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Register a new userInduced transparency in optomechanically coupled resonators
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In this work we theoretically investigate a hybrid system of two optomechanically coupled resonators, which exhibits induced transparency. This is realized by coupling an optical ring resonator to a toroid. In the semiclassical analyses, the system displays bistabilities, isolated branches (isolas) and self-sustained oscillation dynamics. Furthermore, we find that the induced transparency transparency window sensitively relies on the mechanical motion. Based on this fact, we show that the described system can be used as a weak force detector and the optimal sensitivity can beat the standard quantum limit without using feedback control or squeezing under available experimental conditions.
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Coherent interaction of laser radiation with multilevel atoms and molecules can lead to quantum interference in the electronic excitation pathways. A prominent example observed in atomic three-level-systems is the phenomenon of electromagnetically induced transparency (EIT), in which a control laser induces a narrow spectral transparency window for a weak probe laser beam. The concomitant rapid variation of the refractive index in this spectral window can give rise to dramatic reduction of the group velocity of a propagating pulse of probe light. Dynamic control of EIT via the control laser enables even a complete stop, that is, storage, of probe light pulses in the atomic medium. Here, we demonstrate optomechanically induced transparency (OMIT)--formally equivalent to EIT--in a cavity optomechanical system operating in the resolved sideband regime. A control laser tuned to the lower motional sideband of the cavity resonance induces a dipole-like interaction of optical and mechanical degrees of freedom. Under these conditions, the destructive interference of excitation pathways for an intracavity probe field gives rise to a window of transparency when a two-photon resonance condition is met. As a salient feature of EIT, the power of the control laser determines the width and depth of the probe transparency window. OMIT could therefore provide a new approach for delaying, slowing and storing light pulses in long-lived mechanical excitations of optomechanical systems, whose optical and mechanical properties can be tailored in almost arbitrary ways in the micro- and nano-optomechanical platforms developed to date.
In contrast to the optomechanically induced transparency (OMIT) defined conventionally, the inverse OMIT behaves as coherent absorption of the input lights in the optomechanical systems. We characterize a feasible inverse OMIT in a multi-channel fashion with a double-sided optomechanical cavity system coupled to a nearby charged nanomechanical resonator via Coulomb interaction, where two counter-propagating probe lights can be absorbed via one of the channels or even via three channels simultaneously with the assistance of a strong pump light. Under realistic conditions, we demonstrate the experimental feasibility of our model using two slightly different nanomechanical resonators and the possibility of detecting the energy dissipation of the system. In particular, we find that our model turns to be an unilateral inverse OMIT once the two probe lights are different with a relative phase, and in this case we show the possibility to measure the relative phase precisely.
Cavity optomechanical system can exhibit higher-order sideband comb effect when it is driven by a control field $omega_{c}$ and a probe field $omega_{p}$, and works in the non-perturbative regime, as was shown in a previous work [Xiong et al., Opt. Lett. 38, 353 (2013)]. The repetition frequency of such a comb is equal to the mechanical frequency $omega_{b}$ and is untunable, which limits the precision of the comb. Here we address this problem by driving the system with an additional strong probe field $omega_{f}$, and the detuning between $omega_{f}$ and $omega_{c}$ is equal to $omega_{b}/n$ (here $n$ is an integer), i.e., this detuning is a fraction of the mechanical frequency. In this case, we obtain some interesting results. We find that not only the integer-order (higher-order) sidebands, but also the fraction-order sidebands, and the sum and difference sidebands between the integer- and fraction-order sidebands, will appear in the output spectrum. The generated nonlinear sidebands constitute an optomechanically induced sideband comb (OMISC). The frequency range and the repetition frequency of the OMISC are proportional to the sideband cutoff-order number and the sideband interval, respectively. We show that we can extend the frequency range of the OMISC by increasing the intensity of the probe field $omega_{p}$. More importantly, we can decrease the repetition frequency, and consequently, improve the precision of the OMISC by increasing $n$ and the intensity of the probe field $omega_{f}$.
Optical interferometers with suspended mirrors are the archetype of all current audio-frequency gravitational-wave detectors. The radiation pressure interaction between the motion of the mirror and the circulating optical field in such interferometers represents a pristine form of light-matter coupling, largely due to 30 years of effort in developing high quality optical materials with low mechanical dissipation. However, in all current suspended interferometers, the radiation pressure interaction is too weak to be useful as a resource, and too strong to be neglected. Here, we demonstrate a meter-long interferometer with suspended mirrors, of effective mass $~ 125$ g, where the radiation pressure interaction is enhanced by strong optical pumping to realize a cooperativity of $50$. We probe this regime by observing optomechanically-induced transparency of a weak on-resonant probe. The low resonant frequency and high-Q of the mechanical oscillator allows us to demonstrate transparency windows barely $100$ mHz wide at room temperature. Together with a near-unity ($sim 99.9%$) out-coupling efficiency, our system saturates the theoretical delay-bandwidth product, rendering it an optical buffer capable of seconds-long storage times.
We study tunable optomechanically induced transparency by controlling the dark-mode effect induced by two mechanical modes coupled to a common cavity field. This is realized by introducing a phase-dependent phonon-exchange interaction, which is used to form a loop-coupled configuration. Combining this phase-dependent coupling with the optomechanical interactions, the dark-mode effect can be controlled by the quantum interference effect. In particular, the dark-mode effect in this two-mechanical-mode optomechanical system can lead to a double-amplified optomechanically induced transparency (OMIT) window and a higher efficiency of the second-order sideband in comparison with the standard optomechanical system. This is because the effective mechanical decay rate related to the linewidth of the OMIT window becomes a twofold increase in the weak-coupling limit. When the dark-mode effect is broken, controllable double transparency windows appear and the second-order sideband, as well as the light delay or advance, is significantly enhanced. For an N-mechanical-mode optomechanical system, we find that in the presence of the dark-mode effect, the amplification multiple of the linewidth of the OMIT window is nearly proportional to the number of mechanical modes, and that the OMIT with a single window becomes the one with N tunable windows by breaking the dark-mode effect. The study will be useful in optical information storage within a large-frequency bandwidth and multichannel optical communication based on optomechanical systems.
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