anti-Stokes Sidebands Research Articles

High-power Raman lasing and efficient anti-Stokes generation in mm-sized crystalline disk resonators.

We have previously experimentally observed high-power Stokes and second-order Stokes output from a mm-sized CaF2 disk using stimulated Raman scattering. A pump laser at a wavelength of 1.06 µm was coupled via a tapered fiber to the whispering gallery modes (WGM) of the disk. In this Letter, we extend this work and demonstrate the production of the first anti-Stokes sideband at power levels as high as 60 µW in near continuous-wave (CW) operation. The result is a four-component Raman comb at the output, with a wavelength range covering from 1.023 to 1.14 µm. We discuss the threshold dependence of the observed Raman lines on the crystal orientation and provide experimental validation. These advances enable the use of such mm-sized resonators as compact, efficient sources for terahertz-level frequency modulation.

Multiple lattice sites occupied AlTaO4:Cr3+ phosphor for luminescence ratiometric thermometry and NIR light source

Cr3+-doped near infrared (NIR) phosphors have promising applications in NIR light sources and optical temperature detection. The development of materials with high relative sensitivity and efficient broadband NIR luminescence is the key. In this paper, we report a new multifunctional NIR phosphor AlTaO4:Cr3+, which contains both narrow-band emission associated with 2Eg→4A2 g transition and broadband emission induced by the 4T2 g→4A2 g transition owing to Cr3+ occupies both AlO6 and TaO6 lattice sites. The R-line (2Eg→4A2 g) emission and its anti-Stokes phonon sideband emission follow the Boltzmann distribution, and the thermometer constructed accordingly reaches a maximum Sr of 1% K−1 at 110 K. Under 425 nm excitation, the broad emission band (FWHM = 200 nm) reaches maximum at 880 nm with an internal quantum efficiency of 62.8%. The NIR LEDs prepared with AlTaO4:Cr3+ confirm the application value in NIR light sources.

Comparison of Performance between Single- and Multiparameter Luminescence Thermometry Methods Based on the Mn5+ Near-Infrared Emission.

Herein, we investigate the performance of single- and multiparametric luminescence thermometry founded on the temperature-dependent spectral features of Ca6BaP4O17:Mn5+ near-infrared emission. The material was prepared by a conventional steady-state synthesis, and its photoluminescence emission was measured from 7500 to 10,000 cm-1 over the 293-373 K temperature range in 5 K increments. The spectra are composed of the emissions from 1E → 3A2 and 3T2 → 3A2 electronic transitions and Stokes and anti-Stokes vibronic sidebands at 320 cm-1 and 800 cm-1 from the maximum of 1E → 3A2 emission. Upon temperature increase, the 3T2 and Stokes bands gained in intensity while the maximum of 1E emission band is redshifted. We introduced the procedure for the linearization and feature scaling of input variables for linear multiparametric regression. Then, we experimentally determined accuracies and precisions of the luminescence thermometry based on luminescence intensity ratios between emissions from the 1E and 3T2 states, between Stokes and anti-Stokes emission sidebands, and at the 1E energy maximum. The multiparametric luminescence thermometry involving the same spectral features showed similar performance, comparable to the best single-parameter thermometry.

Polarization-selective magneto-optical modulation

We study magneto-optical coupling in a ferrimagnetic sphere resonator made of yttrium iron garnet. We find that the resonator can be operated in the telecom band as a polarization-selective optical modulator. The input state of polarization (SOP) contributing to the Stokes sideband is orthogonal to the one contributing to the anti-Stokes sideband. In the region of single sideband modulation, the SOP of both sidebands is nearly orthogonal to the SOP of the incident light. Intermodulation gain can be employed in the nonlinear regime for amplification.

Ultra-sensitive luminescence ratiometric thermometry from 2E→4A2 transitions of AlTaO4:Cr3.

In recent years, non-contact ratiometric luminescence thermometry has continued to gain popularity among researchers, owing to its compelling features, such as high accuracy, fast response, and convenience. The development of novel optical thermometry with ultrahigh relative sensitivity (Sr) and temperature resolution has become a frontier topic. In this work, we present a novel, to the best of our knowldege, luminescence intensity ratio (LIR) thermometry method that relies on AlTaO4:Cr3+ materials, based on the fact that they possess both anti-Stokes phonon sideband emission and R-line emission at the 2E→4A2 transitions and have been confirmed to follow the Boltzmann distribution. In the temperature range 40-250 K, the emission band of the anti-Stokes phonon sideband shows an upward trend, while the bands of the R-lines show the opposite downward trend. Relying on this fascinating feature, the newly proposed LIR thermometry achieves a maximum relative sensitivity of 8.45%K-1 and a temperature resolution of 0.038 K. Our work is expected to provide guiding insights for optimizing the sensitivity of Cr3+-based LIR thermometers and provide some novel entry points for designing excellent and reliable optical thermometers.

Optomechanically controllable double electromagnetically induced transparency and parametric amplification in a quantum well optomechanical system

We demonstrate the formations of optomechanically controllable double electromagnetically induced transparency (DEIT) and parametric amplification in a quantum well (QW) optomechanical system with the anti-Stokes and Stokes sideband effects. We analytically solve the Heisenberg-Langevin equations under the steady-state condition and give the expression of the susceptibility of the QW. For the optomechanical cavity driven into the anti-Stokes sideband, the coupling between the anti-Stokes sideband process and the process of the interaction between the QW and the cavity field leads to the double-dark resonances, resulting in DEIT. In the Stokes sideband case, a similar coupling can lead to the appearance of parametric amplification. These two effects are interconvertible by adjusting the relevant detuning and can be regulated by the optomechanical and QW-cavity coupling strengths. This work may be applied in the achievement of optical switches with a more obvious contrast ratio.

Multimodal deep red luminescent ratiometric thermometer of LaAlO3 doped with Mn4+

Mn 4+ ions show red to deep-red luminescence due to the 2 E→ 4 A 2 spin-forbidden transitions in several host materials. Especially, Mn 4+ -doped LaAlO 3 with perovskite structure shows the deep red luminescence with a quite long wavelength around 730 nm in the first biological window. In this study, we investigated the temperature dependence of the photoluminescence spectra of Mn 4+ -Ca 2+ co-doped LaAlO 3 (LAP: Mn 4+ -Ca 2+ ) and a possibility as a thermometer based on the energy shift of zero-phonon-line (ZPL) and the luminescence intensity ratio (LIR) of thermally coupled ZPL and anti-Stokes phonon sideband (PSB). As a result, the LAP: Mn 4+ -Ca 2+ phosphor shows the continuous energy shift of ZPL with temperature and three different temperature dependences of the LIR by selecting different two luminescence bands, which means that the LAP: Mn 4+ -Ca 2+ phosphor has four different thermometric functions in one phosphor. All the thermometers show a good relative sensitivity and wide working temperature range from 100 K to physiological temperature.

Modeling nonlinear high-pressure sensors based on degenerate four-wave mixing in photonic crystal fibers.

We propose a high-pressure sensing mechanism in solid-core silica photonic crystal fibers (PCF) that is based on the nonlinear optical process of degenerate four-wave mixing. A quite simple configuration for the pressure sensor is given and is theoretically investigated by obtaining signal gain spectra. We focus on the Stokes and anti-Stokes sidebands that are generated during propagation of the field along the PCF due to the interplay of dispersion and nonlinear optical effects. We have considered wave propagation in the normal dispersion regime with the inclusion of negative fourth-order dispersion. We have also considered a pumping field with wavelength of 1076 nm and peak power of 3000 W that propagates along a PCF with 40 cm of length. We have optimized sensitivity, varying lattice pitch and air-hole diameter, and we have obtained high sensitivities of the Stokes and anti-Stokes lines of 3.672 and -0.146nm/MPa, respectively. The proposed sensors have potential applicability in high-pressure environments.

Continuous-Wave Frequency Upconversion with a Molecular Optomechanical Nanocavity

Frequency upconversion is a cornerstone of electromagnetic signal processing, analysis and detection. It is used to transfer energy and information from one frequency domain to another where transmission, modulation or detection is technically easier or more efficient. Optomechanical transduction is emerging as a flexible approach to coherent frequency upconversion; it has been successfully demonstrated for conversion from radio- and microwaves (kHz to GHz) to optical fields. Nevertheless, optomechanical transduction of multi-THz and mid-infrared signals remains an open challenge. Here, we utilize molecular cavity optomechanics to demonstrate upconversion of sub-microwatt continuous-wave signals at $\sim$32~THz into the visible domain at ambient conditions. The device consists in a plasmonic nanocavity hosting a small number of molecules. The incoming field resonantly drives a collective molecular vibration, which imprints an optomechanical modulation on a visible pump laser and results in Stokes and anti-Stokes upconverted Raman sidebands with sub-natural linewidth, indicating a coherent process. The nanocavity offers 13 orders of magnitude enhancement of upconversion efficiency per molecule compared to free space, with a measured phonon-to-photon internal conversion efficiency larger than $10^{-4}$ per milliwatt of pump power. Our results establish a flexible paradigm for optomechanical frequency conversion using molecular oscillators coupled to plasmonic nanocavities, whose vibrational and electromagnetic properties can be tailored at will using chemical engineering and nanofabrication.

Remote magnon entanglement between two massive ferrimagnetic spheres via cavity optomagnonics

Recent studies show that hybrid quantum systems based on magnonics provide a new and promising platform for generating macroscopic quantum states involving a large number of spins. Here, we show how to entangle two magnon modes in two massive yttrium-iron-garnet (YIG) spheres using cavity optomagnonics, where magnons couple to high-quality optical whispering gallery modes supported by the YIG sphere. The spheres can be as large as 1 mm in diameter and each sphere contains more than ${10}^{18}$ spins. The proposal is based on the asymmetry of the Stokes and anti-Stokes sidebands generated by the magnon-induced Brillouin light scattering in cavity optomagnonics. This allows one to utilize the Stokes and anti-Stokes scattering process, respectively, for generating and verifying the entanglement. Our work indicates that cavity optomagnonics could be a promising system for preparing macroscopic quantum states.

Quantum Noise in Fibers with Arbitrary Nonlinear Profiles.

In this Letter we introduce a novel equation addressing the effect of quantum noise in optical fibers with arbitrary frequency-dependent nonlinear profiles. To the best of our knowledge, such an endeavor has not been undertaken before despite the growing relevance of fiber optics in the design of new quantum devices. We show that the stochastic generalized nonlinear Schrödinger equation, derived from a quantum theory of optical fibers, leads to unphysical results such as a negative photon number and the appearance of a dominant anti-Stokes sideband when applied to this kind of waveguides. Starting from a recently introduced master-equation approach to propagation in fibers, we derive a novel stochastic photon-conserving nonlinear Schrödinger equation suitable for modeling arbitrary nonlinear profiles, thus greatly enhancing the study of fiber-based quantum devices.

A Green’s function approach to the linear response of a driven dissipative optomechanical system

In this paper, we first try to shed light on the ambiguities that exist in the literature in the generalization of the standard linear response theory (LRT) which has been basically formulated for closed systems to the theory of open quantum systems in the Heisenberg picture. Then, we investigate the linear response of a driven-dissipative optomechanical system (OMS) to a weak time-dependent perturbation using the so-called generalized LRT. It is shown how the Green’s function equations of motion of a standard OMS as an open quantum system can be obtained from the quantum Langevin equations (QLEs) in the Heisenberg picture. The obtained results explain a wealth of phenomena, including the anti-resonance, normal mode splitting and the optomechanically induced transparency (OMIT). Furthermore, the reason why the Stokes or anti-Stokes sidebands are amplified or attenuated in the red or blue detuning regimes is clearly explained which is in exact coincidence, especially in the weak-coupling regime, with the Raman-scattering picture.

Molecular Platform for Frequency Upconversion at the Single-Photon Level

Direct detection of single photons at wavelengths beyond 2 microns under ambient conditions remains an outstanding technological challenge. One promising approach is frequency upconversion into the visible (VIS) or near-infrared (NIR) domain, where single photon detectors are readily available. Here, we propose a nanoscale solution based on a molecular optomechanical platform to up-convert photons from the far and mid-infrared (covering part of the THz gap) into the VIS-NIR domain. We perform a detailed analysis of its outgoing noise spectral density and conversion efficiency with a full quantum model. Our platform consists in doubly resonant nanoantennas focusing both the incoming long-wavelength radiation and the short-wavelength pump laser field into the same active region. There, infrared active vibrational modes are resonantly excited and couple through their Raman polarizability to the pump field. This optomechanical interaction is enhanced by the antenna and leads to the coherent transfer of the incoming low-frequency signal onto the anti-Stokes sideband of the pump laser. Our calculations demonstrate that our scheme is realizable with current technology and that optimized platforms can reach single photon sensitivity in a spectral region where this capability remains unavailable to date.

Watt-level mid-infrared continuous-wave Tm:YAG laser operating on the 3H4 → 3H5 transition

We report on the first continuous-wave mid-infrared Tm:Y3Al5O12 laser operating on the 3H4 → 3H5 transition. The 3.2 at.% Tm:Y3Al5O12 laser generated a maximum output power of 1.07 W at ~2.19 & 2.32 μm with a high slope efficiency of 46.3% (vs. the absorbed pump power) exceeding the Stokes limit. Depending on the output coupling and the pump power, a set of discrete laser lines in the range of 2.164–2.346 μm was observed. The spectroscopic properties of Tm:Y3Al5O12 relevant for the mid-infrared laser operation are revised. The maximum stimulated-emission cross-section for the 3H4 → 3H5 transition is 0.35 × 10−20 cm2 at 2324 nm and the emission bandwidth is ~37 nm. The overlap of the 3F4 → 3H6 and the 3H4 → 3H5 transitions is quantified revealing the formulas for Stokes and anti-Stokes phonon sidebands of emission bands. Tm:Y3Al5O12 is promising for broadly tunable (2.1–2.5 μm) and mode-locked mid-infrared oscillators.

Motional Sideband Asymmetry of a Nanoparticle Optically Levitated in Free Space.

The hallmark of quantum physics is Planck's constant h, whose finite value entails the quantization that gave the theory its name. The finite value of h gives rise to inevitable zero-point fluctuations even at vanishing temperature. The zero-point fluctuation of mechanical motion becomes smaller with growing mass of an object, making it challenging to observe at macroscopic scales. Here, we transition a dielectric particle with a diameter of 136nm from the classical realm to the regime where its zero-point motion emerges as a sizable contribution to its energy. To this end, we optically trap the particle at ambient temperature in ultrahigh vacuum and apply active feedback cooling to its center-of-mass motion. We measure an asymmetry between the Stokes and anti-Stokes sidebands of photons scattered by the levitated particle, which is a signature of the particle's quantum ground state of motion.

Emission of photon pairs by mechanical stimulation of the squeezed vacuum

To observe the dynamical Casimir effect (DCE) induced by a moving mirror is a long-standing challenge because the mirror velocity needs to approach the speed of light. Here, we present an experimentally feasible method for observing this mechanical DCE in an optomechanical system. It employs a detuned, parametric driving to squeeze a cavity mode, so that the mechanical mode, with a typical resonance frequency, can parametrically and resonantly couple to the squeezed cavity mode, thus leading to a resonantly amplified DCE in the squeezed frame. The DCE process can be interpreted as {\it mechanically-induced two-photon hyper-Raman scattering} in the laboratory frame. Specifically, {\it a photon pair} of the parametric driving absorbs a single phonon and then is scattered into an anti-Stokes sideband. We also find that the squeezing, which additionally induces and amplifies the DCE, can be extremely small. Our method requires neither an ultra-high mechanical-oscillation frequency (i.e., a mirror moving at nearly the speed of light) nor an ultrastrong single-photon optomechanical coupling and, thus, could be implemented in a wide range of physical systems.

Electromechanical Brillouin scattering in integrated optomechanical waveguides

In the well-known stimulated Brillouin scattering (SBS) process, spontaneous acoustic phonons in materials are stimulated by laser light and scatter the latter into a Stokes sideband. SBS becomes more pronounced in optical fibers and has been harnessed to amplify optical signals and even achieve lasing. Exploitation of SBS has recently surged on integrated photonics platforms as simultaneous confinement of photons and phonons in waveguides leads to drastically enhanced interaction. Instead of being optically stimulated, coherent phonons can also be electromechanically excited with very high efficiency as has been exploited in radiofrequency acoustic filters. Here, we demonstrate electromechanically excited Brillouin scattering in integrated optomechanical waveguides made of piezoelectric material aluminum nitride (AlN). Acoustic phonons of 16 GHz in frequency are excited with nanofabricated electromechanical transducers to scatter counter-propagating photons in the waveguide into a single anti-Stokes sideband. We show that phase-matching conditions of Brillouin scattering can be tuned by varying both the optical wavelength and the acoustic frequency to realize tunable single-sideband modulation. Combining Brillouin scattering photonics with nanoelectromechanical systems, our approach provides an efficient interface between microwave and optical photons that will be important for microwave photonics and potentially quantum transduction.

Luminescence behaviour of a Yb sensitized Er:YAG transparent ceramic prepared by the solid-state reaction method

Optical-grade yttrium aluminum garnet (YAG) ceramics co-doped with Yb3+ and Er3+ ions are successfully prepared via using high-temperature solid-state reaction method under vacuum condition. Cubic phase structure and full dense microstructure are determined by means of X-ray diffraction (XRD) and scanning electron microscope (SEM) methods. Both characteristics endow our ceramic with high optical transmittance of ~82% at 600 nm. Moreover, the ceramic luminescent properties are mainly discussed with Yb3+ ions serving as an efficient sensitizer for Er3+ active centers. Both zero-phonon lines (ZPLs) and sidebands of Er3+ ions in the YAG ceramics are first analyzed and the most interesting finding of this work is the anti-Stokes sidebands showing remarkably stronger emission intensity than Stokes ones. This obtained result reveals the predominance of absorbing phonon energy in vibronic luminescence process under the weak crystal field.

Superradiance and Collective Gain in the Atom-Assisted Multimode Optomechanical System

We investigate that the muti-mode optomechanical system coupled with the two-level atoms. If the driving pump field is resonance with the anti-Stokes sideband, the system is at the superradiative state. For the driving filed in the Stokes sideband, the collective gain can be observed. We study a scheme that how the atomic medium affect these superradiance and collective gain. Our results show that the presence of the atom can enhance the superradiant behavior. In the mode splitting regime, the mode splits into thirds with the presence of the atoms with the anti-Stokes sideband. In addition, we also show that the use of atoms in this system could provide us a way to switch the system form superradiative state to collective gain.

RETRACTED: Superluminal effect in a hybrid nano-electro-optomechanical system

Abstract We theoretically investigate the phenomenon of superluminosity of the transmission probe field under the effect of a strong driving field in a hybrid nano-electro-optomechnical system comprising two coupled charged mechanical end resonators connected by bias voltages. The first mechanical charged mirror is connected to the optical field, while the second charged mirror is coupled by Coulomb coupling. We find that the superluminal behavior of the transmitted probe field can be switched by adjusting the cavity field detuning and atom field detuning. The present study extends the previously developed simple optomechanical and nano-electro-optomechanical system (Ma et al., 2014)[62]. Moreover, the group delay of the pulse advancement can be controlled by adjusting the electrostatic Coulomb coupling and the power of the driving field. We explain the effect of atomic field detuning on the superluminal behavior in the regimes of anti-Stokes sidebands, i.e. Δ a = − ω 1 .