Applied Physics B最新文献

For the first time, we realized 360 nm ultraviolet (UV) pulse laser by intracavity frequency doubling of a diode-pumped Q-switched Pr: YLF laser. An acousto-optic modulator was used as the active Q-switcher, and a BiB₃O₆ (BiBO) crystal served as the frequency doubler. A Q-switched laser was successfully obtained at a repetition frequency of 20 kHz, demonstrating excellent performance. Its maximum average output power reached 1.01 W, the maximum single-pulse energy was 50.5 µJ, the minimum pulse duration was merely 30 ns, and the maximum peak power was as high as 1.68 kW. When the repetition frequency was adjusted to 50 kHz, and the absorbed pump power of the 360 nm laser was 6.6 W, this laser’s maximum average output power climbed to 1.36 W, with a corresponding optical conversion efficiency of 20.6%. This novel UV laser is promising to be applied to many fields, such as environmental detection, THz wave generation, spectral analysis, microscopic imaging, and biotechnology.

Polarization detection is a crucial technology widely employed in infrared detection, image recognition, and space optical communication. Within the realm of infrared detection, it serves to enhance the detection of faint targets against complex backgrounds. Consequently, enhancing the performance of polarization devices has become one of the pivotal directions in quantum well infrared photodetectors (QWIPs) research. This paper proposes a novel circular polarization QWIPs inspired by stomatopods compound eye structure. By emulating the compound eye structure of the mantis shrimp, we integrate a top dielectric metasurface and a bottom one-dimensional metallic grating on QWIPs to achieve circular polarization detection. The dielectric metasurface, fabricated by etching heavily doped GaAs material, primarily functions as a quarter-wave plate, decomposing incident circularly polarized light into two orthogonally polarized linear components. The one-dimensional metallic grating at the bottom of device, acting as a linear polarizer, selectively excites surface plasmon polariton (SPP) modes, thereby distinguishing left-handed circularly polarized (LCP) light from right-handed circularly polarized (RCP) light. Finite-difference time-domain method was employed to calculate the total absorption spectrum of this integrated device. Under the LCP light incidence, the device exhibits a total absorption of 0.9 at the peak response wavelength of 7.8 μm, with a coupling efficiency of 3553%. Conversely, under RCP light incidence, the device demonstrates a total absorption of 0.1 at the same peak response wavelength, achieving a coupling efficiency of 95%. Furthermore, the device’s circular polarization extinction ratio reaches 37.4. This structure, achievable through quantum well focal plane array technology, represents a positive performing design for circular polarization QWIPs, contributing to enhancing target identification capabilities.

The sensitivity of coherent anti-Stokes Raman spectroscopy (CARS) is limited by the shot-noise from the probe fields used for stimulation and the non-resonant background noise. We have investigated the performance of the squeezing-enhanced version of CARS under homodyne detection and sum-intensity detection schemes, compared with the shot-noise limit (SNL) and quantum Cramér-Rao bound (QCRB). Our analysis shows homodyne detection performs better than sum-intensity and known single-intensity detection scheme results. It also provides a broader working range and shows more robustness against internal photon losses and remarkably improved performance in the gain-imbalanced configuration of SU(1,1) interferometer. As a result, we expect that our findings will be useful in quantum sensing and imaging techniques.

The thermal lens effect in a nonplanar ring oscillator laser was calculated using finite element analysis(FEA). The optical path difference (OPD) method shows that the thermal lens is significantly affected by strain and end face bulging, which is important for experimental considerations.

This paper demonstrates the characteristics of the THz parametric frequency upconversion detection based on the stimulated polariton scattering in KTiOAsO₄ (KTA) crystal pumped by a 1064 nm pulsed laser (420 ps, 1 Hz). The detectable spectral ranges can be from 3.54 to 4.03 THz, from 4.08 to 4.50 THz, from 4.71 to 5.16 THz, and from 5.87 to 6.32 THz. The minimum detectable energy is 0.24 fJ at 4.92 THz with a dynamic range of 57 dB.

A compact high-energy nanosecond (ns) slab Yb:YAG Master Oscillator Power-Amplifier (MOPA) laser system with high beam quality is proposed and demonstrated. The MOPA system consists of a Q-switched rod Yb:YAG oscillator and two cascaded large aspect ratio slab (CLARS) Yb:YAG amplifiers. The oscillator delivers a pulse energy of 2.4 mJ at a pulse repetition rate (PRR) of 100 Hz, with a pulse duration of 52 ns. The seed pulse is then amplified to 138 mJ with a gain factor of 57.5. The experimental data is in good agreement with the numerical simulation. The average beam quality factor β is 1.62. This laser system is applicable in scientific and industrial fields. The layout area of the entire system is only 900 mm × 450 mm.

We present a comparative study of continuous-wave (CW) and pulsed optical tweezers for trapping polystyrene beads with radii of 250 nm, 500 nm, and 1 μm, using five different laser power settings. In this study we also emphasize the importance of using femtosecond laser, which uses intense peak power pulses to generate larger gradient forces than a CW laser at very low and same average power. We could also achieve stable trapping of 250 nm particle at very low average powers of femtosecond laser. A Ti: Sapphire (MIRA 900 F) laser, capable of seamlessly switching between CW and pulsed modes, was used to ensure identical experimental conditions for both cases. The trap strength in each mode was determined by fitting the power spectrum to a Lorentzian curve. Our results show that pulsed tweezers are more effective for smaller particles, while for larger particles, both CW and pulsed tweezers perform similarly at lower laser powers. However, as the power increases, pulsed tweezers provide more stable trapping.

In this paper, a sensing detection method based on the fiber wedge angle microstructure for coupling excitation of microtubular cavity resonance was proposed. The theoretical model of coupling resonance between the fiber wedge end-face and microtubular cavity was established. The sensing detection mechanism of WGM resonance in the capillary microreactor was investigated. Through the simulation analysis of the factors influencing coupling efficiency and the sensing sensitivity by the capillary microcavity WGM coupling resonant structure, the structural parameters of the coupling resonant system were optimized. The experimental system was established for testing resonant excitation characteristics under different coupling structure parameters, and detecting the RI sensing of solution. The proposed capillary micro-cavity resonant detection system has good robustness, simple resonant excitation structure, and easy integration and practical application. The established theoretical model and analysis results provide new ideas for the application of optical fiber microstructure in capillary microreactor biochemical assay applications.