[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:08.14,0:00:15.13,Default,,0000,0000,0000,,It’s late, pitch dark, and a self-driving \Ncar winds down a narrow country road.
Dialogue: 0,0:00:15.13,0:00:18.72,Default,,0000,0000,0000,,Suddenly, three hazards appear \Nat the same time.
Dialogue: 0,0:00:18.72,0:00:20.85,Default,,0000,0000,0000,,What happens next?
Dialogue: 0,0:00:20.85,0:00:24.04,Default,,0000,0000,0000,,Before it can navigate this \Nonslaught of obstacles,
Dialogue: 0,0:00:24.04,0:00:26.08,Default,,0000,0000,0000,,the car has to detect them—
Dialogue: 0,0:00:26.08,0:00:29.85,Default,,0000,0000,0000,,gleaning enough information about \Ntheir size, shape, and position,
Dialogue: 0,0:00:29.85,0:00:34.21,Default,,0000,0000,0000,,so that its control algorithms \Ncan plot the safest course.
Dialogue: 0,0:00:34.21,0:00:35.76,Default,,0000,0000,0000,,With no human at the wheel,
Dialogue: 0,0:00:35.76,0:00:40.55,Default,,0000,0000,0000,,the car needs smart eyes, sensors \Nthat’ll resolve these details—
Dialogue: 0,0:00:40.55,0:00:43.90,Default,,0000,0000,0000,,no matter the environment, \Nweather, or how dark it is—
Dialogue: 0,0:00:43.90,0:00:45.92,Default,,0000,0000,0000,,all in a split-second.
Dialogue: 0,0:00:45.92,0:00:50.16,Default,,0000,0000,0000,,That’s a tall order, but there’s a \Nsolution that partners two things:
Dialogue: 0,0:00:50.16,0:00:53.85,Default,,0000,0000,0000,,a special kind of laser-based probe \Ncalled LIDAR,
Dialogue: 0,0:00:53.85,0:00:56.58,Default,,0000,0000,0000,,and a miniature version of \Nthe communications technology
Dialogue: 0,0:00:56.58,0:01:00.94,Default,,0000,0000,0000,,that keeps the internet humming,\Ncalled integrated photonics.
Dialogue: 0,0:01:00.94,0:01:06.01,Default,,0000,0000,0000,,To understand LIDAR, it helps to start \Nwith a related technology— radar.
Dialogue: 0,0:01:06.01,0:01:07.16,Default,,0000,0000,0000,,In aviation,
Dialogue: 0,0:01:07.16,0:01:11.87,Default,,0000,0000,0000,,radar antennas launch pulses \Nof radio or microwaves at planes
Dialogue: 0,0:01:11.87,0:01:16.62,Default,,0000,0000,0000,,to learn their locations by timing \Nhow long the beams take to bounce back.
Dialogue: 0,0:01:16.62,0:01:18.59,Default,,0000,0000,0000,,That’s a limited way of seeing, though,
Dialogue: 0,0:01:18.59,0:01:22.68,Default,,0000,0000,0000,,because the large beam-size \Ncan’t visualize fine details.
Dialogue: 0,0:01:22.68,0:01:26.13,Default,,0000,0000,0000,,In contrast, a self-driving car’s \NLIDAR system,
Dialogue: 0,0:01:26.13,0:01:28.63,Default,,0000,0000,0000,,which stands for Light Detection \Nand Ranging,
Dialogue: 0,0:01:28.63,0:01:32.19,Default,,0000,0000,0000,,uses a narrow invisible infrared laser.
Dialogue: 0,0:01:32.19,0:01:36.66,Default,,0000,0000,0000,,It can image features as small as the \Nbutton on a pedestrian’s shirt
Dialogue: 0,0:01:36.66,0:01:38.12,Default,,0000,0000,0000,,across the street.
Dialogue: 0,0:01:38.12,0:01:42.48,Default,,0000,0000,0000,,But how do we determine the shape, \Nor depth, of these features?
Dialogue: 0,0:01:42.48,0:01:48.27,Default,,0000,0000,0000,,LIDAR fires a train of super-short laser \Npulses to give depth resolution.
Dialogue: 0,0:01:48.27,0:01:50.75,Default,,0000,0000,0000,,Take the moose on the country road.
Dialogue: 0,0:01:50.75,0:01:55.85,Default,,0000,0000,0000,,As the car drives by, one LIDAR pulse \Nscatters off the base of its antlers,
Dialogue: 0,0:01:55.85,0:02:00.72,Default,,0000,0000,0000,,while the next may travel to the tip \Nof one antler before bouncing back.
Dialogue: 0,0:02:00.72,0:02:04.28,Default,,0000,0000,0000,,Measuring how much longer \Nthe second pulse takes to return
Dialogue: 0,0:02:04.28,0:02:06.88,Default,,0000,0000,0000,,provides data about the antler’s shape.
Dialogue: 0,0:02:06.88,0:02:13.19,Default,,0000,0000,0000,,With a lot of short pulses, a LIDAR system\Nquickly renders a detailed profile.
Dialogue: 0,0:02:13.19,0:02:18.56,Default,,0000,0000,0000,,The most obvious way to create a pulse \Nof light is to switch a laser on and off.
Dialogue: 0,0:02:18.56,0:02:23.43,Default,,0000,0000,0000,,But this makes a laser unstable and \Naffects the precise timing of its pulses,
Dialogue: 0,0:02:23.43,0:02:25.67,Default,,0000,0000,0000,,which limits depth resolution.
Dialogue: 0,0:02:25.67,0:02:27.04,Default,,0000,0000,0000,,Better to leave it on,
Dialogue: 0,0:02:27.04,0:02:33.03,Default,,0000,0000,0000,,and use something else to periodically \Nblock the light reliably and rapidly.
Dialogue: 0,0:02:33.03,0:02:35.99,Default,,0000,0000,0000,,That’s where integrated photonics come in.
Dialogue: 0,0:02:35.99,0:02:37.83,Default,,0000,0000,0000,,The digital data of the internet
Dialogue: 0,0:02:37.83,0:02:41.05,Default,,0000,0000,0000,,is carried by precision-timed \Npulses of light,
Dialogue: 0,0:02:41.05,0:02:44.47,Default,,0000,0000,0000,,some as short as a hundred picoseconds.
Dialogue: 0,0:02:44.47,0:02:49.10,Default,,0000,0000,0000,,One way to create these pulses is \Nwith a Mach-Zehnder modulator.
Dialogue: 0,0:02:49.10,0:02:52.86,Default,,0000,0000,0000,,This device takes advantage of a \Nparticular wave property,
Dialogue: 0,0:02:52.86,0:02:54.66,Default,,0000,0000,0000,,called interference.
Dialogue: 0,0:02:54.66,0:02:57.61,Default,,0000,0000,0000,,Imagine dropping pebbles into a pond:
Dialogue: 0,0:02:57.61,0:03:01.55,Default,,0000,0000,0000,,as the ripples spread and overlap, \Na pattern forms.
Dialogue: 0,0:03:01.55,0:03:05.46,Default,,0000,0000,0000,,In some places, wave peaks add \Nup to become very large;
Dialogue: 0,0:03:05.46,0:03:08.45,Default,,0000,0000,0000,,in other places, they completely \Ncancel out.
Dialogue: 0,0:03:08.45,0:03:11.52,Default,,0000,0000,0000,,The Mach-Zehnder modulator \Ndoes something similar.
Dialogue: 0,0:03:11.52,0:03:17.29,Default,,0000,0000,0000,,It splits waves of light along two \Nparallel arms and eventually rejoins them.
Dialogue: 0,0:03:17.29,0:03:20.78,Default,,0000,0000,0000,,If the light is slowed down and \Ndelayed in one arm,
Dialogue: 0,0:03:20.78,0:03:25.70,Default,,0000,0000,0000,,the waves recombine out of sync and \Ncancel, blocking the light.
Dialogue: 0,0:03:25.70,0:03:28.34,Default,,0000,0000,0000,,By toggling this delay in one arm,
Dialogue: 0,0:03:28.34,0:03:33.61,Default,,0000,0000,0000,,the modulator acts like an on/off switch, \Nemitting pulses of light.
Dialogue: 0,0:03:33.61,0:03:36.38,Default,,0000,0000,0000,,A light pulse lasting a hundred \Npicoseconds
Dialogue: 0,0:03:36.38,0:03:39.79,Default,,0000,0000,0000,,leads to a depth resolution of a \Nfew centimeters,
Dialogue: 0,0:03:39.79,0:03:43.30,Default,,0000,0000,0000,,but tomorrow’s cars will need \Nto see better than that.
Dialogue: 0,0:03:43.30,0:03:47.60,Default,,0000,0000,0000,,By pairing the modulator with a super-\Nsensitive, fast-acting light detector,
Dialogue: 0,0:03:47.60,0:03:50.88,Default,,0000,0000,0000,,the resolution can be refined \Nto a millimeter.
Dialogue: 0,0:03:50.88,0:03:52.78,Default,,0000,0000,0000,,That’s more than a hundred times better \N
Dialogue: 0,0:03:52.78,0:03:57.34,Default,,0000,0000,0000,,than what we can make out with \N20/20 vision, from across a street.
Dialogue: 0,0:03:57.34,0:04:02.92,Default,,0000,0000,0000,,The first generation of automobile LIDAR \Nhas relied on complex spinning assemblies
Dialogue: 0,0:04:02.92,0:04:05.78,Default,,0000,0000,0000,,that scan from rooftops or hoods.
Dialogue: 0,0:04:05.78,0:04:07.49,Default,,0000,0000,0000,,With integrated photonics,
Dialogue: 0,0:04:07.49,0:04:12.51,Default,,0000,0000,0000,,modulators and detectors are being shrunk \Nto less than a tenth of a millimeter,
Dialogue: 0,0:04:12.51,0:04:17.84,Default,,0000,0000,0000,,and packed into tiny chips that’ll one \Nday fit inside a car’s lights.
Dialogue: 0,0:04:17.84,0:04:21.81,Default,,0000,0000,0000,,These chips will also include a clever \Nvariation on the modulator
Dialogue: 0,0:04:21.81,0:04:27.28,Default,,0000,0000,0000,,to help do away with moving parts \Nand scan at rapid speeds.
Dialogue: 0,0:04:27.28,0:04:31.10,Default,,0000,0000,0000,,By slowing the light in a modulator \Narm only a tiny bit,
Dialogue: 0,0:04:31.10,0:04:36.21,Default,,0000,0000,0000,,this additional device will act more \Nlike a dimmer than an on/off switch.
Dialogue: 0,0:04:36.21,0:04:40.71,Default,,0000,0000,0000,,If an array of many such arms, each with \Na tiny controlled delay,
Dialogue: 0,0:04:40.71,0:04:44.79,Default,,0000,0000,0000,,is stacked in parallel, something novel \Ncan be designed:
Dialogue: 0,0:04:44.79,0:04:47.49,Default,,0000,0000,0000,,a steerable laser beam.
Dialogue: 0,0:04:47.49,0:04:48.85,Default,,0000,0000,0000,,From their new vantage,
Dialogue: 0,0:04:48.85,0:04:52.25,Default,,0000,0000,0000,,these smart eyes will probe and \Nsee more thoroughly
Dialogue: 0,0:04:52.25,0:04:54.68,Default,,0000,0000,0000,,than anything nature could’ve imagined—
Dialogue: 0,0:04:54.68,0:04:57.54,Default,,0000,0000,0000,,and help navigate any number \Nof obstacles.
Dialogue: 0,0:04:57.54,0:05:00.10,Default,,0000,0000,0000,,All without anyone breaking a sweat—
Dialogue: 0,0:05:00.10,0:05:03.99,Default,,0000,0000,0000,,except for maybe one disoriented moose.