z**********n
发帖数: 39 | 1 3x
TEM00 is fundamental transverse mode of the laser resonator and has the same
form as a Gaussian beam.
Also, I know that diffraction causes light waves to spread transversely as
they
propagate, and it is therefore impossible to have a perfectly collimated
beam. The spreading of a laser beam is in precise accord with the
predictions of pure diffraction theory;
My question is :
why there is a beam waist without passing through any optics, for example,
objective?
Or my understanding is wrong, the |
|
a*****e
发帖数: 4577 | 2 比如单原子层的graphene
很多人也在讨论它的介电常数，让我觉得很难理解
没人回复所以干脆解释的详细一点：
以graphene为例
二维的体系，假设不考虑自由电子，那么在光学波段，
介电常数一般是由价带到导带跃迁引起的
吸收截面 a 正比于 介电常数的虚部 e2，e2可以通过考虑所有的跃迁几率得到
e2正比于\int_{cb,vb} u^2 \delta(e-\hbar\omega)，u为跃迁矩阵元，cb,vb是价带和
导带
对于graphene，假设层间的距离足够小，小到和graphite类似，介电常数的定义还是比
较明确的。OK,现在假设把graphene的层间距离加大。大到和光波波长类似，那么用光
波照射之后是否也会出现像bragg diffraction那样的情况呢，个人觉得应该有
这种情况下，如果用吸收截面的方法来理解，显然无法解释为什么会有diffraction
那么，问题在什么地方呢？ |
|
t**l
发帖数: 1284 | 3 假设有一个用ITO(indium tin oxide)做成的透射光栅，用一束激光打过去，可以看到
透射的diffraction pattern吗？
ITO是透明的，会不会没有diffraction pattern
Thanks a lot!!! |
|
|
h*********6
发帖数: 103 | 5 费曼物理讲义第3卷，2-2 Measurement of position and momentum
讲到让粒子穿过一个slit，会观察到diffraction。
Note that if we make B smaller and make a more accurate measurement of the
position of the particle, the diffraction pattern gets wider.
这里的B是hole width。
但是衍射是由粒子的波长决定的。如果是光，光有波长。如果是电子，则可以根据德布
罗意公式通过粒子速度来求波长。这些和slit width是没有关系的。
于是我就在这里糊涂了。 |
|
t****a
发帖数: 3544 | 6 In principle, all particles behaves like wave, which can show diffraction.
But in order to oberserve diffraction pattern, the split width is very
important. Otherwise, the wavefront will move as a free particle.
This is also the case for classical electromagnetic field
|
|
h*********6
发帖数: 103 | 7 〉Otherwise, the wavefront will move as a free particle.
I know this. Actually Feynman said, in his book "QED", that a big space (
here a wide slit) would make other wave paths cancel out so that the light
behaves like a particle.
However, what I am wondering here is:
Why did Feynman calculate diffraction pattern using the slit width, when the
slit width is comparable with the particle wavelength?
diffraction. |
|
t********y
发帖数: 166 | 8 In 1953, James Watson and Francis Crick suggested what is now accepted as
the first correct double-helix model of DNA structure in the journal Nature.
[5] Their double-helix, molecular model of DNA was then based on a single X-
ray diffraction image (labeled as "Photo 51")[169] taken by Rosalind
Franklin and Raymond Gosling in May 1952, as well as the information that
the DNA bases are paired — also obtained through private communications
from Erwin Chargaff in the previous years. Chargaff's rul... 阅读全帖 |
|
d*******2
发帖数: 340 | 9 http://www.edphoton.com/Non-diffraction%20Bessel-like%20Beam%20
Non-diffraction Bessel-like beam can be generated by LED light. This has
been demonstrated for the first time by Zhiming Cheng, Fengtie Wu, et al.,
scientists from Huaqiao University, China. The work has been published by
Scientia Sinica [Physica, Machanica & Astronomica, or China Science, (
Physics, Mechanics & Astronomy)], one of the top Chinese Scientific Journals
, in August 2012. |
|
|
k****g
发帖数: 88 | 11 口径大 = wider lens, to reduce airy diffraction, thus higher optical
resolution. |
|
x*****8
发帖数: 10683 | 12 本虾在爱荷华主攻生物物理化学（bio-pk)，虽然没有什么重要成果，但对现代医药学
还是有了解的。
大致思路是：
一个传染病总有细菌，衣原体，支原体，真菌，寄生虫，或病毒作为病原体吧。研究一
下病原体的结构（比如X-ray diffraction之类的物理手段），然后用计算机算出什么
样的小分子可以block病原体的那一部分（比如某个重要蛋白酶），我的任务主要就是
用量热计这个物理仪器测算enthalpy, entropy，Gibbs free energy，热稳定性等。 |
|
p*********t
发帖数: 2690 | 13 庄小威
维基百科，自由的百科全书
跳转到： 导航, 搜索
庄小威，1972年生于江苏省如皋县，是一位华裔美籍生物物理学家，哈佛大学化学与化
学生物、物理学教授，创办有庄小威实验室。[1][2][3] 她也是霍华德·休斯医学研究
所的研究员。[4]
1987年，她毕业苏州中学的科大少年班预备班。1991年，她获得中国科学技术大学物理
学学士；1997年，获美国加州大学伯克利分校物理学博士。她在1997年至2001年于斯坦
福大学攻读博士后。[5] 从她在哈佛建立自己的实验室开始，她带领研究团队发展超分
辨率显微镜技术（英语：super resolution microscopy）[6]，识别了个体病毒粒子进
入细胞的机理[7]，并用单分子技术从本质上研究核酸与蛋白的相互作用。
庄博士利用自己开发的超灵敏的光学成像技术来监测单一生物分子和联合体在体外或活
细胞内的瞬时行为，主要集中在理解病毒如何进入细胞及核酸-蛋白质相互作用。她拍
摄到单一枚感冒病毒如何影响一枚细胞，是首次有科学家记录到这过程。
庄晓薇34岁成为哈佛的化学和物理双学科正教授，HHMI研究员，她是哈佛物理系和化学
系少有的双... 阅读全帖 |
|
h******t
发帖数: 872 | 14 FDTD analysis/design, Maxwell 's equation.
based on this shap, you can use inverse FDTD design the shape of airplane(
DOE,diffractive optical element). a fast approach would be .... .only I know
! |
|
T**********e
发帖数: 29576 | 15 Maurice Wilkins把Franklin的DNA X-RAY 背着她给Watson 和 Crick展示,成全这两位
推导出DNA双螺旋结构发表在NATURE, 最后这三个老哥得了诺贝尔奖. 而Franklin得癌
症死掉.
Celebrating Rosalind Franklin: a perfect example of single-minded devotion
to research
Today's Google Doodle honours pioneering British biophysicist and x-ray
crystallographer, Rosalind Franklin
Today is the 93rd anniversary of the birth of British biophysicist Rosalind
Franklin, who was a pioneering x-ray crystallographer who is being honoured
today with a special Google Doodle.
N... 阅读全帖 |
|
m********5
发帖数: 17667 | 16 2013年已经进行过单电子Double-slit diffraction |
|
|
r*******6
发帖数: 545 | 18 人家工作还是很牛的，发了那么多好文章。
NAS Award in Molecular Biology goes to Xiaowei Zhuang
Professor Xiaowei Zhuang, recently designated David B. Arnold Jr. Professor
of Science here at Harvard, has been named recipient of the 2015 National
Academy of Science Award in Molecular Biology. This award is given "for the
development of a high-resolution microscopy method (STORM) that allows
molecular-scale resolution, by bypassing the ‘diffraction limit’ that has
long shackled light microscopy. In addition, she develo... 阅读全帖 |
|
|
p*******e
发帖数: 2310 | 20 个人觉得难度一般。
激光down conversion可以产生纠缠态的光量子。
单光子探测仪可能不是那么便宜。
其他的产生秘钥的光学器件，比如偏正片，分光片都很大众。
难度较高的是光量子存储器(memory)，一般是用mot，大众一点的用光纤。但如果只是
量子秘钥传输，没必要。
其他的技术问题，比如传输光纤的损耗，需要计算通过传输后纠缠态的fidelity. 潘团
队由于损耗过高，就提出了用卫星传送（>1000KM），因为在接近真空中，光子传送的
损耗率小。虽然有diffraction loss，但是比起光纤的损耗还是要小得多。 |
|
|
a****n
发帖数: 3082 | 22 在roger bach2013年的文章中，用的是双缝，文章标题，controller double slit
electron diffraction 缝与缝之间的距离是280nm
biprism |
|
j******r
发帖数: 1428 | 23 飞机对雷达隐形的理论就是如何减低电磁反射的理论,和飞控没关系, 飞控之类是搞隐
形的技术, 不是理论.
读物理的, 或读过J.D.JACKSON 的 ELECTRODYNAMICS 这门课的都知道这门课的能吸引
学生的话题之一(为数不多), 就是关于隐形飞机的电磁原理. 不论你在哪里读这门课,
说到这一理论的发现历史, 都要讲有关Petr Yakovlevich Ufimtsev (Пётр Я&#
769;ковлевич Уфи́мцев) 的PTD理论, 和他的书"Method of
Edge Waves in the Physical Theory of Diffraction"(1962) 以及关于 LM 和
NORTHROP的工程师就是拿着这书的英译本当教材加上SUPER COMPUTER 设计出F117和B2
的.
诺贝尔奖不会发给隐形, 若发的话, 公认的是要给Ufimtsev, 不会给美国的LM或
NORTHROP或任何其他人. 这都是有定论了N年的东西, 硬辩是没意义的.
成飞, 沈飞, 西飞, 南航, 北航, 凡是搞飞机的, 哪里没有几十本他的PTD?... 阅读全帖 |
|
t**i
发帖数: 3 | 24 The Purdue University’s Quantum Foundations and Quantum Photonics
Laboratory (Prof. Tongcang Li’s group) has open positions for self-
motivated excellent postdocs, graduate students, visiting students and
visiting scholars starting from 08/2014.
Tongcang Li
Assistant Professor of Physics and Astronomy
Assistant Professor of Electrical and Computer Engineering
Purdue University
Email: t**[email protected]
http://www.physics.purdue.edu/people/faculty/tcli.shtml
Selected publications:
1. Peng Zhang, To... 阅读全帖 |
|
发帖数: 1 | 25 Job linking: https://www.ornl.gov/careers
Job Posting Title: Postdoctoral Research Associate in Synthesis and
Heterogeneity of 2D Materials / NB50648234
Posted Date 12/14/2017; End Posting Date 02/14/2018
Purpose
We are looking for a Postdoctoral Research Associate to focus on the
synthesis and heterogeneity of two-dimensional (2D) materials. As a postdoc,
you will support in-house science projects at the Center for Nanophase
Materials Science (CNMS) that focus on how heterogeneity in 2D materia... 阅读全帖 |
|
|
q******g
发帖数: 390 | 27 Abergel, Rebecca J., Lawrence Berkeley National Laboratory, Berkeley, CA, “
Harnessing f㎡rbital Bonding through Precision Antenna Ligand Design for
Actinide Complexation,” selected by the Office of Basic Energy Sciences.
Braley, Jenifer C., Colorado School of Mines, Golden, CO, “Actinide N〥onor
Thermodynamics: Expanding the f〦lement Covalency Dialogue,” selected by
the Office of Basic Energy Sciences.
Cerfon, Antoine J., New York University, New York, NY, “High Performance
Equilibrium Solvers fo... 阅读全帖 |
|
V*****n
发帖数: 893 | 28 the design likely tried to ensure time and phase correct. The minimal baffle
design can can reduce early diffraction (the sound wave from the dome
tweeter can be reflected on the baffle and murky up the sound). |
|
V*****n
发帖数: 893 | 29 OK! ... although if you don't take others' advice seriously, why bother
asking us?
BTW: depending on the design of the grill, taking it off often results in
improvement (as you have noted). the reason is diffraction. early
reflections from the grill frame can muddy up the sound. But of course, like
you implied, physics may apply differently depending on how much your
equipments cost. |
|
B*D
发帖数: 5016 | 30 不过我觉得PSB revel一类的厂家
是否走得还是传统的好单元加做工好的箱子这种路线？
感觉Genelec一类的厂家更加注重声学技术的运用
比如8260A，等一些喇叭上用
“acoustically optimized rounded edges to prevent diffractions and yielding
superb sound stage imaging”
和什么waveguide技术的同轴单元
当然还有主动音箱的一套filter 分频 room correction等
【hifiman (hardcorehifi) 的大作中提到: 】 |
|
G****o
发帖数: 229 | 31 我在听，目前主要是讲如何推箱子
project是做 guitar amp 估计都是重点在做音箱吧
Week 1
Lesson 1: Introduction to wave propagation, simple oscillating systems,
sound pressure, sound waves, the speed of sound, wavelength, frequency and
wavenumber, sound pressure level, and auditory directional cues.
Lesson 2: Electronics fundamentals - charge, current, voltage, resistance,
Ohm’s law, DC circuits, finding currents and voltages in simple circuits
Week 2
Lesson 1: Reflection and absorption of sound, resonances in air columns,
res... 阅读全帖 |
|
Y*******m
发帖数: 744 | 32 【 以下文字转载自 Physics 讨论区 】
发信人: Yanbeanmm (hahaha), 信区: Physics
标 题: A TEM job opening at Micron
发信站: BBS 未名空间站 (Thu Jan 20 15:26:39 2011, 美东)
Contact me if you are interested -- pls note it is a TEM job-- so you must
have a daily or weekly based hand on experience on TEM.
Job Description
As a TEM Engineer at Micron's Transmission Electron Microscopy (TEM) Lab
located in Boise, Idaho, you will work with R&D research groups to develop
new processes and new materials and work with Fab Engineers to s... 阅读全帖 |
|
F******l
发帖数: 97 | 33 structural biologist的职位，为zt求个内推。hard core crystallographer（去aca
meeting被人评价的），phasing很强，符合招工要求。niw申请已经递交，无排期。140
下来前可能需要H1B或者其它雇主支持的visa。fresh phd，topic问题，文章不厉害（2
篇），但是有几个厉害的结构，包括perfect pseudo merohedral twinning，high
diffraction anisotropy，和9A的anomalous signal phasing的类型，全是他自己解出
来的。希望能借版上牛人之力弥补publication的弱项拿到面试。非常感谢！ |
|
m********u
发帖数: 3942 | 34 地点在加州 有兴趣的同学站内或者发邮件联系 [email protected]/* */
Job Description
This position is for an optical engineer working for Client's next-
generation optical technology. The optical engineer will be responsible for
investigation/development of the key optical component technology to enable
the Augmented Reality/Mixed Reality experience.
Responsibilities
Perform development and research of optical components, including
investigation of the cutting-edge technology and define the technical path
for Go... 阅读全帖 |
|
发帖数: 1 | 35 Please feel free to share it with your friends. Contact the hiring manager (
[email protected]) if interested.
Company: Micron Technology
Location: Boise, Idaho
Note: The requirement for work experience could be relaxed for candidates
with solid optics background.
Job Title: R&D Reticle Enhancement Technology Engineer
As a Reticle Enhancement Technology (RET) Engineer at Micron, you will be
responsible for the design and execution of resolution enhancement
techniques and optical proximity ... 阅读全帖 |
|
A******i
发帖数: 34 | 36 Summary:
The ideal candidate has extensive experience selling high end scientific
equipment to academic and government accounts as well as industrial accounts
such as petrochemical and mining. Experience selling into Canada is also
an advantage for this position. Knowledge of X-ray diffraction and X-ray
fluorescence techniques and equipment a plus.
Responsibilities include, planning, organizing, coordinating and executing
the company's direct sales function in the Pacific Northwest territory.... 阅读全帖 |
|
e*********0
发帖数: 79 | 37 职位性质：全职(Full time)
工作地点：纽约长岛(Long Island, NY)
工作经验：一年以上(one year+)
学历要求：博士 (Ph.D.)
专业要求：结构化学(structural chemistry)
岗位指责：
1、对公司的单晶X射线衍射服务项目提供技术支持，分析汇报实验结果；
2、配合销售人员，分析客户的需求，挖掘潜在客户；
3、熟练制作和使用幻灯片，与客户进行有效沟通；
4、了解并不断学习相关领域的科学进展，改进现有方法和应用，最大限度地提高效益。
任职资格：
1、博士学历，结构化学(structural chemistry)或者固相化学(solid state
chemistry)等相关专业；
2、可以独立操作单晶X射线衍射仪，熟练使用晶体化学行业软件；
3、2-5年蛋白质或者有机小分子单晶衍射经验，了解行业的状况及发展；
4、工作态度踏实，能适应紧张的工作，有较强的执行力；
5、责任心强，具备良好的团队合作精神和沟通能力；
6、优秀的英语听说读写能力。
联系人：宋女士
联系电话：631-722-1066
Email：e*********0@gmai... 阅读全帖 |
|
a**********y
发帖数: 20 | 38 高级有机合成研究员(Senior Scientist – Synthetic Chemist)
职位性质：全职(Full time)
工作地点：纽约长岛(Long Island, NY)
学历要求：硕士(M.S.)
专业要求：有机化学 (Organic Chemistry)
岗位指责：
1、从事新化合物的设计和合成，或临床化合物和上市药物的合成和工艺优化；
2、根据课题安排，合理设计实验方案并仔细实施；
3、独立承担高难度课题任务，保证按时完成课题任务；
4、科学分析实验中出现的问题，提出合理的改进建议；
5、能够独立进行有或无文献报道详细实验操作的目标化合物的合成；
任职资格：
1、美国本土高校毕业，有机合成领域硕士及以上学历；
2、熟练运用NMR，FT-IR，UV-Vis，LC-MS等分析手段和方法；
3、一年以上有机合成化学研发工作经验；
4、工作态度踏实，能适应紧张的工作，有较强的执行力；
5、责任心强，具备良好的团队合作精神，可带领多名实验助理开展研究工作；
6、优秀的英语听说读写能力。
药物化学研究员(Medicinal Chemist)
职位性质：全职(Full time... 阅读全帖 |
|
e*********0
发帖数: 79 | 39 联系人： Dr. Liu
联系电话： 631-398-3562/010-58426714
Email： [email protected]
/* */
公司网址： www.bocsci.com
公司简介： Creative Dynamics Inc是一家立足于中美两国的化学技术及产品服务
的公司，由一批资深留学人员创办，本部位于纽约长岛。公司成立的初衷是基于我们的
理想，充分利用中美两国丰富的化学技术资源，服务于两国科研机构及化学、制药企业
。我们欢迎有朝气，充满梦想和激情的你加入到我们中间来，共创美好明天。
薪资具有竞争力/员工福利全面/国内北京解决户口/美国办理H1
晶体化学专员(Specialist – Single Crystal X-ray Diffraction)
职位性质：全职(Full time)
工作地点：纽约长岛(Long Island, NY)
学历要求：硕士(M.S.)
专业要求：结构化学(structural chemistry)
岗位指责：
1、对公司的单晶X射线衍射服务项目提供技术支持，分析汇报实验结果；
2、配合... 阅读全帖 |
|
m*********o
发帖数: 4 | 40 Position Vacancies: Postdoctoral Fellow
University: Department of Electrical & Computer Engineering, National
University of Singapore
Supervisor: Prof. Cheng-Wei Qiu,
Website:
http://www.ece.nus.edu.sg/staff/web.asp?id=eleqc
Background (in one or two fields ): spin photonics, diffractive optics (e.g.
, hologram, vortex beam, etc), metasurface
Salary: negotiable
Contract duration: 1.5 years
Contact: [email protected]
/* */
Starting date: June 2015 |
|
m*********o
发帖数: 4 | 41 There are three post-doctor positions:
1. nanoprint for high resolution nanoscale color display (prefer canditates
with experience in Fano, FP, or relevant nanostructure resonance; and EBL,
FIB, EELS are pluses);
2. Diffraction optics with experience in DOE, holograms;
3. High efficiency metasurface, including experience in plasmonic/dielectric
metasurface.
Prof. Cheng-Wei Qiu
Department of Electrical & Computer Engineering
National University of Singapore
4 Engineering Drive 3, Singapore 117583... 阅读全帖 |
|
m********u
发帖数: 3942 | 42 【 以下文字转载自 JobHunting 讨论区 】
发信人: missingyou (miss), 信区: JobHunting
标 题: Optics Engineer
发信站: BBS 未名空间站 (Sun Mar 12 21:03:12 2017, 美东)
地点在加州 有兴趣的同学站内或者发邮件联系 [email protected]/* */
Job Description
This position is for an optical engineer working for Client's next-
generation optical technology. The optical engineer will be responsible for
investigation/development of the key optical component technology to enable
the Augmented Reality/Mixed Reality experience.
Responsibilities
Perform devel... 阅读全帖 |
|
发帖数: 1 | 43 Job linking: https://www.ornl.gov/careers
Job Posting Title: Postdoctoral Research Associate in Synthesis and
Heterogeneity of 2D Materials / NB50648234
Posted Date 12/14/2017; End Posting Date 02/14/2018
Purpose
We are looking for a Postdoctoral Research Associate to focus on the
synthesis and heterogeneity of two-dimensional (2D) materials. As a postdoc,
you will support in-house science projects at the Center for Nanophase
Materials Science (CNMS) that focus on how heterogeneity in 2D materia... 阅读全帖 |
|
c********g
发帖数: 143 | 44 LOL.
answer to first question is wrong: not diffraction/refraction but
scattering.... |
|
l*****l
发帖数: 222 | 45 Diffraction的可以考虑，人家有最大的中子源。 |
|
l*******0
发帖数: 215 | 46 The Advanced Energy Department at Lawrence Berkeley National Laboratory has
an opportunity for a Chemist Postdoctoral Fellow to prepare, characterize
and optimize electrode materials for rechargeable lithium-ion batteries.
This position supports the research activities in the Electrochemistry Group
in developing the next-generation batteries for use in electric, hybrid-
electric, and plug-in hybrid-electric vehicles.
Essential
• Synthesize electrode materials for rechargeable lithium ba... 阅读全帖 |
|
|
t**i
发帖数: 3 | 48 The Purdue University’s Quantum Foundations and Quantum Photonics
Laboratory (Prof. Tongcang Li’s group) has open positions for self-
motivated excellent postdocs, graduate students, visiting students and
visiting scholars starting from 08/2014.
Tongcang Li
Assistant Professor of Physics and Astronomy
Assistant Professor of Electrical and Computer Engineering
Purdue University
Email: t**[email protected]
http://www.physics.purdue.edu/people/faculty/tcli.shtml
Selected publications:
1. Peng Zhang, To... 阅读全帖 |
|
f*****l
发帖数: 3 | 49 http://pnnl.jobs/richland-wa/post-doctorate-ra-peptoid-synthesi
Job ID: 304908
Directorate: Physical & Computational Sciences
Division: Physical Sciences
Group: Materials Sciences
.
Job Description
The successful candidate will be a synthetic chemist or materials scientist
responsible for peptoid synthesis, purification and assembly. This
researcher will also be involved in exploiting peptoid assemblies for
applications. Instruments that will be used for peptoid synthesis and
purification includ... 阅读全帖 |
|
p*i
发帖数: 1481 | 50 【 以下文字转载自 Chemistry 讨论区 】
发信人: pbi (别让浮云遮望眼), 信区: Chemistry
标 题: 西南大学洁净能源与先进材料研究院诚招海外英才
发信站: BBS 未名空间站 (Fri Mar 16 15:37:16 2012, 美东)
Faculty Openings in Institute for Clean Energy & Advanced Materials (ICEAM),
Southwest University, Chongqing, P. R. China
Institute for Clean Energy & Advanced Materials (ICEAM) is a newly
established academic unit at Southwest University in Chongqing, aimed at
creating a world-class environment for research in clean energy, advanced
materials and related discipl... 阅读全帖 |
|
