Kotaro Tanaka

Cantilever Probe Integrated with Light-Emitting Diode, Waveguide, Aperture, and Photodiode for Scanning Near-Field Optical Microscope

A microfabricated scanning near-field optical microscope (SNOM) probe integrated with a light-emitting diode, waveguide, aperture, and photodiode is described. This probe includes all optical elements necessary for SNOM on the Si cantilever. By using a-Si as the core layer and SiO2 as the cladding layer, the process for fabricating the waveguide is compatible with that for fabricating the photodiode. The light is confirmed to transmit along the waveguide route with the large curvature. The obtained SNOM image shows a spatial resolution better than 200 nm.

Time-resolved measurements of low concentration aromatic hydrocarbons in diesel exhaust using a resonance enhanced multi-photon ionization method

Abstract Time-resolved measurements of the concentration of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in exhaust from a diesel vehicle fitted with an oxidation catalyst and operated in JE05 mode are performed at a sensitivity of 10 ppb using a supersonic jet/resonance enhanced multi-photon ionization (Jet-REMPI) method. The concentrations of benzene, naphthalene, and phenol in exhaust from the test vehicle are measured before entering and after exiting from the oxidation catalyst. The total hydrocarbon (THC) is measured simultaneously using a constant volume sample (CVS) instrument fitted with a flame ionization detector (FID). Concentration changes of benzene, naphthalene and phenol are recorded at 1 s intervals and quantified using standard samples. Comparison of these signals with the real-time THC data shows that the time dependence of the individual species is almost the same as that of the THC before the oxidation catalyst but substantially different after.

Mechanism of deposit formation on an electronic throttle body

The buildup of deposits on the electronic throttle body (ETB) used to control the intake air flow in an internal combustion engine causes various problems. To obtain information that can be used to prevent the buildup of such deposit, the characteristics and mechanism of the deposit formation were investigated by analysis of the components of the deposit, measurement of the distribution of the deposit thickness, and numerical analysis of the intake air flow. The deposit was found to comprise a complex of fuel and engine oil, high molecular components, and inorganic matter, with engine oil being the major component. The distribution of the deposit thickness was also observed to be similar to that of the temperature decrease across the butterfly valve, indicating that the temperature decrease was related to the deposit formation. In addition, it was established that the deposit component on the downstream side of the butterfly valve was transported very close to the butterfly valve by a circulatory flow. Based on the study results, it is postulated that the mechanism of the ETB deposit formation involves the initial transportation, by the blow-by gas, of hydrocarbons to the ETB air passage, where the hydrocarbons are condensed and adhere to the passage wall just behind the butterfly valve, owing to sudden drop in the air temperature under small valve opening angle conditions. The formed deposit subsequently builds up by attracting fuel, engine oil, combustion products, and suspended solids in the atmospheric air intake passing through the air cleaner.

Wavelength Modulation Spectroscopy Detection of N2O Using a Direct-Bonded Quasi-Phase-Matched LiNbO3-Ridge-Waveguide Mid-Infrared Laser

We measured nitrous oxide (N2O) concentration by mid-infrared wavelength modulation spectroscopy at a wavelength of 3.87 µm. Mid-infrared laser light from difference frequency generation in a fiber-coupled direct-bonded quasi-phase-matched LiNbO3-ridge-waveguide module is obtained using a diode-pumped Nd-doped yttrium alminum garnet (Nd:YAG) laser at 1064 nm together with a distributed feedback diode laser at 1466 nm. The absorption line of N2O centered at 2583.39 cm-1 (3.871 µm), which originates from the first overtone band of the ν1 asymmetric stretching mode, is measured by second-harmonic wavelength modulation spectroscopy detection. The limits of N2O detection measured by wavelength modulation spectroscopy are found to be 150 ppbv using a 29.9 m Herriott multipass cell at a pressure of 12 kPa. We demonstrated the real-time monitoring of atmospheric N2O using our developed spectrometer with a difference-frequency-generation mid-infrared laser light source.