Conference Agenda

Laser direct writing (LDW) systems offer remarkable opportunities to sculpt materials at the micro and nanoscale. However, traditional LDW methods are limited in throughput because of their inherent serial nature– material modification occurs point-by-point. Here we propose a paradigm shift for LDW systems, from point-by-point to region-by-region operations. Our approach leverages ultrasonic waves to shape the laser radiation. Piezoelectric actuators, immersed in water, generate acoustic and, thus, density or refractive index waves, stationary in space and oscillating (MHz) in time. A laser beam traveling through such an acoustically controlled medium gets diffracted and forms interference patterns as well as multiple shape-tailored laser beamlets. Synchronization of the arrival of laser pulses with respect to the refractive index oscillation enables the selection of different inference patterns or beamlet configurations at the unsurpassed speed of MHz. Our system is simple and can be easily integrated into traditional LDW systems. This allowed us preparing micro and nanostructures over a large area (~cm2) of a sample in either additive or substrative mode. We validated our idea by preparing and stitching together, while scanning a sample surface with user-selectable laser patterns, pixels with different either nanostructured colorations or wettability.

MoO3 is extensively studied in the mid infrared range due to the strong anisotropy of its optical properties. We investigate the mid-infrared thermo-optical properties of polycrystalline alpha-phase Molybdenum trioxide (-MoO3) thin films grown onto SiO2 substrates in the temperature range 20°C-250°C reporting a thermo-optic coefficient of the mean order of 10-4 K-1.

Significant advances in mid-infrared optical technology depend on the development of innovative materials blending the properties of metals and insulators. In our work, we have systematically explored the thermochromic phase transition of vanadium dioxide. By introducing tungsten doping at room temperature through pulsed laser deposition technique onto sapphire substrates, we were able to precisely tailor the material's infrared optical responses. Our control over the tungsten concentration enabled us to finely tune both the amplitude and frequency of optical phonon resonances, as well as the free-electron response.

Molybdenum disulphide (MoS2) and is a transition metal-dichalcogenides (TMD) material has layered structure. Recently it has drawn significant attention for exploring optoelectronic and photonic properties at sub-nanometre scale. The TMDs possess direct bandgap which is quite attractive for device engineering and applications in photovoltaic, energy storage, and bandgap engineered light-sources. We have synthesized 2H MoS2 using hydrothermal synthesis at 240 ⁰C for 24 h. The as synthesized powder was used for the fabrication of MoS2 thin films using femto-second pulsed laser deposition (fs-PLD). The deposited films are stoichiometrically congruent with that of synthesized material. The materials were characterised using XRD, UV-vis absorption spectroscopy and Raman spectroscopy. Figure 1 below shows the Raman spectra of MoS2 films grown at different temperatures (400 ⁰C and 600 ⁰C). Shift in the Raman bands are seen for the films deposited at different temperatures. The structural and optical properties of deposited films were analysed and compared. Such a comparative analysis may offer materials fabrication platform in future for engineering optoelectronic and photonic devices on silica glass and silicon platforms.

Terahertz (THz) time-domain spectroscopic ellipsometry (TDSE) is a powerful, self-reference, and non-destructive technique for characterizing the electrical and optical properties of a wide range of materials including semiconductors such as doped silicon wafers. By analysing the polarization changes of THz pulses reflected off the silicon samples, TDSE provides detailed information on carrier concentration, mobility, complex conductivity, and complex dielectric response. This method leverages the unique sensitivity of THz radiation to free carrier dynamics in semiconductors, enabling precise measurements of doping levels, conductivity, and hence resistivity at once. The study demonstrates the capability of THz TDSE in distinguishing between different doping types (n-type and p-type) and concentration level, providing critical insights for semiconductor research and fast quality control in silicon wafer production.