Pyroelectric-controlled bending of a self-trapped optical beam in a photorefractive iron doped lithium niobate crystal

We present the experimental demonstration of a self-trapped optical beam bending in a photorefractive Fe-doped lithium niobate (LN:Fe) crystal controlled by the pyroelectric effect. Formation of self-trapped beams with typical [Formula: see text]50[Formula: see text][Formula: see text]m diameter and large bending of [Formula: see text]140[Formula: see text][Formula: see text]m are depicted in a 1[Formula: see text]cm length LN:Fe crystal for a laser beam at 632.8[Formula: see text]nm wavelength and 0.5[Formula: see text]mW power with a 30∘C crystal temperature change. The self-trapped beam bending is opposite to the crystal [Formula: see text]-axis. The underlying physics is elaborated and numerical simulations are performed. The long-living waveguiding channels with controlled curvilinear trajectories are promising for optical information routing.

Long Duration Uniform Crystal Temperature Sensor Application in Industrial Gas Turbine for Cooling Design Validation

This paper describes an in-situ validation of advanced cooling designs for turbine airfoils using high accuracy Uniform Crystal Temperature Sensors (UCTS). This was achieved by running a rainbow test of UCTS instrumented parts with different cooling designs in an industrial gas turbine in commercial operation for a period exceeding 6 months. Test results provided valuable information on the cooling performance benefits of the improved design, as well as on different thermal barrier coatings tested as part of the rainbow configuration. This paper presents the comparison between empirical and analytical results. The real engine environment presented obvious challenges to the validation effort, which assumes high accuracy experimental data from a well-controlled test as the basis for comparison. To get as close as possible to this high standard, sources of variation and uncertainties were identified and accounted for in the preparation of the test campaign. This paper describes these in some detail, providing a useful model to practicing engineers. Survival and timeliness of the results were also a concern. Expert installation and removal of the micro-sized crystal sensors was a key contributing factor to the sensor survival. Automated, quality controlled post processing, which correlated changes in the crystal structure and the time history of testing with temperature, enabled accurate reporting of the maximum temperature experienced during the full length of the test for each crystal. The results show excellent agreement between the UCTS reported temperature and the Conjugate Heat Transfer (CHT) model predictions. Hence the experimental results validated the advanced cooling design configuration. Additionally, this case study demonstrates that UCTS is a well suited non-intrusive, accurate and practical technique applicable for long duration in-situ temperature measurements of turbine components in the conditions most representative of the engine.