We present a broadband and polarization-insensitive unidirectional imager that operates at the visible part of the spectrum, where image formation occurs in one direction, while in the opposite direction, it is blocked. This approach is enabled by deep learning-driven diffractive optical design with wafer-scale nano-fabrication using high-purity fused silica to ensure optical transparency and thermal stability. Our design achieves unidirectional imaging across three visible wavelengths (covering red, green, and blue parts of the spectrum), and we experimentally validated this broadband unidirectional imager by creating high-fidelity images in the forward direction and generating weak, distorted output patterns in the backward direction, in alignment with our numerical simulations. This work demonstrates wafer-scale production of diffractive optical processors, featuring 16 levels of nanoscale phase features distributed across two axially aligned diffractive layers for visible unidirectional imaging. This approach facilitates mass-scale production of ~0.5 billion nanoscale phase features per wafer, supporting high-throughput manufacturing of hundreds to thousands of multi-layer diffractive processors suitable for large apertures and parallel processing of multiple tasks. Beyond broadband unidirectional imaging in the visible spectrum, this study establishes a pathway for artificial-intelligence-enabled diffractive optics with versatile applications, signaling a new era in optical device functionality with industrial-level, massively scalable fabrication.

As autonomous vehicles rapidly transition to fully automated operations, the ability of these systems to make critical safety decisions in real-time remains of paramount concern. Successful implementation will rely on maintaining the highest possible fidelity of the underlying image data while operating in the challenging automotive light detection and ranging (LIDAR) environment. In addition to three dimensional (3D) depth data, some proposed systems seek to overlay data from multiple sources in order to further improve decision quality and safety margin. The requirement to establish and maintain system calibration over life, including overlay of various fields of view suggests the need for an optical reference that could be used to routinely recalibrate the system in the field. The ability to validate and re-calibrate LIDAR systems in the field without the need for operator intervention would also serve to ensure consistent data quality as well as removing the need to take vehicles offline for periodic re-calibration. Diffractive-Optical-Elements (DOEs) are well suited for use as optical calibration references. In addition to their small size and lithographic precision, fused silica DOEs exhibit extreme stability and mechanical strength, potentially allowing for direct integration into the LIDAR system itself. In this paper, we examine the use of DOEs as LIDAR calibration standards, including the impact of material properties on the stability of the generated reference patterns and consequently on the reliability of the imaging system data.

Abstract. The promise of fully autonomous vehicles to replace the judgment of human drivers with real-time algorithmic decision-making based on optoelectronic systems relies fundamentally on the quality of the available data. Limitations imposed by sensor-resolution, available optical power, and achievable signal-to-noise ratios have been well studied in the light detection and ranging (LIDAR) application space. Additionally, the problem of integrating multiple sources of image data as well as the need to establish and maintain the system calibration over life are critically important to system reliability and safety. These latter concerns will receive even greater attention as self-driving vehicles begin to transition toward fully autonomous operation. Because of the importance of calibration to system performance and safety, the process of validating and recalibrating the system will ideally be integrated into the LIDAR system itself with calibration occurring automatically “anywhere and at any time,” without dedicated external infrastructure. Mass-market adoption is also being driven by the systems’ size and weight, as well as reliable manufacturability and resilience to environmental stresses. Due to their extreme stability, manufacturability, and small size, diffractive optical elements (DOEs) are well suited for use as optical calibration references. Current three-dimensional (3D) mapping systems based on structured light illumination already rely on DOEs as precision pattern generators to provide 3D depth sensing in a wide array mobile devices. We examine the potential use of DOEs as calibration elements in multicamera or LIDAR systems, including appropriate choices of materials, designs, and fabrication methods to ensure reliable long-term performance under automotive use conditions. We present simulations of the impact of DOE material properties on the accuracy of the generated dot patterns and consequently on the depth accuracy and lateral distortion of the 3D image. Additionally, we present requirements for DOE manufacture using conventional semiconductor fabrication technologies optimized for creating engineered surface nanostructures capable of transforming the output of a laser or other narrow-band source into a precise reference pattern.

The introduction of source mask optimization (SMO) to the design process addresses an urgent need for the 32nm node and beyond as alternative lithography approaches continue to push out. To take full advantage of SMO routines, an understanding of the characteristic properties of diffractive optical elements (DOEs) is required. Greater flexibility in the DOE output is needed to optimize lithographic process windows. In addition, new and tighter constraints on the DOEs used for off-axis illumination (OAI) are being introduced to precisely predict, control and reduce the effects of pole imbalance and stray light on the CD budget. We present recent advancements in the modeling and optical performance of these DOEs.

We present a method for optimizing a free-form illuminator implemented using a diffractive optical element (DOE). The method, which co-optimizes the source and mask taking entire images of circuit clips into account, improves the common process-window and 2-D image fidelity. We compare process-windows for optimized standard and free-form DOE illuminations for arrays and random placements of contact holes at the 45 nm and 32 nm nodes. Source-mask cooptimization leads to a better-performing source compared to source-only optimization. We quantify the effect of typical DOE manufacturing defects on lithography performance in terms of NILS and common process-window.

We present advancements in the manufacture of high-performance diffractive optical elements (DOEs) used in stepper/scanner off-axis illumination systems. These advancements have been made by employing high resolution lithographic techniques, in combination with precision glass-etching capabilities. Enhanced performance of DOE designs is demonstrated, including higher efficiency with improved uniformity for multi-pole illumination at the pupil plane, while maintaining low on-axis intensity. Theoretical predictions of the performance for several classes of DOE designs will be presented and compared with experimental results. This new process capability results in improved performance of current DOE designs, and enables greater customization including control of the output spatial intensity distribution for future designs. These advancements will facilitate continuous improvements in off-axis illumination optimization required by the end user to obtain larger effective lithographic process windows.

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 193mn 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(TM). 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 F-2 scanners.

Fabrication of micro optics for fiber optics applications is a challenge due to their size and the issues associated with alignment of the optics to single-mode fibers. This study summarizes a method for fabricating diffractive optical elements on the ends of coreless fiber segments for passive alignment to single-mode fibers. Results are presented for passively aligned diffractive lens elements used for both collimation and beam shaping.

This paper reports a novel launch scheme for coupling light into the skew rays of a graded index fiber. This is accomplished by utilizing a diffractive optical element in conjunction with a single mode fiber to mode match a graded index fiber. Results are used to confirm the fact that the element does improve the coupling into the skew rays of graded index fiber. This approach offers an alternative to existing methods based on tilting and angular offsets for the conditioned launch problem.

An alternative method is presented for launching light into graded index fiber. This approach utilizes a diffractive element to match the phase of the launched light into specific modes of the graded index fiber.

Graded index fiber has a limited bandwidth due to defects introduced in the fiber manufacturing process. In this paper, an alternative launch technique is presented using a diffractive element to excite specific modes in a fiber to maximize the bandwidth of graded index fiber.

Standard laser welding practices are limited by the intensity profile of the beam and spot size. The introduction of Diffractive Optical Elements (DOE) to the welding process allows for new beam shapes that are better suited to the welding process. A particular problem in laser welding is the joining of dissimilar materials. Because these materials have different material properties including different melting temperatures, it is difficult to synchronize the welding process using a single spot. Additionally, significant thermal stresses are introduced by the welding process because of the keyhole weld shape formed by a gaussian beam. By using a power splitting DOE, two spots of unequal intensity distributions may be projected onto each side of the weld joint. This paper discusses the use of DOEs in laser welding and joining of dissimilar materials. Results are presented from the testing of several candidate aerospace materials.

Previously, a method of incorporating a microlens within a standard fiber optic ferrule was described. In this paper, the micro-rod and wafer fabrication concepts are explained, the wafer mapping/layout processes used to create the microlens substrate are detailed, and packaging in standard ferrules and v-grooves are described along with coupling results.

Integrated Micro-Optical Systems (IMOS) are integrated assemblies of multiple optical components that are made and assembled at the wafer level using semiconductor processing techniques. IMOS has been used to create 3 dimensional optical systems in a cost-effective, highly manufacturable manner. Collimated lens arrays have been fabricated with experimental total round trip insertion loss of 1.5-2.0 dB per channel.

Silicon v-groove structures have been utilized for passive positioning of optical fiber for fiber optic and opto- electronic applications. In this paper, we will present our results of using micro-machined silicon v-groove arrays to passively align optical fiber arrays to micro rod optics. We will also demonstrate the integration of N fiber arrays bonded into the silicon v-groove with a 1xN micro lens array, which is composed of a 2 inch-phase level diffractive optics. For the assembly of 1x6 fiber array and lens array with 16 phase level diffractive optics, the experimental results indicated that total insertion loss per link is typically 1.5-2.0 dB/channel.

Optical connectors utilize microlens elements for coupling light into and out of fibers. Typically, these lenses are based on sapphire ball lenses or Gradient Index lens elements.However, lenses that are on the same scale as the single-mode fiber itself have not been previously realized. This paper introduces an optical lens element that fits into the single-mode optical ferrule, without any modifications to the connector package. This approach offers substantial performance and cost benefits over other methods.Both theoretical and experimental results are presented.

This paper describes the technical approach and progresses of the POINT (Polymer Optical Interconnect Technology) program. This project is a collaborative effort among GE, Honeywell, AMP, AlliedSignal, Columbia University and University of California at San Diego (UCSD), sponsored by DARPA/ETO to develop affordable optoelectronic packaging and interconnect technologies for board and backplane applications. In this paper, we describe the recent development under this program in the following areas: (a) a high density optical interconnect for board and backplane applications using polymer waveguides (Polyguide) to demonstrate high I/O density (100 /spl mu/m channel spacing) and high speed (/spl sim/1 Gbps) interconnect with an interconnect distance to 280 mm, (b) a high density and high speed VCSEL array packaging technology that employs planar and batch fabrication processes scaleable to large volume, low-cost manufacturing, (c) passive alignment techniques for reducing the recurrent cost in an optoelectronic assembly, (d) low-loss optical polymers for board and backplane level interconnects, and (e) CAD tools for modeling multimode guided wave systems and assisting optoelectronic packaging mechanical design.