Manufacturing processes have been developed to produce wafer scale optics in chalcogenide glass using semiconductor
fabrication. Chalcogenide materials are amorphous and covalently bonded solids containing one or more of elements in
Group VI in the periodic table, e.g. sulphur, selenium, or tellurium as a substantial constituent. For this paper, the
material selected for testing to determine the etching process was IG6 - As40Se60. Grayscale photolithography and
binary methods were used to pattern diffractive elements for use in infrared applications. Dual-band color correction,
incorporating diffractive optics, will be presented in the paper as an application of this development.
Standard UV materials, such as ArF-grade fused silica, have impurities that lead to low transmittance, high absorption,
and fluorescence when exposed to high irradiance. Calcium fluoride (CaF2), on the other hand, is a promising material
for use as an optical diffuser for applications at 157nm, 193nm, and 248nm due to its low defect density and high
transmission in the deep UV regime. In this paper, we discuss our method for fabricating Gaussian homogenizers in
calcium fluoride using a grayscale photolithography process. Refractive microlens array homogenizers and Gaussian
homogenizers have been fabricated in CaF2 and tested at 193nm for efficiency and uniformity. Using an excimer laser,
uniformity results were obtained for cylindrical lens arrays in tandem and crossed to observe the homogeneity in an
imaging configuration and for producing a square output. Efficiency, uniformity, and zero order measurements are
provided for the Gaussian homogenizers.
Many manufacturing techniques have been developed and implemented to fabricate a wide range of micro-optical
products. The challenges of the micro-optics business are diverse and tend to resist a widely accepted manufacturing process such as has been implemented for CMOS fabrication. Many of the challenges that have been addressed with various solutions include optical waveband of operation from DUV through LWIR, material systems, cost of manufacturing for the intended application space, feature sizes based on device functionality, and fabrication technology based on the manufacturing volume. Some of the technologies to be discussed include device patterning by e-beam lithography, optical lithography, direct CNC machining and micro-polishing, and plastic replication.
A process to diffractively structure GaAs for enhanced optical performance is described. The benefits of diffractively structuring an EOIR window material include improved FOR/FOV, consistent broadband performance, the ability to design and implement hyper-spectral characteristics directly into the substrate without incorporating a complex anti-reflective coating. Progress to date will be discussed including design evolution, process implementation, and optical characterization using the Automated Rasterable Integrated Spectrometer and TIS Measurement System (ARISTMS). Results will be presented on 100mm diameter samples.
Modern optoelectronic devices require micro and nano-structures to be etched into a wide range of substrate materials. The ability to plasma etch a wide range of semiconductor and glass materials is required to produce devices that provide technical solutions to challenging optical designs for optoelectronic applications. This paper addresses the etching practices developed primarily for microoptical devices including lenses and gratings. The materials considered are compound semiconductors in the III-V materials group as well as high index of refraction optical glasses. Many of the materials investigated were evaluated for optical data storage applications for future generation devices.
Manufacturing processes have been developed to produce high performance wafer form microoptics in both bulk zinc selenide and bulk multispectral zinc sulfide. Gray scale photolithography techniques have been used to pattern aspheric refractive lenses and beam shaping diffractive structures in wafer form for both of the zinc based II-VI group materials. High density plasma etching recipes have been refined to etch gray scale photoresist patterns into the bulk II-VI wafer materials with controllable selectivity. These IR materials have the advantage over other IR materials of transmitting broadband radiation, including visible band radiation. This very wide transmission band capability (visible to LWIR) permits dual band applications to use the same optical path. The high index of refraction of these materials permits production of higher numerical aperture lenses that have reduced lens sag requirements.
The design, fabrication, and testing of a new anamorphic microlens for laser diode circularization is presented. The microlens is fabricated using photolithography, gray scale masks, and reactive ion etching. A front-to-back mask aligner is used to precisely align two anamorphic aspheric microlenses on opposite sides of a single wafer, creating the ability to circularize or collimate a laser diode with only a single monolithic element. The entire fabrication process is highly nonlinear. This requires that accurate surface metrology methods be incorporated into the process as a feedback loop for iterative corrections to the gray scale mask. We discuss the measurement process and the effects of surface errors for circularizers and circularizer/collimators. This device has been under development for about two years at MEMS Optical. The most recent fabrication and test results of an actual device are presented.
For many applications such as lithography and material processing it is important to generate a specific laser irradiance profile. In this paper we discuss design, fabrication, and testing considerations for three beam shapers. These beam shapers transform a 632.8 nm Gaussian intensity profile beam into a square, circle, and ring flat top irradiance profiles. The designs were tailored to minimize the usual sensitivity to fabrication errors. Simulation and empirical results are presented showing very good uniformity in the flat top beams. Other possible beam shapes are presented as well as design performance improvements with analog profile diffractive surface relief structures made with gray scale masks. The issues and difficulties of designing and fabricating UV beam shapers are also discussed.
An adaptive optics system is being developed, which uses integrated circuit technology along with diffractive optics to crete a very compact system. A lenslet array focuses incoming light onto individual actuators. Phase modulation is applied with electrostatic attraction. Gratings on the mirrors split off a part of the light for wavefront sampling. Optics on the back side of the lenslet array combine neighboring beams and focus onto detector elements. This creates a shearing measurement in two orthogonal directions. A resistive grid network reconstructs the wavefront from the individual measurements, and a feedback system nulls the outgoing wave. This paper contains simulations and analysis of the system. A 1D array was simulated, including the wavefront measurement and correction. A sine wave was input to the system, and the resulting phase and point spread function were calculated. System analysis of the wavefront reconstruction and feedback are discussed. Test results for a non-shearing interferometer are presented. Some test results from a test chip are also provided.
Current AMLCD panel pixels are divided into sub-pixels each covered by red, green, or blue absorptive color filters to transmit each of the color components. This method discards 2/3 of available light and causes these displays to be highly inefficient. Using a diffractive color separation filter, DCSF, a much higher percentage of energy from the back-light is used in the display, which can be translated into higher brightness and lower power consumption. Such a DCSF is designed to separate the colors and focus the desired bands onto the apertures of the color pixels. The black matrix is used to block the undesired wavebands. Two basic prototype models were designed and fabricated. The first filter design constraints focusing elements and the second filter contains no focusing elements. This paper present testing results from the two prototype diffractive color separation filter designs.