We demonstrate an optomechanical system employing a movable, micron-scale waveguide optically-coupled to a high-Q optical microresonator. We show that milliwatt-level optical powers create micron-scale displacements of the input waveguide. The displacement is caused by a cavity-enhanced optical dipole force (CEODF) on the waveguide, arising from the stored optical field of the resonator. The CEODF is used to demonstrate tunable cavity-waveguide coupling at sub-mW input powers, a form of all-optical tunable filter. The scaling properties of the CEODF are shown to be independent of the intrinsic Q of the optical resonator and to scale inversely with the cavity mode volume.Although light is usually thought of as imponderable, carrying energy but relatively little momentum, light can exert a large force per photon if confined to small structures. Such forces have recently been proposed 1,2 as a means to construct novel optomechanical components such as tunable filters, couplers, and lasers. Other theoretical studies of the nonlinear dynamics of these systems have shown them to be useful for performing optical wavelength conversion and efficient optical-to-mechanical energy conversion 3,4 . In the field of quantum physics, there has also been recent interest in using radiation pressure forces within micro-optomechanical resonators to help cool macroscopic mechanical oscillators to their quantum-mechanical ground state 5,6,7,8 . Here, we demonstrate an optomechanical system employing a movable, micron-scale waveguide optically-coupled to a high-Q optical microresonator. We show that milliwatt-level optical powers create micron-scale displacements of the input waveguide. The displacement is caused by a cavity-enhanced optical dipole force (CEODF) on the waveguide, arising from the stored optical field of the resonator. The CEODF is used to demonstrate tunable cavity-waveguide coupling at sub-mW input powers, a form of all-optical tunable filter. Finally, the scaling properties of the CEODF are shown to be independent of the intrinsic Q of the optical resonator, and to scale inversely with the cavity mode volume, indicating that such forces may become even more effective as devices approach the nanoscale.The ponderomotive effects of light within optical resonators have long been considered in the field of high-precision measurement 9 . The canonical system, shown in Fig. 1a, consists of a Fabry-Perot (FP) resonant cavity formed between a rigid mirror and a movable mirror attached to a spring or hung as a pendulum 10 . A nearly-resonant optical field builds up in amplitude as it bounces back-and-forth between the mirrors and pushes on the movable mirror with each reflection, which detunes the FP cavity. The nonlinear dynamics associated with the displacement of the mirror and the build-up of internal cavity energy result in an "optical spring" effect 11 . Under conditions in which the optical field cannot adiabatically follow the mirror movement, the radiation pressure force can drive or dampen oscillations of the positi...

Recent advances in thermal management and improvements in fabrication and facet passivation enabled extracting unprecedented optical powers from laser diodes (LDs). However, even in the absence of thermal roll-over or catastrophic optical damage (COD), the maximum achievable power is limited by optical non-linear effects. Due to its non-linear nature, two-photon absorption (TPA) becomes one of the dominant factors that limit efficient extraction of laser power from LDs. In this paper, theoretical and experimental analysis of TPA in high-power broad area laser diodes (BALD) is presented. A phenomenological optical extraction model that incorporates TPA explains the reduction in optical extraction efficiency at high intensities in BALD bars with 100µm-wide emitters. The model includes two contributions associated with TPA: the straightforward absorption of laser photons and the subsequent single photon absorption by the holes and electrons generated by the TPA process. TPA is a fundamental limitation since it is inherent to the LD semiconductor material. Therefore scaling the LDs to high power requires designs that reduce the optical intensity by increasing the mode size.

Chip-based cavity quantum electrodynamics (QED) devices consisting of a self-assembled InAs quantum dot (QD) coupled to a high quality factor GaAs microdisk cavity are coherently probed through their optical channel using a fiber taper waveguide. We highlight one particularly important aspect of this all-fiber measurement setup, which is the accuracy to which the optical coupling level and optical losses are known relative to typical free-space excitation techniques. This allows for precise knowledge of the intracavity photon number and measurement of absolute transmitted and reflected signals. Resonant optical spectroscopy of the system under both weak and strong driving conditions are presented, which when compared with a quantum master equation model of the system allows for determination of the coherent coupling rate between QD exciton and optical cavity mode, the different levels of elastic and inelastic dephasing of the exciton state, and the position and orientation of the QD within the cavity. Pump-probe measurements are also performed in which a far offresonant red-detuned control laser beam is introduced into the cavity. Rather than producing a measurable ac-Stark shift in the exciton line of the QD, we find that this control beam induces a saturation of the resonant system response. The broad photoluminescence spectrum resulting from the presence of the control beam in the cavity points to sub-bandgap absorption in the semiconductor, and the resulting free-carrier generation, as the likely source of system saturation.

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