Optomechanics in a GaAs Vertical Cavity for sub-THz Phonons and NIR Light

A. FAINSTEIN, N. D. LANZILLOTTI-KIMURA, B. JUSSERAND, AND B. PERRIN

Creta

Congreso; Physics of Light-Matter Coupling in Nanostructures 2013? (PLMCN14); 2013

Exposición invitada. Optomechanics in a vertical GaAs/AlAs microcavity for sub-THz vibrations and NIR light A. Fainstein1, N. D. Lanzillotti-Kimura1, B. Jusserand2 and B. Perrin 2 1Instituto Balseiro & Centro Atómico Bariloche, C.N.E.A., R8402AGP Bariloche, RN, Argentina 2Institut des Nanosciences de Paris, UMR 7588 C.N.R.S. - UPMC 75005 Paris, France We propose a new and different approach to cavity optomechanics. The studied devices are based on the semiconductor vertical microcavity structures developed to demonstrate single-photon emitters, and vertical cavity surface emitting lasers (VCSELs). We show that, for the GaAs/AlAs family of materials a resonator structure based on distributed Bragg reflectors (DBRs), and designed to confine photons (i.e., an optical microcavity), efficiently confines acoustic phonons of the same wave-length, strongly enhancing their interaction. Indeed, a ?magic coincidence? determines that the materials index of refraction, mass density, and sound speed, the physical quantities that determine the optical and acoustic device performance, are such that precisely the same structure designed to optimally confine light with the largest optical Q-factor (that is, field amplification) will optimally confine the phonons with the largest attainable acoustic Q-factor (that is, resonant displacement and strain). We study the impulsive generation of intense coherent and monochromatic acoustic phonons in a planar /2 GaAs-spacer vertical microcavity with DBRs made of Al0.18Ga0.82As /AlAs, by following the time evolution of the elastic strain in picosecond-laser experiments. Efficient optical detection is assured by the strong phonon backaction on the high-Q optical cavity mode. The experiments demonstrate that these structures constitute optomechanical devices that can attain very high mechanical and optical Q-factors (Q ~ 105), very low mechanical effective masses (meff ~ pg), large optomechanical coupling factors (gom ~ THz/nm), and ultra-high vibrational frequencies (sub-THz). Based on the demonstrated record optomechanical coupling in the planar GaAs/AlAs cavity structures, we analyze a proposal to use them for the stimulated emission of sound (?saser?). We predict that such stimulated emission should occur in pillars of few-micrometer diameter under laser pump powers in the micro-milliWatt range. One could thus envision a microcavity operating simultaneously as a VCSEL that could provide the required photons under electronic injection. The studied planar microcavities based on DBRs can be designed so that, even with almost perfect mirrors, the phonon extraction out of the cavity is highly efficient. These characteristics make the proposed structures very attractive for the study of novel optomechanical and optoelectronic phenomena, and for the demonstration of sub-THz saser action by parametric instability. [1] A. Fainstein et al., Phys. Rev. Lett. 110, 037403 (2013)