低损耗波纹波导的传输特性

为了降低太赫兹波传输的损耗,研究了波纹波导中传输太赫兹波时的损耗特性,得到波纹波导的衰减常数的理论计算公式,在数值计算基础上设计了220 GHz低损耗波纹波导,并通过电磁仿真对数值计算结果进行验证,HE11模式实现了仿真与理论结果的相互吻合。     

Low-loss fibre-coupled waveguide directional coupler modulator

We report a fibre-coupled Ti: LiNbO3 directional coupler modulator with total fibre-device-fibre insertion loss as low as 1.5 dB for ?=1.32 ?m. Low loss has been achieved by using diffusion parameters to give good mode match to the fibre and low propagation loss, an effective SiO2 buffer layer to eliminate electrode loading loss and a directional coupler geometry which minimises the effect of bend loss.     

Low-loss singlemode waveguide and fibre bends

A new theoretical strategy for reducing bend loss is presented. It is based on the concept of introducing both depressed and increased index regions into the cladding of planar waveguides on the outside of the bent core. A similar strategy can be applied to optical fibres. In both cases, the bending loss is reduced beyond that achievable with the presence of depressed regions alone in the cladding     

Low-loss twists in oversized rectangular waveguide

The unwanted mode conversion from twists in overmoded waveguides is calculated from numerical integration of the coupled-mode equations, considering simultaneous coupling of the five lowest-order modes coupled in a twist. Twists with tapered or linearly varying rates of twist are shown to be superior in medium- or broad-band applications to those with uniform twist rate. Measurements consistent with these theoretical calculations are discussed for uniform twists in WR90 waveguide at 60 GHz and for an electroformed twist having a linearly tapered rate of twist in WR187 waveguide from 15.7 to 17.7 GHz. The coupling coefficients needed in the calculations are derived and are compared with the results of other work, including a modal expansion of the dominant mode in twisted waveguide. The work also considers the transmission through an oversized waveguide with a mode converter generating a trapped unwanted mode, and the result for the dependence of the resonance depth on the mode conversion and the attenuation of the trapped mode is found     

Multikilohertz all-optical modulator in semiconductor doped glass channel waveguide

A polarisation independent all-optical modulator is presented with 100% modulation depth at multikilohertz repetition rate in semiconductor doped glass channel waveguide. An interpretation of the modulation mechanism is given.<>     

低损耗太赫兹波导及其成像应用

高性能的太赫兹功能器件在太赫兹波的产生、传输及探测上都有着重要意义.报道了一种Kagome型低损耗太赫兹波导及其成像应用.首先根据反谐振波导理论设计了0. 1 THz处低损耗的太赫兹波导,其理论损耗低至0. 012 cm~(-1).然后使用3D打印技术制备波导实物,实验测得其损耗为0. 015 3 cm-1,波导末端光束发散角为6±0. 5°.最后基于该波导搭建了可重构太赫兹成像装置,分别实现了对隐藏刀片、矿石的反射和透射成像,在地下远距离勘探领域具有潜在的应用前景.     

Low-loss high-silica single-mode channel waveguides

Low-loss high-silica single-mode channel optical waveguides of 0.1 dB/cm have been fabricated on crystal silicon substrates with fibre coupling losses of less than 0.05 dB by flame hydrolysis deposition and reactive ion etching. Directional couplers have also been fabricated with excess loss of 0.5 dB by this waveguide fabrication technique.     

Low-loss three-dimensional waveguide crossings using adiabatic interlayer coupling

The silica-based planar lightwave circuit (PLC) is a promising technology for application to a reconfigurable optical add/drop multiplexer (ROADM), which contains arrayed waveguide gratings (DEMUX/MUX), variable optical attenuators (VOAs), switches (SWs), and tap monitors (TAPs) as shown in Fig. 1. Specifically, single-chip integration with higher delta (D) contrast waveguides, which allow a small bending radius, enables us to realise compact and low-cost ROADM modules [1]. The critical problem with regards to single-chip integration is the large excess loss caused by conventional two-dimensional (2D) waveguide crossings as shown by the broken line in Fig. 1, because a large channel number of more than 40 ch is strongly required in ROADMsystems, and the crossing loss will accumulate in proportion to the channel number. On the other hand, three-dimensional (3D) waveguide crossings are attractive because they are fundamentally lossless [2, 3]. The most important technical aspect with regards to 3D waveguide crossings is to find a way to interconnect between vertically stacked waveguides. Various approaches have been proposed for realising interlayer coupling. One approach is direct writing using a femtosecond laser [2]. The problem with this approach is that the writing process time increases in proportion to the number of channels. Another approach involves using vertical directional couplers to realise interlayer coupling of the double waveguide structures [3, 4]. In this case, a severe fabrication tolerance is required if we are to form a directional coupler with 100% coupling. To overcome these problems, we propose and demonstrate 3D waveguide crossings based on a triple waveguide layer structure and adiabatic double/stacked-core modefield (MF) converters. By adopting simple mode conversion with the middle waveguide layer, we can provide stable low-loss interlayer coupling between vertically stacked upper and lower waveguides.     

Low-loss Cu/sup +/-Na/sup +/ ion exchanged optical channel waveguides in glass

Electric field assisted Cu/sup +/-Na/sup +/ ion exchanged optical channel waveguides have been produced in Corning 7740 borosilicate glass using a Cu film source. Average losses of 1.0, 0.45 and 0.3 dB/cm, at wavelengths of 633, 850 and 1300 nm, respectively, have been measured.     

Low-loss antiresonant reflecting optical waveguide on Si substrate in visible-wavelength region

A low-loss (0.3 dB/cm) antiresonant reflecting optical waveguide on an Si substrate was realised at 0.633 ?m wavelength by employing a TiO2/SiO2 interference reflector instead of an Si/SiO2 pair used in the long-wavelength range.     

Low-loss propagation in the dipole-mode along a coaxial waveguide

A theoretical investigation has been made as a step towards defining more precisely the operating conditions of a fully screened dipole-mode waveguide, comprising a coaxial structure whose inner consists of a cylindrical grid of parallel longitudinal wires separated by air and whose outer is represented by a concentric tube of continuous metal.     

Optical channel waveguide in chalcogenide (Ga:La:S) glass

A novel method for fabricating optical channel waveguides in Ga:La:S chalcogenide glass, through continuous wave direct UV laser writing (λ=244 nm) is reported. Well-formed single-mode channel structures, with low propagation losses of 0.38±0.05 dB/cm at 1.3 μm, were engineered using this technique     

Low-loss electrooptic BaTiO/sub 3/ thin film waveguide modulator

A strip-loaded electrooptic waveguide modulator based on an epitaxial BaTiO/sub 3/ thin film was fabricated and characterized for the first time. The strip-loaded waveguide structure greatly improves waveguide propagation and polarization-dependent loss performance. A propagation loss of 1.1 dB/cm and polarization dependent loss of 0.1 dB/cm were measured. The electrooptic waveguide modulator exhibited a half-wave voltage-interaction length product of 4.5 V /spl middot/ cm at a wavelength of 1542 nm. The measured effective electrooptic coefficient of the as-grown BaTiO/sub 3/ waveguide modulator was 38 pm/V. The experimental results indicate that a strip-loaded thin film waveguide modulator is suitable for photonic applications.     

Low-loss flat-top passband arrayed waveguide gratings realised byfirst-order mode assistance method

A novel method of flattening the passband of an arrayed waveguide grating with a small excess loss is described, which employs a new concept that uses the assistance of the weak first-order mode. A 16-channel 100 GHz-spacing demultiplexer with a fibre-to-fibre loss of less than 3.6 dB and a flattened excess loss of 1.85 dB is demonstrated. The 1 dB down passband is widened 2.2 times     

Sol-gel glass waveguide and grating on silicon

This paper reports on the fabrication and characterization of hybrid organic-inorganic glass sol-gel slab and channel waveguides by ultraviolet light imprinting in thin films deposited by a one-step dip-coating process. The adjustment of chemical composition of the materials provides precise selection of refractive index from 1.48 to 1.52 at the wavelength of 632.8 mn. The refractive index of the waveguides at 1.55 μm is similar to that of optical fiber, thus reducing the reflection loss between the two to less than 0.01 dB. The effect of ultraviolet light exposure and heat treatment on waveguide refractive index is studied. Fabrication parameters to produce ridge waveguides are optimized to achieve very smooth side walls. Propagation losses in these waveguides are ~0.1 dB/cm. Single mode buried waveguides, at 1.55 μm wavelength, with circular mode profile are demonstrated     

Low-loss fibre-chip coupling by buried laterally tapered InP/InGaAsP waveguide structure

A passive InP/InGaAsP spot-size transformer for low-loss coupling of semiconductor optoelectronic devices to single-mode fibres has been fabricated entirely on InP. Using a buried two-layer laterally tapered section, spot-size transformation is demonstrated from below 2 mu m up to 8 mu m, the spot size of a dispersion-shifted fibre at 1550 nm. For a chip without antireflection coating a total insertion loss of 2.7 dB was achieved at a taper length of approximately 600 mu m.<>     

Low-loss laser diode module using a molded aspheric glass lens

The fabrication and characteristics of a 1.3-μm laser diode (LD) module for single-mode fiber using a molded aspheric glass lens is discussed. An average coupling loss of 2.2 dB with a standard deviation of less than 0.5 dB after thermal heat cycling tests was achieved. The average assembly loss was 0.24 dB. The LD module demonstrated stability during thermal and heat cycling tests from -10 to 60°C     

Erbium-doped composite glass waveguide amplifier

Optical amplification at 1.523 mu m wavelength is demonstrated in an erbium-doped glass waveguide. More than 10 dB amplification is achieved in a 4.7 mm long waveguide with about 30 mW guided pump power of 0.9734 mu m wavelength.<>     

离子交换平板玻璃光波导

本文报导了把玻璃放在熔融的AgNO_3中制备玻璃光波导,其工艺简单,可以重复.我们测量了波导的有效折射率、波导厚度以及损耗等.波导损耗小于1分贝/厘米.     

Semiconductor-doped glass waveguide electro-absorption modulator

A semiconductor-doped glass optical waveguide modulator has been fabricated and characterised. Semiconductor-doped glass is a widely available material that has recently been shown to have interesting electroabsorptive properties. The work presented represents progress towards a practical switching device with significant depth of modulation.<>