Laser Cooling of a Nanomechanical

Oscillator Jasper Chan et. al.

Presented by: Clinton Potts

Overview

Experimental Motivation

Optomechanics

Sideband Cooling

Nanomechanical Oscillator

Measurement Technique

Results

Future Work 2

Experimental Motivation

Observe quantum mechanical behavior in a mesoscopic system

Mesoscopic Billions of atoms

Similar work performed using cryogenic cooling techniques

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Solely cryogenic cooling not realizable for many devices

~ OConnell, Nature 464, 697-703 (2010)

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Optomechanics

Crookes radiometer

Photons carry momentum

Radiation Pressure

High finesse cavities increase momentum transfer

Optical field couples to the mechanical motion

Markus Aspelmeyer, Cavity Optomechanics (2013)

www.envirogadget.com

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Optical Resonator

High population of photons at resonant frequency Population quickly drops off

Optical decay rate - Related to Finesse

Markus Aspelmeyer, Cavity Optomechanics (2013)

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Optomechanical Resonator

Optical Cavity consists two mirrors

Fixed Mirror

Movable mirror attached to Spring

Movable mirror act as simple harmonic oscillator

Motion described by phonons

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Sideband Cooling

Non-Sideband Resolved

>

Sideband Resolved

<

7 Markus Aspelmeyer, Cavity Optomechanics (2013)

=

Phonon-Photon Interactions

Three processes possible

Photon Absorption (Grey)

Phonon Creation (Red, Stokes)

Phonon Annihilation (Blue, Anti-Stokes)

Markus Aspelmeyer, Cavity Optomechanics (2013)

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Ground State Cooling

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To maximize Anti-Stokes scattering

= High Density of States within cavity

Low Density of States outside cavity

=

Markus Aspelmeyer, Cavity Optomechanics (2013)

Nano-Mechanical Device

Silicon Nanobeam

Device pre-cooled to 20K

Laser coupled via tapered fiber

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Measurement and Results

=

(()2+(

2 )2)

Average number of phonons

Total mechanical damping rate

Measured from transmitted drive laser

Phonon number determined via curve fitting

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Measurement and Results

= . .

Average number of Phonons

Cooling limited by increased bath temperature

Due to high intensity field

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Going Forward

Not a true quantum mechanical measurement Classical measurement of quantum system

Measured average number of phonons Detection of discrete phonon values more direct proof of quantum mechanics

Markus Aspelmeyer, Cavity Optomechanics (2013)

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Questions

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