Laser Lighting, LiFi And LiDAR

WiFi is embedded in our lives today. The term originated about four decades ago (as a marketing ploy, designed to rhyme with the term “Hi-Fi”) and has revolutionized personal communications, internet access, social media and the Internet of Things (IoT). WiFi uses modulated radio waves for short-range wireless data communications. DSRC (dedicated short-range communications). The technology proved critical during the recent pandemic, allowing students to continue learning and many professionals to work remotely. At this point, it is a basic staple of life – like water and electricity. LiFi uses the same idea, except it uses modulated visible light rather than radio waves. It is poised to revolutionize multiple applications, a key one being V2X (Vehicle to X where X could be vehicles, traffic infrastructure, roadway lighting, etc.) communications which is a critical enabler for connected and autonomous vehicles (CAVE).

Harald Haas, a professor at the University of Strathclyde/Glasgow, gave a seminal TED talk titled “Wireless Data from Every Light Bulb” in 2011. The presentation included a physical demonstration of real-time video transmission using a visible LED-based lightbulb. He coined the term LiFi (Light Fidelity) and painted a compelling picture of how it could deliver ever-increasing data requirements using the installed base of billions of lightbulbs in public spaces and automobiles. Professor Haas discussed four key issues that traditional WiFi (using radio waves) faces – availability, efficiency, capacity and security. LiFi has the potential to solve these by orders of magnitude, using an already installed base of lighting infrastructure. Smart transportation (through the use of smart vehicles and infrastructure) can leverage these advantages to enhance safe autonomy and efficiency.

The past decade has seen an increased proliferation of LED-based lighting in homes, industries, cars and traffic infrastructure. Along with more efficient and environmentally friendly lighting, LiFi applications have also grown in aviation, healthcare, consumer electronics, defense, and industrial applications. Studies indicate a ~$6B market in 2020, growing by a factor of > 10X by 2025. Multiple players ranging from venture-funded start-ups to large players like Panasonic and Phillips Lighting are active in this area. The opportunity is compelling, especially in a world where the volume of data is exploding and accessing this data efficiently is imperative. There are challenges – fluorescent lighting needs to be replaced by LED bulbs with modulating electronics, communications infrastructure and software have to be deployed, and operability standards need to be finalized (the IEEE 802.11 bb Light Communication Standard is currently under development).

More recently, laser-based headlamps have emerged. The technology for producing high-power, white laser illumination (400-700 nm wavelength) using a combination of blue laser diodes (440-450 nm wavelength) coupled to a luminescent phosphor was developed at Soraa Laser Diodes (SLD, acquired by Kyocera in 2020, to form Kyocera SLD or KSLD). Its founders include Dr. Shuji Nakamura who won the Nobel prize in 2014. Professor Haas and John Peek (ex-CTO of Phillips Automotive Lighting) are on their advisory board. Their flagship automotive product is the LaserLight™ engine which provides high-intensity lighting to illuminate the roadway at a 650 m range (1 km is possible, but is currently constrained by regulations). These light sources have been in production since 2019 for the BMW’s Series 5 model, and more recently for the iX3 and iX4 electric SUVs.

LiFi operates by modulating the light source and integrating optical receivers in the visible wavelength that can capture photons and transform these into electrons (these wavelengths are eye-safe at high-intensity levels). The modulation is rapid, not observable by the human eye, and can occur with or without operating the illumination function of the light source. Lasers provide significant speed and capacity advantages over LEDs for LiFi and data communications. This is a game-changer for V2X communications as safety becomes paramount with increased levels of autonomous driving in cars and trucks. Figure 3 is an illustration of how LiFi could operate in an automotive environment.

According to Paul Rudy, Chief Marketing Officer of KSLD, “simulated emission (in lasers) versus spontaneous emission (in LEDs) enables higher power density and superior beam shape, with 100X higher brightness and 10X higher range”. This leads to the following key advantages of laser-based illumination (vs LEDs) for LiFi:

• 5X narrower spatial and spectral profile
• >100x faster communication and sensing (lasers can be modulated at 10 GHz vs 100 MHz for LEDs)

As increased levels of autonomy are incorporated into road vehicles and trucks (L3 and L4), the type and number of sensors required to ensure safety and efficiency increases (cameras, radars, LiDARs, IMUs, GPS, etc.). This leads to a massive explosion of data, some of which is processed with onboard computers (estimates indicate ~10 TB/hour generated from sensors on autonomous vehicles). The idea of sharing this data securely with other vehicles and fixed infrastructure (V2X) is an active area of discussion and research. DSRC (dedicated short-range communications) and cellular connectivity are already used or imminent. However, as the CAVE revolution progresses, these solutions will run out of capacity and bandwidth to support low latency information sharing. LiFi is a potential solution. The LaserLight™ used for illumination can also be used to transmit large amounts of data securely between vehicles or to traffic infrastructure-based receivers. Although laser lighting is 20-30% higher in cost than LED lighting, the added LiFi functionality can potentially help reduce the number of onboard sensors and computing resources required for autonomous operation.

Professor Haas indicates the following challenges to enabling LiFi communications for ground transportation: “Connecting vehicles at varying distances and speeds while ensuring reliable data connections (at gigabit transmission speeds) with zero cross-interference creates interesting challenges. The directionality and range of KSLD’s LaserLight™ devices allow these to be addressed effectively. At this stage, it is merely a question of adoption. To this end, inter-operability between cars and related standards will be hugely beneficial. I foresee a very bright future of LiFi in the automotive sector for V2X supporting autonomous driving and enhanced road safety. I look forward to working with KSLD to bring these innovations to the road”

Cost is a critical factor in replacing conventional halogen and LED lighting in vehicles and transportation infrastructure. Laser lighting provides significantly higher performance, but it will be at a price premium initially (20-30% higher) and not affordable for mid-range vehicles. As discussed above, bundling lighting with LiFi capabilities helps since V2X capabilities can reduce the amount of onboard sensor and compute resources. A third function is also possible in the KSLD’s LaserLight™ product. Apart from GaN-based blue lasers, the semiconductor assembly also includes a higher wavelength GaAs laser (850 nm, 905 nm or 940 nm) diode which in conjunction with a silicon detector can provide for range-finding and LiDAR imaging capabilities.

The headlamp space in a vehicle can be used for three critical functions:

1. Lighting: uses GaN laser + phosphor luminescence to create white light to deliver sharp, precise, and dynamically controlled illumination based on the road, traffic and lighting conditions
2. LiFi: a modulation circuit added to the above, along with a visible wavelength detector can provide high speed, low latency V2X communications
3. Sensing and LiDAR: uses an infrared GaAs laser and detector (9XX nm wavelength) to provide simple range information or more complex LiDAR point clouds

The bundling of three critical functions (lighting, communication and sensing) in a single headlamp assembly provides for significant gains in vehicle integration overhead (cost, space, power) and reduces overall system costs by replacing other sensors. It is difficult to quantify these savings at this stage since these depend on specific integration approaches pursued by vehicle manufacturers. But it is reasonable to conclude that the price premium for laser lighting will be more than offset by the bundling of these added functionalities.

George Lucas created the fictional Lightsabre (laser energy sword) four decades ago and it became a mainstay throughout the famous Star Wars movie franchise. Fast-forwarding to the present, products like KSLD’s LaserLight™ are an important weapon in our arsenal for solving the challenges of increased autonomy in transportation and creating secure and low latency data connectivity between cars and traffic infrastructure. May the light be with you.