 Laser Interferometry
Price: Item discontinued, no longer for sale ....
Laser Interferometry is a mainstay of modern physics, belonging in every physics teaching lab. With
this experiment, students assemble and align the interferometer
themselves, learning about modern optical components, mounting
hardware, and alignment procedures. They observe the
interferometer fringes first hand (e.g. the image at right), plus
they send the beam to a photodetector, modulate the position of one
mirror using a piezoelectric transducer, and then observe the
interferometer fringes on the oscilloscope, connecting the
visible fringes to an electronic signal.
The interferometer
signal is then fed back to the mirror to lock the interferometer at its
most sensitive point. From there students can modulate the mirror
position at high frequencies (while maintaining the lock at low
frequencies), thereby observing the modulated signal on the
oscilloscope. By using a series of signal averaging techniques
(including a built-in basic lock-in amplifier), students can observe
picometer displacements with this instrument -- 1/100th of an atom!
This is over a 10-cm-long arm length, which is like measuring the
distance from New York to Los Angeles with a sensitivity of the width
of a human hair!
The Laser Interferometer package also includes
a mirror mounted to a mechanical oscillator, essentially one arm of a
tuning fork. Students can use their interferometer to observe
nanometer motions of this oscillator, thus characterizing its
properties. In this way students see how laser interferometry can
be used as an effective tool for making precision displacement
measurements.
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