Meet the Team: Prabhu Thiagarajan, VP Engineering, On Overcoming Technical Barriers in Lidar

     

PrabhuThiagarajan.jpgDr. Prabhu Thiagarajan, Lasertel’s VP of Engineering, is working with some of the leading automotive companies and system integrators in the market to bring the driverless vehicle to widespread adoption.

Lidar (light detection and ranging) is one of several technologies that can be used to improve the safety of autonomous vehicles, and semiconductor laser diodes (edge-emitting and vertical cavity surface-emitting, referred to as VCSEL) are the preferred technology for the illumination source in automotive lidar.

Each offers significant advantages in addressing the biggest barriers to lidar-enabled driverless vehicles today:

  • Cost
  • Supply
  • Performance

We asked him a few questions about the state of the market today.

What are you seeing take hold as the dominant diode platform for lidar?

There is no direct product today that’s fully developed for lidar. Different companies are pursuing different solutions. We have been partnering on development projects for two different laser diode platforms: edge emitters and VCSEL.

Edge emitters currently offer efficiency and reduced size—a lot more power in a given areawhile VCSEL offers cost and some performance advantages.

Edge-Emitting Laser Diodes

VCSEL Laser Diodes

Illuminate entire scenery—flash lidar

Illuminate portions of scenery

More power in greater area

Environmentally insensitive—wavelength stable in automotive with little or no temperature control

2-3x power density of VCSEL at eye-safe limits, about 1 kilometer

Imaging at 100 meters at eye-safe wavelengths

 

These are just two of many laser system approaches that you’ve been developing and testing. What have you ruled out?

I think the mechanical scanning version of lidar will be an interim solution. The mechanical movement of a source has the disadvantage of moving parts, causing a potential for reliability issues. Its sheer size presents aesthetic issues, as it is not easily integrated into existing vehicle components. Automobile manufacturers are seeking to implement a forward and backward looking lidar system that fits existing available space, in fog lights, for instance.

Lidar is not widely deployed yet, because it still faces some significant barriers. One emerging technology is using gated imaging, which is somewhere between scanning lidar and camera technology. Gated imaging flash illuminates scenery and uses a gated camera to pick out time slices. Lidar uses short laser pulses and a detector to create a 3D image of the scenery.

How do we improve the speed and range of lidar?

It comes down to resolution and range. Lidar’s range today is 200-300 meters. Gating has a range of 200 meters today. With automakers striving for 500-600 meters, both have a way to go.

Could gated imaging get there?

Yes, with higher source power. We’re seeing it used on yachts, for example, with a range of 1-2 kilometers, but there is a tradeoff in resolution. Eye-safety also becomes an issue when designing longer-range active imaging systems.

Where’s the biggest potential to increase performance of lidar systems?

The laser source is typically 30-40% of the cost of a lidar system. We’re making progress on driving up power and reducing unit cost with edge emitters by using multiple junctions within the laser structure, achieving 2-3x the power from a given laser bar, in the same real estate.

There are efficiencies possible throughout the source assembly, and we’re working through the full system design with some partners.

Is this what brought you to Lasertel?

Actually, it was my past work with Lasertel’s president, Mark McElhinney, that brought me here. After completing my Ph.D., working with 1.3 micron edge-emitter lasers, I worked with Mark setting up a telecom pump laser company, and appreciated how he approached research and manufacturing. I am also quite proud of our team at Lasertel. They’ve stepped up to challenges and delivered, with an impressive track record on projects that have stretched the boundaries in technology, challenges that most companies wouldn’t touch.

Collaborating with customers to meet their end goals is one of the main things that continues to drive my work.

Want more on lidar source technology for driverless vehicles? Download our white paper, The Race to the Starting Line: Edge-Emitting Diode Lasers vs. VCSELs for the Automotive Lidar Market.

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