Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Re-clustering of neodymium ions in neodymium, buffer ion-codoped alkaline-earth fluoride transparent ceramics
No full textNational Nature Science Foundation of China [61378069, 61405221]; Youth Innovation Promotion Association of the Chinese Academy of Sciences (CAS); National Key Research and Development Program of China [2017YFB0310503]We systematically present the relationship between the optical properties and deformation of Nd, B-codoped MF2 (B = buffer ions; M = alkaline earth metal ions) transparent ceramics. Re-clustering of Nd3+ ions in ceramics was experimentally observed for the first time. The mechanism of re-clustering was studied
Tin diselenide as a new saturable absorber for generation of laser pulses at 1 mu m
No full textNational Natural Science Foundation of China (NSFC) [11274203]; Strategic Priority Research Program of CAS [XDB16030700]; Key Research Program of Frontier Science of CAS [QYZDB-SSW-JSC041]The nonlinear optical responses of two-dimensional (2D) few-layer tin diselenide (SnSe2) have been investigated in this work. By applying the Z-scan technique, the saturable absorption of SnSe2 thin film has been observed at a wavelength of similar to 1 mu m, which enables SnSe2, a new saturable absorber for pulsed laser generation. A detailed exploration of the nonlinear absorption of SnSe2 film and their dependence on excitation pulse energy is carried out. Our results show that saturation intensity of the nonlinear absorption is similar to 23.78 GW/cm(2) and corresponding nonlinear absorption coefficients are at a range from -13596 to -2967.3 cm/GW. By employing the SnSe2-coated mirror as a saturable absorber, the passively Q-switched lasing has been achieved on a crystalline waveguide platform at similar to 1 mu m. (C) 2017 Optical Society of Americ
Effect of GeO2 on the lasing performance of Yb: Phosphate glass fiber
No full textNational Natural Science Foundation of China [61177083, 51272262, 61405215]A novel GeO2 modified Yb: phosphate glass with good luminescent properties has been demonstrated. P and PG fibers were fabricated by the stack-and-draw method. An output power of 6.4 W with slope efficiency of 46% was obtained from 40.5 cm long PG fiber, while 40.2 cm long P fiber had an output power of 2.7 W and 34% slope efficiency. (C) 2016 Elsevier B.V. All rights reserved
Filamentation and supercontinuum generation in lanthanum glass
No full textHundred Talents Program of the Chinese Academy of Sciences; National Natural Science Foundation of China (NSFC) [61475171, 11374084, 61307056]; Pujiang Talent Plan [14PJ1409200]; Joint Research Project of Chinese Academy of Science and Japan Society for the Promotion of Science [GJHZ1412]; National High Technology Research and Development Program of China [2012AA041203]A broadband supercontinuum (SC) covering 400-2800 nm in a 20 dB dynamic range is reported in a piece of highly nonlinear, low-dispersion bulk lanthanum glass without employing any lens to focus the pump pulse. The spectrum width obtained in this study is broader than the maximum spectrum width obtained in silica photonic crystal fibers. The filaments and bright conical visible emission patterns of the SC are analyzed. Under optimum pump conditions, an SC conversion efficiency of 75% is obtained. The SC conversion efficiency is confirmed to be stable. Additionally, the relationship between the input peak intensity and the output beam radius is elucidated by simulating the propagation of a Gaussian beam in the bulk lanthanum glass. A 0.20mm stable laser beam radius at the end of the propagation domain is demonstrated in a certain input peak intensity range. This small value of the beam radius indicates that most of the output power is localized over a small region because of the Kerr focusing effect despite the existence of conical emission in the SC generation by filamentation. The findings of this study are of significance for the development of ultra-broadband SC sources based on bulk glasses and high peak power lasers
Yb-Er doped composite fiber with silicate clad and phosphate core prepared by stack-and-draw method
No full textNatural Science Foundation of Shanghai [17ZR1434000]; China Postdoctoral Science Foundation [2016M601653]We report on a single-clad fiber with heavily Yb-Er-doped phosphate core and silicate clad. The calculated core NA is similar to 0.11. The diffusion is slight between the core and clad due to the small drawing temperature contrast between the phosphate and silicate glass. A strong ASE was obtained with central wavelength of 1534 nm
Viterbi equalization for long-distance, high-speed underwater laser communication
No full textNational High Technology Research and Development Program [2014AA093301]In long-distance, high-speed underwater laser communication, because of the strong absorption and scattering processes, the laser pulse is stretched with the increase in communication distance and the decrease in water clarity. The maximum communication bandwidth is limited by laser-pulse stretching. Improving the communication rate increases the intersymbol interference (ISI). To reduce the effect of ISI, the Viterbi equalization (VE) algorithm is used to estimate the maximum-likelihood receiving sequence. The Monte Carlo method is used to simulate the stretching of the received laser pulse and the maximum communication rate at a wavelength of 532 nm in Jerlov IB and Jerlov II water channels with communication distances of 80, 100, and 130 m, respectively. The high-data rate communication performance for the VE and hard-decision algorithms is compared. The simulation results show that the VE algorithm can be used to reduce the ISI by selecting the minimum error path. The trade-off between the high-data rate communication performance and minor bit-error rate performance loss makes VE a promising option for applications in long-distance, high-speed underwater laser communication systems
Dynamic three-dimensional multifocal spots in high numerical-aperture objectives
No full textNational Natural Science Foundation of China (NSFC) [61675093, 61705096]; Shandong Provincial Natural Science Foundation, China [ZR2017MA035]Multifocal spots in high numerical-aperture (NA) objectives has emerged as a rapid, parallel, and multi-location method in a multitude of applications. However, the typical method used for forming three-dimensional (3D) multifocal spots based on iterative algorithms limits the potential applications. We demonstrate a non-iterative method using annular subzone phases (ASPs) that are composed of many annular subareas in which phaseonly distributions with different 3D displacements are filled. The dynamic 3D multifocal spots with controllable position of each focal spot in the focal volume of the objective are created using the ASPs. The experimental results of such dynamic tunable 3D multifocal spots offer the possibility of versatile process in laser 3D fabrication, optical trapping, and fast focusing scanned microscopic imaging
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
Fabrication of high-Q microresonators in dielectric materials using a femtosecond laser: Principle and applications
No full textNational Basic Research Program of China [2014CB921300]; National Natural Science Foundation of China (NSFC) [61275205, 11174305, 61505231]; Open Fund of the State Key Laboratory on Integrated Optoelectronics [IOSKL2015KF34]Femtosecond laser micromachining has been a promising technique for fabricating three-dimensional (3D) micro/nano-structures in various kinds of dielectric materials with unprecedented spatial resolutions as well as flexibility in terms of the geometry and the materials can be processed. This unique capability opens opportunities for fabrication of 3D high-quality (Q) microresonators, which are one of the key elements in modern photonic applications. Here, we review the recent progress in fabrication of high-Q microresonators on glass and crystalline substrates by employing femtosecond laser direct writing. We demonstrate the applications of the fabricated microresonators in generating low-threshold lasers, high-sensitivity chemical sensing and nonlinear optical wavelength conversion. (C) 2016 Elsevier B.V. All rights reserved
Enhanced emission of the 1.50-1.67 mm fluorescence in Er3+, Ce3+-codoped Lu3Al5O12 crystal
No full textGuangdong Project of Science and Technology [2014B090903014, 2014B010131004, 2014B010124002, 2015B090901014, 2016B090917002]; National Natural Science Foundation of China [61475067, 11404332, 51302283, 51472257]The use of Ce3+ codoping for enhancement of the Er3+: I-4(13/2) -> I-4(15/2) emissions were investigated in the Lu3Al5O12 (LuAG) crystal for the first time. The effect of Ce3+ codoping on the 1.50-1.67 mu m photo-luminescence of Er3+ was investigated in detail. It was found that Ce3+ greatly enhanced Er3+: 1.50-1.67 mu m emission by increasing the non-radiative decay rate from the I-4(11/2) to I-4(13/2) of Er3+, leading to greater population accumulation in the I-4(13/2) level. With the codoped of Ce3+ ion in Er: LuAG crystal, the lifetime of Er3+: I-4(11/2) level decreases dramatically from 90 ms to 58 mu s, while the lifetime of Er3+: I-4(13/2) level remains almost unchanged. These results suggest that the Er/Ce: LuAG crystal may become an attractive host for developing solid state lasers at around 1.50-1.67 mm laser applications under a conventional 970 nm LD pump. (C) 2016 Elsevier B.V. All rights reserved