We demonstrate the analog of electromagnetically induced transparency in a room temperature cavity\ud optomechanics setup formed by a thin semitransparent membrane within a Fabry-P´erot cavity. Due to destructive\ud interference, a weak probe field is completely reflected by the cavity when the pump beam is resonant with\ud the motional red sideband of the cavity. Under this condition we infer a significant slowing down of light of\ud hundreds of microseconds, which is easily tuned by shifting the membrane along the cavity axis.We also observe\ud the associated phenomenon of electromagnetically induced amplification which occurs due to constructive\ud interference when the pump is resonant with the blue sideband

A minimal observable length is a common feature of theories that aim to merge quantum physics and gravity. Quantum mechanically, this concept is associated with a nonzero minimal uncertainty in position measurements, which is encoded in deformed commutation relations. In spite of increasing theoretical interest, the subject suffers from the complete lack of dedicated experiments and bounds to the deformation parameters have just been extrapolated from indirect measurements. As recently proposed, low-energy mechanical oscillators could allow to reveal the effect of a modified commutator. Here we analyze the free evolution of high-quality factor micro- and nano-oscillators, spanning a wide range of masses around the Planck mass mP (≈22 μg). The direct check against a model of deformed dynamics substantially lowers the previous limits on the parameters quantifying the commutator deformation.

We present thick, uniform and rather flat melanin films obtained using spray deposition. The morphology of the films was investigated using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Temperature-dependent electrical resistance of melanin thin films evidenced a semiconductor-like character and a hysteretic behavior linked to an irreversible process of water molecule desorption from the melanin film. X-ray Photoelectron Spectroscopy (XPS) was carried out to analyze the role of the functional groups in the primary and secondary structure of the macromolecule, showing that the contribution of the 5,6-dihydroxyindole-2-carboxylic acid (DHICA) subunit to the molecule is about 35%. Comparison of the optical absorption of the thick (800nm) and thin (80nm) films showed a spectral change when the thickness increases. From in vacuum photoconductivity (PC) measured at controlled temperatures, we suggest that the melanin films exhibit a possible charge transport mechanism by means of delocalized pi states along the stacked planar secondary structure.

We realise a phase-sensitive closed-loop control scheme to engineer the fluctuations of the pump field which drives an optomechanical system, and show that the corresponding cooling dynamics can be significantly improved. In particular, operating in the counter-intuitive "anti-squashing" regime of positive feedback and increased field fluctuations, sideband cooling of a nanomechanical membrane within an optical cavity can be improved by 7.5 dB with respect to the case without feedback. Close to the quantum regime of reduced thermal noise, such feedback-controlled light would allow going well below the quantum backaction cooling limit.Feedback loops based on real-time continuous measurements [1] are commonly used for stabilisation purposes, and they have also been successfully applied to the stabilisation of quantum systems [2][3][4]. Typically a system is continuously monitored and the acquired signal drives the actuator which in turn drives the system to the desired target. Here we demonstrate a novel approach to closed-loop control in which the feedback acts on an additional control field which is used to drive the system of interest. In particular, the actuator acts on the control field in order to engineer its phase and amplitude fluctuations. The resulting feedback-controlled inloop field is then exploited to manipulate the system and improve its performance. In-loop optical fields have been studied for decades both theoretically [5][6][7][8] and experimentally [9, 10]. A lot of effort has been made to reduce (squash) the noise exhibited by the field fluctuations inside the loop. However, in-loop sub-shot-noise fluctuations cannot be recognised as squeezed below the vacuum noise level, for two different reasons: firstly, the free field commutation relations are no longer valid for time events separated by more than the loop delay-time, since in-loop fields are not free fields [6]; secondly, the corresponding out-of-loop fields exhibit supershot-noise fluctuations [7]. Nevertheless, useful applications of these fields have been proposed and realised, e.g. suppression of the radiation pressure noise [9], removal of classical intensity noise [10], and atomic line narrowing [8]. The common basis of these works is the negative feedback regime. Negative feedback has also been successfully employed in mechanical [11][12][13], and cavity optomechanical systems [4], where an electromagnetic field is used to probe a mechanical resonator, and in turn to control the feedback actuator, which acts directly on the mechanical oscillator. Engineered light fluctuations in the form of squeezed light have also been used in optomechanical systems to improve both the detection sensitivity [14][15][16][17] and the cooling efficiency [18][19][20]. In the present work we show that it is possible to manipulate, with a feedback system [see Figure 1 (a)], the fluctuations of the laser field that drives an optomechanical system to enhance optomechanical sideband cooling [21][22][23][24]. Our analysis demonstrates the effectiveness of t...