![]() ![]() If one of the mirrors is tilted slightly, then a spatial interference pattern is formed at the output. So, I assume you are interested in understanding the impact of temporal coherence (due to the laser’s finite bandwidth) on the properties of an interferogram formed with a Michelson interferometer? With a perfectly aligned Michelson, the output is a beam with uniform contrast. Of course a perfectly monochromatic beam is both temporally and spatially coherent as the field fluctuations at any point in the beam are sinusoidal. More specifically, at any point on a transverse plane the field fluctuations may appear chaotic, due to the finite spectral bandwidth, but these field fluctuations are highly correlated with those at any other point on the plane, hence high spatial coherence. Let me know if you have any more questions! :)Ī laser beam is typically spatially coherent. This method, although sometimes high sampling to wavelength spectrum is needed, gives better image with fewer noise. The random method used by built-in method usually gives noisy result.The built-in method consider a uniform distributed spectrum and this method use Gaussian distribution, which is more realistic for a laser source.I actually haven’t checked literatures for the built-in one, but I think there should be some too. For example, I mainly read the following documents and made this method. More literatures support this alternative method.The more the accurate but slower the ray-tracing. spect_samp is the sampling points you want to use to sample the spectrum. wave_center is the center of the Gaussian distributed source spectrum.Ħ. wave_FWHM is the full width at half maximum of the Gaussian distributed source spectrum.ĥ. n_smooth works same as the Smooth parameter you see in the Detector Viewer.Ĥ. It’s suggested you exactly specify this instead of leave it “0”.ģ. wavenum is the Wavenumber you used for your source parameter. detnum is the object # of the Detector Rectangle you want to observe the interference pattern.Ģ. If you use this example code with your own system, you at least should check and modify the following 6 variables.ġ. The Interactive Extension Mode can be turned on as shown below. We just set it to zero to turn the function off. Note, in this method, we don’t use the Coherence Length settings. To see how it works, users just need to open the attached ZAR file, turn on Interactive Extension Mode, and run the attached MATLAB code. Here we provide a simple case and an ZOS-API code to demonstrate how to do it. To calculate the interference pattern of each wavelength and incoherently sum them, we need to do it manually. However, the interference pattern cannot be detected because the pattern changes with very high frequency and vanishes when sensor averages it over time. In fact, light with different wavelength could interfere. In other words, the interference pattern of a multi-wavelength source is the incoherent sum of the interference pattern of each wavelength themselves. In this method, it’s assume light with different wavelength cannot interfere. In this post, an another method is demonstrated for simulating coherence length. This works based on randomizing the wavelength of each ray. ![]() In OpticStudio, an option is available for assigning Coherence Length to a source as shown below. ![]()
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