Eecs

We report an ultrahigh light extraction efficiency (LEE) light emitting diodes (LEDs) by incorporating innovative asymmetric obtuse angle microstructured surfaces. The quantitative simulations show that the LEE can be as high as 90% with realistic parameters. The physical mechanisms that enable such an ultrahigh LEE are also analyzed. It is believed that the main reasons are (1) the increased interaction surface area and (2) the better randomization effect by replacing the symmetric structure with the asymmetric obtuse angle structure. We also show that the proposed asymmetric obtuse angle microstructured surfaces are manufacturable. Experimental results also verify that a higher light extraction can be achieved by harnessing the asymmetric obtuse angle microstructured surfaces. Such an ultrahigh LEE can significantly increase the overall light efficacy of solid state lighting sources (SSL) and expedite the deployments of SSL sources

We report a new type of photoconductive semiconductor switch (PCSS), consisting of a semi-insulating gallium arsenic (GaAs) substrate and a front-bonded ruby crystal. The 532 nm laser pulses from an Nd-YAG laser incident on the front surface of the ruby crystal. A portion of the laser pulse passes through the crystal and reaches the GaAs substrate, and the remaining portion of the laser pulse is absorbed by the ruby crystal. This results in the emission of 694 nm fluorescent light. Furthermore, a portion of emitted fluorescent light also reaches the GaAs substrate. The highfluence 532 nm short laser pulse with a pulse width around several nanoseconds is used to trigger the PCSS entering the high-gain nonlinear mode, whereas the low-fluence longlifetime (on the order of a millisecond) 694 nm fluorescent light is used to maintain the lock-on time. Thus, an ultralong lock-on time on the order of millisecond is achieved, which is 3 orders of magnitude longer than a typical lock-on time of high-gain GaAs PCSS.

To overcome the depth limitation of the space-charge-controlled (SCC) potassium tantalate niobate (KTN) deflectors, we report in this paper a method of increasing the aperture of SCC-KTN deflectors by harnessing the physical mechanism of blue light photon excitation. The experimental results show that the deflection angle can be increased from 0.7 mrad without the blue light excitation to 2.5 mrad with the blue light excitation at a penetration depth of 5 mm under the same external applied voltage, which is consistent with the theoretical analysis. This represents a substantial increase in the deflection angle at a much deeper penetration depth, which can be very useful for applications such as high speed 3D printings and displays.

The temperature dependent electrostrictive effect, with respect to increasing the cooling rate to a cooling temperature, was quantitatively investigated in potassium tantalate niobate (KTN) lead-free single crystals above and near Curie temperature (T C). High work-function Pt electrodes are used to minimize the effect of charge injection, and the electric field induced displacement was measured with Michelson interferometry. It was found that a giant electrostrictive coefficient of 696 × 10 −16 m 2 /V 2 could be obtained at a high cooling rate of 0.75 ○ C/s to a temperature of T C + 4.5 ○ C due to the evolution of polar nano-regions, which is one order of magnitude larger than the previously reported value in KTN crystals. This strengthens the realization of replacing toxic lead-based electrostrictive materials with environmentally friendly KTN materials in real world applications.