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Optical coherence tomography (OCT) is a noninvasive, three-dimensional imaging technique that offers close-to-histology-level image quality. Based on broadband spectral interferometry, OCT has enabled clinical applications ranging from ophthalmology to cardiology that revolutionized in vivo medical diagnostics. Considering the size and cost of a commercial OCT system, it is essential to investigate different approaches for realizing a compact and low-cost OCT system in order to make it accessible to a significantly larger group of applications and users. Exploiting integrated optics, several central components of an OCT system have been assembled on a microchip so far. Silicon based designs have the advantage of complementary metal-oxide-semiconductor (CMOS) compatible high-volume production while indium phosphate (InP) based designs have the possibility of monolithic integration of the light source and the detector with other components. In this chapter, the design considerations, theoretical analysis and experimental results of the passive integrated optical components of an on-chip OCT system including interferometer, spectrometer, reference arm, and sample arm will be presented. Active components (light source and detectors) are beyond the scope of this chapter.

We report on a comparison between piezoelectric and interferometric readouts of vibrations in quartz tuning forks (QTFs) when acting as sound wave transducers in a quartz-enhanced photoacoustic setup (QEPAS) for trace gas detection. A theoretical model relating the prong vibration amplitude with the QTF prong sizes and electrical resistance is proposed. To compare interferometric and piezoelectric readouts, two QTFs have been selected; a tuning fork with rectangular-shape of the prongs, having a resonance frequency of 3.4 kHz and a quality-factor of 4,000, and a QTF with prong having a T-shape characterized by a resonance frequency of 12.4 kHz with a quality-factor of 15,000. Comparison between the interferometric and piezoelectric readouts were performed by using both QTFs in a QEPAS sensor setup for water vapor detection. We demonstrated that the QTF geometry can be properly designed to enhance the signal from a specific readout mode. Keywords: Photoacoustic spectroscopy, Tuning fork, Piezoelectricity, Interferometry, Gas sensing

The interaction of the enantiomers of the non-steroidal anti-inflammatory drug naproxen (NPX) with human serum albumin (HSA) has been investigated using fluorescence and phosphorescence spectroscopy in the steady-state and time-resolved mode. The absorption, fluorescence excitation, and fluorescence emission spectra of (S)-NPX and (R)-NPX differ in shape in the presence of HSA, indicating that these enantiomers experience a different environment when bound. In solutions containing 0.2 M KI, complexation with HSA results in a strongly increased NPX fluorescence intensity and a decreased NPX phosphorescence intensity due to the inhibition of the collisional interaction with the heavy atom iodide. Fluorescence intensity curves obtained upon selective excitation of NPX show 8-fold different slopes for bound and free NPX. No significant difference in the binding constants of (3.8 ± 0.6) 105 M1 for (S)-NPX and (3.9 ± 0.6) 105 M1 for (R)-NPX was found. Furthermore, the addition of NPX quenches the phosphorescence of the single tryptophan in HSA (Trp-214) based on Dexter energy transfer. The short-range nature of this mechanism explains the upward curvature of the Stern–Volmer plot observed for HSA: At low concentrations NPX binds to HSA at a distance from Trp-214 and no quenching occurs, whereas at high NPX concentrations the phosphorescence intensity decreases due to dynamic quenching by NPX diffusing into site I from the bulk solution. The dynamic quenching observed in the Stern–Volmer plots based on the longest phosphorescence lifetime indicates an overall binding constant to HSA of about 3 105 M1 for both enantiomers. 201, The authors thank Dr. Gert van der Zwan for stimulating discussions, Kim van den Boom for assistance with the time-resolved fluorescence measurements, the Dutch Foundation for the Advancement of Science (NWO-CW ECHO Grant No. 700.55.014 to I.L.) and the Spanish government (Ramon y Cajal contract RyC-2007-00476 to V.L-V.) for financial support. V.L.-V.'s visit to LaserLaB VU Amsterdam was made possible through the access program of Laserlab-Europe, EU-Integrated Infrastructures Initiative contract 2008-1-228334, project lcvu001484.

Ytterbium-doped yttrium aluminum garnets (Yb:YAG) are known as IR laser crystals. Previously, we have shown that they are also fast scintillators in the near UV region. In this work we report on the measurements of I R scintillation properties of Yb(10%):YAG crystal. It emits at room temperature at 1.03 mum with a light yield of (79+/-8) x 103 photons/MeV and a decay time of 1.9 ms when excited by 90 keV electrons. With decreasing temperature both light yield and decay time decrease. (C) 2001 Elsevier Science B.V. All rights reserved.

Infrared emission induced by ionizing particle has been observed in liquid Ar and liquid Xe. The phenomenon seems to be similar to the one recently observed in dense noble gases. (C) 2000 Elsevier Science B.V. All rights reserved.

The uptake of polycyclic aromatic hydrocarbons (PAHs) by fish can be determined by screening the gall bladder bile for PAH metabolites. Conjugated 1-hydroxy pyrene is a major metabolite in bile of fish exposed to PAH polluted sediment. Synchronous fluorescence spectrometry is presented as a rapid screening technique for the determination of this compound; the complete analysis takes only 2–3 min. HPLC with fluorescence detection was used to validate the assay. Calibration methods, using either free 1-hydroxy pyrene or the pyrene-1-glucuronide conjugate as a reference standard, were investigated. The technique was applied to a mesocosm study in which the uptake of PAHs by flounder ( Platichthys flesus ) from polluted sediment was studied. Direct contact with the sediment proved the most important factor; the uptake through water phase or diet was less significant. The usefulness of 1-hydroxy pyrene analysis in bile as a monitoring tool for PAH exposure is discussed.

We report on measurements of the light yield, emission spectrum, and time response of YAG:Yb crystals. The temperature dependence of light yield was investigated. Data show that YAG:Yb crystals are good scintillators, suitable for applications to neutrino detection and spectroscopy. (C) 2001 Elsevier Science B.V. All rights reserved.