electronics Archives - EFFECT Photonics

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September 4, 2024

Leveraging Electronic Ecosystems in Photonics

(First published on the 2nd November 2022 updated 4th September 2024) Thanks to wafer-scale technology,…

(First published on the 2nd November 2022 updated 4th September 2024)

Thanks to wafer-scale technology, electronics have driven down the cost per transistor for many decades. This allowed the world to enjoy chips that every generation became smaller and provided exponentially more computing power for the same amount of money. This scale-up process is how everyone now has a computer processor in their pocket that is millions of times more powerful than the most advanced computers of the 1960s that landed men on the moon.

This progress in electronics integration is a key factor that brought down the size and cost of coherent transceivers, packing more bits than ever into smaller areas. However, photonics has struggled to keep up with electronics, with the photonic components dominating the cost of transceivers. If the transceiver cost curve does not continue to decrease, it will be challenging to achieve the goal of making them more accessible across the entire optical network.

To trigger a revolution in the use of photonics worldwide, it needs to be as easy to use as electronics. In the words of our Chief Technology Officer, Tim Koene-Ong:

“We need to buy photonics products from a catalog as we do with electronics, have datasheets that work consistently, be able to solder it to a board and integrate it easily with the rest of the product design flow.”
Tim Koene-Ong, Chief Technology Officer.

This goal requires photonics manufacturing to leverage existing electronics manufacturing processes and ecosystems. Photonics must embrace fabless models, chips that can survive soldering steps, and electronic packaging and assembly methods.

The Advantages of a Fabless Model

Increasing the volume of photonics manufacturing is a big challenge. Some photonic chip developers manufacture their chips in-house within their fabrication facilities. This approach has substantial advantages, giving component manufacturers complete control over their production process.

Figure-vertically-integrated — Figure 1: Simplified value chain diagram of a vertically-integrated optical transceiver developer. The developer handles the PIC design, manufacturing, and packaging.

However, this approach has its trade-offs when scaling up. If a vertically integrated chip developer wants to scale up in volume, they must make a hefty capital expenditure (CAPEX) in more equipment and personnel. They must develop new fabrication processes as well as develop and train personnel. Fabs are not only expensive to build but to operate. Unless they can be kept at nearly full utilization, operating expenses (OPEX) also drain the facility owners’ finances.

Especially in the case of an optical transceiver market that is not as big as that of consumer electronics, it’s hard not to wonder whether that initial investment is cost-effective. For example, LightCounting research data estimates that 173 million optical Ethernet transceivers were sold in 2023, while the International Data Corporation estimates that 1.17 billion smartphones were sold in 2023. The latter figure is seven times larger than the entire optical transceiver market.

Electronics manufacturing experienced a similar problem during their 70s and 80s boom, with smaller chip start-ups facing almost insurmountable barriers to market entry because of the massive CAPEX required. Furthermore, the large-scale electronics manufacturing foundries had excess production capacity that drained their OPEX. The large-scale foundries sold that excess capacity to the smaller chip developers, who became fabless. In this scenario, everyone ended up winning. The foundries serviced multiple companies and could run their facilities at total capacity, while the fabless companies could outsource manufacturing and reduce their expenditures.

This fabless model, with companies designing and selling the chips but outsourcing the manufacturing, should also be the way for photonics. Instead of going through a more costly, time-consuming process, the troubles of scaling up for photonics developers are outsourced and (from the perspective of the fabless company) become as simple as putting a purchase order in place. Furthermore, the fabless model allows photonics developers to concentrate their R&D resources on the end market. This is the simplest way forward if photonics moves into million-scale volumes.

Adopting Electronics-Style Packaging

While packaging, assembly, and testing are only a small part of the cost of electronic systems, the reverse happens with photonic integrated circuits (PICs). Researchers at the Technical University of Eindhoven (TU/e) estimate that for most Indium Phosphide (InP) photonics devices, the cost of packaging, assembly, and testing can reach around 80% of the total module cost.

To become more accessible and affordable, the photonics manufacturing chain must become more automated and standardized. The lack of automation makes manufacturing slower and prevents data collection that can be used for process control, optimization, and standardization.

One of the best ways to reach these automation and standardization goals is to learn from electronics packaging, assembly, and testing methods that are already well-known and standardized. After all, building a special production line is much more expensive than modifying an existing production flow.

There are several ways in which photonics packaging, assembly, and testing can be made more affordable and accessible. Below are a few examples:

Passive alignments: Connecting optical fiber to PICs is one of optical devices’ most complicated packaging and assembly problems. The best alignments are usually achieved via active alignment processes in which feedback from the PIC is used to align the fiber better. Passive alignment processes do not use such feedback. They cannot achieve the best possible alignment but are much more affordable.
BGA-style packaging: Ball-grid array packaging has grown popular among electronics manufacturers. It places the chip connections under the chip package, allowing more efficient use of space in circuit boards, a smaller package size, and better soldering.

Figure 3: Top, bottom, and side views of a ball-grid array (BGA) style package.

Flip-chip bonding: A process where solder bumps are deposited on the chip in the final fabrication step. The chip is flipped over and aligned with a circuit board for easier soldering.

Figure 4: Simplified steps of the flip chip bonding process.

These might be novel technologies for photonics developers who have started implementing them in the last five or ten years. However, the electronics industry embraced these technologies 20 or 30 years ago. Making these techniques more widespread will make a massive difference in photonics’ ability to scale up and become as available as electronics.

Making Photonics Chips That Can Survive Soldering

Soldering remains another tricky step for photonics assembly and packaging. Photonics device developers usually custom order a PIC, then wire and die bond to the electronics. However, some elements in the PIC cannot handle soldering temperatures, making it difficult to solder into an electronics board. Developers often must glue the chip onto the board with a non-standard process that needs additional verification for reliability.

This goes back to the issue of process standardization. Current PICs often use different materials and processes from electronics, such as optical fiber connections and metals for chip interconnects, that cannot survive a standard soldering process.

Adopting BGA-style packaging and flip-chip bonding techniques will make it easier for PICs to survive this soldering process. There is ongoing research and development worldwide, including at EFFECT Photonics, to make fiber coupling and other PIC aspects compatible with these electronic packaging methods.

PICs that can handle being soldered to circuit boards will allow the industry to build optical subassemblies that can be made more readily available in the open market and can go into trains, cars, or airplanes.

Conclusion

Photonics must leverage existing electronics ecosystems and processes to scale up and have a greater global impact. Our Chief Technology Officer, Tim Koene-Ong, explains what this means:

Photonics technology needs to integrate more electronic functionalities into the same package. It needs to build photonic integration and packaging support that plays by the rules of existing electronic manufacturing ecosystems. It needs to be built on a semiconductor manufacturing process that can produce millions of chips in a month.

As soon as photonics can achieve these larger production volumes, it can reach price points and improvements in quality and yield closer to those of electronics. When we show the market that photonics can be as easy to use as electronics, that will trigger a revolution in its worldwide use.
Our Chief Technology Officer, Tim Koene-Ong.

This vision is one of our guiding lights at EFFECT Photonics, where we aim to develop optical systems that can impact the world in many different applications.

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Tags: automotive sector, BGA style packaging, compatible, computing power, cost per mm, efficient, electronic, electronic board, electronics, fabless, Photonics, risk, scale, soldering, transistor, wafer scale

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May 22, 2024

Why Semiconductors are Vital to Optics and Photonics

Thanks to wafer-scale technology, electronics have driven down the cost per transistor for many decades.…

Thanks to wafer-scale technology, electronics have driven down the cost per transistor for many decades. This allowed the world to enjoy chips that every generation became smaller and provided exponentially more computing power for the same amount of money. This scale-up process is how everyone now has a computer processor in their pocket that is millions of times more powerful than the most advanced computers of the 1960s that landed men on the moon.

For example, this progress in electronics integration is a key factor that brought down the size and cost of coherent transceivers, packing more bits than ever into smaller areas. However, photonics has struggled to keep up with electronics, with the photonic components dominating the cost of transceivers. Making transceivers more accessible across the entire optical network requires bringing down these costs.

In this article, we will explore a bit of the relationship between optics and semiconductors and explain what optics can learn from electronics when it comes to semiconductor processes.

At the Heart of Photonic Systems

Semiconductor materials are vital for photonics due to their electronic and optical properties. These materials have a bandgap that can be precisely manipulated to control the absorption and emission of light, and this is essential for creating photonic devices like lasers and photodetectors. The ability to engineer the electronic structure of semiconductors like silicon, gallium arsenide (GaAs), and indium phosphide (InP) allows for the design of devices that operate across various wavelengths of light. These capabilities allow us to develop efficient, compact, and versatile photonic components.

Moreover, semiconductor fabrication techniques, inherited from the microelectronics industry, enable the mass production of photonic devices, which supports scalability and integration of photonics with existing electronic systems. If photonics becomes as readily available and easy to use as electronics, it can become more widespread and have an even greater impact on the world.

“We need to buy photonics from a catalog as we do with electronics, have datasheets that work consistently, be able to solder it to a board and integrate it easily with the rest of the product design flow.“
Tim Koene – Chief Technology Officer, EFFECT Photonics

Some differences between electronics and photonics complicate this transition. Silicon, the dominant material in microelectronics, cannot naturally emit laser light from electrical signals. Therefore, making suitable components for integrated photonics often requires using III-V semiconductor materials such as InP and GaAs. The need for these non-silicon semiconductors has made the photonics manufacturing space harder to standardize and streamline than microelectronics.

The Need for a Fabless Model

Increasing the volume of photonics manufacturing is a big challenge. Some photonic chip developers manufacture their chips in-house within their fabrication facilities. This approach has some substantial advantages, giving component manufacturers complete control over their production process.

Figure 1: Simplified value chain diagram of a vertically-integrated optical transceiver developer. The developer handles the PIC design, manufacturing, and packaging.

However, this approach has its trade-offs when scaling up. If a vertically-integrated chip developer wants to scale up in volume, they must make a hefty capital expenditure (CAPEX) in more equipment and personnel. They must develop new fabrication processes as well as develop and train personnel. Fabs are not only expensive to build but to operate. Unless they can be kept at nearly full utilization, operating expenses (OPEX) also drain the facility owners’ finances.

Especially in the case of an optical transceiver market that is not as big as that of consumer electronics, it’s hard not to wonder whether that initial investment is cost-effective. For example, LightCounting estimates that 55 million optical transceivers were sold in 2021, while the International Data Corporation estimates that 1.4 billion smartphones were sold in 2021. The latter figure is 25 times larger than that of the transceiver market.

Electronics manufacturing experienced a similar problem during their 70s and 80s boom, with smaller chip start-ups facing almost insurmountable barriers to market entry because of the massive CAPEX required. Furthermore, the large-scale electronics manufacturing foundries had excess production capacity that drained their OPEX. The large-scale foundries ended up selling that excess capacity to the smaller chip developers, who became fabless. In this scenario, everyone ended up winning. The foundries serviced multiple companies and could run their facilities at total capacity, while the fabless companies could outsource manufacturing and reduce their expenditures.

This fabless model, with companies designing and selling the chips but outsourcing the manufacturing, should also be the way to go for photonics. Instead of going through a more costly, time-consuming process, the troubles of scaling up for photonics developers are outsourced and (from the perspective of the fabless company) become as simple as putting a purchase order in place. Furthermore, the fabless model allows photonics developers to concentrate their R&D resources on the end market. This is the simplest way forward if photonics moves into million-scale volumes.

Investment is Needed for Photonics to Scale like Electronics

Today, photonics is still a ways off from achieving the goal of becoming more like electronics in its manufacturing process. Photonics manufacturing chains are not at a point where they can quickly produce millions of integrated photonic devices per year. While packaging, assembly, and testing are only a small part of the cost of electronic systems, they are 80% of the total module cost in photonics, as shown in the figure below.

To scale and become more affordable, the photonics manufacturing chains must become more automated and leverage existing electronic packaging, assembly, and testing methods that are already well-known and standardized. Technologies like BGA-style packaging and flip-chip bonding might be novel for photonics developers who started implementing them in the last five or ten years, but electronics embraced these technologies 20 or 30 years ago. Making these techniques more widespread will make a massive difference in photonics’ ability to scale up and become as available as electronics.

The roadmap of scaling integrated photonics and making it more accessible is clear: it must leverage existing electronics manufacturing processes and ecosystems and tap into the same economy-of-scale principles as electronics. Implementing this roadmap, however, requires more investment in photonics. While such high-volume photonics manufacturing demands a higher upfront investment, the resulting high-volume production line will drive down the cost per device and opens them up to a much larger market. That’s the process by which electronics revolutionized the world.

Takeaways

A robust investment is needed to better adapt and integrate microelectronic semiconductor processes into the photonics manufacturing chain to harness the full potential of photonic technologies. Such advancements will not only refine the production scales but also enhance the accessibility and affordability of photonic solutions.

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Tags: bandgap, BGA style packaging, Coherent Transceivers, computing power, economy-of-scale principles, EFFECT Photonics, electronic packaging, electronics, Fabless model, Flip-chip bonding, GaAs, high-volume production, III-V semiconductor materials, InP, Investment, lasers, manufacturing chains, microelectronics industry, optical network, Optics, Photodetectors, photonic components, Photonic devices, photonic solutions, Photonics, photonics developers, photonics manufacturing, Semiconductor, semiconductor fabrication techniques, silicon, transistor, wafer-scale technology

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January 10, 2024

From the Lab Boutique to High Volume Production: How to Scale Up Photonics Manufacturing

Photonics, the science and technology of generating, detecting, and manipulating light, has witnessed remarkable progress…

Photonics, the science and technology of generating, detecting, and manipulating light, has witnessed remarkable progress in recent years. From cutting-edge research in academic labs to breakthrough innovations in startups, photonics is poised to revolutionize various industries, from telecommunications to healthcare. However, despite its tremendous potential, the transition from boutique lab-scale production to high-volume manufacturing remains a significant challenge.

To overcome this hurdle, the photonics industry must draw lessons from the successful scaling of electronics manufacturing. By adopting key strategies and practices that have propelled the electronics industry into the realm of mass production, photonics can pave the way for widespread adoption and integration into our everyday lives.

Learning from Electronics Packaging

A key way to improve photonics manufacturing is to learn from electronics packaging, assembly, and testing methods that are already well-known and standardized. After all, building a new special production line is much more expensive than modifying an existing production flow.

One electronic technique essential to transfer into photonics is ball-grid array (BGA) packaging. BGA-style packaging has grown popular among electronics manufacturers over the last few decades. It places the chip connections under the chip package, allowing more efficient use of space in circuit boards, a smaller package size, and better soldering.

Another critical technique to move into photonics is flip-chip bonding. This process is where solder bumps are deposited on the chip in the final fabrication step. The chip is flipped over and aligned with a circuit board for easier soldering.

These might be novel technologies for photonics developers who have started implementing them in the last five or ten years. However, the electronics industry embraced these technologies 20 or 30 years ago. Making these techniques more widespread will make a massive difference in photonics’ ability to scale up and become as available as electronics.

Adopting BGA-style packaging and flip-chip bonding techniques will make it easier for PICs to survive this soldering process. There is ongoing research and development worldwide, including at EFFECT Photonics, to transfer more electronics packaging methods into photonics. PICs that can handle being soldered to circuit boards allow the industry to build optical subassemblies that are more accessible to the open market and can go into trains, cars, or airplanes.

Supply Chain Optimization

Electronics manufacturers have honed the art of supply chain management to achieve cost-effective and efficient production processes. This includes strategies like just-in-time inventory management, lean manufacturing principles, and global sourcing. In contrast, the photonics industry often faces challenges related to specialized materials and components, resulting in longer lead times and higher costs.

Photonics manufacturers can learn from electronics by implementing supply chain optimization strategies. This involves diversifying sources, streamlining production workflows, and leveraging economies of scale. By fostering strategic partnerships with suppliers and embracing advanced inventory management systems, the photonics industry can overcome the hurdles that have hindered its growth.

Figure 3: Key locations of EFFECT Photonics’ global supply chain. This includes our offices but also some locations where manufacturing is outsourced. We don’t mention the locations of our off-the-shelf component suppliers.

The Advantages of Moving to a Fabless Model

Increasing the volume of photonics manufacturing is a big challenge. Some photonic chip developers manufacture their chips in-house within their fabrication facilities. This approach has some substantial advantages, giving component manufacturers complete control over their production process.

However, if a vertically-integrated chip developer wants to scale up in volume, they must make a hefty capital expenditure (CAPEX) in more equipment and personnel. They must develop new fabrication processes as well as develop and train personnel. Fabs are not only expensive to build but to operate. Unless they can be kept at nearly full utilization, operating expenses (OPEX) also drain the facility owners’ finances.

Especially in the case of an optical transceiver market that is not as big as that of consumer electronics, it’s hard not to wonder whether that initial investment is cost-effective. For example, LightCounting estimates that 55 million optical transceivers were sold in 2021, while the International Data Corporation estimates that 1.4 billion smartphones were sold in 2021. The latter figure is 25 times larger than that of the transceiver market.

Electronics manufacturing experienced a similar problem during their 70s and 80s boom, with smaller chip start-ups facing almost insurmountable barriers to market entry because of the massive CAPEX required. Furthermore, the large-scale electronics manufacturing foundries had excess production capacity that drained their OPEX. The large-scale foundries ended up selling that excess capacity to the smaller chip developers, who became fabless. In this scenario, everyone ended up winning. The foundries serviced multiple companies and could run their facilities at total capacity, while the fabless companies could outsource manufacturing and reduce their expenditures.

This fabless model, with companies designing and selling the chips but outsourcing the manufacturing, could also be the way to go for photonics. The troubles of scaling up for photonics developers are outsourced and (from the perspective of the fabless company) become as simple as putting a purchase order in place. Furthermore, the fabless model allows photonics developers to concentrate their R&D resources on the end market. This might be the most straightforward way for photonics to move into million-scale volumes.

Takeaways

Scaling up photonics manufacturing from boutique labs to high-volume production is a pivotal step in realizing the full potential of this transformative technology. By taking a page from the electronics industry’s playbook, focusing on standardization, optimizing the supply chain, and embracing automation, the photonics industry can overcome the challenges that have impeded its growth. With concerted efforts and strategic investments, the future of photonics looks poised for a paradigm shift, bringing us closer to a world illuminated by the power of light.

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Tags: automation, BGA packaging, EFFECT Photonics, electronics, Fabless model, Flip-chip bonding, Global sourcing, innovation, Integrated circuits, Integrated Photonics, Just-in-time inventory, Lean manufacturing, Manufacturing, Optical transceiver, Photonics, PICs (Photonic Integrated Circuits), R&D, Scaling up, Semiconductor, Standardization, supply chain

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June 7, 2023

What do Next-Gen Optical Subassemblies Need?

While packaging, assembly, and testing are only a small part of the cost of electronic…

While packaging, assembly, and testing are only a small part of the cost of electronic systems, the reverse happens with photonic integrated circuits (PICs) and their subassemblies. Researchers at the Technical University of Eindhoven (TU/e) estimate that for most Indium Phosphide (InP) photonics devices, the cost of packaging, assembly, and testing can reach around 80% of the total module cost.

Figure 1. Process cost breakdown of an InP PIC-based module as a percentage of the overall manufacturing cost. Source: Latkowski et al., 2019

To trigger a revolution in the use of photonics worldwide, it needs to be as easy to manufacture and use as electronics. In the words of EFFECT Photonics’ Chief Technology Officer, Tim Koene: “We need to buy photonics from a catalog as we do with electronics, have datasheets that work consistently, be able to solder it to a board and integrate it easily with the rest of the product design flow.”

This article will explore three key avenues to improve optical subassemblies and packaging for photonic devices.

Learning from Electronics Packaging

A key way to improve photonics manufacturing is to learn from electronics packaging, assembly, and testing methods that are already well-known and standardized. After all, building a new special production line is much more expensive than modifying an existing production flow.

One electronic technique essential to transfer into photonics is ball-grid array (BGA) packaging. BGA-style packaging has grown popular among electronics manufacturers over the last few decades. It places the chip connections under the chip package, allowing more efficient use of space in circuit boards, a smaller package size, and better soldering.

Figure 2: Top, bottom, and side views of a ball-grid array (BGA) style package.

Another critical technique to move into photonics is flip-chip bonding. This process is where solder bumps are deposited on the chip in the final fabrication step. The chip is flipped over and aligned with a circuit board for easier soldering.

Figure 3: Simplified steps of the flip chip bonding process.

These might be novel technologies for photonics developers who have started implementing them in the last five or ten years. However, the electronics industry embraced these technologies 20 or 30 years ago. Making these techniques more widespread will make a massive difference in photonics’ ability to scale up and become as available as electronics.

Adopting BGA-style packaging and flip-chip bonding techniques will make it easier for PICs to survive this soldering process. There is ongoing research and development worldwide, including at EFFECT Photonics, to transfer more electronics packaging methods into photonics. PICs that can handle being soldered to circuit boards allow the industry to build optical subassemblies that are more accessible to the open market and can go into trains, cars, or airplanes.

The Benefits of Increasing Integration

Economics of scale is a crucial principle behind electronics manufacturing, and we must apply it to photonics too. The more components we can integrate into a single chip and the more chips we can integrate into a single wafer, the more affordable the photonic device becomes. If production volumes increase from a few thousand chips per year to a few million, the price per optical chip can decrease from thousands of Euros to mere tens of Euros. This must be the goal for the photonics industry in general.

By integrating all optical components on a single chip, we also shift the complexity from the assembly process to the much more efficient and scalable semiconductor wafer process. Assembling and packaging a device by interconnecting multiple photonic chips increases assembly complexity and costs. On the other hand, combining and aligning optical components on a wafer at a high volume is much easier, which drives down the device’s cost.

Deepening photonics integration will also have a significant impact on power consumption. Integrating all the optical components (lasers, detectors, modulators, etc.) on a single chip can minimize the losses and make devices such as optical transceivers more efficient. This approach doesn’t just optimize the efficiency of the devices themselves but also of the resource-hungry chip manufacturing process.

The Importance of Laser Packaging

Over the last decade, technological progress in tunable laser packaging and integration has matched the need for smaller footprints. In 2011, tunable lasers followed the multi-source agreement (MSA) for integrable tunable laser assemblies (ITLAs). By 2015, tunable lasers were sold in the more compact Micro-ITLA form factor, which cut the original ITLA package size in half. And in 2019, laser developers (see examples here and here) announced a new Nano-ITLA form factor that reduced the size by almost half again.

Figure 4: Evolution of tunable laser form factors for coherent optics (2011-2021). Figure inspired from a picture in Laser Focus World.

Reducing the footprint of tunable lasers in the future will need even greater integration of their parts. For example, every tunable laser needs a wavelength locker component that can stabilize the laser’s output regardless of environmental conditions such as temperature. Integrating the wavelength locker component on the laser chip instead of attaching it externally would help reduce the laser package’s footprint and power consumption.

Another aspect of optimizing laser module footprint is allowing transceiver developers to mix and match their building blocks. For example, traditional ITLAs in transceivers contain the temperature control driver and power converter functions. However, the main transceiver board can usually provide these functions too. A setup in which the main board performs these driver and converter functions would avoid the need for redundant elements in both the main board and tunable laser.

Finally, the future of laser packaging will also involve packaging more multi-laser arrays. As explained in a previous article, multi-laser arrays will become increasingly necessary to increase link capacity in coherent systems. They will not need more slots in the router faceplate while avoiding the higher cost and complexity of increasing the speed with a single laser channel.

Takeaways

Improving subassemblies and packaging is vital for photonics to reach its potential. Photonics must learn from well-established, standardized electronics packaging techniques like BGA-style packaging and flip-chip bonding. By increasing integration, photonics can achieve economies of scale that make devices more affordable and energy efficient. In this context, improved integration and packaging of tunable lasers and arrays will be particularly important. Overall, these efforts will make photonics more accessible to the open market and make it as easy to manufacture and use as electronics.

Tags: Assembly, electronics, flip chip bonding, integration, Manufacturing, Packaging, Photonics, Subassemblies, testing

Photonic technology more available to all Industries

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March 15, 2023

Coherent Optics In Space

When it started, the space race was a competition between two superpowers, but now there…

When it started, the space race was a competition between two superpowers, but now there are 90 countries with missions in space.

The prices of space travel have gone down, making it possible for more than just governments to send rockets and satellites into space. Several private companies are now investing in space programs, looking for everything from scientific advances to business opportunities. Some reports estimate more than 10,000 companies in the space industry and around 5,000 investors.

According to The Space Foundation’s 2022 report, the space economy was worth $469 billion in 2021. The report says more spacecraft were launched in the first six months of 2021 than in the first 52 years of space exploration (1957-2009). This growing industry has thus a growing need for technology products across many disciplines, including telecommunications. The space sector will need lighter, more affordable telecommunication systems that also provide increased bandwidth.

This is why EFFECT Photonics sees future opportunities for coherent technology in the space industry. By translating the coherent transmission from fiber communication systems on the ground to free-space optical systems, the space sector can benefit from solutions with more bandwidth capacity and less power consumption than traditional point-to-point microwave links.

It’s all About SWaP

One of the major concerns of the space industry is the cost of sending anything into space. Even during the days of NASA’s Space Shuttle program (which featured a reusable shuttle unit), sending a kilogram into space cost tens of thousands of dollars. Over time, more rocket stages have become reusable due to the efforts of companies like SpaceX, reducing these costs to just a few thousand. The figure below shows how the cost of space flight has decreased significantly in the last two decades.

Figure 1: The cost of a kilogram of payload into space since 2000. Source: Visual Capitalist (data from the Center for Strategic and International Studies)

Even though space travel is more affordable than ever, size, weight, and power (SWaP) requirements are still vital in the space industry. After all, shaving off weight or size in the spacecraft means a less expensive launch or perhaps room for more scientific instruments. Meanwhile, less power consumption means less drain on the spacecraft’s energy sources.

Using Optics and Photonics to Minimize SWaP Requirements

Currently, most space missions use bulkier radio frequency communications to send data to and from spacecraft. While radio waves have a proven track record of success in space missions, generating and collecting more mission data requires enhanced communications capabilities. Besides, radiofrequency equipment can often generate a lot of heat, requiring more energy to cool the system.

Decreasing SWaP requirements can be achieved with more photonics and miniaturization. Transmitting data with light will usually dissipate less than heat than transmission with electrical signals and radio waves. These leads to smaller, lighter communication systems that require less power to run.

These SWaP advantages come alongside the increased transmission speeds. After all, coherent optical communications can increase link capacities to spacecraft and satellites by 10 to 100 times that of radio frequency systems.

Leveraging Electronics Ecosystems for Space Certification and Standardization

While integrated photonics can boost space communications by lowering the payload, it must overcome the obstacles of a harsh space environment, which include radiation hardness, an extreme operational temperature range, and vacuum conditions.

*Mission Type*	*Temperature Range*
Pressurized Module	+18.3 ºC to 26.7 °C
Low-Earth Orbit (LEO)	-65 ºC to +125 °C
Geosynchronous Equatorial Orbit (GEO)	-196 ºC to +128 °C
Trans-Atmospheric Vehicle	-200 ºC to +260 ºC
Lunar Surface	-171 ºC to +111 ºC
Martian Surface	-143 ºC to +27 ºC

Table 1. Temperature Extremes by Mission Type. Source: NASA

The values in Table 1 show the unmanaged environmental temperatures in different space environments. In a temperature-managed area, these would decrease significantly for electronics and optics systems, perhaps by as much as half. Despite this management, the equipment would still need to deal with some extreme temperature values.

Fortunately, a substantial body of knowledge exists to make integrated photonics compatible with space environments. After all, photonic integrated circuits (PICs) use similar materials to their electronic counterparts, which have already been space qualified in many implementations.

Much research has gone into overcoming the challenges of packaging PICs with electronics and optical fibers for these space environments, which must include hermetic seals and avoid epoxies. Commercial solutions, such as those offered by PHIX Photonics Assembly, Technobis IPS, and the PIXAPP Photonic Packaging Pilot Line, are now available.

Takeaways

Whenever you want to send data from point A to B, photonics is usually the most efficient way of doing it, be it over fiber or free space.

Offering optical communication systems in a small integrated package that can resist the required environmental conditions will significantly benefit the space sector and its need to minimize SWaP requirements. These optical systems can increase their transmission capacity with the coherent optical transmission used in fiber optics. Furthermore, by leveraging the assembly and packaging structure of electronics for the space sector, photonics can also provide the systems with the ruggedness required to live in space.

Tags: certification, coherent, electronics, existing, fast, growing, heat dissipation, miniaturization, Optical Communication, Photonics, power consumption, size, space, space sector, speed, SWAP, temperature, weight

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December 7, 2022

The Power of Integrated Photonic LIDAR

Outside of communications applications, photonics can play a major role in sensing and imaging applications.…

Outside of communications applications, photonics can play a major role in sensing and imaging applications. The most well-known of these sensing applications is Light Detection and Ranging (LIDAR), which is the light-based cousin of RADAR systems that use radio waves.

To put it in a simple way: LIDAR involves sending out a pulse of light, receiving it back, and using a computer to study how the environment changes that pulse. It’s a simple but quite powerful concept.

Figure 1: Diagram of a time-of-flight LIDAR system

If we send pulses of light to a wall and listen to how long it takes for them to come back, we know how far that wall is. That is the basis of time-of-flight (TOF) LIDAR. If we send a pulse of light with multiple wavelengths to an object, we know where the object is and whether it is moving towards you or away from you. That is next-gen LIDAR, known as FMCW LIDAR. These technologies are already used in self-driving cars to figure out the location and distance of other cars. The following video provides a short explainer of how LIDAR works in self-driving cars.

Despite their usefulness, the wider implementation of LIDAR systems is limited by their size, weight, and power (SWAP) requirements. Or, to put it bluntly, they are bulky and expensive. For example, maybe you have seen pictures and videos of self-driving cars with a large LIDAR sensor and scanner on the roof of the car, as in the image below.

Figure 2: LiDAR sensors and camera on roof of a self-driving car.

Making LIDAR systems more affordable and lighter requires integrating the optical components more tightly and manufacturing them at a higher volume. Unsurprisingly, this sounds like a problem that could be solved by integrated photonics.

Replacing Bulk LIDAR with “LIDAR on Chip”

Back in 2019, Tesla CEO Elon Musk famously said that “Anyone relying on LIDAR is doomed”. And his scepticism had some substance to it. LIDAR sensors were clunky and expensive, and it wasn’t clear that they would be a better solution than just using regular cameras with huge amounts of visual analysis software. However, the incentive to dominate the future of the automotive sector was too big, and a technology arms race had already begun to miniaturize LIDAR systems into a single photonic chip.

Let’s provide a key example. A typical LIDAR system will require a mechanical system that moves the light source around to scan the environment. This could be as simple as a 360-rotating LIDAR scanner or using small scanning mirrors to steer the beam. However, an even better solution would be to create a LIDAR scanner with no moving parts that could be manufactured at a massive scale on a typical semiconductor process.

This is where optical phased arrays (OPAs) systems come in. An OPA system splits the output of a tunable laser into multiple channels and puts different time delays on each channels. The OPA will then recombine the channels, and depending on the time delays assigned, the resulting light beam will come out at a different angle. In other words, an OPA system can steer a beam of light from a semiconductor chip without any moving parts.

Figure 2 Diagram of an optical phased array on a chip

There is still plenty of development required to bring OPAs into maturity. Victor Dolores Calzadilla, a researcher from the Eindhoven University of Technology (TU/e) explains that “The OPA is the biggest bottleneck for achieving a truly solid-state, monolithic lidar. Many lidar building blocks, such as photodetectors and optical amplifiers, were developed years ago for other applications, like telecommunication. Even though they’re generally not yet optimized for lidar, they are available in principle. OPAs were not needed in telecom, so work on them started much later. This component is the least mature.”

Economics of Scale in LIDAR Systems

Wafer scale photonics manufacturing demands a higher upfront investment, but the resulting high-volume production line drives down the cost per device. This economy-of-scale principle is the same one behind electronics manufacturing, and the same must be applied to photonics. The more optical components we can integrate into a single chip, the more can the price of each component decrease. The more optical System-on-Chip (SoC) devices can go into a single wafer, the more can the price of each SoC decrease.

Researchers at the Technical University of Eindhoven and the JePPIX consortium have done some modelling to show how this economy of scale principle would apply to photonics. If production volumes can increase from a few thousands of chips per year to a few millions, the price per optical chip can decrease from thousands of Euros to mere tens of Euros. This must be the goal for LIDAR and automotive industry.

Figure 3: Modelling of photonic integrated chip (PIC) cost as a function of aggregate number of PICs produced per year. Exponential increases in production lead to an exponential decrease in cost. Source: Model and graph provided by Prof. Meint Smit, TU Eindhoven.

By integrating all optical components on a single chip, we also shift the complexity from the assembly process to the much more efficient and scalable semiconductor wafer process. Assembling and packaging a device by interconnecting multiple photonic chips increases assembly complexity and costs. On the other hand, combining and aligning optical components on a wafer at a high volume is much easier, which drives down the device’s cost.

Using Proven Photonics Technologies for Automotive Standards

Another challenge for photonics technologies is that they need to move from into parameters and specifications in the automotive sector that are often harsher than the telecom/datacom sector. For example, a target temperature range of −40°C to 125°C is often required, which is much broader than the typical industrial temperature range used in the telecom sector. The packaging of the PIC and its coupling to fiber and free space is particularly sensitive to these temperature changes.

Temperature Standard	Temperature Range (°C)
Temperature Standard	Min	Max
Commercial (C-temp)	0	70
Extended (E-temp)	-20	85
Industrial (I-temp)	-40	85
Automotive / Full Military	-40	125

Table 1: Comparing the temperature ranges of different temperature hardening standards, including industrial and automotive/full military applications

Fortunately, a substantial body of knowledge already exists to make integrated photonics compatible with harsh environments like those of outer space. After all, photonic integrated circuits (PICs) use similar materials to their electronic counterparts, which have already been qualified for space and automotive applications. Commercial solutions, such as those offered by PHIX Photonics Assembly, Technobis IPS, and the PIXAPP Photonic Packaging Pilot Line, are now available.

Takeaways

Photonics technology must be built on a wafer-scale process that can produce millions of chips in a month. When we can show the market that photonics can be as easy to use as electronics, that will trigger a revolution in the use of photonics worldwide.

The broader availability of photonic devices will take photonics into new applications, such as those of LIDAR and the automotive sector. With a growing integrated photonics industry, LIDAR can become lighter, avoid moving parts, and be manufactured in much larger volumes that reduce the cost of LIDAR devices. Integrated photonics is the avenue for LIDAR to become more accessible to everyone.

Tags: accessible, affordable, automotive, automotive sector, beamforming, discrete, economics of scale, efficient, electronics, laser, LIDAR, phased arrays, photonic integration, power consumption, self-driving car, self-driving cars, space, wafer

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