Integrated III-V Photonic Crystal – Si waveguide platform with tailored optomechanical coupling

Abstract

Optomechanical systems, in which the vibrations of a mechanical resonator are coupled to an electromagnetic radiation, have permitted the investigation of a wealth of novel physical effects. To fully exploit these phenomena in realistic circuits and to achieve different functionalities on a single chip, the integration of optomechanical resonators is mandatory. Here, we propose a novel approach to heterogeneously integrate arrays of two-dimensional photonic crystal defect cavities on top of silicon-on-insulator waveguides. The optomechanical response of these devices is investigated and evidences an optomechanical coupling involving both dispersive and dissipative mechanisms. By controlling the optical coupling between the waveguide and the photonic crystal, we were able to vary and understand the relative strength of these couplings. This scalable platform allows for an unprecedented control on the optomechanical coupling mechanisms, with a potential benefit in cooling experiments, and for the development of multi-element optomechanical circuits in the framework of optomechanically-driven signal-processing applications.

External Control of Dissipative Coupling in a Heterogeneously Integrated Photonic Crystal—SOI Waveguide Optomechanical System

“…For the mechanical mode at Ω m /2π we observe the optical spring effect: the mechanical mode amplitude S P (Ω m ), linewidth and frequency Ω m are modified when the laser probe is swept across the cavity optical resonance [6]. Concerning the modulation peak, it does not come from direct modulation of the probe laser carrier, but is transferred to it via the QD layer.…”

“…Dissipative optomechanical coupling consists in the modulation of the lifetime of the cavity photons through the motion of a mechanical oscillator. Very recently, this effect has been observed in a wide variety of devices [2][3][4][5][6][7]. Dissipative coupling may significantly enhance the detection sensitivity in optomechanically-based sensing schemes [8,9].…”

“…In our recent work [6], we reported on tailored dispersive and dissipative optomechanical couplings for the flexural mechanical modes of our devices. Here we investigate the impact of the embedded active medium on the optomechanical coupling by using an external modulation of the pump laser.…”

“…We have used an analytical model, describing this phenomenon by considering the impact of dissipative, intrinsic dispersive and external dispersive optomechanical couplings, with coupling coefficients g ω , g κ,i and g κ,e , respectively [3,6]. The fitting procedure follows the one described in [6]: we took as initial guess the experimental coupling coefficients, measured for the fundamental mode and same access waveguide geometry in the absence of an external pump [6]. Subsequently, we let all the three coefficients free.…”

“…Moreover, it could open new possibilities in the optomechanical control of systems featuring both types of coupling mechanisms [10,11], where a tailored coupling strength is highly desirable. Such tailoring was demonstrated using external [3] or integrated [6] variation of the geometry of the optical access channel to the nanocavity. These demonstrations, however, were based on the simultaneous modification of both types of couplings.…”