Mahdi Shayganmanesh

In this paper, we report the design and fabrication of a surface plasmon resonance (SPR) sensor for measuring variations in the refractive index of liquid solutions. The sensor employs a simple Kretschmann configuration in which only two layers of chromium and gold with optimised thicknesses were deposited on a prism and the laser beam reflection is evaluated via image processing instead of photodiode. A computer simulation programme was developed to predict resonance curves by analysing the effect of key parameters. To validate the system, calibration experiments were carried out using sugar solutions with concentrations of 0%, 5%, 15% and 20%. The results show that the implemented SPR sensor achieves a sensitivity of 165.16 deg/RIU, an FWHM of 7 deg, a quality factor of 25.6 RIU ⁻¹ and a dynamic range of 1.00–1.37 RIU. These findings demonstrate the reproducibility and robust performance of the proposed setup, highlighting its potential as a low‐cost and reliable platform for refractive index sensing in chemical, biological and industrial applications.

In this paper, a comprehensive model was developed for analyzing the impact of optical misalignment in the presence of thermal lensing on pointing stability in laser resonators. An index was defined to estimate pointing stability during the design and simulation phases of stable laser resonators. This index was derived using transfer matrices and drew inspiration from the method for calculating misalignment sensitivity. However, unlike misalignment sensitivity which calculated the effect of optical element misalignment in the displacement of the mode axis on the active medium, this index focused on the impact of optical element misalignment in the mode axis displacement on the resonator’s output coupler. The examples presented demonstrated that this index could exhibit distinct behavior compared to misalignment sensitivity across various resonator configurations. In applications where laser pointing stability is essential, this model serves as a valuable tool for optimal design. It provides a quantitative framework for predicting pointing stability resulting from misalignment, facilitating the design and optimization of laser resonators. By quantifying permissible misalignment tolerances, this study contributes to the establishment of practical standards in laser system design. Ultimately, this research enhances high-precision laser applications in fields like beam steering, amplifier oscillators, and laser-based imaging, where maintaining pointing stability is critical.

Conventional long laser resonators impede industrial adoption due to excessive footprint and alignment sensitivity. This theoretical study presents an engineered mirror configuration for compact laser resonators, achieving significant length compression while preserving fundamental-mode beam quality. The approach involved using flat mirrors fixed together by adhering to a set of principles to sandwich the long lengths of the resonator arms. As an example, a resonator was designed with an effective length of 30 cm using paired parallel flat mirrors—a specialized configuration of flat mirrors fixed together, whereas the fundamental mode spot size on the active medium exceeded 2.8 mm, thus maintaining good dynamic stability and low sensitivity to misalignment. Theoretical analysis confirms this design enables unprecedented aggressive length reduction in laser resonators while preserving misalignment robustness. Although experimental validation remains for future work, the design framework offers practical guidelines for resonator miniaturization in industrial applications. The design is particularly transformative for fundamental mode lasers and ultrafast lasers, where traditional long resonators limit compactness.

In the present paper we have performed sets of experiments to study laser triggering high voltage switch. In this study, instead of electrical diagnostics, optical technique was utilized to characterize the discharge process. A Q-switched nanosecond Nd:YAG laser was used for triggering the switch. Dynamics of discharge, and the time delay of laser produced pre-plasma was monitored by fast photo diode signal which was connected to a fast oscilloscope. The spectrum of discharge emission was also recorded by photo spectrometer from which plasma parameters i.e. electron temperature, and density were estimated.

A model is presented for calculating the electric field profiles of transverse modes in fibres. Using this model, the electric field propagation of transverse modes was calculated and compared in both bent and straight Yb and Ho fibres. Our simulations revealed that the field intensities of the modes did not consistently increase or decrease by bending as expected, but rather fluctuated as the bending radii of the fibres changed from 1 to 100 cm. Additionally, it was observed that at certain bending radii, the modes of the fibres became deformed and transitioned into higher modes. Furthermore, the extent to which the modes stretched towards cladding due to bending was calculated. To provide a more comprehensive analysis of the results and investigate the effects of the physical parameters of the fibres on the bent fibre modes, simulation results were presented for two different V numbers and core radii.