The measurement of surface morphology of a material with high resolution is important in both the industrial and biomedical applications. Furthermore, a precise measurement of the morphology of the internal interface is usually needed for materials with multilayered structures. Although some optical techniques can provide subsurface imaging of materials, their resolutions are difficult to achieve nanometer scale. In our research, an optical system based on a composite interferometer which can image the internal interface of a material with nanometer resolution is proposed and demonstrated. The system consists of a Michelson interferometer and a Mach-Zehnder interferometer. The Michelson interferometer with a broadband light source is used for three-dimensional imaging of the sample. In the Mach-Zehnder interferometer, a prism and a retro-reflector are arranged for an optical delay line with adjustable length. The two interferometers share common light source and a rapid scanning optical delay system used for axial scanning. In the experiment, the adjustable optical delay line in the second interferometer is adjusted for the optical path lengths to match that relative to the interface under investigation. With a phase compensation mechanism, the interface can be imaged with an axial accuracy at nanometer scale.

Microfluidic design and fabrication was developed for wafer-scale varifocal liquid lens which is slim less than 0.9mm. The liquid-filled varifocal lens has advanced functions such as auto macro and focusing to obtain a high quality of image. This varifocal lens is similar to human eye and it consists of main Si frame which has penetrated inner hole, upside-bonded PDMS (polydimethylsiloxane) elastomer membrane, downside-bonded glass plate and optical fluid confined by these structures. Si frame, which has a circular hole for tunable lens chamber, several holes for actuator chamber and micro-fluidic channels between chambers, is fabricated using thin Si wafer and microelectromechanical system (MEMS) processes. When optical fluid is filled the internal cavity by conventional injection, void trapping which degrades optical performance or filling impossibility happens because of high aspect ratio between lens diameter and thickness for slim liquid lens. To prevent these problems, we developed wafer-based microfabrications of seal line dispensing, accurate dropping of optical fluid, pressing & bonding process in vacuum and UV sealant curing. Afterward, electro-active polymer actuators, which push the optical fluid to change the lens shape, was attached on the PDMS membrane of liquid lens wafer and sawing process of 9.4mm*9.0mm chip size followed. Finally, the varifocal liquid lens which is slim less than 0.6mm thickness (0.9mm included actuators), tunable more than 20diopter changes of refractive power, guaranteed reliability of 300,000 repetitions and suitable for mass production, was realized.

We report on device properties of tunable spatial light modulators for high-resolution optical applications by a novel fabrication process. Thin polydimethylsiloxane (PDMS) films (4ìm-13ìm) were sandwiched between a flexible gold film(50nm) and a rigid substrate with a comb-like electrode either by compression molding or spin coating. By applying voltage between the upper gold film and underlying electrode, the initial plane PDMS surface changes into a form of grating. Far-field scattering pattern with high order light components was observed by illumination at the continuously reflective gold film with laser beam. Characterization was done by measuring the grating profile of the PDMS and the response time. The PDMS deformation was demonstrated to increase with driving voltage. The deformation for 6ìm thick PDMS is measured around 100nm when driving voltage is applied as 230V. Modeling and simulation of the modulator electro-mechanical behavior was done for varies structure design. The simulation results showed fair agreement with the experimental results. The response time, which defines how fast the PDMS response to the applied voltage, was measured as a function of the driving voltage. The measured rise time is around 1 micorseconds and the fall time is around 0.2 microseconds.

Monolithic lens arrays are used in applications such as hyper-spectral imaging, Shack-Hartmann wavefront sensors, and lens replication molds, where lens-to-lens registration is critical. Traditionally, monolithic lens arrays are produced by diamond turning one lens at a time on axis. This process requires the substrate to be shifted to a new position before the next lens is machined. This intermediate step increases production time and makes it difficult to achieve lens-to-lens registration accuracy. Freeform diamond machining allows lens arrays to be produced in a single setup. Since there are no intermediate shifts of the substrate, the lens-to-lens registration is inherent to the program and machine accuracy. The purpose of this paper is to compare different freeform manufacturing processes in the production of a three-element germanium lens array. Freeform machining technologies including Slow Tool Servo (STS), Fast Tool Servo (FTS) and Diamond Micro-Milling (DMM) will be used to produce this lens array. The results for process times, figure, and finish characteristics will be compared across all three techniques.

Applying aspherical and freeform optics in high-end optical systems can improve system performance while decreasing the system mass, size and number of required components. The NANOMEFOS measurement machine is capable of universal non-contact and fast measurement of aspherical and freeform optics up to ∅500 mm, with an uncertainty of 30 nm (2σ). In this machine, the surface is placed on a continuously rotating air bearing spindle, while a specially developed optical probe is positioned over it by a motion system. A separate metrology system measures the probe and product position relative to a metrology frame. The prototype realization, including custom electronics and software, has been completed. The noise level at standstill is 0.88 nm rms. A reference flat was measured with 13 μm and 0.73 mm tilt. Both measurements show an rms flatness of about 8 nm rms, which correspond to the NMi measurement. A hemisphere has also been measured up to 50° slope, and placed 0.2 mm eccentric on the spindle. These measurements reproduce to about 5 nm rms. Calibration and software are currently being improved and the machine is applied in TNO aspherical and freeform optics production.

The breakthrough of freeform optics is limited by manufacturing and metrology technology. However, today's manufacturing machines like polishing robots and diamond turning machines are accurate enough to produce good surface quality, so the question is how accurate can a freeform be produced. To investigate how accurate freeform optics can be diamond turned, measurable freeforms (e.g. an "off-axis" sphere) were diamond turned and they were compared to there on-axis equivalents. The results of this study are described in this paper. Furthermore, an overview of the accuracies of freeform optics that TNO diamond turned are presented. An indication of freeform accuracy for diamond turned optics is derived from this, which can be used for optical designers as a guideline in their design work.

The application of multi-axis micromilling and flycutting is investigated for the fabrication of complex optical microsystems incorporating different classes of aspherical and freeform optical elements. Such elements provide the necessary degrees of freedom for aberration correction in integrated optical microsystems and are specifically interesting for applications like beam shaping or computational imaging. Especially for elements with small radii of curvature, high aspect ratios and spatial frequencies, micromilling and flycutting are interesting alternatives to the more established diamond turning technology. We present the results of the fabrication of a monolithically integrated optical microsystem consisting of two tilted flat surfaces used as coupling prisms and a freeform imaging element. On the resulting surfaces the average roughness height without subsequent polishing was found to be R_a = 18.2 ... 25.5 nm (depending on the fabrication technique) with an overall shape accuracy < 0.5 ... 2.9 μm (based on the determination of the radii of curvature).

Optical designers have been designing ultraviolet (UV) systems at wavelengths in the UV region for many years. With increasing demand for deep UV applications, special considerations that are not applicable to traditional visible optics must be taken to produce the optics. Specifically as the wavelength of incident light decreases, the importance of very smooth surfaces increases. The intent of this project is to increase the performance of UV optics in a four-phase project. The first phase consists of characterizing sub-surface damage using destructive methods to enable process control, the second phase (presented here) focuses on polishing methods, the third phase will include cleaning and possible etching protocols and the fourth phase will be improving thin film coating performance.

A conventional polishing study was conducted with infrared material zinc sulfide with the goal of producing defect-free polished surfaces in predictable amounts of time. Utilizing the measured electro-kinetic properties of the zinc sulfide and polishing abrasives, polishing slurries were selectively altered and the resulting removal rates and surface roughness values were measured. This paper will serve as a baseline for developing an empirical model for optimizing both surface roughness and removal rate for two different types of abrasives and two pitch types with ZnS.

Aqueous magnetorheological (MR) polishing fluids used in magnetorheological finishing (MRF) have a high solids concentration consisting of magnetic carbonyl iron particles and nonmagnetic polishing abrasives. The properties of MR polishing fluids are affected over time by corrosion of CI particles. Here we report on MRF spotting experiments performed on optical glasses using a zirconia coated carbonyl iron (CI) particle-based MR fluid. The zirconia coated magnetic CI particles were prepared via sol-gel synthesis in kg quantities. The coating layer was ~50-100 nm thick, faceted in surface structure, and well adhered. Coated particles showed long term stability against aqueous corrosion. "Free" nano-crystalline zirconia polishing abrasives were co-generated in the coating process, resulting in an abrasivecharged powder for MRF. A viable MR fluid was prepared simply by adding water. Spot polishing tests were performed on a variety of optical glasses over a period of 3 weeks with no signs of MR fluid degradation or corrosion. Stable material removal rates and smooth surfaces inside spots were obtained.

The material removal in magnetorheological finishing (MRF) is known to be controlled by shear stress, λ, which equals drag force, F_d, divided by spot area, As. However, it is unclear how the normal force, F_n, affects the material removal in MRF and how the measured ratio of drag force to normal force F_d/F_n, equivalent to coefficient of friction, is related to material removal. This work studies, for the first time for MRF, the normal force and the measured ratio Fd/Fn as a function of material mechanical properties. Experimental data were obtained by taking spots on a variety of materials including optical glasses and hard ceramics with a spot-taking machine (STM). Drag force and normal force were measured with a dual load cell. Drag force decreases linearly with increasing material hardness. In contrast, normal force increases with hardness for glasses, saturating at high hardness values for ceramics. Volumetric removal rate decreases with normal force across all materials. The measured ratio F_d/F_n shows a strong negative linear correlation with material hardness. Hard materials exhibit a low "coefficient of friction". The volumetric removal rate increases with the measured ratio F_d/F_n which is also correlated with shear stress, indicating that the measured ratio F_d/F_n is a useful measure of material removal in MRF.

Magnetorheological finishing (MRF) is a sub-aperture deterministic process for fabricating high-precision optics by removing material and smoothing the surface. The goal of this work is to study the relative contribution of nanodiamonds and water in material removal for MRF of aluminum oxynitride ceramic (ALON) based upon a nonaqueous magnetorheological (MR) fluid. Removal was enhanced by a high carbonyl iron concentration and the addition of nanodiamond abrasives. Small amounts of deionized (DI) water were introduced into the nonaqueous MR fluid to further influence the material removal process. Material removal data were collected with a spot-taking machine. Drag force (F_d) and normal force (F_n) before and after adding nanodiamonds or DI water were measured with a dual load cell. Both drag force and normal force were insensitive to the addition of nanodiamonds but increased with DI water content in the nonaqueous MR fluid. Shear stress (i.e., drag force divided by spot area) was calculated, and examined as a function of nanodiamond concentration and DI water concentration. Volumetric removal rate increased with increasing shear stress, which was shown to be a result of increasing viscosity after adding nanodiamonds and DI water. This work demonstrates that removal rate for a hard ceramic with MRF can be enhanced by adding DI water into a nonaqueous MR fluid.

For the Computer Controlled Polishing (CCP) process of aspheres and freeform shapes different kind of subaperture tools can be used. The selection of the best tool out of a wide range of possible and available tools is today based on the experience of the skilled operator. If the optical part is finished with sufficient quality in a reasonable time, the working procedure is fixed. Another approach is to put the tool choice on a scientific base, using a simulation to generate the wear function and a Power Spectral Density (PSD) analysis to describe the residual shape deviations. Based only on theoretical tool data and the geometric shape of the tool, the final result of the shape correction could be calculated and transferred to a NC machine code for various polishing machines.

Computer controlled optical surfacing (CCOS) requires accurate knowledge of the tool influence function (TIF) for the polishing tool. The linear Preston's model for material removal has been used to determine the TIF for most cases. As the tool runs over the edge of the workpiece, however, nonlinear removal behavior needs to be considered to model the edge TIF. We reported a new parametric edge TIF model in a previous paper.** This model fits 5 parameters to measured data to accurately predict the edge TIF. We present material from the previous paper, and provide a library of the parametric edge TIFs for various tool shape and motion cases. The edge TIF library is a useful reference to design an edge figuring process using a CCOS technique.

Image degradation due to scattered radiation is a serious problem in many short wavelength (X-ray/EUV) imaging systems. Most currently-available image analysis codes require the scatter behavior (BRDF data) as input in order to calculate the image quality from such systems. This BRDF data is difficult to measure and rarely available for the operational wavelengths of interest. Since the smooth-surface approximation is often not satisfied at these short wavelengths, the classical Rayleigh-Rice expression that indicates the BRDF is directly proportional to the surface PSD cannot be used to calculate BRDFs from surface metrology data for even slightly rough surfaces. We discuss the implementation of an FFTLog numerical Hankel transform algorithm that enables the practical use of the computationally intensive Generalized Harvey-Shack (GHS) surface scatter theory. The FFTLog Hankel transform algorithm is validated over the large dynamic range of relevant spatial frequencies required for short wavelength imaging applications, and BRDFs are calculated and displayed for increasingly short wavelengths that violate the smooth surface approximation implicit in the Rayleigh-Rice surface scatter theory.

A profilometer for in situ measurement of the topography of aspheric mirrors called the Swing arm Optical CMM (SOC) was built, and has been used for measuring the figure of 1.4 m convex aspheric mirrors with a performance rivaling full aperture interferometric tests. Errors in the SOC that have odd symmetry are self-calibrated due to the test geometry. Even errors are calibrated against a full aperture interferometric test.

Next generation space telescopes, which are currently being developed in the US and Europe, require large-scale lightweight reflectors with high specific strength, high specific stiffness, low CTE, and high thermal conductivity. To meet budget constraints, they also require materials that produce surfaces suitable for polishing without expensive overcoatings. HB-Cesic® - a European and Japanese trademark of ECM - is a Hybrid Carbon-Fiber Reinforced SiC composite developed jointly by ECM and MELCO to meet these challenges. The material's mechanical performance, such as stiffness, bending strength, and fracture toughness are significantly improved compared to the classic ECM Cesic® material (type MF). Thermal expansion and thermal conductivity of HB-Cesic® at cryogenic temperatures are now partly established; and excellent performance for large future space mirrors and structures are expected. This paper will present the whole manufacturing process of such a space mirror starting from the raw material preparation until the polishing of the optic including cryo testing . The letters "HB" in HB-Cesic® stand for "hybrid" to indicate that the C/C raw material is composed of a mixture of different types of chopped, short carbon-fibers.

New developments in fabrication and testing techniques at the College of Optical Sciences, University of Arizona have allowed successful completion of 1.4-m diameter convex off-axis aspherics. The optics with up to 300 μm aspheric departure were finished using a new method of computer controlled polishing and measured with two new optical tests: the Swingarm Optical CMM (SOC) and a Fizeau interferometer using a spherical reference surface and CGH correction. This paper shows the methods and equipment used for manufacturing these surfaces.

With respect to null test, non-null test is more flexible and can provide fast, general test with acceptable accuracy. A non-null interferometric aspheric testing system, which employs partial null lens and reverse optimization reconstruction, is proposed. The partial null lens compensates most of the longitude aberration of the aspheric under test and keeps the slope of the non-null wavefront within the resolution of the detector. The reverse optimization reconstruction procedure reduces the retrace error of the non-null test and reconstructs the figure of the test aspheric. The characteristic, design process of the partial null lens and especially the implement of the reverse optimization reconstruction are discussed in detail. Computer simulation shows the reverse optimization reconstruction procedure can reconstruct the aspheric figure error with an accuracy better than 1/200wave within 5 mins. The error analysis is also considered and some conclusions are given. This research is of great importance for general aspheric surfacing and testing.

We present the verification procedure for the 1.4 meter primary mirrors of the Magdalena Ridge Observatory Interferometer (MROI). Six mirrors are in mass production at Optical Surface Technologies (OST) in Albuquerque. The six identical parabolic mirrors will have a radius of curvature of 6300 mm and a final surface wavefront quality of 29 nm rms. The mirrors will be tested in a tower using a computer generated hologram, and the Intellium™ H2000 interferometer from Engineering Synthesis Design, Inc. (ESDI). The mirror fabrication activities are currently in the early stage of polishing and have already delivered some promising results with the interferometer. A complex passive whiffle tree has been designed and fabricated by Advanced Mechanical and Optical Systems (AMOS, Belgium) that takes into account the gravity loading for an alt-alt mount. The final testing of the primary mirrors will be completed with the mirror cells that will be used in the telescopes. In addition we report on shear tests performed on the mirror cell pads on the back of the primary mirrors. These pads are glued to the mirror. The shear test has demonstrated that the glue can withstand at least 4.9 kilo Newton. This is within the requirements.

A number of ongoing astrophysical mission concept studies are based on large aperture spaceborne telescopes. As optics get larger, both manufacturing and engineering trades come into consideration and must be balanced with the science goals and requirements. One of the top-level telescope trades examines the impact of a large monolithic primary mirror versus an array of smaller mirror segments to either fully or sparsely populate the same aperture. The first consideration is the scientific impact. Should the scattered edge effects and diffraction of a segmented design be acceptable, it then becomes a fabrication, test, and cost trade along with any associated risks. This paper will examine some of the key factors that go into such a trade and looks at manufacturing breakpoints. Examples such as the 4-m aperture New World Observer (NWO) and the 8-m aperture Advanced Technology Large Aperture Space Telescope (ATLAST) will be presented.

Aspheric surfaces can provide significant benefits to optical systems, but manufacturing high-precision aspheric surfaces is often limited by the availability of surface metrology. Traditionally, aspheric measurements have required dedicated null correction optics, but the cost, lead time, inflexibility, and calibration difficulty of null optics make aspheres less attractive. In the past three years, we have developed the Subaperture Stitching Interferometer for Aspheres (SSI-A®) to help address this limitation, providing flexible aspheric measurement capability up to 200 waves of aspheric departure from best-fit sphere. Some aspheres, however, have hundreds or even thousands of waves of departure. We have recently developed Variable Optical Null (VON^TM) technology that can null much of the aspheric departure in a subaperture. The VON is automatically reconfigurable and is adjusted to nearly null each specific subaperture of an asphere. The VON provides a significant boost in aspheric measurement capability, enabling aspheres with up to 1000 waves of departure to be measured, without the use of null optics that are dedicated to each asphere prescription. We outline the basic principles of subaperture stitching and the Variable Optical Null, demonstrate the extended capability provided by the VON, and present measurement results from our new Aspheric Stitching Interferometer (ASI^TM).

Stitching Interferometry is now commonplace in Large Optics workshops. However, this technique is far more difficult to implement than might appear at first sight. More precisely, because stitching involves multiple overlapping measurements, there is huge potential for measurement error amplification. And, because there is usually no element of comparison, finding and correcting error sources is usually tricky. This has brought us to develop error detection and/or correction tools in our Stitching Software, two of which will be discussed and graphically illustrated here: First: Environment stability analysis, including computation of stitching measurements probable fluctuations. This requires no mechanical stage, and can therefore be performed as a preliminary test. Second: Calibration error is often a limiting factor. We have solved this issue, for the 1D case, using the same hardware as that used by the stitching process, and requiring no handling of the component. The 2D case is currently being developed. In this paper, we show results obtained from real measurements performed at Customers' facilities: The graphical stability outputs are very instructive, and the self-calibration technique performs remarkably well.

Based on the difference between theoretical with real interferogram images the figure of original aspheric surface can be obtained using an algorithm of Reverse iterate Optimization Reconstruction (ROR) calculating technique. Because the procedure of ray tracing path needed an accurate geometry of optical structure size so the aspheric and compensator L_C must be located in the optical path. To avoid the compensator L_C resulted in bigger spherical aberration a smart located method is proposed in this paper. Before measurement an aplanatic lens consists of compensator L_C and another removable lens L_M that the last surface is a standard one. So Fiezau interference is formed by the standard one with reflected ray from the vertex of aspheric that the aspheric surface detected can be accurately located. At testing the lenses L_M will be removed and the aspheric is moved to an adapted position. The experiments show the displacement locating accuracy is an amount of micron. The RMS for aspheric testing of ROR calculating technique is better than 1/200 wavelength.

Large, convex surfaces, such as secondary mirrors, have presented challenging metrology problems for many years. Over the years, new metrology approaches have been developed to keep pace with the ever changing definition of "large". The latest class of large secondary mirrors requires a new approach that is practical, scalable and can produce low uncertainty measurements. This paper presents a new configuration that uses a computer generated hologram based Fizeau interferometer to make sub-aperture measurements on large secondary mirrors. One of the key features of this system is that all of the surfaces used in the interferometer are spherical. Another key element is the ability to perform simultaneous phase shift interferometry which reduces sensitivity to vibration. An example system that is capable of measuring the Large Synoptic Survey Telescope secondary mirror is presented along with a sensitivity analysis.

The random ball test (RBT), also known as the CaliBall test, is often used to calibrate interferometer transmission spheres. This paper provides a way to estimate the total errors remaining after interferometer calibration using the RBT. Errors that cannot be removed by calibration include random errors due to measurement noise in the calibration, geometric errors, and errors due to diffraction. The random errors can be reduced by averaging multiple random ball tests. The geometric errors and diffraction errors are systematic, and arise when the radius of the CaliBall is different from that of the test optic.

We developed a complete and orthonormal set of vector polynomials defined over a unit circle. One application of these vector polynomials is for fitting the mapping distortions in an interferometric null test. This paper discusses the source of the mapping distortions and the approach of fitting the mapping relations, and justifies why the set of vector polynomials is the appropriate choice for this purpose. Examples are given to show the excellent fitting results with the polynomials.

The scanning pentaprism test has provided an important absolute test method for flat mirrors, parabolic mirrors and also collimation systems. We have developed a scanning pentaprism system to measure off-axis paraboloidal mirrors such as those for the Giant Magellan Telescope (GMT) primary mirror. Special characteristics of the pentaprism testing of an off-axis mirror are discussed in the paper. We provide performance results for the final measurement of a 1.7 m off-axis parabolic mirror and present a technique used to determine the radius of the parent, off-axis distance and the clocking of the mirror from the data from the scanning pentaprism system.

The main feature of the compound diffractive telescope is the combination of diffractive optics with compound structure arranged eyepieces. In this paper, a design of the compound diffractive telescope is firstly introduced, and a 4.2° FOV is obtained with one primary lens and twenty-one eyepieces. Secondly, image characteristic of different channels is analyzed with the design wavelength in ASAP, and one modified phase function model of diffractive optical element is introduced to analyze the MTF curves for 0° FOV, which provides a more accurate prediction of the performance of the system. Then the system is tested by the star image test, and the diffraction limit images are got within ± 2° FOV. And finally, two pictures taken from the adjacent FOV proved to be able to be spliced together. All the results above demonstrate that a good performance of the compound diffractive telescope.

The auto-focusing is one of the important parts in the automated vision inspection or measurement using optical microscopes. Moreover, laser micromachining or laser lithography requires a high speed and precision auto-focusing. In this paper, we propose and realize an auto-focusing system using two cylindrical lenses, which is the enhanced version of the previous astigmatism method. It shows very good performances, especially very high speed and the largest defocusing range in comparison with the previous astigmatic methods. The performance of our auto-focusing system was evaluated by tracing the linear stage whose position was monitored by a commercial laser interferometer.

In the INAF-Astronomical Observatory of Brera (INAF-OAB) a new Ion Beam Figuring Facility, that adds to the previous one, is under advanced construction. The present facility is able to figure optics up to 50 cm in diameter meanwhile the new one is larger and will be able to figure optics up to 1.7 meter. It will employ a Kaufman Ion Source having three degrees of freedom (x-y-z) with step motors and encoders. The source will have two different grid sizes so to be able to figure the optics wit a broad or small removal function depending from the application. The control system will be computer controlled and designed to be autonomous and self-monitoring during the figuring by using a proprietary process control software. This software will use a time matrix map indicating the dwell times required for each pixel of the optical surface. The software and the mathematical tools used to compute the Time Matrix solution has been developed in INAF-OAB as well.

We propose a new method based on direct laser writing to fabricate reference chromium patterns on a silicon wafer. Our method is able to fabricate a maximum 360-mm-diameter pattern with 651-nm position uncertainty. The minimum pattern size is about 0.8 μm (line width value) and the maximum available height of the pattern is slightly over 400 nm.

We have developed a metrology system that is capable of measuring rough ground and polished surfaces alike, is nearly independent of the nominal surface shape, and can accommodate surfaces up to 8.4 m in diameter. The system couples a commercial laser tracker with an advanced calibration technique and a system of external references. This system was built to guide loose abrasive grinding and initial polishing of the off-axis primary mirror segments for the Giant Magellan Telescope, and will be used to guide the fabrication of the Large Synoptic Survey Telescope primary and tertiary mirrors as well. The results obtained using this system during the fabrication of the first segment of the Giant Magellan Telescope are presented along with an assessment of the expected system accuracy.

We investigated the process of laser micro-drilling of copper and iron by using nanosecond laser-pulses at 532nm wavelength in atmospheric air. We analyzed the ablated volume, ablation rate, crater diameter, and craters quality as functions of laser-fluence and beam-diameter. The fluence was varied between 10 and 6000 J/cm² by changing the laserenergy. The results indicate that the ablated volume increases linearly with fluence, whereas the ablation rate and crater diameter increase linearly with the fluence's square root. The ablated volume, ablation rate, and crater diameter, increase with thermal diffusivity of the materials. Additionally, the ablation threshold-fluence is demonstrated to be directly related to the optical penetration depth. The ablated volume, ablation rate, and crater diameter were further assessed for beam-diameters in the range of 10-50 microns by translating the targets away from the focal plane while keeping a constant fluence. The results indicate that the ablated volume increases linearly with beam-diameter, whereas the ablation rate and crater diameter increase linearly with the inverse of the beam-diameter's square root. To investigate the craters quality we measured the dimension of the thermally affected zone (TAZ) around the craters as a function of fluence. At fluences up to 400 J/cm², where strong ionization occurs within the plume, the crater diameter is <15 microns (comparable with beam diameter) and there is small TAZ around the craters. Further increase of the fluence leads to a significant increase of TAZ, indicating that the expanding plasma plays a major role in metals ablation in this fluence domain.

Today elastic membranes are being used more frequent as optical surfaces in the science or in the industry. This due to the advantages that they display in their handling and in their cost of production. These characteristics make them ideals to apply them in micro-optical components and Tunable Focus Liquid Filled Length Lens (TFLFLL). In order to know if a membrane of PDMS (PDMS Sylgard 184) is feasible for a specific application within the field of the optics, it is necessary to know its mechanical, optical and chemical properties. In this work the parametric membrane characterization is reported for an optical application. An important factor in the performance of these membranes is related with their scattering factor that is produced due to the roughness and impurities (micro-bubbles or dust particles). These membranes are used as refractive surface in TFLFLL. Experimental results of the characterization process and device performance are presented.

Computer Generated Holograms (CGH) for optical test are commonly consisted of one main pattern for testing aspheric surface and some alignment patterns for aligning the interferometer, CGH, and the test optics. To align the CGH plate and the test optics, we designed the alignment CGHs modified from the cat's eye alignment method, which are consisted of a couple of CGH patterns. The incident beam passed through the one part of the alignment CGH pattern is focused onto the one radius position of the test aspheric surface, and is reflected to the other part, and vice versa. This method has several merits compared to the conventional cat's eye alignment method. First, this method can be used in testing optics with a center hole, and the center part of CGH plate can be assigned to the alignment pattern. Second, the alignment pattern becomes a concentric circular arc pattern. The whole CGH patterns including the main pattern and alignment patterns are consisted of only concentric circular fringes. This concentric circular pattern can be easily made by the polar coordinated writer with circular scanning. The required diffraction angle becomes relatively small, so the 1^st order diffraction beams instead of the 3^rd order diffraction beam can be used as alignment beams, and the visibility can be improved. This alignment method also is more sensitive to the tilt and the lateral shift of the test aspheric surface. Using this alignment pattern, a 200 mm diameter F/0.5 aspheric mirror and a 600 mm diameter F/0.9 mirror were tested.