Applied Physics B最新文献

The present paper reports on the design, fabrication, and characterization of an 8-tube inhibited-coupling guiding hollow-core photonic crystal fiber (IC-HCPCF) capable of guiding both the beam emitted from an Yb:YAG laser at the fundamental wavelength of (lambda =1030 text{nm}) and its second harmonic at (lambda =515 text{nm}). By controlling the strut thickness of the glass capillaries to approximately (362 text{nm}), the transmission of laser radiation at both wavelengths was possible with low losses. Optimizing the outer diameter of the glass capillaries mitigates the bending-induced increase of the confinement loss at the wavelength of (515 text{nm}) without compromising the optical performance of the fiber at the wavelength of (1030 text{nm}). Experimental results confirm the near to diffraction-limited beam quality (left({M}^{2}<1.15right)) of the laser beams exiting the fiber at both operational wavelengths. Operating in the first transmission band at the wavelength of (1030 text{nm}), the calculated chromatic dispersion is (1.02 text{ps}/(text{nm}bullet text{km})), despite a diameter of the hollow core of (40 mu text{m}). At the wavelength of (515 text{nm}) this value amounts to (0.62 text{ps}/(text{nm}bullet text{km})). The measured losses are (27.5pm 0.3 text{dB}/text{km}) at the wavelength of (515text{ nm}) and (25.7pm 0.7 text{dB}/text{km}) at the wavelength of (1030text{ nm}), which is comparable to the loss of state-of-the-art IC-HCPCFs with tubular cladding structures. The measured bending-induced increase of the confinement losses confirms the potential of the proposed approach for flexible, low-loss guiding of ultrashort laser pulses at the two wavelengths using a single fiber. This gained flexibility can significantly enhance the options for wavelength selection in laser material processing applications.

In recent years, various methods for laser pulse post-compression have demonstrated their effectiveness. Nonlinear spectral broadening, achieved by coupling an ultrafast pulse into a gas-filled multi-pass cell (MPC), typically enables pulse compression factors exceeding 20, depending on the initial pulse duration. In this work, we report the direct post-compression of four Yb-based commercial laser systems to sub-20 fs durations, with energies up to 4 mJ and initial pulse durations ranging from 320 fs to 450 fs, using argon-filled MPCs. Each MPC was specifically designed to operate at a fixed optimal point for each laser, achieving the shortest possible pulse duration. Numerical simulations reproducing the experimental data highlight the critical influence of the driver pulse’s temporal profile on the shape of the broadened spectra. These simulations are compared with the experimental results, demonstrating strong agreement.

A single-resonant type-I β-Ba₂BO₄ (BBO) optical parametric oscillator (OPO) with a widely tunable output and a repetition rate of 100 Hz in the ultraviolet region has been reported. The system incorporates crystal switch technology, enabling continuous tunability in the ultraviolet spectral range from 218.7 nm to 322.5 nm, with a tuning range of 103.8 nm. The OPO component further enhances the system’s versatility, extending the tunable range from 409.9 nm to 709.0 nm, covering a continuous span of 399.1 nm. The OPO achieved a maximum conversion efficiency of 25.78% at 477.0 nm, with an average efficiency of approximately 13% across the 470–710 nm range. Additionally, the highest recorded energy output of the system at 239 nm is 205.1 µJ. Our study includes both theoretical and experimental analyses, with particular focus on the observed fluctuations in conversion efficiency throughout the experimental process.

This paper presents the design, fabrication, and implementation of a single-layer resonant-reflection grating-waveguide structure (RR-GWS) optimized for laser operation in the 2 μm wavelength region. The RR-GWS was designed to function effectively across a broad spectral region ranging from 1.9 μm to 2.1 μm. Reflectance measurements confirmed the structure’s wideband performance within this spectral region, with 99% resonant reflectivity. Incorporating the RR-GWS into a Ho: YAG thin-disk laser system, as a cavity folding mirror, it demonstrated very good power-handling capability and efficacy in wavelength and polarization selection. The 2 μm laser system achieved a linearly polarized output power of 36 W, with an optical efficiency of 34.6%. Additionally, the laser demonstrated a spectral bandwidth of < 0.5 nm full width at half maximum, i.e., 12 times narrower than that obtained with an equivalent all-mirror reference cavity.

We report on the observation of efficient light storage based on recoil-induced resonances and the associated generation of forward four-wave mixing signal. We use a strong coupling beam red-detuned from the closed transition (6S_{1/2}, F=4rightarrow 6P_{3/2}, F^{prime }=5) of cold cesium atom and a two-mode probe beam, whose frequency can be scanned around the coupling beam frequency. First, we demonstrate the coherent phase transfer from one mode component of the probe beam to the corresponding forward generated four-wave mixing beam. We then explore the coherent nature of the stored optical information to retrieve the two-mode probe energy with an efficiency 3.5 fold higher as compared with the total retrieved energy efficiency associated with the case where each mode component of the probe acts separately. Finally, we discuss a possible application of our experimental scheme and observed effects to investigate squeezing and quantum photon correlations.

We present a longitudinally diode-pumped Q-switched Nd:YAG/V:YAG microchip laser emitting at (1.44,upmu)m and the optimization of its output parameters in terms of pulse energy and peak power maximization. Optimization was achieved by modifying the size of the pumping beam with four compact focusing systems, each consisting of an aspheric collimator and one of four aspheric focusing lenses. The laser’s emission spectrum, average power, pulse duration, and spatial beam profile were measured for pumping repetition frequencies ranging from 10 to 715 Hz. Using different focusing systems, it was possible to increase the maximum pulse energy and peak power up to (91,upmu)J and 14.8 kW, respectively. Thermal effects due to pumping influenced both the laser operation and the parameters of the V:YAG saturable absorber, leading to a decrease in pulse duration from 9.6 to 4.9 ns.

The combination of the “2 + 1” phase-shifting algorithm with temporal phase unwrapping (TPU) not only facilitates the acquisition of phase information using fewer fringe patterns but also minimizes errors resulting from motion in the 3-step phase-shifting profilometry (PSP). By considering the influence of fringe frequency sequences on measurement accuracy, we derive the noise-induced wrapped phase error and its variance of the “2 + 1” phase-shifting algorithm and further analyze the phase unwrapping accuracy at each stage of the “2 + 1 + 2 + 2” algorithm. Consequently, a method for selecting the optimal fringe frequency sequence is introduced, ensuring that the phase unwrapping accuracy in both stages remains as consistent as possible, while the effectiveness of this method is experimentally validated. The experimental results demonstrate that the method for selecting the optimal fringe frequency is applicable to both hierarchical and heterodyne TPU and aligns well with theoretical analysis. Compared to two sets of non-optimal frequency sequences, the error rates of the optimal fringe frequency sequences are reduced by 33.41% and 72.53%, respectively.

In this work we present the power scaling of diode-pumped waveguide lasers fabricated in a Pr:LiLuF₄ crystal by direct femtosecond writing. We demonstrated a maximum output power of 360 mW at 604 nm, 420 mW at 721 nm, and 55 mW at 523 nm. Moreover, we demonstrated what we believe to be the first operation of a waveguide laser at 545 nm. In the end, we achieved stable lasing at 604 nm with an extraction of 96%, demonstrating the high gain achievable in waveguide devices.

A temperature-compensated magnetic field sensor based on a hollow core Bragg fiber (HCBF) Fabry-Perot interferometer (FPI) is proposed. The two ends of the HCBF are fused with optical single-mode fibers (SMF) and adhered to magnetostrictive rods. The temperature and magnetic field response can be demodulated by 2 × 2 sensitivity matrix method, achieving multiparametric demodulation of dual parameters. Experimental results indicate that the error rate of demodulated magnetic field is only 1.9%, while the error rate of demodulated temperature is only 0.8%. The ease of fabrication, high accuracy and temperature compensation suggest that the proposed fiber sensor is suitable for practical magnetic field sensing applications.

The performance of QKD systems in airborne environments is significantly hindered by optical distortions and perturbations caused by the boundary layer around high-speed aircraft. This paper proposes an optimization scheme to enhance airborne QKD system performance by analyzing the flow field around the transmitter and strategically positioning it under specific flow conditions. Using ray tracing and two distinct airborne QKD models, we evaluate system performance across various installation positions. Our results show that the largest beam deflection occurs when the transmitter is placed at the center of the wing in air-to-ground scenarios, while the QBER remains consistent across different wing positions, indicating minimal boundary layer effects on QBER. In air-to-air scenarios, optimizing the quantum source placement reduces the photon offset by 6.3 m, with QBER consistently measured at 6% ± 1% across wing positions. These findings offer critical insights for the design and deployment of QKD systems in practical airborne applications.