Surface plasmon resonance based sensor for detection of different human blood groups in near infrared region is proposed. The plasmonic structure is based on fused silica or chalcogenide sulfide glass Ge20Ga5Sb10S65, commonly known as 2S2G. Experimental results describing the wavelength-dependent refractive index variation in multiple samples of different blood groups are considered for theoretical calculations. The angular interrogation method is considered. The sensor’s performance is closely analyzed in terms of its angular shift and curve width in order to predict the design consideration for simple and accurate blood-group identifier. The results are explained in terms of light coupling and plasmon resonance condition. Chalcogenide glass-based SPR structure is able to provide highly precise detection of different blood groups. The proposed low-volume blood sensor can be very useful for simple and reliable blood sample detection in medical application.

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We recently demonstrated orders of magnitude enhancement of two-photon absorption (2PA) in direct gap semiconductors due to intermediate state resonance enhancement for photons of very different energies. It can be expected that further enhancement of nondegenerate 2PA will be observed in quantum wells (QW's) since the intraband matrix elements do not vanish near the band center as they do in the bulk, and the density of states in QW's is larger near the band edge.Here we present a perturbation-theory based theoretical description of nondegenerate 2PA in semiconductor QW's, where both frequency and polarization of two incident waves can vary independently. Analytical expressions for all possible permutations of frequencies and polarizations have been obtained, and the results are compared with degenerate 2PA in quantum wells along with degenerate and nondegenerate 2PA in bulk semiconductors. We show that using QW's in place of bulk semiconductors with both beams in the TM-polarized mode leads to an additional order of magnitude increase in the nondegenerate 2PA. Explicit calculations for GaAs QW's are presented.

Abstract:We utilize the recently demonstrated orders of magnitude enhancement of extremely nondegenerate two-photon absorption in direct-gap semiconductor photodiodes to perform scanned imaging of 3D structures using IR femtosecond illumination pulses (1.6 µm and 4.93 µm) gated on the GaN detector by sub-gap, femtosecond pulses. While transverse resolution is limited by the usual imaging criteria, the longitudinal or depth resolution can be less than a wavelength, dependent on the pulsewidths in this nonlinear interaction within the detector element. The imaging system can accommodate a wide range of wavelengths in the mid-IR and near-IR without the need to modify the detection and imaging systems.

In this work, we have investigated the capability of different bimetallic nanoparticle alloy combinations to be used in fibre optic temperature sensing based on the technique of surface plasmon resonance (SPR). The metals considered for the present analysis are silver, gold and aluminium. The analysis is derived mainly from the thermo-optic effect along with some fundamental concepts of metal optics such as surface scattering, phonon-electron scattering and electron-electron scattering. The performance of the sensor with three different bimetallic nanoparticle alloy combinations is evaluated and compared, numerically, in terms of its sensitivity and accuracy. On the basis of the comparison and some logistic criterion, we predict the best possible bimetallic alloy combination along with a requisite alloy composition ratio that simultaneously provides higher values of both sensitivity and accuracy which is not possible with any single metallic nanoparticle layer.

Two-photon absorption, 2PA, in semiconductors is enhanced by two orders of magnitude due to intermediate-state resonance enhancement, ISRE, for very nondegenerate (ND) photon energies. Associated with this enhancement in loss is enhancement of the nonlinear refractive index, n2. Even larger enhancement of three-photon absorption is calculated and observed. These large nonlinearities have implications for applications including ND two-photon gain and twophoton semiconductor lasers. Calculations for enhancement of ND-2PA in quantum wells is also presented showing another order of magnitude increase in 2PA. Potential devices include room temperature gated infrared detectors for LIDAR and all-optical switches.

A fiber-optic surface plasmon resonance (SPR) sensor for the detection of human blood groups is proposed. Previous experimental results describing the wavelength-dependent refractive index variation of multiple samples of different blood groups are considered for theoretical calculations. The spectral interrogation method, along with silica fiber and silver layer, is considered. The sensor's performance is closely analyzed in terms of shift in SPR wavelength and SPR curve width in order to optimize the design parameters for a reliable and accurate blood-group identifier. The sensor design parameters include silver layer thickness, fiber core diameter, sensing region length, and temperature variation. The results are explained in terms of light coupling and plasmon resonance condition. The proposed sensing probe is able to provide high sensitivity and accuracy of blood-group detection, thereby opening an easy and reliable window for medical applications.

We present femtosecond pump-probe measurements of the nondegenerate (1960 nm excitation and 1176-1326 nm probe) two-photon absorption spectra of 8 nm GaAs/12 nm Al0.32Ga0.68As quantum well waveguides. Experiments were performed with light pulses co-polarized normal and tangential to the quantum well plane. The results are compared to perturbative calculations of transition rates between states determined by the k · p method with an 8 or 14 band basis. We find excellent agreement between theory and experiment for normal polarization, then use the model to support predictions of orders-of-magnitude enhancement of nondegenerate two-photon absorption as one constituent photon energy nears an intersubband resonance.