Shanghai Institute of Optics and Fine Mechanics,Chinese Academy of Sciences
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Influence of Ce ion Concentration on Fluorescence Properties of Ce: TAG-Al2O3 Eutectic Mixed Crystals
No full textFundamental Research Funds for the Central Universities [NZ2015112]Combining a blue LED chip with phosphor, white light can be obtained. In traditional white LEDs, the phosphor was dispersed in resin in a form of particles. Particle-resin composite has complex packaging and poor thermal stability. For high-power white LEDs, this combination cannot provide long-term stable work because of photo-degradation of the organic epoxy resin under high irradiation and high temperatures. Here we develop resin-free phosphor (Tb(1-n)Cen)(3)Al5O12-Al2O3 eutectic mixed crystals (Ce: TAG-Al2O3) to eliminate the photo-degradation issue of the organic material. They were grown by optical floating zone method. X-ray diffraction and scanning electron microscopy show that these materials have typical eutectic mixed crystal structure of sapphire and garnet phases, in which lamellar spacing is in an order of tens of microns. The doped Ce3+ ions do not influence basic structure of TAG crystal. Ce3+ ion replaces Tb3+ ion rather than Al3+ ion. Photoluminescence emission and excitation properties of the eutectic mixed crystals were investigated. They get to maximal value with 2.0% Ce-3+,Ce- and have wide excitation band at 470 nm. Luminous efficiency of eutectic mixed crystal- packaged LED is higher than that of particle- resin composite packaged LED. These results show that Ce: TAG-Al2O3 eutectic mixed crystals are promising phosphor for white LEDs
Stimulated emission and laser behaviors of Nd3+/Yb3+ Co-doped phosphate glass fiber
No full textNational Natural Science Foundation of China [61405215, 61505232]; Youth Innovation Promotion Association of the Chinese Academy of Sciences; National High Technology Research and Development Program of China [2016YFB0402201]The energy transfer phenomenon between Nd3+ and Yb3+ generates the research interest in Nd3+ / Yb3+ co-doping, because it provides a straight-forward way to combine the features of Nd3+ and Yb3+ to develop some potential applications, such as solar cells, high energy pulse and tunable lasers. Substantial research work has been conducted to study the spectroscopic properties of Nd3+ / Yb3+ in different glasses, crystal and ceramic host materials. However, it is still not very clear about the laser properties of the Nd3+ / Yb3+ co-doping system, especially the high rare-earth solubility phosphate glass. This work reports the stimulated emission and laser properties of an Nd3+ / Yb3+ co-doped phosphate glass fiber under singly 970 nm and 808 nm LD pumping. The molar doping ratio of Nd3+ : Yb3+ is 4 : 1. Using the free-space coupled method, the laser properties of the co-doped fiber under 970 nm pump are tested first in a laser cavity comprised of a butt-coupled dichroic mirror with high reflectivity (>= 99.5%) and a cleaved fiber ended with similar to 4.6% Fresnel reflectivity. It is found that with the increase of 970 nm pump power (P-970) two discrete laser peaks and one peak located at 1053 nm with a larger threshold can be observed for fiber length equal to and less than 0.7 m. The 1053 nm laser is produced by Yb3+ -> Nd3+ energy transfer, and its lasing threshold decreases with increasing fiber length in this length region. Then, the amplified spontaneous emission (ASE) spectra for fiber lengths of 0.35 m, 0.9 m and 5.0 m under 970 nm pumping are tested by cutting 6. at the output port. The test results indicate that the Yb3+ -> Nd3+ energy transfer has a modulation effect on fiber spectrum, and the modulation becomes more obvious for a longer fiber length. A two-fold promotion mechanism is suggested to explain the modulation effect: 1) the reabsorption effect of Yb3+ leading to relatively lifetime prolongation increases the Yb3+ -> Nd3+ energy transfer efficiency; 2) the red-shifted oscillator laser wavelength leads to a larger emission cross section difference between Nd3+ and Yb3+. Besides, the measurement results in 0.35-m-long fiber also suggest that the 1053 nm laser in fiber laser test may be due to a fiber temperature raising effect during the increase of P-970. The laser properties and ASE spectra of the fiber under 808 nm pumping have been studied in the same fiber test setup. However, the tested results are quite different from the 970 nm pumping case. Only one lasing peak at 1053 nm is detected, and it is found that the peak is not dependent on the 808 nm pump power (P-808)nor the fiber length. To explain this phenomenon, one energy transfer model with taking into consideration the stimulated emission of Nd3+ is derived. According to this theoretical model, Nd3+ -> Yb3+ energy transfer efficiency fast decreases with the increase of simulated emission intensity of Nd3+. This explanation is experimentally supported by a 0.05-m-long Nd3+ / Yb3+ co-doped phosphate glass fiber with varying P-808. Therefore, the adoption of Nd3+ to sensitize Yb3+ for developing some laser applications needs to consider the suppression effect of Nd3+ stimulated emission on Nd3+ -> Yb3+ energy transfer
Tunable colorimetric performance of Al2O3-YAG:Ce3+ eutectic crystal by Ce3+ concentration
No full textNatural Science Foundation of Shanghai [15ZR1444700]Ce-doped Al2O3-YAG eutectics with different percentage of Ce were successfully grown by the optical floating zone technique. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to investigate the structure. The results show that they have typical eutectic structure of interpenetrating sapphire and garnet phases with the tens of microns lamella spacing. The photoluminescence spectra of the eutectics showed that they have wide excitation band, and samples with 1.6 mol% Ce-doped has the highest emission intensity. The eutectic-packaged LED has high luminous efficiency and its color can be modulated by changing Ce concentration. The results reveal that Ce-doped Al2O3-YAG eutectic is a promising phosphor for white LED applications. (C) 2017 Elsevier B.V. All rights reserved
On the optical super-resolution dynamic readout effects of metal thin films
No full textNational Natural Science Foundation of China (NSFC) [51672292, 61627826, 61137002]The physical understanding for retrieving super-resolution pits using metal thin films in optical information storage is given, where the reflection modulations both of bright and dark fields are demonstrated experimentally due to the reflection intensity change of metal thin films. A pump-probe setup is constructed to explore the transient reflection intensity change under different pump light intensities. The results show that the reflectivity increases for Al thin films while the reflectivity decreases for Cu and Zn thin films, corresponding to the reflection modulation of the bright and dark fields, respectively. The frequency response function also verifies that the cutoff frequency is extended through reflection modulation. This work gives an understanding on the optical super-resolution readout effect of metal thin films and is very useful in promoting the development of nano-optical information storage. (C) 2016 Optical Society of Americ
Optical-power tunable dual-wavelength laser around 1 mu m in Nd3+/Yb3+ co-doped phosphate glass fiber
No full textNational Natural Science Foundation of China (NSFC) [61405215, 61505232]; Youth Innovation Promotion Association of the Chinese Academy of Sciences; National High Technology Research and Development Program of China [2016YFB0402201]This work reports the generation of an optical-power tunable 1 mu m dual-wavelength fiber laser in Nd3+/Yb3+ co-doped phosphate glass fiber under 970 nm and 808 nm laser diode pumping. A bidirectional free-space pump laser setup was adopted. An optical-power tunable dual-wavelength laser can be easily realized by the control of 808 nm pump power magnitude. Based on a series of laser tests under different pump conditions and theoretical calculation of the Nd3+ -> Yb3+ energy transfer efficiency, the control mechanism was found to be the stimulated emission modulation of Nd3+ on Yb3(+) lasing. This property is helpful to enhance the knowledge of the Nd3+/Yb3+ co-doping system
Coherent supercontinuum generation from 1.4 to 4 mu m in a tapered fluorotellurite microstructured fiber pumped by a 1980 nm femtosecond fiber laser
No full textNSFC [61378004, 61527823, 61575210, 61535009, 61077033, 11474132]; Opened Fund of the SKLIO; TNList Cross-discipline Foundation; MEXT, Support Program for Forming Strategic Research InfrastructureCoherent supercontinuum light expanding from 1.4 to 4 mu m is generated in a 4 cm long tapered fluorotellurite microstructured fiber (MF) pumped by a 1980 nm femtosecond fiber laser. The spectral broadening in the tapered fluorotellurite MF is caused by self-phase modulation, the Raman soliton, and red-shifted dispersive wave generation. Our results show that tapered fluorotellurite MFs are promising nonlinear medium for generating coherent broadband mid-infrared supercontinuum light. Published by AIP Publishing
Passively Q-switched Ho, Pr: LiLuF4 bulk laser at 2.95 mu m using WS2 saturable absorbers
No full textNational Key Research and Development Program of China [2016YFB1102201]; National Natural Science Foundation of China (NSFC) [61405213, 61405101]; Science and Technology Project of Qingdao [16-5-1-9-jch]We demonstrate a passively Q-switched Ho, Pr: LiLuF4 laser at 2.95 mu m using a WS2 saturable absorber (SA). A shortest pulse width of 654 ns was achieved with an average output power of 82 mW and the repetition rate of 90.4 kHz at T = 2%. Our result reveals that WS2 -SAs have great potential to be the modulator in mid-IR wavelength range.
Ultrastable Multiclock Frequency Injection and Dissemination in a Ring Fiber Network
No full textStrategic Priority Research Program of the Chinese Academy of Sciences [XDB21030800]; National Natural Science Foundation of China [61535014]Owing to the characteristics of ultralow loss and antielectromagnetic interference, using optical fiber to deliver time and frequency signals has been a preferred choice for high-precision clock dissemination and comparison. As a brilliant idea, one has been able to reproduce ultrastable signals from one local station to multiple users. In this paper, we take a step further and propose a concept of multiclock (in different locations) dissemination for multiterminals. By injecting frequency signals into one stabilized ring-like fiber network, the relative stabilities of 3.4 x 10(-14)@ 1 s for a master clock dissemination and 5.1 x 10(-14)@ 1 s for a slave clock dissemination have been achieved. The proposed scheme can greatly simplify the future "N" to "N" radio-frequency dissemination network, especially in the situation of multiclock comparison
Widely tunable all-fiber SESAM mode-locked Ytterbium laser with a linear cavity
No full textNational High Technology Research and Development Program of China [2014AA041901]; NSAF Foundation of National Natural Science Foundation of China [U1330134]; National Natural Science Foundation of China [61308024]We present a widely tunable all-fiber mode-locked laser based on semiconductor saturable absorber mirror (SESAM) with a linear cavity design. An easy-to-use tunable bandpass filter based on thin film cavity technology is employed to tune the wavelength. By tuning the filter and adjusting the polarization controller, shade-locked operation can be achieved over the range of 1023 nm-1060 nm. With the polarization controller settled, mode locked operation can be preserved and the wavelength can be continuously tuned from 1030 nm to 1053 nm. At 1030 nm, the laser delivers 9.6 mw average output power with 15.4 ps 10.96 MHz pulses at fundamental mode locked operation
Simple phase shifting lateral shearing interferometer based on a thick birefringent plate
No full textNational Science and Technology Major Project of China [2011ZX02402]; International Science and Technology Center (ISTC) Cooperation Programs of China [2011DFR10010, 2012DFG51590]A simple phase shifting lateral shearing interferometer based on a thick birefringent plate is proposed. The interferometer is composed of a thick birefringent plate and a polarizer. The thick birefringent plate works as the shear generator as well as the phase shifter. The optical path difference and shearing amount between the two sub-beams emerging from the thick birefringent plate change depending on the incident angle. For incident angles in a certain range, the shearing amount stays almost constant while the optical path difference varies linearly. Thus phase shifting can be obtained by rotating the thick birefringent plate. It is a very simple structure for the testing of a small beam, and equidistant phase shifting can be obtained by equal incident angle variation. The validity of the interferometer is verified by both simulation and experiment