Resonant Photon Research Articles

Quantum degeneracy and phase-space density in superradiant semiconductor heterostructures at room temperature

We investigate the fulfilment of the quantum degeneracy criterium in bulk GaAs/AlGaAs heterostructures operated under the superradiant emission generation at room temperature. The e-h density has been evaluated by analysing both spontaneous window emission from above the samples and amplified spontaneous emission radiated from their edges. The maximum experimental value of the phase-space density is 1.31 at . It is supposed that resonant photons with energies at the band gap establish coherence within the e-h ensemble and facilitate the build-up of a macroscopic wave packet from overlapped wave functions of collectively paired electrons and holes. As a result, the photon-mediated “stimulated” condensation of e-h pairs in phase space can take place at room temperature.

Electromagnetic bursts from mergers of oscillons in axion-like fields

We investigate the bursts of electromagnetic and scalar radiation resulting from the collision, and merger of oscillons made from axion-like particles using 3+1 dimensional lattice simulations of the coupled axion-gauge field system. The radiation into photons is suppressed before the merger. However, it becomes the dominant source of energy loss after the merger if a resonance condition is satisfied. Conversely, the radiation in scalar waves is dominant during initial merger phase but suppressed after the merger. The backreaction of scalar and electromagnetic radiation is included in our simulations. We evolve the system long enough to see that the resonant photon production extracts a significant fraction of the initial axion energy, and again falls out of the resonance condition. We provide a parametric understanding of the time, and energy scales involved in the process and discuss observational prospects of detecting the electromagnetic signal.

47.5 GHz Membrane-III-V-on-Si Directly Modulated Laser for Sub-pJ/bit 100-Gbps Transmission

Near-future upgrades of intra data center networks and high-performance computing systems would require optical interconnects capable of operating at beyond 100 Gbps/lane. In order for this evolution to be achieved in a sustainable way, high-speed yet energy-efficient transceivers are in need. Towards this direction we have previously demonstrated directly-modulated lasers (DMLs) capable of operating at 50 Gbps/lane with sub-pJ/bit efficiencies based on our novel membrane-III-V-on-Si technology. However, there exists an inherent tradeoff between modulation speed and power consumption due to the carrier-photon dynamics in DMLs. In this work, we alleviate this tradeoff by introducing photon–photon resonance dynamics in our energy-efficient membrane DMLs-on-Si design and demonstrate a device with a maximum 3-dB bandwidth of 47.5 GHz. This denotes a bandwidth increase of more than 2x times compared to our previous membrane DMLs-on-Si. Moreover, the DML is capable of delivering 60-GBaud PAM-4 signals under Ethernet’s KP4-FEC threshold (net data rate of 113.42 Gbps) over 2-km of standard single-mode fiber transmission. DC energy-efficiencies of 0.17 pJ/bit at 25 °C and 0.34 pJ/bit at 50 °C have been achieved for the > 100-Gbps signals. Deploying such DMLs in an integrated multichannel transceiver should ensure a smooth evolution towards Terabit-class Ethernet links and on-board optics subsystems.

Constraining early dark energy with gravitational waves before recombination

We show that the nonperturbative decay of ultralight scalars into Abelian gauge bosons, recently proposed as a possible solution to the Hubble tension, produces a stochastic background of gravitational waves which is constrained by the cosmic microwave background. We simulate the full nonlinear dynamics of resonant dark photon production and the associated gravitational-wave production, finding the signals to exceed constraints for the entire parameter space we consider. Our findings suggest that gravitational-wave production from the decay of early dark energy may provide a unique probe of these models.

Low-chirp isolator-free 65-GHz-bandwidth directly modulated lasers

Today, in the face of ever increasing communication traffic, minimizing power consumption in data communication systems has become a challenge. Direct modulation of lasers, a technique as old as lasers themselves, is known for its high energy efficiency and low cost. However, the modulation bandwidth of directly modulated lasers has fallen behind those of external modulators. In this Article, we report wide bandwidths of 65–75 GHz for three directly modulated laser design implementations, by exploiting three bandwidth enhancement effects: detuned loading, photon–photon resonance and in-cavity frequency modulation–amplitude modulation conversion. Substantial reduction of chirp (α < 1.0) as well as isolator-free operation under a reflection of up to 40% are also realized. A fast data transmission of 294.7 Gb s−1 over 15 km of a standard single-mode fibre in the O-band is demonstrated. This was achieved without an optical fibre amplifier due to a high laser output power of 13.6 dBm. Directly modulated semiconductor lasers are shown to be able to operate with bandwidths exceeding 65 GHz thanks to a cavity design that harnesses photon–photon resonances.

Direct high-resolution resonant Raman scattering measurements of dynamic nuclear spin polarization states of an InAs quantum dot

We report on the direct measurement of the electron spin splitting and the accompanying nuclear Overhauser (OH) field, and thus the underlying nuclear spin polarization (NSP) and fluctuation bandwidth, in a single InAs quantum dot under resonant excitation conditions with unprecedented spectral resolution. The electron spin splitting is measured directly via resonant spin-flip single photon Raman scattering detected by superconducting nanowires to generate excitation-emission energy maps. The observed two-dimensional maps reveal an OH field that has a non-linear dependence on excitation frequency. This study provides new insight into earlier reports of so-called avoidance and tracking, showing two distinct NSP responses directly by the addition of a emission energy axis. The data show that the polarization processes depend on which electron spin state is optically driven, with surprising differences in the polarization fluctuations for each case: in one case, a stabilized field characterized by a single-peaked distribution shifts monotonically with the laser excitation frequency resulting in a nearly constant optical interaction strength across a wide detuning range, while in the other case the previously reported avoidance behavior is actually the result of a nonlinear dependence on the laser excitation frequency near zero detuning leading to switching between two distinct mesoscopic nuclear spin states. The magnitude of the field, which is as large as 400 mT, is measured with sub-100 nuclear spin sensitivity. Stable/unstable points of the OH field distribution are observed, resulting from the non-linear feedback loop in the electron-trion-nuclear system. Nuclear spin polarization state switching occurs between fields differing by 160 mT at least as fast as 25 ms. Control experiments indicate that the strain-induced quadrupolar interaction may explain the measured OH fields.

Implications of gravitational-wave production from dark photon resonance to pulsar-timing observations and effective number of relativistic species

The coherent oscillation of axionic fields naturally drives copious production of dark photon particles in the early universe, due to resonance and tachyonic enhancement. During the process, energy is abruptly transferred from the former to the latter, sourcing gravitational wave generation. The resulting gravitational waves are eventually to be observed as stochastic background today. We report analytical results of this production and connect them to the recent pulsar-timing results by the NANOGrav collaboration. We show an available parameter space, around the mass $m_\phi \sim 10^{-13} \, {\rm eV}$ and the decay constant $f_\phi \sim 10^{16} \, {\rm GeV}$ with a dimensionless coupling of ${\cal O}(1)$, for our mechanism to account for the signal. A mechanism to avoid the axion over-dominating the universe is a necessary ingredient of this model, and we discuss a possibility to recover a symmetry and render the axion massless after the production. We also comment on potential implications of the required effective number of relativistic species to the determination of the present Hubble constant.

Exploiting Photoionization Reflectron Time-of-Flight Mass Spectrometry to Explore Molecular Mass Growth Processes to Complex Organic Molecules in Interstellar and Solar System Ice Analogs.

ConspectusThis Account presents recent advances in our understanding on the formation pathways of complex organic molecules (COMs) within interstellar analog ices on ice-coated interstellar nanoparticles upon interaction with ionizing radiation exploiting reflectron time-of-flight mass spectrometry (ReTOF-MS) coupled with tunable vacuum ultraviolet (VUV) single photon ionization (PI) and resonance enhanced multiphoton ionization (REMPI) of the subliming molecules during the temperature-programmed desorption (TPD) phase. Laboratory simulation experiments provided compelling evidence that key classes of complex organics (aromatic hydrocarbons, alcohols, ethers, aldehydes, enols, ketones, and carboxylic acids) can be synthesized upon exposure of astrophysically relevant model ices to ionizing radiation within and throughout the ices at temperatures as low as 5 K.Molecular mass growth processes can be initiated by suprathermal or electronically excited reactants along with barrierless radical-radical recombination if both radicals hold a proper recombination geometry. Methyl (CH3), amino (NH2), hydroxyl (OH), ethyl (C2H5), vinyl (C2H3), ethynyl (C2H), formyl (HCO), hydroxycarbonyl (HOCO), hydroxymethyl (CH2OH), methoxy (CH3O), and acetyl (CH3CO) represent readily available reactants for radical-radical recombination within the ices. Reactive singlet species were found to insert without barrier into carbon-hydrogen and carbon-carbon single bonds (carbene) leading to an extension of the carbon chain and may add to carbon-carbon double bonds (carbene, atomic oxygen) forming cyclic reaction products. These galactic cosmic ray-triggered nonequilibrium pathways overcome previous obstacles of hypothesized thermal grain-surface processes and operate throughout the ice at 5 K. Our investigations discriminate between multiple structural isomers such as alcohols/ethers, aldehydes/enols, and cyclic/acyclic carbonyls. These data provide quantitative, isomer selective input parameters for a cosmic ray-dictated formation of complex organics in interstellar ices and are fully able to replicate the astronomical observations of complex organics over typical lifetimes of molecular clouds of a few 106 to 107 years. Overall, PI-ReTOF-MS revealed that the processing of astrophysically relevant ices can lead to multifaceted mixtures of organics reaching molecular weights of up to 200 amu. Further advances in laboratory techniques beyond the FTIR-QMS limit are clearly desired not only to confidently assign detection in laboratory ice analog experiments of increasingly more complex molecules of interest but also from the viewpoint of future astronomical searches in the age of the Atacama Large Millimeter/submillimeter Array (ALMA).

Whispering-gallery mode resonance-assisted plasmonic sensing and switching in subwavelength nanostructures

Whispering-gallery modes (WGMs), confining the resonant photons in nanoscale volumes, have been known to exhibit high-quality factor and sensitivity for electromagnetic waves in the field of nanophotonics. Here, we numerically demonstrate that a metasurface, which consists of periodic arrays with concentrically hybrid rectangular-slot (RS) and circular-ring-aperture (CRA) unit cells, supports polarization-dependent plasmonic sensing and switching in the visible and near-infrared regions. In particular, it is shown that the magnetic plasmon-induced transparency (PIT) effect arises from the coupling between a wideband WGM resonance and a narrowband magnetic dipole resonance mode in the hybrid metasurface. It is of great interest to find that the resonance mode broadening and mode shift sensing can be realized by varying the polarization angle of incident light and the length of the RS structure, respectively. Moreover, a novel and easy-fabricated plasmonic switching can be implemented in the visible and near-infrared regions. By changing the inner radius of the CRA structure, we reveal that the operating wavelength of the plasmonic switching can be extended to the telecom O- or E-band with an optimal ON/OFF ratio being 18.35 dB. Our results provide a path toward designing compact and tunable PIT device and could expand the application range of subwavelength nanostructures to the realm of optical communications and information process.

Effect of a strongly magnetized plasma on the resonant photon scattering process

In this paper, the photons absorption rate in a relatively strong magnetic field in the Compton process taking into account the resonance on the virtual electron are calculated. A comparative analysis of the obtained result with the nonresonant case was carried out.

Directly modulated membrane lasers with 108 GHz bandwidth on a high-thermal-conductivity silicon carbide substrate

Increasing the modulation speed of semiconductor lasers has attracted much attention from the viewpoint of both physics and the applications of lasers. Here we propose a membrane distributed reflector laser on a low-refractive-index and high-thermal-conductivity silicon carbide substrate that overcomes the modulation bandwidth limit. The laser features a high modulation efficiency because of its large optical confinement in the active region and small differential gain reduction at a high injection current density. We achieve a 42 GHz relaxation oscillation frequency by using a laser with a 50-μm-long active region. The cavity, designed to have a short photon lifetime, suppresses the damping effect while keeping the threshold carrier density low, resulting in a 60 GHz intrinsic 3 dB bandwidth (f3dB). By employing the photon–photon resonance at 95 GHz due to optical feedback from an integrated output waveguide, we achieve an f3dB of 108 GHz and demonstrate 256 Gbit s−1 four-level pulse-amplitude modulations with a 475 fJ bit−1 energy cost of the direct-current electrical input. Directly modulated membrane distributed reflector lasers are fabricated on a silicon carbide platform. The 3 dB bandwidth, four-level pulse-amplitude modulation speed and operating energy for transmitting one bit are 108 GHz, 256 Gbit s−1 and 475 fJ, respectively.

Near-field resonant photon sorting applied: dual-band metasurface quantum well infrared photodetectors for gas sensing

Abstract Two photodetectors for measuring transmission and two bulky, separated narrowband filters for picking a target gas absorption line and a non-absorbing reference from broadband emission are typically required for dual-band non-dispersive infrared (NDIR) gas sensing. Metal-dielectric-metal (MDM) metasurface plasmon cavities, precisely controllable narrowband absorbers, suggest a next-generation, nanophotonic approach. Here, we demonstrate a dual-band MDM cavity detector that consolidates the function of two detectors and two filters into a single device by employing resonant photon sorting-a function unique to metasurfaces. Two MDM cavities sandwiching a quantum well infrared photodetector (QWIP) with distinct resonance wavelengths are alternately arranged in a subwavelength period. The large absorption cross section of the cavities ensures ~95% efficient lateral sorting of photons by wavelength into the corresponding detector within a near-field region. The flow of incident photons is thus converted into two independent photocurrents for dual-band detection. Our dual-band photodetectors show competitive external quantum efficiencies up to 38% (responsivity 2.1 A/W, peak wavelength 6.9 5m) at 78 K. By tailoring one resonance to an absorption peak of NO2 (6.25 5m) and the other to a non-absorbing reference wavelength (7.15 5m), NDIR NO2 gas sensing with 10 ppm accuracy and 1 ms response times is demonstrated. Through experiment and numerical simulation, we confirm near-perfect absorption at the resonant cavity and suppressed absorption at its non-resonant counterpart, characteristic of resonant photon sorting. Dual-band sensing across the mid-infrared should be possible by tailoring the cavities and quantum well to desired wavelengths.

Transfer mechanisms in semiconductor hybrids with colloidal core/shell quantum dots on ZnSe substrates

Hybrid systems consisting of colloidal CdS/ZnS core/shell quantum dots on ZnSe semiconductor substrates have been studied by continuous-wave and nanosecond time-resolved photoluminescence. On the basis of kinetic calculations, we studied the interplay between the possible transfer processes in these hybrids. The considered transfer mechanisms were resonance energy transfer, photon reabsorption, electron and hole tunneling. Depending on the size of the CdS cores the dominating transfer mechanism is changing. Carrier tunneling was found only for quantum dots in direct contact to the substrate. For large quantum dots a hole tunneling was found, whereas in case of small dots the fast electron tunneling is decisive. Eventually, we were able to determine the conduction band offset between CdS and ZnSe to 0.56 eV at 10 K.

Modeling of generating ultra-high frequency oscillations in VCSEL integrated with cascaded transverse coupled cavities

We report on the design and modeling of vertical-cavity surface-emitting laser (VCSEL) integrated in the lateral direction with a cascade of multiple passive cavities. The scheme is proposed to increase the bandwidth of the VCSEL in the mm-waveband to generate ultra-high-frequency oscillations with low-frequency chirp. The model treats the transverse feedback induced by the cascaded transverse coupled cavities (TTCs) as time delay of the transverse slow light due to round trips in these cavities. The simulation is based on numerical integration of the modified time-delay rate equations of the intensity and phase of the electric field. The simulation results are used to optimize the TCCs parameters, including the coupling ratio and TCC length, for generating ultra-high-frequency signals with high intensity, low chirping and low distortion. The obtained results show that the proposed structure could achieve 300% enhancement of the modulation bandwidth of the C-VCSEL due to either extended carrier-photon resonance (CPR) frequencies of photon–photon resonance (PPR). Signals with frequencies as high as (40–49 GHz) with second-harmonic distortion lower than − 30 dB are presented.

How to suppress exponential growth—on the parametric resonance of photons in an axion background

Axion-photon interactions can lead to an enhancement of the electromagnetic field by parametric resonance in the presence of a cold axion background, for modes with a frequency close to half the axion mass. In this paper, we study the role of the axion momentum dispersion as well as the effects of a background gravitational potential, which can detune the resonance due to gravitational redshift. We show, by analytical as well as numerical calculations, that the resonance leads to an exponential growth of the photon field only if (a) the axion momentum spread is smaller than the inverse resonance length, and (b) the gravitational detuning distance is longer than the resonance length. For realistic parameter values, both effects strongly suppress the resonance and prevent the exponential growth of the photon field. In particular, the redshift due to the gravitational potential of our galaxy prevents the resonance from developing for photons in the observable frequency range, even assuming that all the dark matter consists of a perfectly cold axion condensate. For axion clumps with masses below ∼ 10−13 M⊙, the momentum spread condition is more restrictive, whereas, for more massive clumps, the redshift condition dominates.

Vortex electron generated by microwave photon with orbital angular momentum in a magnetic field

With semi-quantum theory, we quantitatively deduce microwave photons radiated from the moving electrons in a magnetic field, as well as the interaction of transmitted microwave photons with the vortex electrons in the magnetic field. It shows that the Orbital Angular Momentum (OAM) transition between microwave photons and vortex electrons in the magnetic field occurs when the relativistic effect is considered. This work indicates an effective way to transfer OAM between microwave photons and vortex electrons theoretically. By the OAM microwave photon resonance absorption, different vortex electrons with radial and magnetic quantum numbers can be generated. Furthermore, vortex electrons can be detected to analyze the OAM carried by microwave photons.

Enhancement of rotational vacuum friction by surface photon tunneling

AbstractWhen a neutral sphere is rotating near a surface in vacuum, it will experience a frictional torque due to quantum and thermal electromagnetic fluctuations. Such vacuum friction has attracted many interests but has been too weak to be observed. Here we investigate the vacuum frictional torque on a barium strontium titanate (BST) nanosphere near a BST surface. BST is a perovskite ferroelectric ceramic that can have large dielectric responses at GHz frequencies. At resonant rotating frequencies, the mechanical energy of motion can be converted to electromagnetic energy through resonant photon tunneling, leading to a large enhancement of the vacuum friction. The calculated vacuum frictional torques at resonances at sub-GHz and GHz frequencies are several orders larger than the minimum torque measured by an optically levitated nanorotor recently, and are thus promising to be observed experimentally. Moreover, we calculate the vacuum friction on a rotating sphere near a layered surface for the first time. By optimizing the thickness of the thin-film coating, the frictional torque can be further enhanced by several times.

Modulation induced splitting of the magnetic resonance

The splitting of magnetic resonance induced by a frequency modulated linearly polarized light field is presented for Hanle experimental configuration. The experiment is carried out with thermal Rubidium atoms in an anti-relaxation coated glass cell. The observed splitting corresponds to steady-state behaviour of the system over an integrated time scale that is longer than the modulation frequency. The splitting is only observed for dark resonances, with left and right circularly polarized light simultaneously coupled to the atomic system. The split components are separated by half of the modulation frequency with the central component lying at zero-magnetic field. The absence of odd split components at single photon resonance is consistent with the theoretical calculation. The different components of the split profile have distinct response to the direction of the transverse magnetic field. The response is captured by the theoretical calculation and the underlying physical mechanism is discussed. These studies will be useful in metrology and advancement of vector atomic magnetometer.

Control of the half-cycle harmonic emission process for generating the intense and ultrashort single attosecond pulses (SAPs)

Abstract In this paper, the half-cycle harmonic generation process has been controlled by using the asymmetric inhomogeneous chirped pulse combined with the ultraviolet (UV) pulse. It is found that by properly optimizing the chirps and chirp delays of the fundamental two-color pulse, the optimal negative and positive half-cycle laser profiles for the harmonic cutoff extension can be obtained. Further, with the introduction of the negative and positive inhomogeneous effect, respectively, the harmonic cutoff from the negative and positive half-cycle laser profiles can be further improved. Next, with the assistance of the UV pulse, the harmonic intensity can be enhanced due to the UV resonance ionization. Moreover, the single and double UV photon resonance ionizations are much better for generating the higher harmonic intensity. As a result, the stronger and broader harmonic plateaus with the larger harmonic cutoff can be obtained, which can support the generation of the high-intensity ultrashort attosecond pulses with the pulse durations of sub-45 as.

XeUS: A second-generation automated open-source batch-mode clinical-scale hyperpolarizer

We present a second-generation open-source automated batch-mode 129Xe hyperpolarizer (XeUS GEN-2), designed for clinical-scale hyperpolarized (HP) 129Xe production via spin-exchange optical pumping (SEOP) in the regimes of high Xe density (0.66–2.5 atm partial pressure) and resonant photon flux (~170 W, Δλ = 0.154 nm FWHM), without the need for cryo-collection typically employed by continuous-flow hyperpolarizers. An Arduino micro-controller was used for hyperpolarizer operation. Processing open-source software was employed to program a custom graphical user interface (GUI), capable of remote automation. The Arduino Integrated Development Environment (IDE) was used to design a variety of customized automation sequences such as temperature ramping, NMR signal acquisition, and SEOP cell refilling for increased reliability. A polycarbonate 3D-printed oven equipped with a thermo-electric cooler/heater provides thermal stability for SEOP for both binary (Xe/N2) and ternary (4He-containing) SEOP cell gas mixtures. Quantitative studies of the 129Xe hyperpolarization process demonstrate that near-unity polarization can be achieved in a 0.5 L SEOP cell. For example, %PXe of 93.2 ± 2.9% is achieved at 0.66 atm Xe pressure with polarization build-up rate constant γSEOP = 0.040 ± 0.005 min−1, giving a max dose equivalent ≈ 0.11 L/h 100% hyperpolarized, 100% enriched 129Xe; %PXe of 72.6 ± 1.4% is achieved at 1.75 atm Xe pressure with γSEOP of 0.041 ± 0.001 min−1, yielding a corresponding max dose equivalent of 0.27 L/h. Quality assurance studies on this device have demonstrated the potential to refill SEOP cells hundreds of times without significant losses in performance, with average %PXe = 71.7%, (standard deviation σP = 1.52%) and mean polarization lifetime T1 = 90.5 min, (standard deviation σT = 10.3 min) over the first ~200 gas mixture refills, with sufficient performance maintained across a further ~700 refills. These findings highlight numerous technological developments and have significant translational relevance for efficient production of gaseous HP 129Xe contrast agents for use in clinical imaging and bio-sensing techniques.