Optical Engineering

Optical Engineering

  • John Jupe added an answer:
    Which techniques are used for three-dimensional imaging outside the visible light?

    Since conventional optics does not always work in the range outside the visible light (UV, IR) , it is very interesting how 3D imaging can be applied in this range.

    Can somebody give relevant references?

    Thank you in advance. 

    John Jupe · Perceptual Awareness Centre

    Hi Vladimir. There is no information structure 'blur' in the phenomenon of vision. No motion blur, no depth of field. There are no pictures in vision. No picture frames and no frames per second. As there are no pictures to call up then there is no binocular fusion going on. We have developed a new form of illusionary space based on perceptual structure not the fundamentals of optics. This is termed Vision-Space instead of picture space. Its spatial saliency is not on the 1,2,3D curve. It's experiential spatial saliency or ExpD! Presentation list attached and articles are on my page.

  • Cang Jin added an answer:
    Did anyone use before EDF (model:M5-980-125 from Thorlabs) as an active gain medium for fiber laser or fiber amplifier?

    I need to know the minimum length of this fiber to get signal gain

    Cang Jin · Laval University

    You can contact Thorlabs to get absorption spectrum, Er concentration and fiber parameters, and then you are able to calculate the cross section. Following, you use the simulation to find out the length suit for you. Or you just simply mention your application and the pump power you would like to employ, let Thorlabs answer your question.

    Good luck.

  • Muhammad Salili added an answer:
    I have trouble finding certain parameters of the liquid crystal E44. Can somebody help me with this and give relevant references/links?

    What is the value of the rotational viscousity of (Merck) E44 Liquid Crystal? How E44 depends on the voltage? I need to know these parameters for the experiment. Thank you in advance!

    Muhammad Salili · Kent State University

    chances are the value of rotational viscosity for this liquid crystal has not reported in the literature, and even if it has, it might not be at the temperature you are interested in. Therefore, I have attached the info about the  technique through which you can measure the rotational viscosity of any liquid crystal.

    Do you want to know how its retardation or birefringence depends on voltage? or the threshold voltage?

  • Zol Bahri Razali added an answer:
    Is it always necessary to position the injector vertically to study the spray characteristics using diagnostics instruments?
    If the orientation of injector is different , why have so many publications used vertical position as standard? If the injector is placed horizontally the dynamics will be different. Very few studies are attempted like this.
    Is it always necessary to study the SMD (Sauter mean diameter) value at the tip of the injector?
    Zol Bahri Razali · Universiti Malaysia Perlis

    Maybe related

    http://ebooks.spiedigitallibrary.org/book.aspx?bookid=121

  • Wurood Khalil asked a question:
    Can anyone suggest a paper or report dealing with the theoretical analysis of CW EDFL with a ring cavity?

    I need simple model to calculate gain, active medium length and the pump threshold.

  • How can I change the time step in simulating laser pulse drilling in COMSOL ?

    when I use pulse trains laser drilling , when the the  laser is on and off,  if adopt the same timestep, the computation time would be very long. Can I use different the timestep when the laser is on and off?However, when I use different range in time solver, the result would wrong.What can I do? Anyone else can tell me ? Thank you very much.

    Waranatha L Abeygunasekara · University of Peradeniya

    did you try to extend your small time step a little beyond the time duration the laser is on? for example instead of range(0,1e-6,1e-3), something like range(0,1e-6,2e-3).  It may be your answer is wrong because you are not capturing the transient effect correctly because you switch back to larger time step as soon as the laser is off. The computation time will be higher, but not as high as when you do the whole time period in shorter time step.

  • Santiago Royo added an answer:
    Which techniques and instruments can you recommend to identify optical aberrations of the optical systems?

    I want better understand this problem, and understand how I can compare simulation results with real data.

    Santiago Royo · Polytechnic University of Catalonia

    I agree. Depends a lot on application and accuracy. If you are interested in "normal" aberrations (third order Seidel) you will find plenty of methods in Optical Shop Testing, from nm to m accuracy. If you resconstruct the wavefront, do not be obscured by the value of "20th Zernike polynomial", or "tetragonal astigmatism". Only a few aberrations have clearly defined physical senses, and enable to introduce reasonable corrections. The rest is mathematical fitting of an infinite series.  

  • Jayaramakrishnan Velusamy added an answer:
    Which camera is suitable for femtosecond output image capture in the pump-probe experiment setup and what information can I get?

    new experimental setup to be set in our lab so can i get which camera suitable(specifications) for our work and what are the difficulties are to face while using camera in that setup and any measurement technique for analysis femtosecond output from camera.

    Jayaramakrishnan Velusamy · PSG Institutions

    Thank you very much dear  Romo-Cardenas for your helpful answer

  • Gabriele Marchi added an answer:
    What are the limitations of the Linear Canonical Transformation (LCT) in the practical optical system modeling?

    Linear canonical transformation is the useful tool for the light propagation description. When we prefer to use it for light propagation description? And when we prefer not to use it?When it is valid and when not? Thank you in advance.

    Gabriele Marchi · Munich University of Applied Sciences

    the LCT is what I usually call Fresnel propagation. It is valid anytime we can suppose the Huygens principle valid that means dimension of the source much smaller than the distance between source and measurement point. Personally I had everytime these conditions so I never found an example where is not applicable. Anyway this book :"K. IIzuka, Engineering Optics" delines very well the conditions where it is applicable or not.

  • Sylvain Girard added an answer:
    What is the influence of pre-irradiation defects on RIA of optical fibres?

    The prep-irradiation defects like some impurities can enlarge the linear attenuation of the fibre.
    But how this defect impact on the RIA?

    thx

    Sylvain Girard · Université Jean Monnet

    What will mostly influence the fiber RIA sensitivity is the level of precursor sites meaning defects that will be upon irradiation converted into other defects with stronger RIA at the wavelength of interest. This is the case for example for the GLPC in Ge-doped optical fibers that will be converted during irradiation in other Ge-related defects such as Ge(1) or Ge(2). Having already-absorbing strong defects may not help to enhance the sensitivity.

    So, to have the most radiation sensitive fiber, you must try to enhance the number of precursor sites that will lead to absorption at the wavelength of interest. One example: if your system works at 633nm, you could try to create a fiber with a lot of strained Si-O-Si bonds by using specific drawing conditions. When the fiber will be irradiated, these weak bonds will be converted into NBOHC absorbing at 630nm...

  • Md. Aliullah Sujan added an answer:
    What is the relation between evanescent field and v parameter for gas sensors?

    I have come to learn that at incident angle slightly higher than critical angle, the higher the wavelength, the deeper the penetration depth i.e more fractional power in evanescent field which tends to higher sensitivity. But when v is less than 2.405, it becomes single mode. so, is it necessary for evanescent field gas sensor to be multi mode always? or having single mode (v<2.405) won't be a problem? please help. 

    Md. Aliullah Sujan · Rajshahi University of Engineering & Technology

    Thank you for your help.

  • Rocio B Dominguez added an answer:
    Can anyone recommend best books in terms of quality and simplicity of explanations for optics implementation in the LABVIEW?

    Most of the simulations I perform in the MATLAB, so I almost not familar with LABVIEW, but It is a tool that can be very useful. I am mainly interested in the books describing the implementation of the Imaging (3D imaging, Hyperspectral imaging and Holography) in the LABVIEW. Thank you in advance!

    Rocio B Dominguez · Center for Research and Advanced Studies of the National Polytechnic Institute

    Hi Vladimir

    In my image processing course I checked the book Michael Young is posting and I found it very useful; but if, as you said, your expertise on Labview is limited you should take a look on this book first

    http://www.amazon.com/LabVIEW-Everyone-Graphical-Programming-Edition/dp/0131856723

    it covers almost all basic labview topics in a simplified way, which I think is important before to start with a specific toolbox such as image processing

  • Kaustav Bhowmick added an answer:
    Best sructure for high effective area in a PCF?

    What is the best structure to achieving high effective area in a solid-core silica-air hole photonic crystal fiber?

    Kaustav Bhowmick · National Institute of Technology Sikkim

    try 2-D PCF

  • Sayyed Jalil Mahdizadeh added an answer:
    Do you know of a good reference for Monte Carlo Simulation in the area of optical wireless communications?

    I wish to study optical wireless communications by employing Monte Carlo simulation. Is there a good reference (content examples) to start with.

    Sayyed Jalil Mahdizadeh · Ferdowsi University Of Mashhad

    Your welcome my friend.

    Be Happy

  • Guan Wang added an answer:
    How can I create a p-polarized gaussian beam in COMSOL 4.3?
    I want to simulate refraction of a gaussian beam at Air-anisotropic material interface in frequency domain.
    Guan Wang · Xi'an Jiaotong University

    you can  set a Gaussian Pulse and then set a variables functions which is the Gaussian product a exp(ikx)

  • Sara Liyuba Vesely added an answer:
    What is the physical meaning of the modulation transfer function (MTF)?

    Can somebody explain in the simple terms the physical meaning of the MTF?
    How does a turbulence in the air (atmosphere) affects on the MTF?
    How does the optical aberrations affect on the MTF?

    Sara Liyuba Vesely · itb cnr

    In my previous contribution I tried to avoid suggesting that the mathematical tools of the Fourier transform are mandatory to deal with Fraunhofer's diffraction. I just explained in a few words the physical meaning I would attach to the MTF, connecting it with the much older concept of Airy disc. The “wavy” effect of the aperture of the telescope on the images of stars, which I called OTF, was noticed well before it was mathematically interpreted. On the plane of the image of a diffraction limited system one always sees that effect of the aperture, which is not its image. According to this physical interpretation the blur of stars, and of the images of incoherently lit objects, is due to the “Fraunhofer diffraction image” of the aperture. Therefore, the MTF can be conceived as a generalization of the OTP, that takes into account how that train of thought evolved from the Airy disk to the analysis of optical lenses, and finally toward the standard conventions utilized in electrical engineering about amplitude and phase.

    I agree that, for Ronchi rules in nearly monochromatic light the OTF is due to them. In fact, in the applications of the linear filter theory to electro-optics systems, where the Fourier transform is applied, contrast variation depends also on  the constituent Fourier components of the imaged object.

  • Santiago Royo added an answer:
    Which technique for 3D imaging and visualization, the holography or plenoptic imaging will be dominant in the future 3D television?

    Which one of this techniques will be dominant? Or there are other rivals to this techniques?
    Thank you in advance!

    Santiago Royo · Polytechnic University of Catalonia

    Well, maybe a very interesting debate is what we all understand as 3D...I find myself often discussing on that. Is reconstruction of multiple planes in 2D able to be called 3D? Or is it depth perception by human eyes... hours of debate may follow. However in the end it comes to: 3D data or 3D perception? And the trick is both need each other.

    If I had to bet between your two options (I mean other techniques, e.g., time of flight or stereoscopy, are possibly not total outsiders here) I'd bet on holography, essentially because of the limits in spatial resolution there were in plenoptic imaging, at least when I analyzed the technique two years ago. Maybe things have evolved extraordinarily... But sure there is a lot of space for all techniques in different applications, as usually.

  • Gwendal Beauvois added an answer:
    How can I modify the OH stoichiometry in an optical fiber?

    I saw in some articles that OH stoichiometry can modify the RIA of some fibers. But I never find any informations in the fabrication cycle that can modify the OH stoichiometry.

    Thank you in advance for your advice and answer.

    Gwendal Beauvois · Université de Perpignan

    Thx a lot for you both to help me like that. It is very useful for me. And happy new year

  • Hemanth Pruthvi added an answer:
    What is the expression for the electric field vector of unpolarized light?

    What is the mathematical expression for electric field vector of unpolarized light?

    Hemanth Pruthvi · Indian Institute of Astrophysics

    Consider Stokes vector [S0; S1; S2; S3]. S0 represents the total intensity where as S1, S2, S3 represent various polarization states. For unpolarized light S1 = S2 = S3 = 0. Using the expressions of Stokes parameters in terms of the electric field, mathematical expression for the "time averages of the electric field" of the unpolarized light can be obtained. Please refer to the link, I found it really useful.

  • Salam Nazhan Ahmed added an answer:
    How can I measure the azimuth angle of an elliptically polarized light?

    I want to measure the azimuth angle of a elliptically polarized light. Could you give me some suggestions?

    Salam Nazhan Ahmed · Northumbria University

    First of all, you have to check that at a point close to threshold current, you can use one of these devices; linear polarizer or quarter wave plate (QWP) to find out the maximum output power of the laser, for instance, when use QWP, rotate the QWP angle until you have a maximum output power, for example, was at 0 degree,this corresponding to azimuth angle and a minimum output power will be at 45 degree of the QWP

  • Robert M. Malone added an answer:
    Which methods can you recommend for a speckle noise reduction in acquisition stage in the holography?

    I am interested in the methods to reduce the speckle noise in acquisition stage, but I am also interested in the speckle noise reduction in post-processing stage. Do you have any references?

    Robert M. Malone · National Security Technologies LLC

    To reduce speckle noise in the reconstruction of a hologram, we use a spinning diffuser and a sheet of holographic diffuser. The holographic sheet diffusers are specified by angles. We use either the 10 degree or 15 degree holographic diffuser. The spinning diffuser was originally a spinning aperture, bought commercially. We cut a disc of sheet protector film to make the 5 degree spinning diffuser. The combination of a static and a spinning diffuser completely eliminates the speckle noise.

  • Jan Winter added an answer:
    How to display the precious imaginary part of index in COMSOL4.4 when it is very small?

    I am trying to use COMSOL4.4 to calculate the confinement loss of PCF, and one way is using the imaginary part of index to calculate the confinement loss. However, when I do the experiment in COMSOL4.4, the smallest imaginary part of index is 0. This may due to the display limit of COMSOL, e.g. the imaginary part of index may be around e-11, it may be too small for COMSOL4.4 to display.

    I know in COMSOL3.5a, we can see the precious index by generating a report, however this seems does not work in COMSOL4.4.

    Do you have any idea how to deal this?

    I have applied PML in the model, so I don't think this is the problem.

    Jan Winter · Munich University of Applied Sciences

    The calculation of imaginary part in comsol must be taken account . You have to set up in your equation(physics) that the imaginary part must to calculate too. If you already calculate the real and imagninary part, you can show this with command "imag(x)" and "real(x)"

  • Bijan Goudarzi asked a question:
    How to catch exact dispersion curve in Lumerical Mode-solution?

    I have simulated a photonic crystal fiber by Lumerical mode-sloution. the substrate is SiO2 with air-holes along it. I have added SiO2 in material by defining its sellmeier coefficients. All the extracted results are acceptable except Dispersion!

    With finest changing in mesh geometry or mesh steps, dispersion changes dramatically. is there any specific setting or rule to extract an exact and stable dispersion curve vs. wavelength in Limerical mode-solution. please help me

  • Koji Hasegawa added an answer:
    How can I use Anisotropic Perfectly Matched Layer in Lumerical Mode-Solution?

    I am simulating a hexagonal photonic crystal fiber in mode-solution and need to use anisotropic PML. but there is no such an option. can any one guide me?

    Koji Hasegawa · Muroran Institute of Technology

    PMLs in cylindrical coordinates work well.

  • Parviz Parvin added an answer:
    Is it possible to perform some experiment to understand if LASER is based on 3 level or 4 energy level model?

    If it is possible, can anyone suggest an experiment which can allow understanding if laser is based on 3 level or 4 energy level model? For example, for LASER Nd:YVO4. Thank you in advance.

    Parviz Parvin · Amirkabir University of Technology

    "Gain is linear in 4-level system" Alexandr wrote:

    To which parameter is the gain linear? pumping rate, input intensity, or dopant concentration ?

  • Haiwei Chen added an answer:
    Can anyone recommend best books in terms of quality and simplicity of explanations for liquid crystal tunable lens design?

    I would like to know what is being done in this area to understand if that can be relevant to my research.Thank you in advance!

    Haiwei Chen · University of Central Florida

    http://onlinelibrary.wiley.com/doi/10.1002/9781118270080.ch6/summary

    check this one. it was written by H. Ren and S.T. Wu.

  • Parviz Parvin added an answer:
    Is it possible to make a simple optical set-up to reduce the spectral width of a laser source?

    Laser light is not fully monochromatic so is it possible to reduce its spectral width without using any monochromator?

    Parviz Parvin · Amirkabir University of Technology

    Tunable lasers handbook, I do not have the other!

  • Yoon-Soo Jang added an answer:
    What's the working principle of micro channel plates (MCP) Photomultiplier tube (PMT)?

    Why it's so special compared to traditional PMT? Why it can't respond to high repetition rate (tens of MHz) and need to be pulse picked to low down the repetition rate (~ tens of kHz)?

    Yoon-Soo Jang · Korea Advanced Institute of Science and Technology

    It takes a time to multiply photon in MCP.

  • Mina Esmaeelpour added an answer:
    How can I obtain the Fundamental Mode in an Octagonal solid core Photonic Crystal Fiber?

    I am simulating an Octagonal Photonic Crystal Fiber by Comsol. It is desired to extract some properties such as Dispersion, Confinement Loss and Effective Area vs. wavelength. For this purpose, I should obtain the Effective Refractive Index and Field Distribution for the Fundamental Mode. The Structure is a Solid-Core PCF (silica core n=1.45 and air holes n=1).
    How I can reach to the Fundamental Mode?

    Mina Esmaeelpour · Lehigh University

    Normally, fundamental mode has the highest group velocity, meaning the lowest n_eff. I recommend chapter 09 of the book below which is made available online by the authors.

  • David Compertore added an answer:
    Can somebody answer on few clarifying questions about Hartmann-Shack sensor?

    I have a few clarifying questions, that I want to ask:

    1)Which exactly aberrations can be measured by Hartmann-Shack sensor?

    2)If there are differences between aberrations which can be measured if wavefront is spherical and not plane wave?If we will add lens in the acquisition process which additional aberrations we will able to identify?

    3)Data (about aberrations) that we aquired by Hartmann-Shack sensor how it is practically can be used to improve the aberrations?

    4) Can we improve all aberrations that identified by Hartmann-Shack sensor or only part of them?

    David Compertore · Lumetrics, Inc.

    A set of Zernike coefficients has no meaning unless the Zernike aperture over which the analysis was completed is provided. I don’t know exactly how the Thorlabs software works, but once a set of Zernike coefficients are available points beyond the Zernike circle can be calculated. If the points are beyond the Zernike radius reported by the software, those points are extensions beyond the original data set and should be viewed as estimates. This is the case where the Zernike analysis circle is selected to fit completely inside the detector.
    If the original Zernike fit was made using the furthest available data point, typically along the diagonal, then the original fix contains the full set of available data. There is a disadvantage to this method, too. If the Zernike radius was set by the diagonal of the data then the coefficients were calculated with holes in the data set where no centroid information exists. The four area of the circle where the arc of the circle extends beyond the detector’s rectangular area have no data, but are inside the Zernike analysis. This is the case where the Zernike analysis circle is made large enough to cover the detector area.
    To analyze the physical size of your measurement you must scale by the aperture. Normalization is achieved by dividing the distance away from the center of analysis by the Zernike radius, which is often defined as the maximum distance from the center for which data exists. Multiply by the Zernike aperture to return to physical coordinates. In fact, determining the Zernike radius can be complicated. It is affected by the criteria for selecting the outer most area of interest. It is not necessarily just the coordinates of furthest from the analysis center centroid’s center of mass. Often, the size of the area of interest needs to be considered. Again sometimes averaging of data along edge points can be employed to calculate the Zernike radius. Of course if the Zernike radius is set by the user the existing data is used to calculate the best fit regardless of coverage, and the operator should review the residual fit error to ensure it is acceptable.
    A zonal fit to the data does not rely on the Zernike fit process. It provides a map of the difference from your reference surface for all data points gathered. It is good for mapping, but does not provide a simple set of coefficients for later analysis.

About Optical Engineering

Optical engineering is the field of study that focuses on applications of optics.

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