Most Silicon based depth and lidar sensors rely on near-infrared (NIR 750-900nm) sources to produce depth images as Silicon CMOS sensors can achieve a high quantum efficiency for an unbeatable cost at such wavelengths. Advances in Short Wave Infrared (SWIR) sensor technologies, such as Silicon-Germanium sensors, changes this paradigm and opens a new window for groundbreaking sensor designs, as SWIR can push the wavelength above retinal hazard area (⪆1400nm), allowing for much higher eye safety, due to the low penetration of those wavelengths through the eye lens. Here, we propose to use a Silicon Metalens flat optics and build upon our stacked sensor technologies to obtain a fully Silicon integrated stacked sensor at SWIR wavelengths. We will discuss the design of the stacked sensor and focus on the Silicon Metalens for multiple use-cases. We will demonstrate the results of our Silicon metalens prototype at 1550nm. We will show numerical simulations of the optical stack for eye-tracking application or wide-angle Time of Flight (TOF) and discuss the necessary trade-offs.
We introduce our cutting-edge panoramic camera – a True Panoramic Camera (TPC), designed for mobile smartphone applications. Leveraging prism optics and well-known imaging processing algorithms, our camera achieves parallax-free seamless stitching of images captured by dual cameras pointing in two different directions opposite to the normal. The result is an ultra-wide (140ox53o) panoramic Field-of-View (FOV) without the optical distortions typically associated with ultra-wide-angle lenses. Packed into a compact camera module measuring 22 mm (length) x 11 mm (width) x 9 mm (height) and integrated into a mobile testing platform featuring the Snapdragon 8 Gen 1 processor, the TPC demonstrates unprecedented capabilities of capturing panoramic pictures in a single shot and recording panoramic videos.
Recent investigations in holographic mass memory systems have produced proof of concept demonstrations that have highlighted their potential for providing unprecedented capacity, data transfer rates and fast random access performance. The exploratory nature of most such investigations have been largely confined to benchtop experiments in which the practical constraints of packaging and environmental concerns have been ignored. We have embarked on an effort to demonstrate the holographic mass memory concept by developing a compact prototype system geared for avionics and similar applications which demand the following features (mostly interdependent factors): (1) solid state design (no moving parts), (2) fast data seek time, (3) robust with respect to environmental factors (temperature, vibration, shock). In this paper, we report on the development and demonstration of two systems, one with 100 Mbytes and the other with more than 1 Gbyte of storage capacity. Both systems feature solid state design with the addressing mechanism realized with acousto- optic deflectors that are capable of better than 50 microseconds data seek time. Since the basic designs for the two systems are similar, we describe only the larger system in detail. The operation of the smaller system has been demonstrated in various environments including hand-held operation and thermal/mechanical shock and a photograph of the smaller system is provided as well as actual digital data retrieved from the same system.
In this paper, an in real time and in situ fixing method by heating with a carbon-dioxide laser beam is suggested to thermally fix a small local hologram in a bulk of Fe:LiNbO3 photorefractive crystal. To form a heating-up to 100 - 200 degree Celsius volume with the shape similar to the laser beam, heat-guiding technique is developed. Based on the heat transfer equations, different heating modes with or without metal absorbers for heat-guiding by using a continuous or pulsed laser beam are analyzed. The optimal mode may be the case of pulsed heating with absorbers. On this basis, experiments are designed and demonstrated. It is seen that the fixing process by carbon-dioxide laser beam is very short compared with the process by oven and the fixing efficiency is quite high.
In order for optical interconnects to become a mature technology they must be amenable to electronic packaging technology. Two main obstacles to including free-space optical interconnects are alignment and heat dissipation issues. This paper presents work that studies the issues of alignment tolerancing over long distance (greater than 10 cm) board-level interconnects. In this work we demonstrate a computer-aided analysis procedure that permits one to determine the alignment tolerances needed to achieve some system level specification, such as yield or cost. The procedure that we employ relies upon developing a detailed design of the system to be studied in a standard optical design program such as CODE V. Using information from this model, we can determine the integrated power falling on the detector by performing Gaussian propagation and/or general Fresnel propagation (if significant vignetting occurs). With this computer-aided analysis technique, a sensitivity analysis of all the misalignments under study is made on a realistic system to find each misalignment's relative effects (with other misalignments being set to zero) on the power falling on the detector. This information is used to set initial tolerances for subsequent tolerancing analysis and design runs. An alignment tolerancing analysis using Monte Carlo techniques is applied to determine if the yield/cost (yield being defined as the percentage of systems that have acceptable system performance) is acceptable. By utilizing a technique called parametric sampling, a subsequent tolerancing design run can be applied to optimize this yield/cost with very little increase in computation. In this paper, we study a realistic design example and show that all tolerances can be achieved with current technology.
This paper presents the concepts of a board-to-board free space optical interconnection scheme that will support a bus architecture. While the technology required to implement this optical scheme is very compatible with existing electronic packaging technologies, it promises to be able interconnect many more boards together without serious impedance matching or termination problems encountered by electrical interconnects at high speed. Experimental demonstration of the optical scheme is in progress.
Lead Lanthanum Zirconate Titanate (PLZT--a transparent, ferroelectric ceramic) exhibits a large quadratic electro-optic effect, allows full modulation at relatively low voltages and is commercially available in wafer form up to 150 mm diameter. PLZT modulators can handle large amount of light power. They can be configured for either reflective or transmissive operation and the pixel switching speed is in the order of 500 ns. High contrast ratio (4000:1) and throughput (90%) can be accommodated. A new technique referred to as direct bonding that involves the bonding of a thin Si film containing circuits onto PLZT substrates allows a monolithic-like integration without affecting the performance of modulators or electronic circuits. Lenslet arrays and Wollaston prisms can be added to the input of the modulator array to improve the light throughput for unpolarized light. An electro-optic light deflector stage added to the output will improve the space-bandwidth product by trading off the speed of the PLZT modulator. The availability of an excellent modulator and the possibility for monolithic integration with Si circuits makes Si/PLZT technology attractive for high performance display applications.
Architectures of optoelectronic neural network modules based on digital 3-D holographic memory are evaluated in terms of holographic memory design, module scalability and learning capability. A feed-forward module with 900 inputs and 9 outputs with 12-bit interconnection accuracy and perceptron learning are demonstrated experimentally.
Multistage interconnection networks (MINs) are used to create wide diameter networks with a logarithmic number of stages. To further reduce the costs of constructing and operating this type of network, these stages can be stored in a volume hologram and accessed sequentially to achieve the same functionality as a MIN. We discuss the design of such a system and demonstrate a prototype that uses infrared sensitive photorefractive lithium niobate to store a wavelength multiplexed volume holographic lens array. The holograms were recorded at 800 nm and several stages were multiplexed in a single hologram, each separated by as little as 0.6 nm. The optical system performance was analyzed and the results discussed.
In order to fabricate practical free-space optical interconnect systems, a thorough understanding of the effect of optical misalignment on the power throughput of an optical link is required. Further, not only assembly tolerances (resulting in misalignment) but also component manufacturing tolerances that also introduce vignetting into the optical system need to be studied. We present a study of a wide variety of assembly and component manufacturing errors and their effect on the integrated power falling onto the detector for planar space variant optical systems. We also discuss the trends of the different misalignment sensitivities as the interconnect distance increases.
The impact of process variation associated with lateral and axial misalignment of flip-chip solder joint based assembly for OE-MCM packaging is analyzed through quasi-static force balance in the system. The effect of variation in solder deposition height, vertical loading, and surface tension coefficient on the alignment, and therefore on the optical performance of the system, is studied.
The addition of optics to electronics in optoelectronic packaging for free-space optical interconnects alters the nature of electrical packaging design methodologies as well as the complexity of implementation. One such complexity arises from the stringent alignment requirement among the microlaser, computer-generated holographic element, and detector. The alignment achieved in the system is a function of assembly tolerance and working environment conditions such as operating temperature. The impact of these constraints on the alignability of the assembly of free-space optical interconnects is quantitatively analyzed.
Photorefractive materials are useful for optical interconnection and data storage in optoelectronic computing systems because of their unique properties (e.g., writelreadlerase capability, real time wave mixing, and high storage capacity). In this paper we will review the recent advances in these two application areas that make use of these properties and the techniques for improving their real-time and storage performance.
The packaging opto-electronic interconnects has the potential to create compact, highly dense communication networks. We present a packaged space-variant optical interconnect module using wavelength multiplexed volume holographic elements recorded in photorefractive materials. The input/output arrays (4 X 4), an illumination lenslet array, and a set of two wavelength multiplexed off-axis volume holographic lenslet arrays were integrated with a series of several glass substrates to form a free-space optical interconnect. The size of the packaged optical interconnect module was 40 mm X 24 mm X 37 mm. Reconfigurable interconnection was demonstrated on the packaged module by performing the perfect shuffle and butterfly networks, at different wavelengths. Several packaging issues, such as alignment, bonding, energy efficiency, and system scalability were studied.
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