Suppression Of Spontaneous Emission Research Articles

Contrast of Ramsey-CPT Fringes in Quenching and Depolarizing Gases

Molecular nitrogen is often used as a buffer gas in cells with alkali metals due to its known ability to quench resonant fluorescence. It is widely believed that the suppression of spontaneous emission decreases the width of coherent population trapping resonance. However, our recent results have not confirmed this positive action of molecular nitrogen within the typical range of 87Rb concentrations and buffer gas pressures. On the opposite, we have observed the negative influence of quenching, the decrease in contrast of the coherent population trapping resonance in $${{\sigma }^{ + }}$$–$${{\sigma }^{ + }}$$ configuration. In this work, we further confirm these results implementing the Ramsey spectroscopy, and compare the characteristics of the central fringe in nitrogen and neon, and show that the latter provides a significantly better contrast-to-width ratio.

High-power 1018 nm Yb3+ doped fiber lasers with different YDF core and coiling diameters: theoretical and experimental study.

In this paper, the effect of the active fiber's core/cladding area ratio on the output parameters of 1018nm fiber lasers has been investigated. In this regard, we conducted a comprehensive study of two fiber lasers that utilized 25/400 and 30/250µm ytterbium-doped fibers (YDFs), both theoretically and experimentally. The optimum length of YDFs required for 40dB of amplified spontaneous emission suppression was calculated. Theoretical studies also identified the YDF breaking zone for lengths greater than the optimum. The experimental results showed that selecting the proper dimensions and coiling diameter for the active fiber significantly increased the power and efficiency of the YDF laser. We obtained an output power of 943W with a 75.5% slope efficiency for the co-pumped 30/250µm YDFL which, to the best of our knowledge, is the highest reported value for the 1018nm co-pumped fiber laser. An analysis of the experimental and theoretical results revealed that YDFs with a core/cladding area ratio greater than 1% are more suitable for realizing a high-power 1018nm fiber laser. The findings of this study are crucial for the development of high-power 1018nm fiber lasers with improved performance.

45 W single frequency Er:Yb co-doped fiber amplifier at 1530 nm

A high-power continuous-wave single-frequency 1530 nm Er:Yb co-doped fiber amplifier is demonstrated with polarization-maintaining fiber as the gain medium. To achieve the greater than 50% population inversion required for efficient 1530 nm amplification, core pumping with a 1480 nm Raman fiber laser is utilized. The advantage of the 1480 nm core-pumping over the usual 9xx nm diode cladding pumping is proved by numerical simulation. The maximum single-frequency 1530 nm laser of 45.5 W with an amplified spontaneous emission suppression ratio of 46 dB is obtained at an incident 1480 nm laser of 60.7 W, corresponding to an optical efficiency of 74%. To date, this is the highest reported single-frequency 1530 nm laser, which will be used to pump an acetylene-filled hollow-core fiber laser.

Gender differences in contralateral suppression of spontaneous otoacoustic emissions in individuals with auditory neuropathy spectrum disorders.

The current study aims to evaluate gender variations in the efferent auditory system functioning in the ANSD population and compare them to normal hearing persons using contralateral suppression of spontaneous OAE (SOAEs). For the current study, a total of 54 ears were considered prospectively. 27 ears with normal hearing (NH) sensitivity were in group I, while 27 ears with ANSD were in group II. All of the subjects had a regular audiological examination followed by synchronised SOAE recordings with and without broadband noise (in the contralateral ear) at 50dB SPL and statistical analysis was carried out. Wilcoxon signed rank test revealed a significant decrease in SOAE amplitude with contralateral noise stimulation in NH, while no such trend was observed in ANSD. However, contralateral SOAE stimulation resulted in significant high-frequency shifts for both the ANSD and NH groups in the noise condition. In the comparison of gender effects on SOAE amplitude and frequency shifts using Mann-Whitney, no significant gender differences were seen. The lack of gender differences in SOAE suppression is explained based on global standing wave theory and local oscillator theory. Contralateral effect of noise on SOAE shows frequency shifts, but not amplitude shifts both of which are not affected by gender effects.

Pauli blocking of stimulated emission in a degenerate Fermi gas

The Pauli exclusion principle in quantum mechanics has a profound influence on the structure of matter and on interactions between fermions. Almost 30 years ago it was predicted that the Pauli exclusion principle could lead to a suppression of spontaneous emission, and only recently several experiments confirmed this phenomenon. Here we report that this so-called Pauli blockade not only affects incoherent processes but also, more generally, coherently driven systems. It manifests itself as an intriguing sub-Doppler narrowing of a doubly-forbidden transition profile in an optically trapped Fermi gas of 3He. By actively pumping atoms out of the excited state, we break the coherence of the excitation and lift the narrowing effect, confirming the influence of Pauli blockade on the transition profile. This insight into the interplay between quantum statistics and coherent driving is a promising development for future applications involving fermionic systems.

Hybrid double-cladding Er/Yb co-doped fiber amplifier with Yb-ASE suppression

A single-frequency hybrid double-cladding Erbium-Ytterbium co-doped fiber amplifier (EYDFA) with Yb-band amplified spontaneous emission (Yb-ASE) suppression is demonstrated. Two segments of EYDFs, with core diameters of 6 μm and 12 μm, are fused in sequence to form a hybrid gain fiber. Theoretical analysis indicates that reducing the pump absorption in the initial part of the gain fiber is beneficial to avoid Yb-ASE boosting. A 4.79-W output laser with a linewidth of 1.67 kHz is obtained in the experiment. The Yb-ASE of the hybrid fiber amplifier is suppressed by more than 3 dB when compared to the uniform fiber amplifier with the same gain fiber length, and the slope efficiency is increased by 1.6 %. The loss characteristics of the hybrid gain fiber for backward transmitted light indicate its potential to suppress SBS effects. These results show a compact structure to suppress the Yb-ASE of the EYDF amplifier.

Long-range cooperative resonances in rare-earth ion arrays inside photonic resonators

Engineering arrays of active optical centers to control the interaction Hamiltonian between light and matter has been the subject of intense research recently. Collective interaction of atomic arrays with optical photons can give rise to directionally enhanced absorption or emission, which enables engineering of broadband and strong atom-photon interfaces. Here, we report on the observation of long-range cooperative resonances in an array of rare-earth ions controllably implanted into a solid-state lithium niobate micro-ring resonator. We show that cooperative effects can be observed in an ordered ion array extended far beyond the light’s wavelength. We observe enhanced emission from both cavity-induced Purcell enhancement and array-induced collective resonances at cryogenic temperatures. Engineering collective resonances as a paradigm for enhanced light-matter interactions can enable suppression of free-space spontaneous emission. The multi-functionality of lithium niobate hosting rare-earth ions can open possibilities of quantum photonic device engineering for scalable and multiplexed quantum networks.

3.1 kW 1050 nm narrow linewidth pumping-sharing oscillator-amplifier with an optical signal-to-noise ratio of 45.5 dB.

In this paper, the amplified spontaneous emission (ASE) suppression in a 1050 nm fiber laser with a pump-sharing oscillator-amplifier (PSOA) structure is studied theoretically and experimentally. A theoretical model of a fiber laser with a PSOA structure is established. The characteristics of the ASE for the PSOA structure and the pump-independent oscillator-amplifier (PIOA) structure are compared and analyzed. The experimental results show that the ASE can be effectively suppressed by utilizing the PSOA structure, which agree with the simulation results. A 1050 nm high-power narrow-linewidth fiber laser with PSOA structure is demonstrated, in which the gain fiber lengths of the oscillator and amplifier are 1.6 m and 9 m, respectively, to ensure the interconnection of pump power between the oscillator and amplifier. Finally, the maximum output power of 3.1 kW has been achieved, the linewidth is 0.22 nm at 3 dB, the beam quality M2 ≈ 1.33, and the optical signal-to-noise ratio (OSNR) is 45.5 dB.

Engineering of the Photon Local Density of States: Strong Inhibition of Spontaneous Emission near the Resonant and High-Refractive Index Dielectric Nano-objects.

Metallic or dielectric nano-objects change the photon local density of states of closely placed emitters, particularly when plasmon or Mie resonances are present. Depending on the shape and material of these nano-objects, they may induce either a decrease or an increase in decay rates of the excited states of the emitter. In this work, we consider the reduction of the probability of optical transitions in emitters near high-refractive index dielectric (silicon and zinc selenide) nanoparticles. We tune the spectral positions of magnetic and electric modes of nanocylinders to obtain the largest overlap of the valleys in the total decay rate spectra for differently oriented dipoles and, in this way, find the highest inhibition of about 80% for randomly oriented emitters. The spectral positions of these valleys are easy to control since the wavelengths of the modes depend on the height and diameter of nanocylinders. The inhibition value is robust to the distance between the emitter and the nanoparticle in the range of nearly 50 nm, which is crucially important for the applications, such as selective optical transition engineering and photovoltaics.

Relationship between irregularities in spontaneous otoacoustic emissions suppression and psychophysical tuning curves.

The suppression of spontaneous otoacoustic emissions (SOAEs) allows the objective evaluation of cochlear frequency selectivity by determining the suppression tuning curve (STC). Interestingly, some STCs have additional sidelobes at the high frequency flank, which are thought to result from interaction between the probe tone and the cochlear standing wave corresponding to the SOAE being suppressed. Sidelobes are often in regions of other neighboring SOAEs but can also occur in the absence of any other SOAE. The aim of this study was to compare STCs and psychoacoustic tuning curves (PTCs). Therefore, STCs and PTCs were measured in: (1) subjects in which the STC had a sidelobe, and (2) subjects without STC sidelobes. Additionally, PTCs were measured in subjects without SOAEs. Across participant groups, the quality factor Q10dB of the PTCs was similar, independently from whether SOAEs were present or absent. Thus, the presence of an SOAE does not provide enhanced frequency selectivity at the emission frequency. Moreover, both PTC and STC show irregularities, but these are not related in a straightforward way. This suggests that different mechanisms cause these irregularities.

Using high refractive index nanoparticles to inhibition of spontaneous emission

The article discusses the issues of inhibition of spontaneous emission of molecules by using silicon spherical nanoparticles and dimers made from them. It is shown that at different wavelengths of the visible spectral range, the value of the total spontaneous transitions rate in a molecule located at an optimal distance with respect to the structure with silicon nanospheres and at an optimal size of the structure can be up to 5–10 times lower than the transition rate in the case when the nanoparticles are absent.

Vacuum-field-induced THz transport gap in a carbon nanotube quantum dot

The control of light-matter interaction at the most elementary level has become an important resource for quantum technologies. Implementing such interfaces in the THz range remains an outstanding problem. Here, we couple a single electron trapped in a carbon nanotube quantum dot to a THz resonator. The resulting light-matter interaction reaches the deep strong coupling regime that induces a THz energy gap in the carbon nanotube solely by the vacuum fluctuations of the THz resonator. This is directly confirmed by transport measurements. Such a phenomenon which is the exact counterpart of inhibition of spontaneous emission in atomic physics opens the path to the readout of non-classical states of light using electrical current. This would be a particularly useful resource and perspective for THz quantum optics.

Efficient single-photon emission from a nanowire quantum dot coupled to a plasmonic nanoantenna

Integration of a single III-V quantum dot with a plasmonic nanoantenna is still underexplored as a means towards efficient single-photon sources. Here, we propose two new concepts based on a nanowire quantum dot (NWQD) emitter coupled with a plasmonic bowtie antenna and an NWQD-plasmonic metal hybrid structure. Based on finite element method modeling, we show how these devices can achieve an enhancement in single-photon emission rate and directional radiation. The plasmonic bowtie can increase the spontaneous emission of NWQD with a small diameter, overcoming their otherwise dominating intrinsic spontaneous emission suppression. Further, the NWQD-plasmonic hybrid structure can act as a single-mode waveguide. These features would facilitate nano-photonic device integration as desired for applications of bright single-photon sources, plasmonic lasers, and on-chip opto-electronic nanodevices.

Resilient Mølmer-Sørensen gate with cavity QED

We propose a simple scheme for implementing resilient two-qubit entangling gates in universal cavity QED systems. The technique employs suitably designed laser pulse with modulated amplitude and phase to decrease residual qubit-cavity entanglement that reduces the fidelity of the desired entangling operation. Numerical simulations suggest that the optimized gates are robust against errors in gate time, frequency detuning, atom-field coupling constant and pulse amplitude. Moreover, the optimized gates provide increased robustness to cavity decay as well as strong suppression of atomic spontaneous emissions. With modest experimental parameters the scheme could enable a high gate fidelity exceeding 99% in realistic scenarios.

Self-adaptive amplified spontaneous emission suppression with a photorefractive two-beam coupling filter.

Optical bandpass filters can be utilized to suppress parasitic broadband spectral power prior to laser amplification but are typically designed around specific frequencies or require manual adjustment, thus limiting their compatibility with highly tunable or integrated laser systems. In this Letter, we introduce a self-adaptive volume holographic filter using the dynamic two-beam coupling interaction in photorefractive BaTiO3, demonstrating -10dB suppression of amplified spontaneous emission noise surrounding a tunable 780 nm diode laser peak, with <2nm filter bandwidth and 50% power throughput. The spectral filtering is automatically centered on the lasing mode, with an estimated auto-tuning rate of 100 GHz/s under typical conditions. Furthermore, the filter suppression and bandwidth can be optimized via the two-beam coupling intensity ratio and angle, respectively, for versatile control over the self-adaptive filter characteristics.

Possibility for inhibited spontaneous emission in electromagnetically open parity–time-symmetric guiding structures

Remote sensing and manipulation of quantum emitters are functionalities of significant practical importance in quantum optics. Unfortunately, these abilities are considered as fundamentally challenging in systems of inhibited spontaneous emission. The reason is intimately related to the common perception that, in order to nullify the spontaneous emission decay rate, the system has to be electromagnetically closed, meaning that all loss channels should be avoided, including radiation. However, since radiation is prohibited in these systems, far-field sensing and by reciprocity, also far-field manipulation are considered impossible. Here, we suggest a possible solution to this challenge and theoretically propose an electromagnetically open system that may exhibit a complete inhibition of spontaneous emission while supporting guiding waves. This peculiar functionality is achieved through a feedback wave mechanism that is found in parity-time-symmetric structure. The analysis is based on an exact Green's function derivation as well as full wave simulations involving a realistic design for the sake of future experimental validation.

窄线宽光纤激光器在1 030 nm波段实现3 kW近衍射极限输出

In this paper, we demonstrate an all-fiber high-power Yb-doped 1 030 nm fiber laser based on master oscillator power amplifier structure. The record output power at 1 030 nm up to 3 004 W was achieved, along with a slope efficiency of 69.27%, which is the highest output power for 1030 nm near diffraction limited beam quality fiber laser. The beam quality factor is Mx2＝1.169, My2＝1.174, and full width at half maximum is 0.18 nm at maximum power level. The amplified spontaneous emission (ASE) suppression ratio reaches up to 37 dB.

Suppressing deleterious effects of spontaneous emission in creating bound states in cold atom continuum

In a previous paper [Deb and Agarwal 2014 Phys. Rev. A 90 063417], it was theoretically shown that, magneto-optical manipulation of low energy scattering resonances and atom-molecule transitions could lead to the formation of a bound state in continuum (BIC), provided there is no spontaneous emission. We find that even an exceedingly small spontaneous decay from exited molecular states can spoil the BIC. In this paper, we show how to circumvent the detrimental effect of spontaneous emission by making use of vacuum-induced coherence (VIC) which results in the cancellation or suppression of spontaneous emission. VIC occurs due to the destructive interference between two spontaneous decay pathways. An essential condition for VIC is the non-orthogonality of two transition dipole moments associated with the radiative decays form two excited states. Furthermore, the interference between two decay pathways requires that the spacing between the two decaying states must be comparable to or smaller than the square root of the product of the two spontaneous linewidths. We demonstrate that these conditions can be fulfilled by optically manipulating appropriately chosen molecular excited states, opening a promising prospect for the experimental realization of BIC of cold atoms.

Improvement of 2-μm Thulium-Doped Fiber Lasers via ASE Suppression Using All-Solid Low-Pass Photonic Bandgap Fibers

All-solid photonic bandgap fibers (PBGFs) were designed and fabricated to work as low-pass filters in 2-μm region. They were used for manipulating thulium doped fiber laser (TDFL) operating in the 2-μm region via amplified spontaneous emission suppression. A sharp lasing peak at 1915 nm was achieved using a single-stage TDFL with full width at half maximum and optical signal-to-noise ratio of 0.3 nm and 39.5 dB, respectively. This lasing is achieved using the fabricated PBGF low-pass filter with cutoff wavelength at 1945 μm and loss of more than 25 dB. In this respect, the resultant TDFL performed better than the one that did not employ the low-pass filter. In this paper, we present a few representative cases involving the all-solid PBGF. We have shown that by increasing the diameter of the fabricated PBGF from 142 to 189 μm, their cutoffs related to their bandgaps shifted from 1727 nm toward longer wavelengths, 2079 nm. As a result, lasers with different wavelengths were generated within 2-μm region.

Suppressed Spontaneous Emission for Coherent Momentum Transfer.

Strong optical forces with minimal spontaneous emission are desired for molecular deceleration and atom interferometry applications. We report experimental benchmarking of such a stimulated optical force driven by ultrafast laser pulses. We apply this technique to accelerate atoms, demonstrating up to an average of 19ℏk momentum transfers per spontaneous emission event. This represents more than an order of magnitude improvement in suppression of spontaneous emission compared to radiative scattering forces. For molecular beam slowing, this technique is capable of delivering a many-fold increase in the achievable time-averaged force to significantly reduce both the slowing distance and detrimental losses to dark vibrational states.