Abstract We theoretically investigate the intra-band optical absorption in GaAs spherical quantum dots (QDs) confined by a screened Kratzer potential. The energy levels and wave functions are obtained analytically within the adopted approximation using the Nikiforov–Uvarov method, and the optical absorption coefficient is evaluated from Fermi’s golden rule. The results show that increasing the characteristic confinement length r 0 produces a redshift and reduces the absorption intensity. In contrast, increasing the potential depth V 0 leads to a systematic blueshift with a non-monotonic variation of the peak intensity. Increasing temperature mainly suppresses the absorption intensity through the Fermi–Dirac occupation factors, while the resonance energy remains nearly unchanged. These results demonstrate that screened Kratzer confinement provides an effective mechanism for tuning the intra-band optical response of GaAs QDs.
Abstract Under microsecond-level short-time observation, FMCW LiDAR beat-frequency estimation is limited by coarse FFT frequency spacing and sparse spectral sampling, leading to unstable peak localization and degraded ranging accuracy. To address this problem without extending the observation window, this work formulates beat-frequency extraction as a sub-bin peak localization problem. Three methods are investigated: three-point parabolic interpolation on the logarithmic magnitude spectrum (M1), weighted multi-point quadratic fitting around the spectral peak (M2), and time-domain maximum-likelihood matching (M3). Their performance is evaluated through Monte Carlo simulations and experimentally validated on a coherent FMCW LiDAR platform using a 5 m fiber-delay target. Experimental results show that, for a 1 μ s observation window, sub-bin localization significantly reduces the error fluctuation compared with direct FFT, with the standard deviation decreasing from 7.24 mm to 2.66 mm using M3. When the observation window is extended to 10 μ s, the improved spectral sampling further compresses the error distribution; M2 achieves a median ranging error of 0.99 mm, while M3 gives the lowest standard deviation of 0.97 mm. These results demonstrate that sub-bin peak localization can effectively improve ranging accuracy and stability under short-time FMCW LiDAR measurement conditions.
Abstract Laser technology has advanced various fields due to its high brightness and coherence. However, high coherence produces detrimental speckle noise and phase distortion that limit its engineering applications in full-field imaging and display. Research shows partially coherent light can suppress these issues. Among methods, the degenerate cavity laser features self-imaging structural characteristics. It enables the simultaneous excitation of numerous transverse modes within the cavity and thus directly outputs partially coherent light. As a result, it is now widely used in imaging and display applications. In this work, we established the rate equations for Q-switched operation of an Nd:YAG laser. Pulsed laser emission with a pulse width of 70 ns and a repetition rate of 500 Hz was successfully generated by integrating a potassium dihydrogen phosphate (KH2PO4, KDP) electro-optic Q-switch into a degenerate cavity capable of continuous-wave output. The output beam was measured to have approximately 200 transverse modes and a speckle contrast of 0.0707. At a pump power of 221 W, the system achieved a maximum output power of 391.6 mW, corresponding to a single pulse energy of 782 μ J. Furthermore, we performed imaging experiments using scattering media. Under the same conditions, the target image features from the Q-switched degenerate cavity laser (after transmission through 660-grit and 1500-grit ground glass diffusers) were more recognizable than those from a Gaussian beam. These results confirm that the Q-switched degenerate cavity laser maintains effective speckle noise suppression while delivering high peak-power pulsed output.
Abstract In this study, a surface plasmon resonance fiber-optic sensor is designed and demonstrated for the simultaneous detection of refractive index (RI) and temperature. A microstructured optical fiber is polished into a fan-shaped configuration with a 60° angle. Gold films are deposited on the two polished sides and the arc surface of the fiber, and a polydimethylsiloxane (PDMS) layer is further coated on the arc surface. Owing to the unique fan-shaped microstructure, the effective RI of the fiber core mode can be flexibly tuned, enabling the excitation of hybrid plasmonic modes around the polished sides and the arc surface with mutually perpendicular polarizations. The plasmonic resonance peak associated with the polished sides exhibits exclusive responsiveness to changes in the surrounding RI, achieving a sensitivity of 2403.6 nm RIU −1 . In contrast, the plasmonic mode distributed around the arc PDMS layer is solely sensitive to temperature variations, with a sensitivity of −2.8 nm °C −1 . Furthermore, an optimized fan-shaped microstructure with the PDMS layer coated on one polished side is proposed for simultaneous RI and temperature sensing, yielding enhanced sensitivities of 2800.0 nm RIU −1 and −3.0 nm °C −1 , respectively.
Abstract In this work, we propose a method to achieve dual-wavelength deep red laser based on Pr:YLF crystal. Laser with the central wavelength of 691.7 nm and 697.7 nm is simultaneously generated with an insertable cavity Lyot filter. The maximum output power is 1.001 W with the pump power of 11.88 W. The corresponding slope effciency is 11.8%. And the beam quality factor is also measured to be approximately 2.32 and 2.87 in the x and y directions, respectively. To the best of our knowledge, it is the first time we have achieved dual-wavelength laser with such a wavelength combination.
Abstract We present a scheme for precision measurement of electrical charge using tunable double optomechanically induced transparency (OMIT) with quantized squeezed fields in a hybrid Coulomb-coupled optomechanical system. We show that the double OMIT windows are linearly tuned by the charge number and robust against temperature, cavity decay and squeezed photon number. By monitoring the interval between the two transparency dips in the homodyne spectrum, high-precision charge detection can be achieved with strong noise immunity. This work provides a reliable optical method for micro-nano charge sensing and promotes the application of quantized field assisted OMIT in quantum metrology.
Abstract Laser-induced fluorescence (LIF) in the spectral range of 400–1000 nm has been investigated in rubidium vapor excited by narrowband diode laser radiation at 780 nm and 795 nm, resonant with the 5 S 1 / 2 → 5 P 1 / 2 , 3 / 2 transitions. Experiments were performed using three specially fabricated all-sapphire cells with thicknesses of L = 1 cm, 10 μ m, and 500 nm. Multiple fluorescence channels were observed, and it is shown that many LIF signals are suppressed with decreasing cell thickness due to enhanced atom–wall collisions leading to quenching of excited states. Nevertheless, for a nanocell of thickness L = 500 nm at temperatures of ∼ 300 ∘ C, blue fluorescence at 420 nm remains observable, and its intensity is compared with results available in the literature. It is further demonstrated that LIF spectroscopy enables detection and estimation of residual cesium vapor in rubidium cells via energy-transfer processes. In addition, the Rb vapor cell can operate as an efficient optical filter and frequency up-converter, converting radiation at 780 nm or 795 nm into shorter wavelengths, notably 420 nm. These results highlight the potential of broadband LIF spectroscopy in alkali vapors for applications in precision measurements, optical frequency standards, and quantum technologies.
This research demonstrates a significant performance enhancement of a passively Q-switched Nd:YAG laser via an innovative interfacial coating strategy applied to both the gain medium and the semiconductor saturable absorber mirror (SESAM). The core innovation lies in the deposition of three specific dielectric coating stacks. A critical pair of coatings on the Nd:YAG crystal facet facing the SESAM: a 1064 nm anti-reflection coating and an 808 nm high-reflection coating-effectively suppresses the parasitic etalon effect and prevents pump-induced bleaching of the SESAM in the compact laser configuration. Furthermore, the dielectric film on the SESAM itself actively tailors key saturable absorber parameters and, decisively, markedly increases its damage threshold, enabling robust high-power operation. Experimental results confirm the efficacy of this approach. The Q-switched laser operated stably within a pump power range of 1250-1550 mW, generating single-pulse energies of 0.865-1.023 & micro;J with pulse widths (full width at half-maximum) of 65-129 ns. The output power exhibited excellent linear scaling with pump power without thermal instability. This coating-based interface engineering strategy offers a novel and effective pathway for developing high-performance, compact, solid-state Q-switched lasers.
Abstract Zn:Yb:Ho:LiNbO 3 crystals with different [Li]/[Nb] ratios were prepared by Czochralski method in air. ([Li]/[Nb] = 0.946, 1.05, 1.20, 1.38.) The effect of the [Li]/[Nb] ratio on the crystal defect structure and the occupation behavior of doped ions was investigated and discussed via infrared absorption spectroscopy. The results indicate that with an increase in the [Li]/[Nb] ratio, the hydroxyl (OH − ) absorption peak in the crystal undergoes a systematic blue shift, and its absorption intensity is significantly weakened. The photodamage resistance of the crystals was investigated and analyzed by means of the light scattering exposure energy flow threshold method. The results show that the photodamage threshold of the crystals is positively correlated with the [Li]/[Nb] ratio. The upconversion luminescence properties of the crystals were tested using a fluorescence spectrometer, and the variation in the [Li]/[Nb] ratio exerted an extremely minimal effect on the luminescence peak positions. These changes are attributed to the fact that the increase in the [Li]/[Nb] ratio reduces the concentrations of intrinsic defects such as antiposition niobium ( Nb Li 4 + ) and lithium vacancies ( V Li − ), alters the occupying behavior of Zn 2+ ions, and thereby optimize the defect structure and photoelectric properties of the crystal.
Abstract We propose a polarization-maintaining (PM) photonic crystal fiber (PCF) made of Ge 23 Sb 7 S 70 chalcogenide for the mid-infrared (MIR) supercontinuum generation (SCG). This fiber features five rings of air holes arranged in a hexagonal lattice, with the air holes in the first ring shaped elliptically to induce birefringence. By tuning the structural parameters of the fiber, the proposed PM-PCF achieves an ultra-flat normal dispersion profile for x -polarization mode, spanning from −2.3 to −4.44 ps nm −1 km −1 with a small variation of 1.07 ps nm −1 km −1 over a broad wavelength range of 2.8 µ m–7.9 µ m (corresponding to a bandwidth of 5.1 µ m). In contrast, the y -polarization mode maintains a flat anomalous dispersion profile. When pumped with a 200 fs width pulse at a pump wavelength of 4.0 µ m and a peak power of 2.0 kW, the 5.0 cm long PM-PCF generates a MIR SC spanning from 1.7 µ m to 5.1 µ m (a bandwidth of 3.4 µ m) and 1.08 µ m to 8.15 µ m (a bandwidth of 7.07 µ m) for the x - and y -polarizations, respectively. Owing to its high nonlinearity and larger birefringence, the proposed PM-PCF-based SC source is a promising candidate for applications in the MIR region.
Abstract This paper demonstrates the switchable operation between dark and dark-bright-bright pulses in erbium-doped fiber laser using TaTe 2 as saturable absorber (SA). The TaTe 2 SA, fabricated via the liquid phase exfoliation method, exhibits modulation depth of 4.7%, nonsaturable loss of 45%, and saturation intensity of 2.03 MW cm −2 . By simply adjusting the pump power and polarization controller, we achieved dual-wavelength switching operation of dark/dark-bright-bright pulses at repetition frequency of 3.353 MHz, accompanied by high signal-to-noise ratio. These experimental results highlight the potential of TaTe 2 SA as promising candidates for photonics device applications.
High power, narrow linewidth, single mode distributed feedback (DFB) semiconductor lasers are essential for high-coherence photonic applications. However, the widely used symmetric quarter wavelength phase shifted DFB (QWPS-DFB) lasers suffer from pronounced longitudinal spatial hole burning (LSHB) effect, which limits the extractable output power, broadens the linewidth, and destabilizes single mode operation. Asymmetric coupling coefficient (ACC) designs have been proposed to break the longitudinal field symmetry and enhance the front facet output power. However, previous studies have explored only a limited set of device geometries and have not clarified how coupling asymmetry modulates the photon and carrier density distributions, output power, the severity of LSHB effect and the resulting spectral linewidth. Here, we develop the physics model for laterally coupled QWPS-DFB lasers incorporating an ACC grating, and combine it with a linewidth framework that relates the output power and individual linewidth contributions to the longitudinal coupling distribution and cavity length. Numerical simulations based on this model show that moderate coupling asymmetry redistributes the intracavity optical energy toward the front facet and flattens the photon and carrier density distributions. Systematic mapping of the output power, linewidth broadening associated with LSHB effect (Delta nu NN) and total linewidth as functions of the normalized coupling coefficient kappa 1L, the asymmetry ratio r kappa, and the cavity length L reveals an extended window of optimal coupling asymmetry, within which asymmetrically coupled QWPS-DFB lasers consistently achieve higher output power and a narrower total linewidth than their symmetric counterparts. For a representative design with kappa 1L = 2.1, L = 1200 & micro;m, and r kappa = 0.63, the ACC-DFB laser provides 32.49% higher output power and reduces Delta nu NN and the total linewidth by 32.25% and 26.94%, respectively, compared with the symmetric QWPS-DFB reference. These results clarify how coupling asymmetry modulates output power, linewidth and single mode stability, and offer design rules for high power, narrow linewidth lasers.
The vanadium aluminum carbide (V 2 AlC) has been examined as a saturable absorber (SA) for the Q-switching of an erbium-doped fiber laser (EDFL). Three configurations were used to test the MAX phase material (V 2 AlC) as a mesh powder SA, and thin films prepared by pulsed laser deposition (PLD) with the thicknesses of 500 nm and 1 μ m. The V 2 AlC mesh powder SA achieved a maximum repetition rate of 90.23 kHz and a minimum pulse duration of 4.95 μ s by varying the pump power from 19.36 to 172.48 mW. In contrast, PLD thin film with a thickness of 500 nm achieved the highest repetition rate of 84.17 kHz and a minimum pulse duration of 6.15 μ s when the pump power is increased from 19.36 to 129.36 mW. Similarly, PLD thin film with a thickness of 1 μ m achieved a maximum repetition rate of 117.34 kHz and a minimum pulse duration of 3.9 μ s when the pump power is increased from 19.36 to 273.24 mW. The comparison for peak power and pulse energy, mesh powder has a maximum pulse energy of 7 nJ and peak power of 0.91 mW, on the other hand, for PLD thin film having a thickness of 500 nm, the maximum pulse energy was 33 nJ and peak power of 7.3 mW. Similarly, maximum pulse energy of 41 nJ and peak power of 14.95 mW were measured for the thin film of thickness 1 μ m prepared by PLD. This is the first study that used a V 2 AlC thin film of different thicknesses grown by PLD and demonstrated the passive Q-switching, along with a detailed method for the measurement of the stability of EDFL.
In high-speed and long-haul optical fiber transmission, signal degradation arises from the accumulation and interaction of various noise sources along the propagation path. The resulting noise behavior exhibits pronounced nonlinear and coupled characteristics, which complicate its physical characterization and discrimination.In particular, the joint influence of transmission distance, amplifier noise, and signal distortion leads to complex noise evolution patterns that cannot be sufficiently characterized by a single observable indicator. In this work, we construct a quantum kernel-based learning framework for the characterization of noise states in the optical fiber communication. By using quantum feature mapping, noise-related observable quantities are embedded into a Hilbert space, where nonlinear relationships among physical indicators can be represented through a quantum-kernel-induced similarity measure.Within this framework, a classification model based on quantum support vector classification is developed. The proposed model can effectively capture the complex relationships among physical indicators and analyzing their discriminative performance with respect to noise states.The study provides effective physical insights into the application of quantum machine learning for noise structure characterization in optical fiber communication links.The integration of eye-diagram-related features, which encode signal quality, amplitude, and decision margin information, achieves superior noise characterization performance. In contrast, feature combinations involving power-domain observables provide complementary information, particularly noise power retains useful details. Moreover, the single-kernel structure demonstrates more consistent and physically meaningful representations compared to multi-kernel structures. Also, the study validate the effectiveness of the proposed framework while also identifying its current limitations.
In this paper, we investigate the dynamics of quantum resources (QRs) in a double quantum dot (DQD) system subject to thermal fluctuations. We explore the effects of temperature, Rashba spin-orbit interaction (RSOI), and other system parameters on QR in this system. We use three quantum measures in this context: linear entropy, first-order coherence, and entanglement quantified by concurrence. The results demonstrate the detrimental effects of thermal noise and that an increase in the Zeeman splitting exacerbates this degradation of QR. The findings further reveal that careful tuning of the RSOI can enhance and preserve thermal quantum correlations. Interestingly, first-order coherence persists at higher temperatures than entanglement, indicating that coherence-based tasks and protocols could be more resilient in spin-qubit arrays. Unlike entanglement and coherence, linear entropy increases with temperature and Rashba coupling, suggesting that the RSOI increases the mixedness of the thermal state in the DQD system.
A symmetry-breaking strategy for generating and controlling the chirality of Laguerre-Gaussian (LG) beams is proposed and experimentally demonstrated in an Nd:YVO4 microchip laser. By establishing an annular gain distribution, coherent superposition states of LG(0,+l) and LG(0,-l) modes were obtained for topological charges from l=1 to 22. By further introducing a controllable biaxial tilt to the microchip resonator, the rotational symmetry of the cavity was broken, enabling chirality-selected LG outputs dominated by either the positive or negative chiral component for l=1 to 4. The output was observed to evolve continuously from balanced coherent superposition states to single-chirality-dominated annular modes. For the LG(0,1) mode, the slope efficiency was 15.5% for the coherent superposition state and 14.75% for the chirality-selected state, showing that chirality selection can be achieved with only a slight reduction in conversion efficiency. This scheme enables both high-order mode extension and controllable chirality output on a single microchip-laser platform, providing an effective route toward compact structured-light sources carrying high-order orbital angular momentum.
We numerically investigate period-doubling bifurcation dynamics in a near-zero dispersion ultrafast fiber laser modeled by the generalized nonlinear Schr & ouml;dinger equation. Through cascaded period-doubling bifurcations, period-32 pulsating dissipative solitons are generated, providing a universal and reproducible route to achieve precise subharmonic entrainment. This work not only offers insights into the rich nonlinear dynamics of pulsating solitons but also highlights the potential of period-doubling bifurcation for advancing high-precision frequency comb applications.
The growing demand for portable quantum technologies in real-world applications necessitates systems capable of reliable field operation. High-precision atomic spectroscopy lies at the heart of these applications, but achieving it in compact, stable, and field deployable architectures remains a major challenge. Here, we present a compact and mobile laser spectroscopy platform based on an additively manufactured opto-mechanical housing, designed for reliable operation in both laboratory and field-deployable environments. The spectroscopic module (115 mm & times; 90 mm & times; 70 mm) integrates a diode laser system with a & micro;-metal-shielded cesium vapor cell, providing a stable atomic frequency reference within a single modular unit. Stable saturated absorption spectroscopy of the 133Cs D2 62S1/2 -> 62P3/2 transition was demonstrated over a broad operating temperature range. Laser frequency stabilization was implemented using frequency-modulation spectroscopy, enabling robust and reproducible locking under mobile conditions. At the optimal temperature of 25 degrees C, the locked laser exhibits a full-width at half-maximum frequency fluctuation of 400 +/- 4 kHz over an 80 min interval, with a minimum overlapping Allan deviation of 3.6 & times;10-11 at an averaging time of 24 s. These results establish a thermally optimized and magnetically robust platform, realizing a compact, portable plug-and-play atomic reference for deployable sensing and neutral atom-based quantum technologies
We report an all-fiber passively Q-switched erbium-doped fiber laser (EDFL) using a thulium-ytterbium co-doped fiber (Tm-Yb, TYDF) segment as a distributed fiber saturable absorber (FSA). To address practical sample-to-sample variability, we benchmark two independently fabricated TYDF samples and systematically vary the interaction length (10, 20, and 30 cm) to evaluate its impact on passive Q-switching (PQS) performance and repeatability. Absorption measurements in the 700-1600 nm range and power-dependent transmission at 1550 nm confirm saturable behavior in the erbium band and reveal clear differences in nonlinear loss between the two samples. In particular, one sample shows higher small-signal attenuation around 1550 nm (approximate to 30 dB m-1 versus approximate to 15 dB m-1) together with a stronger bleaching response. In laser operation, these differences translate into measurable changes in lasing threshold and pulse-energy extraction as the TYDF length is increased, providing practical guidelines for selecting both the TYDF sample and the interaction length to achieve stable PQS in all-fiber EDFLs. To the best of our knowledge, this is the first controlled comparison of two Tm-Yb co-doped FSA combined with a short interaction-length sweep (10-30 cm) in an all-fiber passively Q-switched EDFL.
The construction of mutually unbiased maximally entangled bases (MUMEBs) in composite dimensions is a key challenge. In this work, we addresses the problem for bipartite system Cd circle times Cd with d=2n. Utilizing exponential sums over finite Galois rings GR(4,n), we explicitly construct d2 maximally entangled bases. Crucially, we prove that a subset of d bases from this set are pairwise mutually unbiased. This finding represents a significant advancement in understanding MUMEBs for even prime power dimensions.
