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International audience; Accurate prediction of resistances at the transistor’s access zone and their temperature dependency are very important, since the current flow to the device depends on that region. In this paper, we have modeled the access resistances and have verified their temperature dependency with the experimental results in the case of a 0.25 μm gate GaN HEMT. At first, the carrier concentration profile and its mobility associated with the two-dimensional electron gas (2-DEG) were evaluated to model these resistances. Also, we have measured the threshold voltage and have studied its temperature dependence in this estimation process. Apart from that, thermal resistance and its change with temperature were investigated, as it is an important factor in describing the 2-DEG transport mechanism. We also estimated the variation of channel temperature for nine different temperatures (from 233 to 423 K) and validated the output with the measured data. The studied results can be used for the prediction of GaN HEMTs characteristics with temperature variation and can be included in the simulation packages.

In this paper, we have investigated the channel temperature and thermal sensitivity for a 0.15 μm gate GaN HEMT at nine different temperatures from 233 K to 423 K. The estimation of channel temperature has been accomplished by means of DC and pulse measurement and it was later well verified with modelled data. Using that measured and theoretical data, the thermal resistance for the device is also estimated and compared with those published in open literature. The investigation was further extended to study the thermal-sensitivity of the DC and small signal parameters by means of on-wafer measurement in relation to room temperature. Temperature has a variety of effects based on the selected operating condition, the bias point is selected to achieve highest gain in the case of intrinsic parameters. As will be shown, different trends are observed for the extrinsic and intrinsic parameters but the temperature has a greater impact on the resistances.

International audience; The goal of this paper is to provide a comparative analysis of the thermal impact on the microwave performance of high electron-mobility transistors (HEMTs) based on GaAs and GaN technologies. To accomplish this challenging goal, the relative sensitivity of the microwave performance to changes in the ambient temperature is determined by using scattering parameter measurements and the corresponding equivalent-circuit models. The studied devices are two HEMTs with the same gate width of 200 µm but fabricated using different semiconductor materials: GaAs and GaN technologies. The investigation is performed under both cooled and heated conditions, by varying the temperature from −40 °C to 150 °C. Although the impact of the temperature strongly depends on the selected operating condition, the bias point is chosen in order to enable, as much as possible, a fair comparison between the two different technologies. As will be shown, quite similar trends are observed for the two different technologies, but the impact of the temperature is more pronounced in the GaN device.

The main objective of this work is to design and construct a PoE switch based system: to control electric appliances such as light, fan, heater, washing machine, motor, TV, etc. and simultaneously data communication facility. Especially PoE switch can manage power and data separately by a splitter which motivated the need to research into it not only for industrial application but also for domestic use or home use. Power is use for controlling devices and data is for communication purpose. This system will play an important role for the elderly and physically disabled people to control their home appliances in intuitive and flexible way through Wi-Fi and internet. This system is password protected so only authorized person can control any sensitive electrical appliances. Most commercially available home automation systems are used only for control purpose. But by our proposed PoE based system we can control electrical appliances as well as data communication by the same switch port.

Signal routers are novel photonic components that ensure communication between a large numbers of optical networks. In this paper we present the construction of 1×N router by using 2×2 Mach-Zehnder interferometer electro-optic switches operating at 1.55 µm. The 2×2 Mach-Zehnder Interferometer (MZI) electro-optic switches in the routers are made by titanium diffused potassium niobate (Ti:KNbO 3 ) and the results of the routers were compared with titanium diffused lithium niobate (Ti:LiNbO 3 ) based routers to ease the choice of materials in implementing large networks. Enhanced performance of a single switch was evaluated at first to obtain reduced insertion loss, high extinction ratio & low excess loss. Then we implemented the 1×2, 1×4, 1×8 and 1×16 routers using that optimized switches. We can switch the input optical power to each of the output ports of the routers by the application of applied voltage at each second electrode of the MZI switches. The originality of this work is to introduce Ti:KNbO 3 waveguide in the design of signal router. The simulation is done and also outputs are calculated by using OptiBPM12.2 simulation software.

Optical logic gates have become the most essential means of performing optical signal processing functions. These gates have potential for the development of large scale integrated optical processor. In this paper we tried to bring out the best performance of AND, NOT, NAND, NOR, XOR, XNOR logic gates based on electro-optic effect by implementing these devices with the use of Ti:KNbO 3 waveguide. To implement these gates we used an optimal performing 2×2 Mach-Zehnder Interferometer electro-optic switch based on Ti:KNbO 3 waveguide as basic building block. Two or more switches were needed for designing the gates. Signals in second electrodes which are also referred as control signals are the inputs of the gates. The novelty of this work is to introduce AND, NOT, NAND, NOR, XOR, XNOR logic gates using Ti:KNbO 3 based waveguides at 1.55 μm. Finite difference beam propagation method (FDBPM) was used as the performance analyzing tool of these gates with the help of Opti-BPM 12.2 simulation software.

Electro-optic Mach-Zehnder interferometer (MZI) switches are well known devices in optical systems for their high speed of operation. In next generation optical network, such switches have wide applications due to their high switching capability and great reliability. In this paper we have investigated the enhanced performance of an electro-optic switch made by titanium diffused lithium niobate (Ti:LiNbO3) functioned as waveguide medium based on integrated Mach-Zehnder interferometer (MZI) at 1.55 μm wavelength. The performance of the switch is optimized for low switching voltage, low insertion loss, high extinction ratio. This is done by varying the strip thickness of titanium, interferometer arm length, arm gap, waveguide width, gap in the coupling region of the 3 dB couplers, and center position of second electrode deposited on integrated Mach-zehnder Interferometer arm with respect to the original axis of the switch. The designed switch gives lowest insertion loss of 0.00881dB and highest extinction ratio of 33.581 dB at 8.8 V.

The multimode interference (MMI) coupler is a versatile component for photonic signal processing applications. In present day, research scenarios based on low-index-contrast MMI couplers give more scope of study as it has certain advantages over high-index-contrast MMI couplers. In this work we presented an optimal design for the low-index-contrast MMI coupler. From various possible structures, we considered Silica-on-Silicon based 4×4 MMI coupler. Various techniques such as conventional self imaging, improved self-imaging and Genetic algorithm are used here, with numerical analysis such as mode propagation analysis, beam propagation method for evaluating optimal performance by adjusting the parameters of the structure. The optimum structure is finally selected one from them by comparing the results of these different techniques.

In recent years, the silica-on-silicon based multimode interference (MMI) optical waveguide is an interesting research topic. It is being advanced various researches on the silica based MMI coupler. This paper represents the considerations of the optimal design of the silica-on-silicon based MMI optical coupler for better performance. For that, we have illustrated the simulation results on a particular case of the 4×4 silica-on-silicon based MMI coupler. From the simulation results, it is seen that the performance of the MMI coupler depends on multiple width and length combinations of the MMI waveguide. The results also show that the width of the multimode waveguide could not be too small or too large for optimal performance, and at the widths, 100 µm, 120 µm and 130 µm, the performance could be optimized and be almost 0.62 - 0.64 in a given length range. Finally, the results have been compared with the optical coupler presently available in the market and show that the silica-on-silicon based MMI coupler is much more efficient in terms of losses and the performance associated with it and the size of the coupler.