This PDF file contains the front matter associated with SPIE Proceedings Volume 10018, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Recent progresses in femtosecond laser (fs) manufacturing have already proved that fs laser is a powerful tool in three dimensional internal structure fabrications. However, most studies are mainly focused on realize such structures in inorganic transparent dielectric, such as photosensitive glass and fused silica, etc. In this study, we present two methods to fabricate embedded internal 3D structures in a polymer dielectric material polymethyl methacrylate (PMMA). Both continuous hollow structure such as microfluidic channels and discrete hollow structures such as single microcavities are successfully fabricated with the help of femtosecond lasers. Among them, complicated 3D microchannel with a total length longer than 10mm and diameters around 80μm to 200μm are fabricated with a low repetition rate Ti: sapphire femtosecond laser by direct laser writing at a speed ranging from 25μm/s to 2000μm/s; microcavities which function as concave microball lenses (CMBLs) and can be applied in super-wide-angle imaging are fabricated with a high repetition rate femtosecond fiber laser due to the distinct heat accumulation effect after 5s irradiation with the tightly focused fs laser beam. These new approaches proved that femtosecond laser direct writing technology has great application potential in 3D integrated devices manufacturing in the future.

W/Cu joining is key for the fabrication of high heat load components for fusion reactors, which however suffers from the low W/Cu bonding strength due to the immiscible nature of W-Cu system. In this study, we proposed a method for strengthened W/Cu joining based on femtosecond (fs) laser induced micron-scale W/Cu interface structure. W surfaces were irradiated by fs laser to form micron-scale cubes array, and then joined to Cu by hot pressing at 1000 °C, 80 MPa for 2.5 hours. The tensile strength of the W/Cu joining samples was investigated. The results show that micron-scale cubes array was successfully introduced into W/Cu interface without any cracks or pores. The interface structure helps to increase the W/Cu bonding strength to as high as 59.61 MPa, increased by about 50% as compared to W/Cu joining with a flat interface (bonding strength 40.11 MPa). The W/Cu bonding strength shows positive correlation with the W/Cu interface area, indicating the possibility to control the W/Cu bonding strength by simply adjusting the fs laser ablation parameters for the fabrication of cubes array on W surface. Our research provides a method for strengthened joining between intrinsically immiscible materials, including but not limited to W and Cu.

Traditional laser lithography systems cannot write sub-wavelength patterns due to the diffraction limit. In this paper, a novel super-resolution laser direct writing method is proposed to break through the diffraction limit. Compared with conventional lithography systems, the photoresist layer in this method is overlaid by an extra photochromic layer which is a mixture of metanil yellow and aqueous PVA solution. Then a vortex beam with a hollow energy distribution is used to expose the photochromic layer and make an annular region of the photochromic layer opaque to the writing beam. Thus, a virtual aperture is formed in the photochromic layer which can confine the diameter of the writing beam and reduce the linewidth exposed in the photoresist layer. Lithography process of this new method was modeled and a corresponding simulation was made. In this simulation, the intensity ratio of the two beams, relative absorption coefficients and other parameters were changed to study their influence to linewidth in the photoresist. An experimental setup was designed to validate the simulation, where the wavelengths of the writing beam and the vortex beam are 405 nm and 532 nm, respectively. These two beams are strictly coaxial when they are incident to the photochromic layer. The experimental results agree quite well with the model simulation, showing that the linewidth could be reduced by increasing the intensity ratio of the vortex beam to the writing beam. They also indicate that the vortex beam could effectively reduce the lithography linewidth to 300nm or even smaller.

The paper presents a dual-beam interference lithography technology for fabrication of diffraction gratings for surface encoders by using cost-effective 405 nm blu-ray laser diodes. In this system, an amplitude division interferometer system is employed. A laser beam raying from a blu-ray laser diode is collimated and then divided into two beams by a beam splitter. These two beams are changed their propagation directions and interfere with each other. Generated interference fringes are exposed on the photoresist coated substrate. Grating line spacing d can be adjusted by changing the incident angle between these two beams. Grating width W_c that determines the measurement of the surface encoder is decided by the coherence length L_c of the laser diode and the grating line spacing d. Calculation and simulation were carried out to decide the grating width. L_c was experimentally obtained. A fabrication system was constructed to verify the feasibility of this technology. Diffraction gratings with a 2.5 micron line spacing and a 2.5 mm width was obtained.

In this work, various types of pure nanoparticles are synthesized by pulsed laser ablation. A novel method using laser ablation is presented to synthesize and separate different sizes of nanoparticles. Laser ablation is applied as a physical and environmental friendly method to generate a variety of nanoparticles in air-based environments. By tuning laser beam horizontal and placing target materials vertically to the substrate, nanoparticles can be generated and separated automatically depending on their sizes. The size distribution is evaluated by optical microscope and nanoparticles are counted according to their diameters. The diameter of the particles ranges from 30nm to 5000nm. This work provides a versatile means to collect many types of uniform functional nanoparticles for a wide range of applications.

Taking laser ablation and laser chemical machining as examples, this paper explores the challenges to implement the energy-based approach of process signature in laser micro processing. It is expected that laser processes and specific materials independent mechanisms can be found, which are deeper causes of the generation of the surface integrity behind the interactions among the specific energy sources, mediums, surface, subsurface, base material and environment. With the aim of dealing with the challenges, this paper discusses a new point of view, cumulation of modifications, concerning more effects in laser micro processing.

The continuous in situ laser-induced catalysis proceeding via generation and growth of nano-sized copper particles was discussed. Also, the simple and lost-cost method for manufacturing of microstructural copper electrodes was proposed. The electrochemical properties of these electrodes were studied by cyclic voltammetry and impedance spectroscopy. The surface of the deposited copper structures (electrodes) was investigated by X-ray photoelectron spectroscopy and atomic force microscopy. These microstructures are highly conductive and porous with a dispersion of pore size ranging from 50 nm to 50 μm. An analytical response of the fabricated copper electrode is 30 times higher than those observed for a pure bulk copper with similar geometric parameters. A study of sensory characteristics for hydrogen peroxide determination showed that the value of Faraday current at the fabricated copper electrode is 2-2.5 orders of magnitude higher than for etalon one.

Nowadays surface acoustic wave sensors are produced using a photolithography method. It is expensive in small series production and do not allow further topology correction, which is important for inertial sensors. In this case, a laser ablation method seems promising. It does not require a photomask and can achieve a good matching of topologies produced on opposite sides of the wafer. Several delay lines were produced using a proposed technique. Its characteristics were explored and discussed.

We present a kind of a switchable repetition rate mode-locked of bound-state solitons in a fiber laser based on Bi₂Se₃ saturable absorber (SA). In the fiber laser, two forms of the bound-state optical spectrum with central wavelength of 1532 nm are observed. The fiber laser is operate at the abnormal group velocity dispersion and the bound state pulses are equally distributed to the temporal domain. The fundamental cavity repetition-rate is 1.11 MHz with a pulse duration of 2.27 ps. The output average power and the pulse peak energy are 1.53 mW and 607 W respectively, which the pump power is 267 mW. The different repetition-rates are also achieved by changing the pump power or adjusting the angle of polarization controller. In the experiment, the repetition-rate is switched from 1.11 MHz to 41.32 MHz (37th-order, the highest repetition-rate).

The intrinsic phase noise of distributed feedback (DFB) fiber laser greatly reduces the signal to noise ratio (SNR) of unbalance interferometric fiber sensor system, which has a negative influence on the demodulation of tiny signal. In order to suppress the phase noise of DFB fiber laser (DFB-FL), a self-injecion locking DFB-FL was presented. Result of experiment demonstrated that the phase noise can be suppressed by the self-injection locking structure and the effect of suppression was improved with the increase of the length of locking ring. When the length of locking ring is two meters, the phase noise above 500Hz decreases by 8 dB / √Hz demodulated by an one meter optical path difference asymmetric Michelson Interference, and the mode is not hoping in eight hours. Contrast with the unlocked DFB-FL, the pump efficiency of self-injection locking DFB-FL is increased by 30%.