p**********g
发帖数: 378 | 1 老大，你给的 information 太少了啊想帮也帮不了。
先回答几个问题：
Small molecule or large molecule?
Peptide? Ionizable? pH?
sample stability? Temperature?
Column?
Mobile phase? Buffer?
Sample concentration? Diluent?
UV? Wavelength? |
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U**********b
发帖数: 13 | 2 【 以下文字转载自 Postdoc 讨论区 】
发信人: UofLlaserlab (UofLlaserlab), 信区: Postdoc
标 题: Post-doc Positions in Molecular Spectroscopy
发信站: BBS 未名空间站 (Mon May 23 14:08:21 2016, 美东)
Two Post-doc Positions in Molecular Spectroscopy at the University of
Louisville and the Ohio State University.
Two post-doctoral positions in experimental and theoretical molecular
spectroscopy are available in the research groups of Prof. Jinjun Liu at the
University of Louisville (UofL) and Prof. Terry A. Miller at the Ohio Stat... 阅读全帖 |
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q****i
发帖数: 6923 | 3 Poly(phenylenevinylene)s as Sensitizers for Visible Light Induced Cationic
Polymerization
Semih Erdur, Gorkem Yilmaz, Demet Goen Colak, Ioan Cianga, and Yusuf Yagci
Macromolecules, 2014, 47 (21), pp 7296–7302
http://pubs.acs.org/doi/abs/10.1021/ma5019457
A Dithienothiophene Derivative as a Long-Wavelength Photosensitizer for
Onium Salt Photoinitiated Cationic Polymerization
Binnur Aydogan, Ali Senol Gundogan, Turan Ozturk and Yusuf Yagci
Macromolecules, 2008, 41 (10), pp 3468–3471
http://pubs.ac... 阅读全帖 |
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k******t
发帖数: 28 | 4 extending from 9KHz to 3000GHz (wavelength 0.1mm~33km),
RF refers to frquencies with which an electromagnetic
field is generated suitable for wireless braodcasting
and communication.
AF(audio freq.) covers from 20Hz~20KHz however. |
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y*****n
发帖数: 5 | 5 Transparency or not depends on which wavelength you are talking about.
There are many methods to measure thin film's thickness, for example, using
AFM (Atomic Force Microscope), Cross sectional SEM (Scanning Electron
Microscope). For in situ measurement, you can use ellipsometry or QCM (Quartz
Crystal Microbalance), all those are standard methods for semiconductor
manufactuaring hence you can find their principles easily from related books
and internet. |
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c******k
发帖数: 1140 | 6 本人不是学电子的，近期要买示波器测 ultra short pulse.
center wavelength: 1550nm
Repetition rate: 40MHz
Pulse width: 100 Fs
请牛人解释一下什么样的示波器能满足我的要求？ 另外示波器面板上的4GHz和20Gs/S
是什么意思？多谢 |
|
c******k
发帖数: 1140 | 7 我们有个FR－103XL autocorrelator。Femtosecond fiber laser 连接这个
autocorrelator，autocorrelator有个PMT探测器，它的输出接示波器，进而观察
autocorrelation signal,不知道买个什么样的示波器（多少带宽和采样频率）就够用
了？谢谢
超短脉冲信息如下：
center wavelength: 1550nm
Repetition rate: 40MHz
Pulse width: 100 Fs |
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b****r
发帖数: 2555 | 8 大哥，你不是学光学的吧。
首先光纤的色散不影响频谱分布，这里不能简单的用傅立叶变换来套。光学信号有个
相关性的概念，它的时域和频域分布很可能不是傅立叶变换对。简单的例子，蜡烛光
在时域上是cw信号，但是频域上也是一个很宽的信号，这里就不是傅立叶变换对的关
系——因为蜡烛光没有相关性。
光纤色散从物理上来说就是各个频谱分量在光纤中的传输速度不一样，所以时域上表
现为脉冲会展宽，但是频域上可能不会受影响。比如说现在最新提出来的光纤传输概
念，就是有意识的增强光纤色散来压制非线性，最后在利用负色散来恢复信号在时域
上的分布。这个过程中信号的频谱就不会变化——roughly speaking。
光纤本身的传输带宽和色散没有什么关系，而是被光纤的材料以及设计所决定。也就
是所谓的cut-off wavelength。
回到原来的问题，脉冲展宽不说明脉冲在频谱上会变窄，没有必然联系。但是脉冲在
光纤中传输可能会变窄，原因是光纤本身的带宽，或者非线性。1.55微米30nm的信号，
大概是5THz的带宽，光纤的带宽可能够，也可能不够。可以设计一个简单的实验。
把激光输出光强降低10倍，再看通过光纤后的 |
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A*u
发帖数: 111 | 9 optical spectrum 就只有optical wavelength 的信息
你说的spectrum是optical spectrum吗？能被光谱仪探测到吗？
thin |
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A*u
发帖数: 111 | 10 since it is a fs pulse, the shape is only dependent on wavelength components
and their phases. |
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z*****n
发帖数: 7639 | 11 I don't know the case in US, but theoretically
a longer wavelength makes the signal propagate farer.
Here is a statistics that shows the activities
in each amateur band (in Ireland).
http://www.irts.ie/cgi/vhf.cgi |
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a*******o
发帖数: 67 | 12 请问一个题目，哪位同学帮个忙
做助教的课的一个作业题，老师让我帮他做出来，光纤通信的题目，学了快2年了，忘
得差不多了，当时的课本也没带过来，这边的课本也借不到，而且我印象中这个题中很
多概念以前光纤通信都没讲过，我现在的项目也不是做光通信的，所以看了半天，实在
不知道怎么做，哪位同学帮个忙，先谢谢了
A plane TE polarized lightwave with vacuum wavelength λ0 is incident on the
interface between two dielectrics at an angle of incidence of θ1=86°. The
two dielectrics have refractive indices n1=1.50 and n2=1.49. The incident
light is propagating in the higher index material
a) Calculate the relative field amplitude in both media as a function of
d |
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G***T
发帖数: 66 | 13 1. solution frequency decides wavelength therefore determine the initial
mesh size and total meshs in the simulation. What happened in HFSS is based
on your solution frequency, HFSS will generate a initial solution, which
includes the mesh, port solution and etc. based on that frequency.
2. After the inital solution, HFSS will automatically refine the mesh and
perform a full solution until convergence based on that single solution
frequency.
3. If your model can be convergented at your solution |
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m*******e
发帖数: 639 | 14 Yes, it really depends on the wavelength of the light source.
Intel already showed some results beyond that limitation. |
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c******k
发帖数: 1140 | 15 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 |
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c******k
发帖数: 1140 | 16 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 |
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g**h
发帖数: 15 | 17 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." |
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g**h
发帖数: 15 | 18 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 |
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c******k
发帖数: 1140 | 19 由于我们本来是想制作一个半导体光放大器的，但是出来laser bar 以后，由于
waveguide facet 镀膜及加工7度角成本较大，就没作。如果没做这些处理的话，出来
的是一个标准的FP laser diode。这个laser diode 在30mA 就发激光@1540nm
wavelength.
请问：在加电流小于30mA时，这个laser diode 能用作semiconductor optical
amplifier吗？自己简单测了一下，好像不能放大光在1540nm.但不清楚为甚么？还是我
的测量有问题？ 谢谢！！ |
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a****l
发帖数: 8211 | 20 I might be wrong, but it seems to me that even if semiconductor is not going
down it will still generate fewer and fewer optics jobs. The reason is
that with the increasing smaller die feature size, the way of making die is
moving away from optical methods, i.e., using lights. Wavelength is fixed,
and once the feature size is too small, no light spectrum will be suitable
for manufacturing. So, I would say eventually optics jobs will almost die
out in silicon industry.
hour |
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R****a
发帖数: 199 | 21 What kind of coupler can do this? Assuming same(similar) wavelength and
single mode fiber system. Please do not tell me couple different kinds of
polarization (but that may work for LZ's case if he/she has two well-
controlled polarized lasers). |
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c*u
发帖数: 916 | 22 我需要解决一个问题，似乎不会太复杂，但是我水平不够，所以请教各位高手，
我有一段SMF-28光纤，其cut-off波长是1250 nm左右，所以1250nm更长的光在其中可以
当作single-mode。这个光纤的末端，我加了一个lens，因为是single mode，所以其聚
焦特性很容易用Gaussian beam理论来研究。
但是我现在需要把一束绿光（532nm）的光导入该光纤，然后研究其聚焦特性，查了一
下一些光学的入门书，好像最多也就是研究其在光纤中的Laguerre-Gaussian modes，
没有说明怎么对这种multi-mode光的聚焦计算，尤其是怎么用ABCD来计算。大牛们能告
诉我这东西如何入手么？ |
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R****a
发帖数: 199 | 23 I guess the calculation is not easy. The reason is as following:
Your fiber is not single mode fiber for 532nm light for sure, but it is not
quite 'multi-mode' either. The core is small and the contrast is not that
large, it may be just a few modes. You can use a software or even use simple
scalor method to estimate how many modes supported.
But even you know how many modes are supported, you still cannot get much
information from this one. Since the fiber you used may be pretty long, the
mode p |
|
c*u
发帖数: 916 | 24 Fiber当然是不能换的,要不然这个问题就过分简单了:-) 我必须用SMF-28光纤，因为我
在公司，有很多别的人需要把那个光纤弄成smf-28。
多少个mode可以很容易计算，到底有哪些mode可以列举出来，甚至这些mode的分布也可
以计算出来。我所不明白的是，
1。对于这些mode经过透镜后，怎么计算，怎么用ABCD matrix或者其他办法。这样我至
少可以计算worst case scenario,
2。正如同你所说，比如有5个mode，这5个mode不见得光强度一样，这种mode间的
leakage和最后分布与光纤长度和弯曲度显然有关。显然不定态是很难弄的，有什么办
法保证大致上只在一个mode，或者全部均匀分布？
xiexie,
not
simple
the |
|
R****a
发帖数: 199 | 25 1。对于这些mode经过透镜后，怎么计算，怎么用ABCD matrix或者其他办法。这样我至
少可以计算worst case scenario,
You can do this for each mode. For the fundamental mode, you can make the
assumption that the mode shape is a Gaussian, then ABCD matrix works. For
higher order mode, I would say if the order goes up, the error goes up too.
(And ABCD matrix still works.)
http://www.newport.com/servicesupport/Tutorials/default.aspx?id=112
2。正如同你所说，比如有5个mode，这5个mode不见得光强度一样，这种mode间的
leakage和最后分布与光纤长度和弯曲度显然有关。显然不定态是很难弄的，有什么办
法保证大致上只在一个mode，或者全 |
|
b******g
发帖数: 77 | 26 高斯光束经过成像还是高斯光束，把高斯光束的分布和光纤中的模式做交叠积分，就可
以算各个模式所占比例 |
|
l***g
发帖数: 1035 | 27 thanks for the reference. by electrical length, do you mean wavelength of
the fundamental? |
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f****i
发帖数: 20252 | 28 check quater wavelength transformer |
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d*******2
发帖数: 340 | 29 Multi-Casting 1x9 Wavelength Selective Switch
请问其中的multi-casting中文怎么说？先谢了！ |
|
c**s
发帖数: 255 | 30 请教搞RF的同学，
我想设计的一个大概150MHz的transmitter，但是天线必须是一根很细的线，1/10的
wavelength大概是20cm，1/20是10cm。我想问一下，用这两个不同长度的antenna，
range上会有多少区别？ |
|
发帖数: 1 | 31 大家好，
我们研究组最近有一个博后职位空缺。有意者可以直接申请。
Research Fellow in Nanophotonic Devices (Job No. 0040356)
A Research Fellow in Nanophotonic Devices position under the supervision of
Professor Kenneth Crozier is available in the Department of Electrical and
Electronic Engineering, at the University of Melbourne. Further information
on Professor Crozier's research group can be found at: http://kcrozier.eng.unimelb.edu.au/
The position involves the experimental demonstration of long wavelength
infrared photodet... 阅读全帖 |
|
发帖数: 1 | 32 小弟是刚毕业的硕士学生。在实验室主要是做Graphene solar cell的，有两年的实验
室经验，已经thesis答辩完，马上准备发paper。最近找工作找的快崩溃了，求相关的
公司的前辈，帮忙内推。
贴上我的工作经历。
• At UIC, my thesis research focus is to develop transfer-free
graphene-on-silicon heterojunction solar cells and plasmonics enhancement of
photo-conversion efficiency and received 1.5% PCE
• Tested and optimized critical parameters to solve graphene
quality problem via Raman, XPS, FESEM
• Monitored the parameters (pressure, temperature, precursor gas
flow ... 阅读全帖 |
|
H***F
发帖数: 2501 | 33 刷题
小弟是刚毕业的硕士学生。在实验室主要是做Graphene solar cell的，有两年的实验
室经验，已经thesis答辩完，马上准备发paper。最近找工作找的快崩溃了，求相关的
公司的前辈，帮忙内推。
贴上我的工作经历。
• At UIC, my thesis research focus is to develop transfer-free
graphene-on-silicon heterojunction solar cells and plasmonics enhancement of
photo-conversion efficiency and received 1.5% PCE
• Tested and optimized critical parameters to solve graphene
quality problem via Raman, XPS, FESEM
• Monitored the parameters (pressure, temperature, precursor gas
f... 阅读全帖 |
|
发帖数: 1 | 34 大家好，
我们研究组最近有一个博后职位空缺。有意者可以直接申请。
Research Fellow in Nanophotonic Devices (Job No. 0040356)
A Research Fellow in Nanophotonic Devices position under the supervision of
Professor Kenneth Crozier is available in the Department of Electrical and
Electronic Engineering, at the University of Melbourne. Further information
on Professor Crozier's research group can be found at: http://kcrozier.eng.unimelb.edu.au/
The position involves the experimental demonstration of long wavelength
infrared photodet... 阅读全帖 |
|
d*****s
发帖数: 313 | 35 I am very new to polymer and basically blind of all the primary
measuring techniques. So my question may be too simple. hehe
I use spin-coater to get a polymer film. Then how can I measure the
thickness of this film? Laser? What if the film is not transparent to
normal laser wavelength? |
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c********n
发帖数: 7 | 36 There are several ways to measure the thickness.
Mass method only works for thickness larger than microns.
Ellispometry is the most popular method measure from 1 micron
down to few nonometers as in the case of SAMs. You have to know
some prior info for this technique, like optical constant
of substrate and film (wavelength dependent), which sometimes
is not easy to get. Some widely-accepted assumptions include:
1) for most thin organic film, n~1.45.
2) for thick polymer film, optical constant is |
|
b**s
发帖数: 589 | 37 深刻 //applaud
我记得印度的拉曼就是因为研究天为什么是蓝色的而获得了诺贝尔奖金 |
|
x*o
发帖数: 1037 | 38 Band gap between different orbitals?
Like UV: n-->Pai* et al...
Visible absorption is the same? |
|
x*o
发帖数: 1037 | 39 I don't know what due to the color of solid.
could you explain some? |
|
w******r
发帖数: 43 | 40 The crytal color comes from the impurities in the crystalline. If there is no
moleculer absorbtion, the crystal should be colorless.
The color of metal comes from its energy band structure, that means the band
gap determine its color.
The color of liquid shold be determined by the molecule structure, by its
molecule absorption. The mechanism is just like UV absorption. |
|
b**s
发帖数: 589 | 41 Mark, Mark
no
It seems that we polymer guys know polymers so well that there is no
question deserves to ask here :-), I decides to relinquish surfing BBS for a
period of time to prepare the approaching finals. If you’d like to discuss
with me, reach me via email at b**********[email protected] |
|
J******t
发帖数: 32 | 42 haha
是吗？
那我要去研究
地为什么是黄的。。。 |
|
d*****s
发帖数: 313 | 43 I know something about atomic absorption, not knowing much about
molecular absorption. But my naive thoughts tell me that every
absorption comes with radiation and satuation. Therefore, at a
stage, all absorpted photons will be radiated out, which leads
to white color whatsoever. I just do not know. |
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b**s
发帖数: 589 | 44 【 以下文字转载自 StartUp 讨论区,原文如下 】
发信人: salmon (salmon), 信区: StartUp
标 题: My idea
发信站: The unknown SPACE (Wed Feb 26 20:51:44 2003) WWW-POST
Ok, the idea will be like this:
every body are using the CD and DVD right now. one of the big concerns is the
capacity, like the current CD has a capacity of 750M/disc; DVD has a capacity
4.7G/disc, double sides will be around 9.5G/disc;
The future blue light tecnnology, which uses the short-wavelength blue light,
will has a capacity around 20G/disc.
all of the |
|
c*****e
发帖数: 238 | 45 I think dynamic/static light scattering is used for determination of the
structure factor for density fluctuation in phase transitions,
usually at the length scale of the wavelength of light.
X-ray scattering is used to determine the crystal lattice constants.
Neutron scattering could be used to determine the correlation functions of
deutrium, mostly used to characterize the conformation of a single chain,
what I know about SANS is it can be used to measure Rg. |
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f******n
发帖数: 4 | 46 It's probably some instablity which chooses a wavelength of tens micrometers. Capilary force may be one factor. Do you have two balancing forces which give you a length of tens microns? |
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D***e
发帖数: 435 | 47 using CQ (camphorquinone ) as photoinitiator to polymerizat acrylamide.
The what range of wavelength I should use. Does it really matter or at some ra
nge will be OK?
Thank you very much. |
|
c*s
发帖数: 2145 | 48 in case of cinamyl, the wavelength is 280 nm |
|
t***u
发帖数: 20182 | 49 有专门测turbidity的仪器，没用过。也可以用uv-vis的transmittance at certain
wavelength。
wiki：
Measurements of turbidity
The most widely used measurement unit for turbidity is the FTU (Formazin
Turbidity Unit). ISO refers to its units as FNU (Formazin Nephelometric
Units).
There are several practical ways of checking water quality, the most direct
being some measure of attenuation (that is, reduction in strength) of light
as
it passes through a sample column of water. The alternatively used Jackson
Candle method (u |
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d**a
发帖数: 3715 | 50 我们实验室有一些 ELC-500 Light Exposure System (Eletro Lite Corporation,
Wavelength = 365 nm). |
|
