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Accepted papers to appear in an upcoming issue

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Towards Commercial Realization of Quantum Dot based White LEDs for General Illumination

Ken Shimizu, Marcel Böhmer, Daniel Estrada, Stefan Grabowski, Sumit Gangwal, Helmut Bechtel, Edward Kang, Kenneth Vampola, Danielle Chamberlin, Oleg Shchekin, and Jyoti Bhardwaj

Doc ID: 280995 Received 17 Nov 2016; Accepted 12 Jan 2017; Posted 13 Jan 2017  View: PDF

Abstract: We demonstrate the first commercial production-ready white LEDs for the general illumination market with red colloidal quantum dots (QD) applied in an on-chip configuration. We show red QDs with tunable peak emission and narrow FWHM in combination with conventional phosphor material can lead to LED conversion efficiency improvements of 5% to 15% over commercial phosphor based LEDs at CCT’s ranging from 5000K to 2700K. Furthermore, the challenges associated with reliability under high temperature, high blue flux intensity and high humidity operation have been overcome to meet consumer market requirements. Finally, a demonstrator lamp at 3000K color temperature and 90 CRI with QD based LEDs show a larger efficiency gain up to 17%, which is attributed to lower heat sink temperature and reduced blue LED droop.

Experimental demonstration of TMI enhancement by counter-pumped scheme in a 2 kW all-fiberized laser

Zebiao Li, Zhihua Huang, Xiaoyu Xiang, Xiaobao Liang, Shanhui Xu, Zhongmin Yang, wang jianjun, Feng Jing, and Honghuan Lin

Doc ID: 281270 Received 24 Nov 2016; Accepted 09 Jan 2017; Posted 12 Jan 2017  View: PDF

Abstract: Transverse mode instability (TMI) has became the major limitation for power scaling of fiber lasers with nearly diffraction-limited beam quality. Compared with co-pumped fiber laser, counter-pumped fiber laser reveals TMI threshold enhancement through a semi-analytical model calculation. We demonstrated a 2 kW high power counter-pumped all-fiberized laser without observation of TMI. Compared with co-pumped scheme, TMI threshold is enhanced at least 50% in counter-pumped scheme, moreover, stimulated Raman scattering and four-wave mixing are suppressed simultaneously.

High Sensitivity D-shaped Hole Fiber Temperature Sensor based on Surface Plasmon Resonance with Liquid Filling

Li Pei, Sijun Weng, jianshuai wang, Tigang NIng, and Jing Li

Doc ID: 278394 Received 10 Oct 2016; Accepted 03 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: A high sensitivity D-shaped hole fiber temperature sensor based on surface plasmon resonance (SPR) is designed and investigated by full-vector finite element method. Within the D-shaped hole fiber, the hollow D-section is coated with gold film and then injected in a high thermo-optic coefficient liquid to realize a high temperature sensitivity for the fiber SPR temperature sensor. The numerical simulation results show that the peaking loss of the D-shaped hole fiber SPR temperature sensor is huge influenced by the distance between the D-shaped hole and fiber core and the thickness of gold film, but the temperature sensitivity is insensitive to the above parameters though. When the thermo-optic coefficient is -2.8×10-4/⁰C, the thickness of gold film is 47 nm and the distance between the D-shaped hole and fiber core is 5 μm, the temperature sensitivity of D-shaped hole fiber SPR sensor can reach to -3.635 nm/⁰C.

Polarization evolution of vector beams generated by q-plates

Weixing Shu, Xiaohui Ling, Xiquan Fu, Yachao Liu, Yougang Ke, and Hailu Luo

Doc ID: 280016 Received 04 Nov 2016; Accepted 01 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: The polarization evolution of vector beams generated by q-plates is investigated theoretically and experimentally. An analytical model is developed for the vector beam created by a general quarter-wave q-plate based on vector diffraction theory. It is found that the polarization distribution of vector beam varies with position and the value q. In particular, for the incidence of circular polarizations, the exit vector vortex beam has polarization states that cover the whole surface of the Poincaré sphere, thereby constituting a full Poincaré beam. For the incidence of linear polarizations, the vector beam is not cylindrical but specular symmetric, and exhibits an azimuthal spin splitting. These results are in sharp contrast with those derived by the commonly used model, i.e. regarding the incident light as a plane wave. By implementing q-plates with dielectric metasurfaces further experiments validate the theoretical results.

Demonstration of an ultra-low threshold phonon laser with coupled microtoroid resonators in vacuum

Xiaoshun Jiang, Guanzhong Wang, Mingming Zhao, Yingchun Qin, Zhangqi Yin, and Min Xiao

Doc ID: 280694 Received 11 Nov 2016; Accepted 01 Jan 2017; Posted 06 Jan 2017  View: PDF

Abstract: We demonstrate an ultra-low-threshold phonon laser using a coupled-microtoroid-cavity system by introducing a novel coupling approach. The scheme exhibits both high optical quality factors and high mechanical quality factors. We have experimentally obtained the mechanical quality factor up to 18,000 in vacuum for a radial breathing mode of 59.2 MHz. The measured phonon lasing threshold is as low as 1.2 µW, which is ∼5 times lower than the previous result.

General coupled mode analysis of geometry symmetric waveguide array with non-uniform gain and loss

Jun Jun Xiao, Zhenzhen Liu, Qiang Zhang, and Yuntian Chen

Doc ID: 275860 Received 15 Sep 2016; Accepted 26 Dec 2016; Posted 06 Jan 2017  View: PDF

Abstract: Exceptional point (EP) is one of the typical properties of parity-time symmetric systems, arising from the mode coupling with identical resonant frequencies or propagation constants in optics. Here we show that in addition to two different modes coupling, non-uniform distribution of gain and loss leads to the offset from the original propagation constant including both real and imaginary parts, resulting in the absence of EP. These behaviors are examined by the general coupled mode theory from first-principle of Maxwell equations, which yields results that are more accurate than those from the classical coupled mode theory. Numerical verification by finite element method is provided. In the end, we present an approach to achieve lossless propagation in geometry symmetric waveguide array.

Q-switched fiber laser based on saturable absorption of ferroferric-oxide nanoparticles

Dong Mao, Cui Xiaoqi, Wending Zhang, Li Mingkun, Feng Tianxian, bobo du, Hua Lu, and Jianlin Zhao

Doc ID: 274471 Received 24 Aug 2016; Accepted 21 Dec 2016; Posted 22 Dec 2016  View: PDF

Abstract: Ferroferric-oxide (Fe3O4) nanoparticles, a typical magnetic material with semi-conductive property, display a large third-order optical nonlinearity due to the finite size and surface effect. Here, we demonstrate that Fe3O4 nanoparticles exhibit nonlinear saturable absorption property at 1.55 µm, and two filmy saturable absorbers are fabricated by incorporating the nanoparticles with polyvinyl alcohol (PVA) or polyimide (PI). Based on proposed saturable absorbers, passively Q-switched pulses are obtained in an erbium-doped fiber laser. It is demonstrated that PI-based saturable absorber can afford higher power than PVA-based saturable absorber, which can be attributed to the high fusion point of PI. The Fe3O4-PI saturable absorber exhibits features of high-damage threshold, low-cost, and high-flexibility, which could be applied in fields of near-infrared pulsed laser, material processing, optical sensors, and modulators.

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