In this paper, a new type of waveguide switch-field induced dynamic optical waveguide switch is presented. The switching
mechanism is based on electric-field induced dynamic waveguiding effect in nanodisordered potassium tantalate niobate
(KTN) crystals. By applying an electric field at different locations, different waveguide paths are created, which result in
different output locations. The major advantages of this unique optical switch are broad bandwidth, covering the entire
1300 nm – 1600 nm fiber optic communication window, and ultrafast switching speed (on the order of nanosecond), which
can be very useful for next generation optical networks such as the one used in data center networks.
By taking advantage of the recent advances in high quality sizable KTN crystal growth, a broadband large field of view (FOV) EO modulator is developed and presented in this paper. The experimental and theoretical studies indicate that the built EO modulator not only has a broad bandwidth (~1 GHz) but also has a large FOV (+/- 30 deg) because cubic phase KTN crystals do not introduce any intrinsic birefringence without applying the external electric field.
The study reveals an innovative design of the optical waveguide based on potassium tantalate niobate (KTN) crystal. The
device’s guiding properties, which benefits from the large electro-optic coefficients of KTN crystal, can be dynamically
controlled by an external electric field in a relatively simple waveguide structure. Finite Element Method (FEM) and
Beam Propagation Method (FEM) are used in the theoretical part of this work which shows that the KTN based dynamic
waveguide has good potential on applications of several kinds of optical switches and modulators.
The method by applying the interfered femtosecond laser to create nanostructured copper (Cu) surface has been studied.
The nanostructure created by direct laser irradiation is also realized for comparison. Results show that more uniform and
finer nanostructures with sphere shape and feature size around 100 nm can be induced by the interfered laser illumination
comparing with the direct laser illumination. This offers an alternative fabrication approach that the feature size and the
shape of the laser induced metallic nanostructures can be highly controlled, which can extremely improve its
performance in related application such as the colorized metal, catalyst, SERS substrate, and etc.
In recent years, much of effort has been devoted in the field of optical switches, including electro-optics (EO), magnetooptics
(MO), acousto-optics (AO), liquid crystal (LC), and microelectromechanical systems (MEMS). However, issues
which involve switching speed, aperture size, and extinction ratio cannot be simultaneously settled by the present
approaches. The paper proposes a novel optical switch based on tunable photonic metamaterial. By the controllable
external electrical or magnetic field, the nano-structure is forced to vary its optical properties to be an optical switch. The
theoretical studies suggest that the device could offer the merit features of ultra-fast speed, large aperture, and high
extinction ratio. In the future, we will not only thoroughly model the proposed devices, but investigate kinds of possible
fabrication process to implement the design. To be a next-generation optical switch, the tunable photonic metamaterial
has large potential in several civilian applications, including mobile high-speed display, free-space optical
communication, solar concentration, and the optical printing.
In this paper, we present the design and the fabrication method for high DC bias voltage photoconductive semiconductor
switch (PCSS). By employing a low temperature grown molecular beam epitaxial GaAs (LT-MBE GaAs) and a proper
protection coating to prevent air breakdown, the DC bias electric field can be significantly increased. Such a PCSS
structure can effectively achieve a low DC dark current in a high voltage pulse generation system with smaller PCSS
sizes. DC bias capability also eliminates the need of complicated synchronization. The application of high DC bias field
PCSS will also be discussed.
In this paper, recent works of buried chemical detection system by stimulating and enhancing spectroscopic
signatures with multi-frequency excitations are discussed. In this detection system, those multiple excitations,
including DC electric field, microwave, CO<sub>2</sub> laser illumination and infrared radiation, are utilized and each of
them plays a unique role. The Microwave could effectively increase the buried chemicals' evaporation rate from
the source. The gradient DC electric field, generated by a Van De Graaff generator, not only serves as a vapor
accelerator for efficiently expediting the transportation process of the vapor release from the buried chemicals,
but also acts as a vapor concentrator for increasing the chemical concentrations in the detection area, which
enables the trace level chemical detection. Similarly, CO<sub>2</sub> laser illumination, which behaves as another type
vapor accelerator, could also help to release the vapors adsorbed on the soil surface to the air rapidly. Finally, the
stimulated and enhanced vapors released into the air are detected by the infrared (IR) spectroscopic fingerprints.
Our theoretical and experimental results demonstrate that more than 20-fold increase of detection signal can be
achieved by using those proposed technology.
Zinc oxide (ZnO) nano-wires have draw people's attention in recent studies. The unique structural and physical
properties offer fascinating potential for future technological applications. The state-of-the-art fabrication process of ZnO
nano-wires is based on vapor-liquid-solid (VLS) method. In this paper, the microwave assisted heating technique is
introduced for the growth of ZnO nanopillar arrays. The microwave grown ZnO nanowires were characterized by fieldemission
scanning electron microscopy, X-ray diffraction, transmission electron microscopy, and photoluminescence
spectroscopy. It was demonstrated that (001) oriented single crystal ZnO nanowires can be grown vertically and
uniformly on a-plane sapphire wafers.
In this paper, the separation of transmitted and diffused light beams in a scattering medium by a magneto-optical ultrafast
switch is investigated. The magneto-optical switch previously developed by the authors is capable of 1 ns switching
speed and has a 1 mm clear aperture. The diffused light beams and ballistic beams in a scattering medium are simulated
in the lab by two beam paths. One beam is delayed from the other to simulate the diffused light beam and the ballistic
beam, respectively. The magneto-optical switch is synchronized with the required delay to the laser pulse to keep only
the ballistic beam, acting as an ultrafast light gate. The concept is demonstrated with a 532nm Q-switched pulsed laser.
In this paper, some of our recent works on the design of different types of nanostructured surfaces, the
terahertz generation, terahertz lenses, and terahertz metamaterials are reviewed and discussed. The
mechanism behind the terahertz radiation is the photoelectric emission effect, which leads to the
oscillating motions of emitted electrons and are affected by the electric field inside the metal.
Furthermore, by using those nanostructured surfaces, terahertz lenses, which are due to the excitation
of surface plasmons, and terahertz metamaterials, which results from the effective inductor-capacitor
resonator, are also presented.
In this paper, the application of a broadband spatially coherent IR supercontinuum source to the biomedical imaging and
detection is presented. New IR material is proposed to generate Mid-IR supercontinuum above 4um, which was previously
difficult due to inherent material absorption. Broad Mid-IR supercontinuum is numerically shown to be possible
with one single wavelength pump in appropriate fiber structure.
Mid-IR broadband sources are very useful in IR Optical
Coherence Tomography (OCT) and spectroscopy in biomedical materials, due to the rich absorption structures the
Mid-IR region. Broadband Mid-IR source is better than single wavelength tunable source, such as Quantum Cascaded Lasers
(QCL), for faster analysis speed, since slow scan is not required.