Michael Evans, Sungjin Kim, John Liobe, Paul Bereznycky, Dmitry Zhilinsky, Wei Xu, John Wieners, Andrew Eckhardt, Jinguo Yu, Michael Delamere, John Tagle, Scott Ramsey
As customer demand for infrared laser sensors increases, so too does the need for low cost, readily manufacturable SWIR imaging systems capable of asynchronous laser pulse detection (ALPD). Sensors Unlimited, Inc., an RTX company, presents recent advancements in its SWIR APLD products tailored toward high volume production and broad deployment. Detectors based on SUI’s multi-mode tracking (MMT) readout integrated circuit (ROIC) have been adapted for uncooled operation over a wide temperature range, enabling the elimination of costly thermoelectric cooling. A chip-on-board device configuration has also been implemented, obviating the need for a windowed package. Automation of fabrication processes further reduces unit cost and provides improved device uniformity. Results of SUI’s latest system performance assessments are also discussed.
Sensors Unlimited Inc. (SUI), a Raytheon Company, continues to expand its sensor portfolio through the development of time-of-flight (TOF) capable technologies. The utility of SWIR for active TOF solutions is of particular interest due to its inherent eye safety characteristic. SUI is developing TOF technologies both at the detector and readout integrated circuit (ROIC) layers of the focal plane array (FPA). In this work, SUI will offer updates to the internal development efforts comprising both areas as it pertains to the time-of-flight technologies.
In this work, SUI presents an update on PIN Photodiode Array (PDA) developments and the advancements in Avalanche Photodetectors (APD) Array development. SUI continue to push the PIN based SWIR photodetector performance by reducing the dark current, increasing the quantum efficiency in broad spectral wavelength range from 400nm to 1700nm and extending the wavelength to 2.6μm. We will also present APD technology advancements specifically related to low temperature performance from room temperature to 260K and Geiger Mode operation. In addition, we will discuss the requirements of Readout Integrated Circuits (ROIC) for APD based sensor development for synchronous and asynchronous pulse detection and active and passive quenching mechanisms. We will also discuss 2-D and 3-D TCAD simulation results at low temperature and compare them with measured performance results. Finally, recent results related to the advanced development of Geiger Mode Avalanche Photodetectors (GMAPD) and the results using passive and active quenching circuits are presented.
The value proposition for Short-Wave Infrared (SWIR) includes capabilities beyond standard passive, low-noise imaging. Sensors Unlimited Inc. (SUI), a Raytheon Technologies Company, has expanded its multi-mode tracking (MMT) portfolio with the development of two new solutions, each of which offers laser range finding (LRF) capability. The SWIR Pocket Scope-MMT (SPS-MMT) sets the gold standard for asynchronous laser pulse detection (ALPD) and low-noise passive imaging, internally dubbed MMT, in a SWIR hand-held solution. SUI’s expanded portfolio now includes a variant of that product with an embedded LRF so that the warfighter can simultaneously, image, track and decode any laser designators, and determine the distance to any targets in the same scene of interest. Additionally, SUI has developed an HD version of that capability set. Performance results of each solution will be described herein.
Improved situational awareness using SWIR is of upmost importance to many of SUI's, a Collins Aerospace company, customers. SUI’s proprietary Asynchronous Laser Pulse Detection (aka MMT, Multi-Mode Tracking) methodology facilitates the detection, tracking, and decode of NIR-SWIR lasers at the pixel level at all ambient lighting conditions without the compromising imaging performance. This paper describes advancing this technology for improved hostile detection. The main challenge of hostile detection using infrared imaging technologies is the requirement for fast frame rates as the signal lifetime is short for both retroreflection and muzzle flash detection. In this work, SUI demonstrates how its MMT technology can be leveraged for low SWaP hostile detection applications.
Recent short-wave infrared (SWIR) sensors have demonstrated in-pixel multimode capabilities. One of the additional modes is range finding. High resolution range finding is increasingly becoming vital functionality in high precision targeting and imaging systems. Highly precise and accurate range-to-target information is essential for many modern commercial and military applications. With the recent advances in LiDAR (Light Detection and Ranging) technology, range measurement accuracies as low as a centimeter at kilometer ranges. Sensors Unlimited Inc. (SUI), a Raytheon Technologies (RTX) Company, has been developing these multimode sensors using traditional PIN-based InGaAs detector technology. However, the capability of these sensors has been extended through the introduction of Avalanche Photodetector (APD) InGaAs sensors. This APD technology has been developed onshore to better serve the onshore community requiring simultaneous laser tracking, ranging, and imaging applications. In this work, SUI offers an update on previously presented, PDA-specific development, most specifically related to the advancement of Geiger Mode Avalanche Photodetectors (GMAPD). SUI’s APD technology is in direct response to the challenging SWaP and NEI performance requirements of active imaging and tracking applications. This update includes 2D and 3D TCAD simulation results with a comparison with measured performance results. Finally, initial results related to the advanced development of Geiger Mode Avalanche Photodetectors (GMAPD) themselves as well as supporting electronics is given. The revitalization of SUI’s APD development is a direct response to the challenging SWaP and longer-range with higher accuracy performance requirements of active imaging applications. SUI’s most recent APD design improvements facilitates greater signal to noise ratio at the pixel, which subsequently enables a supporting ROIC pixel design with improved performance.
This paper reviews the camera development efforts at Sensors Unlimited Inc. (SUI), a Collins Aerospace company, focused on serving multi-mode short-wavelength infrared (SWIR) applications while maintaining a low size, weight, and power (SWaP) footprint. Increasingly over the last decade, end users have looked to SWIR to support not only low-noise passive imaging, but also active illumination applications. Hence, cameras that include provisions to specifically support both modalities, passive and active imaging, have been given the moniker, “Multi-Mode.” In this work, SUI offers an overview of the passive and active imaging performance of the multi-mode cameras in its technology portfolio juxtaposing the traits of each. Finally, an outlook for future work in the area of multi-mode SWIR camera development is presented.
KEYWORDS: Aerospace engineering, Photodetectors, Diffusion, Modulation transfer functions, Avalanche photodetectors, Readout integrated circuits, Personal digital assistants, Metals, Short wave infrared radiation, Scanning electron microscopy
Increasing shortwave infrared (SWIR) sensor performance requirements have pushed traditional HOT detector technologies to their limits. Collins Aerospace Princeton, a Raytheon Technologies (RTX) Company, has answered this call by looking beyond dark current reduction, and leveraging its onshore foundry capabilities to develop unprecedented, high performance photodetector array (PDA) technologies to better serve both passive and active imaging applications. In this work, Collins Aerospace Princeton offers an update on several previously presented, PDA-specific development fronts as well as offering introductions into other novel efforts. In addition to presenting current state-ofthe-art (SOA) InGaAs dark current performance, results related to mesa-structure PDAs for modulation transfer function (MTF) improvement and hybridization capacitance reduction for active imaging noise equivalent irradiance (NEI) improvement are offered. Additionally, focal plane array (FPA) interconnection improvement techniques and results for yield improvement and cost reduction are presented. Finally, results related to the three most advanced and nascent development tracks, avalanche photodiode (APD), PDA metallization and single side bumped FPA, are introduced. Collins Aerospace Princeton’s APD technology is in direct response to the challenging size, weight, and power (SWaP) and NEI performance requirements of active imaging applications. Similarly, Collins Aerospace Princeton’s PDA metallization technology, inspired by silicon-based brethren, facilitates greater integration capability on the PDA itself, which subsequently allows for greater functionality and performance at every pixel location. The most recently developed single side bumped FPA will dramatically improve operability with reduced cost. Overall, these PDA-specific developments represent the most innovative SWIR technology portfolio known to date.
KEYWORDS: Sensors, Short wave infrared radiation, Personal digital assistants, Photodiodes, Modulation transfer functions, Sensor technology, Detector arrays, Capacitance
Sensors Unlimited Inc. (SUI), a Raytheon Technologies Company, has long been the vanguard of low-noise InGaAs/InP PiN back-side illuminated (BSI) planar-type photodiode technology. In addition to focusing on dark current reduction efforts, SUI has also initiated other photodiode detector array (PDA) improvement efforts to better serve its broad portfolio of sensor technology. In previous years, SUI has presented results related to mesa-structure PDAs for modulation transfer function (MTF) improvement and hybridization capacitance reduction for NEI improvement. An update to these technologies is offered. Additionally, SUI has more recently engaged in more advanced PDA development to better satisfy active imaging applications. Results of these efforts are also presented.
Sensors Unlimited Inc. (SUI), a Collins Aerospace Company, has developed a large-area, high-speed, short-wave infrared (SWIR) focal plane array (FPA) to meet the field-of-view (FOV) and bandwidth requirements of LiDAR applications. Modifications to SUI’s standard InGaAs photodiode array (PDA), include junction shape, dielectric thickness, and contact metallization. These changes allow for a reduction in the effective capacitance seen by the hybridized FPA’s readout integrated circuit (ROIC) while preserving the epitaxial structure that ensures the company’s industry-leading dark current. Compared to SUI’s standard device, significant capacitance reductions have been demonstrated. Enhancements of laser pulse detection performance arising from the capacitance improvement, and suitability of the resulting device for implementation in LiDAR systems, will be discussed.
Next-generation multi-mode tracking (MMT) technology developed by Sensors Unlimited Inc. (SUI), a Collins Aerospace Company, is presented. The technology provides focal plane arays (FPAs) with pulse detection capability in addition to traditional passive imaging, enabling more compact electro-optical (EO) systems with significantly lower power consumption. SUI’s latest MMT device is a short wave infrared (SWIR) FPA that features low-noise imaging, asynchronous laser pulse detection (ALPD), and time-of-arrival (TOA) capability in every pixel in the 12 μm pitch, 1280 x 1024 array. Simulated and measured results from the new FPA’s readout integrated circuit (ROIC), the 1280MMT, are given along with a comparison to SUI’s first multi-mode tracking ROIC, the 640MMT.
Sensors Unlimited Inc. (SUI), a Collins Aerospace company, has developed a short wave infrared (SWIR) photodetector device structure using isolated mesa pixels to improve the detector modulation transfer function (MTF), an important parameter in determining the overall image quality of a camera system. A combination of device fabrication and simulation has been used to evaluate the design and manufacturability of various mesa morphologies. Because mesa formation entails both the removal of some portion of the active region of the photodetector and the introduction of non- planar surfaces, any MTF improvement must be balanced against a loss of quantum efficiency (QE) and potentially higher dark current. Focal plane arrays (FPAs) based on the optimal mesa morphology have been fabricated and compared for MTF and QE performance at the camera level to FPAs built using SUI’s standard pixel structure. The mesa structure described herein is implemented on the front side of the photodetector and could also be implemented across all of SUI’s backside-illuminated (i.e., VIS/SWIR, NIR/SWIR, SWIR) structures for applications where a premium is placed on MTF performance.
For ultra-fine pixel pitch focal plane array (FPA) applications, flip-chip hybridization has advantages including high I/O density and short distance between the photodiode array (PDA) and the readout integrated circuit (ROIC). Indium has become the primary interconnect material because of its high ductility at low temperature. Successful mating of large format die becomes increasingly difficult, however, for finer pitch applications where bumps are shorter, as tolerance for bowing is low. Simultaneously, the epoxy filling process for large image format, hybridized focal planes becomes more challenging. These constraints call for tall indium bumps with high aspect ratio to accommodate die bowing and provide larger openings for the flow of fill epoxy. A process for the fabrication of highly uniform, high aspect ratio (height:diameter) indium bumps has been developed by Sensors Unlimited Inc. (SUI), a Collins Aerospace Company. The grain size of the deposited indium metal is minimized by optimizing process parameters as well as introducing intermediate metal layers underneath the indium bumps. Anisotropic deposition has been achieved by optimizing deposition rate and controlling substrate parameters. Indium bumps with aspect ratios over 2:1 and flat bump heads have been achieved. The developed bump process has been successfully applied to the fabrication of high resolution indium gallium arsenide (InGaAs) FPAs. Key control parameters for bump formation will be discussed in this paper.
KEYWORDS: Sensors, Acoustics, Interference (communication), Transducers, Analog electronics, Fourier transforms, Signal detection, Smart sensors, Data acquisition, Signal processing
Unattended ground monitoring that combines seismic and acoustic information can be a highly valuable tool in
intelligence gathering; however there are several prerequisites for this approach to be viable. The first is high
sensitivity as well as the ability to discriminate real threats from noise and other spurious signals. By combining
ground sensing with acoustic and image monitoring this requirement may be achieved. Moreover, the DS Sentry®provides innate spurious signal rejection by the "active-filtering" technique employed as well as embedding some
basic statistical analysis. Another primary requirement is spatial and temporal coverage. The ideal is
uninterrupted, long-term monitoring of an area. Therefore, sensors should be densely deployed and consume very
little power. Furthermore, sensors must be inexpensive and easily deployed to allow dense placements in critical
areas. The ADVIS DS Sentry®, which is a fully-custom integrated circuit that enables smart, micro-power
monitoring of dynamic signals, is the foundation of the proposed system. The core premise behind this technology
is the use of an ultra-low power front-end for active monitoring of dynamic signals in conjunction with a highresolution,
Σ Δ-based analog-to-digital converter, which utilizes a novel noise rejection technique and is only
employed when a potential threat has been detected. The DS Sentry® can be integrated with seismic accelerometers
and microphones and user-programmed to continuously monitor for signals with specific signatures such as impacts,
footsteps, excavation noise, vehicle-induced ground vibrations, or speech, while consuming only microwatts of
power. This will enable up to several years of continuous monitoring on a single small battery while concurrently
mitigating false threats.
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