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t*i
5 楼
没人能回答吗?哪怕给点道听途说的消息也好。
c*k
6 楼
请见图,FP laser 总长度 270 + 500 + 270=1040um
G*T
7 楼
if you want free ads, then have to do SEO for your site.
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.
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
i don't know how to reply messsag, it displayed wrong user id. i was an mba student, right now, i am applying for phd program, but little chance
【在 L****i 的大作中提到】 : co-ask
R*a
21 楼
Be NICE! ;) Accumulate more RP! ;)
【在 L*****e 的大作中提到】 : your question is stupid.
r*g
22 楼
Any other good websites for business school faculty job information?
c*k
23 楼
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
k*t
24 楼
www.ssrn.com Click individual network link on the left panel. There are job opening listings in each network Also, you could go to the website of the association of each discipline, such as American Accounting Association, American Finance Association... There are listings there as well. Schools that do not post ads may still hire.
【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
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
28 楼
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
29 楼
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.
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
32 楼
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
33 楼
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
34 楼
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
【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
36 楼
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
37 楼
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
38 楼
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
39 楼
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
40 楼
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
41 楼
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
42 楼
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."
【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
44 楼
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
45 楼
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
46 楼
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.