We study a generalized notion of two-mode squeezing for the Stokes and anti-Stokes fields in a model of a cavity Raman laser, which leads to a significant reduction in decoherence or quantum noise. The model comprises a loss-less cavity with classical pump, unsaturated medium and arbitrary homogeneous broadening and dispersion. Allowing for arbitrary linear combinations of the two modes in the definition of quadrature variables, we find that there always exists a combination of the two output modes which exhibits quadrature squeezing with noise reduction below the vacuum level. The number of noise photons for this combination mode is proportional to the square root of the number of Stokes noise photons.
The sensitivity of classical Raman spectroscopy methods, such as Coherent Anti-Stokes Raman spectroscopy (CARS) or Stimulated Raman spectroscopy (SRS), is ultimately limited by shot-noise from the stimulating fields. We present the complete theoretical analysis of a squeezing-enhanced version of Raman spectroscopy that overcomes the shot-noise limit of sensitivity with enhancement of the Raman signal and inherent background suppression, while remaining fully compatible with standard Raman spectroscopy methods. By incorporating the Raman sample between two phase-sensitive parametric amplifiers …
A completely quantum description of Raman process is used to investigate the nonclassical properties of the modes in the stimulated, spontaneous and partially spontaneous Raman process. Both coherent scattering (where all the initial modes are coherent) and chaotic scattering (where initial phonon mode is chaotic and all the other modes are coherent) are studied. Nonclassical character of Raman process is observed by means of intermodal entanglement, single mode and intermodal squeezing of vacuum fluctuations, sub-shot noise and wave variances. Joint photon-phonon number and integrated-intensi…
We fabricate a fiber coupled ultrahigh-Q resonator from a μdroplet per se; and experimentally measure stimulated Raman emission showing itself at a 160μW threshold. We observe Raman-laser lines that agree with their related calculated molecular-vibrations, as well as with a control-group experiment that uses a Raman-spectrometer. Yet, unlike spectrometers where emission is spontaneous and less directional, our droplet emitter is stimulated, single-mode-fiber coupled, resonantly enhanced with Q of 250 million, confined to a 23 um3 mode volume and has 7 orders of magnitude higher power.
Quantum Dispersive Waves and Multimode Squeezing in Pure-Kerr Parametrically Driven Cavity Solitons
Institute for Physical Science and Technology, University of Maryland（马里兰大学物理科学与技术研究所）；Department of Physics, University of Maryland（马里兰大学物理系）；Department of Mechanical Engineering, University of Maryland（马里兰大学机械工程系）；University of Maryland Baltimore County（马里兰大学巴尔的摩县分校）；National Quantum Laboratory (QLab) at Maryland（马里兰国家量子实验室）
Magnon squeezing near a quantum critical point in a cavity-magnon-qubit system
Zhejiang Key Laboratory of Micro-Nano Quantum Chips and Quantum Control, and School of Physics, Zhejiang University（浙江大学微纳量子芯片与量子控制浙江省重点实验室及物理学院）；Department of Physics, Wenzhou University（温州大学物理系）；International Quantum Academy, Shenzhen（深圳国际量子研究院）
We propose a scheme generating robust squeezed light by using double cavity optomechanical system driven by a blue detuned laser in one cavity and by a red detuned laser in the other. This double cavity system is shown to mimic effectively an interaction that is similar to the one for the downconverter, which is known to be a source of strong squeezing for the light fields. There are however distinctions as the phonons, which lead to such an interaction, can contribute to the quantum noise. We show that the squeezing of the output fields in the order of $10$dB can be achieved even at the mirro…
In this paper, we study theoretically a hybrid optomechanical system consisting of a degenerate optical parametric amplifier inside a driven optical cavity with a moving end mirror which is modeled as a stiffening Duffing-like anharmonic quantum mechanical oscillator. By providing analytical expressions for the critical values of the system parameters corresponding to the emergence of the multistability behavior in the steady-state response of the system, we show that the stiffening mechanical Duffing anharmonicity reduces the width of the multistability region while the optical parametric non…
We demonstrate efficient generation of a Raman-type optical frequency comb by employing adiabatic Raman excitation in an enhancement cavity. A broad frequency comb spanning over 130 THz is realized with an excitation power reduction exceeding three orders of magnitude compared with a single-pass configuration.
Ponderomotive squeezing of the output light of an optical cavity has been recently observed in the MHz range in two different cavity optomechanical devices. Quadrature squeezing becomes particularly useful at lower spectral frequencies, for example in gravitational wave interferometers, despite being more sensitive to excess phase and frequency noise. Here we show a phase/frequency noise cancellation mechanism due to destructive interference which can facilitate the production of ponderomotive squeezing in the kHz range and we demonstrate it experimentally in an optomechanical system formed by…
Raman spectroscopy reveals chemically specific information and provides label-free insight into the molecular world. However, the signals are intrinsically weak and call for enhancement techniques. Here, we demonstrate Purcell enhancement of Raman scattering in a tunable high-finesse microcavity, and utilize it for molecular diagnostics by combined Raman and absorption imaging. Studying individual single-wall carbon nanotubes, we identify crucial structural parameters such as nanotube radius, electronic structure and extinction cross-section. We observe a 320-times enhanced Raman scattering sp…
We analyze the effects of noise and parameter deviations in a bichromatic Raman type white light cavity, with potential applications in precision measurements such as gravitational wave detection. The results show that the dispersion variation induced by parameter deviation can be controlled within $10^{-4}$. The laser phase noise decreases the dispersion magnitude while the amplitude noise increases it. Although we can always adjust the parameters to satisfy the white light condition, both noises make the cavity transmission curve uneven.
We demonstrate cavity-enhanced Raman emission from a single atomic defect in a solid. Our platform is a single silicon-vacancy center in diamond coupled with a monolithic diamond photonic crystal cavity. The cavity enables an unprecedented frequency tuning range of the Raman emission (100 GHz) that significantly exceeds the spectral inhomogeneity of silicon-vacancy centers in diamond nanostructures. We also show that the cavity selectively suppresses the phonon-induced spontaneous emission that degrades the efficiency of Raman photon generation. Our results pave the way towards photon-mediated…
The efficiency of the frequency conversion process at the heart of Raman heterodyne spectroscopy was improved by nearly four orders of magnitude by resonant enhancement of both the pump and signal optical fields. Our results using an erbium doped Y$_2$SiO$_5$ crystal at temperatures near 4K suggest that such an approach is promising for the quantum conversion of microwave to optical photons.
Temporal cavity solitons (CS) are optical pulses that can persist in passive resonators, and they play a key role in the generation of coherent microresonator frequency combs. In resonators made of amorphous materials, such as fused silica, they can exhibit a spectral red-shift due to stimulated Raman scattering. Here we show that this Raman-induced self-frequency-shift imposes a fundamental limit on the duration and bandwidth of temporal CSs. Specifically, we theoretically predict that stimulated Raman scattering introduces a previously unidentified Hopf bifurcation that leads to destabilizat…
Quantum vacuum fluctuations fundamentally limit the precision of optical measurements, such as those in gravitational-wave detectors. Injection of conventional squeezed vacuum can be used to reduce quantum noise in the readout quadrature, but this reduction is at the cost of increasing noise in the orthogonal quadrature. For detectors near the limits imposed by quantum radiation pressure noise (QRPN), both quadratures impact the measurement, and the benefits of conventional squeezing are limited. In this paper, we demonstrate the use of a critically-coupled 16m optical cavity to diminish anti-…
We experimentally study the relaxation oscillations and amplitude stability properties of an optical laser operating deep into the bad-cavity regime using a laser-cooled $^{87}$Rb Raman laser. By combining measurements of the laser light field with nondemolition measurements of the atomic populations, we infer the response of the gain medium represented by a collective atomic Bloch vector. The results are qualitatively explained with a simple model. Measurements and theory are extended to include the effect of intermediate repumping states on the closed-loop stability of the oscillator and the…
Herein we report experimental evidence of directional SERS from molecules situated inside a single nanowire-nanoparticle junction cavity. The emission was confined to a narrow range of wavevectors perpendicular to the axis of the cavity. In addition to this, the molecules excite multiple guided modes of the nanowire which were imaged using leakage radiation Fourier microscopy. We further characterize the emission wavevectors as a function of output polarization. The excited guided modes of the wire show interesting polarization signatures. All the results were corroborated using finite element…
