An optical sensor to be used for gas pressure detection is described. The device is based on the spectral response associated with the surface plasmon resonance (SPR) occurring on a 50-nm gold surface. The operation of the device relies on the fact that the refractive index of a gas changes with pressure, which leads to a shift in the resonance wavelength dip SPR in the SPR curve. Experiments performed on nitrogen gas at room temperature demonstrated the sensor resolution of 4.4×10–5 RUI, which corresponds to a pressure resolution of 16 kPa. The new device offers the benefits of wide dynamic range, no moving parts, and possibly 2-D imaging of pressure distribution. Further development of the device may lead to a new type of optical pressure sensors.
We report a 2-dimensional surface plasmon resonance (SPR) imaging array sensor based on differential phase measurement between p- and s-polarization. This parallel detection provides the advantage of high-throughput sensing, which is essential in recent biosensing technology. In the differential measurement approach, the signal (p) and reference (s) beams go through exactly identical optical path. This greatly improves the phase detection stability. In the present setup we use a low-cost imaging device and a simple data analysis program to perform the required arrayed sensing operation. The system demonstrates a refractive index resolution of 1x10<sup>-4</sup> RIU per degree phase change.
Lattice-matched In<sub>0.53</sub>Ga<sub>0.47</sub>As/InP quantum well (QW) structures are of considerable interest in photonic application since they enabled device operation in the 1.3micrometers to 1.55micrometers wavelength range which is of importance for optical communication systems. The process of interdiffusion modifies the as-grown square QW to a graded QW which alter the subband structure and optical properties of the QW. Thus it provides a useful tool for bandstructure engineering. The interdiffusion process of InGaAs/InP QW provides more degrees of freedom than AlGaAs/GaAs QW system since interdiffusion can occur for group-III, group-V, and groups III plus V together. These are determined by the temperature and chemical environment used during annealing of the QW structure. The effect of interdiffusion on the laser performances of InGaAs/InP QWs is also studied based on these different types of diffusion processes. It is found that the operating wavelength shows both a red shift and a blue shift depending on the types of diffusion process. It is also found that group-III interdiffusion gives the best performance of InGaAs/InP QW laser when comparing to the other tow types of interdiffusion in terms of a smaller threshold carrier density.