical simulation. From the numerical simulation results, 26.2 mJ/1 kHz amplified pulses can be obtained by two double-pass amplifiers with 20 mu J/1 kHz, 40 nm (FWHM) bandwidth seed pulses injection. Due to similar to 1300 gain, the bandwidth of the amplified pulse decreases to about 3.5 nm (FWHM), corresponding to 466 fs pulse duration near 2 mu m wavelength. Therefore, the spectrum shaping of seed pulses is induced to suppress the gain narrowing effect. Then, the pulses can be amplified to 22.8 mJ with a spectrum of 16 nm (FWHM), which supports 368 fs pulse duration near 2 mu m by simulation

A hybrid Gerchberg Saxton-like algorithm for DOE and CGH calculation

The Gerchberg-Saxton (GS) algorithm is widely used in various disciplines of modern sciences and technologies where phase retrieval is required. However, this legendary algorithm most likely stagnates after a few iterations. Many efforts have been taken to improve this situation. Here we propose to introduce the strategy of gradient descent and weighting technique to the GS algorithm, and demonstrate it using two examples: design of a diffractive optical element (DOE) to achieve off-axis illumination in lithographic tools, and design of a computer generated hologram (CGH) for holographic display. Both numerical simulation and optical experiments are carried out for demonstration. (C) 2016 Elsevier Ltd. All rights reserved

Automatic spectral calibration for polarization-sensitive optical coherence tomography

Innovation Action Plan of Science and Technology Commission of Shanghai Municipality [15441905600]; Open Fund of Key Laboratory of Optoelectronic Information Processing of University in Guangxi [KFJJ2016-04]Accurate wavelength assignment is important for Fourier domain polarization-sensitive optical coherence tomography. Incorrect wavelength mapping between the orthogonal horizontal (H) and vertical (V) polarization channels leads to broadening the axial point spread function and generating polarization artifacts. To solve the problem, we propose an automatic spectral calibration method by seeking the optimal calibration coefficient between wavenumber k(H) and k(V). The method first performs a rough calibration to get the relationship between the wavelength. and the pixel number x of the CCD for each channel. And then a precise calibration is taken to bring both polarization interferograms in the same k range through the optimal calibration coefficient. The optimal coefficient is automatically obtained by evaluating the cross-correlation of A-line signals. Simulations and experiments are implemented to demonstrate the performance of the proposed method. The results show that, compared to the peaks method, the proposed method is suitable in both Gaussian and non-Gaussian spectrums with a higher calibration accuracy

Tailoring femtosecond 1.5-mu m Bessel beams for manufacturing high-aspect-ratio through-silicon vias

National Natural Science Foundation of China [61327902, 11134010]; National Basic Research Program of China [2014CB921300]Three-dimensional integrated circuits (3D ICs) are an attractive replacement for conventional 2D ICs as high-performance, low-power-consumption, and small-footprint microelectronic devices. However, one of the major remaining challenges is the manufacture of high-aspect-ratio through-silicon vias (TSVs), which is a crucial technology for the assembly of 3D Si ICs. Here, we present the fabrication of high-quality TSVs using a femtosecond (fs) 1.5-mu m Bessel beam. To eliminate the severe ablation caused by the sidelobes of a conventional Bessel beam, a fs Bessel beam is tailored using a specially designed binary phase plate. We demonstrate that the tailored fs Bessel beam can be used to fabricate a 2D array of approximately circle divide 10-mu m TSVs on a 100-mu m-thick Si substrate without any sidelobe damage, suggesting potential application in the 3D assembly of 3D Si ICs

Observation of polariton resonances with five-level M-type atoms in an optical cavity

National Natural Science Foundation of China [91321101, 11274112, 11474092]We study the polariton resonances with the five-level M-type atoms inside an optical cavity through the observation of the cavity transmission spectrum. The ultranarrow peaks associated with the dark-state polaritons in the system can be achieved by adjusting three coupling fields. Simple theory analysis and numerical simulations are also presented. (C) 2017 Published by Elsevier B.V

Harmonic generation at air-soil interface by femtosecond laser filament

Key Project from the Bureau of International Cooperation Chinese Academy of Sciences [181231KYSB20160045]; 100 Talents Program of the Chinese Academy of Sciences; State Key Laboratory of High Field Laser Physics; [XDB16]We observe the third-harmonic generation and second-harmonic generation together with element fluorescence from the interaction of a femtosecond laser filament with a rough surface sample (sandy soil) in non-phase-matched directions. The harmonics prove to originate from the phase-matched surface harmonics and air filament, then scatter in non-phase-matched directions due to the rough surface. These harmonics occurr when the sample is in the region before and after the laser filament, where the laser intensity is not high enough to excite the element fluorescence. The observed harmonics are related to the element spectroscopy, which will benefit the understanding of the interaction of the laser filament with a solid and be helpful for the application on filament induced breakdown spectroscopy

Investigation of pre-pulse pumping laser for preserving temporal waveform of stimulated Raman scattering

National Science Foundation of China (NSFC) [11127901, 11134010]; Shanghai Sailing Program [15YF1413500]A modified polarized beam combination technique is proposed for preserving the temporal waveforms of stimulated Raman scattering. 1064 nm pre-pulse pumping lasers prior to the main pumping laser with a delay time are generated and injected into a Ba(NO3)(2) Raman medium to excite the crystal firstly. The influences of pre-pulse lasers with various energy levels on the temporal shapes of Raman lasers are investigated, and it is demonstrated that the temporal waveforms of the Raman laser are distorted once the energies of the pre-pulse are below and above the required energy for preserving the temporal shapes of Stokes radiation. It is also discovered that the temporal shape of the 1197 nm Raman laser cannot be perfectly preserved if the energy of the 1064 nm main laser is too low or the relative delay time is too large. Moreover, the optical conversion efficiency and Stokes laser energy obtained under pumping lasers with single and double intensity peaks are compared

Effective mass dependence in laser-induced absorption of ZnO pumped by mid-infrared laser pulse

National Natural Science Foundation of China [11127901, 61221064, 11134010, 11227902, 11222439, 11274325]; 973 Project [2011CB808103]The time-resolved laser-induced absorption below the band edge in a ZnO sample is observed in the presence of a strong mid-infrared (MIR) pulse. The laser-induced absorption increases with the pump intensity, but it is different in two directions ([1100] and [1120] direction). The simulation results demonstrate that this phenomenon is primarily caused by the direction dependence of the reduced effective mass of electron and hole. For smaller reduced effective mass, the number of multi-photon ionization channel becomes larger, the probe photons are more likely to be absorbed and the absorption coefficients is larger, so lower pump intensity is needed for absorption saturation. (C) 2015 Elsevier B.V. All rights reserved