Photonic integrated circuit

A photonic integrated circuit (PIC) or integrated optical circuit is a microchip containing two or more photonic components that form a functioning circuit. This technology detects, generates, transports, and processes light. Photonic integrated circuits use photons (or particles of light) as opposed to electrons that are used by electronic integrated circuits. The major difference between the two is that a photonic integrated circuit provides functions for information signals imposed on optical wavelengths typically in the visible spectrum or near-infrared (850–1650 nm).

One of the most commercially utilized material platforms for photonic integrated circuits is indium phosphide (InP), which allows for the integration of various optically active and passive functions on the same chip. Initial examples of photonic integrated circuits were simple 2-section distributed Bragg reflector (DBR) lasers, consisting of two independently controlled device sections—a gain section and a DBR mirror section. Consequently, all modern monolithic tunable lasers, widely tunable lasers, externally modulated lasers and transmitters, integrated receivers, etc. are examples of photonic integrated circuits. As of 2012, devices integrate hundreds of functions onto a single chip. ^[1] Pioneering work in this arena was performed at Bell Laboratories. The most notable academic centers of excellence of photonic integrated circuits in InP are the University of California at Santa Barbara, USA, the Eindhoven University of Technology, and the University of Twente in the Netherlands.

A 2005 development ^[2] showed that silicon can, even though it is an indirect bandgap material, still be used to generate laser light via the Raman nonlinearity. Such lasers are not electrically driven but optically driven and therefore still necessitate a further optical pump laser source.

History

Photonics is the science behind the detection, generation, and manipulation of photons. According to quantum mechanics and the concept of wave–particle duality first proposed by Albert Einstein in 1905, light acts as both an electromagnetic wave and a particle. For example, total internal reflection in an optical fibre allows it to act as a waveguide.

Integrated circuits using electrical components were first developed in the late 1940s and early 1950s, but it took until 1958 for them to become commercially available. When the laser and laser diode were invented in the 1960s, the term "photonics" fell into more common usage to describe the application of light to replace applications previously achieved through the use of electronics.

By the 1980s, photonics gained traction through its role in fibre optic communication. At the start of the decade, an assistant in a new research group at Delft University Of Technology, Meint Smit, started pioneering in the field of integrated photonics. He is credited with inventing the Arrayed Waveguide Grating (AWG), a core component of modern digital connections for the Internet and phones. Smit has received several awards, including an ERC Advanced Grant, a Rank Prize for Optoelectronics and a LEOS Technical Achievement Award. ^[3]

In October 2022, during an experiment held at the Technical University of Denmark in Copenhagen, a photonic chip transmitted 1.84 petabits per second of data over a fibre-optic cable more than 7.9 kilometres long. First, the data stream was split into 37 sections, each of which was sent down a separate core of the fibre-optic cable. Next, each of these channels was split into 223 parts corresponding to equidistant spikes of light across the spectrum. ^[4]

Comparison to electronic integration

Unlike electronic integration where silicon is the dominant material, system photonic integrated circuits have been fabricated from a variety of material systems, including electro-optic crystals such as lithium niobate, silica on silicon, silicon on insulator, various polymers, and semiconductor materials which are used to make semiconductor lasers such as GaAs and InP. The different material systems are used because they each provide different advantages and limitations depending on the function to be integrated. For instance, silica (silicon dioxide) based PICs have very desirable properties for passive photonic circuits such as AWGs (see below) due to their comparatively low losses and low thermal sensitivity, GaAs or InP based PICs allow the direct integration of light sources and Silicon PICs enable co-integration of the photonics with transistor based electronics. ^[5]

The fabrication techniques are similar to those used in electronic integrated circuits in which photolithography is used to pattern wafers for etching and material deposition. Unlike electronics where the primary device is the transistor, there is no single dominant device. The range of devices required on a chip includes low loss interconnect waveguides, power splitters, optical amplifiers, optical modulators, filters, lasers and detectors. These devices require a variety of different materials and fabrication techniques making it difficult to realize all of them on a single chip.^{[ citation needed ]}

Newer techniques using resonant photonic interferometry is making way for UV LEDs to be used for optical computing requirements with much cheaper costs leading the way to petahertz consumer electronics.^{[ citation needed ]}

Examples of photonic integrated circuits

The primary application for photonic integrated circuits is in the area of fiber-optic communication though applications in other fields such as biomedical ^[6] and photonic computing are also possible.

The arrayed waveguide gratings (AWGs) which are commonly used as optical (de)multiplexers in wavelength division multiplexed (WDM) fiber-optic communication systems are an example of a photonic integrated circuit which has replaced previous multiplexing schemes which utilized multiple discrete filter elements. Since separating optical modes is a need for quantum computing, this technology may be helpful to miniaturize quantum computers (see linear optical quantum computing).

Another example of a photonic integrated chip in wide use today in fiber-optic communication systems is the externally modulated laser (EML) which combines a distributed feed back laser diode with an electro-absorption modulator ^[7] on a single InP based chip.

Applications

Photonic chips are used for sensors, such as Lidar, diagnostic sensors for healthcare, instruments on satellites, in telecommunications for fibre-optic communication, among other things. ^[8]

Data and telecommunications

The primary application for PICs is in the area of fibre-optic communication. The arrayed waveguide grating (AWG) which are commonly used as optical (de)multiplexers in wavelength division multiplexed (WDM) fibre-optic communication systems are an example of a photonic integrated circuit. ^[9] Another example in fibre-optic communication systems is the externally modulated laser (EML) which combines a distributed feedback laser diode with an electro-absorption modulator.

The PICs can also increase bandwidth and data transfer speeds by deploying few-modes optical planar waveguides. Especially, if modes can be easily converted from conventional single-mode planar waveguides into few-mode waveguides, and selectively excite the desired modes. For example, a bidirectional spatial mode slicer and combiner ^[10] can be used to achieve the desired higher or lower-order modes. Its principle of operation depends on cascading stages of V-shape and/ or M-shape graded-index planar waveguides.

PICs also reduce energy consumption in data centres. ^[11] Researchers at Columbia Engineering integrated optical elements into computing chips, decreasing the amount of energy and space required for data transfer in interconnected systems. Their system had a bandwidth of 800 Gb/s and a density of 5.3 Tb/s/mm². ^[12]

Healthcare and medicine

PICs are being developed for use as biosensors in medicine to provide faster tests and imaging for radiation therapy. ^[13] Amazec Photonics has developed a photonic sensor which enables external temperature sensing with sub-millikelvin precision. ^[14] This increase in precision allows medical specialists to better measure cardiac output and circulating blood volume to monitor for heart disease. Optical sensors are also used in EFI's Optirip device, which offers greater tissue feeling for minimally invasive surgery. ^[15]

Automotive and engineering applications

PICs are used in LiDAR sensor systems to monitor vehicles' surroundings. Fiber Bragg grating sensors can be used to sense pressure, temperature, vibrations, accelerations, and mechanical strain. ^{[16] [17]}

Agriculture and food

Sensors play a role in innovations in agriculture and the food industry in order to reduce wastage and detect diseases. ^[18] Light sensing technology powered by PICs can sense non-visible light, allowing detection of disease, ripeness and nutrients in fruit and plants. It can also help food producers to determine soil quality and plant growth. It can also measure CO₂ emissions. Near-infrared spectromoters have been miniaturized and can be used to analyse products such as milk and plastics. ^[19]

Types of fabrication and materials

The fabrication techniques are similar to those used in electronic integrated circuits, in which photolithography is used to pattern wafers for etching and material deposition.

The platforms considered most versatile are indium phosphide (InP) and silicon photonics (SiPh):

• Indium phosphide (InP) PICs have active laser generation, amplification, control, and detection. This makes them an ideal component for communication and sensing applications.
• Silicon nitride (SiN) PICs have a vast spectral range and ultra low-loss waveguide. This makes them highly suited to detectors, spectrometers, biosensors, and quantum computers. The lowest propagation losses reported in SiN (0.1 dB/cm down to 0.1 dB/m) have been achieved by LioniX International's TriPleX waveguides.
• Silicon photonics (SiPh) PICs provide low losses for passive components like waveguides and can be used in minuscule photonic circuits. They are compatible with existing electronic fabrication.

The term "silicon photonics" actually refers to the technology rather than the material. It combines high density photonic integrated circuits (PICs) with complementary metal oxide semiconductor (CMOS) electronics fabrication. The most technologically mature and commercially used platform is silicon on insulator (SOI).

Other platforms include:

• Lithium niobate (LiNbO₃) is an ideal modulator for low loss mode. It is highly effective at matching fibre input–output due to its low index and broad transparency window. For more complex PICs, lithium niobate can be formed into large crystals. As part of project ELENA, there is a European initiative to stimulate production of LiNbO₃-PICs. Attempts are also being made to develop lithium niobate on insulator (LNOI).
• Silica has a low weight and small form factor. It is a common component of optical communication networks, such as planar light wave circuits (PLCs).
• Gallium arsenide (GaAS) has high electron mobility. This means GaAS transistors operate at high speeds, making them ideal analogue integrated circuit drivers for high speed lasers and modulators.

By combining and configuring different chip types (including existing electronic chips) in a hybrid or heterogeneous integration, it is possible to leverage the strengths of each. Taking this complementary approach to integration addresses the demand for increasingly sophisticated energy-efficient solutions.

Current status

As of 2010, photonic integration was an active topic in U.S. Defense contracts. ^{[20] [21]} It was included by the Optical Internetworking Forum for inclusion in 100 gigahertz optical networking standards. ^[22] A recent study presents a novel two-dimensional photonic crystal design for electro-reflective modulators, offering reduced size and enhanced efficiency compared to traditional bulky structures. This design achieves high optical transmission ratios with precise angle control, addressing critical challenges in miniaturizing optoelectronic devices for improved performance in PICs. In this structure, both lateral and vertical fabrication technologies are combined, introducing a novel approach that merges two-dimensional designs ^[23] with three-dimensional structures. This hybrid technique offers new possibilities for enhancing the functionality and integration of photonic components within photonic integrated circuits. ^[24]

See also

• Integrated quantum photonics
• Optical computing
• Optical transistor
• Silicon photonics

Notes

1. Larry Coldren; Scott Corzine; Milan Mashanovitch (2012). Diode Lasers and Photonic Integrated Circuits (Second ed.). John Wiley and Sons. ISBN   9781118148181.
2. Rong, Haisheng; Jones, Richard; Liu, Ansheng; Cohen, Oded; Hak, Dani; Fang, Alexander; Paniccia, Mario (February 2005). "A continuous-wave Raman silicon laser". Nature. 433 (7027): 725–728. Bibcode:2005Natur.433..725R. doi: 10.1038/nature03346 . PMID   15716948. S2CID   4429297.
3. "Meint Smit Named 2022 John Tyndall Award Recipient". Optica (formerly OSA). 23 November 2021. Retrieved 20 September 2022.
4. Sparkes, Matthew (October 20, 2022). "Chip can transmit all of the internet's traffic every second". Nature Photonics. 16 (11). NewScientist: 798. Bibcode:2022NaPho..16..798J. doi:10.1038/s41566-022-01082-z. S2CID   253055705 . Retrieved October 28, 2022.
5. Narasimha, Adithyaram; Analui, Behnam; Balmater, Erwin; Clark, Aaron; Gal, Thomas; Guckenberger, Drew; et al. (2008). "A 40-Gb/S QSFP Optoelectronic Transceiver in a 0.13μm CMOS Silicon-on-Insulator Technology". OFC/NFOEC 2008 - 2008 Conference on Optical Fiber Communication/National Fiber Optic Engineers Conference. p. OMK7. doi:10.1109/OFC.2008.4528356. ISBN   978-1-55752-856-8. S2CID   43850036.
6. Rank, Elisabet A.; Sentosa, Ryan; Harper, Danielle J.; Salas, Matthias; Gaugutz, Anna; Seyringer, Dana; Nevlacsil, Stefan; Maese-Novo, Alejandro; Eggeling, Moritz; Muellner, Paul; Hainberger, Rainer; Sagmeister, Martin; Kraft, Jochen; Leitgeb, Rainer A.; Drexler, Wolfgang (5 January 2021). "Toward optical coherence tomography on a chip: in vivo three-dimensional human retinal imaging using photonic integrated circuit-based arrayed waveguide gratings". Light Sci Appl. 10 (6): 6. Bibcode:2021LSA....10....6R. doi:10.1038/s41377-020-00450-0. PMC   7785745 . PMID   33402664.
7. Paschotta, Dr Rüdiger (9 May 2005). "Electroabsorption Modulators". www.rp-photonics.com.
8. PhotonDelta & AIM Photonics (2020). "IPSR-I 2020 overview" (PDF). IPSR-I: 8, 12, 14. Archived from the original (PDF) on 2022-01-20.
9. Inside Telecom Staff (30 July 2022). "How Can Photonic Chips Help to Create a Sustainable Digital Infrastructure?". Inside Telecom. Retrieved 20 September 2022.
10. Awad, Ehab (October 2018). "Bidirectional Mode Slicing and Re-Combining for Mode Conversion in Planar Waveguides". IEEE Access. 6 (1): 55937. Bibcode:2018IEEEA...655937A. doi: 10.1109/ACCESS.2018.2873278 . S2CID   53043619.
11. Verdecchia, R., Lago, P., & de Vries, C. (2021). The LEAP Technology Landscape: Lower Energy Acceleration Program (LEAP) Solutions, Adoption Factors, Impediments, Open Problems, and Scenarios.
12. Daudlin, Stuart; et al. (21 March 2025). "Three-dimensional photonic integration for ultra-low-energy, high-bandwidth interchip data links". Nature Photonics. 19 (5): 502–509. Bibcode:2025NaPho..19..502D. doi: 10.1038/s41566-025-01633-0 .
13. Boxmeer, Adrie (1 April 2022). "Geïntegreerde fotonica maakt de zorg toegankelijker en goedkoper". Innovation Origins (in Dutch). Retrieved 20 September 2022.
14. Flaherty, Nick (15 Feb 2024). "€1.5m for photonic chip heart monitor" . Retrieved 2025-12-30.
15. Oderwald, Michiel (October 2016). "The OptiGrip: A surgical instrument with feeling" (PDF). Retrieved 2025-12-30.
16. De Vries, Carol (5 July 2021). "Roadmap Integrated Photonics for Automotive" (PDF). PhotonDelta. Retrieved 20 September 2022.
17. "Technobis fotonica activiteiten op eigen benen als PhotonFirst". Link Magazine (in Dutch). 1 January 2021. Retrieved 20 September 2022.
18. Morrison, Oliver (28 March 2022). "Let there be light: Netherlands probes photonics for food security solution". Food Navigator. Retrieved 20 September 2022.
19. Hakkel, Kaylee D.; Petruzzella, Maurangelo; Ou, Fang; van Klinken, Anne; Pagliano, Francesco; Liu, Tianran; van Veldhoven, Rene P. J.; Fiore, Andrea (2022-01-10). "Integrated near-infrared spectral sensing". Nature Communications. 13 (1): 103. Bibcode:2022NatCo..13..103H. doi:10.1038/s41467-021-27662-1. ISSN   2041-1723. PMC   8748443 . PMID   35013200.
20. "Silicon-based Photonic Analog Signal Processing Engines with Reconfigurability (Si-PhASER) - Federal Business Opportunities: Opportunities". Fbo.gov. Archived from the original on May 6, 2009. Retrieved 2013-12-21.
21. "Centers in Integrated Photonics Engineering Research (CIPhER) - Federal Business Opportunities: Opportunities". Fbo.gov. Archived from the original on May 6, 2009. Retrieved 2013-12-21.
22. "CEI-28G: Paving the Way for 100 Gigabit" (PDF). Archived from the original (PDF) on 29 November 2010.
23. Khakbaz Heshmati, MohammadMahdi (2023). "Numerical investigations of 2-D optical free-form couplers for surface connections of photonic integrated circuits". Results in Optics. 10 100351. Bibcode:2023ResOp..1000351M. doi: 10.1016/j.rio.2023.100351 .
24. Khakbaz Heshmati, MohammadMahdi (2023). "Optimized Design and Simulation of Optical Section in Electro-Reflective Modulators Based on Photonic Crystals Integrated with Multi-Quantum-Well Structures". Optics. 4: 227-245. doi: 10.3390/opt4010016 .

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