Download
1 / 23
250 likes | 485 Vues
16.711 Lecture 1 Review of Wave optics. Today. Introduction to this course Light waves in homogeneous medium Monochromatic Waves in inhomogeneous medium Polychromatic waves Multiple interference and optical resonator Diffraction principle and diffraction grating .
E N D
16.711 Lecture 1 Review of Wave optics Today • Introduction to this course • Light waves in homogeneous medium • Monochromatic Waves in inhomogeneous medium • Polychromatic waves • Multiple interference and optical resonator • Diffraction principle and diffraction grating
16.711 Lecture 1 Review of Wave optics Syllabus and policy of the course • Syllabus, course materials, schedules are available on the course website: • http://faculty.uml.edu/xlu/16.711 Course contents: • Introduction of the course, reviews of Wave Optics • Dielectric waveguides and optical fibers, mode and effective index • Optical Fiber modal and wavdguide dispersions, dispersion management • Mode-coupling theory, Mach-zehnder interferometer, Directional coupler, taps and WDM coupler • Electro-optics, polarization and modulation of lights • Optical Amplifiers. noise figure, gain profile, ASE noise. Gain equalization, optical filter, bit error rate, amplifier cascade • DWDM technology, Gratings, AWG, Fiber Bragg grating • Photonic switches and all optical switches • Nonlinear Fiber optics
16.711 Lecture 1 Review of Wave optics Light waves in homogeneous medium • The Helmholtz equation Helmholtz equation • Plane electromagnetic wave
16.711 Lecture 1 Review of Wave optics Light waves in homogeneous medium • The spherical wave • The Gaussian wave
16.711 Lecture 1 Review of Wave optics • The Gaussian wave
16.711 Lecture 1 Review of Wave optics • Power of a Gaussian beam Total Power: The ratio of the power carried within a circle of radius : The power contained within a circle of radius 86% of the total power. 99% of the total power is contained within a circle of radius .
16.711 Lecture 1 Review of Wave optics • Beam radius of a Gaussian beam is the spot size. is the waist radius. when 86% energy is confined in the cone.
16.711 Lecture 1 Review of Wave optics • depth of focus is the spot size. is the waist radius. The gaussian has minimum width at . The axial distance for the beam width is called depth of focus.
16.711 Lecture 1 Review of Wave optics Monochromatic waves in inhomogeneous medium • Fresnel’s equations:
16.711 Lecture 1 Review of Wave optics Monochromatic waves in inhomogeneous medium • Fresnel’s equations: The Fresnel’s equations is derived from the boundary conditions. • phase change: when : At normal incidence, no phase shift if n1>n2, 180 phase shift if n2>n1.
16.711 Lecture 1 Review of Wave optics Monochromatic waves in inhomogeneous medium • General case: • polarization angle or Brewster’s angle : At The reflected wave is linear polarized.
16.711 Lecture 1 Review of Wave optics Monochromatic waves in inhomogeneous medium • Total internal reflection The amplitude of the reflected wave is 1. At The phase of the reflected wave changes with the incident angle.
16.711 Lecture 1 Review of Wave optics Monochromatic waves in inhomogeneous medium • Total internal reflection and evanescent wave • Evanescence wave: • penetration depth:
16.711 Lecture 1 Review of Wave optics Monochromatic waves in inhomogeneous medium • Reflectance and Transmittance • normal incidence:
16.711 Lecture 1 Review of Wave optics Polychromatic waves • group velocity wave packet speed: is called group index. Exercise: the difference between phase velocity and group velocity?
16.711 Lecture 1 Review of Wave optics Polychromatic waves • absorption and dispersion is the absorption or attenuation coefficient. a wave packet broadening for a length of L is: dispersion parameter:
16.711 Lecture 1 Review of Wave optics Polychromatic waves • classical picture of the susceptibility: classical electron moving equation:
16.711 Lecture 1 Review of Wave optics Multiple interference and optical resonator • interference of monochromatic waves : • interferometers Mach-zehnder Sagnac Michelson
16.711 Lecture 1 Review of Wave optics Multiple interference and optical resonator • interference of two oblique plane waves : • exercise: interference of a plane wave and spherical wave
16.711 Lecture 1 Review of Wave optics Multiple interference and optical resonator • interference of two monochromatic waves – light beating • multiple interference
16.711 Lecture 1 Review of Wave optics Multiple interference and optical resonator • spectral width, finesse, Diffraction principle and diffraction grating • Fraunhofer diffraction
inside the aperture outside the aperture 16.711 Lecture 1 Review of Wave optics Diffraction principle • The Fourier optics view of Fraunhofer diffraction In far fields, the spatial frequency is transferred to position.
16.711 Lecture 1 Review of Wave optics Diffraction grating • Transmission grating • Reflection grating
