Oxygen and carbon dioxide sensors are involved in many chemical and biochemical reactions. Consequently, considerable efforts over years have been devoted to discover and improve suitable techniques for measuring gas concentrations by optical fiber sensors. Optical gas sensors consist of a gas-sensitive dye entrapped in a matrix with a high permeability to gas. With such sensors, gas concentration is evaluated based upon the reduction in luminescence intensity caused by gas quenching of the emitting state. However, the luminescence quenching effect of oxygen is highly sensitive to temperature. Thus, a simple, low-cost plastic optical fiber sensor for dual sensing of temperature and oxygen is presented. Also, a modified Stern-Volmer model is introduced to compensate for the temperature drift while the temperature is obtained by above dual sensor. Recently, we presented highly-sensitive oxygen and dissolved oxygen sensors comprising an optical fiber coated at one end with platinum (II) meso-tetrakis(pentafluorophenyl)porphyrin (PtTFPP) and PtTFPP entrapped core-shell silica nanoparticles embedded in an n-octyltriethoxysilane(Octyl-triEOS)/tetraethylorthosilane (TEOS) composite xerogel. Also, two-dimensional gas measurement for the distribution of chemical parameters in non-homogeneous samples is developed and is of interest in medical and biological researches.

A wavelength-selective but polarization-insensitive thermophotovoltaic emitter was numerically developed with a binary tungsten grating and its appealing emittance spectra were demonstrated with analysis. Ranges of emitter dimensions were preliminarily confined with the excitation of the surface plasmon polariton, cavity resonance, and Wood’s anomaly at specified wavelengths. Then, a hybrid scheme (the rigorous coupled wave analysis together with a genetic algorithm) was able to finely tailor the grating profile such that emittance could be significantly enhanced in the near infrared region. The peak emittance at the transverse electric and transverse magnetic polarizations was 0.997 and 0.935, respectively. The emittance was actually almost twice that from a plain tungsten plate at short wavelengths but significantly reduced at long wavelengths. Moreover, such spectral emittance is insensitive to the polarization and 5% dimension modification, making the emitter ideal for thermophotovoltaic applications. Patterns of electromagnetic fields and Poynting vectors were able to confirm the excitation of physical mechanisms.