Volume 1, Issue 3

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No abstract available.

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No abstract available.

Micro-optics represents a rich discipline with many features not found in classical optics. Yet micro-optics is not merely ‘small optics’. Using the technologies of microfabrication, entirely new fabrication processes, new materials and new types of optical devices have been conceived. Here, we provide a brief introduction to the field, discussing a variety of miniaturized optical components, as well as the materials from which they are made and the novel technologies used to fabricate them. Designed as a tutorial, this brief précis includes adequate literature references to guide the interested reader to more in-depth treatments.

Engineered diffusers are refractive, achromatic optical elements with the capability to not only spread and homogenize an input beam but also shape the distribution of energy as well as intensity profiles. Bandlimited illumination is of particular interest for many applications that require certain intensity profiles over specific angular range with maximum efficiency. Here, we describe the concept and design of engineered diffusers as well as the method to fabricate them, from the initial resist master to volume production. Engineered diffusers are found to provide nearly ideal bandlimited illumination without image artifacts and with acceptable manufacturing tolerances.

Micro-optics is an indispensable key enabling technology for many products and applications today. Probably the most prestigious examples are the diffractive light shaping elements used in high-end DUV lithography steppers. Highly-efficient refractive and diffractive micro-optical elements are used for precise beam and pupil shaping. Micro-optics had a major impact on the reduction of aberrations and diffraction effects in projection lithography, allowing a resolution enhancement from 250 nm to 45 nm within the past decade. Micro-optics also plays a decisive role in medical devices (endoscopes, ophthalmology), in all laser-based devices and fiber communication networks, bringing high-speed internet to our homes. Even our modern smart phones contain a variety of micro-optical elements. For example, LED flash light shaping elements, the secondary camera, ambient light and proximity sensors. Wherever light is involved, micro-optics offers the chance to further miniaturize a device, to improve its performance, or to reduce manufacturing and packaging costs. Wafer-scale micro-optics fabrication is based on technology established by the semiconductor industry. Thousands of components are fabricated in parallel on a wafer. This review paper recapitulates major steps and inventions in wafer-scale micro-optics technology. The state-of-the-art of fabrication, testing and packaging technology is summarized.

In this review, we describe our method for creating holograms of incoherent objects, dubbed Fresnel incoherent correlation holography (FINCH). FINCH creates holograms by a single-channel on-axis incoherent interferometer process. Like any Fresnel hologram, the object is correlated with quadratic phase functions, but the correlation is carried out without any movement. Generally, in the FINCH system, light is reflected, or emitted, from a three-dimensional (3D) object, propagates through a spatial light modulator (SLM), and is recorded by a digital camera. The SLM is used as a beam-splitter of the single-channel incoherent interferometer, such that each spherical beam originated from each object point is split into two spherical beams with two different curve radiuses. Incoherent summing of the entire interferences between all the couples of the spherical beams creates the Fresnel hologram of the observed 3D object. When this hologram is reconstructed in the computer, the 3D properties of the object are revealed. In this review, we describe various aspects of FINCH which have been described recently, including FINCH of reflected white light, FINCH of fluorescence objects, a FINCH-based holographic fluorescence microscope, a FINCH configuration which capitalizes on the polarization sensitivity of the SLM and finally FINCH is analyzed in view of linear system theory.

We present the latest results in the fabrication of micro-optical components using a novel nanostructuring process. This low-cost fabrication technology, which exploits advances in the development of photonic crystal fibres, uses a modified stack-and-draw technique where macroscopic distributions of thermally and mechanically matched glasses are reduced in scale by repeated draw-down and restacking procedures until the individual glass features are significantly below the wavelength of incident light. We demonstrate that this fabrication technique is suitable for the creation of large diameter high numerical aperture micro-lenses for light collection and concentration purposes and broadband form birefringent materials.

We present wide-band resonance waveguide reflectors at the visible wavelengths providing nearly 100% reflectance over a range of several tens of nanometres. The reflectors are based on multilayer designs consisting of layers of high and low index materials with a binary grating etched through the stack. We also fabricated an example structure and discuss the fabrication aspects of these elements.

The combination of diffractive and refractive elements in hybrid optical systems allows for precise control of the longitudinal chromatic aberration. We provide comprehensive design strategies for hybrid hyperchromatic lenses that maximise the longitudinal chromatic aberrations. These lenses are mainly used in chromatic confocal sensor systems for efficient non-contact profilometry as well as for measurements of distances and wall thicknesses of transparent materials. Our design approach enables the tailoring of the sensor properties to the specific measurement problem and assists designers in finding optimised solutions for industrial applications. We, for example, demonstrate a hybrid system that significantly exceeds the longitudinal chromatic aberration of purely diffractive elements.

We present a numerical gradient-index (GRIN) design methodology for application in coherent mode conversion. Within the framework of geometric optics, a one-to-one correspondence between the field description and the ray description of the propagating beam is established using optical path lengths and the conservation of energy within a bundle of rays. A family of ray paths is chosen to transform the initial ray distribution into a target ray distribution. The specified ray paths are used to calculate the index profile of the GRIN structure required to effect the gradual transformation from the input beam to the desired output beam. We demonstrate our approach with a GRIN structure design that converts a Gaussian beam into a flat-top beam.

Modern phase shifting interferometers enable the manufacture of optical systems that drive the global economy. Semiconductor chips, solid-state cameras, cell phone cameras, infrared imaging systems, space based satellite imaging and DVD and Blu-Ray disks are all enabled by phase shifting interferometers. Theoretical treatments of data analysis and instrument design advance the technology but often are not helpful towards the practical use of interferometers. An understanding of the parameters that drive system performance is critical to produce useful results. Any interferometer will produce a data map and results; this paper, in three parts, reviews some of the key issues to minimize error sources in that data and provide a valid measurement.

No abstract available.