This paper presents a nanosecond speed KTN varifocal lens. The tuning principle of varifocal lens is based on the high-speed refractive index modulation from the nanosecond speed tunable electric field. A response time on the order of nanoseconds was experimentally demonstrated, which is the fastest varifocal lens reported so far. The results confirmed that the tuning speed of the KTN varifocal lens could be significantly increased by avoiding the electric field induced phase transition. Such a nanosecond speed varifocal lens can be greatly beneficial for a variety of applications that demand high speed axial scanning, such as high-resolution 3D imaging and high-speed 3D printing.
This paper presents an ultra-fast growth of silicon carbide crystal with the size up to 50 μm from SiC nanopowders. By using a CO2 laser with a power of 30W to heat the silicon carbide nanopowders in a vacuum chamber, the nanopowders tends to congregate together to form larger particles first. Following the slow cooling process, the congregate formation would further transform to final SiC micro-crystals. The two types of final products grown from quenching process and slow cooling process were analyzed by SEM. The lattice structure of final SiC micro-crystal was determined to be hexagonal structure according to the XRD analysis.
This paper presents a quantitative two-dimensional (2D) analysis on high power GaN light emitting diodes (LEDs) fabricated on asymmetric micro-structured substrates. It is found that the light extraction efficiency (LEE) can be substantially improved from conventional symmetric structure to asymmetric structure. The increase of LEE is mainly dedicated to the increased surface area and better randomization on the direction of transmitted/reflected light, which enhances the escaping probability after multiple reflections. This quantitative 2D analysis lays down a solid foundation for the future quantitative 3D analysis.
In this paper, we present a novel large capacity (a 1000+ channel) time division multiplexing (TDM) laser beam combining technique by harnessing a state-of-the-art nanosecond speed potassium tantalate niobate (KTN) electro-optic (EO) beam deflector as the time division multiplexer. The major advantages of TDM approach are: (1) large multiplexing capability (over 1000 channels), (2) high spatial beam quality (the combined beam has the same spatial profile as the individual beam), (3) high spectral beam quality (the combined beam has the same spectral width as the individual beam, and (4) insensitive to the phase fluctuation of individual laser because of the nature of the incoherent beam combining. The quantitative analyses show that it is possible to achieve over one hundred kW average power, single aperture, single transverse mode solid state and/or fiber laser by pursuing this innovative beam combining method, which represents a major technical advance in the field of high energy lasers. Such kind of 100+ kW average power diffraction limited beam quality lasers can play an important role in a variety of applications such as laser directed energy weapons (DEW) and large-capacity high-speed laser manufacturing, including cutting, welding, and printing.
A non-uniform space charge-controlled KTN beam deflector is presented and analyzed. We found that a non-uniform
space charge can result in a non-uniform beam deflection angles. This effect can be useful for some applications such as
electric field controlled beam separation. However, a non-uniform space charge needs to be avoided if one wants uniform
beam deflection throughout the entire crystal.
In this paper, a multi-dimensional KTN beam deflector is presented. The multi-scanning mechanisms, including space-charge-
controlled beam deflection, composition gradient-induced beam deflection, and temperature gradient-induced
beam deflection are harnessed. Since multi-dimensional scanning can be realized in a single KTN crystal, it represents a
compact and cost-effective approach to realize multi-dimensional scanning, which can be very useful for many
applications, including high speed, high resolution imaging, and rapid 3D printing.
This study reports a high light extraction efficiency (LEE) light emitting diode (LED) by harnessing asymmetric obtuse
angle micro-structured roofs. In comparison to conventional symmetric micro-structured roofs, the LEE has been
improved from 62% to 73%. This represents an 11% improvement in LEE, which is significant for LED. It is
speculated that this improvement is largely due to the increased surface area and better randomization on the direction of
transmitted/reflected light, which enhances the escaping probability after multiple reflections.