An innovative fabrication technique is introduced that is based on multiple exposure techniques for micro-optics fabrication. This approach is compatible with conventional lithography systems used in Integrated Circuit manufacturing and can be applied to thick and thin photoresists. The additive concept is centered on the idea of using multiple exposures to remove the desired amount of resist without resorting to multiple etching steps. This presentation will explain how the additive technique, used with thin and thick resists, will revolutionize our capability to efficiently form refractive lenses and micro-optics for optical beam shaping and transforming. The quality and reproducibility of these elements will also be discussed.

Ever-increasing demands of smaller feature sizes and larger throughputs have catapulted the semicondutor lithography juggernaut to develop immensely complex and expensive systems. However, it is not clear if the lithography needs for microoptic and other “botique” device fabrication are being addressed. ZPAL is a new nanolithography technique which leverages advances in micromechanics and diffractive optics technologies. We present ZPAL as the ideal system for such non-conventional lithography needs.

A hybrid phase and amplitude modulation proximity printing mask was designed, manufactured and tested. The proposed diffractive structure modulates both the phase and the amplitude of a UV exposure beam. In the fused silica substrate a relief is generated in order to modulate the phase and a patterned diamond like carbon layer modulates the amplitude of the UV light. Besides, the diamond like carbon thin film is partially transparent at wavelengths larger than 400 nm, what improves the alignment procedures between different mask levels. The lithographic image was projected onto a resist coated silicon wafer, placed at a distance of 50 micrometer behind the mask, obtaining a resolution better than 1 micrometer, what is impossible with traditional proximity printing techniques.

We have developed a material system, a fabrication process, and optical designs that allow for direct integration of patternable optical components onto microelectronics and optoelectronics platforms. The spin-on-glass is a sol-gel platform that has a low waveguide loss with the ability to incorporate a waveguide amplifier. Our material and process includes the ability to fabricate 3-D structures in a single photolithography step. In this paper, we present details of our fabrication process, general materials characteristics, and some optical designs for planar lightwave circuit platforms.

This paper pertains to the development of a system for micro replication that has been successfully implemented on a conventional flexographic printing machine. The core technology in the system is UV assisted rotational moulding using an elastomer as the micro mould and UV curable polymers as the casting material.

In this paper, a detailed study of replication of microlenses by UV-assisted moulding in hybrid glass materials is presented. Circular aspherical, spherical and cylindrical microlenses were designed and fabricated in photoresist by using the grey-scale lithography based on high-energy beam sensitive glass. A semi-transparent replication master was then generated. Hybrid organic-inorganic resins were synthesized by sol-gel processing of functionalized alkoxysilanes. The resin viscosity and refractive index depended on synthesis conditions. Transparent, well adhering, several tens of microns-thick films were deposited on fused silica substrates by adjusting the solvent content of the formulation. The thermal expansion coefficient of our material, determined by a Michelson interferometric technique was 1.75 10^-4 K^-1. High replication fidelity e. g. better than 5% is demonstrated by controlling changes, at the various process steps, in the radius of curvature i.e. focal lengths of microlenses performing the measurements with a Twyman-Green interferometer. Close to diffraction limited microlenses with f-numbers ranging from f/1.4 to f/10 were fabricated.

An experimental method is presented to maximize the replication quality of UV-molded micro-optical components. It is important to maximize the replication quality, because one can obtain the replicated micro-optical components with desired properties by accurate control of the shape. In the present study, a simple technique to avoid micro-air bubbles was first suggested. The effects of the UV-curing dose and the compression pressure on the replication quality of UV-molded structure were examined experimentally. Finally, as a practical application of the process design method, micro-lens arrays with diameters between 8μm and 230μm were fabricated by the present method, and the replication quality and the optical properties of the replicated micro-lens were measured and analyzed.

This paper describes that arbitrary three-dimensional photonic crystals, so called fourteen Bravais lattices, and even a diamond structure can be fabricated by recording the four plane-waves interference fringe. It is derived that the equation of maximum intensity point condition for interference fringe among four plane waves is the same as that between the lattice vectors and the reciprocal lattice vectors in the solid-state physics. This relation gives us the way to calculate the incident directions for four plane waves to fabricate any desired three-dimensional photonic crystal structures. The diamond structure consists of two same face centered cubic lattices, which are shifted by a quarter of their lattice constant to each other. This shift can be introduced by shifting the phases of four plane waves for interference. Therefore, the diamond structure can be fabricated by double exposures without and with phase shifts. Experimentally, a face centered cubic lattice structure was fabricated in the positive photoresist layer by using a He-Cd laser. The polarization directions of four beams were adjusted to obtain a maximum interference modulation depth. The SEM observation and the diffraction pattern observation of the fabricated sample show that the fabricated structure has a face centered cubic periodic structure.

We report on the design and fabrication of diffractive optical elements on high power broad area semiconductor lasers. Several issues related to the integrated diffractive elements fabrication by electron beam lithography and focused ion beam are discussed. We illustrate the flexibility of electron beam lithography by presenting results for beam focusing, splitting and tapering functions. An additional technique based on focused ion beam milling is presented for fabricating refractive lens elements onto the laser diode.

In this paper we present the development of several new and novel fabrication methods for the realization of two-dimensional photonic crystal devices in silicon slab waveguides. We begin by presenting a process for the fabrication of high fill-factor devices in silicon-on-insulator wafers. Next, we present a grayscale fabrication process for the realization of three-dimensional silicon structures, such as tapered horn couplers. We then present the fabrication of suspended silicon slabs using a co-polymer process based on direct write electron beam lithography and silicon sputtering. And lastly, we conclude by presenting an alternate method for realizing PhC devices in a silicon slab based on a combination of wet and dry etching processes in bulk silicon wafers.

The methods of fabricating infrared antennas using electron beam lithography will be investigated. For this purpose, a process using a bi-layer lift off process and a single layer of resist has been developed. The bi-layer lift off process used allowed for antenna arm resolution of 200nm. The single layer resist process enhanced the resolution of the antenna arms to 90nm by using a Chlorine based reactive ion etcher with Chrome as an etch mask. An alignment scheme using a set of global and local marks allowed for an overlay accuracy of 25nm. An improved process was developed to further improve device yield and uniformity of the infrared detectors by sputtering the bolometer and using an oxygen descum to remove residual resist between antenna and bolometer. Two separate methods of fabrication of air-bridge microstrip antenna-coupled microbolometers using both a critical point dryer and an isotropic reactive ion etcher will also be introduced.

The advance in microlithography has greatly helped the development of microoptical elements. Large array of microlenses can now be fabricated in the same fashion as manufacturing of integrated circuits. Because most of the microoptical elements require well-defined and continuous surface relief profile, special methods are needed to supplement to the normal microlithography to produce those relief structures. One of the techniques is greyscale lithography, including electron and laser beam direct write and greyscale photolithography. In this paper, the development of greyscale photolithography is reviewed, in comparison with the direct write techniques. The new development in coding method for greyscale mask is introduced. The importance of correcting non linearity in optical imaging and resist development is discussed. A discussing is also devoted to practical issues in mask fabrication, thick resist patterning and pattern transfer process.

This paper reports on the manufacturing of a novel type of retroreflecting sheeting material. The geometry presented has high reflection efficiency even at large incident angles, and it can be manufactured at low cost through polymer replication techniques. The paper consists of two parts. A theoretical section outlining the design parameters and their impact on the optical performance, and secondly, an experimental part comprising both manufacturing and optical evaluation for a candidate retroreflecting sheet material in traffic control devices. Experimental data show that the retroreflecting properties are promising. The retroreflector consists of a front layer of densely packed spherical microlenses, a back surface of densely packed spherical micromirrors, and a transparent spacer layer with a thickness equal or not equal to the focal length of the lens. The master structures for the lens and mirror sides of the retroreflector were produced by thermal reflow of photoresist pads on silicon wafers. The silicon master structures were transferred into metallic counterparts by electroforming. The casting of the retroreflector was then done in a cavity being limited by the respective mould inserts for the lens and mirror sides.

A novel concept of perpendicular magnetic anisotropy is applied to electromagnetic micro-optical switch (EMOS). In the study, Fe/Pt equiatomic alloy thin film is potential high-density recording media and high-energy permanent magnetic because of their exceptional magnetic properties. EMOS combines of new type Fe/Pt alloy thin film, innovative design of closed magnetic circuit and single layer planar coil. The Fe/Pt alloy thin film and magnetic circuit with close loop is applied to concentrate the magnetic flux, increase magnetic force, and decrease switching time. In this EMOS, some important features are summarized as follows: (1) high magnetic force (>68mN); (2) low work voltage (<5V); and (3) short switching time (<0.4ms). The work demonstrates that EMOS can provide excellent performance than conventional magnetic microactuator.

The output from a laser diode is not circularly symmetric, the output divergence in one axis is much greater than that in the transverse axis. MEMS Optical has developed a laser diode circularizer1 that can take the elliptical output beam from a laser diode and circularize the beam. Due to it’s operating principle, it has a major advantage in that precise alignment is not required, making assembly operations much simpler and faster. Due to the ability to manufacture this device in wafer scale, it can be economically manufactured. We report here the results of a series of optical performance measurements, including wavefront phase and Strehl ratio. Designed for a wavelength of 650nm, it has less than 0.05 waves of wavefront error, Strehl ratios as high as 98%, efficiency of 89%, and circularity >0.95. The lenses have low aberrations and high throughput with a circular cross section. These lenses are ideal for use in applications such as optical data storage, fiber coupling, and any application in which degraded performance is due to an elliptical beam.

The development of dynamical surface of viscous liquid with electrical charge is researched in the periodical restoring process of spatial deformation type crater. The possibility of obtaining of optical elements on PTPC is indicated which combines the different physical properties as the diffraction (diffusion) and the refraction (focusing). The investigation of evolution kinetic of periodical deformed dissipative structures of crater type deformation indicates the existence of optimal time of 0.1 - 9.9 s as the dependence of recording regime, the destroying of optical refractive elements does not take place during it. The experimental calculations indicate that the developing speed of dynamical surface refractive element can give the values of 100 micrometers per second in the transversal plane and 0.2 from the thickness of the visualizing layer in the normal plane. A mechanism of germination and a mechanism of multiplying exists in the process of apparition and development of dissipative structures. This assures the nanofabrication of diffractive elements as optical non homogenous in the real time of development of refractive element. The diffractive element as the form of nonhomogenizes - deformation of crater type appears in the limit intervals from 0.04 to 0.1 s.

Multimode optical waveguides have been fabricated by dispensing photopolymers onto various substrates using direct-write technologies. Fine-tuning is achieved by micromachining the waveguides using a femtosecond-regime pulsed laser. Propagation losses are determined using the cutback method. A 2 × 2 coupler and a 1 × 8 splitter are demonstrated.

In this presentation we discuss a digital signal processing approach to optical component design and the fabrication of components in photopolymer layers and ion exchange waveguides. This technique is useful in designing complex filters such asapodized and cascaded gratings. We then illustrate the design process for a new type of Bragg filter formed in an edge illuminated holographic photopolymer. The filter can readily be apodized to reduce side lobes and cascaded to form various types of passband filters. In order to integrate filters of different types with optical fiber networks we describe a selectively buried ion exchange waveguide that provides efficient coupling between optical fibers and polymer materials deposited on the surface of the waveguide.

Novel methods for space-variant polarization-state manipulation using subwavelength metal and dielectric gratings are presented. By locally controlling the period and direction of the grating, we show that any desired polarization can be achieved. The methods presented in this paper are generic to any portion of the spectrum, and we present experimental demonstrations of our theory using CO₂ laser radiation at a wavelength of 10.6μm. Moreover, we exploited our computer-generated subwavelength gratings to demonstrate a polarization Talbot self-imaging, as well as nondiffracting periodically space-variant polarization beams, and a unique method for real-time polarization measurement. We also present novel optical phase elements based on the space-domain Pancharatnam-Berry phase. Unlike diffractive and refractive elements, the phase is not introduced through optical path differences, but results from the geometrical phase that accompanies space-variant polarization manipulation. We intoduce and experimentally demonstrate Pancharatnam-Berry phase optical elements (PBOEs) based on computer-generated subwavelength gratings such as polarization beam-splitters, optical switches and spiral phase.

A novel method called phase scanning is suggested in this paper, with which varied line-space diffraction grating can be fabricated on a classically photoelectric ruling engine. An experimentally blazed varied line-space plane grating with a central groove density of 1200 g/mm was fabricated. The space increment varies from -0.332nm to +0.332nm. A test to examine the scanning phase method was also made on it.

Using tightly focused femtosecond laser pulses waveguides can be fabricated inside various glasses. This technique has the potential to generate not only planar but three-dimensional photonic devices. In this paper we present, to the best of our knowledge, the first three-dimensional integrated optical device, a 1×3 splitter. The optical properties of this device will be discussed.

We describe novel designs for production of laser pulses from the nanosecond to the femtosecond regime which allow optimization to specific material processing requirements. These lasers are based on use of multimode Yb:fiber amplifiers (MM YDFA) to provide microJoule-level output in a single-mode beam. First, we present laser designs based on MM YDFA that produce 10 kHz - 5 MHz pulses of picosecond and femtosecond duration. Next, by seeding a MM YDFA with pre-shaped nanosecond laser diode seed pulses, we have created a laser that provides temporally nearly-rectangular output pulses. The duration is adjustable between 4 and 20 ns, with sharp rise times of <1.5 ns, and repetition rate of up to 20 kHz. Output pulse energy of >15 microJoules is maintained over the full tuning range. With this "tailorable" pulse design, control of laser energy deposition in confined laser interaction zones (“dosage”) can be user-optimized in real-time from the controller. For example, in biomedical microelectronics and other applications where the creation of micron-size features (in width and in depth) is required the user can adjust dosage in response to meas-ured structural changes over the material. Results of Si wafer and other material micromachining using this unique tem-porally-tailored pulsed laser are presented.

Binary Laser Direct-Write (LDW) raster-scan technology for UV exposure of photosensitive materials has been used for single or multiple-pass exposure applications. Gray-scale LDW can be applied to manufacture of 3-D optical structures, but the system requirements are substantially different, since edge slopes and surface departures must be controlled to within fractions of a wavelength.. In this paper, we explore the differences between binary and gray-scale raster imaging applied to micro-optic fabrication, and compare the system model with a prototype high-speed, gray-scale LDW tool that was developed from a Laser Direct Imaging tool originally designed for binary applications.

Excimer laser ablation is a versatile method to generate three dimensional microstructured devices for mechanics, fluidics and optics. Especially, if in one dimension the structure is predefined by a layer design, and the other two dimensions are defined in the layer ablation process by mask projection, very precise structure definition in three dimensions and ablated surfaces with optical quality can be achieved. Patterning optical layers or layer stacks, a variety of applications is possible. As examples the fabrication of dielectric masks and diffractive optical elements and the performance of these elements in shaping excimer laser beams are demonstrated.

With ultra-fast oscillator lasers (less than 1nJ/pulse, 80MHz repetition rate), we propose that we could fabricate features with less than 40nm inside UV transparent material such as fused silica and quartz. The low threshold property of this demonstration could lower the cost of lasers, and improve the throughput of laser machining due to the quasi-CW nature of the laser used. Our initial results shows that damages are observed with threshold as low as 1nJ before the UV objective, and then size is below 1 micron.

As CDs continue to shrink, lithographers are moving towards using off-axis illumination while continuing to decrease the operating wavelength to improve their CD budget. Currently DUV lithography at 248nm and 193nm are driving the ability of the foundries and IDM’s to meet or exceed the SIA roadmap for semiconductor chip performance. In time, however, the industry will migrate to the even shorter wavelengths of 157nm and 13nm. To meet today’s needs with 248nm and 193nm requires the use of Resolution Enhancement Techniques such as Optical Proximity Correction, Phase Shift Mask, and Off Axis Illumination. The need for these techniques will be only slightly reduced as the industry migrates to 157nm in several years. Off-axis illumination (the topic of this paper) has been shown to significantly increase the lithographic process window and there have been several papers over the last few years describing various illumination profiles designed for application specific optimization. These include various annular and quadrupole illumination schemes including weak quadrupole, CQUEST, and Quasar Diffractive optics, if incorporated into the design of the illumination system, can be used to create arbitrary illumination profiles without the associated light loss, thus maintaining throughput while optimizing system performance. We report on the design and fabrication of such devices for use with KrF, ArF, and F₂ scanners.

Fabrication processes for wet chemical and dry etching of hollow capillary leaky optical waveguides in high-purity fused silica for extended path cells for improved optical detection in analytical chemistry are described. We focus on microstructures with etch depths on the order of 80 μm. Special attention is paid to the preparation of the etch masks for the two different etch technologies. The fused silica wet chemical etching technique uses buffered hydrofluoric acid with ultrasonic agitation achieving etch rates > 100 nm/min. We succeeded in developing an etch process based on a single-layer photoresist (AZ 5214E, Clariant Corp.) soft mask, which gives excellent results due to special adhesion promotion and a photoresist hardening cycle after the developing step. This procedure allows for the production of channels of nearly semi-cylindrical profiles with etch depths of up to 87 μm. For the dry etch process a ~10 μm thick Ni layer is used as a hard mask realized with electroplating and a thick photoresist. The etch process is performed in an ECR (Electron Cyclotron Resonance) chamber using CF₄ gas. The resulting etch rate for fused silica is about 138 nm/min. Etch depths of (accidentally also) 87 μm are achieved.

Significant advancements in the field of controls engineering have recently been commercialized which have application to the fields of micromachining as well as for automated alignment, precision machining, tracking and active optics: 1. Cost effective, industrial-class implementations of Momentum Compensation (also known as Frahm Damping) provide low-order cancellation of inertial inputs to supporting structures and are of particular applicability to structures with low natural resonance frequencies; 2. Input Shaping, a patented digital controls algorithm developed at the Massachusetts Institute of Technology, provides effective cancellation of structural resonances in arbitrary actuation; 3. Input Preshaping, a technique realized in both a priori and self-learning implementations, substantially eliminates following errors in repetitive actuation. Simultaneous advancements in the minimization of multi-axis positioner workpiece mass via parallel kinematics technologies have increased the native bandwidth of the positioners used in these throughput-intensive applications. The author reviews applications of each of these, alone and together, in a comprehensive overview of the state of the art of high-bandwidth positioning techniques for micropatterning and micromachining.

Moulding of plastics enables optical features to be integrated into a single unit. This is particularly an advantage for product designs that impose space and weight constraints. Therefore, the use of plastic for biomedical and non telecommunications orientated optical applications continues to grow as design engineers take advantage of the ease of fabrication and the material flexibility. Deep X-ray LIGA presents itself as a method ideally suited for the production of moulds for the manufacture of plastic microcomponents. LIGA is synonymous for the lithography preferably carried out with synchrotron radiation X-rays, although many other lithography and non-lithography methods for master production have been developed in the last few years. Nevertheless, the exceptional resist heights, the enormous accuracy and low runout as well as the low sidewall roughnesses cannot be copied by these other methods of master production. In particular, the low sidewall roughnesses achieved through deep X-ray LIGA is essential for the manufacture of waveguide coupling systems based on polymers. The design and conceptualisation of such waveguides systems is presented here. In addition however, the exceptional resist heights and low runout can be employed to produce passive structures for the packaging of optical components. This paper provides an overview of the deep X-ray LIGA technology, emphasizing its strengths and application areas. Considerations for the design and manufacture of the plastic structures are also elucidated.

A new method, self-alignment process is introduced to fabricate microlens arrays. By this method, during fabrication process, the rigorous alignment, which has great effect on diffraction efficiency in the conventional multi-photolithography process, is avoided. The large arrays of 1500 × 640 element silica microlens with 8-phase-level are manufactured by this method. The measurement results show that the 8-phase-level microlens arrays diffraction efficiency is as high as 93%, which is higher than by the conventional method.