쉐도잉 연습: Introduction to Optoelectronics and Photonics - 영상으로 영어 말하기 배우기

So in this video, I'm going to give an overview of optoelectronics and photonics.

And this is going to be the subject of many future videos on this discipline.

But what are the questions that we're trying to ask when we talk about optoelectronics and photonics?

Well, the core questions are first, how does light interact with matter?

and so from our everyday experience we sort of know that

if you send a beam of light at some material we know

that some of it is going to get absorbed so some of it's going to get absorbed

some might get reflected back to our eyes

so we can actually see it and depending on the material some might get transmitted through it.

So materials can be transparent, for example.

And so we're interested in what's happening exactly inside this black box.

So what is the process of absorption, reflection, and transmission look like?

And absorption is going to be our primary focus because this is sort of the core of how optoelectronic devices operate.

And once we understand this, we're going to answer the question that engineers are generally more interested in, which is, how can we create devices?

How can we create devices, devices is spelled with an E, that manipulate light?

so these are the likes of lasers LEDs absorption modulators all sorts of other other cool fun devices

and once we understand how light interacts with matter then we'll be able to start to understand

and answer the question of how we would go about designing a laser

or an LED

or how we go about analyzing them like what their limitations are what their spectrum looks like what their emission

or absorption spectrum looks like

and how we expect them to behave in a circuit now personally I think optoelectronics is probably the coolest

of all the disciplines I've been a part of and that's just

because it's so complicated like it's it requires so many different

so many different domains of knowledge you need to understand quantum

mechanics you need to understand electromagnetics you need to understand to

a certain degree circuits device physics devices physics doesn't start with

an s device physics to a certain extent you need to understand optics

and more general electronics and you need to understand most challenging is how all of these sort of behave together,

how one flows into another, and how they interact with each other.

And so I think optoelectronics is super cool to study for this reason.

And it sort of brings together many different domains of knowledge into a coherent model, which is really, really cool.

And so where do we start?

How do we go about figuring out how we're going to create devices?

Well, we're going to start with the two energy level system.

So these are just two different energy levels.

These aren't bands.

This isn't a band diagram like you might expect.

And each of these energy levels has some wave function associated with it.

So it's got some state, some electronic state that's associated with it.

And maybe we've got an electron up here residing in this state.

Maybe we've got an electron down here residing in this state

and we want to know what happens

or maybe we've got an electron in both

or neither we want to know what happens when I send in light

so when I send in light of a certain frequency

or equivalently a certain energy

so what happens to this system what happens to these electrons

where do they go what happens to the the energies of the system

if anything and once we understand just how two individual energy levels interact.

Just two.

So one, two.

From there, we'll be able to figure out how entire materials interact.

So from there, we go to analyzing the band structure or what's called the band structure of materials.

And you might see diagrams that look something like this.

So this is what band diagrams often look like in photonics.

And we'll go through, Don't worry if this scares you.

This is an energy momentum diagram And we'll go over what exactly everything means here, but briefly, energy is on the y -axis,

momentum is on the x -axis, and this lets us figure out how electrons and holes,

and in particular photons, are emitted and absorbed by this material.

So a photon, for example, we've got an electron up here and a hole down here.

We're allowed to emit a photon as these two recombine with each other.

So this is the conduction band and these are the various valence bands.

And so once we figure that out, once we figure out where photons are allowed to go between,

and we're also we'll also analyze things like quasi Fermi levels

so EFC and EFV and how these affect how these affect our absorption

or how the how these affect our band diagrams

and how we go about representing them once once we understand

this we can move to actually analyzing the absorption spectrum

or the absorption and gain spectrum of semiconductor devices

and specifically of bulk devices or if I've in other words

if I've just got a slab for example of germanium

or gallium arsenide or something what happens

when I send in light to this material how much of it is going to get absorbed within the material

and we'll actually be able to derive and plot what this absorption specter will look like, or what this absorption and gain specter will look like.

And we'll figure out how exactly that depends on things like the carrier concentration inside the material.

So this is alpha, and this is h bar omega, for example, on this axis.

And so alpha is the absorption coefficient.

And it will turn out that we can actually get negative absorption some of the time.

And this is called gain.

So this region where we have negative absorption is called gain.

So this is alpha equals zero on the y -axis.

And we'll understand how we go about getting gain out of a material or negative absorption.

And this is the basis for pretty much all lasers.

You need a material that gives you gain, and you'll see why in future videos.

But it turns out that instead of just having this hunk of material here,

so instead of just having this hunk of germanium or gallium arsenide or whatever light emitting or absorbing material,

it's actually way, way more efficient to have what are called quantum wells inside your system.

And so we'll analyze what exactly the absorption spectra looks like in that case, and it will turn out to look something like this.

Instead of this smoothly varying thing, we've actually got a staircase going on, and so this is for quantum wells.

We'll also briefly analyze things like quantum wires and quantum dots and what their absorption spectra look like.

And just as with the bulk case, we can also have gain in our quantum well.

So for certain, under certain conditions, we can have negative absorption.

And then it just tracks out whatever our gain looked like previously.

But we'll analyze when we can get this.

So when we can get this bizarre negative absorption, also known as gain, and what conditions need to be met for us to do that.

We'll also go over how you actually make these quantum wells, and what they look like, not just their conduction band, but also their valence band,

and what the consequences are of us having two of these.

And so this, for example, might be indium gallium arsenide.

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This might be gallium arsenide.

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And this is what's called a heterostructure.

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A heterostructure.

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And these are the basis for how all quantum wells are made.

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And this is how most modern lasers and LEDs are fabricated.

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So heterostructures are really the core of all of modern active optical devices.

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And so we'll understand how to analyze them, what their band diagrams look like,

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what happens when you inject electrons or holes

108

and where the energy levels are of this system

109

and from there the last thing you need to understand before

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you understand lasers is mirrors in particular mirrors in the configuration of resonators

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so we'll go over how resonators behave so if we've got some incident I didn't.

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electric field or some light, what happens as it bounces back and forth inside a mirror or inside a set of two mirrors?

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And so we'll analyze all of these bounces.

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And if we've got some material inside these two mirrors, which maybe it absorbs light,

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or maybe it has a certain negative absorption or a certain gain, what happens? So what happens here? And also,

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why do we even want to use resonators like why why

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can't we just stick chunks of optical optically active material

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that has a certain gain or a certain absorption and send light

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or send an electric field uh into that like what what's what's wrong with

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that why do we need these uh why do we need these resonators

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and to analyze these resonators we'll be going over the scattering matrix

122

which is sort of the central way of analyzing them it's it's quite intuitive

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if you've ever taken like an RF course before or circuits class

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or electromagnetics and this is connected to the transfer matrix of the system

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and these are actually used in practice

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so I actually use these use transfer matrix simulators to calculate

127

what my how my optical devices will behave in my research

128

and it's spectacularly accurate like it's just fabulous and after we understand mirrors

129

and resonators we'll finally be able to understand devices so things like LEDs

130

things like lasers also for example modulators so this is a central focus of my research right now.

131

And so I'm probably going to make a few videos on it.

132

But also things like photodetectors.

133

So photodetectors, these might be photodiodes, these might be photoconductors.

134

And we'll analyze briefly noise in all of these systems.

135

So lasers, LEDs, and photodetectors, and how this impacts device performance.

136

We'll also not just analyze these in what's called steady state,

137

or how these devices behave when you just sort of apply a constant voltage or a constant current,

138

but also what happens when you vary the current, or what are the dynamics of the system?

139

How fast can I get my LEDs or my lasers or my photodetectors to operate?

140

What are the limitations there?

141

And last but not least, we need to get light in and out of these systems.

142

And so we're going to go over waveguides.

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so we're going to go over how we actually transport light

144

from point a to point b on something like a photonic integrated circuit

145

or just across some distance and waveguides are the central way of doing this

146

so these are optical fibers are one kind of waveguide

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but we've also got slab waveguides as well as rectangular waveguides and other sorts of waveguides

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And waveguides are critical to sort of any time you want

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to move light from point A to point B without a massive amount of loss between the two points.

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You really need a waveguide.

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Now, you could also use lenses, or you could also use an optical system.

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But this is the subject of optics.

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And so this I go, I actually do have some videos right now in optics.

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And so you can give those a look if you like.

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and we might have time for some other special topics here

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and there so I might get into coupled mode theory

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which is something I've been meaning to learn for a very long time

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and maybe some other advanced topics as well depending on what the what the comments section pops up with

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but I'm really looking forward to you

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and taking this journey with me to learn optoelectronics

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and photonics it's it's a really cool discipline

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and I think you'll have a lot of fun and

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so with that I just want to say thanks for watching the video

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and if you have any questions or comments

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or video requests Just put them down in the in the comment section below

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and don't forget to like and subscribe for more optoelectronics and photonics videos

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이 레슨의 어휘와 말하기 포인트

이 영상에는 섀도잉할 문장 166개와 단어 2075개가 있습니다. 말하는 구간의 길이는 14:40입니다. 화자는 분당 약 141단어의 일정한 속도로 말해서 섀도잉하기에 편한 속도입니다. 단어의 83%가 영어에서 가장 많이 쓰이는 3,000단어에 속합니다. 나머지는 연습 전에 미리 확인해 두세요.

이 영상의 핵심 어휘

영상에 나오는 익혀 둘 만한 단어 15개를 발음, 뜻과 함께 정리했습니다.

단어	발음	뜻
absorption 명사	/æbˈsɔɹp.ʃn̩/	흡수
analyze 동사	/ˈæn.əˌlaɪz/	분석하다
laser 명사	/ˈleɪzɚ/	레이저
mirror 명사	/ˈmiɹɚ/	거울
spectrum 명사	/ˈspɛktɹəm/	스펙트럼, 분광
diagram 명사	/ˈdaɪ.ə.ɡɹæm/	다이어그램, 도표
behave 동사	/bɪˈheɪv/	처신하다, 행동하다
axis 명사	/ˈæksɪs/	축
electron 명사	/ɪˈlɛk.tɹɑn/	전자
physics 명사	/ˈfɪz.ɪks/	물리학, 물리
alpha 명사	/ˈæl.fə/	알파
discipline 명사	/ˈdɪsəplɪn/	규율
depend 동사	/dɪˈpɛnd/	의존하다, ...에 달려 있다
optics 명사	/ˈɑptɪks/	광학
topic 명사	/ˈtɑpɪk/	화제, 주제

이 영상의 문법

화자가 가장 많이 쓰는 문형을 영상 속 실제 표현과 함께 정리했습니다.

문형	영상 속 표현
수동태 be + 과거분사 — 누가 하는지보다 무슨 일이 일어나는지에 초점	is spelled · are emitted · are allowed
현재완료 have/has + 과거분사 — 과거의 일이 지금도 관련이 있을 때	I've been · you've ever taken

주의할 발음

화자는 we'll, we're, we've 같은 축약형과 약화된 형태를 53번 사용합니다. 들리는 대로 짧게 발음하세요.

“sh”와 “zh” 소리: absorption /æbˈsɔɹp.ʃn̩/, associate /əˈsoʊʃi.ət/, limitation /lɪmɪˈteɪʃən/, efficient /ɪˈfɪʃənt/, transmission /tɹænsˈmɪʃən/
긴 단어 — 강세 위치에 주의: associate /əˈsoʊʃi.ət/, momentum /ˌmə(ʊ)ˈmɛntəm/, limitation /lɪmɪˈteɪʃən/, complicated /ˈkɑm.plɪˌkeɪ.tɪd/, concentration /ˌkɑn.sənˈtɹeɪ.ʃən/

이 영상으로 연습하는 방법

먼저 말하지 않고 영상을 끝까지 듣고 모르는 단어를 적어 둡니다.
보통 속도로 한 문장씩 섀도잉하고, 화자의 리듬과 맞을 때까지 반복합니다.
자신의 목소리를 녹음해 원본과 비교하고, absorption, analyze, laser 같은 단어에 특히 주의합니다.

쉐도잉이란? 영어 실력을 빠르게 키우는 과학적 방법

쉐도잉(Shadowing)은 원래 전문 통역사 훈련을 위해 개발된 언어 학습 기법으로, 다언어 학자인 Dr. Alexander Arguelles에 의해 대중화된 방법입니다. 핵심 원리는 간단하지만 매우 강력합니다: 원어민의 영어를 들으면서 1~2초의 짧은 지연으로 즉시 소리 내어 따라 말하는 것——마치 '그림자(shadow)'처럼 화자를 따라가는 것입니다. 문법 공부나 수동적인 청취와 달리, 쉐도잉은 뇌와 입 근육이 동시에 실시간으로 영어를 처리하고 재현하도록 훈련합니다. 연구에 따르면 이 방법은 발음 정확도, 억양, 리듬, 연음, 청취력, 말하기 유창성을 크게 향상시킵니다. IELTS 스피킹 준비와 자연스러운 영어 소통을 원하는 분들에게 특히 효과적입니다.

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이 레슨의 어휘와 말하기 포인트

이 영상의 핵심 어휘

이 영상의 문법

주의할 발음

이 영상으로 연습하는 방법

쉐도잉이란? 영어 실력을 빠르게 키우는 과학적 방법