Acoustic Phonon Emission from a Weakly Coupled Superlattice under Vertical Electron Transport: Observation of Phonon Resonance

Abstract

We report measurements of acoustic phonon emission from a weakly coupled AlAs/GaAs superlattice (SL) under vertical electron transport. The phonons were detected using superconducting bolometers. A peak (resonance) was observed in emission parallel to the SL growth axis when the electrical energy drop per SL period matched the energy of the first SL mini-Brillouin zone-center phonon mode. This peak was mirrored by an increase of the differential conductance of the SL. These results are evidence for stimulated emission of terahertz phonons as previously predicted theoretically and suggest that such a SL may form the basis of a SASER (sound amplification by stimulated emission of radiation) device.

Phonon Laser Action in a Tunable Two-Level System

“…Cooling of the mechanical mode is also possible. [10]. However, only recently has phonon laser action been reported using a harmonicallybound magnesium ion [11].…”

“…-The possibility of phonon laser action has been considered in a wide range of physical systems including ions [1], semiconductors [2], nanomechanics [3], nanomagnets [4] and others [5]. Observations of phonon stimulated emission have been reported in cryogenic Al 2 O 3 :Cr 3+ [6,7,8] and Al 2 O 3 :V 4+ [9] as well as semiconductor superlattices [10]. However, only recently has phonon laser action been reported using a harmonicallybound magnesium ion [11].…”

Acoustic gain in piezoelectric semiconductors atɛ-near-zero response

“…There are other methods for obtaining acoustic gain, such as parametric amplification in a magnetostrictive solid [17]. Furthermore, we stress that amplification of sound has also been reported in nonclassical systems, giving rise to phonon lasing and amplification in Stark ladder superlattices [18][19][20]. The present idea, based on the piezoelectric effect that exists in a large class of semiconductors where the unit cell is inversion asymmetric, does not require direct excitation of photons.…”

A GaAs/AlAs superlattice as an electrically pumped THz acoustic phonon amplifier

“…There has been an effort over the last few years to create acoustic analogues of active optical devices [12,13], such as lasers and optical amplifiers, which may provide a highly efficient source of THz sound. As well as investigations into the active components of such structures, it has also been shown [14] that high Q THz acoustic cavities can provide efficient confinement of sound at selected frequencies.…”