Diffraction and Gratings|6 Article(s)
Periodic structural defects in Bragg gratings and their application in multiwavelength devices
Rulei Xiao, Yuechun Shi, Renjia Guo, Ting Chen, Lijun Hao, and Xiangfei Chen
In this paper, we present the finding that periodic structural defects (PSDs) along a Bragg grating can shift the Bragg wavelength. This effect is theoretically analyzed and confirmed by numerical calculation. We find that the Bragg wavelength shift is determined by the defect size and the period of the defects. The Bragg wavelength can be well tuned by properly designing the PSDs, and this may provide an alternative method to fabricate grating-based multiwavelength devices, including optical filter arrays and laser arrays. In regards to wavelength precision, the proposed method has an advantage over the traditional methods, where the Bragg wavelengths are changed directly by changing the grating period. In addition, the proposed method can maintain grating strength when tuning the wavelength since only the period of defects is changed. This will be a benefit for devices such as arrays.
Photonics Research
  • Publication Date: Feb. 23, 2016
  • Vol.4 Issue, 2 02000035 (2016)
Long-period grating inscription on polymer functionalized optical microfibers and its applications in optical sensing
Z. Y. Xu, Y. H. Li, and L. J. Wang
We demonstrated long-period grating (LPG) inscription on polymer functionalized optical microfibers and its applications in optical sensing. Optical microfibers were functionalized with ultraviolet-sensitive polymethyl methacrylate jackets and, thus, LPGs could be inscribed on optical microfibers via point-by-point ultraviolet laser exposure. For a 2 mm long microfiber LPG (MLPG) inscribed on optical microfibers with a diameter of 5.4 μm, a resonant dip of 15 dB at 1377 nm was observed. This MLPG showed a high sensitivity of strain and axial force, i.e., 1.93 pm/μ and 1.15 pm/μN, respectively. Although the intrinsic temperature sensitivity of the LPGs is relatively low, i.e., 12.75 pm/°C, it can be increased to be 385.11 pm/°C by appropriate sealing. Benefiting from the small footprint and high sensitivity, MLPGs could have potential applications in optical sensing of strain, axial force, and temperature.
Photonics Research
  • Publication Date: Mar. 07, 2016
  • Vol.4 Issue, 2 02000045 (2016)
Optically induced atomic lattice with tunable near-field and far-field diffraction patterns
Feng Wen, Huapeng Ye, Xun Zhang, Wei Wang, Shuoke Li, Hongxing Wang, Yanpeng Zhang, and Cheng-wei Qiu
Conventional periodic structures usually have nontunable refractive indices and thus lead to immutable photonic bandgaps. A periodic structure created in an ultracold atoms ensemble by externally controlled light can overcome this disadvantage and enable lots of promising applications. Here, two novel types of optically induced square lattices, i.e., the amplitude and phase lattices, are proposed in an ultracold atoms ensemble by interfering four ordinary plane waves under different parameter conditions. We demonstrate that in the far-field regime, the atomic amplitude lattice with high transmissivity behaves similarly to an ideal pure sinusoidal amplitude lattice, whereas the atomic phase lattices capable of producing phase excursion across a weak probe beam along with high transmissivity remains equally ideal. Moreover, we identify that the quality of Talbot imaging about a phase lattice is greatly improved when compared with an amplitude lattice. Such an atomic lattice could find applications in all-optical switching at the few photons level and paves the way for imaging ultracold atoms or molecules both in the near-field and in the far-field with a nondestructive and lensless approach.
Photonics Research
  • Publication Date: Nov. 08, 2017
  • Vol.5 Issue, 6 06000676 (2017)
Improved optical enhancement using double-width plasmonic gratings with nanogaps
Ahmad A. Darweesh, Stephen J. Bauman, and Joseph B. Herzog
Photonics Research
  • Publication Date: Sep. 01, 2016
  • Vol.4 Issue, 5 05000173 (2016)
Optimal design of Er/Yb co-doped fiber amplifiers with an Yb-band fiber Bragg grating
Qun Han, Wenchuan Yan, Yunzhi Yao, Yaofei Chen, and Tiegen Liu
In this paper, Er/Yb co-doped fiber amplifiers (EYDFAs) with an Yb-band fiber Bragg grating (FBG) at the pump end to improve the performance of the amplifier is systematically studied. The influence of the reflectivity and center wavelength of the FBG along with the gain-fiber length on the performance of an EYDFA are numerically analyzed. The results show that the wavelength of the FBG has critical influence on the efficiency of the EYDFA, whereas the requirement to its reflectivity is relaxed. It is an effective and promising way to improve the efficiency of a high-power pumped EYDFA by introducing a suitable Yb-band FBG at the pump end. Based on the analysis of the underlying principles, suggestions for the practical design and possible further improvement strategies are also proposed.
Photonics Research
  • Publication Date: Mar. 11, 2016
  • Vol.4 Issue, 2 02000053 (2016)