A hybrid structure composed of organic and inorganic piezoelectric fibrous material was developed as a flexible and stretchable pressure sensor. A separately sprayed configuration has the best performance for low frequency and low-pressure conditions.

Resonant optical mode excitations in semiconductor nanowires result in enhanced absorptions. Nominally, only the diameter dependent radial mode excitations have been considered for the increased absorption. In this paper, we try to understand how the length of the nanowires affects the resonant wavelength and peak absorption wavelengths. We answer two questions viz (1) at what minimum length are radial optical modes stabilized and dominate the absorption characteristics and (2) do longitudinal modes play a role in absorption characteristics especially in determining the resonant wavelength. Two different semiconductors are studied viz silicon and gallium arsenide. We find that even nanowires as short as 200 nm exhibit absorption characteristics dominated by the radial mode excitation. However, for lengths smaller than 200 nm, the optical characteristics are dominated by scattering. Further, we observe that longitudinal modes are excited in low absorption semiconductor materials like silicon for lengths up to 700 nm and the absorption peak depends both on the diameter and the wavelength. Further, shorter length nanowires may have higher absorption than the longer ones in this regime. We also observed that scattering from the nanowires is less than 2% of the incident light. For higher absorption semiconductor like GaAs, absorption characteristics are mainly determined by the radial mode excitations even for shorter lengths. The results provide further insight into the radial mode excitations in semiconductor nanowires.

In this paper we simulate and analyze a sample of slow light semiconducting device with In Ga As GaAs 0.25 0.75 / quantum dot structure based on coherent population oscillation (CPO). The simulation is conducted to enhance the main parameters of slow light device and a method is presented for setting the output specifications of this kind of devices. In this paper, we deal with changing the size of quantum dot to find the ideal size. The simulation results indicate that as the size of quantum dot changes properly (with reducing more than 50 percent of quantum dots both radius and height), then the slope of diagram of the real part of refractive index increases significantly so that the Slow Down Factor (SDF) predicted to be18 times greater. Analysis and simulations based on cylinderical quantum dots structure In Ga As GaAs 0.25 0.75 / slow light devices based on exitonic cpo.

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A method based on extraction of effective absorption coefficient using Beer-Lambert’s law on simulated transmissions is used to understand optical absorption characteristics of semiconductor nanowire arrays. Three different semiconductor nanowire arrays viz. silicon (Si), gallium arsenide (GaAs), and amorphous silicon (a-Si) were evaluated using the method. These semiconductors are chosen since two of them have similar real parts of the refractive index in the visible range, while the other two have comparable imaginary parts of the refractive index in the visible range. In this way, we can examine the role of the real and imaginary part of the refractive index in enhancing the absorption characteristics in nanowire arrays due to the excitation of radial and photonic Bloch modes. We have observed that high absorption peaks at modal resonances also correspond to resonance peaks in reflections from the nanowire-air interface. Further, the wavelengths of these two peak resonances are slightly detuned according to the Kramers-Kronig relation for an oscillator system. The study confirms that the resonance wavelengths of radial HE modes are diameter and refractive index dependent. The study extends the understanding to the absorption characteristics due to the excitation of the photonic Bloch modes due to near field coupling. Excitation of Bloch modes leads to increased absorption and quality factor as compared to only the radial mode excitation. We also conclude that the imaginary part of the refractive index of the semiconductor influence the diameters at which Bloch modes are excited for a given lattice spacing. We observed that semiconductors with a higher bulk value of absorption coefficient need to be ordered denser in the nanowire array to be able to excite the photonic crystal modes within the array. Interestingly, we have seen that for Si, GaAs, and a-Si arrays with an equal diameter of 80 nm and lattice spacing of 400 nm, the peak absorption is almost the same, even when GaAs and a-Si are highly absorptive materials compared to the Si. Thus, both radial and Bloch mode excitations can be used to design absorption profiles in a semiconductor nanowire array.

This paper demonstrates the effects of applying magnetic and electric fields and physical dimensions alterations on AlGaAs/GaAs multiple quantum well (QW) slow light devices. Physical parameters include quantum well sizes and number of quantum wells. To the best of our knowledge, this is the first analysis of the effects of both applying magnetic/electric fields and physical parameters alterations and the first suggestion for matching the prefabrication and post fabrication tuning of the slow light devices based on excitonic population oscillations. The aim of our theoretical analysis is controlling the optical properties such as central frequency, bandwidth, and slow down factor (SDF) in slow light devices based on excitonic population oscillation to achieve better tuning. To reach these purposes, first we investigate the quantum well size and number of quantum wells alteration effects. Next, we analyze the effects of applying magnetic and electric fields to the multiple quantum well structure, separately. Finally, physical parameters and applied external fields are changed for measuring frequency shift and SDF for coherent population oscillation slow light devices. The results show the available central frequency shifts in about 1.6 THz at best. Also the SDF value improvement is about one order of magnitude. These results will be applicable for optical nonlinearity enhancements, all-optical signal processing, optical communications, all-optical switches, optical modulators, and variable true delays.

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