MIT and DARPA Pack Lidar Sensor onto Single Chip

From this part of the article, the team seems fairly confident in their ability to integrate the laser onto the same die as the waveguides. This seems very plausible to me, given how standard this integration is in communications applications (eg fiber optic transceivers)

> Our device is a 0.5 mm x 6 mm silicon photonic chip with steerable transmitting and receiving phased arrays and on-chip germanium photodetectors. The laser itself is not part of these particular chips, but our group and others have demonstrated on-chip lasers that can be integrated in the future.

I was thinking the same thing.

Even at 2 meter range with centimeter resolution, these devices would be a much better solution to the "local obstacle" problem than ultrasonics today. Mobile platforms moving around in spaces with a lot of miscellaneous obstacles have to either be compliant (or padded) enough to just push through them or slow enough to detect them and move around them.

> Packaging is always the expensive part of optics

That's not always true, it depends on the die size. Bigger dies often means lower wafer yield for optical sensors.

So we have LIDAR on chip, and RADAR on chip. All while there is a revolution in machine learning.

OK, I'm excited.

Quanergy has yet to ship any production units. They've also been delaying for years. I have no doubt that they are building solid state lidar, but their tech isn't really "here" yet.

IANAE but I would guess that it's the same for laser light as any other EM spectrum comms, in that modulation and some kind of packet system would work in tandem with limited range. It's probably not even as hard to manage as Bluetooth or WiFi, being far more directional as it is.

I think not, because they rely on sending laser light in a specific directly, but also on receiving it from the same direction. The chances that another LIDAR system is looking at the exact same point a the exact same time is really low.

At worst it would cause some outliers that you can filter.

No, but the bigger issue may be from laser jammers[0]. Laser jammers are used to jam police speed lidars to prevent them from obtaining a reading on vehicles. Such devices are legal in most places, because the optical spectrum does not fall under the FCC's control.

[0]https://en.wikipedia.org/wiki/Laser_jammer

There are easy ways to protect a LIDAR against that, but I don't think Velodyne is doing them yet. The duty cycle is low; a ranging operation takes under 1us, and typical cycle rates are 100Hz. So each beam is live only about 1/10,000the of the time. A simple denial jammer thus needs far more power than the pulsed laser used for ranging. A simple denial jammer looks like a target at zero range, so you know you're being jammed. Note that jamming must the same color as the ranging laser; everybody has narrow-band interference filters that only pass a very narrow color band. That's why this works in sunlight.

To defeat a synchronous jammer, the LIDAR only needs to add some random variation in the transmit timing. Then the jammer won't know when to be on. With some random variation, synchronous jamming looks like noise, rather than a solid false reading.

This new MIT system requires that the received light be in phase with the laser beam at the light coherency level. That makes it reasonably immune to anything other than a laser that can sync to a narrow light pulse. Not sure that's even possible.

Yeah, AR/VR was my first though.

Depends on the power and wavelength. 1400-2000nm is meant to be safer for retina, not sure what these lidars use

It's a feedback loop, and a very effective one. The stronger the brand is, the more credibile your article will seem. The more credibile articles, the stronger the brand becomes.

That will be a good first step. As well as better automated parking features.

$8K LIDAR? From what I can find, it sounds like Google is using a $70K LIDAR.

Yes, they do non-mechanical beam steering:

> They also have the potential to be much more robust because of the lack of moving parts, with a non-mechanical beam steering 1,000 times faster than what is currently achieved in mechanical lidar systems.

The LIDAR chips don't use visible light, but the article talks about it as a future project:

> We are also developing visible light phased arrays with applications such as Li-Fi and holography that can be seen by the human eye.

Yes, but your issues will be power output and heat.

My projector is 250 watts and has a ton of cooling due to the light source and is still not all that bright. I can't imagine how difficult it would be to cool a 250 watt light source coming from a .3mm source. Probably impossible for the foreseeable future.

Maybe microfluidic tubes would make it work. But then you have to have watercooling.

It really dependson efficiency. Which I dont recall reading about in the ardicle. Or wait, did they say -6db loss I think? That would still be a ton of heat.

Either way, I don't think this will be the breakthrough we need. Lenses are one of the cheaper components in a projector.

It's still limited to use in the lab, or at least indoors, short-range:

> At the moment, our on-chip lidar system can detect objects at ranges of up to 2 meters, though we hope to achieve a 10-meter range within a year. The minimum range is around 5 centimeters. We have demonstrated centimeter longitudinal resolution and expect 3-cm lateral resolution at 2 meters. There is a clear development path towards lidar on a chip technology that can reach 100 meters, with the possibility of going even farther.

I wonder what the limiting factors are -- laser power, noise, calibration?

So will everyone else.

This could literally be a game changer.

Musk keeps saying radar+cameras is enough