{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

WaveOpt_21

# WaveOpt_21 - Department of Electrical and Computer...

This preview shows pages 1–12. Sign up to view the full content.

Department of Electrical and Computer Engineering ECSE 527 Optical Engineering Diffraction References: Hecht ‘Optics’ Ch 10 References: Hecht Optics Ch. 10 Goodman ‘Introduction to Fourier Optics’ Andrew Kirk 2010 Diffraction 1

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Wave and ray optics Geometrical optics assumes that the wavelength is zero A lt As a result – Rays travel in straight lines unless they reflect or refract – Light can be perfectly collimated – Light can be focused to an infinitely small spot This is of course not true ! •We already have the Gaussian beam model for beam diffraction We already have the Gaussian beam model for beam diffraction In this module we will further investigate the wave nature of light and see the way that apertures cause light to diffract and spread. ©AGK 2010 Diffraction 2
Aspects of wave optics • Diffraction – Waves diverge after passing through an aperture – Periodic structures diffract light to produce a periodic diffraction pattern – Gaussian beams are a simple approximation of diffraction • Interference – Waves can combine in and out of phase – Results in bright and dark intensity fringes • Polarization ©AGK 2010 Diffraction 3

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Contents Review of scalar wave equation Origin of Rayleigh Somerfeld equation Diffraction integrals: Near field, Fresnel and Fraunhofer regimes Brief overview of Fresnel diffraction from edges and apertures Fraunhofer diffraction from square and circular apertures Limits to resolution of optical systems ©AGK 2010 Diffraction 4
Learning outcomes After taking this class you will be able to: E l i th diff b t 3 diff ti i Explain the difference between 3 diffraction regimes Determine when to use which regime Sketch typical Fresnel diffraction patterns (no calculation) Calculate Fraunhofer diffraction of rectangular and circular apertures ©AGK 2010 Diffraction 5

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Diffraction • Ray optics – ignored diffraction • Diffraction theory: study of wavefront propagation, through space and through apertures and periodic structures • It is important to know what approximations we can make in different situations Region of interest ©AGK 2010 Diffraction 6 Aperture Wavelength
Examples Fresnel diffraction Short distance Screen Knife edge Long distance Rectangular aperture ©AGK 2010 Diffraction 7 Photos from Hecht ‘Optics’ Fraunhofer diffraction

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Effect of increasing distance 0 06 0.08 0.1 16 z=160 0.25 0.3 0.35 4 z=40 0.015 0.02 64 z=640 100 200 300 400 500 0.02 0.04 0.06 100 200 300 400 500 0.05 0.1 0.15 0.2 100 200 300 400 500 0.005 0.01 z d 0 15 0.175 8 z=80 0.05 32 z=320 0.005 128 z=1280 0 025 0.05 0.075 0.1 0.125 0.15 0.01 0.02 0.03 0.04 0.001 0.002 0.003 0.004 ©AGK 2010 Diffraction 8 d=100, =10 100 200 300 400 500 0.025 100 200 300 400 500 100 200 300 400 500
Effect of decreasing aperture size =1 d z=1000 256 128 64 32 16 8 0 0008 0.00004 0.00005 0.00006 0.0008 0.0008 0.00001 0.00002 0.00003 ©AGK 2010 Diffraction 9 250 500 750 1000 1250 1500

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Other examples • For a Java diffraction simulation on the web: http://www.falstad.com/diffraction/ ©AGK 2010 Diffraction 10
Huygen’s principle Christiaan Huygens (1629 1695) • Huygen’s principle: each point on a wavefront • Huygen s principle: each point on a wavefront

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### What students are saying

• As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

Kiran Temple University Fox School of Business ‘17, Course Hero Intern

• I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

Dana University of Pennsylvania ‘17, Course Hero Intern

• The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

Jill Tulane University ‘16, Course Hero Intern