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Photonics is a breakthrough technology as it uses photons (smallest unit of light) as the data carrier instead of electrons (smallest unit of electricity) used in electronic ICs. As light travels at very high speeds, photonics is widely used to transfer huge amounts of data at a very high speed. Thus photonics based products are primarily deployed in the field of optical fiber & optical free space communications. More recently, innovations in integrated photonics have allowed the miniaturization of key optical components and the ability to arrange several elements on a single silicon chip. A photonic integrated circuit (PIC) or integrated optical circuit is a device that integrates multiple (at least two) photonic functions and as such is similar to an electronic integrated circuit.
Lasers are essential to many fields – ranging from optical communications and remote sensing, to manufacturing and medicine. While the semiconductor laser was first demonstrated nearly 60 years ago, advances in diode lasers and access to semiconductor fabrication techniques have enabled continued innovation and miniaturization of the technology. When combined with lasers, these photonic integrated circuits (PICs) have the potential to replace large and costly optical systems with chip-scale solutions. The integration of photonic components such as lasers, optical amplifiers modulators, MUX/DEMUX components and photodiodes on chip would enable them to be used in optical signal processing, optical communication, biophotonics, and sensing applications.
Integrating lasers with silicon also brings with it many benefits, including an increase in the density of lasers, a reduction in coupling losses between the laser and the photonics, a reduction in the number of components required, and smaller, simpler packages. Photonic integrated circuits (PICs), which combine many photonic elements onto a single chip, have also transformed the way lasers and other optical systems are engineered, creating improvements in size, weight, and power (SWaP), system performance, and enabling new functionality.
However, due to differences in the properties of the materials that compose them, lasers and PICs are difficult to combine onto the same platform, limiting the benefits of integration and preventing broad technology impact. Number of obstacles still hamper the proliferation of optical systems for defense and commercial applications. “Commercial data center drivers have established integrated photonics platforms that address a specific market segment,” said Dr. Gordon Keeler, program manager in DARPA’s Microsystems Technology Office (MTO). “However, DoD-relevant applications typically require components with higher optical performance, such as lower noise lasers, higher power amplifiers, or operation in different spectral bands. As a result, critical and emerging applications are unable to leverage existing integrated photonics technology effectively.
To address this challenge, DARPA developed the Lasers for Universal Microscale Optical Systems (LUMOS) program, which aims to bring high-performance lasers to advanced photonics platforms. The development of a more capable integrated platform tailored to specialty user needs could have revolutionary impact.” LUMOS seeks to develop complete and highly capable integrated photonics platforms that enable efficient optical gain, high-speed modulation and detection, and low-loss passive functionality on a single chip. To illustrate the performance gains and SWaP improvements generated by complete component integration, LUMOS will pursue demonstrations on DoD-relevant systems throughout the life of the program.
LUMOS is a part of DARPA’s Electronics Resurgence Initiative (ERI) – a five-year, upwards of $1.5 billion initiative to develop techniques and technologies for advancing microelectronics performance beyond the limits of traditional transistor scaling that has helped realize the projections of Moore’s Law. One aspect of ERI is focused on the creation of unique and differentiated domestic manufacturing capabilities that are accessible to the DoD. In addition to a focus on DoD-relevant applications, LUMOS seeks to develop integrated photonics platforms that can be fabricated in existing foundries, making the technology more accessible for defense users.
LUMOS program objectives
Photonic integrated circuits (PICs) take several forms and are typically defined by the fundamental material used to create the integrated device platform. Inherent characteristics of the base materials lend strengths and weaknesses to each photonics approach. Compound semiconductors offer the important benefit of intrinsic optical gain and can be used to create efficient diode lasers and optical amplifiers of various designs. However, when used to build “active” integrated platforms, compound semiconductors suffer challenges that include limited manufacturing maturity, low component density due to weak confinement, and high propagation losses due to light absorption, scattering or other means.
These drawbacks have been largely avoided through “passive” silicon photonics platforms that emerged in the early 2000s. Such technologies offer low-loss, high-density photonic integration in accessible foundry environments and strongly leverage advances in electronics manufacturing.
While the vast silicon electronics manufacturing ecosystem has established silicon photonics as the premier platform for the integration of thousands of high-performance passive components on a single chip, fundamental material constraints preclude efficient generation of light, or optical gain, using on-chip components.
The selection of available materials has expanded rapidly to include not only silicon, but germanium, silica, and silicon nitride, while thin-film lithium niobate and numerous alternative materials show promise to enable key performance advantages. Nevertheless, the absence of intrinsic optical gain remains a critical limitation for optical microsystems built with such passive PICs.
Lacking availability of a complete integration solution, optical systems must employ components from different technology platforms today, combining diode lasers, integrated passive photonics, and optical fibers through various precision assembly techniques. This approach presents several problems beyond the obvious issues of non-ideal size, weight, and power (SWaP). The limited flexibility of such packaging approaches hampers performance and reduces the design innovation advantages of foundry-sourced photonics.
Moreover, custom packaging is typically most effective only for high-volume applications that can tolerate the considerable non-recurring development costs, while specialty users who demand higher performance such as lower noise, higher power, or operation in different spectral bands are forced to employ benchtop or separately-packaged discrete products. The lack of an integrated platform with complete functionality prevents greater photonics deployment and impact throughout many commercial sectors as well as across the Department of Defense (DoD).
Intimate heterogeneous integration represents a compelling path to combine best-in-class materials for universal photonics platforms that incorporate efficient optical gain, high-speed modulation and detection, and low-loss passive functionality on a single substrate. The past decade has seen extensive research on new materials that improve the performance of integrated photonics, as well as the development of promising heterogeneous integration techniques that can combine various materials during the fabrication process. However, there remains a large gap between today’s capabilities and the mature platforms needed to address most DoD-relevant applications.
LUMOS program
The Lasers for Universal Microscale Optical Systems (LUMOS) program aims to bring high performance lasers and amplifiers to manufacturable photonics platforms through heterogeneous integration of diverse materials. LUMOS seeks to develop integrated photonics technology along three vectors: scaling complexity, scaling power, and scaling spectrum. To achieve improved scaling in complexity, LUMOS seeks to integrate thousands of lasers and amplifiers with highly complex photonic integrated circuits for applications such as compact optical phased array LiDAR and neuromorphic optical computing. To achieve power scaling, LUMOS will aim to develop Watt-class lasers on a low-loss, high-speed photonics platform for radio frequency (RF) and microwave applications.
To address these requirements, LUMOS seeks to explore new materials and employ recent developments in heterogeneous integration techniques that combine best-in-class materials on a single chip. The objective of LUMOS is to bring efficient on-chip optical gain to highly-capable integrated photonics platforms and enable complete photonics functionality on a single substrate for disruptive optical microsystems.
LUMOS platforms will integrate lasers and amplifiers with high-performance modulators, waveguides, and detectors for diverse use cases, including digital and analog communications, navigation and timing, long-range sensing, microwave signal generation and processing, and quantum sensing and computing. Such uses demand a diversity of material combinations on photonics platforms tailored to address specific application areas. LUMOS will develop transformative PIC capabilities through heterogeneous integration to achieve integrated photonics scalability along three key directions: complexity, power, and spectrum.
The goal of LUMOS is to transform optical microsystems through the co-integration of direct-emission materials, such as InP, GaN, and GaAs, with low-loss dielectric materials such as silicon and silicon nitride to create accessible, manufacturable systems.
LUMOS also seeks to leverage new concepts in nanophotonic structures, non-reciprocity, and nonlinear processes, as well as alternative materials that possess strong electro-optic and novel properties, such as thin-film lithium niobate, III-nitrides, and other advanced compounds that enable new component functionality. Finally, LUMOS seeks to illustrate the benefits of complete component integration by pursuing DoD-relevant system demonstrations with compelling gains in performance and significant size, weight, and power (SWaP) advantages over current state-of-the-art solutions.
For scaling across the spectrum, LUMOS aims to create photonic circuits with integrated lasers operating across the visible spectrum with a wavelength-by-design methodology to enable atomic microsystems for positioning, navigation, and timing applications, as well as compact quantum sensors and information processing systems. An integrated platform with complete photonics functionality on a single chip would improve performance, support design innovation, and reduce development costs, enabling greater deployment and impact across many commercial sectors as well as the Department of Defense (DoD).
First, LUMOS seeks to dramatically scale the complexity and performance of very-large-scale integration (VLSI) photonic circuits through the development of an active platform that supports the integration of thousands of optical components on a single silicon chip. The fabrication of photonic circuits with >10,000 elements is possible today in high-yield foundry environments, but high optical losses limit the practical benefits of this scalability.
LUMOS will add flexible, high-density gain blocks that enable on-chip lasers and amplifiers for complexity scaling, HR001120S0008 10 overcoming on-chip losses through gain. Second, LUMOS seeks to transform high-power integrated photonics capabilities through the co-integration of low-noise, Watt-class lasers and amplifiers with fast analog components. Such a platform is expected to require intimate integration gain with low-loss optical materials capable of high saturation power levels, in combination with materials that support fast radio frequency (RF) modulation and detection for high dynamic range applications.
Finally, LUMOS seeks to create unprecedented capabilities for emerging visible and near-infrared applications through the development of a broadband visible and near-infrared photonics platform. Maximum utility would be achieved by a complete set of advanced components, including modulators, detectors, and narrow linewidth light sources, all capable of supporting operation across a wide spectral regime. These goals may be attained through the intimate combination of high-transparency substrates, direct emission materials at non-telecom wavelengths, and nonlinear nanophotonic devices that enable greater spectral access than individual gain materials can provide.
The LUMOS program will initially demonstrate on-chip gain integration of high-performance lasers and amplifiers. Next, LUMOS will demonstrate complete active PIC platforms tailored to meet specific application needs, driving improvements of both on-chip gain elements and supporting photonic components. Ultimately, LUMOS will deliver single-chip photonics demonstrators for each platform, targeting DoD-relevant concepts that are intended both to showcase platform capabilities and illustrate the compelling performance gains that can be achieved beyond current solutions.
Within the program, researchers are tasked with creating platforms optimized across three domains – complexity, power, and spectrum. With a focus on dramatically scaling the complexity and performance of silicon photonics technology, researchers will work to develop a platform that supports the integration of thousands of optical components on a single chip under the first research area.
In order to meet these goals, LUMOS is soliciting innovative research proposals in three main Technical Areas (TAs):
Technical Area 1 (TA1) – Scaling Complexity with Gain
This technical area will integrate dense, flexible optical gain in a silicon photonics foundry to achieve revolutionary VLSI photonic circuit technology. LUMOS TA1 will capitalize on the maturity of scalable passive photonics platforms, high precision foundry fabrication, and emerging technologies for gain integration to create complete photonic circuits with thousands of elements. This TA will establish an active silicon photonics platform in an 8″ or 12″ foundry that allows intimate integration of custom lasers and optical amplifiers with state-of-the-art active and passive component functionality. LUMOS TA1 will provide this capability to PIC designer teams (identified by the Government in later LUMOS phases) through multiple project wafer runs (MPWs) with preliminary process design kits (PDKs) developed during the TA1 activity. It is expected that the technologies created under TA1 will enable enduring dual-use access to active silicon photonics for both the defense and commercial user base.
A second research area will focus on the development of high-power, high-speed photonics platforms for defense applications.
Technical Area 2 (TA2) – High Power Gain
This technical area will integrate optical gain with low-loss materials that enable RF operation beyond 100 GHz to create high-power, high-speed photonics platforms. The development of low-noise Watt-class lasers and amplifiers integrated with broadband active and passive components will meet a number of critical defense applications, including high dynamic range microwave signal processing and long-range optical communication needs. Technologies developed in TA2 are expected to address moderate-volume, defense-specific applications and commercial needs.
A third area seeks to develop visible and near-infrared photonics platforms, capable of supporting new classes of applications such as critical sensing, timing, and quantum information applications. Each research area will explore on-chip gain integration strategies and PIC platforms tailored for application-specific needs.
Technical Area 3 (TA3) – Broad Spectrum Gain
This technical area will develop visible and near-infrared photonics platforms with integrated light sources and full component functionality that support new classes of applications. In particular, platform metrics target the need to address spectral signatures from various atomic and molecular species for critical sensing, timing, and quantum information applications. LUMOS TA3 seeks revolutionary breakthroughs in nanophotonics, nonlinear materials, and integrated laser architectures to enable a complete platform that supports operation from 400 nm to 900 nm, with ultra-narrow linewidth, high-performance lasers available to designers across the entire spectral regime.
LUMOS Awards
DARPA has also tapped a number of “performer teams” for LUMOS to create demonstration systems in “three distinct technical areas” where putting lasers on silicon could spur new commercial and defense applications.
The first LUMOS Technical Area brings high-performance lasers and optical amplifiers into advanced domestic photonics manufacturing foundries. Two research teams were selected in this area: Tower Semiconductor and SUNY Polytechnic Institute. These performers will work to demonstrate flexible, efficient on-chip optical gain in their photonics processes to enable next-generation optical microsystems for communications, computing, and sensing. LUMOS technologies will be made available to future design teams through DARPA-sponsored multi-project wafer runs.
Under this partnership, Tower Semiconductor aims to demonstrate flexible, efficient on-chip optical gain in their photonics processes. This may enable next-generation optical microsystems for key communications, computing, and sensing applications. To achieve this, Tower Semiconductor will combine high-performance III-V laser diodes with its PH18 production silicon photonics platform. When ready, multi-project wafer (MPW) runs will be coordinated with the new process.
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Tower Semiconductor offers a Multi-Project Wafer (MPW) shuttle program. Image used courtesy of Tower Semiconductor
Another, including Ultra-Low Loss Technologies, Quintessent, Harvard University, and Sandia National Laboratories, will zero in on developing integrated high-power lasers and amplifiers for microwave applications.
The final LUMOS Technical Area creates precise lasers and integrated photonic circuits for visible spectrum applications with an ambitious goal of “wavelength by design” across an unprecedented spectral range. The teams will seek to develop lasers at many challenging wavelengths throughout the program to enable compact atomic sensors for navigation, precise timing solutions, and emerging quantum information hardware.
AIM Photonics (American Institute for Manufacturing Integrated Photonics), part of NY CREATES, announced $19 million in research program awards for advanced integrated photonics research projects. The awards are under the Defense Advanced Research Projects Agency’s (DARPA) Lasers for Universal Microscale Optical Systems (LUMOS) program. Per the award, AIM Photonics will lead a team of academic, industrial, and government partners working to advance existing technology and develop new technologies for applications with self-driving vehicles, AR, 3D camera technology, and quantum computing. In addition to applications in those areas, AIM Photonics CEO Michael Cumbo identified benefits to military microsystems, big data, and biosensing as those to which the award will contribute. Additional program partners include the University of California, Santa Barbara; Analog Photonics; IQE; and NAsPIII/V GmbH.
Beyond addressing equipment and process challenges associated with the photonics technology, the LUMOS team, through the funding, will develop a standard laser design into nontraditional, silicon-based integration. Analog Photonics, a Tier 1 AIM Photonics member and partner in design, will assist with system implementation.
“Eight years ago, a team of engineers from the Albany Fab and Analog Photonics began implementing our first PIC (photonic integrated chip) designs and our first DARPA program,” said Mike Watts, CEO of Analog Photonics, and AIM Photonics CTO. “Back then, we didn’t have the capabilities to even consider direct integration of gain on-chip. Fast forward eight years later, including five years with AIM Photonics, we are now accelerating this technology to a level of maturity approaching CMOS electronics, including lidar on a chip, which will ultimately make self-driving vehicles mainstream and 3D camera technology standard in consumer electronics.”
References and Resources also include:
https://www.photonics.com/Articles/AIM_Photonics_to_Lead_19M_DARPA-Funded_Photonics/a66453
https://www.allaboutcircuits.com/news/integrated-laser-on-silicon-photonics-boost-darpa/
