Applied Physics B最新文献

In this work we present the development and characterization of a high-gain, double-pass and four-pass femtosecond Yb: KYW amplifier pumped by two polarization-coupled tapered laser diodes emitting a total power of 9 W at 979 nm. The amplifier utilized relies on a crossed-crystals configuration, employing two 3-mm-long 10%-at. doped N_g-cut Yb: KYW crystals with orthogonal orientation of the respective N_m-axis in order to optimize pump absorption and minimize gain narrowing. The amplifier was seeded either with almost Fourier-transform limited ∼300-fs pulses from an in-house-made Yb: KYW oscillator, or with 5-ps-long, chirped pulses (∼15 nm full-width at half-maximum bandwidth around 1030 nm) from a commercial Yb-doped fiber laser. In both cases, we achieved a four-pass small-signal gain G₀ > 100 and an optical-to-optical extraction efficiency of about 30%, even at low seed average power levels. The amplifier showed excellent spatial beam quality preservation up to the full pump power (M² < 1.1) and good preservation of the pulse duration with negligible gain narrowing in case of the 300-fs bulk seeder and pulses (:le:)200 fs after compression in case of the fiber laser seeder.

The propagation of light through opaque materials, served by periodic arrays of subwavelength holes, has revolutionized imaging and sensor technology with a breakthrough of extraordinary optical transmission (EOT). The enhanced optical transmission assisted by surface plasmon resonances (SPR) has become the most ingenious phenomenon in the field of light-matter interaction. Active tuning of SPR presents a new and simple way to control spectral features of the EOT signal (without the need to change the geometrical structure of the device). This provides a new possibility to integrate an active EOT device with tunable operational frequencies on a single chip of photonic integrated circuits (PIC)- a new scalable instrument in the optoelectronic industry, and quantum technology for improving subwavelength optical imaging and biomedical sensing. In this review, we discuss the fundamentals of EOT, the role of SPR, and how the active quantum plasmonic control of the EOT device makes it a feasible on-chip electro-optic programmable element for integrated photonics.

A waveguide-based optical parametric oscillator for coherent Raman scattering applications is presented, exploiting four-wave mixing in a silicon nitride waveguide. Benefiting from its long propagation length of 20 mm in combination with a narrowband pump laser, idler pulses with an energy of up to 210 pJ and a spectral bandwidth down to 11.2 (hbox {cm}^{-1}) were obtained. By combining these narrowband idler pulses and the residual pump pulses, coherent Raman spectroscopy and microscopy were possible with a signal-to-noise ratio of up to 13.4. Thus, the presented compact and stable waveguide-based light source paves the way towards integrated lab-on-a-chip coherent Raman applications.

We have developed a highly sensitive fiber optic sensor that can measure temperature and pressure. The sensor comprises two Fabry–Perot interferometers (FPIs), FPI₁ and FPI₂, connected in parallel. FPI₁ is composed of single mode fiber (SMF)—capillary—SMF spliced together, with a ventilation hole on the capillary. FPI₂ is composed of SMF—capillary—SMF, and the capillary is filled with polyimide (PI). It is found that FPI₁ is almost insensitive to temperature, but sensitive to air pressure. FPI₂ is sensitive to temperature, but not sensitive to pressure. When the free spectra range (FSR) of FPI₁ and FPI₂ approaches twice the relationship, they are connected in parallel to form a first-order harmonic vernier effect (HVE). When the HVE sensor is used for air pressure sensing, FPI₁ is the sensing cavity and FPI₂ is the reference cavity. When the HVE sensor is used for temperature sensing, FPI₂ is the sensing cavity and FPI₁ is the reference cavity. The experimental results showed that the sensitivities of the pressure and temperature of the HVE sensor are 76.71 nm/MPa and 113.29 nm/ °C, respectively. This is currently the highest temperature sensitivity reported in literature. The accuracy of the obtained intersection point in HVE sensor is higher and than that of that of traditional Vernier effect. In addition, the FSR relationship required to form HVE is easier to achieve. By utilizing the temperature and air pressure sensitivities of FPI₁ or FPI₂, as well as that of the HVE sensor, a sensitivity measurement matrix can be formed to achieve simultaneous measurement of temperature and air pressure.

Surface nanoscale axial photonics (SNAP) microcavities exhibit a regular transmission spectrum and encompass multiple axial modes, making them highly relevant for precise and wide-range displacement sensing applications. However, conventional SNAP microcavity shapes, such as parabolic and Gaussian curves, demonstrate limitations in handling noise interference from external environments, compromising displacement sensing accuracy. In this study, we propose a robust displacement sensing approach based on the bat-shaped SNAP microcavity. This unique profile supports a uniform first-order axial field mode. By utilizing the first-order axial mode as a reference, we apply Resonance Spectra Normalization (RSN) to standardize the resonance spectrum, reducing the impact of external perturbations. Extensive simulations validate the effectiveness of this technique. When coupling parameters deviate by up to 8%, our sensing method achieves a prediction error confined within a 4 μm range, compared to 14 μm in conventional displacement sensing solutions. This advancement enhances the sensor’s immunity to environmental noise, potentially revolutionizing microcavity displacement sensing, particularly in challenging environments beyond controlled cleanrooms.

We propose and fabricate a monolithically integrated dual-mode semiconductor laser (DML) based on optical amplified feedback, where the adjustable optical self-injection feedback could induce dual-wavelength lasing, and the sub-millimeter total cavity length provides access to be microwave source. When keeping the injection current of semiconductor optical amplifier (SOA) be constant, inject different current for the segment of distributed feedback laser (DFB), we have achieved tunable microwave signal with different ranges of 10 GHz and 18 GHz respectively, which significantly simplifies the system configuration and reduces the footprint, power consumption and cost. Besides, through a special current injection scheme for the two-segment semiconductor laser, whole wavelength tuning with fixed wavelength spacing can also be realized. It provides a convenient and low-cost photonic solution for flexible and tunable microwave sources.

Refractive index (RI) is an important index to determine the composition of a substance, however, it is affected by temperature changes. Therefore, it is of great significance to design a sensor in which temperature variation will not affect the measurement of RI. In this paper, a double D-shaped photonic crystal fiber based on surface plasmon resonance (PCF-SPR) sensor is proposed to realize simultaneous and independent sensing of RI and temperature. The results show that the maximum sensitivity of the proposed sensor reaches 32,100 nm/RIU and 5.9 nm/℃ for RI and temperature, respectively. In addition, the changes of the air hole radius and the polishing depth will not cause the drift of the resonant wavelength. This advantage is conducive to fabricate a PCF-SPR sensor with high fault tolerance rate and lower production costs in practical process. The paper provides a reference for developing a high-sensitivity and multi-parameter measurement sensor used in water pollution monitoring and bio-sensing.

The present study demonstrates the suitability of the drop-casting technique for the determination of trace elements in liquids using laser induced breakdown spectroscopy (LIBS). In the present work, high-power laser shots are irradiated on the surface of a copper target to create a crater on it. Sample solutions containing trace metal elements, Na, Mg, Ca, Al, Fe and Zn are drop casted into the laser produced craters to obtain a homogeneous sample distribution. The sample is then ablated to form plasma, emissions from which are analysed to obtain a quantitative estimate of trace elements. The analytical accuracy of around 8% relative standard deviation (RSD) is achieved for the drop-casting of 3 µl of sample solution into the crater. Absolute detection limits of 0.06 mg/L for Na, 0.09 mg/L for Ca, 0.06 mg/L for Mg, 0.05 mg/L for Al, 0.23 mg/L for Fe and 0.11 mg/L for Zn are obtained. The proposed approach has been applied to estimate trace elements in liquid samples, including river water and multi-element standard solution. The present drop-casting LIBS technique has been validated using inductively coupled plasma optical emission spectroscopy (ICP-OES) technique and the results show a good resemblance.

Here, we investigate the structured superluminal and subluminal light propagation in the medium generated through a five-level atomic configuration controlled by a tiny probe and multiple of the control field. The absorption and dispersion are altered with the topological charges of control fields. The maxima and minima of absorption and corresponding normal/anomalous dispersion region are enhanced according to the (2ell) condition in the medium. The group index differs in the domain of (-15000le n_g le 17500) in the position ranges of (-1mu mle x,y le 1 mu m). The corresponding velocity of the envelope wave (v_{g}) is calculated by (c/n_g). The subluminal and superluminal maximum and minimum regions are also enhanced with the (2ell) condition in the medium. The modified work of this manuscript is useful for storage devices, imaging coding, and designing technology.

Alignment error significantly influences the fabrication quality of micro/nano structures in laser scanning heat-mode lithography systems. This paper presents an effective compensation strategy to address this issue. A laser heat-mode lithography system is established with a tightly focused objective lens and a grid scanning strategy, achieving a minimum grid size of 6 nm. The factors affecting alignment accuracy are then analyzed from the perspectives of the positioning error, galvanometer scanning distortion and coordinate system inclination. Following this, a compensation strategy is proposed, which adjusts the coordinate system of the dual-galvanometer to compensate alignment error. Experiments demonstrate the effectiveness, significantly reducing the maximum alignment error from 92.4 nm to 8.4 nm, improving alignment accuracy by approximately 91%. Furthermore, the fabrication of various structures with a minimum linewidth of 150 nm further confirms the excellent alignment performance of the system and demonstrates the advantages of laser heat-mode lithography. This work provides flexible compensation strategies for improving alignment accuracy in the dual-galvanometer laser scanning lithography system, paving the way for advancements in systems based on direct laser writing or other step-stitching lithography techniques.