HwaYaw Tam - Academia.edu (original) (raw)

Papers by HwaYaw Tam

Optics Express, 2019

Compared to glass walls with a positive curvature, those with a negative curvature have been prov... more Compared to glass walls with a positive curvature, those with a negative curvature have been proven to have stronger confinement of light. Therefore, we change the multi-layered air holes in a photonic crystal fiber into several negative curvature tubes. As a result, the confinement medium is shifted from a low-index cladding material into a special structure. The theoretical analysis shows that each vector eigenmode has a corresponding threshold value for the outer tube thickness. It means that we can confine the target modes and filter the unnecessary modes by shifting the outer tube thickness. After substantial investigation on this fiber, we obtain the appropriate values for each structural parameter and then fabricate this negative curvature ring-core fiber under the guidance of the simulation results. Firstly, we draw the central cane under vacuum condition, then stack the cane and six capillaries to form the preform, and finally draw the ring-core fiber by using vacuumization method. The fiber test experiment indicates that the fiber length should be at least 15 m∼20 m to form the donut facula, and the tested losses of OAM +1,1 , OAM +2,1 , OAM +3,1 , and OAM +4,1 are 0.30 dB/m, 0.36 dB/m, 0.37 dB/m, and 0.42 dB/m, respectively.

Asia Communications and Photonics Conference, 2012

A dual-core photonic crystal fiber (DC-PCF) sensor based on fiber Mach-Zehnder interferometer is ... more A dual-core photonic crystal fiber (DC-PCF) sensor based on fiber Mach-Zehnder interferometer is proposed and demonstrated for stress sensing with a sensitivity of 1.4 pm/με and hydraulic pressure sensing with a sensitivity of-41 pm/MPa.

Workshop on Specialty Optical Fibers and their Applications, 2013

We propose a new design of polarization-maintaining photonic crystal fiber for Sagnac interferome... more We propose a new design of polarization-maintaining photonic crystal fiber for Sagnac interferometric pressure sensing. Simulation demonstrates its pressure sensitivity is enhanced by over 20 times compared with existing sensors of the same type.

National Fiber Optic Engineers Conference, 2012

We experimentally demonstrated that the taper length of larger diameter microfibers can be contro... more We experimentally demonstrated that the taper length of larger diameter microfibers can be controlled to filter out the higher order modes of LP 0N to cladding mode to obtain a single reflection peak.

$Research paper thumbnail of In-line microfluidic integration of photonic crystal fibres as a highly sensitive refractometer$

Analyst, 2014

Please note that technical editing may introduce minor changes to the text and/or graphics, which... more Please note that technical editing may introduce minor changes to the text and/or graphics, which may alter content. The journal's standard Terms & Conditions and the Ethical guidelines still apply. In no event shall the Royal Society of Chemistry be held responsible for any errors or omissions in this Accepted Manuscript or any consequences arising from the use of any information it contains.

$Research paper thumbnail of In-line open-cavity Fabry-Perot interferometer formed by C-shaped fiber fortemperature-insensitive refractive index sensing$

Progress In Electromagnetics Research M, 2010

20th International Conference on Optical Fibre Sensors, 2009

We present an ultra-short distributed Bragg reflector fiber laser written in Er/Yb co-doped fiber... more We present an ultra-short distributed Bragg reflector fiber laser written in Er/Yb co-doped fiber. The entire laser is only 8.4 mm in length. The lasing threshold is less than 1 mW. The optical signal-to-noise ratio of the laser output is better than 70 dB. The laser emits two orthogonal polarization modes and generates a beat signal with signal-to-noise ratio of ~70 dB and 3-dB linewidth of ~3 kHz. The laser has longitude mode spacing comparable to the grating bandwidth. This obviates the possibility of mode hopping when the laser is subjected to any external perturbations.

Materials, 2014

A generic three-stage stack-and-draw method is demonstrated for the fabrication of complex-micros... more A generic three-stage stack-and-draw method is demonstrated for the fabrication of complex-microstructured optical fibers. We report the fabrication and characterization of a silica superlattice microstructured fiber with more than 800 rhomboidally arranged air-holes. A polarization-maintaining fiber with a birefringence of 8.5 × 10 −4 is demonstrated. The birefringent property of the fiber is found to be highly insensitive to external environmental effects, such as pressure.

$Research paper thumbnail of In-line microfluidic refractometer based on C-shaped fiber assisted photonic crystal fiber Sagnac interferometer$

Optics Letters, 2004

We report the development of photosensitive polymeric optical fibers for gratings. The fiber clad... more We report the development of photosensitive polymeric optical fibers for gratings. The fiber cladding is made of a copolymer of methyl methacrylate and butyl methacrylate, and its core is made of a copolymer of methyl methacrylate, ethyl methacrylate, and benzyl methacrylate (90͞4͞6 molar ratio) doped with trans-4stilbenemethanol. Ultraviolet absorption and photoinduced refractive-index change of the doped core system are presented, and its photosensitivity is demonstrated by fabrication of Bragg gratings in the core of the fiber by use of a pulse laser at 325 nm.

Optics Letters, 2003

A new type of mode recoupling in a Bragg grating pair, in which one of the gratings is written in... more A new type of mode recoupling in a Bragg grating pair, in which one of the gratings is written in the fiber cladding, is proposed to overcome limitations of concatenated long-period and fiber Bragg gratings reported earlier [Opt. Lett. 27, 1214 (2002)]. Its ref lection spectrum is similar to that of the previously reported concatenated grating structure; however, the ref lectivity can be much larger than the previous limitation of 50%. Furthermore, avoidance of the loss induced by a long-period grating makes such a Bragg grating pair more attractive for practical applications.

Optics Express, 2006

A novel and simple technique, based on nonlinear polarization rotation (NPR) effect, to generate ... more A novel and simple technique, based on nonlinear polarization rotation (NPR) effect, to generate stable multiwavelength oscillations in an erbium-doped fiber laser is proposed and successfully demonstrated. The NPR effect effectively induced intensity-and wavelength-dependent loss to alleviate mode competition caused by homogeneous gain broadening in erbium-doped fibers. Up to 28-wavelength lasing operation with wavelength spacing of 0.8 nm has been achieved. The outputs had uniform power distributions, and the power fluctuation in each wavelength is smaller than 0.2 dB within a period of an hour.

Optics Communications, 2006

A multiwavelength fiber laser based on multimode fiber Bragg gratings (MM-FBGs) is proposed and d... more A multiwavelength fiber laser based on multimode fiber Bragg gratings (MM-FBGs) is proposed and demonstrated. The laser, which is comprised of two MM-FBGs connected in a parallel configuration, can yield 10 stable output wavelengths using the offset launch technique.

IEEE Photonics Technology Letters, 2005