Measurement of the thickness and refractive index of a thin film by analyzing reflected interference fringes.

We propose a novel, to the best of our knowledge, method to estimate the thickness and refractive index of a thin film by analyzing the reflectance as a function of the incidence angle. In most cases, interference fringes cannot be obtained from a film within a practical angular range unless it is much thicker than the wavelength. This problem was solved by adopting a high-index material as the medium of incidence, in which case several cycles of interference fringes were observed within a small range of incidence angles near the critical angle, allowing a fringe analysis. Consequently, the thicknesses, as well as the refractive indices of dielectric thin films, could be estimated. Our proposed method gave uncertainties of 20 nm and 0.0004 for the thickness and refractive index measurements, respectively.

Interference of two diverging beams reflected from a plane parallel plate: stationary fringes with characteristic stable period.

We investigated interference fringes due to superposition of diverging light waves reflected from the two sides of a plane parallel plate. A non-localized fringe pattern of high contrast was obtained as a function of incident angle when we used a coherent diverging beam. We found that the fringe density increased to a certain angle and then decreased thereafter, against the common belief that the fringe density increases monotonically with the angle of incidence. Because the fringe density is maximum at this angle and does not change rapidly in the vicinity, we could employ Fourier analysis to estimate interferometric parameters, such as thickness, refractive index, and wavelength, that determine the characteristic stationary fringe density.

Electrical Reliability and Bending Test Methodologies of Metal Electrode on Flexible Substrate.

To develop highly reliable flexible electronics, mechanical reliability during mechanical deformation such as repeated bending is an important issue. Bending test methodologies to estimate long-term reliability during repeated mechanical deformation are attracting substantial interest from related researchers and industry insiders. In this study, four representative bending test methodologies for testing flexible electronics are introduced: free arc bending test, variable radius bending test, sliding plate test, and variable angle test. Correct name and characteristics of each method are also explained. Furthermore, electrical reliability of Cu film on polymer substrate samples was investigated in each bending test method through in situ monitoring of electrical resistance. With different bending test methodologies, different electrical resistance changes were observed. Fatigue damages occurred at different areas. Obtained electrical reliability and failure modes were analyzed by observing crack morphologies.

Speckle noise reduction on a laser projection display via a broadband green light source.

A broadband green light source was demonstrated using a tandem-poled lithium niobate (TPLN) crystal. The measured wavelength and temperature bandwidth were 6.5 nm and 100 °C, respectively, spectral bandwidth was 36 times broader than the periodically poled case. Although the conversion efficiency was smaller than in the periodic case, the TPLN device had a good figure of merit owing to the extremely large bandwidth for wavelength and temperature. The developed broadband green light source exhibited speckle noise approximately one-seventh of that in the conventional approach for a laser projection display.

Evaluation of domain randomness in periodically poled lithium niobate by diffraction noise measurement.

Random duty-cycle errors (RDE) in ferroelectric quasi-phase-matching (QPM) devices not only affect the frequency conversion efficiency, but also generate non-phase-matched parasitic noise that can be detrimental to some applications. We demonstrate an accurate but simple method for measuring the RDE in periodically poled lithium niobate. Due to the equivalence between the undepleted harmonic generation spectrum and the diffraction pattern from the QPM grating, we employed linear diffraction measurement which is much simpler than tunable harmonic generation experiments [J. S. Pelc, et al., Opt. Lett.36, 864-866 (2011)]. As a result, we could relate the RDE for the QPM device to the relative noise intensity between the diffraction orders.

Nondestructive quality evaluation of periodically poled lithium niobate crystals by diffraction.

Quasi-phase-matching devices are usually fabricated by electric field poling over photolithographically defined electrode patterns on ferroelectric crystal substrates. For the optimal nonlinear optical performance of such devices, the micro-poled domain structure must ensure good fidelity to the designed grating structure. We present a nondestructive diffraction method to evaluate the quality of periodically poled lithium niobate crystals, by utilizing index modulation caused by the internal field effects. Our proposed method is much simpler than the conventional second-harmonic generation experiment, and provides a fast, low-cost but accurate means for micro-poling quality evaluation.

Doxorubicin-induced reactive oxygen species generation and intracellular Ca2+ increase are reciprocally modulated in rat cardiomyocytes.

Doxorubicin (DOX) is one of the most potent anticancer drugs and induces acute cardiac arrhythmias and chronic cumulative cardiomyopathy. Though DOX-induced cardiotoxicity is known to be caused mainly by ROS generation, a disturbance of Ca2+ homeostasis is also implicated one of the cardiotoxic mechanisms. In this study, a molecular basis of DOX-induced modulation of intracellular Ca2+ concentration ([Ca2+]i) was investigated. Treatment of adult rat cardiomyocytes with DOX increased [Ca2+]i irrespectively of extracellular Ca2+, indicating DOX-mediated Ca2+ release from intracellular Ca2+ stores. The DOX-induced Ca2+ increase was slowly processed and sustained. The Ca2+ increase was inhibited by pretreatment with a sarcoplasmic reticulum (SR) Ca2+ channel blocker, ryanodine or dantrolene, and an antioxidant, alpha-lipoic acid or alpha-tocopherol. DOX-induced ROS generation was observed immediately after DOX treatment and increased in a time-dependent manner. The ROS production was significantly reduced by the pretreatment of the SR Ca2+ channel blockers and the antioxidants. Moreover, DOX-mediated activation of caspase-3 was significantly inhibited by the Ca2+ channel blockers and a-lipoic acid but not a-tocopherol. In addition, cotreatment of ryanodine with alpha-lipoic acid resulted in further inhibition of the casapse-3 activity. These results demonstrate that DOX-mediated ROS opens ryanodine receptor, resulting in an increase in [Ca2+]i and that the increased [Ca2+]i induces ROS production. These observations also suggest that DOX/ROS-induced increase of [Ca2+]i plays a critical role in damage of cardiomyocytes.

Broadband optical parametric amplification at the communication band with periodically poled lithium niobate.

We report broadband optical parametric generation (OPG) in a single periodically poled lithium niobate crystal with a picosecond pump pulse at a fixed wavelength. We also demonstrate efficient optical parametric amplification of a broadband seed pulse within the quasi-phase-matched OPG band. The broad parametric gain band is attributed to group-velocity matching and degeneracy between the signal and idler, and the broad spectral width of the pumping source.