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- 摘要
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- 实验方案
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Fundamental Limit of the Emission Linewidths of Quantum Dots: An Ab Initio Study of CdSe Nanocrystals
摘要： The emission linewidth of a semiconducting nanocrystal (NC) significantly affects the performance in light-emitting applications but its fundamental limit is still elusive. Herein we analyze exciton-phonon coupling (EPC) from Huang-Rhys (HR) factors using ab initio calculations, and compute emission line shapes of CdSe NCs. When surface traps are absent, acoustic modes are found to dominate EPC. The computed linewidths are mainly determined by the size of NCs, being largely insensitive to the shape and crystal structure. Linewidths obtained in this work are much smaller than most measurements on the homogeneous linewidth, but they are consistent with a CdSe/CdxZn1?xSe (core/shell) NC [Park et al. Nat. Mater. 2019, 18, 249-255]. Based on this comparison, it is concluded that the large linewidths in most experiments originated from internal fields by surface (or interface) traps or quasi-type Ⅱ band alignment that amplify EPC. Thus, the present results on NCs with ideal passivation provide the fundamental minimum of homogeneous linewidths, indicating that only the CdSe/CdxZn1?xSe NC has achieved this limit through well-controlled synthesis of the shell structure. To further verify the role of internal fields, we model NCs with charged surface defects. We find that the internal field significantly increases HR factors and linewidths, in reasonable agreements with experiments on single cores. By revealing the fundamental limit of emission linewidths of quantum dots, this work will pave the way to engineering quantum dots with ultrasharp spectrum.
关键词： nanocrystals,photoluminescence,homogeneous linewidth,exciton-phonon coupling,surface traps,density functional theory,electroluminescence,quantum dots
更新于2025-09-19 17:13:59
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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Monolithic Linearly Polarized Nanosecond Fiber Laser with Record Peak Power and Near-Transform-Limited Linewidth
摘要： An all-fiberized linearly polarized nanosecond fiber laser with high peak power and near-transfrom-limited linewidth is demonstrated based on master oscillator power amplifier structure. Employing the polarization-maintaining fiber with large-mode-area Yb-doped tapered longitudinal geometry, short length and high concentration, the main amplifier possesses excellent performance for nonlinear effect suppression, including stimulated Brillouin scattering effect and self-phase modulation effect. As a result, an average output power of 8.8 W with the pulse duration of 3.8 ns is obtained at the repetition frequency of 80 kHz after the amplification, corresponding to the peak power of ~30 kW and the pulse energy of 110 uJ. The near- transform-limited linewidth is maintained, accompanying high polarization extinction ratio of more than 16 dB and near-diffraction-limited beam quality with M2 factor of 1.2. It is known to be the record output power of all-fiber linearly polarized ns fiber laser with transform-limited linewidth, to the best of our knowledge.
关键词： narrow linewidth,nanosecond fiber laser,tapered fiber,linear polarization
更新于2025-09-16 10:30:52
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[IEEE 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - Sao Paulo, Brazil (2019.10.7-2019.10.9)] 2019 SBFoton International Optics and Photonics Conference (SBFoton IOPC) - High-Performance and Small Form-Factor Tunable Lasers for High-Capacity Telecom Systems
摘要： In this work, an overview of requirements for compact optical modules and devices is presented, focusing on optical laser sources. Regarding coherent applications, the laser must have narrow linewidth, while, at the same time, be compact and present low power consumption, targeting C-form factor pluggable (CFP) modules. Latest results obtained by our group on laser development are presented, showing that the External-Cavity Laser (ECL) can fulfill the requirements for this application.
关键词： C-form factor modules,coherent optical communication,external cavity laser,micro-ITLA,narrow-linewidth laser
更新于2025-09-16 10:30:52
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Hybrid Integrated Semiconductor Lasers with Silicon Nitride Feedback Circuits
摘要： Hybrid integrated semiconductor laser sources offering extremely narrow spectral linewidth, as well as compatibility for embedding into integrated photonic circuits, are of high importance for a wide range of applications. We present an overview on our recently developed hybrid-integrated diode lasers with feedback from low-loss silicon nitride (Si3N4 in SiO2) circuits, to provide sub-100-Hz-level intrinsic linewidths, up to 120 nm spectral coverage around a 1.55 μm wavelength, and an output power above 100 mW. We show dual-wavelength operation, dual-gain operation, laser frequency comb generation, and present work towards realizing a visible-light hybrid integrated diode laser.
关键词： low-loss Si3N4 waveguides,dual-wavelength laser,laser frequency comb,InP semiconductor optical amplifier,integrated photonic circuits,semiconductor laser,hybrid integration,narrow intrinsic linewidth
更新于2025-09-16 10:30:52
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Radio-frequency analysis of self-mode-locked quantum dot laser
摘要： We numerically study and confirm experimentally a transition from unlocked multi-modal emission to self-mode-locked emission of a single-section InAs/InGaAs quantum dot laser in dependence on the laser injection current. At this transition, the radio-frequency beat note linewidth as well as the modal power fluctuations quantified by an integrated relative intensity noise of all modes are found to be significantly reduced. A linewidth reduction from several hundreds of MHz to below 1 MHz is observed, with the lowest value observed being as small as 20 kHz. Experiment and simulation results are in good qualitative and quantitative agreement.
关键词： quantum-dot laser,Self mode-locking,relative intensity noise,semiconductor laser,radio-frequency linewidth
更新于2025-09-16 10:30:52
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Tunable passively Q-switched ultranarrow linewidth erbium-doped fiber laser
摘要： A tunable passively Q-switched erbium-doped fiber laser with ultranarrow linewidth is proposed and demonstrated. With the single wall carbon nanotubes (SWCNTs) as the passive Q-switch, the ultranarrow linewidth laser operation is realized based on spectral filtering effect using an ultranarrow tunable bandpass filter (UNTBF). The Q-switched laser spectrum is tunable from 1525 to 1561 nm, covering a wavelength range of 36 nm. At 1545 nm, the highest repetition rate of ~ 38 kHz and the lowest pulse width of 1.15 μs are obtained, with the corresponding pulse energy of approximately 0.18 nJ. The linewidth measurement using self-heterodyne technique yields a linewidth value of 17.5 kHz, which may be the narrowest linewidth for a Q-switched fiber laser to the best of our knowledge.
关键词： Ultra-narrow linewidth,passively Q-switched,tunable wavelength,erbium-doped fiber laser
更新于2025-09-16 10:30:52
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Optical feedback stabilization of a self-mode-locked quantum dot laser
摘要： In this work, the impact of fine-delay tunable dual-cavity optical self-feedback (DC-OFB) on the pulse timing stability and pulse repetition rate (RR) frequency of a 1 mm long single-section self-mode-locked quantum-dot (QD) laser emitting at 1255 nm is studied experimentally and by simulation. By tuning both microscopic dual-cavity delay lengths, we find a maximum RR tuning range of 70 MHz. A two-fold periodic structure is apparent every 25 ps which corresponds to the internal round trip time of the laser. A timing jitter (TJ) reduction by a factor of 16 down to 3.5 fs is obtained. Simulation results reproduce the experimentally observed RR trends with a good qualitative and quantitative agreement.
关键词： quantum-dot laser,Self mode-locking,timing jitter,optical feedback,semiconductor laser,radio-frequency linewidth
更新于2025-09-16 10:30:52
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Passively mode-locked quantum dot laser subject to dual long cavity time-delayed optical feedback
摘要： In this contribution, we study experimentally the impact of two long external passive optical cavities on the repetition rate and timing jitter of a monolithic passively mode-locked InAs/InGaAs quantum dot laser. The dual cavity scheme allows to fully suppress feedback induced sidebands in the radio-frequency spectrum. By fine delay control of the optical self-feedback delay lengths, a repetition rate tunability of 9.4 MHz is achieved. The lowest repetition rate line width amounts to less than 50 Hz, corresponding to a timing jitter of 1.7 fs. We explain the experimentally observed timing jitter and repetition rate trends qualitatively by adapting a versatile simple time-domain model. Both experiment and simulations indicate the strongest pulse train timing jitter reduction at feedback lengths that yield the lowest repetition rate frequency deviation.
关键词： quantum-dot laser,timing jitter,Passive mode-locking,Optical feedback,semiconductor laser,radio-frequency linewidth
更新于2025-09-16 10:30:52
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Weak superradiance in arrays of plasmonic nanoantennas
摘要： A collection of N emitters can exhibit an N-fold broadening of the radiative linewidth resulting from the development of a macroscopic dipole moment. Such a broadening of the radiative linewidth has previously been observed in systems of several nanoparticles and has often been described in terms of superradiant behavior. However, the understanding of the physics behind the observed dependence of radiative linewidth on the number of irradiated nanoparticles is far from complete. In this paper, we present theoretical and experimental results that elucidate this broadening mechanism in plasmonic systems and draw a connection with the phenomenon of Dicke superradiance. We demonstrate that, in the limit where radiative broadening dominates, the extinction linewidth of a planar array of plasmonic nanoantennas scales linearly with the number of nanoantennas contained within a circle of radius equal to the resonant optical wavelength. We explain this classical phenomenon as a weak superradiance effect, which corresponds to the case in the Dicke model where only the ground state and the first collective excited state contribute to the enhanced radiation.
关键词： superradiance,radiative linewidth,Dicke model,plasmonic nanoantennas,collective behavior
更新于2025-09-16 10:30:52
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Intrinsic exciton photophysics of PbS quantum dots revealed by low-temperature single nanocrystal spectroscopy
摘要： With a tunable size-dependent photoluminescence (PL) over a wide infrared wavelength range, lead chalcogenide quantum dots (QDs) have attracted significant scientific and technological interest. Nevertheless, the investigation of intrinsic exciton photophysics at the single-QD level has remained a challenge. Herein, we present a comprehensive study of PL properties for individual core/shell PbS/CdS QDs emissive near 1.0 eV. In contrast to the sub-meV spectral linewidths observed for II/VI QDs, PbS/CdS QDs are predicted to possess broad homogeneous linewidths. Performing spectroscopy at cryogenic (4 K) temperatures, we provide direct evidence confirming theoretical predictions, showing that intrinsic linewidths for PbS/CdS QDs are in the range of 8-25 meV, with an average of 16.4 meV. In addition, low-temperature, single-QD spectroscopy reveals a broad low-energy side emission attributable to optical as well as localized acoustic phonon-assisted transitions. By tracking single QDs from 4 K to 250 K we were able to probe temperature-dependent evolutions of emission energy, linewidth and line shape. Finally, polarization-resolved PL imaging showed that PbS/CdS QDs are characterized by a 3D emission dipole, in contrast with the 2D dipole observed for CdSe QDs.
关键词： PbS/CdS,bandgap,spectral linewidth,infrared nanocrystals,polarization,single nanocrystal spectroscopy
更新于2025-09-12 10:27:22