How does an optical spatial filter work?

on2t1inf8b 2022-07-20 Answered
How does an optical spatial filter work?
You can still ask an expert for help

Expert Community at Your Service

  • Live experts 24/7
  • Questions are typically answered in as fast as 30 minutes
  • Personalized clear answers
Learn more

Solve your problem for the price of one coffee

  • Available 24/7
  • Math expert for every subject
  • Pay only if we can solve it
Ask Question

Answers (1)

Bubbinis4
Answered 2022-07-21 Author has 8 answers
The principle behind the use of a pinhole in the way that you describe is simply to create a subresolvable source of light, thus destroying all wavefront information. You are correct that the exact diffraction pattern from a subresolvable point source is not Gaussian, but it is very nearly so and indeed Gaussian modes are the eigenfunctions of an approximation to the wave equation that holds for paraxial fields, i.e. fields of very small numerical aperture and with wave vectors all directed to within about 0.1 radians of the nominal beam propagation direction.
So in practice the beam will become more Gaussian after passage through a subresolvable pinhole, i.e. one of diameter that is smaller than approximately λ/NA, where NA is the beam's numerical aperture.
Not exactly what you’re looking for?
Ask My Question

Expert Community at Your Service

  • Live experts 24/7
  • Questions are typically answered in as fast as 30 minutes
  • Personalized clear answers
Learn more

You might be interested in

asked 2022-08-06
If we have two laser beams with central wavelengths λ 1 and λ 2 , (one with a spectral width of Δ λ 2 and one with negligible spectral width), interacting in a non-linear crystal, how would we calculate the spectral width of the difference-frequency-generated (DFG) output? I know it's a Lorentzian given by Δ λ = 4 λ 1 2 Δ λ 2 4 ( λ 2 λ 1 ) 2 Δ λ 2 2 . But I don't know how to prove this.
asked 2022-05-10
How do you calculate the absolute index of refraction?
asked 2022-05-13
How does the index of refraction relate to speed of light?
asked 2022-07-13
What is the angle of refraction (relative to the boundary normal) of a diamond in contact with water according to Snell's law? The indices of refraction for water and diamond are respectively 1.33 and 2.42.
asked 2022-05-10
Why does total internal reflection occur in a bicycle reflector?
asked 2022-07-23
Currently I have a gas with a density that follows and inverse square law in distance, r. Given that I know the mass attenuation coefficient of this gas, I wish to calculate an effective optical depth using a modified version of the Beer-Lambert Law that uses mass attenuation coefficients:
τ = α ρ g a s ( T ) l ρ = α M p ( T ) ρ R T 1 x 2 d x
Where α is the mass attenuation coefficient for the solid phase of the gas [cm 1 ], ρ is the mass density of the solid phase of the gas, l is the path length, M is the molar mass of the gas, p ( T )is the pressure of the gas as a function of temperature, R is the ideal gas constant and T is the temperature of the gas. ρ g a s is the mass density of the gas itself and can be extracted from the ideal gas law:
ρ g a s = p ( T ) M R T
The integral emerges from my attempt at rewriting the first equation for a non uniform attenuation, that I have here due to the inverse square law effecting the density of the gas.
However, I am now concerned that units no longer balance here since τ should be unitless. Can anyone help guide me here?
asked 2022-07-20
Does electromagnetic diffraction ever equal zero?

New questions