Digital PhotoDiodes enable a whole new level of sensitivity to 3D sensing – An interview with ActLight

The rapid growth of the 3D sensing trend  has accelerated over the past years. For instance, the consumer market has seen a proliferation of 3D depth sensing cameras and the automotive and industrial markets have experienced increasing popularity of LiDAR. Both markets have generated many expectations regarding their evolution and future performance. One of the key elements of the 3D sensing modules is the receiver side sensor, either a PhotoDiode (PD) or PhotoDiode array, which is a semiconductor device that converts light into an electrical current based on the photoelectric effect. As detailed in Yole Développement’s (Yole) 3D Imaging & Sensing 2020” report, the 3D Sensing and Imaging market will exceed $15B by 2025. Sensor arrays will represent 39% of this market, and Yole estimates this segment will exceed $6B by 2025.

YDR20061-3D sensing and imaging - 2019-2025 market forecast (in $M)

ActLight SA, a Swiss-based startup , is commercializing a development of the traditional PhotoDiode, called a Dynamic PhotoDiode (DPD), which provides high performance sensing with immunity to a strong background light, enabling an enhanced level of performance and new applications.

Yole Développement Imaging principal analyst, Pierre Cambou talked with ActLight’s Chief Commercial Officer, Roberto Magnifico, about the company’s technology, strategy, and prospects for Dynamic PhotoDiode and related applications. Discover the details of their discussion below.

Yole Développement (YD): Could you please introduce ActLight, its history, and current activities?

Roberto Magnifico (RM): ActLight is the IP company that invented the Dynamic PhotoDiode, the breakthrough technology that is changing the game in the light-sensing market. Our company was incorporated in 2011, when we started development of technology based on the innovative idea that we can use the time delay of the forward current over the PhotoDiode to measure light in a much more precise and efficient way compared to conventional PhotoDiodes. Since 2011, we went through a series of investment rounds to grow the team and support the continuous development of our technology, inspired by the needs of markets such as smartphones, wearable devices, cars, and others.

Overtime, we started to gain traction in these markets and today we have contracts with prestigious semiconductor companies that are committed to bring our technology to market in 2021.

YD: How do you position your Dynamic PhotoDiode (DPD) with respect to regular Pin PhotoDiodes (PPD), avalanche PhotoDiodes (APD), Single Photon Avalanche PhotoDiodes (SPAD)?

RM: Overall, our DPD is a truly innovative device. Compared to regular Pin PhotoDiodes (PPD) and avalanche PhotoDiodes (APD) it has a higher signal to noise ratio (up to 90dB) thanks to the fact that the DPD does not suffer from the noise generated by the circuits needed to amplify the output current, and it is also a low voltage device (bias voltage around 1.5V). These unique characteristics make our DPD the best in class device in terms of power consumption and small size.

Compared to Single Photon Avalanche PhotoDiodes (SPAD), a device that works at high voltage, our DPD has single photon sensitivity at much lower bias voltage (1V to 2V); moreover, the sensitivity of the DPD can be adjusted by changing the bias voltage to keep measurement precision in changing ambient light conditions. This feature makes our DPD unique and suitable for 3D sensing applications such as LiDAR.

Standalone Dynamic PhotoDiode (DPD) (Courtesy of ActLight SA)

YD: Does it work for all Silicon wavelengths such as 850nm and 940nm? What about beyond Silicon, 1200nm, 1550nm and higher?

RM: Our Embedded DPD uses a standard CMOS technology and works for all Silicon wavelengths, such as 850nm and 940nm. The DPD concept can also be applied to other semiconductor materials with smaller bandgap, accommodating longer wavelengths. Our Standalone DPD uses a very simple fabrication process and can be easily manufactured by using materials other than silicon.

YD: What kind of products will use DPD and for which applications?

RM: The applicability of our IP portfolio is broad: currently, the markets that intensively engage with us are smartphones, wearable & hearable devices and cars. The range of applications goes from 3D sensing (LiDAR, fast autofocus, face recognition, etc.) to vital sign monitoring (continuous heart rate monitoring, blood oxygenation/Spo2, blood pressure, etc.). An emerging market for our DPD is quantum computing, which could be a growth engine for ActLight in the near future. 

YD: How big (physical size in mm or microns) are current designs, standalone DPD, arrays?

RM: We have a very wide range of detector sizes. The biggest being 1cm2 (stand-alone DPD) down to 13µm pitch in 180nm CMOS.
We believe the single-photon DPD can bring a big pixel-size advantage over traditional SPAD; with a pitch as small as 3µm on more advanced CMOS processes.

Embedded Dymanic PhotoDiode (DPD) – Source : ActLight SA
Embedded Dynamic PhotoDiode (DPD) (Courtesy of ActLight SA)

YD: What are the tradeoffs in designing with DPD?

RM: For healthcare applications, the superior SNR of the DPD at lower light-power can translate into either lower power consumption of the system or a smaller sensor size. The specific application dictates which of these two key parameters is given priority.
In terms of dToF 3D sensing, the DPD requires the same tradeoff between photon detection probability (PDP) and jitter as SPADS. At system level, the tunability of the sensitivity opens the door to more flexible designs with higher resolution.

YD: Timewise, what do you think will be the first products to market with DPD, and then what could be the killer application?

RM: The first product to market will be a vital-sign monitoring integrated chip for the healthcare market in 2021: the on-going pandemic has amplified and accelerated the needs for remote patient monitoring. Travel restrictions on trial patients and medical personnel as well as increased chance of infection at medical centers have reduced physical interactions, resulting in a lack of critical patient information and readily available data. This issue is addressed with the availability of performant wearable devices capable of monitoring the patient’s vital signs from a distance.

As we see the market today, the killer application is 3D sensing: mainstream products such as smartphones, light vehicles and machine vision are driving the mass implementation of this technology. The constraints of the current solutions and the complexity of the applications are challenges for the components market which is asking for increased performance and ActLight is up to the challenge with its innovative solutions.

YD: How does your company compete with the other quantum imaging players, Sony, STMicroelectronics, and Gigajot?

RM: Competition is generally great for the markets, though we prefer to see the quantum imaging players as customers or partners and work with them to add value to their technology roadmaps with innovative technologies.

Would you like to add some final words for our readers?

RM: Sure, first I would like to thank all of them for reading this interview and also I would encourage them to visit our website to obtain access to more information and stay updated on our progress.



Roberto Magnifico is ActLight’s Chief Commercial Officer (CCO) and has held this position since November 2017.
Roberto has 30+ years of experience in the components industry. He began his career in 1984 at ST Microelectronics as a product engineer and evolved his career with progressive growing commercial responsibilities with Phillips Semiconductor (NXP) and, later, managing as Vice President the growth of the European business at Intersil. More recently, in the positions of Vice President Sales & Marketing, he helped Swiss industrial groups such as Cicor Technologies and Fischer Connectors to expand their business globally.
Roberto Magnifico was born in Milano – Italy, has an electronic engineering background and graduated with an EMBA master from the IMD business school in Lausanne, Switzerland.


Pierre Cambou, Yole Développement

Pierre Cambou MSc, MBA, is a Principal analyst in the Photonic and Display Division at Yole Développement (Yole).
Pierre’s mission is dedicated to imaging related activities by providing market & technology analyses along with strategy consulting services to semiconductor companies. He is responsible for the CIS Quarterly Market Monitor while he has authored more than 15 Yole Market & Technology reports.
He has been deeply involved in the design of early mobile camera modules and the introduction of 3D semiconductor approaches to CMOS Image Sensors (CIS).
Known as an expert in the imaging industry, he is regularly interviewed and quoted by leading international media.
Pierre has an Engineering degree from Université de Technologie de Compiègne (France) and a Master of Science from Virginia Tech. (VA, USA), Pierre also graduated with an MBA from Grenoble Ecole de Management (France).

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