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ABSTRACT: We propose a leaky channel waveguide structure for large-mode-area single-mode operation. The proposed structure is characterized
by a uniform rectangular core and a specially designed cladding, through which all the confined modes are leaky. Single-mode
operation is ensured by choosing the waveguide parameters properly so that the differential leakage loss between the first
two modes is sufficiently high. A general power-law cladding geometry profile is considered, which is solved by the effective-index
method in conjunction with the transfer-matrix-method to obtain the effective indices and leakage losses of the modes. We
show that, with a suitable choice of cladding parameters, the waveguide can demonstrate extended single-mode operation in
the wavelength range 750–1600nm with a core area as large as 100μm2. Such a large confinement area for mode propagation can effectively suppress nonlinear optical effects. The waveguide is
expected to find applications in the design of high-power lasers and amplifiers.
Applied Physics B 04/2012; 90(3):507-512. · 2.19 Impact Factor
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ABSTRACT: We demonstrate a new approach of fabricating a thermo-optic polymer-waveguide Mach-Zehnder interferometer (MZI). The MZI is fabricated with an imprinting technique, where the electrode heater is formed at the bottom of the waveguide substrate.
OptoElectronics and Communications Conference, 2009. OECC 2009. 14th; 08/2009
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ABSTRACT: Long period fiber gratings (LPFGs) formed in photonic crystal fibers (PCFs) are of considerable interest because they can provide many new opportunities for optical and biochemical sensing. LPFGs can be fabricated in PCFs by intense CO<sub>2</sub>-laser radiation through deforming the fiber geometry or changing the glass structure. In this paper, we report a new, efficient way of writing LPFGs in PCFs, which is based on the generation of frozen-in inelastic tensile stresses in a tensioned PCF by CO<sub>2</sub>-laser heating. The mechanism, known as frozen-in viscoelasticity, can also improve the writing efficiency of LPFGs in conventional single-mode fibers.
Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
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ABSTRACT: We propose a refractive-index sensor that operates on the principle of exciting the long-range surface plasmon mode of a metal-coated waveguide with a long-period grating formed in the waveguide, where the wavelength at which the mode excitation occurs serves as a measure of the refractive index of the external medium. We analyze the sensor with a coupled-mode theory and highlight the effects of the waveguide parameters on the loss of the surface plasmon mode and the performance of the sensor. Our results show that the sensor can provide a sharp resonance for high precision measurements and a high sensitivity comparable to that of an optimized bulk prism-based surface plasmon sensor. Our sensor also offers much flexibility in the choice of waveguide parameters for different applications.
Optics Express 06/2009; 17(10):7933-42. · 3.59 Impact Factor
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ABSTRACT: We demonstrate that the efficiency of CO(2) laser writing of long-period fiber gratings in a solid-core photonic crystal fiber (PCF) can be enhanced greatly by applying tension to the fiber during the writing process through the mechanism of frozen-in viscoelasticity. Using this mechanism, we are able to write strong gratings in PCFs with a dosage of CO(2) laser radiation low enough not to cause any significant fiber structure deformation.
Optics Express 04/2009; 17(6):4533-9. · 3.59 Impact Factor
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ABSTRACT: We report electro-optic (EO) long-period waveguide gratings (LPWGs) fabricated in a special lithium-niobate (LiNbO3) waveguide structure. The waveguide consists of a clad core formed with a two-step proton-exchange process and a thin cover layer created by an additional reverse proton-exchange process for the restoration of the EO strength of the waveguide. Using several LPWG samples, we demonstrate experimentally the effects of using different cladding modes and waveguide parameters on the grating performance. One of our 10-mm long samples shows a 27-dB rejection band at a driving voltage of 95 V with a center wavelength tunable thermally at a sensitivity of -0.4 nm/degrees C. Our analysis of the theoretical limit of the efficiency of such an EO grating suggests room for significant further improvement by optimizing the waveguide and electrode designs. The LiNbO(3) LPWG provides an EO control of the grating strength and a thermo-optic control of the operating wavelength and thus opens up many new opportunities for high-speed applications, such as dynamic optical filtering and optical intensity modulation.
Optics Express 01/2009; 16(25):20409-17. · 3.59 Impact Factor
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ABSTRACT: We present a UV-written polymer long-period waveguide grating coupler, which can be tuned over a wavelength range of 100 nm with a temperature control of 22 degC. Its coupling efficiency varies between 57% and 80%.
Opto-Electronics and Communications Conference, 2008 and the 2008 Australian Conference on Optical Fibre Technology. OECC/ACOFT 2008. Joint conference of the; 08/2008
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ABSTRACT: Using several electro-optic long-period grating s fabricated on LiNbO 3 wave guides, we demonstrate the effects of the cladding modes and the waveguide struct ure on the grating performance. We obtain a 25-dB rejection band at 95-V driving voltage.
Opto-Electronics and Communications Conference, 2008 and the 2008 Australian Conference on Optical Fibre Technology. OECC/ACOFT 2008. Joint conference of the; 08/2008
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ABSTRACT: We propose a special lithium-niobate (LiNbO<sub>3</sub>) single-mode waveguide for the realization of long-period gratings, which consists of a channel core embedded in a thin slab cladding. We fabricated the waveguide on a z-cut LiNbO<sub>3</sub> substrate with a two-step proton-exchange process and demonstrated its suitability for grating application with a number of removable photoresist long-period gratings deposited on the waveguide surface. The waveguide fabrication process and the LiNbO<sub>3</sub> waveguide structure could be further explored for the development of electrooptic gratings for high-speed applications.
IEEE Photonics Technology Letters 08/2008; · 2.19 Impact Factor
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ABSTRACT: Epitaxial Ba 0.7 S r 0.3 TiO 3 (BST) thin films were deposited on MgO (001) single crystal substrates using pulsed laser deposition. The bidimensional structure of a rib-type Mach-Zehnder electro-optic modulator was designed using the effective index method. A Mach-Zehnder electro-optic modulator based on BST/MgO was fabricated using standard photolithography and reactive ion etching techniques. A single mode near-field output pattern was observed using an end-fire coupling method. Optical modulation was successfully demonstrated. The half-wave voltage V π was found to be 60 V and the effective electro-optic coefficient was calculated to be r c eff = 27.0 × 10−12 m/V at a wavelength of 1550 nm.
Ferroelectrics. 11/2007; 357(15 October 2007):109-114.
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ABSTRACT: We demonstrate a technique of applying the prism-coupler method to the characterization of dielectric films that are too thin to support enough guided modes in air for the normal application of the method. The technique is based on applying suitable index-matching liquids on the surface of the thin film to increase the number of effective indexes available for the determination of the refractive index and the thickness of the film. With this technique, even thin films that do not support any guided modes in air can be characterized. We apply the technique to the characterization of polymer thin films as thin as 100-200 nm and discuss its performance and limitation
Journal of Lightwave Technology 06/2007; · 2.78 Impact Factor
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ABSTRACT: A three-dimensional 1times4 switching matrix based on polymer optical waveguides is reported. Its features are: compactness, small switching electric power, and wavelength independent. This structure can be readily generalized to a mtimesn matrix.
Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007. OFC/NFOEC 2007. Conference on; 04/2007
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ABSTRACT: We demonstrate experimentally two widely tunable optical couplers formed with parallel long-period polymer waveguide gratings. One of the couplers consists of two parallel gratings and shows a peak coupling efficiency of ~34%. The resonance wavelength of the coupler can be tuned thermally with a sensitivity of 4.7 nm/ degrees C. The experimental results agree well with the coupled-mode analysis. The other coupler consists of an array of ten widely separated gratings. A peak coupling efficiency of ~11% is obtained between the two best matched gratings in the array and the resonance wavelength can be tuned thermally with a sensitivity of -3.8 nm/ degrees C. These couplers have the potential to be further developed into practical broadband add/drop multiplexers and signal dividers.
Optics Express 01/2007; 14(26):12644-54. · 3.59 Impact Factor
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ABSTRACT: We fabricated a specially designed polymer long-periodwaveguide grating to demonstrate the phenomenon of dual resonance arising from light coupling between the core mode and a low-ordercladding mode of the waveguide. By varying the temperature of the grating, we observed the onset and the evolution of the dual-resonancewavelengths. The separation between the dual-resonancewavelengths was varied by ∼110nm with a temperature variation of ∼10°C. The experimental results are explained well by the simulation results.
Applied Physics B 12/2006; 86(1):147-150. · 2.19 Impact Factor
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ABSTRACT: We propose a novel optical planar waveguide structure for single-mode operation. The proposed structure has a uniform core and a leaky cladding. The cladding is characterized by a refractive-index profile that increases with the distance from the core. Such a structure supports leaky modes. A careful design can ensure a low leakage loss for the fundamental mode and much higher leakage losses for higher-order modes. With all the high-order modes stripped off, the waveguide supports effectively only the fundamental mode even with a large core. We introduce a class of power-law cladding profiles to demonstrate large-core single-mode operation with the structure. The effects of the profile parameters on single-mode operation are investigated by calculating the leakage losses of the first two modes using the transfer-matrix method. Owing to its large confinement area for single-mode operation, the proposed structure can suppress nonlinear effects effectively and is expected to find applications in the design of high power waveguide lasers and amplifiers.
Applied Physics B 09/2006; 85(1):11-16. · 2.19 Impact Factor
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Integrated Ferroelectrics 09/2006; 69(2005):443-451. · 0.30 Impact Factor
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ABSTRACT: We report the design and fabrication of Bragg gratings in benzocyclobutene (BCB) channel waveguides with emphasis on the demonstration of their polarization dependence. The effects of the stress-induced birefringence in the waveguide on the polarization dependence of the Bragg gratings are characterized and discussed. Our results show the possibility of realizing tunable polarization-insensitive Bragg-grating filters with simple polymer waveguide structures. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 334–338, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21342
Microwave and Optical Technology Letters 01/2006; 48(2):334 - 338. · 0.62 Impact Factor
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ABSTRACT: We present a simulation of the temperature sensitivity of the resonance wavelength of a long-period waveguide grating (LPWG). We find that the temperature sensitivity of an LPWG in a channel waveguide is proportional to a modal dispersion factor that depends sensitively on the size of the core of the waveguide. Measurements with experimental polymer LPWGs agree well with the simulation results. The dimension of the waveguide core is an effective parameter for the control of the thermal characteristics of an LPWG in a channel waveguide.
Applied Physics Letters 07/2005; · 3.84 Impact Factor
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ABSTRACT: We propose a composite polymer vertically-coupled optical waveguide switch that offers wavelength independent switching characteristics. The variation of the extinction ratio within the C-band is less than 4 dB for bar state and 1 dB for cross state.
Optical Fiber Communication Conference, 2005. Technical Digest. OFC/NFOEC; 04/2005
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ABSTRACT: A long-period waveguide grating in a polymer channel waveguide, which consisted of a benzocyclobutene core and an epoxy cladding, has been fabricated. By changing the stress in the waveguide through etching of the cladding width, a polarisation-insensitive resonance wavelength thermo-tunable from 1520 to 1610 nm with a temperature range of only 8°C was achieved.
Electronics Letters 05/2004; · 0.96 Impact Factor
