Fabrication Of Lenses Research Articles

Hardness Improvement of Chalcogenide Glasses

In and Bi were doped into 30Ge10Sb60Se and 27.5Ge12.5Sb60Se glasses to improve hardness. While Bi did not have any influence on hardness, In made 10% hardness improvement in 27.5Ge12.5Sb60Se glass. Over 8wt% In doping triggered crystallization of In2Se3 so that IR transmittance was degraded below 10%. In2Se3 crystallization was confirmed by XRD and FE-SEM. I. Introduction Recently, night vision system has been used in a various fields such as military, aircrafts, and cars. Since infrared lens components based on monocrystalline Ge or polycrystalline ZnSe were very expensive in the early days, it was used only for military application [1]. However, its applications have been widely expanded to civilian ones such as cars and even mobile phones by adapting moldable chalcogenide glasses which have low phonon energy, good thermal stability, and especially high infrared transparency up to 12 um [2]. Se-based chalcogenide glasses which have optical transparency up to 10um are assumed as attractive candidates for moldable chalcogenide glasses lens compared with S-based or Te-based chalcogenide glasses. Among several ternary Se-based glasses, especially, Ge-Sb-Se ternary glasses are considered as promising ones because they are thermally stable and non-toxic [3]. We have already investigated the optimum chalcogenide glass compositions for moldable lens in terms of IR transmittance, thermal property, and hardness [4]. Among them, hardness has an important role on lens fabrication process as well as final lens product. Here, we want to propose the way to improve hardness by adding additional element to the optimum compositions. II. Experiment Chalcogenide glasses have been made by the conventional fabrication method by rocking furnace. The starting materials (Ge, Sb, Se, In and Bi) were weighed and put into a silica ampule in a glove box filled with Ar gas. Glasses were melted in a 3 zone rocking furnace at 1000 °C for 12hrs and quenched into water followed by annealing. Synthesized glasses were cut and polished to measure properties such as Vickers hardness, IR transmittance (Perkin-Elmer, Spectrum 100), and surface morphology. III. Results and discussions The additional element which was chosen to improve hardness was determined in terms of binding energy and tendency of glass forming ability. In (Indium) and Bi (Bismuth) were doped with the optimum composition glasses such as 30Ge10Sb60Se and 27.5Ge12.5Sb60Se. Based on the reference literature, In and Bi were doped by 3, 5wt% and 8wt%, respectively. Each glass was cut and polished in the upper part, middle part, and lower part to confirm the homogeneity of glass. IR transmittance and Vickers hardness were measured for each sample. Since each sample from one glass showed almost similar IR transmittance and Vickers hardness, synthesized glasses seem to be homogeneous. The tendency of In and Bi doping on IR transmittance and Vickers hardness was investigated more detail. IR transmittance of In and Bi doped 30Ge10Sb60Se glasses showed almost similar value except 5wt% In doped glass. 5wt% In doped 30Ge10Sb60Se glass showed lower than 50% IR transmittance. However, doping of In and Bi has not an effect on Vickers hardness at all. In and Bi doped 27.5Ge12.5Sb60Se glasses showed a little different trend. Vickers hardness of Bi doped 27.5Ge12.5Sb60Se glasses did not show any improvement. On the other hand, 3wt% and 5wt% In doped 27.5Ge12.5Sb60Se glasses showed about 10% Vickers hardness improvement while IR transmittance property remains over 60%. IR transmittance of 8wt% In doped 27.5Ge12.5Sb60Se glass decreased below 10%, which means In should be doped under 8wt%. In order to confirm the reason of IR transmittance decrease, XRD and FE-SEM analyses were done. According to XRD results, 8wt% In doped 27.5Ge12.5Sb60Se glass showed In2Se3 peak while other glasses did not show any other sharp peaks related to crystallization. In addition, small particles which are related to In2Se3 crystallization were observed on the surface of 8wt% In doped 27.5Ge12.5Sb60Se glass in FE-SEM image References [1] X.H. Zhang, Y. Guimond, Y. Bellec, J. Non-Cryst. Solids 326&327 (2003) 519 [2] E. Guillevic, X.H.Zhang, T. Pain, L. Calvez, J.L. Adam, J. Lucas, Opt. Mater. 31 (2009) 1688 [3] D.R. Goyal, A.S. Maan, J. Non-Ctryst. Solids 183 (1995) 182 [4] J.H. Lee, W.H. Lee, J.K. Park, J.H. Yi, S.Y. Shin, B.J. Park, B. So, J. Heo, J.H. Choi, H.J. Kim, Y.G. Choi, J. Non-Ctryst. Solids, to be published (2016) Figure 1

Fabrication and Analyses of Bionic Polymer Lens System

In this paper, we design and fabricate a bionic solid tunable lens which is mainly made of polymer materials. The lens focal length can be changed flexibly by pressing the lens surface to alter the curvature radius. A detailed description of the lens structure, materials and fabrication process is presented. The lens mechanical properties and deformation process are simulated and analyzed using Ansys software. A precise experimental device based on a stepping motor is fabricated to measure and analyze the relationship between the displacement load and focal length. The lens focal length can be reversibly changed from 31.8 to 14.1 mm under 1 mm variation of displacement load. This paper offers a feasible way for the design, fabrication, and actuation of the solid tunable lens, which can be used in various machine vision apparatus.

SU-8 Lenses: Simple Methods of Fabrication and Application in Optical Interconnection Between Fiber/LED and Microstructures

This paper presents two facile methods to fabricate off-plane lenses made of SU-8, an epoxy-based negative photoresist from MicroChem, on glass for optical interconnection. The methods allow the fabrication of lenses with flexible spot size and focal length depending on SU-8 well size and SU-8 drop volume and viscosity. In the first method, SU-8 drops were applied directly into patterned SU-8 wells with Teflon-coated micropipettes, and were baked to become (a)-spherical lenses. The lens shape and size were mainly determined by SU-8 viscosity, ratio of drop volume to well volume, and baking temperature and time. In the second method, a glass substrate with SU-8 patterned wells was emerged in diluted SU-8, then drawn up and baked to form lenses. The lens shapes and sizes were mainly determined by SU-8 viscosity and well volume. By the two methods, SU-8 lenses were successfully fabricated with spot sizes varying in range from micrometers to hundred micrometers, and focal lengths varying in range of several millimeters, depending on the lens rim diameters and aspheric sag height. Besides, on-plane SU-8 lenses were fabricated by photolithography to work in conjunction with the off-plane SU-8 lenses. The cascaded lenses produced light spots reduced to several micrometers, and they can be applied as a coupler for light coupling from fiber/Light-emitting diode (LED) to microstructures and nanostructures. The results open up the path for fabricating novel optical microsystems for optical communication and optical sensing applications.

Tubular Focus-Tunable Fluidic Lens Based on Structured Polyimide Foils

We demonstrate an entirely new means for fabrication of focus-tunable fluidic lenses using a tubular geometry with great design flexibility. The technology is based on patterned, flexible polymeric foils inserted into a cylindrical tube, which is filled with two liquids of different refractive indices. Electrowetting is used for actuation of the liquid/liquid interface, thus realizing focus tunability. To show the utility of this approach, a single liquid lens with a 4.5-mm aperture and of a back focal length tuning by a factor of 7, requiring actuation voltages below 100 Vrms, is demonstrated. The tubular geometry optical resulted in a high optical surface quality over the entire actuation range, with rms values for wavefront error below λ/2, is dominated by spherical aberration.

Fabrication of polycrystalline diamond refractive X-ray lens by femtosecond laser processing

X-ray planar compound refractive lenses were fabricated from a polycrystalline diamond plate grown by chemical vapor deposition, by precise through cutting with femtosecond laser pulses. The lens geometry and the surface morphology were investigated with optical and scanning electron microscopy, while the material structure modification was analyzed by Raman spectroscopy. The results of the preliminary lens test at 9.25-keV X-rays are presented.

Tunable Liquid Crystal Lens Based on Pretilt Angle Gradient Alignment

ABSTRACTThe new method of LC lenses fabrication based on innovative alignment material for pretilt angle gradient generation is developed. The alignment layer provides LC lens pretilt angle gradient via two-step treatment: uniform rubbing and gradient nonpolarized UV exposure. LC lens has uniform cell-gap, 2–10 V tunable voltage range. The fabrication method is scalable for lens arrays for two-dimensional/three-dimensional autostereoscopic and light-field displays.

Long-Working-Distance Grating Coupler for Integrated Optical Devices

A novel grating coupler design is presented with its experimental demonstration. The grating can focus the outcoming light upward without the need for a lens or additional fabrication steps. The lenslike effect is introduced by applying a deformation to the grating stripes in order to add a phase map that matches the phase of the spherical wavefront coming from the fiber. The presented grating is designed for silicon photonics technology and has a working distance of 230 $\mu\text{m}$ to a standard single-mode fiber. This long distance would introduce an excess loss of 9 dB with a standard grating, whereas with the long-working-distance grating, we demonstrate no extra loss with respect to the standard grating.

Fabrication and characterization of high-efficiency double-sided blazed x-ray optics.

The focusing efficiency of conventional diffractive x-ray lenses is fundamentally limited due to their symmetric binary structures and the corresponding symmetry of their focusing and defocusing diffraction orders. Fresnel zone plates with asymmetric structure profiles can break this limitation; yet existing implementations compromise either on resolution, ease of use, or stability. We present a new way for the fabrication of such blazed lenses by patterning two complementary binary Fresnel zone plates on the front and back sides of the same membrane chip to provide a compact, inherently stable, single-chip device. The presented blazed double-sided zone plates with 200 nm smallest half-pitch provide up to 54.7% focusing efficiency at 6.2 keV, which is clearly beyond the value obtainable by their binary counterparts.

Enhanced Terahertz Transmission Through Bullseye Plasmonics Lenses Fabricated Using Micromilling Techniques

Imaging applications at terahertz frequencies are, in general, limited to relatively low spatial resolution due to the effects of diffraction. By using a subwavelength aperture in the near-field, however, it is possible to achieve subwavelength resolution, although low transmission through the aperture limits the sensitivity of this approach. Plasmonic lenses in the form of bullseye structures, which consist of a circular subwavelength aperture surrounded by concentric periodic corrugations, have demonstrated enhanced transmission, thereby increasing the utility of near-field imaging configurations. In this paper, the design, fabrication, and experimental performance of plasmonic lenses optimized for 300 GHz are discussed. While nanofabrication techniques are required for optical applications, microfabrication techniques are sufficient for terahertz applications. The process flow for fabricating a double-sided bullseye structure using a precision micromilling technique is described. Transmission and beam profile measurements using a customized terahertz testbed are presented.

Mechanically tunable aspheric lenses via additive manufacture of hanging elastomeric droplets for microscopic applications

Mechanically deformable lenses with dynamically tunable focal lengths have been developed in this work. The fabricated five types of aspheric polydimethylsiloxane (PDMS) lenses presented here have an initial focal length of 7.0, 7.8, 9.0, 10.0 and 10.2 mm. Incorporating two modes of operation in biconvex and concave–convex configurations, the focal lengths can be tuned dynamically as 5.2–10.2, 5.5–9.9, 6.6–11.9, 6.1–13.5 and 6.6–13.5 mm respectively. Additive manufacturing was utilized to fabricate these five types of aspheric lenses (APLs) via sequential layering of PDMS materials. Complex structures with three-dimensional features and shorter focal lengths can be successfully produced by repeatedly depositing, inverting and curing controlled PDMS volume onto previously cured PDMS droplets. From our experiments, we empirically found a direct dependence of the focal length of the lenses with the amount (volume) of deposited PDMS droplets. This new mouldless, low-cost, and flexible lens fabrication method is able to transform an ordinary commercial smartphone camera into a low-cost portable microscope. A few microscopic features can be readily visualized, such as wrinkles of ladybird pupa and printed circuit board. The fabrication technique by successively applying hanging droplet and facile mechanical focal-length-tuning set-up can be easily adopted in the development of high-performance optical lenses.

Single-crystal diamond refractive lens for focusing X-rays in two dimensions.

The fabrication and performance evaluation of single-crystal diamond refractive X-ray lenses of which the surfaces are paraboloids of revolution for focusing X-rays in two dimensions simultaneously are reported. The lenses were manufactured using a femtosecond laser micromachining process and tested using X-ray synchrotron radiation. Such lenses were stacked together to form a standard compound refractive lens (CRL). Owing to the superior physical properties of the material, diamond CRLs could become indispensable wavefront-preserving primary focusing optics for X-ray free-electron lasers and the next-generation synchrotron storage rings. They can be used for highly efficient refocusing of the extremely bright X-ray sources for secondary optical schemes with limited aperture such as nanofocusing Fresnel zone plates and multilayer Laue lenses.

Coloured cornea replacements with anti-infective properties: expanding the safe use of silver nanoparticles in regenerative medicine.

Despite the broad anti-microbial and anti-inflammatory properties of silver nanoparticles (AgNPs), their use in bioengineered corneal replacements or bandage contact lenses has been hindered due to their intense yellow coloration. In this communication, we report the development of a new strategy to pre-stabilize and incorporate AgNPs with different colours into collagen matrices for fabrication of corneal implants and lenses, and assessed their in vitro and in vivo activity.

Single step fabrication and characterization of PDMS micro lens and its use in optocapillary flow manipulation

We report single-step fabrication and characterization of PDMS microlens and demonstrate its use in optocapillary flow manipulation. Mixed PDMS droplets are dispensed over a thermally controlled Si substrate and cured to obtain microlenses. The spreading characteristics of sessile PDMS droplets are measured with time and substrate temperature. The gel-time of PDMS drops is studied for various substrate temperatures. The micro lenses are characterized based on the numerical aperture, focal length, f/number, optical transparency and spot size. Finally, micro lenses are used for focusing light from a low power IR laser for the manipulation of capillary flow in a microchannel.

Optical Design and Fabrication of a Large Telephoto Zoom Lens with Fixed f/2.8 and Light Autofocus Lens

Compact system cameras (CSCs) are commonly used nowadays and feature enhanced video functions and thin yet light interchangeable lenses. They differ from digital single-lens reflex (DSLR) cameras in their lack of mirror boxes. CSCs, however, have autofocus (AF) speeds lower than those of conventional DSLRs, requiring weight reduction of their AF groups. To ensure the marketability of large telephoto zoom lenses with fixed f/2.8 regardless of field angle variation, in particular, light weight AF groups are essential. In this paper, we introduce a paraxial optical design method and present a new, large, telephoto zoom lens with f/2.8 regardless of the field angle variation, plus a lightweight AF group consisting of only one lens. Using the basic paraxial optical design and optimization methods, we fabricated a new and lighter zoom lens system, including a single-lens, lightweight AF group with almost the same performance.

Large elliptical nanostructured gradient-index microlens.

We demonstrate the feasibility of the development of a gradient-index elliptical microlens with a size of 75×125 μm using nanostructured glass technology. The gradient index is obtained by means of a discrete internal structure composed of two glasses with feature sizes much smaller than the wavelength of the incident light. A modified photonic crystal fiber-drawing technique is used for the lens fabrication. The elliptical shape of the lens is obtained by a novel final drawing stage where the spherically symmetric lens preform is drawn into an elliptical form by collapsing two large air holes placed in the preform during assembly. The effective focal lengths of 160 and 260μm for the orthogonal axes are obtained experimentally for the fabricated lens, and show good agreement with those predicted by the effective medium theory and the full-wave beam propagation simulations.

Wafer-level fabrication of multi-element glass lenses: lens doublet with improved optical performances.

This Letter reports on the fabrication of glass lens doublets arranged in arrays and realized at wafer level by means of micro-fabrication. The technique is based on the accurate vertical assembly of separately fabricated glass lens arrays. Since each one of these arrays is obtained by glass melting in silicon cavities, silicon is employed as a spacer in order to build a well-aligned and robust optical module. It is shown that optical performance achieved by the lens doublet is better than for a single lens of equivalent numerical aperture, thanks to lower optical aberrations. The technique has good potential to match the optical requirements of miniature imaging systems.

An imaging spectrometer employing tunable hyperchromatic microlenses.

We present the design, fabrication and characterization of hydraulically-tunable hyperchromatic lenses for two-dimensional (2D) spectrally-resolved spectral imaging. These hyperchromatic lenses, consisting of a positive diffractive lens and a tunable concave lens, are designed to have a large longitudinal chromatic dispersion and thus axially separate the images of different wavelengths from each other. 2D objects of different wavelengths can consequently be imaged using the tunability of the lens system. Two hyperchromatic lens concepts are demonstrated and their spectral characteristics as well as their functionality in spectral imaging applications are shown.

Bionic intraocular lens with variable focus and integrated structure

This paper proposes a bionic accommodating intraocular lens (IOL) for ophthalmic surgery. The designed lens has a solid–liquid mixed integrated structure, which mainly consists of a support ring, elastic membrane, rigid lens, and optical liquid. The lens focus can be adjusted through the deformation of the lens front surface when compressed. The integrated structure of the IOL is presented, as well as a detailed description of the lens materials and fabrication process. Images under different radial pressures are captured, and the lens deformation process, accommodating range, density, and optical property are analyzed. The designed lens achieves a 14.6 D accommodating range under a radial pressure of 51.4 mN and a 0.24 mm alteration of the lens outer radius. The deformation property of the lens matches well with the characteristic of the eye and shows the potential to help patients fully recover their vision accommodation ability after the cataract surgery.

Design and fabrication of microwave flat lenses using a novel dry powder dot deposition system

We describe a new methodology for creating flat lenses operating in the microwave spectrum using a custom designed additive manufacturing system. This method utilizes a novel dry powder 3D printing system to achieve graded index lenses integrated within a structural composite. We also describe a new iterative dot patterning algorithm to achieve a desired graded dielectric distribution, and we compare the iterative dot patterning algorithm to other dot patterning techniques. Computational and experimental results are provided validating the design and fabrication process.

Fabrication of a multilevel THz Fresnel lens by femtosecond laser ablation

The possibility of fabricating a silicon diffractive four-level THz Fresnel lens by laser ablation is studied. For a microrelief to be formed on the sample surface, use is made of a femtosecond Yb : YAG laser with a high pulse repetition rate . Characteristics of the diffractive optical element are investigated in the beam of a free-electron laser. The measured diffraction efficiency of the lens is in good agreement with the theoretical estimate.