VCSEL Evolution: From Invention to Consumer Applications

Name: The Little Vertical Laser That Everyone Uses
Uploaded: 2026-05-17T23:00:23+00:00
Duration: 18 min 46 s
Channel: Asianometry
Description: Summary and key takeaways on The Little Vertical Laser That Everyone Uses — Summary, covering The Physics of Lasers A laser needs an optical cavity formed by

Asianometry

May 17, 2026

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18 min video

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YouTube video ID: XSNuyDA4800

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A laser needs an optical cavity formed by two mirrors and an active gain medium, which may be solid, gas, liquid, or semiconductor. Energy pumping—either electrical or optical—excites the medium, causing light to amplify as it bounces between the mirrors. Traditional edge‑emitting lasers fire horizontally from the wafer’s edge after a manual cleaving step that creates individual chips.

The Invention of the Surface‑Emitting Laser

Kenichi Iga of the Tokyo Institute of Technology sketched the vertical‑firing laser concept on March 22 1977. By emitting light perpendicular to the wafer surface, the design enables monolithic wafer‑scale fabrication and removes the need for surgical‑knife cleaving. Surface‑emitting lasers generate a circular beam, which couples more easily to optical fibers than the elliptical beams of edge‑emitters. Iga’s team later demonstrated a non‑practical surface‑emitting laser in 1979 at an operating temperature of 77 K.

Technical Challenges and Solutions

Early VCSELs suffered from high threshold currents, excessive heat, and low efficiency. Engineers reduced the optical cavity length and introduced high‑reflectivity Bragg reflectors that exceed 99 % reflectance, lowering the threshold current and improving wall‑plug efficiency. In 1989, Iga’s group and Jack Jewell’s team at Bell Labs announced the first continuous‑wave, room‑temperature VCSELs, marking a turning point for the technology.

Commercialization and Market Applications

Gigabit Ethernet became the first major driver for VCSEL adoption, offering cost and reliability benefits over edge‑emitters. The technology then migrated to consumer electronics. Optical mice replaced LEDs with VCSELs, gaining higher intensity and better focus for tracking on difficult surfaces. In 3D sensing, VCSEL arrays enable Structured Light—projecting dot patterns to infer depth—and Time‑of‑Flight measurements that calculate distance from round‑trip light travel time. These methods power gesture recognition in devices like the Xbox Kinect and facial recognition in Apple’s Face ID, introduced with the iPhone X in 2017. Today, VCSELs compete with edge‑emitters in automotive Lidar, leveraging their scalable wafer fabrication and lower per‑unit cost.

Takeaways

Kenichi Iga’s 1977 vertical‑firing laser concept enabled monolithic wafer fabrication and eliminated manual cleaving.
Shrinking the cavity and adding high‑reflectivity Bragg reflectors lowered threshold currents, leading to the first continuous‑wave, room‑temperature VCSELs in 1989.
The circular beam of surface‑emitting lasers simplifies fiber coupling, driving adoption in Gigabit Ethernet and later in optical mice and 3D sensing.
Structured Light and Time‑of‑Flight techniques use VCSEL arrays to project patterns or measure light travel time, enabling gesture and facial recognition technologies.
VCSELs now challenge edge‑emitters in automotive Lidar, thanks to their wafer‑scale scalability and cost advantages.

Frequently Asked Questions

How did Bragg reflectors improve VCSEL performance?

Bragg reflectors increase the reflectivity of the VCSEL’s mirrors to over 99%, reducing the threshold current needed for lasing and boosting wall‑plug efficiency. By stacking alternating high‑ and low‑index layers, they create a highly reflective cavity without adding loss, which was essential for achieving continuous‑wave operation at room temperature in 1989.

Why did VCSELs replace LEDs in optical mice?

VCSELs emit a focused, circular beam that provides higher intensity and better contrast on varied surfaces than the broad LED light used previously, allowing optical mice to track accurately on glossy or textured materials. Their low power consumption and ease of integration also made them suitable for high‑end mouse designs.

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Helpful resources related to this video

If you want to practice or explore the concepts discussed in the video, these commonly used tools may help.

Introductory Textbook On Laser Physics Recommended

Provides foundational knowledge on optical cavities and gain mediums, helping the reader understand the physics behind VCSEL technology.

Amazon →

High Precision Digital Optical Mouse

Uses VCSEL or advanced LED technology for surface tracking, allowing the user to experience the practical application of the technology discussed.

Amazon →

Semiconductor Physics And Devices Textbook

Explains the manufacturing and material science of semiconductors, which is essential for understanding how VCSELs are fabricated on wafers.

Amazon →

Laser Optics Experiment Kit

Allows for hands-on exploration of light reflection, mirrors, and beam manipulation, mirroring the concepts of optical cavities.

Amazon →

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Full Transcript YouTube

For the first few decades of its existence,  
all lasers were side-firing lasers - meaning the 
beam comes out of the wafer's side. Horizontally.
But in the late 1970s, a new type 
of semiconductor laser emerged.  
One that fired out of the wafer surface, 
vertically. Yes. It sounds a bit weird.
At first, nobody had any idea 
what to do with it. But over time,  
the technology has been adopted into a 
wide variety of everyday applications.
Today, it literally shines into 
people's faces. In today’s video,  
the little vertical lasers that everyone uses.
## Beginnings
The concept of a laser involves light bouncing 
between two mirrors facing one another.
One of the mirrors is fully 
reflective. The other just  
partially so. We call the space between 
these two mirrors the optical cavity.
The laser must also have an active or gain 
medium. It is made from any material capable  
of producing and amplifying light: Solids, 
gases, liquids, or semiconductor material.
To get the laser working, we pump energy into 
the gain medium - either using electricity or  
another light. It generates light. 
And when light passes through it,  
it can add yet more light: Amplification.
So the laser light bounces back 
and forth between the two mirrors,  
amplifying because of the gain medium. 
At some point, the light gets strong  
enough to burst through the partially 
reflective mirror out towards the target.
With a side-firing laser, the light bounces back  
and forth inside the optical cavity in 
a horizontal direction - accumulating  
gain. Then when the laser fires, 
it fires out the wafer's edge.
## Iga and the Laser
Japan. Tokyo Institute of Technology.
A graduate student named Kenichi Iga is 
looking for a topic for a graduation thesis.
He applies to do laser research under the 
legendary professor Yasuharu Suematsu - who  
would go on to do pioneering work 
in the field of fiber optics.
For his masters thesis project, Suematsu 
suggested to Iga to rebuild Ted Maiman's  
first practical laser - which used a ruby crystal 
as the gain medium, energized by a flash lamp.
In the autumn of 1962, Iga replicates 
the paper using a ruby crystal borrowed  
from a colleague. It worked, and he 
fell in love with laser technology.
The laser that Iga built was what we 
call a multi-mode laser. This means  
that the laser emits multiple 
modes or colors. By contrast,  
a single-mode laser would be a laser 
that emits just one pure color.
Because the laser had multiple modes, the 
beam it shot out was messy and scattered.  
Iga with Suematsu's help intuited that 
this was because the laser was bouncing  
light in too many directions 
inside the ruby crystal medium.
So to make it so that the laser 
bounces fewer modes of light,  
Iga reduced the physical size of 
one of the mirrors in the laser.  
This blocked the messy light and let 
the laser output a much tighter beam.
They wrote up the result and it 
got published. Which in those days,  
was still a rare achievement for a Japanese.
By the way, before we continue, I want 
to flag the book "the VCSEL Odyssey"  
as a fascinating chronicle of the VCSEL's 
invention. Written in part by Iga himself,  
it features interesting anecdotes from 
the start of the optical revolution.
## Making Semiconductor Lasers
A decade later, Iga is now an associate professor 
at the Institute, studying semiconductor lasers.
Industry interest in such lasers was growing. 
In 1966, Charles Kao proposed that extremely  
pure optical fibers can carry light signals 
a very long way with relatively little loss.
Additional work on the nature of glass 
fibers in 1973 by the American company  
Corning predicted that wavelengths between 1.4 and  
1.7 micrometers would have the fewest 
losses when sent through silica fibers.
With regards to long distance telecom, 
it was important that the lasers firing  
signals into these optical fibers be able 
to consistently fire at a single wavelength.  
Different light wavelengths travel at 
different speeds through optical fiber.
So for a multi-mode laser sending signals through 
a long-distance fiber, there was the risk of the  
different modes arriving at the destination 
at different times - causing annoying mixups.
Yasuharu Suematsu identified Indium gallium 
arsenide phosphide as a promising material  
to make these semiconductor 
single-mode lasers. But can  
such a bulky, four-element compound 
be reliable enough for extended use?
Iga worked in Suematsu's laboratory,  
trying to produce the crystal growth 
system for such a laser. While doing so,  
he started to ponder whether there was 
a better way to manufacture these items.
## The Cleave
As I mentioned, all lasers in those 
days were edge-emitting lasers.
So the light inside the optical cavity bounces 
left and right in a horizontal direction and  
fires out of the laser's edge. In practice, this 
optical cavity consists of a small laser chip.
Back in those days, you produced these laser 
chips using a complex multi-step process.  
First, you deposited layers of a 
desired semiconductor material like  
Indium gallium arsenide phosphide onto a wafer.
After two steps called 
patterning and metallization,  
we then cleave the wafer along 
a specific crystal plane to get  
strips of semiconductor material 
like as if we are making pasta.
In the early days, this cleaving had 
to be done with a surgical knife and  
a little nerve - presumably granted by 
a swig of Suntory whisky. The cleaved  
strips are then diced into laser chips 
of the right size using a diamond saw.
Iga was frustrated by this extremely 
manual production method. There was no  
way that it can scale to millions of units. 
Variations in the cleaving make the laser's  
performance inconsistent - causing the 
laser to fire additional, unwanted modes.
Considering how small these chips can get,  
this was a significant manufacturing challenge. 
For some laser designs and modes, the length of  
the cavity - and thus the size of the laser 
chips - must be as small as 50 micrometers.
What sort of laser design can get you single mode, 
and be consistent and reliable with that single  
mode ... while also being manufacturable at scale? 
Existing designs did not seem capable of it.
## The Surface Emitting Laser
Iga writes that the idea for 
a vertical-firing laser first  
came to him in a midnight dream on March 22, 1977.
As soon as the idea appeared, he sketched 
it down into a research note. The next day,  
he immediately began working on the design  
idea - recognizing that it fulfilled all 
the requirements that he wanted to solve.
The idea was exceedingly simple: A single-mode 
laser firing vertically from the surface of the  
wafer, rather than its edge. The concept is the 
same, just turned on its side. The gain builds  
up and down vertically rather than horizontally 
between two mirrors inside an ultra-short cavity.
We can manufacture this laser monolithically in a  
fab by carefully depositing layers of 
semiconductor materials to create your  
gain medium and the two mirrors. No more 
cleaving crystals with a knife by hand!
There were other benefits. Side-firing 
lasers have a rectangular exit window.  
So when the laser beam fires through it, 
it comes out asymmetrical - an oval-ish,  
elliptical shaped beam that 
can be challenging to focus.
This surface-firing laser on the other hand 
can fire a beam that is perfectly circular,  
making it easy to either focus using 
lenses or couple to an optical fiber.
Iga decided to first announce the idea at 
a conference to gauge people's interest.  
So in March 1978, he first presented it at 
the 25th Spring Meeting of Applied Physics  
Societies in Japan. Iga recalled 
people saying that the idea was  
interesting but the feasibility 
unlikely, especially in industry.
The thing would eventually be called 
the Vertical Cavity Surface Emitting  
Laser (VCSEL, pronounced like 
"vixel"). But that name was  
coined in the late 1980s. For now, Iga 
called them "surface emitting lasers".
Iga and his team demonstrated a non-practical 
surface-emitting laser concept in 1979.  
The laser's active medium was Gallium 
Indium Arsenide Phosphide deposited on  
a substrate of indium phosphide. The 
optical cavity was about 6 microns.
## Technical, Business Problems
When first presented, VCSELs were far from
the groundbreaking inventions that 
they eventually turned out to be.
There are a few reasons for 
this. On the technical side,  
the VCSEL had higher threshold currents 
than that of their side-firing counterparts.
The threshold current is the minimum 
current required to turn a laser on.  
A high threshold means that the laser 
cannot lase unless we pumped a very large  
current through them - leading to high 
power consumption and heat generation.
The heat was a legit problem as they can 
cause the semiconductor laser to shut down.  
That first 1979 VCSEL operated at temperatures 
of 77 Kelvin and did not fire a continuous beam.
Another issue concerned the "so what?". Many 
side-firing lasers were being announced - it  
was an exciting time in laser research history. 
Now here comes this funky surface-emitting thing  
with worse performance. People were not sure 
what they can use it for. Thus the skepticism.
In 1979, Iga went to the US for a year and 
a half to study at the legendary Bell Labs,  
where he worked on laser concepts unrelated 
to the surface-emitting laser. Upon returning,  
he dedicated himself to his idea.
## Lowering the Threshold
The key technical hurdle to overcome was the
high threshold current - which is 
responsible for the heat issues.
The high current was because the lasers' 
optical cavities leaked too much light.  
One way to fix that was to shrink 
the size of the optical cavity,  
which in turn means shrinking the active 
medium region between the two mirrors.
A smaller active medium means needing to make 
the mirrors much more reflective than before,  
something to the order of 99% or more. The 
mirrors must also be reasonably electrically  
conductive so that current can pass 
through to reach the active region.
This required acquiring various sophisticated  
epitaxy and metal-organic chemical vapor 
deposition machines to deposit thin,  
high quality films of dielectric 
and metal semiconductor materials.
In late 1988 (published in 1989), Iga and 
his team announced the first VCSEL that  
can generate a continuous laser light 
whilst operating at room temperature.
Shortly after or about the same time, 
a Bell Labs team led by Jack Jewell  
presented their own continuous 
wave, room temperature VCSEL.
What is notable about Jewell's VCSEL 
is that it used a quantum well for the  
active region and Bragg Reflectors 
for the top and bottom mirrors.
Quantum Wells are very small semiconductor  
layers that trap charge carriers and force 
them together in order to emit a lot of light.
Bragg Reflectors are mirrors made from many 
alternating layers of reflecting materials.  
Combined, they can achieve reflectivities 
of 99% or more. We use them in EUV machines.
Two different technical approaches 
to the same problem. Jewell's VCSEL  
was a bit weird in that it fired a laser 
out of its bottom through the substrate.  
Iga's still suffered moderate heat issues and 
worked better when bonded to a copper heatsink.
But the end results are the same: VCSELs became  
a practical technology - arriving on 
the scene at exactly the right time.
## DataCom
Researchers in the United States finally 
picked up on this progress - encouraged  
by shifts in US government technology 
spending after the end of the Cold War.
Optoelectronics attracted a lot of funding 
due to the rise of data communications and  
the Internet - which was shaping to demand 
different things from optical fiber technology.
Older systems developed by Bell were geared for 
long distance telephone calls - high performance,  
high-cost lasers and precision optical fiber 
for sending signals thousands of kilometers.
But the dynamics of data communications are 
different. The distances tend to be shorter,  
but the data volumes to be transferred are  
much greater - emphasizing lower cost 
multi-mode fiber and laser solutions.
For the VCSEL, the turning 
point was Gigabit Ethernet,  
an updated version of the popular Ethernet 
local area network standard. The target was  
to send a gigabit of data in both directions 
and the current LEDs were not good enough.
People investigated edge-firing lasers 
then used for CD players for this,  
but discovered those suffered low 
reliability. The structures of the  
VCSELs are a bit more complicated but 
for that you get several key benefits.
The most significant being cost. We can 
produce VCSELs at huge volume. Oftentimes  
up to a million lasers on a single 
wafer, making them very cheap. Since  
their light comes up from the surface, we 
can easily test all those lasers before  
cutting them out of the wafer. Not 
the case with edge emitting lasers.
VCSELs can also be easily packaged like LEDs  
and coupled to a fiber for digital 
modulation. And as I said earlier,  
their beams are round-shaped rather than 
rectangular, which offer optical benefits.
In the mid-1990s big companies like Motorola,  
Agilent and Honeywell started producing VCSELs. 
And in 1996 Honeywell broke the plane in publicly  
presenting production-level data and actually 
offering the VCSEL to the market in volume.
## The Mouse
Spurred on by the telecom boom, 
venture capital poured into VCSELs,  
sprouting many startups to 
develop higher performing lasers.
Things got a little bit out of 
hand. Jim Tatum of the VCSEL  
pioneer Finisar Corporation estimated 
30 startups during the peak which was  
obviously too much. Many went under or 
were acquired after the bubble popped.
The carnage in the post-bubble Datacom 
industry led companies to experiment  
with alternate use cases for 
VCSEL technologies. One that  
popped out was the optical mouse - which 
replaced the old-school trackball mice.
Optical mice work by illuminating the surface 
with some light source. Then a small CMOS  
sensor takes pictures of the surface, comparing 
the results to intuit the distance of travel.
The first optical mice used LEDs for that 
illumination. VCSELs fire a more coherent  
beam of light, making it easier to discern 
travel on weird surfaces like metals or glass.
In 2004, Agilent integrated the VCSEL into 
"engine modules" that allowed vendors to  
make laser-enabled optical mice. Other 
companies like Philips followed and today  
over a billion mice have been made. 
They have not quite obviated the LED  
like they did in Gigabit Ethernet, 
but sit comfortably in the high end.
## 3D Sensing
After the mice, 3D sensing has 
been the next major use case.
VCSELs are ideal for consumer devices 
because they do not use a lot of energy,  
do not generate a lot of heat, 
emit a tight spectrum of light,  
and are physically small. We can 
mount them right on the circuit board.
There are two major methods of doing 3D sensing 
with VCSELs: Structured Light and Time of Flight.  
This first method, Structured Light, involves 
projecting a dot pattern over a surface and  
observing how that dot pattern deforms over time. 
We interpret that data to understand the movement.
The first major consumer "gesture 
recognition" system was the Xbox Kinect,  
which gained a lot of hype in 
2013 as this new form of gaming.
The first version of the Kinect for 
the Xbox 360 used Structured Light,  
but suffered issues due to gaps in the 
dot pattern. Thus the second version  
of the Kinect switched to using Time of 
Flight, which was seen as more accurate.
Time of Flight is where we extract a 3D 
image by measuring the time it takes for  
the light to do a round trip from the 
VCSEL array to the thingy and back.
Despite the hype, the Xbox Kinect did not quite 
make the same type splash as the Nintendo Wii. But  
VCSEL arrays did find their big breakthrough with 
facial recognition technology on the mobile phone.
These use Structured Light to compare the dot 
pattern of a person's face with that inside  
the phone. Face ID. Apple's iPhone X, which 
hit the market in November 2017, brought this  
market to the big time and it has remained a 
core technology for mobile phones ever since.
## Conclusion
VCSELs remain important in data 
communications, but they seem to  
have finally hit their limits - especially for 
transmitting data over medium to long distances.
The current hotness seems to be in Lidar 
for automobiles - an application that has  
been growing a great deal and seeing a lot of 
competition thanks to EVs and self-driving cars.
Today they compete vigorously with 
traditional edge-emitting lasers for  
dominance in the Lidar stack - offering their 
traditional advantages of reliability, cost,  
and stability. Their downsides being 
lower efficiency and lower brightness.
But vendors continue to work on improving 
those weaknesses - new structures are  
continually being experimented on to 
extend detection range and resolution.  
The little laser that everyone uses 
continues to find new use cases.

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Asianometry

May 10, 2026

The Invention of the Surface‑Emitting Laser

Technical Challenges and Solutions

Commercialization and Market Applications

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Frequently Asked Questions

How did Bragg reflectors improve VCSEL performance?

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