<section><p><strong>In order to keep up with the growth in - mobile - data traffic, wireless signals with an increasingly shorter wavelength are required. Doctoral candidate <a href="https://research.tue.nl/en/persons/alvaro-morales-vicente" target="_blank">Álvaro Morales Vicente</a> investigated how you can generate and transmit so-called millimeter waves with the use of photonic chips.</strong></p></section><section tabindex="-1"><p>Those of us working from home who -&nbsp;out of necessity or by choice -&nbsp;have taken a closer look at their Wi-Fi network recently, will know that the router sends signals over two frequencies: 2.4 Gigahertz and 5 Gigahertz. The latter connection is faster, but also has a shorter range unfortunately, due to the shorter radio waves (6 centimeters instead of 12.5) -&nbsp;which is why an extra Wi-Fi point is sometimes needed to enhance the signal.</p><p>In order to provide everyone with ultrafast internet indoors and outdoors, to allow self-driving cars to communicate with each other, or to enable wireless data transfer within data centers, ‘data rates’ of several Gigabits per second are required. For this, even higher frequencies are needed, ranging from 30 to 300 Gigahertz, corresponding to wavelengths of a few millimeters.</p><h2>Beat</h2><p>This poses several challenges, doctoral candidate Álvaro Morales Vicente from Spain says. “Since short waves cover a smaller range, the signals need to be steered in a very specific direction over a short distance. That can be done with several antennas in a row.” In addition, generating such high frequencies with traditional electronics is no easy task in itself, Morales Vicente emphasizes. “The main problem is the limited bandwidth of the modulation that can be handled by traditional electronics, which means that you cannot achieve the desired high bit rates.”</p><p>There is an alternative: using laser light to very accurately generate the desired radio frequencies. Laser light has a much higher frequency than radio waves, but combining two laser beams with slightly different ‘colors’ leads to a periodic variation in light intensity caused by interference, Morales Vicente explains. “That difference frequency can be converted to a radio signal with the use of a light detector.” This phenomenon is comparable to the ‘beating’ you can hear when you pluck two strings of a slightly out of tune guitar.</p><p><span class="fr-img-caption fr-fic fr-dib" style="width: 788px;"><span class="fr-img-wrap"><img src="https://s3-us-west-1.amazonaws.com/wevolver-project-images/froala%2F1606906402771-csm_Sluitstuk+detailfoto+Javier+P%C3%A9rez+Santacruz_ba8a309c78.png"><span class="fr-inner">Photonic chip that steers the radiation direction of millimeter-wave radio signals for high-speed wireless communications. Foto: Javier Pérez Santacruz&nbsp;</span></span></span></p><h2>Optical Chip</h2><p>The next essential step is ‘aiming’ the millimeter waves to bring the signal from A to B. “That too works with interference. When the signal is transmitted by a row of antennas, each with a slightly different delay, the radio signal is steered in a certain direction.” Morales Vicente managed to realize this effect at different wavelengths in the lab by creating the signals on an optical chip.</p><p>Optical generation of millimeter waves is energy-efficient and flexible, but this technology is still in its infancy. “The major challenge is to combine all the necessary steps in a handy device. That includes generating a signal with the right frequency, modulating this to store data in it, and steering the millimeter waves in a specific direction to deliver said data.”</p><p>The idea is that all this can eventually be done on an optical chip, a technology in which TU/e is leading. Morales Vicente: “I still used separate lasers to generate the signals, but I have already carried out a study on how to realize this on an optical chip.”</p><hr><p><style type="text/css"></style><style type="text/css"></style><span data-sheets-userformat='{"2":769,"3":{"1":0},"11":3,"12":0}' data-sheets-value='{"1":2,"2":"This article was first published here"}'>This article was first published here:&nbsp;<a href="https://www.tue.nl/en/our-university/departments/mathematics-and-computer-science/the-department/news/news-overview/30-11-2020-radio-from-laser-light/" rel="noopener noreferrer" target="_blank">https://www.tue.nl/en/our-university/departments/mathematics-and-computer-science/the-department/news/news-overview/30-11-2020-radio-from-laser-light/</a></span></p></section>

Álvaro Morales Vicente will defend his thesis on December 7th at the department of Electrical Engineering of the TUe

Radio from laser light

<p><em>This article is sponsored by PhotonDelta, a growth accelerator for the integrated photonics industry. Its network consists out of chip designers, module companies, foundries, researchers, software developers as well end-customers. Through their sponsorship, PhotonDelta supports knowledge building and resource sharing on this topic.</em></p><h2 data-element-id="headingsMap-4-0">Introduction</h2><p>Integrated photonics is the rapidly emerging field of photonics that works to integrate multiple photonic functions into integrated circuits for communication, sensing, and, going forward, computing applications. Complex photonic circuits can now generate, process, and detect light, in analogy to how electronic integrated circuits do for electronic signals by way of connecting multiple discrete single-function components (e.g. dedicated lasers, photodetectors) and relevant optical interfaces.</p><p>As many communication and sensing applications already make use of light, solid-state integration on a Photonic Integrated Circuit (PIC) carries the promise of significant reduction of size, weight, manufacturing costs, and power consumption while improving reliability, in comparison to the assembling and packaging of multiple discrete photonics components and bulk optics.</p><p>Integrated photonics are already applied in impactful applications such as high-speed fiber-based optical communications, next-generation low-cost environmental mapping systems, and lab-on-chip biosensors for fast and accurate analysis of biological samples.</p><p>For a more comprehensive introduction to Integrated Photonics read our previous <a href="https://www.wevolver.com/article/an-introduction-to-integrated-photonics" rel="noopener noreferrer" target="_blank" id="isPasted">foundation article on the topic</a>. This article will focus on the areas PICs are being applied and how they are accelerating innovation in these sectors.</p><h3 data-element-id="headingsMap-5-0">Automotive</h3><p>The automotive industry is going through a rapid transformation driven by trends including electrification, autonomous vehicles &amp; driver support systems, and changes in mobility patterns and city infrastructure. These trends will influence not only the physical design and capability of commercial, public, and individual vehicles but also the broader social and economic impacts of changes to car/fleet ownership and use. The increased need for sensors in vehicles, in the electric/hybrid drivetrains as well as in advanced driver-assistance systems (ADAS) up to autonomous driving systems, creates new significant opportunities for the integrated photonics industry (Figure 1).</p><h3 data-element-id="headingsMap-6-0"><span class="fr-img-caption fr-fic fr-dib" style="width: 788px;"><span class="fr-img-wrap"><img src="https://images.wevolver.com/eyJidWNrZXQiOiAid2V2b2x2ZXItcHJvamVjdC1pbWFnZXMiLCAia2V5IjogImZyb2FsYS8xNjA2MjAzOTEyMTU5LUFEQVMuanBnIiwgImVkaXRzIjogeyJyZXNpemUiOiB7IndpZHRoIjogOTUwLCAiZml0IjogImNvdmVyIn19fQ=="><span class="fr-inner" spellcheck="false">Figure 1. An example of an ADAS system.&nbsp;</span></span></span>Lidar</h3><p>The role of integrated photonics in the automotive sector has so far been modest, but its potential is extensive and touches all aspects of the vehicle and system design. One promising area is in Lidar (BAD) (Light Detection And Ranging) systems, used to assist autonomous vehicles to ‘see’. Currently, these laser-based systems are extremely expensive, often costing more than tens of thousands of dollars for a single system which limits their commercial availability. Additionally, these early systems carried with them concerns about their reliability, eye safety (due to the close to visible range wavelength regions used), and limited accuracy (given the relatively simple ranging schemes possible). Integrated photonics offers the opportunity to reduce this cost and increase system safety<sup>[1]</sup>.</p><p><a href="https://news.mit.edu/2010/explained-doppler-0803#:~:text=The%20Doppler%20effect%2C%20or%20Doppler,the%20source%20approaches%20the%20observer." rel="noopener noreferrer" target="_blank" id="isPasted">The Doppler effect</a> is the term given to the phenomena of the frequency of a wave changing when its source is in motion relative to an observer. Frequency-modulated continuous-wave (FMCW) Lidar works by measuring the doppler shift coherently, preventing interference from sunlight and other lidar systems. This system design offers distance resolution but comes at the cost of low acquisition speed and requires a highly coherent, as well as precisely chirped, laser source. Researchers from the Swiss Federal Institute of Technology have <a href="https://www.nature.com/articles/s41586-020-2239-3.epdf?sharing_token=8awhPK7bY8-NhCsu_UpQ4tRgN0jAjWel9jnR3ZoTv0O5vYNz8blttgNr8QtgeZcckxVk2YwyJUrdECE9S2yFSZiDVQhFdep4yLgcTlf3Xpzj-Vh0QRmBjODOGv3VU9UN1FbfxVj2R7kdYd-x8K4xH3pscwq9ozftp_lxb0GWasRGEb14fDj258OnxyFYLYzOY9V6eWP8XstlG_lFYEbROutXTZHPaKpADZtTFsUBI-A%3D&tracking_referrer=physicsworld.com" target="_blank" id="isPasted">outlined</a> how a novel approach multiplexes a single FMCW laser using a high-quality silicon-nitride microresonator on a photonic chip.</p><p>PhotonDelta is currently developing a roadmap for integrated photonics applications for the automotive industry, with a focus on the potential of Lidar, set to be published in early 2021.&nbsp;</p><h3 data-element-id="headingsMap-7-0">Continuum-of-Care</h3><p>The traditional healthcare paradigm of focusing on diagnosis and treatment of patients only after they are seriously ill has been under growing pressure to change due to increasing costs, growing populations, and rapid demographic changes (i.e. aging). There is a growing <a href="https://www.mckinsey.com/industries/healthcare-systems-and-services/our-insights/seven-healthcare-industry-trends-to-watch-in-2020" rel="noopener noreferrer" target="_blank" id="isPasted">global trend&nbsp;</a> to approach healthcare more holistically, with a particular focus on prioritizing prevention before illness, ensuring that populations can stay healthy for as long as possible. Additionally, there is also an increased focus on rehabilitation, ensuring that former patients can rapidly and fully recover to good health using a broader approach to healthcare than just medication.</p><p>Traditionally the diagnosis and treatment of patients occur in specialized centers (i.e. clinics and hospitals). A holistic approach to health requires decentralization, i.e. shifting diagnosis and treatment closer to the patients (BAD), with the ultimate vision including remote diagnosis and treatment from people’s homes. Despite strong evidence that this approach would reduce national health costs and improve patients' prognosis while reducing hospital time and resources, there has been little movement in the national health care approach around the world. To implement a more forward-looking healthcare method, an alternative to hospital-specific medical devices must be created – and this is where Integrated Photonics can provide the answer.</p><p>Light has the relevant property that a number of its parameters may change under the effect of its interaction (e.g. reflection, refraction, scattering) with bio body tissues and fluids. Light-based sensors have already been adopted into many medical devices and they will continue to be introduced at a large scale.</p><p>Integrated Photonics offers the possibility to dramatically reduce the cost and size of hospital oriented medical devices and therefore kickstart a new approach to diagnosis and treatment. Several global companies are addressing this challenge by developing Integrated Photonic technology in two main areas: &nbsp;bio-sensing (see below) and Optical Coherent Tomography (OCT) &nbsp;which is a diagnostic method for eyes, skin, and neurology diseases. Within this emerging area, PhotonDelta is developing a roadmap for integrated photonics applications for the Continuum-of-Care, with a focus on bio-sensing, set to be published in early 2021.</p><h3 data-element-id="headingsMap-8-0">Biosensors</h3><p>Silicon Nitride PICS (SiN PICs) are optimal for the detection of biological molecules. They work in a very wide wavelength range from visible to near-infrared which means they avoid the water absorption window of water and allow fluorescence detection. This wavelength range makes it easy to combine them with a cheap laser source. SiN allows for a small bend radius which means the light-contacting waveguide can be rolled up to create a very long light path on the chip’s surface. This results in a long interaction time of the light with biomolecules that are in the vicinity of the surface making the biosensors based on SiN PICs highly sensitive. They also offer the ability for simultaneous multiplexed sensing of different target molecules by using the same body fluid (e.g. blood, saliva) – ie they can test for multiple items at once. &nbsp;A full view of how a photonic biosensor works can be accessed here. (BAD)</p><p><span class="fr-img-caption fr-fic fr-dib" style="width: 788px;"><span class="fr-img-wrap"><img src="https://images.wevolver.com/eyJidWNrZXQiOiAid2V2b2x2ZXItcHJvamVjdC1pbWFnZXMiLCAia2V5IjogImZyb2FsYS8xNjA2MjA1MTIyOTU0LVNvbGVyLWltZzEuanBnIiwgImVkaXRzIjogeyJyZXNpemUiOiB7IndpZHRoIjogOTUwLCAiZml0IjogImNvdmVyIn19fQ=="><span class="fr-inner" spellcheck="false">Nanophotonic interferometric biosensor for multiplexed analysis of protein and nucleic acid biomarkers. [Dámaso Torres/ICN2]&nbsp;</span></span></span></p><p>PIC-based biosensors are expected to be applied in a multitude of areas, such as health-related targets (e.g. glucose monitoring in diabetes patients, early detection of the onset of cancer or infectious diseases), environmental applications (e.g. the detection of <a href="https://en.wikipedia.org/wiki/Pesticides" target="_blank" id="isPasted">pesticides&nbsp;</a>and pollutants), and the food industry (e.g. determination of antibiotics or hormon <a href="https://en.wikipedia.org/w/index.php?title=Drug_residue&action=edit&redlink=1" target="_blank" id="isPasted">residues</a> in food, early detection of infectious diseases). Dutch-based Lionix International is developing PIC-based biosensors to develop rapid testing (BAD) for COVID-19.</p><h2 data-element-id="headingsMap-9-0">Data &amp; telecommunications</h2><p>Research indicates that the total internet demand is growing at about 40% per year. This is driven by a huge appetite for video - Netflix now takes up to 30% of the internet’s bandwidth at peak hours. Mobile access to video is becoming more widespread as are video-centred applications such as Tik-Tok. Data consumption per device is rapidly increasing. Mobile users in North America are expected to reach 48 GigaBytes (GB) per month per smartphone by the end of 2023<sup>[2]</sup>. Integrated photonics has the potential to provide significant power, space, and cost savings, and new functionality when integrated into optical communication systems. They can also increase the transmission capacity (BAD) of existing communication systems.</p><p>Dutch-based startup, <a href="https://effectphotonics.com/" rel="noopener noreferrer" target="_blank" id="isPasted">Effect Photonics&nbsp;</a>, has been developing in this field for more than a decade and their first product a 10 Gb/s DWDM tuneable optical transceiver module is now ready for market (Figure 2). The module has an autotuning feature, in which the module scans the network for what channel to use. No engineer is required to program it at installation: it’s plug-and-play and hot-pluggable. The next step is higher bandwidths, a 25Gb/s is in the works with 100 and 400/600 channels in the works too.</p><p><span class="fr-img-caption fr-fic fr-dib" style="width: 788px;"><span class="fr-img-wrap"><img src="https://images.wevolver.com/eyJidWNrZXQiOiAid2V2b2x2ZXItcHJvamVjdC1pbWFnZXMiLCAia2V5IjogImZyb2FsYS8xNjA2MjA0Mjc3MzY4LUVmZmVjdC1QaG90b25pY3MtVUstOTQtd2ViLXJlYWR5LmpwZyIsICJlZGl0cyI6IHsicmVzaXplIjogeyJ3aWR0aCI6IDk1MCwgImZpdCI6ICJjb3ZlciJ9fX0="><span class="fr-inner" spellcheck="false">Figure 2: A tuneable optical transceiver module.</span></span></span></p><h2 data-element-id="headingsMap-10-0">Advanced components for 6G networks</h2><p>Photonic technology will play a key role in 6G networks across different segments. In 6G transport, it has the potential to allow the transmission and routing of large amounts of data traffic at an acceptable cost. In data centers, photonic interconnect and switching will introduce a new architecture that can reduce energy consumption while providing a high level of flexibility in resource utilization. There is also promising research into photonic <a href="https://www.osapublishing.org/abstract.cfm?uri=OEDI-2018-OT3A.2" target="_blank" id="isPasted">beam-forming networks&nbsp;</a> based on packaged integrated photonic circuits. Additionally, integrated photonics may be able to help achieve some functions of future radio systems that will enable further evolution towards the 6th generation of mobile networks.</p><h3 data-element-id="headingsMap-11-0">Quantum Computing</h3><p>Quantum computers based on photons instead of electrons have many advantages. A key advantage is the ability for the computer to operate at room temperature A classic quantum computer needs to be maintained at temperatures well below freezing for optimal performance making their storage and maintenance extremely costly and fragile.</p><p>Earlier this year Canadian based startup, Xanadu announced the release of the world's first publicly available photonic quantum computing platform. Applicants can access 8, 12, and soon 24 qubit machines over the cloud. Despite this historic breakthrough, the potential of photonic quantum computing has not even begun to be tapped.</p><h3 data-element-id="headingsMap-12-0">More applications to come</h3><p>Other application domains and market segments for Integrated Photonics are expected to mature within 5-10 years. These include fiber-based sensor systems for real-time, and highly accurate distributed structural health monitoring, applications in energy grids and wind turbines, defense and aerospace applications as well as in monitoring systems for highly critical structures such as dikes and bridges. &nbsp;Another exciting area is NIR spectral sensing modules and components for analysis of fruit and vegetable nutrients, taste, and structure insights, which will meet increasing global concerns about food safety, storage, and traceability. Selected Integrated Photonics applications will be addressed in future articles.</p><h2 data-element-id="headingsMap-13-0">Conclusion</h2><p>Integrated Photonics is a rapidly emerging technology and industry which offers a dramatic reduction of costs and size for many communications and sensing components. As such offering huge potential to enable disruptive innovative products and solutions across industries and applications. Integrated Photonics is growing rapidly into one of the defining technologies of our time. &nbsp;</p><hr><h2 data-element-id="headingsMap-14-0"><em>About the sponsor: PhotonDelta</em></h2><p><em><a href="https://www.photondelta.com/" rel="noopener noreferrer" target="_blank" id="isPasted">PhotonDelta&nbsp;</a> is a growth accelerator for the Dutch integrated photonics industry. Its objective is to promote the adoption of integrated photonics and support companies to get prioritized access to the Dutch Integrated Photonics supply chain. Furthermore, PhotonDelta runs a new business creation program that provides companies, ranging from startups to SMEs and big organizations, with access to strategy, market, and funds.</em></p><p><em>Through its wide network within the industry, PhotonDelta has gathered insights on market trends, challenges, and product roadmaps. This information is used to drive business creation, investments, and strategic technology roadmaps. Furthermore, PhotonDelta actively supports start-ups and SMEs to facilitate their involvement with the Dutch integrated photonic supply chain. This includes facilitating options for establishing a solid presence in the Netherlands.</em></p><h1><em><img class="fr-fic fr-dib" src="https://images.wevolver.com/eyJidWNrZXQiOiAid2V2b2x2ZXItcHJvamVjdC1pbWFnZXMiLCAia2V5IjogImZyb2FsYS8xNjA2MjAzNDcwNjM2LXBob3RvbiBkZWx0YSBhcnRpY2xlIGJvdHRvbSBiYW5uZXIuanBnIiwgImVkaXRzIjogeyJyZXNpemUiOiB7IndpZHRoIjogOTUwLCAiZml0IjogImNvdmVyIn19fQ==" style="width: 788px;"></em></h1><h2 data-element-id="headingsMap-16-0"><em>References</em></h2><ol start="1" type="1"><li><a href="https://www.photonics.com/Articles/Integrated_Photonics_Looks_to_Advance_Safety_for/a64791" target="_blank" id="isPasted">https://www.photonics.com/Articles/Integrated_Photonics_Looks_to_Advance_Safety_for/a64791</a></li></ol><ol start="2" type="1"><li>ERICSSON Mobility Report November 2017, Mobile data traffic growth outlook. [Online] Available at: https://www.ericsson.com/en/ mobility-report/reports/november2017/mobile-data-traffic-growth-outlook</li></ol>

Article 2 of our Integrated Photonics series: Integrated Photonics is enabling innovation in a broad and expanding list of applications.

Key Application Areas for Integrated Photonics

<p><em>This is the first article in a series dedicated to integrated photonics. In this article, we introduce you to the technology, its history, and its materiality.&nbsp;</em></p><h2>What is integrated photonics?</h2><p>Integrated Photonics (IP) is the use of light for applications traditionally tackled by electronics. It can be used in a wide range of areas including telecommunications such as 5G networks, biosensors for speeding up medical diagnosis, and in automotive where it is used in LiDAR. IP consists of integrating multiple photonic functions on a Photonic Integrated Circuit (PIC) fabricated using automated wafer-scale generic integration technology over silicon, silica, or Indium Phosphide (InP) substrates. Integrated photonics dramatically improves the performance and reliability of these photonic functions while simultaneously reducing the size, weight, and power consumption.</p><h2>Electronics versus Photonics</h2><p>A good introduction to IP is by understanding its similarities and differences with traditional electronic circuits. Where electronics deal with the control of electrons on a chip, photonics does the same with photons. Photons are the fundamental particles of light.</p><p>Conventional integrated circuits (ICs) conduct electricity by allowing the flow of electrons through the circuit. Electrons are negatively charged subatomic particles that interact with both other electrons and other particles. These interactions slow electrons down as they move through circuits, this limits the amount of information that can be transmitted; it also generates heat, which in turn causes energy and information losses.</p><p>Photonic integrated circuits (PICs) use photons. Photons move at the speed of light with almost no interference from other photons. This greatly increases the bandwidth (the data transfer rate) and speed of the circuit, without big energy losses making PICs significantly more efficient than their IC counterparts.&nbsp;</p><p>Integrated photonic components use "waveguides", which confine and direct the light in the desired directions (by total internal reflection), much the same way as metallic wires do for electrical signals. A PIC provides functions for information signals on optical wavelengths typically in the <a href="https://en.wikipedia.org/wiki/Light#:~:text=Visible%20light%20is%20usually%20defined,%E2%80%93750%20terahertz%20(THz)." target="_blank">visible spectrum</a> or near-infrared 850 nm-1650 nm.</p><p>The elements on a PIC are connected via waveguides. The chip elements can be both passive (e.g. couplers, switches, modulators, multiplexers) and active (e,g amplifiers, detectors, and lasers). These components are integrated and fabricated onto a single substrate, which creates the compact and robust photonic device.</p><p>A key difference between electronic circuits and PICs is in the primary device that is used for fabrication. In an electronic integrated circuit, the main device is the transistor. But, in PIC, there is no particular main device that dominates in the fabrication. According to its application, the PIC will be designed with a range of fabrication devices. This integration presents opportunities to reduce current bulky, complex, and expensive optical systems in an integrated chip-scale way that has increased stability and robust operation, reduced size and power consumption, and cost-effective large-scale fabrication of even complex circuits.</p><p><img class="fr-fic fr-dib" src="https://images.wevolver.com/eyJidWNrZXQiOiAid2V2b2x2ZXItcHJvamVjdC1pbWFnZXMiLCAia2V5IjogImZyb2FsYS8xNjA1MTAzODE2MTczLXRpbWVsaW5lNS0wMS5qcGciLCAiZWRpdHMiOiB7InJlc2l6ZSI6IHsid2lkdGgiOiA5NTAsICJmaXQiOiAiY292ZXIifX19" style="width: 788px;"></p><h1>Fabrication and materials</h1><p>PICs are currently fabricated on both standard element semiconductors and compound semiconductors to dielectric materials and <a href="https://www.rp-photonics.com/nonlinear_crystal_materials.html" target="_blank">nonlinear crystal materials.</a> The specific application requirements drive the choice of the most suitable substrate material as each material has its own specific advantageous features and limitations. For example, lithium niobate can be used to fabricate low-loss waveguide devices or integrated flexible chalcogenide glass to make photonic crystals with mechanical flexibility.</p><p>The transparency and <a href="https://en.wikipedia.org/wiki/Refractive_index" target="_blank">refractive index</a> of the materials as well as their ability to directly generate light defines the properties of the finished PIC and its uses. The material's bend loss and bend radius also impact the PIC properties. Bend loss describes propagation losses (reduction in power density) in an optical fiber (or other waveguide) caused by bending while the bend radius describes the amount a fiber can bend without breaking. The major substrates today are Indium Phosphide (InP)-based monolithic integration and Silicon Photonics but Silica (SiO2 &nbsp;and Silicon Nitride (SiN) are also growing areas.</p><h2>Indium Phosphide (InP)</h2><p>Indium phosphide (InP) is the most developed platform for PICs. InP allows for the integration of both active and passive elements such as high-performance amplifiers, lasers, modulators, and detectors in combination with interferometers within one chip in the 1.1 – 1.6 μm spectral window. InP integrated photonics are used in data communications, precision metrology (for example LIDAR in autonomous vehicles), spectrometry, and imaging. </p><p>Much of the most impactful research into InP has been done in the Netherlands and several organizations and research groups continue to lead the way. The Smart Photonics foundry in Eindhoven is a leader in production services for Indium Phosphide based photonic components. The foundry and its associated services offer support for researchers and businesses to test and expand their use of InP PICs.</p><h2>Silicon Photonics (SiPh)</h2><p>Building on the success of silicon (Si) as the foundation of IC reliability, silicon photonics (SiPh) is a critical part of integrated photonics development. Silicon photonic devices can be manufactured using existing semiconductor fabrication techniques, and as silicon is already used as the substrate for most ICs, both optical and electronic components can be integrated on to the chip to create hybrid devices.</p><p>Si is <a href="https://en.wikipedia.org/wiki/Transparency_(optics)" target="_blank">transparent</a> to <a href="https://en.wikipedia.org/wiki/Infrared_light" target="_blank">infrared light</a> with wavelengths above about 1.1 micrometers (μm) &nbsp;- making it suitable for <a href="https://en.wikipedia.org/wiki/Fiber_optic_telecommunication" target="_blank">fiber optic telecommunication</a> systems which uses 1.55 micrometer <a href="https://en.wikipedia.org/wiki/Wavelength" target="_blank">wavelength</a>. It also has a very high <a href="https://en.wikipedia.org/wiki/Refractive_index" target="_blank">refractive index</a>, of about 3.5, much higher than that of silicon oxide (1.5), which allows strong confinement of light in Si structures embedded in silicon oxide (waveguides). These properties make Si well suited for usage in telecom.</p><p><span class="fr-img-caption fr-fic fr-dib" style="width: 788px;"><span class="fr-img-wrap"><img src="https://images.wevolver.com/eyJidWNrZXQiOiAid2V2b2x2ZXItcHJvamVjdC1pbWFnZXMiLCAia2V5IjogImZyb2FsYS8xNjA1MTAzODQyNjM0LUdJSlMxMjI4LUVkaXQuanBnWzc3XS5qcGciLCAiZWRpdHMiOiB7InJlc2l6ZSI6IHsid2lkdGgiOiA5NTAsICJmaXQiOiAiY292ZXIifX19"><span class="fr-inner" spellcheck="false"><span lang="EN-US">PHIX – Gijs van Ouwerkerk, courtesy of QuiX</span>&nbsp;</span></span></span></p><h2>Silicon Nitride (SiN)</h2><p>Silicon Nitride (SiN) based platforms are of recent growing interest due to their large transparency window (from visible to MIR) and ultra-low optical losses compared to other PIC platforms. Silicon nitride (SiN) excels at passive light processing in the visible, near-infrared (NIR), and IR range thanks to its very low light intensity loss in the waveguide, small bend radii, and adjustable polarization. If required by the application, active components made in another technology platform (i.e. InP) can be coupled to SiN PICs into the same package through PIC-level hybrid integration processes.</p><p>The proprietary waveguide concept, called TriPleX, from the Dutch company, <a href="https://www.lionix-international.com/" rel="noopener noreferrer" target="_blank"></a><a href="https://www.lionix-international.com/" rel="noopener noreferrer" target="_blank">Lionix International</a>, has the lowest propagation losses reported for silicon nitride waveguides (0.1 dB/cm down to 0.1 dB/m). It operates in a broad wavelength band ranging from 405 nm to 2350 nm. Furthermore, they have developed a patented tapering method that converts low contrast modes for optimal fiber coupling, to high contrast modes for small bending radii.&nbsp;</p><p>There are several large scale <a href="https://www.nwo.nl/en/research-and-results/research-projects/i/21/32421.html" target="_blank">research projects</a>  underway that are aiming to eliminate the number of current assembly steps and provide both lossless transitions between materials and a lower-cost manufacturable process.</p><h2>Lithium niobate (LiNbO3)</h2><p>Lithium niobate (LiNbO3) is a nonlinear crystal material suitable for devices performing nonlinear functions - that is functions that take advantage of this material property. A good example <a href="https://en.wikipedia.org/wiki/Electro-optic_modulator" target="_blank">electro-optic modulators</a> or acousto-optic transducers. Waveguides can be fabricated on lithium niobate substrates controlled by a lithographic method. Adding or ‘doping’ rare-earth ions to Lithium niobate makes amplifiers and lasers possible. &nbsp;LiNbO3 has the property of birefringence - which means its refractive index depends on its polarization direction. This creates opportunities for polarization control, which may then be used for filtering purposes or other similar applications. However, this property also makes it more difficult to form polarization-independent devices, which are often required for optical fiber communications.</p><h1>Innovation through collaboration</h1><p><a href="https://www.photondelta.com/" rel="noopener noreferrer" target="_blank">PhotonDelta</a>, a Dutch public-private partnership consisting of a cohesive cluster of companies and highly qualified knowledge institutes, has been formed to accelerate and reduce time to market of integrated photonics products. PhotonDelta stimulates and facilitates cooperation between stakeholders within the ecosystem providing fertile ground for developing the common business strategy, setting goals, and stimulating cooperation between partners in the Netherlands and beyond. PhotonDelta helps to amplify and scale existing companies and kickstart new ones by having access to significant funding through its industry building and growth accelerator program.</p><h1>Conclusion</h1><p>Integrated Photonics is an emerging field of technology already demonstrating massive future potential in applications across multiple fields. Much of this emerging industry developments/scale-ups and relevant R&amp;D are occurring in the Netherlands supported and driven by the leadership of PhotonDelta. PICs will continue to increase in efficiency and speed, both driving disruptive innovation, I.e. enabling (radically) new products and markers, as well as improving existing systems.</p><p>In our next article, we explore the key technology areas for Integrated Photonics. We’ll guide you through how the technology is impacting automotive, biosensors, communications, quantum computing, and data storage.</p><div align="center"><hr align="center" size="0" width="100%"></div><h1><em>About the sponsor: PhotonDelta</em></h1><p><em>PhotonDelta is a growth accelerator for the Dutch integrated photonics industry. Its objective is to promote the adoption of integrated photonics and support companies to get prioritized access to the Dutch Integrated Photonics supply chain. Furthermore, PhotonDelta runs a new business creation program that provides companies, ranging from startups to SMEs and big organizations, with access to strategy, market, and funds.</em></p><p><em>Through its wide network within the industry, PhotonDelta has gathered insights on market trends, challenges, and product roadmaps. This information is used to drive business creation, investments, and strategic technology roadmaps. Furthermore, PhotonDelta actively supports start-ups and SMEs to facilitate their involvement with the Dutch integrated photonic supply chain. This includes facilitating options for establishing a solid presence in the Netherlands.</em></p><p><em><img class="fr-fic fr-dib" src="https://images.wevolver.com/eyJidWNrZXQiOiJ3ZXZvbHZlci1wcm9qZWN0LWltYWdlcyIsImtleSI6ImZyb2FsYS8xNjA1NjEzNjc0MjkwLXBob3RvbiBkZWx0YSBhcnRpY2xlIGJvdHRvbSBiYW5uZXIuanBnIiwiZWRpdHMiOnsicmVzaXplIjp7IndpZHRoIjo5NTAsImZpdCI6ImNvdmVyIn19fQ==" style="width: 788px;"></em><br></p><p><br></p><div language="JavaScript"><div language="JavaScript"><div language="JavaScript"><div language="JavaScript"><br></div></div></div></div><p><br></p>

 PHIX – Gijs van Ouwerkerk, courtesy of QuiX

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