Video Demonstrations in Lasers and Optics

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This section contains demonstrations used to illustrate the theory and applications of optics. Some of the topics superbly treated in Prof. Shaoul Ezekiel's Demonstrations in Lasers and Optics videos include light polarization, reflections at boundaries, Brewster's angle, critical angle, Fraunhofer diffraction from slits, optical fibers, and lasers. In addition to presentation of Prof. Ezekiel's video segments in lectures and recitations, students viewed segments of Prof. Ezekiel's Optics videos. Homework problems based on phenomena in the videos were also prepared and assigned.

TOPICS DESCRIPTIONS VIDEOS
Overview of demonstrations in lasers and optics Streaming: (RM - 56K)
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I. Demonstrations in physical optics
Optics: polarization of light and polarization manipulation
Linear polarizer

Description of a linear polarizer

Use of a linear polarizer to analyze the state of polarization of light from a laser

Demonstration of the change in the state of polarization of light after reflection by two aluminum coated mirrors

Use of a linear polarizer to set the state of polarization of light

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Polarization rotation using polarizers

Rotation of the plane of polarization of light using a single linear polarizer

Limitation of the single polarizer method

Rotation of the plane of polarization using two linear polarizers

Effect of polarization rotation on transmitted intensity

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Quarter-wave plate

Description of a quarter-wave plate

Use of a quarter-wave plate to change the state of polarization of light, e.g., from linear to elliptical (or to circular) polarization

Demonstration that there is no change in the state of polarization when propagating along either principal axis of the quarter-wave plate

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Half-wave plate

Description of a half-wave plate

Use of a half-wave plate to rotate the plane of polarization from zero to ninety degrees with very little loss

Demonstration that there is no change in the state of polarization when propagating along either principal axis of the half-wave plate

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Optical isolator

Need for an optical isolator

Demonstration of the performance of an optical isolator using a quarter-wave plate and a linear polarizer

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Scattered light in a dielectric

Propagation of linearly polarized light in a dielectric (Lucite) rod

Observation of Rayleigh scattered light within rod

Demonstration that the state of polarization of the scattered light is the same as that of the incident light

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Optics: reflection at dielectric interfaces
Reflection at the air-glass boundary

Reflection and transmission of light at an air-glass boundary as a function of the angle of incidence (0-90º) for different states of polarization of the incident light

Demonstration of Brewster's angle

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Reflection at the glass-air boundary

Reflection and transmission at a glass-air boundary as a function of angle of incidence (0-90º) for different states of polarization of the incident light

Demonstration of the critical angle

Demonstration of the propagation of the transmitted beam along the boundary at the critical angle

Demonstration of Brewster's angle

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Phase shifts in total internal reflection

Demonstration of the absence of any change in the state of polarization of the reflected and transmitted light at a glass-air boundary below the critical angle

Demonstration of the change in the state of polarization of reflected light at a glass-air boundary above the critical angle, i.e., in total internal reflection

Application of this effect to making quarter-wave and half-wave plates

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Optics: two-beam interference
Two-beam interference — collimated beams

Demonstration of two-beam interference using collimated beams in a Michelson interferometer

Demonstration of various fringe patterns as a function of the alignment of the interferometer mirrors

Effect of mirror translation on fringe pattern using a piezoelectric driver

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Two-beam interference — diverging beams

Demonstration of two-beam interference using diverging beams in a Michelson interferometer

Demonstration of various fringe patterns as a function of the alignment of the interferometer mirrors

Change in fringe pattern as a function of path length difference

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Destructive interference — Where does the light go?

Demonstration of constructive and destructive interference in a Michelson interferometer using diverging beams

Demonstration of complete destructive interference between the two beams leaving the interferometer for equal path lengths

Where does the light go in destructive interference?

Demonstration that there is light in each arm of the interferometer in destructive interference

Demonstration of light reflected back toward source simultaneously with light transmitted from interferometer for equal paths and also for unequal paths of the interferometer

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Fringe contrast — vibrations

Demonstration of two-beam interference in a Michelson interferometer with collimated beams

Effect of vibrations on fringe contrast

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Fringe contrast — intensity ratio

Demonstration of two-beam interference in a Michelson interferometer with collimated beams

Effect of intensity difference between interfering beams on fringe contrast

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Fringe contrast — polarization difference

Demonstration of two-beam interference in a Michelson interferometer with collimated beams

Determination of the state of polarization in each arm of the interferometer

Demonstration of the rotation of the plane of polarization in one arm of the interferometer using a quarter-wave plate

Demonstration of the effect of polarization difference on fringe contrast, showing zero contrast for orthogonal polarizations

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Fringe contrast — path difference

Demonstration of two-beam interference in a Michelson interferometer with collimated beams

Demonstration of the effect of path length difference (0-100 cm) on fringe contrast

Demonstration of the spectrum of the light source, in this case, a multilongitudinal mode He-Ne laser

Relationship between fringe contrast, path length difference, and spectrum of the light source

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Coherence length and source spectrum

Demonstration of two-beam interference in a Michelson interferometer with collimated beams

Demonstration of fringe contrast with path length difference for a single-frequency laser light source

Demonstration of fringe contrast with path length difference for two- and three-frequency laser light sources

Relationship between fringe contrast and coherence length

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Optics: multiple beam interference
Plane mirror cavity — collimated beams

Demonstration of multiple beam interference using a plane mirror cavity in transmission with mirror separation of 3 mm and collimated incident beam

Observation of finesse, free spectral range, and effect of cavity misalignment

Demonstration of multiple beam interference in reflection using the same cavity

Simultaneous observation of multiple beam interference in transmission and in reflection

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Plane mirror cavity — diverging beams

Demonstration of multiple beam interference using a plane mirror cavity in transmission with a mirror separation of 3 mm and a diverging incident beam

Demonstration of multiple beam interference in reflection using the same cavity

Simultaneous observation of multiple beam interference in transmission and in reflection

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Curved mirror cavity — radial modes

Demonstration of multiple beam interference in transmission using a cavity with curved mirrors and a single-frequency laser light source

Observation of the intensity distribution associated with a variety of radial (or transverse) modes as a function of cavity tuning

Observation of the cavity transmission associated with radial modes as a function of cavity tuning

Demonstration of the properties of a confocal resonator, i.e., where the radius of curvature of each mirror is equal to the mirror separation

Demonstration of the behavior just below and just above the confocal condition

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Optical spectrum analyzer

Demonstration of the use of a confocal cavity for the spectral analysis of single-frequency laser

Demonstration of the use of a confocal cavity for the spectral analysis of multifrequency laser

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Optics: Fraunhofer and Fresnel diffraction
Fraunhofer diffraction — adjustable slit

Demonstration of Fraunhofer diffraction by a narrow slit

Demonstration of Fraunhofer diffraction by an adjustable narrow slit

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Fraunhofer diffraction — two slits

Demonstration of Fraunhofer diffraction by a single slit

Demonstration of Fraunhofer diffraction by pairs of 150 μm slits with spacings ranging from 150 μm to 2 mm

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Fraunhofer diffraction — multiple slits

Demonstration of Fraunhofer diffraction by a single slit

Demonstration of Fraunhofer diffraction by two slits

Demonstration of Fraunhofer diffraction by three slits

Demonstration of Fraunhofer diffraction by four, five, six, seven, eight, nine, and more slits

Demonstration of Fraunhofer diffraction by multiple slits with line spacings of 100 per inch, 200 per inch, 300 per inch, and 2000 per inch

Demonstration of Fraunhofer diffraction by multiple slits as a function of slit orientation

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Fraunhofer diffraction — thin wires

Demonstration of Fraunhofer diffraction by a thin wire

Demonstration of Fraunhofer diffraction by thin wires with different diameters

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Fraunhofer diffraction — rectangular aperture

Demonstration of Fraunhofer diffraction by a fixed rectangular aperture

Demonstration of Fraunhofer diffraction by an adjustable rectangular aperture

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Fraunhofer diffraction — circular apertures

Demonstration of Fraunhofer diffraction by a circular aperture

Demonstration of Fraunhofer diffraction by circular apertures with different diameters

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Fraunhofer diffraction — crossed multiple slits

Demonstration of Fraunhofer diffraction by fixed crossed multiple slits

Demonstration of Fraunhofer diffraction by crossed multiple slits as a function of the relative orientation of the slits

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Fresnel diffraction — adjustable slit

Demonstration of Fresnel diffraction by a fixed slit

Demonstration of Fresnel diffraction by an adjustable slit

Observation of the transition from Fresnel to Fraunhofer diffraction using an adjustable slit

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Fresnel diffraction — circular apertures

Demonstration of Fresnel diffraction by a circular aperture using a spatially filtered laser source

Demonstration of Fresnel diffraction by circular apertures with different diameters

Demonstration of Fresnel diffraction by a circular aperture as a function of source distance

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Optics: propagation in optical fibers
Single mode fiber

Demonstration of a single mode fiber and light coupling into the fiber

Demonstration of single mode transmission

Demonstration of the effect of stress and bends applied to fiber showing light expelled by fiber

Demonstration of the effect of bends and stress on single mode transmission

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Multi-mode fiber

Demonstration of light transmission through a multimode fiber, showing a variety of transverse modes

Demonstration of the effect of input alignment changes on transverse modes

Demonstration of the effect of fiber bends and stresses on transverse modes

Demonstration of single mode behavior in a multimode fiber using fiber bends to eliminate higher order transverse modes

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Polarization in a single mode fiber

Demonstration of single mode propagation in an optical fiber

Demonstration of the state of polarization of the light exiting the fiber as a function of stress and bends applied to the fiber

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II. Demonstrations in laser fundamentals
Laser fundamentals I
Simple laser

Introduction to lasers

Demonstration of a simple laser with internal mirrors

Demonstration of a laser with external mirrors, showing the effect of cavity misalignment

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Light amplifier

Demonstration of light amplification by an optical amplifier, using a He-Ne laser and a He-Ne amplifier tube

Demonstration of 6% amplification per pass

Calibration of detector using a fixed loss

Measurement of the effect of amplifier fluorescence on detector output

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Polarization of laser light

Demonstration of the state of polarization of a laser with external mirrors and the amplifier terminated with Brewster windows

Demonstration of the state of polarization of a laser with internal mirrors

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Spectrum of laser light

Demonstration of the spectrum of laser light from a He-Ne laser with external mirrors showing multiple frequencies associated with longitudinal modes of the cavity

Demonstration of the polarization of the multiple frequencies being identical

Demonstration of the effect of temperature, vibration, and misalignment of the spectrum of the laser output

Demonstration of the spectrum of laser light from a He-Ne laser with internal mirrors, showing multiple frequencies associated with longitudinal modes of the cavity

Demonstration of the polarization of the multiple frequencies from an internal mirror laser showing that adjacent modes are orthogonally polarized

Demonstration of single-frequency output by polarization selection

Demonstration of the effect of temperature on the spectrum of the laser output

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Light inside and light outside laser

Demonstration of light inside laser cavity being much stronger than light leaving the laser

Discussion of cavity dumping

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Laser fundamentals II
Optics of laser beams

Demonstration of an expanding beam from a laser

Demonstration of spatial filtering of a laser beam

Demonstration of laser-generated speckle patterns on screen

Visualization of laser beam propagating in a water tank

Visualization of focused laser beam in a water tank

Observation of the Rayleigh range

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Laser transverse modes

Demonstration of various transverse modes from a laser as a function of cavity alignment

Demonstration of the use of an intra-cavity adjustable aperture to control the number of transverse modes that can oscillate

Demonstration of the frequency spectrum of laser transverse modes

Demonstration of a method of isolating single transverse modes using a wire inside the laser cavity

Demonstration of the spectrum of isolated transverse modes

Demonstration of the change in orientation of a transverse mode

Demonstration of the effect of blocking one of the lobes of a two-lobe mode inside the laser cavity

Demonstration of the effect of blocking one of the lobes of a two-lobe mode outside the laser cavity

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Laser linewidth

Discussion of laser linewidth

Measurement of laser linewidth using an optical spectrum analyzer

Measurement of the fundamental laser linewidth using a two-frequency laser showing the intrinsic spectral width to be much less than 30 Hz

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Laser fundamentals III
Reflection back into laser

Demonstration of the intensity and spectrum of a single-frequency laser and a multifrequency laser

Demonstration of the effect of back reflection into the laser on the intensity and the spectrum of each laser

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High power argon laser

Demonstration of the operation on an argon ion laser

Demonstration of the high intensity in the argon laser beam by burning a hole in cardboard with an unfocused laser beam

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Multi-wavelength argon laser

Demonstration of the operation of an argon ion laser

Demonstration of simultaneous multiwavelength operation of an argon laser in the blue-green spectral range

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Single frequency argon laser

Demonstration of the operation of an argon ion laser

Demonstration of the broad spectrum from an argon laser using an optical spectrum analyzer

Demonstration of single-frequency operation using an intracavity etalon

Demonstration of the effect of etalon tuning on the single-frequency output of the laser showing mode hopping phenomena

Demonstration of the effect of aligning the intracavity etalon normal to the laser beam showing chaotic amplitude and frequency behavior

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Tunable dye laser

Demonstration of the operation of a cw dye laser pumped by an argon laser

Demonstration of the wide tuning capability of the dye laser from green to yellow to red

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Dye laser excitation of sodium

Demonstration of the excitation of atomic sodium in a heated cell by a tunable dye laser

Observation of intense radiation from the sodium vapor when the laser is on resonance with a ground state transition in sodium

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Dye laser induced fluorescence in iodine

Demonstration of fluorescence induced by a tunable dye laser in a cell of molecular iodine

Simultaneous display of the color of the dye laser and the color of the iodine fluorescence as a function of laser tuning showing large differences in color under certain conditions

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To obtain high quality versions of these demonstrations, visit Zeelase.

Recommended Citation

For any use or distribution of these materials please cite as follows:

Shaoul Ezekiel, Video Demonstrations in Lasers and Optics. (Massachusetts Institute of Technology: MIT OpenCourseWare). http://ocw.mit.edu (Accessed [Date]). License: Creative Commons Attribution-NonCommercial-Share Alike.