Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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High-Stability High-Energy Picosecond Optical Parametric Chirped Pulse Amplifier as a Preamplifier in Nd:Glass Petawatt System for Contrast Enhancement
No full textNational Natural Science Foundation of China [11604350, 61405211]We demonstrate a novel picosecond optical parametric preamplification to generate high-stability, high-energy and high-contrast seed pulses. The 5 ps seed pulse is amplified from 60 pJ to 300 mu J with an 8.6 ps/ 3mJ pump laser in a signal stage of short pulse non-collinear optical parametric chirped pulse amplification. The total gain is more than 106 and the rms energy stability is under 1.35%. The contrast ratio is higher than 108 within a scale of 20 ps before the main pulse. Consequently, the improvement factor of the signal contrast is approximately equal to the gain 106 outside the pump window
Target Area Design of an Inertial Confinement Fusion Laser Driver Compatible with Multiple Irradiation Configurations of Targets
No full textCollaboration on Advancing Key Techniques for Inertial Fusion Energy in China [2012DFG62040]The target area of a 288-beam inertial confinement fusion laser driver was designed to allow lasers for direct-drive illumination, spherical hohlraum with six laser entrance holes (6LEHs), and baseline cylindrical hohlraums. The suggested radius of a target chamber was 6.0 m based on the ratio of the total port area to chamber area. Beam port distribution on the chamber was calculated if the direct propagation of laser beams into opposing beam ports was avoided, and this distribution was compatible with spherical hohlraums with 6LEHs without additional ports opened. According to the symmetry of the beam port distribution, an X-shaped beam-guiding system (BGS) in the switchyard was proposed and arranged within a baseline algorithm. The switch between direct-and indirect-drive modes was easy to operate using this BGS concept
Tunable compensation of GVD-induced FM-AM conversion in the front end of high-power lasers
No full textNational Natural Science Foundation of China (NSFC) [61405211]Group velocity dispersion (GVD) is one of the main factors leading to frequency modulation (FM) to amplitude modulation (AM) conversion in the front end of high-power lasers. In order to compensate the FM-AM modulation, the influence of GVD, which is mainly induced by the phase filter effect, is theoretically investigated. Based on the theoretical analysis, a high-precision, high-stability, tunable GVD compensatory using gratings is designed and experimentally demonstrated. The results indicate that the compensator can be implemented in high-power laser facilities to compensate the GVD of fiber with a length between 200-500 m when the bandwidth of a phase-modulated laser is 0.34 nm or 0.58 nm and the central wavelength is in the range of 1052.3217-1053.6008 nm. Due to the linear relationship between the dispersion and the spacing distance of the gratings, the compensator can easily achieve closed-loop feedback controlling. The proposed GVD compensator promises significant applications in large laser facilities, especially in the future polarizing fiber front end of high-power lasers. (C) 2017 Optical Society of Americ
Three-dimensional identification card and applications
No full textThree dimensional Identification Card, with its three-dimensional personal image displayed and stored for personal identification, is supposed be the advanced version of the present two-dimensional identification card in the future [ 1]. Three dimensional Identification Card means that there are three-dimensional optical techniques are used, the personal image on ID card is displayed to be three-dimensional, so we can see three dimensional personal face. The ID card also stores the three-dimensional face information in its inside electronics chip, which might be recorded by using two-channel cameras, and it can be displayed in computer as three-dimensional images for personal identification. Three-dimensional ID card might be one interesting direction to update the present two-dimensional card in the future. Three-dimension ID card might be widely used in airport custom, entrance of hotel, school, university, as passport for on-line banking, registration of on-line game, etc..
Three-dimensional edge extraction in optical scanning holography
No full textEdge 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
Automatic spectral calibration for polarization-sensitive optical coherence tomography
No full textInnovation 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
Fast autofocusing in digital holography using the magnitude differential
No full textNational Natural Science Foundation of China (NSFC) [61327902, 61377005]; Chinese Academy of Sciences (CAS) [QYZDB-SSW-JSC002]Typical methods of automatic estimation of focusing in digital holography calculate every single reconstructed frame to get a critical function and then ascertain the focal plane by finding the extreme value of that function. Here, we propose a digital holographic autofocusing method that computes the focused distance using the first longitudinal difference of the magnitude of the reconstructed image. We demonstrate the proposed method with both numerical simulations and optical experiments of amplitude-contrast and phase-contrast objects. The results suggest that the proposed method performs better than other existing methods, in terms of applicability and computation efficiency, with potential applications in industrial and biomedical inspections where automatic focus tracking is necessary. (C) 2017 Optical Society of Americ
Interferometric rotating point spread function
No full textChina Postdoctoral Science Foundation [2015M580356]; National Natural Science Foundation of China [61377005, 61327902]; Chinese Academy of Sciences [QYZDB-SSW-JSC002]Rotating point spread functions (PSF), such as the double helix (DH) PSF, are widely used in localization-based super-resolution imaging because of their large working depth range. In this article, we propose an interferometric DH PSF (iDH PSF) using two opposed objective lenses as in the 4Pi microscope. In the proposed iDH PSF, the super-resolution in the axial PSF is transferred to the azimuthal rotation. Moreover, we design an iDH PSF whose imaging range reaches 3 mu m, which is roughly 3 times as much as that which can be obtained by using other interferometric localization-based super-resolution imaging methods
Modal wavefront reconstruction based on Zernike polynomials for lateral shearing interferometry
No full textNational Natural Science Foundation of China (NSFC) [61405210, 61275207, 61474129]; Natural Science Foundation of Shanghai [14ZR1444900]The Zernike-polynomials-based modal reconstruction method is an important wavefront reconstruction method for lateral shearing interferometry. There are four typical Zernike-polynomial-based modal reconstruction methods: the Rimmer-Wyant method, the elliptical orthogonal transformation method, the numerical orthogonal transformation method (NOT), and the difference Zernike polynomial fitting method (DZF). In a previous paper [Appl. Opt. 51, 5028 (2012)], the overall performances of these four methods were comprehensively compared with each other. The conclusions showed that NOT and DZF have the highest reconstruction accuracies among these four methods. In addition, it was shown that the performance of NOT is identical to that of DZF; however, the reason behind this was not known until now, to our knowledge. In the present paper, we present a strictly mathematical proof for this highly significant result. (C) 2016 Optical Society of Americ
Ultrafast Nonlinear Optical Properties of a Graphene Saturable Mirror in the 2 mu m Wavelength Region
No full textScience Foundation Ireland [12/IA/1306]; European Commission under the Seventh Framework programme (ISLA) [287732]; NSFC [61675217, 61522510]; CAS [XDB16030700, QYZDB-SSW-JSC041]; Program of Shanghai Academic Research Leader [17XD1403900]Mid-infrared ultrafast lasers have emerged as a promising platform for both science and industry because of their inherent high raw power and eye-safe spectrum. 2D nanostructures such as graphene have emerged as promising photonic materials for laser mode-locking to generate ultrashort pulses. However, there are still many unanswered questions about graphene's key advantages to be practical devices, especially over the matured semiconductor saturable absorber mirror (SESAM). In this work, we conducted systematic comparisons on the nonlinear optical properties of graphene and that of a commercial SESAM at 2 mu m wavelength. Our results showed that graphene has significant advantages over the commercial SESAM, exhibiting similar to 28% less absorptive cross-section ratio of excited-state to ground-state and similar to 50 times faster relaxation time. This implies that graphene can be exploited as a better mode-locker than the current commercial SESAM for high power, high repetition rate and ultrafast mid-infrared laser sources