No description available.

In this paper, a ring laser design based on tapered waveguide coupler is fabricated and discussed. Using the asymmetric tapered waveguide coupler, two different directional coupling can be realized. Such that, the spatial-hole burning problem in linear laser cavity can be avoided, leading to the possibility of unidirectional traveling laser. In the work, two types of ring laser structures are fabricated and analyzed, in which (1) 90 degrees total reflection mirrors (TIMs) and (2) circular retro-mirrors are defined. Through the current injection on the tapered waveguide coupler, the received spontaneous emissions power at different directions (clockwise and counterclockwise directions) shows a 3dB difference for both type (1) and (2). Two oscillations in ring resonator could give different round-trip loss, indicating the possibility to fabricate unidirectional ring laser.

Topping is a precommercial thinning (PCT) method where secondary stems are cut higher above the ground compared to conventional PCT. The secondary stems continue to live for a period and are supposed to compete with the main stems and promote their quality. The objective of the study was to compare the effect of PCT on height and diameter growth between topping and conventional PCT. The study also analysed the relationship between height and diameter growth and the number of stems after PCT. Nine topped stands and six conventional precommercially thinned stands were visited between February 28th and March 5. One sample plot per hectare was laid out in the investigated stands. In every sample plot the number of stems was counted and five main stems were measured for height, height growth since PCT, diameter and diameter growth since PCT. The results showed significantly higher effect on height growth after topping as compared to conventional PCT but no significant difference in the effect of diameter growth between topping and conventional PCT. After PCT the H/D quote (height/diameter quote) was higher (less taper) in topped stands and lower (larger taper) in conventional PCT.

A volume equation for predicting individual tree volume, and a taper function for describing a stem profile were developed for a little known species, Styrax tonkinensis (Siam benzoin) in northern Laos. The species has high potential commercial value and can make an important contribution to the local economy. It can provide two different types of products, a non-wood product (benzoin resin) and timber. In Laos, the most important product is currently resin, and the use of timber for commercial purposes is rare. One reason is that information about the timber is not available. In Vietnam, on the other hand, the species is an import pulpwood species. Data used in this study came from 73 trees. Trees were purposely selected to ensure coverage of a full range of tree sizes. Measurement was undertaken only on over-bark diameters due to some constraints, limitations and problems during the field data collection. However, due to the importance of under-bark volume for this species, a small available dataset was used to build a bark model as an interim guide to the errors associated with using over-bark models for estimating under-bark volumes. From this bark model, errors in estimating under-bark volumes of trees with diameters at breast height between 10cm and 17 cm were approximately 18%. Nineteen individual volume models, and 7 individual taper functions were compared for bias and precision. Collective names for the volume equations tested include single-entry, double-entry, logarithmic, combined variables. Most volume models had similar bias but a few were clearly biased. The models with similar bias were further evaluated by four common statistics including bias, standard error of estimates, standard deviation of residuals and mean absolute deviation. The results showed that a five parameter model was ranked first, and was the most precise model. However, the magnitudes of difference in prediction errors between this model and other models, particularly the three parameter model were not significant. For practical purposes, the simpler model was preferred. Seven taper functions tested here belong to three different groups including single taper equations, compatible taper equations and segmented taper equations. Evaluation of taper equations used the same residual analysis procedures and criteria as those applied with volume equations. Graphical residual analysis showed that most taper models had similar precision with their errors in diameter predictions being similar in range. However, some models showed obvious bias. The most highly ranked taper model was a compatible taper model of polynomial form. It was the least biased model. The second ranked model was a single, simple model. This latter model is relatively simple to apply, but it is not compatible with the volume model, yielding slightly different estimates of volume if it is integrated and rotated around the longitudinal axis of a tree. However, if the sole purpose is to describe tree taper, it is the best model to use.

The goal of the thesis is Ring Laser Integrated Taper-directional Coupler Using Deep Etching to Fabricate Total Internal Reflection Mirrors. In order to total internal reflection, we make deep etching for the total reflection mirror. We use the tapered waveguide coupler, if unidirectional traveling-wave oscillation can be achieved, spatial hole burning effects seen in DFB laser can be avoided. In this paper, two types of ring laser structures are fabricated and discussed, in which (1) 90 degrees total reflection mirrors and (2) circular retro-mirrors. In fabrication process, we get smooth waveguide and highly perpendicularity waveguide by Self-Alignement wet etch method. In order to reduce bending loss and waveguide loss, we make deep etching for the total reflection mirror and circular retro-mirrors.

Purpose of this study is to use adjustable platform for development of fiber diameter and fiber fusion from 125£gm to 50£gm,125£gm to 40£gm different taper single-mode fiber, the use of different process parameters in the design of fire taper models and parameters with the molten zone, the minimum loss of 0.77dB.After the large diameter quartz capillary tube inserted into some optical fiber taper changes made after the n¡Ñ1 optical combiner, and adjusted through the design taper model parameters reduce the firepower some fiber transmission loss. In recent years, the application of high-power fiber laser in various industries is widely spreading and exploring. Within the system, one of critical component is the fiber pump combiner. We are currently investigating the fabrication of 7x1 Combiner with both single mode and multimode fibers and the characterization of combiner efficiency as a function of processing. The development of 7¡Ñ1 single-mode fiber combiner loss of about 1.5dB and 7 ¡Ñ 1 multimode fiber combiner loss of about 1.4dB

No description available.

Initial investigations were conducted to determine the feasibility of applying a post solution heat treatment stress relief stretching operation to near-net-shaped taper rolled aerospace aluminium plate, in terms of the possible process window and the impact on key mechanical properties. Finite element modelling (FEM) and simulations, validated using digital image correlation to measure the strain distribution in flat tapered tensile specimens, have demonstrated the existence of a suitable process window for the production of near-net-shape wing skin blanks. It was revealed that the limits of the available taper geometry are dictated by the work hardening behaviour of the specific aluminium alloy. In addition, in the case of two typical upper wing skin alloys AA2195 and AA7055, tensile and toughness testing revealed that the resultant strain gradient offers the potential for graded mechanical properties suited to this application, with a higher level of toughness at the wing root and an increase in the yield strength of the material at the wing tip. Further, investigations explore the effect of increased tensile pre-stretching, to the maximum achievable before tensile instability, on the strength, microstructure, and precipitation kinetics seen during ageing alloys AA2195 and AA7055. Subsequently, in both alloys, microstructure data have been used to deconvolute and model the effects of increasing pre-strain on the main strengthening components that contribute to the T8 yield strength of the material. In the case of the AA2195 alloy, the T8 yield strength was observed to increase continually as a function of pre-strain to a maximum value of ~670MPa at 15%. It was shown that refinement of the T1 phase continued to the maximum obtainable pre-strain, which was predicted to result in a reduction in the precipitate strengthening contribution. The increase in the T8 yield strength resulting from high levels of pre-strain was attributed to a large increase in residual strain hardening following artificial ageing, owing to a low level of recovery. In the AA7055 alloy, increased pre-strain led to a substantial increase in the T3 yield strength, which was revealed to be due to the dynamic precipitation of GP-Zones. In the T8 temper the yield strength of the alloy increased continually as a function of pre-strain to a maximum of ~607MPa at 24%. Increasing pre-strain was shown to result in a continual and significant increase in the residual strain hardening contribution to the alloys T8 yield strength, due to the occurrence of limited recovery. However, it was also shown that increasing pre-strain led to a progressive reduction in the precipitate strengthening contribution from the eta prime phase, due to an increase in the volume fraction of precipitate free zones (PFZs) with increased dislocation density. Therefore, the increase in the T8 yield strength, as a function of pre-strain, is attributed to an increased residual strain hardening contribution which outweighs a smaller progressive reduction in the precipitate strengthening contribution.

The purpose of this study is to use multi-functional optical fiber processing platform produce 2X2 single-mode fiber coupler, and use theory and simulation to analyze, as the basis of the starting, development of novel fused coupler device. The characteristics of this coupler is a 2x2 single-mode fiber coupler in which a single-mode fiber replaced by our laboratory to manufacture the capillary fiber. The use of this coupler is similar to the use of single-mode fiber refractive index of the solution pumped capillary fiber to a liquid switch fiber coupler. We know that the refractive index decreases as the wavelength increases, the slope of the different materials for this change is different, and due to the different materials, the thermal coefficient of refractive index is different, so we can be found in the case of different temperatures, the refractive index of the two materials are equal, and other wavelength is different, therefore, only when the same refractive index of the wavelength in order to fully coupled. The advantages of this coupling is temperature control of its maximum coupling wavelength range, and the capillary fiber core is liquid, we can use this measurement technique for the development of liquid, if the later then the single-mode fiber to replace the other refractive index different fiber, you can use this method to measure the other liquid. Next, use simulation software to simulate this coupler, the coupling wavelength and coupling efficiency values of the change in refractive index different cases, in order to facilitate the produce this novel fused coupler device.

Use the adjustable diameter fiber splicing platform to manufactured coupler, N fibers were put into the appropriate aperture silica capillaries, and then changed the taper model to manufactured fiber coupler [1], and adjusted the taper model and fusion parameters to reduce the fiber transmission loss and reduce the diameter of the fibers to achieve the optical coupling effect. We preferred to the Eisenmann & Weidel in 1988 [2]. It is a low loss of the fusion type equilateral triangle of 3¡Ñ3 fiber coupler. And we will study the asymmetric shape of an 3¡Ñ3 fiber coupler, the research method is the use of arc heating. The fiber has smaller heating area and the heating position which can be controlled. With the parameters which BeamPorp, we cut the fiber coupler and to discuss its cross-section. By the different geometric distribution of fibers, and the core spacing, we discuss the spectra of the OSA to change the coupling site. We changed the interior structure to make the power coupling to a marked effect; if we could control the asymmetric coupler explicitly then we could achieve the transmission power [3], power coupling, and the multiple spectra of light.