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Accepted papers to appear in an upcoming issue

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Subnanosecond KTP OPO intracavity pumped by a Kerr-lens mode-locked YVO4/Nd:YVO4 laser coupled with an AOM

Hongwei Chu, Jia Zhao, Kejian Yang, Shengzhi Zhao, Tao Li, Dechun Li, Guiqiu Li, and qiaowen chao

Doc ID: 243524 Received 22 Jun 2015; Accepted 27 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: A Kerr-lens mode-locked (KLM) YVO4/Nd:YVO4 laser coupled with the acousto-optic modulator (AOM) Q-switching near 1064 nm was employed to pump an intracavity KTiOPO4 (KTP) optical parametric oscillator (OPO). Subnanosecond signal wave near 1572 nm with low repetition rate was realized. At an AOM repetition rate of 8 kHz, the maximum output power was 165 mW. The highest pulse energy, the shortest duration and the highest peak power of a mode-locking signal pulse were estimated to be ~ 10.3 μJ, ~ 120 ps and ~ 82 kW, respectively.

Computational Investigation of InxGa1−xN/GaN Quantum Dot Intermediate Band Solar Cell

Dr Mohammad Monirujjaman Khan and Raqibull Hasan

Doc ID: 236140 Received 19 Mar 2015; Accepted 23 Jul 2015; Posted 29 Jul 2015  View: PDF

Abstract: The development of high-performance solar cell using InxGa1−xN quantum dots (QDs) is an important goal when compared with the existing single/multi junction solar cell. From this perspective, InxGa1-xN /GaN quantum dot intermediate band (QDIB) solar cell is a promising candidate for exceeding the Shockley-Queisser power conversion efficiency limit of a single p-n junction solar cell. In this paper, the performance of InxGa1-xN /GaN QD-IBSC has been analyzed by solving the Schrodinger equation using Kronig-Penney model in finite potential well. In addition, two important parameters which include open circuit voltage (Voc) and short circuit current (Jsc) have been also presented with the variation of indium composition in quantum dot (QD) materials. However, the power conversion efficiency is worked out based on particular assumptions. The results show that the greater the size of QD and interdot distance (ID) leads to poor power conversion efficiency. Moreover, the maximum power conversion efficiency is noticed to be 62.84% for the position of intermediate band at 2eV energy state in the barrier region.

Non-orthogonal Objects Identification Based on Ghost Imaging

Xiaofan Gu and Shengmei Zhao

Doc ID: 240028 Received 11 May 2015; Accepted 22 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: Ghost imaging could be used to make a quick identification on the orthogonal objects by means of photocurrent correlation measurements. In this paper, we extend the method to identify the non-orthogonal objects. In the method, an object is illuminated by one of the entangled pair photons, and the other photon is diffracted to a particular direction by a pre-established multiple-exposure hologram on the idler arm. By the correlation measurements, the non-orthogonal object in the signal arm could be discriminated within a very short time. The constraints for the discrimination of the non-orthogonal objects is presented, which shows that the non-orthogonal objects can be discriminated when the overlapping portion among any two objects is less than half of all the objects in the set. The numerical simulations further verify the result.

Silicon and silicon nitride photonic circuits for spectroscopic sensing on–a–chip

Ananth Subramanian, Eva Ryckeboer, Ashim Dhakal, Frédéric Peyskens, Aditya Malik, Bart Kuyken, Haolan Zhao, Shibnath Pathak, Alfonso Ruocco, Andreas De Groote, Pieter Wuytens, Daan Martens, François Leo, Weiqiang Xie, Utsav Dave, Muhammad Muneeb, Pol Van Dorpe, Joris Van Campenhout, Wim Bogaerts, Peter Bienstman, Nicolas Le Thomas, Dries Van Thourhout, Zeger Hens, Gunther Roelkens, and Roel G. Baets

Doc ID: 241314 Received 21 May 2015; Accepted 21 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: There is a rapidly growing demand to use silicon and silicon nitride (Si₃N₄) integrated photonics for sensing applications, ranging from refractive index to spectroscopic sensing. By making use of advanced CMOS technology, complex miniaturized circuits can be easily realized on a large scale and at a low cost covering visible to mid-IR wavelengths. In this paper we present our recent work on the development of silicon and Si₃N₄ based photonic integrated circuits for various spectroscopic sensing applications. We report our findings on waveguide-based absorption, Raman and surface enhanced Raman spectroscopy. Finally we report on-chip spectrometers and on-chip broadband light sources covering very near IR to mid IR wavelengths to realize fully integrated spectroscopic systems on-a-chip.

The Dynamics of Lossless Polarization Attraction

Matteo Barozzi and Armando Vannucci

Doc ID: 242074 Received 01 Jun 2015; Accepted 21 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: We study a nonlinear lossless polarizer (NLP), a fiber-based device able to control the polarization of an optical signal, while preserving its energy. The NLP exploits the lossless polarization attraction (LPA) generated by the Kerr interactions between the signal and a fully polarized CW pump. By employing a co-propagating pump, we show that the effectiveness of LPA depends on the joint action of the Kerr nonlinearity and the mutual delay between signal and pump. We find the optimal pump wavelength placement and demonstrate that true LPA occurs only within a limited range of delay values. Thus, we explain why the co-propagating NLP is more flexible and power efficient, compared with the traditional counter-propagating NLP.

High-resolution pseudo-inverse ghost imaging

Wenlin Gong

Doc ID: 243400 Received 19 Jun 2015; Accepted 21 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: We present a technique, pseudo-inverse ghost imaging (PGI), which can dramatically enhances the spatial transverse resolution of pseudo-thermal ghost imaging (GI). In comparison with conventional GI, PGI can break the limitation on the imaging resolution imposed by the speckle's transverse size on the object plane and also enables the reconstruction of an N-pixel image from much less than N measurements. This feature also allows high-resolution imaging of gray-scale objects. Experimental and numerical data assessing the performances of the technique are presented

InP Photonic Circuits using Generic Integration

Kevin Williams, Erwin Bente, Xaveer Leijtens, Jos J.G.M. van der Tol, Meint Smit, Yuqing Jiao, Katarzyna Lawniczuk, and Dominik Heiss

Doc ID: 241319 Received 18 May 2015; Accepted 16 Jul 2015; Posted 23 Jul 2015  View: PDF

Abstract: InP integrated photonics has become a critical enabler for modern telecommunications, and is poised to revolutionise data communications, precision metrology, spectrometry and imaging. The possibility to integrate high performance amplifiers, lasers, modulators and detectors in combination with interferometers within one chip is enabling game-changing performance advances, energy savings and cost reductions. Generic integration accelerates progress through the separation of applications from a common technology development. In this paper, we review the current status in InP integrated photonics and the efforts to integrate the next generation of high-performance functionality on a common substrate using the generic methodology.

Multicolored sideband generation based on cascaded four-wave mixing with the assistance of spectral broadening in multiple thin plates

Peng Wang, Jun Liu, fangjia li, Xiong Shen, and Ruxin Li

Doc ID: 243244 Received 16 Jun 2015; Accepted 14 Jul 2015; Posted 17 Jul 2015  View: PDF

Abstract: The generation of multicolored sidebands with the spectrum from 377 nm to 970 nm in a 0.5-mm-thick N-WG280 Schott glass based on cascaded four-wave mixing (CFWM) process is demonstrated. The experimental setup is compact and economical. Pulse with a broadened spectrum from 670 nm to 900 nm is generated by utilizing two 0.18-mm-thin fused silica glass plates and is used to provide two input beams for CFWM process. The new frequency components generated from the self-phase modulation effect in the two thin glass plates contribute to the broadening of the total spectral range of the generated multicolored sidebands.

Enhanced optical Kerr nonlinearity of MoS2 on silicon waveguides

Ke Xu, LIU LINGHAI, xi wan, Jian Xu, Chi Yan Wong, and Hon Tsang

Doc ID: 242019 Received 29 May 2015; Accepted 11 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: A quasi two-dimensional layer of MoS2 was placed on top of a silicon optical waveguide to form a MoS2-silicon hybrid structure. Chirped pulse self-phase modulation measurements were carried to determine the optical Kerr nonlinearity of the structure. The observed increase in the spectral broadening of the optical pulses in the MoS2-silicon waveguide compared with the silicon waveguides indicated that the third order nonlinear effects in MoS2 is about two orders of magnitude larger than silicon. The measurements show that MoS2 has an effective optical Kerr coefficient of about 〖1.1×10〗^(-16) m^2/W. This work reveals potential application of MoS2 to enhance the nonlinearity of hybrid silicon optical devices.

Broadband ultrafast nonlinear optical response of few-layers graphene: towards the mid-infrared regime

Miao Li, Yaqin Jiang, Shunbin Lu, Chunjun Zhao, Han Zhang, Shuangchun Wen, and Bingxin Shi

Doc ID: 237862 Received 10 Apr 2015; Accepted 10 Jul 2015; Posted 16 Jul 2015  View: PDF

Abstract: The gapless linear energy dispersion of graphene endows it with unique nonlinear optical properties, including broadband nonlinear absorption and giant nonlinear refractive index. Herein, we experimentally observed that the few-layers graphene has obvious nonlinear absorption and large nonlinear refraction investigated by Z-scan technique in the mid-infrared (mid-IR) regime. Our study may not only, for the first time, verify the giant nonlinear refractive index of graphene (~10-7cm2/W) at mid-IR, which is seven orders of magnitude larger than other conventional bulk materials, but also provide some new insights for grapheme-based mid-IR photonics, potentially leading to the emergence of several new conceptual mid-IR optoelectronics devices.

Laser annealing made amplified spontaneous emission of “giant” CdSe/CdS core/shell nanocrystals transferred from bulk-like shell to quantum-confined core

chen liao, Kai Fan, Ruilin Xu, Huichao Zhang, Changgui Lu, Yiping Cui, and Jiayu Zhang

Doc ID: 241875 Received 28 May 2015; Accepted 04 Jul 2015; Posted 06 Jul 2015  View: PDF

Abstract: “Giant” CdSe/CdS core/shell nanocrystals (NCs) were synthesized with thick CdS shell (15 monolayers), and the X-ray diffraction (XRD) measurement indicates that there is zinc blende (ZB) phase in the thick CdS shell whereas it transformed into wurtzite (WZ) phase under 5 min radiation with 400 nm, 594 μJ/cm² femtosecond (fs) laser beam. The evolution of the NCs’ spontaneous emission (SPE) under the fs laser radiation was recorded with a Hamamatsu streak camera. The as-synthesized NCs exhibit a amplified spontaneous emission (ASE) at 530 nm, which come from bulk-like CdS shell due to the interfacial potential barrier that could slow down the relaxation of holes from the shell to the core. After annealed by fs laser, ASE of the g-NCs transferred from bulk-like CdS shell to quantum-confined CdSe core, because the phase transformation determinated with the XRD measurement could remove the interfacial barrier. Besides the ASE at 643 nm , two shorter-wavelength ASE peaks at 589 nm and 541 nm corresponding to optical transitions of the second (1P) and the third (1D) electron quantization shells of CdSe core appear also, indicating that Auger recombination is very effectively suppressed.

Lower the energy consumption in silicon photonic devices and systems

Zhiping Zhou, Bing Yin, Qingzhong Deng, Xinbai Li, and Jishi Cui

Doc ID: 238414 Received 20 Apr 2015; Accepted 23 Jun 2015; Posted 26 Jun 2015  View: PDF

Abstract: We review the current silicon photonic devices and their performance in connection with the energy consumption. Four classes of critical issues are identified to lower energy consumption in devices and systems: reducing the influence of the thermo-optic effect, increasing the wall-plug efficiency of lasers on silicon, optimizing energy performance of modulators, and enhancing the sensitivity of photodetectors. Major findings are: 1) MZI-based devices can achieve athermal performance without any extra energy consumption while microrings do not have an efficient passive athermal solution; 2) While direct bonded III-V-based Si lasers can meet system power requirement for now, hetero-epitaxial grown III-V QD lasers are very competitive and may be a better option for the future; 3) Resonant modulators are promising for low energy consumption operation even when the power to stabilize their operation is included, especially coupling modulators; 4) Benefiting from high sensitivity and low cost, Ge/Si APD is the most promising photodetector and can be used to effectively reduce the optical link power budget. These analyses and solutions will contribute to further lowering the energy consumption to meet the aggressive energy demands in future systems.

Mode converter based on dual-core all-solid photonic bandgap fiber

Wang Yuan, Yongjun Zhang, Shanyong Cai, Mingying Lan, Song Yu, and Wanyi Gu

Doc ID: 239689 Received 08 May 2015; Accepted 15 Jun 2015; Posted 19 Jun 2015  View: PDF

Abstract: In this paper, we present a mode selective coupler based on a dual-core all-solid photonic bandgap fiber (ASPBGF). Because of its all solid property, mode converter based on AS-PBGF is easier to splice to other fibers than that based on air-hole photonic crystal fiber (PCF). Mode conversions between LP 01 mode and LP11 mode, between LP01 mode and LP21 mode, between LP01 mode and LP02 mode are obtained at the wavelength λ = 1550 nm. The 3 dB wavelength bandwidth of these mode converters are 47.8 nm, 20.3 nm and 20.3 nm respectively, which is better than that based on conventional air-hole PCF.

Theoretical investigation on core modes cutoff condition for tapered multi-core fiber

Xuanfeng Zhou, Zilun Chen, Hang Zhou, and Jing Hou

Doc ID: 234093 Received 06 Feb 2015; Accepted 19 May 2015; Posted 22 May 2015  View: PDF

Abstract: Core mode cutoff is a very useful concept not only for a tapered single-core fiber (SCF) but also for a tapered multi-core fiber (MCF) to realize cladding mode transmission. In this paper, cutoff conditions of either core mode for tapered SCFs or super-modes for MCFs are theoretically investigated. Rigorous analytical formulas are derived for the modes of SCF by three-layer waveguide (TLW) model and an approximation formula of cutoff condition is given for the LP01 mode. The super-modes of MCFs are analyses by coupling mode theory and the cutoff condition is calculated by a numerical method. Simulation results show that the in-phase super-mode of MCFs has a similar cutoff condition with that of SCF. Based on this property, a convenient approximate formula is given to estimate the cutoff condition of the in-phase super-mode for tapered MCFs.

73 nJ、109 fs Yb-doped fiber laser at 19 MHz repetition rate in amplifier similariton regime

Yizhou Liu, Yifan Cui, Jian Zhang, Aimin Wang, and Zhigang Zhang

Doc ID: 232649 Received 20 Jan 2015; Accepted 02 Apr 2015; Posted 15 Apr 2015  View: PDF

Abstract: We report femtosecond pulse generation in an amplifier similariton oscillator and a pre-chirped fiber amplifier system. The final output power is 1.4 W fundamental repetition rate is 19.1 MHz after a single state fiber amplifier. The pulse width is 109fs.

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