We propose a novel application of optical coherence tomography (OCT) to monitor pit formation in laser irradiated optical storage materials. A multilayer optical storage recordable compact disk, is composed of multiple layers, each of different structure. Disks were irradiated with a Q-Switched Nd:YAG laser with an energy of 373 mJ. Post-irradiated disks were evaluated by OCT and those images were compared with optical microscopy. Our results indicate that OCT is a useful instrument to investigate pit formation in multilayer optical storage disks and might also provide information to optimize optical memory technology.

Novel multi-wavelength switching filters based on cascaded long-period fiber grating (LPG) and polarization-maintaining fiber (PMF) in a Sagnac loop configuration are proposed and experimentally demonstrated. While the multi-channel spectrum of PMF Sagnac loop filter is controlled by the polarization state in the loop, the polarization-independence of the LPG filter is used to drop one channel. The polarization-independence of the cascaded LPG filter is also used for the fixed periodic loss spectrum to drop multiple channels in the loop. Although the polarization state of the optical wave filter is switched by the electro-optic modulator in the loop, the device is independent of the polarization state of the input light due to the bi-directional polarization compensation of the Sagnac loop interferometer. This device can be used to achieve all-channel gating and odd/even-channel switching with fine channel selectivity and high speed response.

Selection of infrared (IR) detector is a key consideration in designing an experimental setup for temperature depth profiling using pulsed photothermal radiometry (PPTR). In addition to common detector characteristics, such as the spectral response, detector noise, and response speed, application-specific details must be taken into account to ensure optimal system performance. When comparing detectors with different spectral responses, blackbody emission characteristics must be considered in terms of influence on radiometric signal amplitude, as well as on background shot noise. In PPTR, optical penetration depth of the sample in the acquisition spectral band is also an important factor, affecting the stability of the temperature profile reconstruction. Moreover, due to spectral variation of IR absorption coefficient in watery tissues, the acquisition band must be appropriately narrowed to ensure the validity of the customary approximation of a constant absorption coefficient value in signal analysis. This reduces the signal-to-noise ratio, adversely affecting the stability and quality of the temperature profile reconstruction. We present a performance analysis of PPTR depth profiling in human skin using commercially available IR detectors (InSb, HgCdTe), operating in different spectral bands. A measurement simulation example, involving a simple, hyper-Gaussian temperature profile, and realistic noise levels, illustrates their expected performance.

Background and Objectives: Pulsed dye laser (PDL) irradiation is the standard clinical treatment for vascular lesions. However, PDL treatment of port wine stain birthmarks (PWS) is variable and unpredictable. Photodynamic therapy (PDT) using benzoporphyrin derivative monoacid ring A (BPD) and yellow light may induce substantial vascular effects and potentially offer a more effective treatment. In this study, we utilize a rodent dorsal skinfold model to evaluate the vascular effects of BPD-PDT at 576 nm as compared to PDL. Study Design/Materials and Methods: A dorsal skinfold window was created on the backs of female Sprague-Dawley rats, allowing epidermal and subdermal irradiation and subdermal imaging. One mg/kg BPD was administered intravenously via a jugular venous catheter. Study groups were: control (no BPD, no light), PDL (585 nm, τ p 1.5 ms, 10 J/cm 2), and PDT (BPD + continuous wave irradiation (CW) at 576nm, τ p 16 min, 96 J/cm 2). Vessels were imaged and assessed for damage using laser speckle imaging (LSI) before, immediately after, and 18 hours post-intervention. Results: Epidermal irradiation was accomplished without blistering, scabbing or ulceration. PDL and PDT resulted in similar reductions in vascular perfusion 18 hours post-intervention (34.6% and 33.4%, respectively). Conclusions: BPD-PDT can achieve safe and selective vascular effects and may offer an alternative therapeutic option for treatment of hypervascular skin lesions including PWS birthmarks.