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Graphene-Enabled Electrically Controlled Terahertz Meta-Lens

Bin Hu, Weiguang Liu, Zongduo Huang, Hongyu Guan, HeTing Li, Xinke Wang, Yan Zhang, Hongxing Yin, Xiaolu Xiong, Juan Liu, and Yongtian Wang

Doc ID: 324896 Received 26 Feb 2018; Accepted 15 May 2018; Posted 16 May 2018  View: PDF

Abstract: Metasurface has become a new photonic structure for providing potential applications to develop integrated devices with small thickness, because it can introduce an abrupt phase change by arrays of scatters. However, the function of the metasurface based devices lacks active control once the structure is fabricated. Here a tunable terahertz meta-lens whose focal length is able to be electrically tuned by ~4.45 λ is demonstrated experimentally. The lens consists of a metallic metasurface and a monolayer graphene. Due to the dependence of the abrupt phase change of the metasurface on the graphene chemical potential, which can be modulated using an applied gate voltage, the focal length is changed from 10.46 mm to 12.24 mm when the gate voltage increases from 0 V to 2.0 V. Experimental results are in good agreement with the theoretical hypothesis. This type of electrically controlled meta-lens could widen the application of terahertz technology.

Elucidation of "phase difference" in Raman tensor formalism

Wei Zheng, Jingshen Yan, Fadi Li, and Feng Huang

Doc ID: 326693 Received 22 Mar 2018; Accepted 14 May 2018; Posted 15 May 2018  View: PDF

Abstract: The so-called “phase difference” is commonly introduced as a phenomenological parameter in Raman tensor theory, so as to fit the experimental data well. Although phase difference is widely recognized as an intrinsic property of crystals, its physics still remains ambiguous. Recently, Kranert et al. have presented a new formalism to explain the origin of phase difference theoretically. Here, we systematically conducted an experimental polar phonons in wurtzite crystals research, whose results strongly suggest that the phase difference should be predetermined in Raman tensor, rather than be treated as Raman tensor elements traditionally or as an intrinsic property. On the ground of pinpointing existing logical flaws in Raman tensor study, we provide a logically clear paradigm.

Intermodal Four Wave Mixing in Silicon waveguides

Stefano Signorini, mattia Mancinelli, Massimo Borghi, Martino Bernard, Mher Ghulinyan, Georg Pucker, and Lorenzo Pavesi

Doc ID: 319640 Received 06 Feb 2018; Accepted 10 May 2018; Posted 15 May 2018  View: PDF

Abstract: In this work, we report the modeling and the experimental demonstration of intermodal spontaneous as well as stimulated four wave mixing (FWM) in silicon waveguides. In intermodal FWM, the phase matching condition is achieved by exploiting the chromatic dispersion of the optical modes in a multimode waveguide. Since both the energy and the wavevectors have to be conserved in the FWM process, this leads to a wide tunability of the generated photon wavelength allowing to achieve a large spectral conversion. We measured several waveguides which differ by their widths and demonstrate large signal generation spanning from the pump wavelength (1550 nm) down to 1202 nm. A suited set-up evidences that the different waves propagated indeed on different order modes, which supports the modeling. Despite we observed a reduced efficiency with respect to intramodal FWM due to the decreased modal overlap, we were able to show a maximum spectral distance between the Signal and Idler of 979.6 nm, with a 1550 nm pump. Our measurements suggest the intermodal FWM as a viable mean for large wavelength conversion and heralded photon sources.

Integrated (de)multiplexer for OAM fiber communications

Zhenwei Xie, She Gao, Ting Lei, Shengfei Feng, Yan Zhang, Fan Li, Jianbo Zhang, Zhaohui Li, and Xiaocong Yuan

Doc ID: 321270 Received 01 Feb 2018; Accepted 09 May 2018; Posted 09 May 2018  View: PDF

Abstract: Quickly increasing data transfer loads requires an urgent revolution in current optical communications. Orbital angular momentum (OAM) multiplexing is a potential candidate with its ability to considerably enhance the capacity of communications. However, the lack of a compact, efficient, and integrated OAM (de)multiplexer prevents it from being widely applied. By attaching vortex gratings onto the facets of a few-mode fiber, we demonstrate one such integrated fiber-based OAM (de)multiplexer. A vortex grating fabricated on the fiber facet enables the direct multiplexing of OAM states at one port and the demultiplexing of OAM states at the other port. The measured bit error rate of the carrier signal after propagating through a 5-km few-mode fiber confirms the validity and effectiveness of the proposed approach. The scheme offers advantages in future high-capacity OAM communications based on optical fiber.

Surface-illuminated photon-trapping ultra-fast Ge-on-Si photodiodes with broadband high efficiency up to 1700nm

Hilal Cansizoglu, CESAR BARTOLO-PEREZ, Yang Gao, Ekaterina Ponizovskaya Devine, SOROUSH GHANDIPARSI, Kazim G. Polat, Hasina Mamtaz, Toshishige YAMADA, ALY F. ELREFAIE, Shih-Yuan Wang, and M. Saif Islam

Doc ID: 326327 Received 20 Mar 2018; Accepted 09 May 2018; Posted 09 May 2018  View: PDF

Abstract: In this paper, high speed surface-illuminated Ge-on-Si pin photodiodes with a broadband high efficiency are demonstrated. With photon-trapping microholes features, the external quantum efficiency (EQE) of the Ge-on-Si pin diode is >80% at 1300 nm and 73% at 1550 nm with only 2 µm thick intrinsic Ge layer, showing much improvement compared to the one without microholes. More than three folds of EQE improvement is also observed at longer wavelength range beyond 1550 nm. These results make the microholes enabled Ge-on-Si photodiodes promising to cover both existing C and L bands, and a new data transmission window (1620 nm-1700 nm) that can be used to enhance the capacity of conventional standard single mode fiber (SSMF) cables. They have potentials for many applications such as inter/intra -data centers, passive optical networks (PON), metro and long haul dense wavelength division multiplexing (DWDM) systems, eye safety laser radar (LIDAR) systems, and quantum communications. The CMOS and BiCMOS monolithic integration compatibility of this work is also attractive for Ge CMOS and near-infrared sensing and communication integration.

Plasmonically induced transparency in double-layered graphene nanoribbons

Sheng-Xuan Xia, Xiang Zhai, Lingling Wang, and Shuangchun Wen

Doc ID: 320509 Received 24 Jan 2018; Accepted 08 May 2018; Posted 09 May 2018  View: PDF

Abstract: To achieve plasmonically induced transparency (PIT), general near-field coupled plasmonic systems rely solely on one-way bright-dark mode couplings. However, the realization of such well-designed devices is quite challenging, mainly due to their significant dependence on the choice of polarization direction. In this paper, we take advantage of surface plasmons supported by two crossed layers of graphene nanoribbons (GNRs) to achieve dynamically tunable PIT effects, where every GNR acts as both the bright and dark mode simultaneously. Specifically, the proposed PIT effect can result from either one-way bright-dark mode interactions or bidirectional bright-bright and bright-dark mode hybridized couplings, when the polarization is perpendicular/parallel or at an angle to GNRs, respectively. Additionally, homogeneous ribbon widths lead to a polarization-insensitive single-window PIT effect, while an inhomogeneous system produces a polarization-dependent double-window PIT effect. Finally, we examine the proposed technique by using the combined plasmon wave functions (PWFs) and the transfer matrix method (TMM), finding excellent agreement between the analytical and numerical results. The concepts developed can grant physical insight into PIT coupling mechanisms and facilitate the applicability and versatility of PIT-based sensing platforms and other active devices.

Experimental Demonstration of Dissipative Sensing in a Self-Interference Microring Resonator

Shuai Wan, Rui Niu, Hongliang Ren, Changling Zou, Guang-can Guo, and Chunhua Dong

Doc ID: 327375 Received 02 Apr 2018; Accepted 30 Apr 2018; Posted 03 May 2018  View: PDF

Abstract: The dissipative sensing based on a self-interference microring resonator composed of a microring resonator and a U-shaped feedback waveguide is demonstrated experimentally. Instead of a frequency shift induced by the phase shift of the waveguide or the microcavity, the dissipative sensing converts the phase shift to the effective external coupling rate, which leads to the change oflinewidth of the optical resonance and the extinction ratio in the transmission spectrum. In our experiment, the power dissipated from a microheater on the the feedback waveguide is detected by the dissipative sensing mechanism, and the sensitivity of our device can achieve 0:22 dB=mW. This dissipative sensing mechanism provides a promising candidate for microcavity sensing applicationsimmune to the frequency noise of the lasers.

Athermal 4-channel (de-)multiplexer in silicon nitride fabricated at low temperature

shiqi tao, Qingzhong Huang, liangqiu zhu, Jun Liu, Yinglu Zhang, ying huang, Yi Wang, and Jinsong Xia

Doc ID: 321216 Received 01 Feb 2018; Accepted 29 Apr 2018; Posted 03 May 2018  View: PDF

Abstract: We have designed and realized an athermal 4-channel wavelength (de-)multiplexer in silicon nitride (SiN). Minimized thermal sensitivity is achieved in a wide wavelength range by using wide and narrow waveguides with low and different thermal-optic coefficients in the two arms of Mach–Zehnder interferometers (MZIs). The SiN core layer and SiO2 cladding layers are all deposited by low-temperature plasma-enhanced chemical vapor deposition process. The fabricated MZI filter exhibits a thermal sensitivity within ±2.0 pm/°C in a wavelength range of 55 nm near 1300 nm. Then, an athermal (de-)multiplexer based on cascaded MZIs has been demonstrated with a crosstalk ≤-22 dB and a thermal sensitivity <4.8 pm/°C for all the four channels, reduced by 77% compared to a conventional SiN (de-)multiplexer. Owing to the passive operation and compatibility with CMOS back-end process, our devices have potential applications in 3-D integration of photonics and electronics.

Multi-wavelength sampled Bragg grating quantum cascade laser arrays

Xuefeng Jia, lijun wang, Ning Zhuo, jinchuan zhang, Shenqiang Zhai, Junqi Liu, Shuman Liu, Liu Fengqi, and Zhanguo Wang

Doc ID: 322578 Received 07 Feb 2018; Accepted 28 Apr 2018; Posted 03 May 2018  View: PDF

Abstract: Multi-wavelength sampled Bragg grating (SBG) quantum cascade laser array operating between 7.317 μm and 7.85 μm is reported. The sampling grating structure, which can be analyzed as a conventional grating multiplied by a sampling function, is fabricated by holographic exposure combined with the optical photolithography. The sampling grating period was varied from 8 to 32 μm and different sampling order (-1st, -2nd and -3rd order) modes were achieved. We propose that higher order modes with optimized duty cycles can be used to take full advantage of the gain curve and improve the wavelength coverage of the SBG array, which will be beneficial to many applications.

Ultra-compact dual mode waveguide crossing based on subwavelength multimode-interference couplers

Weijie Chang, Luluzi Lu, Xinshu Ren, Dongyu Li, Zepeng Pan, Mengfan Cheng, Deming Liu, and Minming Zhang

Doc ID: 322783 Received 08 Feb 2018; Accepted 27 Apr 2018; Posted 27 Apr 2018  View: PDF

Abstract: We propose and experimentally demonstrate a novel ultra-compact dual waveguide crossing based on subwavelength multimode-interference couplers for densely integrated on-chip mode-division multiplexing system. By engineering lateral-cladding material index and manipulating phase profiles of light at the nanoscale using inverse design method, subwavelength structure could theoretically realize identical beat length for both TE₀ and TE₁, which can reduce the scale of the device greatly. The fabricated device occupied a footprint of only 4.8 x 4.8 µm². The measured insertion loss and crosstalk were less than 0.6 dB and -24 dB from 1530 nm to 1590 nm for both TE₀ mode and TE₁ mode, respectively. Furthermore, our scheme could be also expanded to design waveguide crossing supporting more modes.

Parametric Amplification of Rydberg Six- and Eight-Wave Mixing Processes

Ji Guo, Zhaoyang Zhang, Bingling Gu, Ling Hao, Gaoguo Yang, Kun Wang, and Yanpeng Zhang

Doc ID: 324899 Received 26 Feb 2018; Accepted 26 Apr 2018; Posted 27 Apr 2018  View: PDF

Abstract: We study the parametric amplification of electromagnetically induced transparency assisted Rydberg six- and eight-wave mixing signals through a cascaded nonlinear optical process in a hot rubidium atomic ensemble both theoretically and experimentally. The shift of the resonant frequency (induced by the Rydberg-Rydberg interaction) of parametrically amplified six-wave mixing signal is observed. Moreover, the interplays between the dressing effects and Rydberg-Rydberg interactions in parametrically amplified multi-wave mixing signals are investigated. Such linearly amplified Rydberg multi-wave mixing processes with multi-channel nature can antagonize the suppression caused by Rydberg-Rydberg interaction and dressing effect.

Nonlinear Optical Performance of Few-layer MoSe₂ as a Slow-saturable Absorber

Gaozhong Wang, Guangxing Liang, Aidan Baker-Murray, Kangpeng Wang, Jing Jing Wang, Xiaoyan Zhang, Daniel Bennett, Jing-Ting Luo, Jun Wang, Ping Fan, and Werner Blau

Doc ID: 325979 Received 14 Mar 2018; Accepted 26 Apr 2018; Posted 27 Apr 2018  View: PDF

Abstract: Two dimensional transient-metal dichalcogenides (TMDC) are considered promising materials for next generation photonics and nano-optical devices. Although many previous reports have showed saturable absorption of molybdenum selenide (MoSe₂), these nonlinear optical (NLO) properties of MoSe₂ were measured in separate works and different conditions with their hot-carrier relaxations. Here, we conducted a series coherent studies on NLO properties of few-layered molybdenum selenide (MoSe₂) via open-aperture Z-scan and degenerate pump-probe techniques. These measurements were taken to test the materials capabilities as a slow-saturable absorber. A slow-absorber model was employed to analyze the NLO measurements and the results show that the NLO modulation depth was modeled to be 7.4% and 15.1% for the linear absorption of 5.22 1/cm and 6.51 1/cm respectively. The corresponding saturated intensities were modeled to be 39.37 and 4.75 MW/cm² respectively. The excitation carrier recovery time of few-layer MoSe₂ was measured by degenerate pump-probe techniques to be ~ 220 ps. These nonlinear optical performances make it a promising slow-saturable absorber for passive mode-locking in femtosecond lasers.

Watt-level and spectrally flat mid-infrared supercontinuum in fluoroindate fibers

Francis Theberge, nancy bérubé, Samuel Poulain, Solenn Cozic, Louis-Rafaël Robichaud, Martin Bernier, and Real Vallee

Doc ID: 322969 Received 12 Feb 2018; Accepted 17 Apr 2018; Posted 19 Apr 2018  View: PDF

Abstract: We report on infrared supercontinuum (SC) generation in step-index fluoroindate based fiber by using an all-fiber laser source. In comparison to widely used ZBLAN fibers for high-power mid-infrared (MIR) SC generation, fluoroindate fibers have multiphoton absorption edges at significantly longer wavelengths and can sustain similar power densities. Recent development highlighted in the present study allowed the production of fluoroindate fibers with MIR background loss of 2 dB/km, which is similar or even better than for ZBLAN fibers. By using an all-fiber picosecond laser source based on an erbium amplifier followed by a thulium power amplifier, we demonstrate the generation of 1.0 W infrared SC spanning over 2.25 octaves from 1 μm to 5 μm. The generated MIR SC also exhibits high spectral flatness with a 0.6 dB spectral bandwidth from 1.91 μm to 4.77 μm and an average power 2 orders of magnitude greater than in previous demonstrations with a similar spectral distribution.

Ultraflat, Broadband and Highly Coherent Supercontinuum Generation in All-solid Microstructured Optical Fibers with All-normal Dispersion

Chunlei Huang, Meisong Liao, wanjun bi, Xia Li, Lili Hu, Long Zhang, Longfei Wang, Guanshi Qin, Tianfeng Xue, Danping Chen, and Weiqing Gao

Doc ID: 320692 Received 26 Jan 2018; Accepted 14 Apr 2018; Posted 17 Apr 2018  View: PDF

Abstract: High flatness, wide bandwidth and high coherence properties of supercontinuum (SC) generation in fibers are crucial in many applications. It is challenging to achieve SC spectra in the combination of the properties since special dispersion profiles are required, especially when the pump pulses with duration over 100 fs are employed. We propose an all-solid microstructured fiber composed only of hexagonal glass elements. The optimized fiber possesses an ultraflat all-normal dispersion profile covering a wide wavelength interval of approximately 1.55 μm. An SC spectrum spanning from 1030 to 2030 nm (corresponding to nearly one octave) with flatness <3 dB is numerically generated in the fiber with 200 fs pump pulses at 1.55 μm. The results indicate that the broadband ultraflat SC sources can be all-fiber and miniaturized due to commercially achievable 200-fs fiber lasers. Moreover, the SC pulses feature high coherence and a single pulse in the time domain, which can be compressed to 13.9-fs pulses with high quality even for simple linear chirp compensation. The Fourier-limited pulse duration of the spectrum is 2.16 fs, corresponding to only 0.42 optical cycles.

Enhancement of stimulated emission by a metallic optofluidic resonator

Xianfeng Chen, Bei Jiang, and Hailang Dai

Doc ID: 318922 Received 04 Jan 2018; Accepted 08 Apr 2018; Posted 12 Apr 2018  View: PDF

Abstract: Stimulated emission can be controlled by material molecular energy band and intensity of pump laser, which can provide some of population inversion and promote ground electron transition, respectively. We use a metallic optofluidic resonator to enhance stimulated emission intensity. The quality factor Q and the spontaneous emission coupling factor β of the metallic optofluidic resonator are discussed in detail to explain the enhancement mechanism. Experimental data demonstrate that the operated emission from Rhodamin 6G solution can be observed due to the enhancement of stimulated emission from the optofluidic resonator.

Active /Passive Q-switching operation of 2μm Tm,Ho:YAP laser with acousto-optical Q-switch / MoS2 saturable absorber mirror

Linjun Li, xining yang, Long Zhou, Wenqiang Xie, Yunlong Wang, yingjie shen, Yuqiang Yang, Wenlong Yang, Wei Wang, Zhiwei Lv, Xiaoming Duan, and minghua Chen

Doc ID: 324784 Received 26 Feb 2018; Accepted 06 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: Active /passive Q-switching operation of 2 μm a-cut Tm,Ho:YAP laser was experimentally demonstrated with an acousto-optical (AO) Q-switch / MoS2 saturable absorber (SA) mirror. The active Q-switch laser was operated, for the first time, with an average output power of 12.3 W and a maximum pulse energy of 10.3 mJ. The passive Q-switch laser was also the first acquired with an average output power of 3.3 W and per pulse energy of .31 μJ, and the beam quality factors of M_x^2=1.06 and M_y^2=1.06 were measured at the average output power of 2 W.

Backcoupling manipulation in silicon ring resonators

ang li and Wim Bogaerts

Doc ID: 324866 Received 26 Feb 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: In this paper we theoretically propose and experimentally demonstrate the manipulation of a novel degree of freedom in ring resonator, which is the coupling from the clockwise input to the counterclockwise propagating mode (and vice versa). We name this mechanism backcoupling, in contrast with the normal forward coupling of a directional coupler. It is well known that internal reflections will cause peak splitting to a ring resonator. Our previous research demonstrated that the peak asymmetry will be strongly influenced by the backcoupling. Thus it's worthy manipulating the backcoupling in order to get full control of a split resonance for the benefit of various resonance splitting based applications. While it's very difficult to directly manipulate the backcoupling of a conventional directional coupler, here we design a circuit explicitly for manipulating the backcoupling. It can be potentially developed for applications like single sideband filter, resonance splitting elimination, Fano resonance and ultra high Q and Finesse.

Electric field tunable strong transverse light current from nanoparticles embedded in liquid crystal

Xiangdong Zhang and Jinhua Li

Doc ID: 325675 Received 08 Mar 2018; Accepted 05 Apr 2018; Posted 06 Apr 2018  View: PDF

Abstract: We present an exact solution to the problem of electromagnetic scattering by nanosphere clusters embedded in a liquid crystal cell based on the Mie theory. The dependence of the scattering property on the structure parameters has been investigated in detail. It is shown that strong transverse light currents in the optical frequency can be obtained from these complex structures. Furthermore, we find that sign reversal of the transverse light current can also be realized by changing frequency and voltage. The physical origins for these phenomena have been analyzed. The transverse light current for subwavelength nanoscale dimensions is of practical significance. Thus, the applications of these phenomena to optical devices are anticipated.

Optical vortex copier and regenerator in the Fourier domain

Xiaodong Qiu, Fangshu Li, Haigang Liu, Xianfeng Chen, and Lixiang Chen

Doc ID: 319681 Received 12 Jan 2018; Accepted 05 Apr 2018; Posted 12 Apr 2018  View: PDF

Abstract: The generation and manipulation of optical vortices are of fundamental importance in a variety of promising applications. Here we develop a nonlinear optical paradigm to implement self- and cross-convolution of optical vortex arrays, demonstrating the features of vortex copier and regenerator. We use a phase-only spatial light modulator (SLM) to prepare the 1064nm invisible fundamental light to carry special optical vortex arrays, and use a Potassium titanyl phosphate (KTP) crystal to perform type II second harmonic generation (SHG) in the Fourier domain to achieve 532nm visible structured vortices. Based on pure cross-convolution, we succeed in copying arbitrary-order single vortices as well as their superposition states onto a prearranged array of fundamental Gaussian spots. Also, based on simultaneous effect of self- and cross-convolutions, we can expand the initial vortex lattices to regenerate more vortices carrying various higher topological charges. Our present method of realizing optical vortex copier and regenerator could find direct applications in optical manipulation, optical imaging, optical communication, and quantum information processing with structured vortex arrays.

Robust cavity soliton formation with hybrid dispersion

Jing Wang, Yuhao Guo, Henan Liu, Lionel Kimerling, Jurgen Michel, Anuradha Agarwal, Guifang Li, and Lin Zhang

Doc ID: 320234 Received 22 Jan 2018; Accepted 03 Apr 2018; Posted 18 Apr 2018  View: PDF

Abstract: Microresonator-based Kerr frequency combs have attracted a great deal of attention in recent years, in which mode-locking of the generated combs is associated with bright or dark cavity soliton formation. In this paper, we show that, different from solitons propagating along a waveguide, cavity solitons can be robustly formed under a unique dispersion profile with four zero-dispersion wavelengths. More importantly, such a dispersion profile exhibits much smaller average dispersion, thus making it possible to greatly reduce the pump power by 5 to 6 times.

Spatially-resolved measurement of plasmon dispersion using Fourier-plane spectral imaging

Amir Ohad, Katherine Akulov, Eran Granot, Uri Rossman, Fernando Patolsky, and Tal Schwartz

Doc ID: 308772 Received 10 Oct 2017; Accepted 02 Apr 2018; Posted 04 Apr 2018  View: PDF

Abstract: We show that Fourier-plane imaging in conjunction with the Kretschmann-Raether configuration can be used for measuring polariton dispersion with spatial discrimination of the sample, over the whole visible spectral range. We demonstrate the functionality of our design on several architectures, including plasmonic waveguides, and show that our new design enables the measurement of plasmonic dispersion curves of structures as small as 3μm in a single shot.

Ultra-compact broadband polarization beam splitter with strong expansibility

Jie Huang, Yang Junbo, Dingbo Chen, xin He, Yunxin Han, JingJing Zhang, and Zhaojian Zhang

Doc ID: 317901 Received 18 Dec 2017; Accepted 02 Apr 2018; Posted 04 Apr 2018  View: PDF

Abstract: Based on the traditional directional coupler, we proposed a new scheme to design on-chip polarization beam splitters by using inverse design method. In our scheme, the coupling area of the designed devices are only 0.48 μm × 6.4 μm. By manipulating the refractive index of the coupling region, the devices can work in C-band, L-band, O-band or any other communication bands. Different from conventional design methods, which need to adjust the design parameters artificially, if the initial conditions are determined, the proposed scheme can automatically design devices according to requirements. The simulation results show that the insertion losses of the designed polarization beam splitters can be less than 0.4 dB (0.35 dB) for TE (TM) at the wavelength of 1310 nm, 1550 nm and 1600 nm, and the extinction ratios are larger than 19.9 dB for TE and TM mode at all three wavelengths. Besides, the extinction ratios of both polarization states are more than 14.5 dB within the wavelength range of 1286 nm-1364 nm, 1497 nm-1568 nm and 1553 nm-1634 nm. At the same time, the insertion losses are smaller than 0.46 dB.

Generation rate scaling: the quality factor optimization of micro-ring resonator for photon-pair sources

Kai Guo, Xiaodong Shi, Xiaolin Wang, Junbo Yang, Yunhong Ding, Haiyan Ou, and Yijun Zhao

Doc ID: 320070 Received 17 Jan 2018; Accepted 29 Mar 2018; Posted 04 Apr 2018  View: PDF

Abstract: To achieve photon-pair generation scaling, we optimize the quality factor of micro-ring resonators for efficient continuous-wave-pumped spontaneous four-wave mixing. Numerical studies indicate that high intrinsic quality factor makes possible high pair rate and pair brightness, of which the maximums take place in the over-coupling and critical-coupling conditions, respectively. We fabricate six all-pass type micro-ring resonator samples on a silicon-on-insulator chip involving gap width as the only degree of freedom. The pair rate, pair brightness and coincidence rate of all the samples are characterized, which are then compared to the modified simulations by taking the detector saturation and nonlinear loss into account. Being experimentally validated for the first time to our best knowledge, this work explicitly demonstrates that reducing the round-trip loss in ring cavity and designing the corresponding optimized gap width are more effective to generate high-rate or high-brightness photon pairs than the conventional strategy of simply increasing the quality factor.

Numerical modeling of Linear Photonic System for Accurate and Efficient Time-Domain Simulations

Yinghao Ye, Domenico Spina, Yufei Xing, Wim Bogaerts, and Tom Dhaene

Doc ID: 312773 Received 21 Nov 2017; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: In this paper, a novel modeling and simulation method for general linear, time-invariant, passive photonic devices and circuits is proposed. This technique, starting from the scattering parameters of the photonic system under study, builds a lowpass equivalent state-space model which splits the optical carrier frequency and operates at baseband, thereby significantly reducing the modeling and simulation complexity without losing accuracy. Indeed, it is possible to analytically reconstruct the port signals of the photonic system under study starting from the time-domain simulation of the corresponding lowpass equivalent model. However, such equivalent models are complex-valued systems and, in this scenario, the conventional passivity constraints are not applicable anymore. Hence, the passivity constraints for scattering parameters and state-space models of lowpass equivalent systems are presented, which are essential for time-domain simulations. Three suitable examples demonstrate the feasibility, accuracy and efficiency of the proposed method.

Extraordinary characteristics for 1D PT-symmetric periodic ring optical waveguide networks

Yan Zhi, Xiangbo Yang, Jiaye Wu, Shiping Du, Peichao Cao, Dongmei Deng, and Chengyi Liu

Doc ID: 318894 Received 19 Jan 2018; Accepted 29 Mar 2018; Posted 30 Mar 2018  View: PDF

Abstract: In this paper, we design a one-dimensional (1D) PT-symmetric periodic ring optical waveguide network (PTSPROWN) and investigate its extraordinary optical characteristics. It is found that quite different from traditional vacuum/dielectric optical waveguide networks, 1D PTSPROWN can not produce photonic ordinary propagation mode (OPM), but can generate simultaneously two kinds of photonic non-propagation modes, attenuation propagation mode (APM) and gain propagation mode (GPM). It creates neither passband nor stopband and then possesses no photonic band structure. This makes 1D PTSPROWN possess richer spontaneous PT-symmetric breaking points and appear interesting extremum spontaneous PT-symmetric breaking points, where electromagnetic (EM) waves can create ultrastrong extraordinary transmission, reflection, and localization and the maximum can arrive at 6.6556*10^{12} and are more than seven orders of magnitude larger than the results reported previously. 1D PTSPROWN may possess potential in designing high efficiency optical energy saver devices, optical amplifiers, optical switches with ultrahigh monochromatity, and so on.

Single-Mode VCSEL for Pre-Emphasis PAM-4 transmission up to 64 Gbit/s over 100-300 m in OM4 MMF

Hsuan-Yun Kao, Cheng-Ting Tsai, Shan-Fong Leong, Chun-Yen Peng, Yu-Chieh Chi, Huai-Yung Wang, Hao-chung Kuo, Chao-Hsin Wu, Wood-Hi Cheng, and Gong-Ru Lin

Doc ID: 312994 Received 08 Nov 2017; Accepted 17 Dec 2017; Posted 22 Dec 2017  View: PDF

Abstract: A single-mode vertical cavity surface emitting laser (VCSEL) based data transmission is demonstrated, which enables 4-level pulse amplitude modulation (PAM-4) at 64 Gbit/s over 100-300 m in the OM4 multi-mode fiber (MMF). By optimizing the bias of the single-mode VCSEL with a differential resistance of 159 ohm the related electrical return loss of -5.7 dB is evaluated to provide an analog modulation bandwidth of 18.9 GHz. After pre-emphasizing waveform of the PAM-4 format, the PAM-4 data stream can be successfully delivered by the single-mode VCSEL at 64 Gbit/s under back-to-back and 100-m-long OM4 MMF conditions. Lengthening the transmission distance worsens the signal-to-noise ratio of PAM-4 data to the FEC criterion, as the waveform pre-emphasis of the PAM-4 data stream inevitably induces spectral power compensation from-low to high frequencies. Therefore, increasing the OM4 MMF distance from 200 to 300 m significantly reduces the peak-to-peak amplitude of data to suppress the SNR and reduce the transmission capacity from 52 to 48 Gbit/s.

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