High-index and low loss polyethylene terephatate optical waveguides

In this paper, the fabrication and characterization of a high-index low loss polyethylene terephatate (PET) optical waveguide is presented. Dip-coating technique has been used to fabricate the optical waveguide using PET. Various waveguide properties, such as mode effective refractive index, optical loss, dispersion and waveguide thickness as a function of temperature of waveguides and substrates have been reported. Optical losses of as low as 0.7 dB cm^–1 waveguides can be obtained if the formation temperature can be controlled between 30 and 35°C. In addition, we suggested that it is a suitable material for optoelectronic waveguide devices.     

Dip-coated HNR120 photoresists thin-film optical waveguides

We report on our systematic and detailed study of fabrication and characterization of HNR120 photoresists thin-film optical waveguides. Various waveguide properties, such as refractive index, optical losses as a function of temperature, waveguide thickness, dispersion and birefringence have been studied. The optical loss are found to be <1.4 dB cm⁻¹.     

A numerical analysis of gain characteristics of Er-doped Al2O3 waveguide amplifiers

The gain characteristics of erbium-doped Al₂O₃ waveguide amplifiers are investigated by solving numerically rate equations with upconversion effects and propagation equations. We obtained the dependence of gain of erbium-doped Al₂O₃ waveguide amplifiers on the waveguide length, erbium concentration and pump power at different pumping wavelengths (980 and 1480 nm). The performance of amplifiers pumping at 1480 and 980 nm are compared. It is shown that 980 nm pumping has higher gain and higher pumping efficiency. The parameters of waveguide amplifiers have been optimized. A optical gain of 43 dB can be achieved for a optimum waveguide length of 8.25 cm and 5.8 × 10²⁰ cm^–3 Er concentration pumped with 100 mW at 980 nm, that is a gain of 5.2 dB/cm.     

Beam Steering Type of 1 : 4 Optical Switch Using Thermo-Optic Effect

We propose a beam steering type optical switch employing a phase shifter. It consists of collimating waveguide mirrors, an arrayed-waveguide which has deep trenches incorporating polymer materials, and input/output waveguides. The incident light is guided to the front mirror, where it is then collimated, and input to the arrayed waveguide. The number of trenches filled with polymer linearly increases in order. The refractive index of the polymer can be controlled with temperature, and the propagation direction of the output light from the arrayed waveguide can also be controlled. A switch with 15 waveguides in the array has been fabricated. The chip size is about 2:5 × 9:0 mm², the insertion loss is 10 dB, and the extinction ratio is about 10–13 dB.     

Optical transmission loss in tin oxide thin film waveguide

This paper reports the optical transmission loss of tin oxide thin film waveguide. The effect of oxidation temperature, thickness and air ageing (40 days at room temperature) was studied. The vapour chopping technique has been used successfully to reduce the optical transmission loss. The vapour chopped tin oxide thin film waveguide (2.90-3.60 dB/cm) showed smaller transmission loss than those of nonchopped tin oxide thin film waveguide (4.16-4.74 dB/cm). Transmission loss was found to be a function of oxidation temperature and thickness. Due to increased oxidation temperature, transmission loss was found to decrease. The effect of increase in thickness was to increase the transmission loss. The air ageing effect caused the increase in transmission loss whereas the effect was found lesser in the vapour chopped tin oxide thin film waveguide.     

Measurement of the optical transmission modes and losses of the poled guest–host polymer NAEC/PEK-c planar waveguides

The polyetherketone (PEK-c) guest–host polymer planar waveguides doped with (4′-nitro)-3-azo-9-ethyl-carbazole (NAEC) were prepared. The waveguide films were poled by corona-onset poling at elevated temperature (COPET), and the corona poling setup includes a grid voltage making the surface-charge distribution uniform. By using the prism-in coupling method, the dark-line spectrum given by the reflected intensity versus the angle of incidence have been obtained, and the optical transmission losses of mth modes have been measured for the poled polymer waveguides at λ=632.8 nm. The measurement result showed that the optical loss of the fundamental mode is less than 0.7 dB cm⁻¹ for the TE polarization.     

特种非对称低损耗1×5光分路器

设计和优化了一种新型低损耗、低偏振的基于二氧化硅的特种非对称1×5光分路器.在设计Y分支结构时,输入端采用缓变展宽波导结构和直波导过渡波导相结合的结构,此结构可以使输入光场缓慢展宽,进行分束前的准备,大大减小分支结构的辐射损耗和模式转换损耗.非对称1×5光分路器第一个端口输出功率占50%,第二至五端口输出功率占50%.利用三维光束传播法模拟和优化了特种非对称1×5光分路器,模拟结果表明,该结构具有均匀性好、器件尺寸小、低损耗和低偏振等优点,1×5光分路器在1 250~1 650 nm波长范围内,第一个输出端口附加损耗小于0.07 dB,均匀性小于0.023 dB,偏振相关损耗小于0.009 dB,第二到五端口附加损耗小于0.45 dB,均匀性小于0.41 dB,偏振相关损耗小于0.06 dB.     

Observation of all-optical wavelength conversion based on cascaded effect in periodically poled lithium niobate waveguide

We experimentally demonstrate multi-channel wavelength conversion through the cascaded second-order nonlinear processes in periodically poled lithium niobate waveguide in the optical communication wavelength band of 1.5 μm. The normalized conversion efficiency as high as 90% W⁻¹ cm⁻² is obtained. Wavelength conversion over a broad wavelength range of 66 nm has been confirmed.     

Beam delivery characteristics of optical fibres for carbon monoxide lasers

An experimental investigation has been conducted of the propagation characteristics of several types of optical fibres which are candidates for use in optical beam delivery systems for carbon monoxide lasers. Both solid core (chalcogenide) fibres and hollow core (with dielectric or dielectric coated metal) waveguides have been investigated. Such experiments have included an assessment of both the power transmission characteristics, and the effects of waveguide transmission on the optical quality of the beam at the exit of the fibre. The experiments indicated lowest loss for the chalcogenide solid core fibre with a value of 0.4 dB m⁻¹.     

Optical fibre strength/fatigue experiments

New techniques for measuring and analysing the strength characteristics of optical waveguide fibres have evolved as the strength of the optical fibres improved. A recent life-fatigue experiment is described and the results analysed in terms of the most commonly used theoretical model which results in the power law V = AKⁿ. Ten m long fibre samples were tensilely stressed in a high humidity environment by both fixed (static fatigue) and constant rate (dynamic fatigue) loads. The respective test values for the power law exponent, the fatigue constant ‘n’, were 38 and 17. The results of the tests indicate the more conservative value, 17, for practical engineering design, and the need for incorporating an ageing term in the model.     

Thermo-Optic Switch using Fluorinated Silicon Oxide and Organic Spin-on-Glass Films

A thermo-optic switch in a thin-film optical waveguide was investigated. Fluorinated silicon oxide (SiOF) and organic spin-on-glass (SOG) films were used as core-layer and clad-layer, respectively, in the waveguide structure. The SiOF films were formed at 23#x00B0;C by a liquid-phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H₂SiF₆) aqueous solution. Thermal coefficients of the refractive indices for LPD-SiOF and organic SOG films formed on silicon (Si) substrates were #x2212;4.0 #x00D7; 10^#x2212;6/#x00B0;C, #x2212;60 #x00D7; 10^#x2212;6/#x00B0;C at the wavelength of 632.8 nm, respectively. A high extinction ratio of 15 dB was obtained for this switch at the applied voltage of 12.8 V.     

Properties of a Thin-Film Optical Waveguide Using Fluorinated Silicon Oxide and Organic Spin-on-Glass Films

A thin-film optical waveguide using a fluorinated silicon oxide (SiOF) as a core layer was investigated. An organic spin-on-glass (SOG) film was used for a cladding layer. The SiOF films were formed at 23°C by a liquid-phase deposition (LPD) technique using a supersaturated hydrofluosilicic acid (H₂SiF₆) aqueous solution. A thin-film optical waveguide structure for single mode was designed and fabricated, based on the dispersion properties of refractive indices for the LPD-SiOF and organic SOG films. The refractive indices at a wavelength of 632.8 nm were 1.430 and around 1.400 for the LPD-SiOF and organic SOG films, respectively. The thickness of LPD-SiOF films deposited was 1.18 μm. Thicknesses of cladding organic SOG films cured at 300 and 400°C were 1.28 and 1.31μm, respectively. The effective refractive indices for single mode were 1.4169 and 1.4158 at a wavelength of 632.8 nm for the cladding organic SOG films cured at 300 and 400°C, respectively, and differences between the measured and calculated incident angles were 0.84° and 1.29° for the cladding organic SOG films cured at these respective temperatures. A streak of guided-light was observed for the LPD-SiOF/SOG structure optical waveguide. The transmission loss was 7.6-7.9 dB/cm.     

Compact four-channel reconfigurable optical add-drop multiplexer using silicon photonic wire

We designed and fabricated a four-channel reconfigurable optical add-drop multiplexer based on silicon photonic wire waveguide, which is controlled through the thermo-optic effect. The effective footprint of the device is about 1000 × 500 μm². The minimum insertion loss including the transmission loss and coupling loss is about 10.7 dB. The tuning bandwidth is about 17 nm, the average tuning efficiency about 6.11 mW/nm and the tuning speed about 24.5 kHz.     

γ辐射对光纤波导电磁场分布的影响

开展了光纤波导中的电磁场传输理论分析,得到了光纤折射率变化对波导中电磁场分布的影响规律,建立了块状融石英材料及光纤光栅在60Co 辐射作用下折射率变化的测量系统,开展了折射率随辐射剂量变化及光纤模场测量实验。结果表明:光纤的折射率随辐射剂量的增加而增大,折射率的变化会引起波导中传输模式的场强分布变化,从而导致光纤的辐射感生波导损耗;在一定的辐射剂量范围（0～2000 Gy）内,光纤仍满足弱导边界条件,能够维持对传输模式的约束能力。     

Infrared Optical Fiber Sensors

Notably improved performance as well as extended application areas is expected in the technology of optical fiber sensors using infrared fibers that transmit radiation in a wavelength range beyond 2 μm. Measurement of infrared radiation is particularly important in thermometry and spectrometry. In these areas, the use of infrared fibers has been studied extensively not only as a transmission waveguide but also as a sensor chip. Of various infrared fibers, fluoride glass fibers exhibit the lowest transmission loss and hence are useful for remote sensing that requires light transmission over a long distance. The wide transmission range of chalcogenide glass fibers and halide crystalline fibers is valuable for thermometry in a low temperature range and for spectrometry of various molecules. Hollow waveguides are useful as a capillary flow cell that realizes fast-response spectrometry. The advantages and disadvantages of infrared fibers must be considered carefully in the development of fiber sensors. In this paper, the progress of infrared optical fiber sensors is reviewed with particular interest in thermometry and spectroscopy.     

All‐optical modulation based on silicon quantum dot doped SiOx:Si‐QD waveguide

All‐optical modulation based on silicon quantum dot doped SiO_x:Si‐QD waveguide is demonstrated. By shrinking the Si‐QD size from 4.3 nm to 1.7 nm in SiO_x matrix (SiO_x:Si‐QD) waveguide, the free‐carrier absorption (FCA) cross section of the Si‐QD is decreased to 8 × 10⁻¹⁸ cm² by enlarging the electron/hole effective masses, which shortens the PL and Auger lifetime to 83 ns and 16.5 ps, respectively. The FCA loss is conversely increased from 0.03 cm⁻¹ to 1.5 cm⁻¹ with the Si‐QD size enlarged from 1.7 nm to 4.3 nm due to the enhanced FCA cross section and the increased free‐carrier density in large Si‐QDs. Both the FCA and free‐carrier relaxation processes of Si‐QDs are shortened as the radiative recombination rate is enlarged by electron–hole momentum overlapping under strong quantum confinement effect. The all‐optical return‐to‐zero on‐off keying (RZ‐OOK) modulation is performed by using the SiO_x:Si‐QD waveguides, providing the transmission bit rate of the inversed RZ‐OOK data stream conversion from 0.2 to 2 Mbit/s by shrinking the Si‐QD size from 4.3 to 1.7 nm.     

用于光互连的聚硅氧烷波导弯曲损耗

研究了用于光互连的聚硅氧烷多模光波导直接弯曲时弯曲损耗与圆弧曲率半径的关系。用Marcuse的直波导近似法理论计算了其弯曲损耗,理论计算表明弯曲损耗随模阶数的增加而变大,随半径的减少而变大;光在波导中传输时,总弯曲损耗出现阶跃式变化,并且曲率半径大于4 mm时,波导的弯曲损耗小于1dB/cm。用BeamPROP仿真软件仿真了5、10、20mm三种曲率半径下的传输光场情况。利用数字化散射法测量了其弯曲损耗,实验结果显示曲率半径在5～6mm时弯曲损耗值在0.55～0.8dB/cm之间,考虑所制备的聚硅氧烷直波导固有的传输损耗,实验值与理论值基本相符。     

Spectrum Invariance for a Particular Class of Optical Fields Propagated in Far Zone

This paper describes invariance of the normalized optical spectrum for a particular class of optical fields propagated in the far zone from a secondary, spatially, partially coherent source. The optical field across the secondary planar source is inhomogeneous to give the complex degree of spectral coherence such that μ = h(αω(ρ₁–ρ₂))exp(iɛω(ρ₁²–ρ₂²)), where α, ɛ are constants, ω is optical frequency, and ρ₁, ρ₂ denote two points in the secondary source. This expression for μ is the same as obtained in the Fresnel zone from a primary, spatially incoherent source. The invariance law does not hold for the spectrum of the light propagated from the primary source.     

4 × 4 Plastic Optical Fiber Star Coupler Incorporated with a Common Polymer Waveguide Optical Power Distribution Region

Abstract

Two types of 4 × 4 plastic optical fiber star couplers incorporated with a polymer waveguide as the optical power distributor are proposed, and their high performances are demonstrated. The characteristics of the proposed star coupler are investigated based on ray optics, and its power distribution performance is evaluated in terms of the flatness of the coupling ratio and the amount of the excess loss. Under the best conditions, the flatness of the coupling ratio and the excess loss of the fabricated device have been obtained as 2.0 dB and 2.5 dB, respectively.     

控制色散的波导结构分析

色散控制在光纤通信中越来越重要,从低速率到高速率,从单波长SDH到多波长DWDM,色散控制要求越来越严.通过对不同应用的光纤波导结构的制造、性能测试和分析,指出了波导结构设计与光纤衰减、模场直径、弯曲损耗和波导色散等的关系.这些实践经验可以指导光纤的设计与制造.