Phonon Laser Action in a Tunable Two-Level System

Abstract

The phonon analog of an optical laser has long been a subject of interest. We demonstrate a compound microcavity system, coupled to a radio-frequency mechanical mode, that operates in close analogy to a two-level laser system. An inversion produces gain, causing phonon laser action above a pump power threshold of around 50 µW. The device features a continuously tunable, gain spectrum to selectively amplify mechanical modes from radio frequency to microwave rates. Viewed as a Brillouin process, the system accesses a regime in which the phonon plays what has traditionally been the role of the Stokes wave. For this reason, it should also be possible to controllably switch between phonon and photon laser regimes. Cooling of the mechanical mode is also possible. [10]. However, only recently has phonon laser action been reported using a harmonicallybound magnesium ion [11]. Here, using a compound microcavity system, a phonon laser that operates in close analogy to a two-level laser system is demonstrated. The approach uses intermodal coupling induced by radiation pressure [12], and can also provide a spectrally selective means to detect phonons. Moreover, there is currently great interest in optomechanical cooling [13] and evidence of intermodal cooling is observed.

Cavity optomechanics with ultrahigh-Qcrystalline microresonators

“…The crystalline resonators can also operate in the novel regime where despite high mechanical Qfactor (> 1000) the mechanical dissipation rate Γ m can exceed κ. Pumping the cavity on the upper sideband would lead to optical gain and eventually the emission of a Stokes wave at a frequency of ω − Ω m . In this regime, the analogon of an optomechanical Brillouin laser can be realized, as recently analyzed [25].…”

“…The large sideband factors achieved here are of interest for a variety of experimental schemes, such as sideband cooling [9], back action evading measurements [23] as well as strong optomechanical coupling [24]. Moreover the demonstrated systems are the first to operate in a novel regime in which mechanical dissipation can exceed optical dissipation, enabling observation of optomechanical Brillouin lasing [25].…”

Amplified spontaneous emission of phonons as a likely mechanism for density-dependent velocity saturation in GaN transistors

“…One way to determine saturation velocity would be to perform full Monte-Carlo simulations [20] v n that are very close to the data obtained in [5]. The "clamping" of drift velocity above threshold is strikingly similar to the clamping of population inversion in lasers; hence one may refer to the mechanism responsible for the velocity saturation as "phonon lasing" [21,22].…”

“…where q n is the equilibrium phonon occupational number at a given lattice temperature, and the rate of spontaneous emission is Therefore, as the bias increases all the additional power transferred from the field to the electrons will be very efficiently transferred to the LO phonons via a stimulated emission process, and the drift velocity will be clamped at the threshold value exactly as the population inversion in the laser is clamped at the threshold [23]; hence it is tempting to refer to this process as "phonon lasing" [21,22]. The major difference from an optical laser is of course the absence of the resonant cavity providing feedback and selecting a single resonant mode.…”

Reservoir engineering and dynamical phase transitions in optomechanical arrays

“…Over the past years, this coupling has been successfully employed to cool mechanical systems close to the quantum ground state [19][20][21][22][23], using techniques analogous to laser cooling of atoms. In parallel, rapid progress in the fabrication and control of OMS, and in particular new designs for microscale and nanoscale devices [20,21,24,25], have led to a drastic improvement of OMS and pave the way for realizing various strongly coupled [26][27][28] and multimode [29][30][31][32][33][34][35] scenarios. Here, we describe the appearance of dissipation processes in extended OM arrays, where in contrast to OM laser cooling, now the mechanical systems provide a decoherence channel for light.…”