Li Yan

University of Maryland, Baltimore County, Baltimore, MD, United States

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Publications (34)34.16 Total impact

  • Li Yan · Lijun Ma · Xiao Tang
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    ABSTRACT: We propose a new method to narrow the linewidth of photon pairs generated from spontaneous parametric down conversion (SPDC). The single structure device incorporates an internal Bragg grating onto a nonlinear optical waveguide. We study theoretically the spectral characteristics of SPDC under two Bragg grating structures. We show that using the Bragg grating with a midway pi- phase shifter is a promising way to implement narrow-line (~GHz to sub-GHz) entangled photon sources.
    Proceedings of SPIE - The International Society for Optical Engineering 08/2010; DOI:10.1117/12.859269 · 0.20 Impact Factor
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    Li Yan · Lijun Ma · Xiao Tang
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    ABSTRACT: We propose a new method to narrow the line width of entangled photons generated from spontaneous parametric downconversion ( SPDC). The single structure device incorporates an internal Bragg grating onto a nonlinear optical waveguide. We study theoretically the spectral characteristics of SPDC under two Bragg grating structures. We show that using the Bragg grating with a midway pi-phase shifter, it is a promising way to generate narrow-line (similar to GHz to sub-GHz) entangled photons. (C) 2010 Optical Society of America
    Optics Express 03/2010; 18(6):5957-63. DOI:10.1364/OE.18.005957 · 3.49 Impact Factor
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    Li Yan · Lijun Ma · Xiao Tang
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    ABSTRACT: We propose a new method to narrow the linewidth of entangled photons generated from spontaneous parametric down conversion (SPDC). An internal Bragg grating is incorporated onto a nonlinear optical crystal waveguide. We study theoretically the spectral characteristics of SPDC under two Bragg grating structures. We show that using the Bragg grating with a midway pi-phase shifter, it is a promising way to generate narrow-line entangled photons. Comment: 7 pages, 3 figures
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    ABSTRACT: We systematically investigate the combined effect on the system performance in an optical fiber communication system of a signal that is depolarized due to polarization-mode dispersion (PMD) and noise that is partially polarized due to polarization-dependent loss. We derive a formula for the variance of the electric current of the signal due to the signal-noise beating between a depolarized signal and partially polarized noise. We validate this theoretical formula by comparing the Q -factor calculated using the theory to results obtained from Monte Carlo simulations and experiments. We show that the system performance strongly depends on the power-splitting ratio, the degree of polarization of the noise, and the angle between the states of polarization of the signal and the polarized part of the noise. Although the theoretical formula is derived assuming that the optical fiber only has first-order PMD, we show that for arbitrary fiber, this formula still produces a reliable estimate of the Q-factor provided that the second-order PMD is on the order of 300 ps<sup>2</sup> or less.
    Journal of Lightwave Technology 10/2009; 27(18-27):4124 - 4315. DOI:10.1109/JLT.2009.2022510 · 2.86 Impact Factor
  • Li Yan · Song Han
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    ABSTRACT: Passive mode locking of inhomogeneously broadened lasers is studied in three typical regimes: pure self-amplitude modulation (SAM) mode locking, soliton mode locking, and mode locking in the presence of self-phase modulation (SPM) and positive group-delay dispersion (GDD). When the mode-locking strength becomes weak and/or the GDD is large, the lockable spectral width reduces and mode locking becomes unstable, which is a common and unique feature for broadband inhomogeneously broadened lasers. Mode locking by the pure SAM is essentially a phase-locking process. The soliton mode locking best resists the impact of insufficient gain filtering, while mode locking in the presence of strong SPM and positive GDD is the weakest, and a certain amount of gain filtering (narrowing) is necessary for stable mode locking. The scaling relations of mode-locking characteristics with the gain linewidth, GDD, and nonlinearities, and the influence of the degree of inhomogeneity of the gain medium are examined. A linearized saturable absorber may not be able to mode lock a strongly inhomogeneously broadened laser, and a minimum unsaturated absorber loss is required for stable mode locking in most situations.
    Journal of the Optical Society of America B 08/2007; 24(9):2108-2118. DOI:10.1364/JOSAB.24.002108 · 1.81 Impact Factor
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    Li Yan · Song Han
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    ABSTRACT: Passive mode-locking of inhomogeneously broadened lasers is studied in three regimes: pure SAM, soliton mode-locking, and with SPM and positive GDD. Scaling features of mode-locking characteristics with the gain linewidth, dispersion, and nonlinearities are presented.
    Quantum Electronics and Laser Science Conference, 2007. QELS '07; 06/2007
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    Qiang Wang · Li Yan
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    ABSTRACT: Mutual injection-locking of two individual lasers through an external combining section was theoretically studied. We found that larger lockable range can be obtained with lower Q-factors for individual lasers.
  • Jiping Wen · Li Yan · Gary M. Carter
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    ABSTRACT: We show that, in a typical terrestrial WDM system, the intra-channel nonlinearity-induced Q fluctuation is comparable to that due to PDL alone, and the inter-channel nonlinearity dominates Q fluctuations at narrow channel spacings.
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    ABSTRACT: Due to the temporal drift of the fiber birefringence in an optical fiber transmission system, the polarization mode dispersion (PMD) effects measured in a time window can be quite different for different time windows of the same duration. Every 10 s for 10 days, the accumulated differential group delay (DGD) was repeatedly measured at 5000 km in a 107-km recirculating loop with loop-synchronous polarization scrambling. In each DGD measurement, the polarization dispersion vector of the 107-km-long fiber was also measured. To model the measured temporal variation of the DGD, two different perturbation algorithms were used to construct random walks through the configuration space of birefringent fibers, where each fiber realization is determined by the standard coarse-step method. With these simulation models, the statistical properties of the spread of the DGD samples over a finite time period were reproduced.
    Journal of Lightwave Technology 04/2006; 24(3):1165- 1175. DOI:10.1109/JLT.2005.863276 · 2.86 Impact Factor
  • Qiang Wang · Li Yan · P.-T. Ho
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    ABSTRACT: The gain linewidth limits the scalability of combining multiple lasers by mutual injection locking. We propose a method to improve the scalability with a simple active stabilization scheme, and present results with Nd: YVO4 lasers
    Conference Proceedings - Lasers and Electro-Optics Society Annual Meeting-LEOS 01/2006; DOI:10.1109/LEOS.2006.278964
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    ABSTRACT: We studied mutual injection locking of two individual continuous-wave $hbox Nd:hbox YVO_4$ lasers that were coupled through an external section. The two lasers lased at the same wavelength with a stable output power and interference fringes with high contrast ratio in the combined beam profile showed good mutual coherence of the two lasers. Mutual injection locking was also achieved without active stabilization for individual lasers with a large cavity length difference and low $Q$ -factors. The calculated combined output power under symmetric pumping agreed with the experimental results. Even when output couplings of individual lasers are not optimized, the output coupling of the combining section can be optimized to make the extracted power very close to the sum of maximum powers that can be extracted from individual free running lasers under optimal output coupling.
    IEEE Journal of Quantum Electronics 10/2005; 41(9-41):1168 - 1175. DOI:10.1109/JQE.2005.852993 · 2.11 Impact Factor
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    ABSTRACT: We investigate experimentally and theoretically the statistics of optical signal-to-noise ratio (OSNR) and Q-factor after 1800 km of propagation with three channel spacings in a typical terrestrial wavelength-division-multiplexing (WDM) system with a fixed loop polarization-dependent loss (PDL) level of 0.75 dB. Comparisons between measured and simulated results show that fiber drift contributes significantly to the OSNR and Q fluctuations, and decreasing channel spacing reduces the PDL-induced performance fluctuations, but increases the interchannel crosstalk-induced performance fluctuations, especially at the 50-GHz channel spacing. The combination of these factors leads to comparable performance statistics with these channel spacings.
    IEEE Photonics Technology Letters 07/2005; DOI:10.1109/LPT.2005.846573 · 2.18 Impact Factor
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    ABSTRACT: We demonstrated mutual injection locking and coherent beam combining of three individual Nd:YVO4 laser modules. A beam splitter couples three lasers as well as combines their outputs. In the free running state, the divergence of combined beams is large. Under mutual injection locking, the divergence of the combined beams becomes substantially smaller than that in the free-running state and is as small as that of the individual laser beam. Mutual injection locking was also realized without active stabilization with large individual laser cavity length difference and low individual laser Q-factor.
    Proceedings of SPIE - The International Society for Optical Engineering 06/2005; DOI:10.1117/12.604024 · 0.20 Impact Factor
  • Xiao Lin · Li Yan
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    ABSTRACT: We report a multichannel optical signal-to-noise ratio (OSNR) monitoring method using the integrated planar lightwave circuit and fast Fourier transform techniques with a single detector. The OSNR of four-channel wavelength-division-multiplexing signals can be monitored for a dynamic range of 20 dB with an accuracy of ┬▒1 dB. This method can further allow one to suppress the optical crosstalk in accordance with the requirements of OSNR accuracy and dynamic range.
    IEEE Photonics Technology Letters 01/2005; DOI:10.1109/LPT.2004.836755 · 2.18 Impact Factor
  • Hai Xu · Hua Jiao · Li Yan · G.M. Carter
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    ABSTRACT: Using the Jones matrix eigenanalysis and Poincare┬┤ arc methods, we measured the differential group delay (DGD) in a recirculating loop for arbitrary fiber realizations and for different round trips. The measurement uncertainty was less than 2.0 ps in most cases. With this capability, we measured the DGD distribution with and without loop-synchronous polarization scrambling. We found that the DGD distribution can be influenced by the slow drift of fiber realization in the loop.
    IEEE Photonics Technology Letters 08/2004; 16(7-16):1691 - 1693. DOI:10.1109/LPT.2004.829523 · 2.18 Impact Factor
  • Xiao Lin · Yu Sun · Gary M. Carter · Li Yan
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    ABSTRACT: We demonstrate an on-chip power monitoring method based on a channelized dynamic gain equalizer filter. Multichannel signal powers can be monitored simultaneously by fast Fourier transform, while phase modulation does not induce penalty on data.
    Integrated Photonics Research; 06/2004
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    ABSTRACT: We compare five methods for measuring the DGD in a long-haul system. The commonly-used JME method is insensitive to PDL, but sensitive to Stokes noise. The other methods are more sensitive to PDL.
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    ABSTRACT: Not Available
    Optical Fiber Measurements, 2004. Technical Digest: Symposium on; 02/2004
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    Hai Xu · J. Zweck · Li Yan · C.R. Menyuk · G.M. Carter
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    ABSTRACT: Using a recirculating loop, we measured nonlinearly induced timing jitter in a terrestrial wavelength-division-multiplexed system at different transmission distances with different amounts of precompensation. Within each 600-GHz subband, we achieved error-free transmission using the same amount of precompensation for all channels at all distances up to 5000 km.
    IEEE Photonics Technology Letters 02/2004; DOI:10.1109/LPT.2003.820470 · 2.18 Impact Factor
  • Xiao Lin · Li Yan · R. Madabhushi
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    ABSTRACT: We report a multiwavelength simultaneous monitoring method using the integrated planar lightwave circuit and fast Fourier transform techniques with a single detector. Accuracies of wavelength and power measurements are within /spl plusmn/ 3 GHz and /spl plusmn/ 0.5 dB, both in a 13-dB dynamic range of optical power, respectively.
    IEEE Photonics Technology Letters 01/2004; 15(12-15):1752 - 1754. DOI:10.1109/LPT.2003.819752 · 2.18 Impact Factor

Publication Stats

58 Citations
34.16 Total Impact Points

Institutions

  • 2003–2010
    • University of Maryland, Baltimore County
      • Department of Computer Science and Electrical Engineering
      Baltimore, MD, United States
  • 2001–2009
    • University of Maryland, Baltimore
      Baltimore, Maryland, United States
    • Loyola University Maryland
      Baltimore, Maryland, United States
  • 2002
    • Johns Hopkins University
      • Department of Electrical and Computer Engineering
      Baltimore, MD, United States