c******k
发帖数: 1140 | 1 制作了一个长条 ridge waveguide 的Fabry-Perot laser,这个长条一共有三段波导可
以加driving bias,分别是波导1（270um）,中间波导（500um），波导3 (270um).
单独给波导1 或者 中间波导加current, 或者给波导1＋中间波导加current, 他们的激
射波长有很大的不同，不太懂FP laser, 怎么理解这一实验现象,请熟悉的朋友讲讲激
射波长跟其他参数的关系？ 谢谢! |
c******k
发帖数: 1140 | 2 请见图，FP laser 总长度 270 + 500 + 270=1040um |
c******k
发帖数: 1140 | 3 兄弟，是啊，一段波导有三个contact区域，给点意见吧，激射波长跟哪些参数有关？ |
c******k
发帖数: 1140 | 4 从激射光谱上看，即使加远高于阈值的电流值，还有若干个cavity mode,再贴个光谱图
看看。得不到一个单模，不清楚是否加更强的电流可以得到单模，又怕烧坏laser. |
L*****e
发帖数: 169 | 5 your question is stupid.
【在 c******k 的大作中提到】
: 从激射光谱上看，即使加远高于阈值的电流值，还有若干个cavity mode,再贴个光谱图
: 看看。得不到一个单模，不清楚是否加更强的电流可以得到单模，又怕烧坏laser.
|
R****a
发帖数: 199 | 6 If you add more current, as long as the laser is not damaged, you will get
more and more modes.
As mentioned in others' posts, you have no control over the longitudinal
modes on your laser. It is very natural to have multiple mode oscillation
for this case.
【在 c******k 的大作中提到】
: 从激射光谱上看，即使加远高于阈值的电流值，还有若干个cavity mode,再贴个光谱图
: 看看。得不到一个单模，不清楚是否加更强的电流可以得到单模，又怕烧坏laser.
|
R****a
发帖数: 199 | 7 Just a quick check of your spectrum, you can see the mode spacing is about 0
.5nm.
So, the frequency difference is about 6.2e10 Hz (that is FSR of your F-P
cavity).
Assume the refractive index of your laser material is 3 (I do not know which
on you are using), the cavity length is about 0.8mm (your number is 1mm).
Given the roughness of this estimation, it is quite clear that those modes
are just longitudinal modes of your F-P laser.
Several ways to achieve single mode operation. You may check y
【在 c******k 的大作中提到】
: 从激射光谱上看，即使加远高于阈值的电流值，还有若干个cavity mode,再贴个光谱图
: 看看。得不到一个单模，不清楚是否加更强的电流可以得到单模，又怕烧坏laser.
|
R****a
发帖数: 199 | 8 Be NICE! ;) Accumulate more RP! ;)
【在 L*****e 的大作中提到】
: your question is stupid.
|
c******k
发帖数: 1140 | 9 Very clear, thanks a lot!
0
which
book
you
【在 R****a 的大作中提到】
: Just a quick check of your spectrum, you can see the mode spacing is about 0
: .5nm.
: So, the frequency difference is about 6.2e10 Hz (that is FSR of your F-P
: cavity).
: Assume the refractive index of your laser material is 3 (I do not know which
: on you are using), the cavity length is about 0.8mm (your number is 1mm).
: Given the roughness of this estimation, it is quite clear that those modes
: are just longitudinal modes of your F-P laser.
: Several ways to achieve single mode operation. You may check y
|
c******k
发帖数: 1140 | 10 我贴的那个激射频谱图是偏置加在中间波导上，中心波长大约在1560nm,
如果偏置加在波导3上或者波导1上，激射的中心波长会偏移到1574nm左右，频谱间隔也
都是0.5nm.
这个现象如何理解？谢谢！
（当然偏置电流加载中间波导或者波导1时，他们阈值电流不同）
0
which
book
you
【在 R****a 的大作中提到】
: Just a quick check of your spectrum, you can see the mode spacing is about 0
: .5nm.
: So, the frequency difference is about 6.2e10 Hz (that is FSR of your F-P
: cavity).
: Assume the refractive index of your laser material is 3 (I do not know which
: on you are using), the cavity length is about 0.8mm (your number is 1mm).
: Given the roughness of this estimation, it is quite clear that those modes
: are just longitudinal modes of your F-P laser.
: Several ways to achieve single mode operation. You may check y
|
|
|
R****a
发帖数: 199 | 11 Also somebody else asked:
那加电区域不同，lasing 的光谱会左右偏移？
Here is my guess, if you put the same current on different contact, you will
have different carrier density (and different amount of inversion) in the
gain region. That is possible to have some shift in the spectrum center.
【在 c******k 的大作中提到】
: 我贴的那个激射频谱图是偏置加在中间波导上，中心波长大约在1560nm,
: 如果偏置加在波导3上或者波导1上，激射的中心波长会偏移到1574nm左右，频谱间隔也
: 都是0.5nm.
: 这个现象如何理解？谢谢！
: （当然偏置电流加载中间波导或者波导1时，他们阈值电流不同）
:
: 0
: which
: book
: you
|
R****a
发帖数: 199 | 12 Please refer to
http://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_6/backbone/r6_1_2.html
Also, if you have the book
Fundamental of Photonics, please check chapter 16: Semiconductor Photonic
Sources.
You may see that the gain is a function of frequency. I think they reason
the gain peak shift can be thought as the following way:
If a lot of current are injected, those electrons (actually similar things
to holes, I just describe one side, which is easier) certainly would occupy
the lower states fi |
R****a
发帖数: 199 | 13 Let's take the number from the picture in page
http://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_6/backbone/r6_1_2.html
Say the injection level can induce a shift of spectrum in tens of meV.
1meV is ~ 2.4e11 Hz.
At 1.55um band, 1nm is about 1.25e11Hz.
So, tens of meV can cause the change more than 10nm.
Certainly, the number needs to be checked for confirmation.
nm |
c******k
发帖数: 1140 | 14 对于中间电极：input bias: 80mA
对于电极1或者电极3：input bias: 125mA
现在贴上电极3加电流125mA后的激射频普图，以便参考。
感谢大家的讨论，本人激光器新手，也在学习之中。。。
从实验上看，增加bias current, 就举中间电极加电的例子，从80mA加到100mA，中心
波长会红移一点，<1nm左右。
正如你疑问的，中间电极加电和电极3加电，他们的中心波长差别很大，很是奇怪。 |
c******k
发帖数: 1140 | 15 You were saying if the density is higher, the higher states in the
conduction band would be occupied. That would result in a higher frequency
or a lower wavelength.
From my measurement, compared to the lasing spectrum between the middle
contact and the contact 3, the lasing wavelength from the contact 3 (1574nm)
is larger than that of the middle contact (1560nm) meanwhile the current
density of the contact 3 is higher than that of the middle contact. But this
is contrary to what you are talking
【在 R****a 的大作中提到】
: Please refer to
: http://www.tf.uni-kiel.de/matwis/amat/semi_en/kap_6/backbone/r6_1_2.html
: Also, if you have the book
: Fundamental of Photonics, please check chapter 16: Semiconductor Photonic
: Sources.
: You may see that the gain is a function of frequency. I think they reason
: the gain peak shift can be thought as the following way:
: If a lot of current are injected, those electrons (actually similar things
: to holes, I just describe one side, which is easier) certainly would occupy
: the lower states fi
|
R****a
发帖数: 199 | 16 What happens if you inject current to all three contacts?
Also, you made the laser or you buy/get it from somewhere else?
A schematic drawing of your laser might also be helpful (including the
waveguide structure and material).
1574nm)
this
bigger
【在 c******k 的大作中提到】
: You were saying if the density is higher, the higher states in the
: conduction band would be occupied. That would result in a higher frequency
: or a lower wavelength.
: From my measurement, compared to the lasing spectrum between the middle
: contact and the contact 3, the lasing wavelength from the contact 3 (1574nm)
: is larger than that of the middle contact (1560nm) meanwhile the current
: density of the contact 3 is higher than that of the middle contact. But this
: is contrary to what you are talking
|
c******k
发帖数: 1140 | 17 Thank you for your interest.
1.To keep the same current density on the waveguide, the bias current for
the middle contact is always 1.8 times larger than that of the contact 1 and
contact 3. If I inject current for all three contacts, the center lasing
wavelength would be around 1546nm. See the attached picture.
2.We made this FP laser on our own with a pretty standard procedure, and the
commercial available substrate is InP with 6 AlGaInAs quantum wells (Well:
6nm Al0.27GaIn0.71As Barrier: 10n
【在 R****a 的大作中提到】
: What happens if you inject current to all three contacts?
: Also, you made the laser or you buy/get it from somewhere else?
: A schematic drawing of your laser might also be helpful (including the
: waveguide structure and material).
:
: 1574nm)
: this
: bigger
|
R****a
发帖数: 199 | 18 QW material does (should) have different behavior in terms of the lasing
frequency comparing to bulk material. I am not quite familiar with that.
On the other hand, if you have some kind of absorbers (like un-driven
sections) in your laser, it might get too messy to understand its behavior
easily.
and
the
3um.
contact
【在 c******k 的大作中提到】
: Thank you for your interest.
: 1.To keep the same current density on the waveguide, the bias current for
: the middle contact is always 1.8 times larger than that of the contact 1 and
: contact 3. If I inject current for all three contacts, the center lasing
: wavelength would be around 1546nm. See the attached picture.
: 2.We made this FP laser on our own with a pretty standard procedure, and the
: commercial available substrate is InP with 6 AlGaInAs quantum wells (Well:
: 6nm Al0.27GaIn0.71As Barrier: 10n
|
M***a
发帖数: 175 | 19 三个sections公用同一个光学腔。所以中心波长不仅仅受偏置section的gain spectra
peak决定。另两个sections的吸收谱会同时影响中心波长。
【在 c******k 的大作中提到】
: Thank you for your interest.
: 1.To keep the same current density on the waveguide, the bias current for
: the middle contact is always 1.8 times larger than that of the contact 1 and
: contact 3. If I inject current for all three contacts, the center lasing
: wavelength would be around 1546nm. See the attached picture.
: 2.We made this FP laser on our own with a pretty standard procedure, and the
: commercial available substrate is InP with 6 AlGaInAs quantum wells (Well:
: 6nm Al0.27GaIn0.71As Barrier: 10n
|
g**h
发帖数: 15 | 20 Don't know if the issue solved or not. But here are my 2 cents.
You also need to consider the heating effect. I noticed that the driving
current is so different: injection with all regions 20mA, region2 80mA, and
region3 120mA. 20mA is the pretty standard for this type of laser.
When you only inject current into certain region of your laser waveguide,
the other region becomes absorber, and force you to inject more current into
it to get enough gain. If no temperature effect, the more current you
【在 c******k 的大作中提到】
: Thank you for your interest.
: 1.To keep the same current density on the waveguide, the bias current for
: the middle contact is always 1.8 times larger than that of the contact 1 and
: contact 3. If I inject current for all three contacts, the center lasing
: wavelength would be around 1546nm. See the attached picture.
: 2.We made this FP laser on our own with a pretty standard procedure, and the
: commercial available substrate is InP with 6 AlGaInAs quantum wells (Well:
: 6nm Al0.27GaIn0.71As Barrier: 10n
|
|
|
c******k
发帖数: 1140 | 21 When I am injecting current to the InP lasers, I am always using a thermal-
electric cooler (TEC) control, and the setting point of temperature is 20C.
So you are saying the 14nm wavelength shift corresponds 30-40C temperature
change. But because of the TEC, I don't think so the laser device could have
so high temperature change.
I talked to my boss, and he is thinking the larger wavelength shift could be
due to the refractive index change with the increasing of injection current
.There is a pap
【在 g**h 的大作中提到】
: Don't know if the issue solved or not. But here are my 2 cents.
: You also need to consider the heating effect. I noticed that the driving
: current is so different: injection with all regions 20mA, region2 80mA, and
: region3 120mA. 20mA is the pretty standard for this type of laser.
: When you only inject current into certain region of your laser waveguide,
: the other region becomes absorber, and force you to inject more current into
: it to get enough gain. If no temperature effect, the more current you
|
g**h
发帖数: 15 | 22 What I mean 30-40C temperature change is the QW local temperature, but not
LD substrate temperature. Most of current injected will recombine in QWs and
generate heat there, so the QW local temerature is quite different from
where you put thermocouple for your TEC. You should examine carefully on
where the thermocouple is located, because that's where you get 20C
temperature reading.
For most efficient cooling, LD should be bonded upside down, did you use TEC
in that way? Btw, If my speculation i |
c******k
发帖数: 1140 | 23 Let's focus on the middle contact only with bias. Here at T=20C we have had
a lasing center wavelength with 1560nm. If I increase T=40C using TEC for
the whole laser substrate, what lasing wavelength would you expect? I think
you will say the lasing wavelength at T=40C will be a red shift (lower
energy of light), right?
I will do this test later to see the lasing wavelength is having a blue
shift or red shift when I have a higher T.
and
into
generally
【在 g**h 的大作中提到】
: Don't know if the issue solved or not. But here are my 2 cents.
: You also need to consider the heating effect. I noticed that the driving
: current is so different: injection with all regions 20mA, region2 80mA, and
: region3 120mA. 20mA is the pretty standard for this type of laser.
: When you only inject current into certain region of your laser waveguide,
: the other region becomes absorber, and force you to inject more current into
: it to get enough gain. If no temperature effect, the more current you
|
g**h
发帖数: 15 | 24 If you increase temperature of TEC from 20C to 40C and meanwhile only add
bias on middle contact, I would expect the following:
1. Higher threshold current.
2. Lasing wavelength red shift 5~10nm.
3. The relative change of lasing wavelength from different bias schemes won'
t change much.
had
think
【在 c******k 的大作中提到】
: Let's focus on the middle contact only with bias. Here at T=20C we have had
: a lasing center wavelength with 1560nm. If I increase T=40C using TEC for
: the whole laser substrate, what lasing wavelength would you expect? I think
: you will say the lasing wavelength at T=40C will be a red shift (lower
: energy of light), right?
: I will do this test later to see the lasing wavelength is having a blue
: shift or red shift when I have a higher T.
:
: and
: into
|
c******k
发帖数: 1140 | 25 I just did the test. You are right. The lasing wavelength is shifted to be
around 1581nm when I am driving a current (125mA) only with the middle
contact meanwhile the TEC temperature is set to be 40C. The threshold
current at T=40C is up to 110mA compared to 70mA at T=20C.
For the case of TEC location, our device is attached on the surface of a
piece of bulk AlN.The bulk AlN is on the top of a copper stage. There is a
thermistor inside the stage,and the stage is on the TEC. In this case, I
beli
【在 g**h 的大作中提到】
: If you increase temperature of TEC from 20C to 40C and meanwhile only add
: bias on middle contact, I would expect the following:
: 1. Higher threshold current.
: 2. Lasing wavelength red shift 5~10nm.
: 3. The relative change of lasing wavelength from different bias schemes won'
: t change much.
:
: had
: think
|
g**h
发帖数: 15 | 26 Quote: "If the band gap is not shrinked, those electrons in the valence band
maybe occupy those lower energy states of the conduction band of QW when
the temperature is high. So the lasing wavelength is red-shifted." |
c******k
发帖数: 1140 | 27 Sorry, 我的意思是说：
你讨论的高温度下QW band-gap shrinkage是解释激射波长红移是唯一的一个原因呢？
还是只是可能的一个原因。或者说你这个说法已经是一个不容置疑的事实呢？还是只是
你的一个猜测。
当然我自己也要查查这方面的文献，
我自己想到的一个原因是 （只是猜想或者是空想）：如果高的温度下QW band-gap 宽
度维持不变，但是价带的电子在高温下只能占据导带的较低的那些能级，如果这样，激
射波长也是红移。
Thank you!
band
【在 g**h 的大作中提到】
: Quote: "If the band gap is not shrinked, those electrons in the valence band
: maybe occupy those lower energy states of the conduction band of QW when
: the temperature is high. So the lasing wavelength is red-shifted."
|
g**h
发帖数: 15 | 28 If no other major effect, the higher the temperature, the lower the bandgap
and longer lasing wavelength. This is a fact.
What I proposed is just my speculation based on my understanding. I don't
have first experience to obserse such type of laser before. But I can
predict that if you enhance TEC cooling efficiency (for example, by putting
laser upside down), you will find it's more difficult to get lasing if my
guess is right.
About your speculation, I don't know what you mean "electrons in the |
c******k
发帖数: 1140 | 29 It is very had to put the laser upside down to increase the TEC cooling
efficiency, since there are three gold wires sticking out from the three
contact pads.Some papers say they are using pulse current injection to avoid
to increase the temperature resulting from the bias itself.
Anyway, you help me a lot. Many thanks!
bandgap
putting
valence
describe
electrons
【在 g**h 的大作中提到】
: If no other major effect, the higher the temperature, the lower the bandgap
: and longer lasing wavelength. This is a fact.
: What I proposed is just my speculation based on my understanding. I don't
: have first experience to obserse such type of laser before. But I can
: predict that if you enhance TEC cooling efficiency (for example, by putting
: laser upside down), you will find it's more difficult to get lasing if my
: guess is right.
: About your speculation, I don't know what you mean "electrons in the
|
g**h
发帖数: 15 | 30 Cityhawk, my bad. Since I was not doing any laser stuff for years, forgot a
lot of things. Yes, if you have a pulsed laser current source and companion
equips, you can test my speculation quickly.
Hope my 2 cents useful and you're very welcome. |
