The bandwidth of single-mode operation in groove NRD waveguide

Based on analysing the dispersion characteristics of groove NRD waveguide using the eigen-weighted BIEM, the frequency bandwidth forE ₁₁ ^y single-mode operation is calculated, and the results show that the bandwidth of groove NRD waveguide is broader than that of NRD waveguide with the same principal sizes.     

Low-loss and thermally stable TE-mode selective polymer waveguide using photosensitive fluorinated polyimide

A low-loss, thermally stable TE-mode selective optical waveguide was fabricated using a photosensitive fluorinated polyimide. The polymer undergoes photocrosslinking under UV exposure, thus changing its refractive index. The photocrosslinking-induced refractive index change was utilized to form channel waveguides. The propagation losses of the photosensitive fluorinated polyimide waveguides were less than 0.3 and 0.5 dB/cm for TE polarization at wavelengths of 1.3 and 1.55 /spl mu/m, respectively. The measured polarization extinction ratio was higher than 29 and 28 dB at wavelengths of 1.3 and 1.55 /spl mu/m, respectively. The refractive index of fluorinated polyimide film remains almost constant after being stored at 150/spl deg/C for 600 min.     

Embedded channel polyimide waveguide fabrication by direct electronbeam writing method

A new embedded channel polyimide waveguide fabrication process by a direct electron beam writing method (DEBWM) is described. The new technique uses an electron-beam induced effect to directly alter the refractive indices of the two-layer polyimide. Both the core and the lower cladding have been fabricated at the same time in two-layer polyimides using electron beam with 25 keV energy. The obtained embedded channel waveguide was made of two kinds of polyimides, one for lower cladding and one for core and other claddings. Guide losses are 0.3 dB/cm for both TE and TM polarized incident lights and guiding mode is single-mode for TE. The optical properties of the waveguide and a relationship between the doses of electron beam and optical losses or loss dependence on wavelength are also mentioned     

光敏聚酰亚胺在硫化镉紫外器件中的应用

介绍了光敏聚酰亚胺的特性及应用情况,将其引入到硫化镉紫外器件制作中,通过实验研究开发并掌握一种正性光敏聚酰亚胺的光刻工艺,亚胺化后将其作为硫化镉器件的表面钝化层,经过实验验证其粘附牢固度和光电性能满足使用要求。同时该光敏聚酰亚胺的应用能够简化近40%的制作工艺,提高了硫化镉紫外器件的生产效率和成品率。     

Design of single-mode step-tapered waveguide sections

Single-mode step-tapered waveguide sections are analyzed in an effort to determine how the various device parameters, specifically, taper function, mask spot size, and taper length, affect power loss. The results indicate that 1) for short to medium length tapers, linear tapers exhibit the lowest loss, whereas for long tapers, all of the taper functions exhibit essentially the same loss; 2) for single-mode transitions with waveguide widths in the range2-15 mum, the loss in a step-tapered waveguide section can be nearly minimized as long as the mask spot size is chosen such that there are at least 20-25 steps in the taper; and 3) the length of a given taper for minimum power loss is strongly influenced by the asymmetry of the waveguide structure.     

Design of a single-mode tapered waveguide for low-losschip-to-fiber coupling

The novel waveguide structures described in this paper have nonlinearly tapered shapes that result in low radiation losses despite their relatively short lengths. The core at the waveguide endface connected with the fiber has a very small cross section and an expanded mode field with a non-Gaussian shape. The taper structures are analyzed by using an improved step-transition method. This method is a based on the theory of enclosing a waveguide within electrical walls and that can therefore treat the radiation modes in a tapered waveguide as discrete mode spectra. Analyzing the relationships between the lengths and shapes of the tapers and the radiation loss due to the tapers show that appropriately tapered semiconductor waveguides operating at an optical wavelength of 1.55 μm and having a taper length of less than 0.7 mm can have a radiation loss of only 0.1 dB and a coupling loss with a conventional single-mode fiber of less than 0.5 dB     

消除波导厚度变动影响的高分子宽带耦合器设计

针对高分子光波导制造工艺中波导芯厚度的均匀性难以控制的实际困难,提出了采用抗波导芯厚度误差的宽带波导耦合器回路结构的解决方案,并给出了优化设计的理论和方法。在实测了含氟聚酰亚胺薄膜的色散特性的基础上,采用该方法做了中心波长为1550nm、带宽为120nm的3dB含氟聚酰亚胺波导耦合器设计。该器件的三维BPM仿真运行结果表明,在上述带宽上,波导芯厚度变动在7-8μm的范围内,器件的功率输出比保持了(50±0.9)%的良好特性。     

Enhanced ESI for prediction of waveguide dispersion in single-mode optical fibres

We provide an enhanced equivalent step index (EESI) approximation for the accurate prediction of waveguide dispersion on monomode optical fibres. Using a quadratic `enhancement function? the waveguide dispersion even for the triangular core profile fibre can be predicted to be between 92 and 100% of its exact value in the single-mode region.     

Improved cavity-stabilised oscillator circuit for single-mode operation

The well known Kurokawa circuit for cavity-stabilised oscillators is discussed, taking both circuit losses and frequency sensitivity of the diode mounting structure into account. It is found that modifying the original circuit by mismatching the d.c. bias port (damping resistor) leads to either increased output power or increased frequency stability. This result has been confirmed by measurements.     

Fluorescence and laser operation in single-mode Ti-diffusedNd:MgO:LiNbO3 waveguide structures

The spectral properties of the guided-wave Nd fluorescence and results of laser oscillation in Ti-indiffused single-mode Nd:MgO:LiNbO ₃ waveguides and waveguide cavities, respectively, are reported. The splitting and polarization behavior of the fluorescence lines around 0.9, 1.08, and 1.37 μm were studied. Using a single-mode diode laser as a pump source (λ_p=814.6 nm), an oscillation threshold in an 8-mm-long structure of 2.1-mW absorbed pump power has been obtained. An output power up to 310 μW (limited by the available pump power), a slope efficiency of 16% at power levels >150 μW, and an emission linewidth of 0.21 nm (at λ_s=1085 nm) have been measured     

Ion exchanged waveguide in new active and photosensitive glass

Active channel waveguides have been fabricated by ion exchange in a new erbium-doped, germane-silicate photosensitive glass. The passive and active properties of the waveguides have been investigated by standard techniques     

Design of DFB lasers for high-power single-mode operation

The longitudinal-mode behaviour above threshold for DFB lasers has been analysed taking into account spatial hole burning along the laser axis. As a result, the single-longitudinal-mode operating condition up to high optical output power has been made clear.     

Optical waveguide fabrication in neodymium-doped lithium niobate

Reports the realisation of high-quality, proton-exchanged optical waveguide structures in neodymium-doped lithium niobate. Measurements indicate that the presence of the neodymium does not alter the proton exchange rate, and the presence of the protons does not affect the emission and absorption spectra of the bulk material significantly. Such waveguides will permit the realisation of highly efficient semiconductor laser pumped amplifiers and laser structures integrated with electro-optic and/or acousto-optic elements     

Exploration of photosensitive polyimide as the modification layer in thin film microcircuit

Positive type photosensitive polyimide is used as the modification layer in the thin film transistors production process.The photosensitive polyimide is not only used as the second insulating layer,it can also be used instead of a mask because of the photosensitivity.A suitable curing condition can help photosensitive polyimide form the high performance polyimide with orderly texture inside,and the performance of imidization depends on the precise control of temperature,time,and heat control during the curing process.Therefore,experiments of different stepped up heating tests are made,and the ability of protecting silicon dioxide is analyzed.     

氟化聚酰亚胺光波导材料制备工艺及性能研究

为了能合成较大分子量的氟化聚酰亚胺光波导材料,采用了几种不同制备工艺,找到了较好的合成大分子量氟化聚酰亚胺的工艺,利用智能傅里叶红外光谱仪测量了合成的氟化聚酰亚胺的红外光谱,证实了材料的结构。为了证实氟化聚酰亚胺可以作为优越的光波导材料,对材料做了热重分析和差示扫描量热测试,材料在530℃左右才会分解,说明材料具有良好的热稳定性。同时利用薄膜测试仪测试分析了材料折射率与含氟量以及折射率和温度之间的关系。结果表明,折射率与含氟量、温度都呈线性关系。     

Estimation of single-mode waveguide dispersion using an equivalent-step-index approach

In the letter, the feasibility of applying the equivalent-step-index parameters to estimate the single-mode waveguide dispersion of various radially inhomogeneous profiles is studied. The results are compared to the actual values obtained by numerical techniques and the errors estimated. The equivalent-step approach seems to be accurate only for cases where the profiles do not deviate severely from the step-index profile.     

Thick-film fabrication techniques for millimetre-wave dielectric waveguide integrated circuits

The letter presents the results of an initial study performed in the development of millimetre-wave dielectric waveguide integrated circuits using novel thick-film printing techniques. The measurements of the propagation characteristics of sample lines at 60 GHz demonstrate the feasibility of such an approach and examples of printed components indicate its potential in low-cost high-volume applications.     

1.5 ?m phase-shifted DFB lasers for single-mode operation

Fabrication and single-mode laser oscillation were demonstrated for modified DFB lasers where the phase of the corrugations was shifted at the centre by a quarter guided-wavelength and which, in principle, provided a resonance at the Bragg wavelength and stable single-mode oscillation. Phase-shifted corrugations were fabricated using electron-beam lithography.     

Multi-oxide layer structure for single-mode operation invertical-cavity surface-emitting lasers

We propose a novel vertical-cavity surface emitting laser (VCSEL) with Al(Ga)As multi-oxide layer (MOX) structure for the purpose of enlarging window aperture maintaining single transverse mode operation. We have fabricated an InGaAs-GaAs VCSEL with the proposed MOX structure formed on GaAs (311)B substrate. We have performed a numerical simulation to investigate single-mode behavior of the proposed structure and showed a possibility of single-mode VCSEL's with a large active area. We have fabricated an 11-μm current aperture 960-nm wavelength VCSEL with this MOX structure. The threshold current and voltage were 1.0 mA and 2.0 V, respectively, which are comparable to those of conventional oxide VCSELs. In 8-μm aperture, single-mode operation was maintained with a driving current up to four times the threshold