Abstract
Direct writing by laser techniques in the micro and nanostructuring scale is very important for the fabrication of new materials and multifunctional devices. They have proven to be very successful tools for precision machining and microfabrication with applications in optical devices, microelectronics, medical device, biomedical, defense applications, and MEMS. Focused nanosecond (ns) laser pulses can produce periodic structures and arrays pattern structures in semiconductors and thin metallic film on shaped surfaces. The achievable structure size is restricted by the wavelength and diffraction limit as well as it is determined by material properties and laser pulse stability. This thesis proposes a nanosecond laser nanostructuring technique in common optical path configuration to examine the limitations of the currently used fabrication methods and type of setups used; the competitive edge is using nanosecond lasers as a tool. Prospectively, this technology can be applied for femtosecond laser fabrication, because this is an easy, simple and common optical path configuration. For this experimental setup, the use of a common optical path configuration for automatic interference offers equals path lengths. It is not required for complicated optical setups while in femtosecond laser setups, it is extremely important to use path compensation in order to offer time delay for one laser beam due to a long path and more optical components. A low repetition rate, low power nanosecond laser system is investigated to preventing the (HAZ) conditions. The influence of the laser repetition rate and pulse energy on the size and quality of submicron features which fabricated on silicon wafers and thin gold film is investigated. In terms of nanomachining below the ablation threshold (surface patterning), the influence of laser fluence, repetition rate and pulse energy on the spacing as well as diameter of dots created on silicon wafer surface is examined. These studies show the capability of the proposed system of nanosecond laser in common optical path configuration in meeting the industry requirements.
Highlights
1.1 INTRODUCTION TO SUBMICRON AND NANO SURFACE PATTERNING TECHNIQUESFabrication of surface patterns structures in micro and nanometer scales of various materials is one of the most important applications in micromachining domain
The dots arrays was governed and arose from intersect two patterns, first is grating that generated by direct interference writing formula and second is ripple that generated by interference between the incident laser and the frozen capillary waves (FCW)
The experimental setup is designed with a minimum number of optical components; the technique can simplify the optical parts for a better fabrication process with fewer vibrations
Summary
1.1 INTRODUCTION TO SUBMICRON AND NANO SURFACE PATTERNING TECHNIQUESFabrication of surface patterns structures in micro and nanometer scales of various materials is one of the most important applications in micromachining domain. The demand for more precise and more efficient apparatuses is driving the semiconductor industry towards the use of different materials of thin films fabricated by pulsed laser It has attracting interest in increasing the densities of integrated circuits, quantum devices, and recording media. For instance gratings of submicron spacing are important components in the development of wavelength specific devices, such as channel selectors and waveguide laser mirrors [52].There are number of gratings fabrication techniques that have been suggested to meet the stringent requirements. Laser ablation is preferred technique for dots arrays over the large-scale machining area by a single shot, fast, clean operating and economic In this Chapter, a novel method is developed for a single shot laser patterning of variable nano features on a thin gold film grating of 1000 A thickness coated on quartz substrate. The end product will be used as a master to perform the standard replications of sub wavelength structures
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