Journal of Russian Laser Research最新文献

We experimentally demonstrate a tunable and switchable low-threshold multi-wavelength erbiumdoped fiber pulsed laser. It is based on a composite structure of Lyot filter and nonlinear optical loop mirror. At a threshold of 30 mW, single-wavelength and dual-wavelength states can be obtained with a tuning range of 5 nm for the single wavelength and 1 nm for the dual wavelength. By adjusting the pump power and polarization controllers, the laser can achieve at most eightuple-wavelength operation. We use the nonlinear optical loop mirror as a saturable absorber to realize stable pulse output. The pulse sequences begin to appear when the pump power is 100 mW. The pulse repetition rate corresponding to the dual-wavelength is 40.52 kHz, and the pulse width is 144 ns. Due to its abundant range of wavelengths and significant pulse phenomenon, the proposed laser is widely used in fiber sensing and other fields.

Single-photon light detection and ranging (LiDAR) provides the single-photon sensitivity and picosecond time resolution, which is rapidly developing in three-dimensional (3D) imaging applications. Spatial resolution and imaging quality of LiDAR based on the single-photon avalanche-diode (SPAD) array detectors are difficult to improve, because currently available SPAD arrays still have small size array, due to the semiconductor manufacturing process limitation, and the functional circuitry around pixels reduces the fill factor. Herein, we propose a photon-efficient LiDAR method that guarantees the coupling relationship between the photosensitive area of each pixel and the corresponding beam spot illuminated on the target and uses 1/4 field of view (FoV) scanning imaging in the photosensitive area. The proposed method can effectively improve the spatial resolution of LiDAR system based on SPAD array detectors. Resolution test experiments show that the best observed (transversal) resolution is 3.1748 lp/mm at a working distance of 2.3 m, over tenfold larger than that of previous methods. Three-dimensional experiments prove that the system can achieve 3D high-resolution single-photon imaging, which is valuable in the fields of remote sensing and long-range target recognition.

In this study, we demonstrate a high-power continuous-wave (CW) Tm:YAP slab laser that is endpumped by laser diodes in a dual-end-pumped configuration. The laser delivers an output power of up to 341.6Wat 1.99 μm, corresponding to a slope efficiency of 49.4% and an optical-to-optical conversion efficiency of 41.6% with respect to the total incident pump power of 822 W. To our knowledge, this is the highest output power of a Tm:YAP laser. At an output power of 300 W, the beam quality factors M² are measured to be 260 in the x direction and 4 in the y direction, respectively. In addition, the power instability at the highest output power is measured to be 0.73% for 30 min. Also, we theoretically analyze the temperature distribution within the Tm:YAP slab crystal by the simulation software COMSOL 5.0.

We report the feasibility of a Ti₃SiC₂ MAX phase material as absorber for Q-switched pulse generation in the 1550 nm region. The proposed saturable absorber (SA) is fabricated by embedding Ti₃SiC₂ particles into polyvinyl alcohol (PVA) thin film and incorporated into Erbium-doped fiber laser (EDFL) cavity via a sandwich-structured fiber-ferrule platform. The SA thin film exhibits a linear absorption of 3.8 dB and a modulation depth of 51% in the 1550 nm region. Using the Ti₃SiC₂/PVA thin filmbased SA within an EDFL ring cavity, a self-started and stable Q-switched pulse train is achieved at a wavelength of 1561.8 nm. It exhibits a maximum pulse energy of 100.7 nJ, a maximum repetition rate of 43.5 kHz, and a minimum pulse width of 5.6 μs at a pump power of 71.5 mW. This result unveils the potential of Ti₃SiC₂ MAX phase material for use as a low-cost and practical SA for pulse generation in the 1550 nm region.

Our aim in this paper is to address the effects of plasma expansion plumes by pulsed laser irradiating the centimeter-level space debris. A dynamic model of centimeter-level space debris irradiated by pulsed laser was established based on the finite element method (FEM), and the evolutionary processes and dynamics of plasma expansion plumes were simulated by COMSOL platform. Based on the simulation and experimental results, we verily the effectiveness of the proposed model by analyzing the plasma flow fields. Further, we describe the influence of impulse coupling coefficient with different incident laser powers. The results show that optimum coupling impulse is closely related to the variation of incident laser powers, and the jet velocity of the plasma expansion plumes increases with increase in the incident laser power. On the basis of this work, we investigate in details the dynamic responses of plasma expansion plumes generated by pulsed laser irradiating the debris with different incident laser powers and laser action times. We find that the jet velocity of the plasma expansion plumes increases fast with increase in the action time and incident laser power. Owing to the influence of plasma shielding, the jet velocity of the plasma expansion plumes reach about 348 m/s, when the action time of pulsed laser and incident laser power are 40 μs and 400 kW, respectively. The results obtained provide important theoretical reference for revealing the formation mechanism of plasma expansion plumes.

In the interferometric fiber-optic gyroscope (IFOG), the stability of the light source is crucial. The fluctuations of light source power (LSP) do greatly compromise the performance of IFOG. When the driving current of the light source has fluctuations of about 0.5 to 2 mA, the bias stability of the gyroscope becomes 2 to 3 orders of magnitude worse. However, simplifying the light source is an important step in the process of miniaturizing and lowering the costs of IFOG, which compromises the stability of the light source and leads to fluctuations of the LSP. Therefore, it is important to compensate for fluctuations of the LSP. Earlier we have found that the differential signal of LSP was always crosstalked into the output signal of IFOG, under the prerequisite that the feedback phase could completely neutralize the light-intensity difference of the last period. We have given a solution to this case in our previous research work, but the prerequisite is not satisfied in many cases, and the crosstalk in the gyroscope is no longer the differential signal of LSP. In this paper, we propose a novel closed-loop control to solve this problem. The experimental results prove that this new method can effectively reduce the impact of LSP fluctuations by about 95%.

In this study, we investigate a new design of a high-sensitivity photonic-crystal pressure sensor (PCPS). The basic structure consists of a triangular array of silicon rods suspended in air. The designed sensor comprises two quasilinear waveguides that are coupled through a resonant cavity. The detection principle is based on the change in the refractive index of the Si material as a function of the pressure variation within the range of 0 to 3 GPa, resulting in a significant shift in the wavelength of the proposed sensor. The sensor offers high sensitivity of approximately 18.2 nm/ GPa, along with very fast response, high-quality factor, and ultra-compact size. The proposed design is reliable and simple to be integrated into various detection applications.

We study the time-resolved Rydberg excitation dynamics for Lithium atoms confined in a magneto-optical trap. Loss of neutral atoms due to Rydberg excitation is measured by means of analyzing the absorption of a weak probe beam. Our experiment demonstrates the existence of both density-dependent excitation blockade and excitation facilitation effects. Moreover, we measure the frequency shift of the Rydberg transition at various durations of excitation pulses. This frequency shift can be attributed to the formation of ultracold ions from the high-density ensemble of Rydberg atoms.

We propose the quaternary AlInGaN last quantum barrier (LQB) structure to improve the performance of deep-ultraviolet (DUV) laser diodes (LDs). Here, we investigate three LQB structures – Al_0.63In_0.03Ga_0.34N LQB, Al_0.65In_0.03Ga_0.32N LQ band, and Al_0.68In_0.03Ga_0.29N LQB. We find that the Al_0.68In_0.03Ga_0.29N LQB structure significantly reduces the electron leakage in the p-region, improves the carrier injection efficiency in the active region, and increases the stimulated radiation recombination rate of the DUV LDs. The simulation results indicate that the threshold current and threshold voltage decrease from 50.93 mA and 4.70 V for the Al_0.63In_0.03Ga_0.34N LQB structure to 42.47 mA and 4.63 V for the Al_0.68In_0.03Ga_0.29N LQB structure, respectively. At an injection current of 100 mA, the slope efficiency increases to 1.12 W/A. Compared with the conventional ternary AlGaN LQB structure, the quaternary AlInGaN LQB structure significantly improves the performance of the DUV LDs, which is crucial for the development of the DUV LDs.

On the “Free Space Optical” (FSO) communication link, the atmospheric scintillation phenomena play a crucial role. The severity of the scintillation can seriously impair the FSO link’s performance. In this article, we consider two wavelengths of FSO link, visible (638 nm) and infrared (980 nm), and measure their performances in a developed artificial scintillation simulation chamber, with the severity of scintillation ranged from low to high. The link performance is measured in terms of the eye pattern, optical power attenuation, signal-to-noise ratio (SNR), bit error rate (BER), etc., at the receiver side signal. As compared to the visible wavelength, 980 nm produces favorable performance in the high scintillation regime.