Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Facial color measurement based on camera colorimetric characterization
No full textThe objective measurement of facial skin color and its variance is of great significance as much information can be obtained from it. In this paper, we developed a new skin color measurement procedure which includes following parts: first, a new skin tone color checker made of pantone Skin Tone Color Checker was designed for camera colorimetric characterization; second, the chromaticity of light source was estimated via a new scene illumination estimation method considering several previous algorithms; third, chromatic adaption was used to convert the input facial image into output facial image which appears taken under canonical light; finally the validity and accuracy of our method was verified by comparing the results obtained by our procedure with these by spectrophotometer
A hybrid Gerchberg Saxton-like algorithm for DOE and CGH calculation
No full textThe 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
Conical refraction, for annular pumping of an efficient vortex Nd:YAG laser
No full textNational Natural Science Foundation of China [61275206, 61475166]; National Science Foundation for Young Scientists of China [61405226]; Shanghai Natural Science Fund [14ZR1445200]We presented a proof-of-concept investigation upon an end-pumped and vortex Nd:YAG laser. In this laser, for the first time, the conical refraction (CR) ring of a biaxial KGd(WO4)(2) crystal was used for annular pumping. Owing to nearly 100% conversion efficiency in forming the CR ring, the Nd: YAG laser was highly efficient and emitted LG(01)-mode vortex light with 177.5 mW beam power and 65% slope efficiency. This study showed the CR ring pumping would favor the production of a compact, simple and efficient vortex laser. It is expected that, in future, the CR ring pumping technique would also facilitate the high-power vortex solid-state laser where a long gain medium is required
Simplified modal method for slanted grating
No full textNational Nature Science Foundation of China [61405214]We report the simplified modal method for the slanted grating based on the accurate dispersion equation. The vividly physical insight is presented to interpret the diffraction process for slanted grating. We also present that the simplified modal method with the two-lowest mode condition is effective for a large slanted angle up to 26 degrees. By examining the eignefunction, the mode index, and the two-lowest mode condition, we provide new evidences to verify the assumption that a slanted grating with subwavelength period can be analyzed as an equivalent rectangular grating using the simplified modal method, which is right and convenient to use for a small slanted angle up to 20 degrees. Numerical simulations of the simplified modal method are coincident with rigorous coupled wave analysis for small slanted angle gratings. Thus the simplified modal method can be used for small slanted angle grating since the equivalence of slanted grating and rectangular grating is verified due to its vivid physical analysis. (C) 2016 Elsevier B.V. All rights reserved
Observation of polariton resonances with five-level M-type atoms in an optical cavity
No full textNational 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
Propagation effects in the generation process of high-order vortex harmonics
No full textNational Natural Science Foundation of China [11374318, 11674312, 61775087]; Natural Science Foundation of Jiangsu [BK20161159]We numerically study the propagation of a Laguerre-Gaussian beam through polar molecular media via the exact solution of full-wave Maxwell-Bloch equations where the rotating-wave and slowly-varying-envelope approximations are not included. It is found that beyond the coexistence of odd-order and even-order vortex harmonics due to inversion asymmetry of the system, the light propagation effect results in the intensity enhancement of a high-order vortex harmonics. Moreover, the orbital momentum successfully transfers from the fundamental laser driver to the vortex harmonics which topological charger number is directly proportional to its order
Single scan femtosecond laser transverse writing of depressed cladding waveguides enabled by three-dimensional focal field engineering
No full textNational Basic Research Program of China [2013CB921904]; National Natural Science Foundation of China (NSFC) [11474010, 61590933, 11527901]; State Key Laboratory on Integrated Optoelectronics [IOSKL2015KF36]We report single scan transverse writing of depressed cladding waveguides inside ZBLAN glass with the longitudinally oriented annular ring-shaped focal intensity distribution of the femtosecond laser. The entire region of depressed cladding at the cross section, where a negative change of refraction index is induced, can be modified simultaneously with the ring-shaped focal intensity profile. The fabricated waveguides exhibit good single guided mode
Exceptional Points in Random-Defect Phonon Lasers
No full text973 Program [2013CB921804]; National Natural Science Foundation of China [11375060, 11434011, 11474087, 11774086]; ARO Grant [W911NF-16-1-0339]; Pennsylvania State University Materials Research Institute; RIKEN iTHES Project; MURI Center for Dynamic Magneto-Optics via AFOSR [FA9550-14-1-0040]; IMPACT program of JST, CREST [JPMJCR1676]; JSPS; Sir John Templeton FoundationIntrinsic defects in optomechanical devices are generally viewed to be detrimental for achieving coherent amplification of phonons, and great care has thus been exercised in fabricating devices and materials with no (or a minimal number of) defects. Contrary to this view, here we show that, by surpassing an exceptional point (EP), both the mechanical gain and the phonon number can be enhanced despite increasing defect losses. This counterintuitive effect, well described by an effective non-Hermitian phonon-defect model, provides a mechanical analog of the loss-induced purely optical lasing. This opens the way to operating random-defect phonon devices at EPs
Low insertion loss optical pulse interleaving for ultra-low phase noise photonic microwave generation
No full textNational Natural Science Foundation of China [11034008, 11274324, 11604353]; Key Research Program of the Chinese Academy of Sciences [KJZD-EW-W02]We report a 32-times multiplication of optical pulse rate based on a cascaded optical fiber ring interferometer for generating ultra-low noise photonic microwaves. The optical power loss of the interleaver is approximately 0.5 dB, which is the lowest insertion loss for optical pulse interleaving to date. The time delay in each interleaver stage is precisely controlled by measuring the power ratio between the harmonics of the generated microwaves. In addition, the relationship between the phase noise reduction from the continuous-wave shot noise limit and interleaver delay errors is verified experimentally for the first time. Finally, a phase noise level of -173 dBc/Hz for a single multiplication channel at an offset frequency of 2 MHz was measured
Quantum temporal imaging: application of a time lens to quantum optics
No full textEuropean Union [665148]We consider application of a temporal imaging system, based on the sum-frequency generation (SFG), to a nonclassical, squeezed optical temporal waveform. We analyze restrictions on the pump and the phase-matching condition in the summing crystal, which are necessary for preserving the quantum features of the initial waveform. We show that modification of the notion of the field of view (FOV) in the quantum case is necessary, and that the quantum FOV is much narrower than the classical one for the same temporal imaging system. These results are important for temporal stretching and compressing of squeezed fields, which are used in quantum-enhanced metrology and quantum communications