Narrow Results

Due to their excellent noise performance and technical maturity, ultra-stable continuous-wave neodymium-doped yttrium aluminum garnet lasers are one of the major light sources in a series of precision measurements such as ground and space-based gravitational wave detection, inter-satellite laser ranging and coherent optical communication. As the first step of developing an ultra-stable spaceborne laser, we carried out the design, development and environmental test of an all-solid-state Nd:YAG NPRO spaceborne laser. The laser deliveries 11.48 mW of optical power at 1064.405 nm, exhibits intensity and frequency noises less than 1 × 10${}^{-2}$/$\surd$Hz and 1 MHz/$\surd$Hz (Fourier frequencies $>$ 10 mHz), respectively, passed environmental tests and has been onboard the first satellite of the Taiji program for one year. The work laid a solid foundation for realizing ultra-stable lasers for the Taiji program as well as being used in many space applications.

Phase synchronization and entrainment of a linear array of loss modulated Nd:YAG lasers are experimentally investigated. The temporally shifting nature of phase synchronization with increasing modulation depth is studied. Chaotic intensity dynamics changes dramatically with increasing modulation, and exhibit entrainment to the modulation signal. Frequency filtered phase variables, defined from the laser intensity time series, uncover phenomena of phase synchronization and competition for phase synchronization that are otherwise hidden.

The investigation deals with the turning of Alumina (Al₂${\text{O}}_3)$ ceramic using various parameters of the input process. The experimental design has been used based on Taguchi technology to perform the experimentation. Pulse frequency, average laser power, work piece rotational speed and feed rate are the process inputs considered during investigation. The Signal-to-Noise ratio values are used for measuring various outputs. The best amount of spot overlap has been reached with various combined parameter settings. In addition, a better width of the rotational scan has been attained by varying axial feed rate as well as the rotational speed of the work piece. Micro-turned deviation (depth) and machined surface finish at different input parametric combinations were considered as output reactions for machining. During the laser turning operation, analyses learned the effect of overlaps on the various inputs considered for output measurements such as micro-degree deviation and surface roughness. The investigation reveals that the surface finish decreases with an increase in overlap in the circumferential direction and rotation of the work sample. The maximum surface finish is 0.507$\mu$m achieved at a frequency of 5000Hz, 300rpm work piece cutting speed, 8.5W power and 0.4mm/s feed.

Laser ablation of sintered SiO₂:TiO₂ targets using Nd:YAG lasers at fundamental (1064nm) harmonic generation in the air has been studied using optical emission spectroscopy. Exploring the spatial fluctuations in electron temperature ($T_e$) and electron density ($n_e$), there is a discussion of how laser energy affects electron temperature ($T_e$) and electron density ($n_e$). Laser energy has also been shown to affect the intensity and velocity of neutral and ion species. Using existing data and theory, the findings were confirmed following the local thermodynamic equilibrium (LTE) hypothesis. Plasma properties such as Debye length (${\lambda }_d$), ($N_d$) and plasma frequency ($w_p$) were also studied in this study. Using a laser, we found that all plasma parameters were affected. In addition, the calculated inverse Bremsstrahlung absorption coefficients (${\alpha }_{IB}$) were altered.

Silver nanoparticles (NPs) were made using double-distilled deionized water (DDDW) and pulsing laser ablation in liquid (PLAL) with Q-switched technology (Nd:YAG) laser (energy: 80mJ, number of pulses: 500) at various wavelengths (1064nm and 532nm). The surface plasmon extinction (SPE) peaks were used to measure the PLAL process’s formation quality. The SPE spectra showed a single sharp peak at about 400nm, suggesting that pure and spherical silver was produced. The formation of silver particles was verified by UV–vis spectrophotometer absorption results. According to the AFM findings, as the wavelength of the laser beam used for preparation increased, the average grain size of the particles decreased. Finally, SEM images pointing to the produced silver nanoparticles spherical in their shape, were shown. The elemental analysis and chemical characterization with energy-dispersive X-ray spectroscopy (EDX) were performed on the produced samples. This confirmed the high purity of the obtained samples and the existence of Ag NPs.

In this work, solid-state reaction method and a two-step sintering procedure were successfully used to prepare neodymium-doped yttrium aluminum garnet (Nd:YAG) transparent dielectric ceramics. The effects of the microstructure and crystal structure of the ceramics on the microwave dielectric properties were investigated. Samples after vacuum sintered at 1600–1750^∘C and further hot isostatic pressing (HIP) at 1700^∘C had a pure YAG phase. The cell volume increased slightly after further HIP treatment compared to the vacuum-sintered ceramics. Combined with the disordered arrangement of the atoms in the HRTEM image, the lattice expansion could be explained by the entrance of larger ions into the YAG lattice. Moreover, the sintering drive provided by HIP could effectively eliminate the porosity in ceramics, increase the average grain size, and narrow the grain boundaries, which was conducive to the improvement of transmittance and quality factor (Qf) value. Finally, the sample that was vacuum sintered at 1700^∘C and then exposed to HIP had outstanding microwave dielectric characteristics: ${\epsilon }_r=10.64$, $\mathrm{\text{Qf}}=515,800$GHz and ${\tau }_f=-21$ppm/^∘C.