The distribution and characteristics of surface cracking (i.e. sub-surface damage or SSD) formed during standard grinding processes has been investigated on fused silica glass. The SSD distributions of the ground surfaces were determined by: (1) creating a shallow (18-108 {micro}m) wedge/taper on the surface by magneto-rheological finishing; (2) exposing the SSD by HF acid etching; and (3) performing image analysis of the observed cracks from optical micrographs taken along the surface taper. The observed surface cracks are characterized as near-surface lateral and deeper trailing indent type fractures (i.e., chatter marks). The SSD depth distributions are typically described by a single exponential distribution followed by an asymptotic cutoff in depth (c{sub max}). The length of the trailing indent is strongly correlated with a given process. Using established fracture indentation relationships, it is shown that only a small fraction of the abrasive particles are being mechanically loaded and causing fracture, and it is likely the larger particles in the abrasive particle size distribution that bear the higher loads. The SSD depth was observed to increase with load and with a small amount of larger contaminant particles. Using a simple brittle fracture model for grinding, the SSD depth distribution has been related tomore » the SSD length distribution to gain insight into ''effective'' size distribution of particles participating in the fracture. Both the average crack length and the surface roughness were found to scale linearly with the maximum SSD depth (c{sub max}). These relationships can serve as useful rules-of-thumb for nondestructively estimating SSD depth and to identify the process that caused the SSD. In certain applications such as high intensity lasers, SSD on the glass optics can serve as a reservoir for minute amounts of impurities that absorb the high intensity laser light and lead to subsequent laser-induced surface damage. Hence a more scientific understanding of SSD formation can provide a means to establish recipes to fabricate SSD-free, laser damage resistant optical surfaces.« less

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Sub-surface mechanical damage distributions during grinding of fused silica

Thanks to its unique features at the nanoscale, nanofluidics, the study and application of fluid flow in nanochannels/nanopores with at least one characteristic size smaller than 100 nm, has enabled the occurrence of many interesting transport phenomena and has shown great potential in both bio- and energy-related fields. The unprecedented growth of this research field is apparently attributed to the rapid development of micro/nanofabrication techniques. In this review, we summarize recent activities and achievements of nanofabrication for nanofluidic devices, especially those reported in the past four years. Three major nanofabrication strategies, including nanolithography, microelectromechanical system based techniques, and methods using various nanomaterials, are introduced with specific fabrication approaches. Other unconventional fabrication attempts which utilize special polymer properties, various microfabrication failure mechanisms, and macro/microscale machining techniques are also presented. Based on these fabrication techniques, an inclusive guideline for materials and processes selection in the preparation of nanofluidic devices is provided. Finally, technical challenges along with possible opportunities in the present nanofabrication for nanofluidic study are discussed.

/pdf/review-article-fabrication-of-nanofluidic-devices-44dwqgr8ys.pdf

Review article: Fabrication of nanofluidic devices

A spherical artificial compound eye which is comprised of an imaging microlens array and a pinhole array in the focal plane serving as receptor matrix is fabricated. The arrays are patterned on separate spherical bulk lenses by means of a special modified laser lithography system which is capable of generating structures with low shape deviation on curved surfaces. Design considerations of the imaging system are presented as well as the characterization of the comprising elements on curved surfaces, with special attention to the homogeneity over the array. The assembled system is the first spherical compound eye able to capture images. It is evaluated by analyzing resolution and cross-talk between the single channels.

Laser lithographic fabrication and characterization of a spherical artificial compound eye.

While the vast majority of integrated photonic devices are traditionally fabricated on rigid substrates, photonic integration of both passive and active photonic devices on flexible polymer substrates has been demonstrated in recent years, and its applications in imaging, sensing and optical interconnects are being actively pursued. This paper presents an overview of the emerging field of mechanically flexible photonics, where we examine material processing and mechanical design rationales dictated by application-specific optical functionalities. The examples include semiconductor nanomembranes which serve as the key enabling material for hybrid inorganic-organic flexible active photonics, and monolithically integrated passive photonic structures fabricated from semiconductors, polymers, or amorphous materials. Technical challenges and further research opportunities related to materials engineering and device integration on flexible substrates are also discussed.

https://udel.edu/~hujuejun/My%20Papers/Journal%20Papers/Flexible%20integrated%20photonics%20--%20where%20materials,%20mechanics%20and%20optics%20meet.pdf

Flexible integrated photonics: where materials, mechanics and optics meet [Invited]

After the introduction and justification of several more or less well known and complicated conversion topologies based on series resonance, this chapter will focus on the design of the non-reversible series resonant converter. Following this, a brief description will be given concerning a collection of DC/DC and DC/AC converters developed under various industrial contracts by the Laboratoire d’Electrotechnique et d’Electronique Industrielle (L.E.E.L), Toulouse, France.

Design and Applications

Fabrication of enclosed nanofluidic channels by UV cured imprinting and optimized thermal bonding of SU-8 photoresist

We demonstrate a novel method for fabricating glass microlens (arrays) with single step on conventional lens surface. In this method, the glass microlens can be achieved by only one step with sol gel glass material. The microlens aperture and focus length can be controlled easily and uniformly. The fabricated sample shows good focusing property. This work will be useful to improve the performance of compound eyes optical system such as camera, telescope, 3D integral imaging and so on.

Single step fabrication of microlens arrays with hybrid HfO2-SiO2 sol-gel glass on conventional lens surface.

Free-standing SU-8 subwavelength gratings fabricated by UV curing imprint

Study on the surface roughness of substrate with multi-fractal spectrum

We demonstrate a method of fabricating varied-line-spacing grating by employing elastic medium with variable vertical section. The advantages of this technique include continuous variation of line spacing, high fabrication efficiency, low cost, etc. It is very difficult or impractical to produce this variation of line spacing by traditional interference lithography. This kind of grating can be used in an optical position sensor to improve the precision of the sensor.

Shaojun Fu

Papers

Fabrication of enclosed nanofluidic channels by UV cured imprinting and optimized thermal bonding of SU-8 photoresist

Single step fabrication of microlens arrays with hybrid HfO2-SiO2 sol-gel glass on conventional lens surface.

Free-standing SU-8 subwavelength gratings fabricated by UV curing imprint

Study on the surface roughness of substrate with multi-fractal spectrum

Fabrication of varied-line-spacing grating by elastic medium.