Hi Astghik, One issue with modeling fiber output is that the angular distribution of the output can depend on the stimulus at the fiber input. However, I have used several methods for approximating fiber output: 1) The Source Ellipse in the Source Distance mode. Here the source aperture is filled with rays such that all the rays appear to emanate from a point. We can calculate the source distance as the semidiameter / Tan[halfAngle]. This is reasonable in the far field, but in the near field or for imaging applications the fact that the fiber output appears as a point source is a strong disadvantage. 2) The Source Ellipse with a Gaussian specification. The Intensity as a function of direction cosines is given by I = I0 Exp[-Gx l^2 - Gy m^2]. If Gx = Gy then the distribution is radially symmetric since l^2+m^2 = (1 - n^2). We can, for example, calculate Gx = Gy = G such than at angle theta the intensity falls to 1/E^2 from G (l^2+m^2) = 2, where l^2+m^2 = (1-n^2) and n^2 = Co
The size of the beam is, well. the size of the beam on the specified surface. The waist is the waist (minimum size) of the beam, and it is located at the location (position) specified as measured from that surface . In your example they are the same since the surface is at the waist in any case. You compare the position of the waist to the Rayleigh range to determine whether the beam on the surface is inside the slowly-varying part of the wavefront propagation or is in the linearly varying part of the wavefront propagation. Hi Mark, Yes,size and waist are the same when the surface is at the waist. I am confused when the M2 = 1,waist size,size,waist are the same. when M2=16,waist=SQRT(M2)*waist size. How do they calculate and when I simulate multimode laser, should I use waist size or waist?
@Mark.Nicholson Hello Mark,I read your article about M2 definition in zemax, which I think is very good. 1. I try to deduce the relationship between M2 and the waist size and the waist. I multiply the formula of the waist size by M, and the result is basically the same as the result of the Paraxial Gaussian Beam Data in ZEMAX. Is my formula correct? 2. Another question, waist (in physical optics propagation) = waist size or waist (Paraxial Gaussian Beam data)? I don't really understand the difference between waist size and waist.Regards,Lenror
Hello,1. The laser equipment outputs Gaussian laser through the fiber. Is the fiber core diameter equal to the beam waist diameter?2. Does ZEMAX have a way to simulate multi-mode Gaussian laser output with a fiber diameter of 200-600um?
Hi, Jeff and SeanThanks for your suggestions, I also think there is something wrong with the CAD model I am using, I will contact the manufacturer to get accurate Powell prism data. Later I have new progress I will share the results.
Dear Jeff,Thank you for your reply,I can't use Thorlabs' Powell lens because their input beam diameter is too small and may be damaged when I use them for high power laser applications. I tried to reduce the diameter of the input beam to about 1mm . Although the energy at both ends of the line spot is decrease, the uniformity of the center energy is worse.But if i just change the source from a source Gaussian to a source point, and the energy distribution of the line spot looks ok. Does it mean that the Powell lens I chose is not suitable for Gaussian laser applications? Powell Prism address of my choice:https://laserlineoptics.com/powell_primer.html
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