Abstract-Efficient second-harmonic and terahertz generation from single BiB3O6 crystal using nanosecond and femtosecond lasers

 

Chandan Ghorui, A. M. Rudra, Udit Chatterjee, A. K. Chaudhary,  D. Ganesh, 

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-60-19-5643

The paper reports the efficient UV and terahertz generation from a 1.29 mm thick and Type I, 𝜃=28.9∘$\theta ={28.9}^{\circ }$ cut BiB3O6${\mathrm{B}\mathrm{i}\mathrm{B}}_3{\mathrm{O}}_6$ (bismuth triborate, BIBO) crystal using femtosecond and nanoseconds laser pulses. We have employed 800 nm wavelength pulses of 50 and 140 fs obtained from a Ti:sapphire laser amplifier and oscillators at 1 kHz and 80 MHz repetition rates, respectively. The conversion efficiency of second-harmonic generation (SHG) was ∼50%$\sim 50\mathrm{\%}$ while that obtained for terahertz (THz) generations was of the order of 1.85×10−5%$1.85\times {10}^{-5}\mathrm{\%}$. In addition, LDS-698 dye laser radiation tunable between 650–700 nm was also used as a source for SHG between the 325–350 nm range. The dye laser was pumped by SHG (532 nm) radiation from an electro-optically 𝑄$Q$-switched Nd:YAG laser having a pulse repetition rate of 10 Hz and a pulse width of 10 ns. A conversion efficiency of 4.01% was obtained for generation of UV at 343.5 nm. Finally, we have measured the transmission, refractive index, absorbance, and conductivity properties of BIBO crystal in the THz domain. We also ascertained the coherence length, relative permittivity and reflectivity of the crystal.

© 2021 Optical Society of America

Abstract-Study of terahertz emission from nickel (Ni) films of different thicknesses using ultrafast laser pulses

M. Venkatesh, S. Ramakanth, A. K. Chaudhary, and K. C. James Raju
https://www.osapublishing.org/ome/abstract.cfm?uri=ome-6-7-2342

The nickel (Ni) films of three different thicknesses, 65 nm, 135 nm and 1018 nm, were deposited by the RF magnetron sputtering technique. These films were subjected to femtosecond laser pulses of ~140 fs duration at 80 MHz repetition rate for generation of terahertz (THz) radiation. The obtained electromagnetic radiation was detected using photoconductive antennas by a sampling technique. The THz generation mechanism of Ni films is attributed to the ultrafast demagnetization process and its time depends on the Gilbert damping factor. The ascertained values of the Gilbert damping parameter of Ni films using ferromagnetic resonance (FMR) measurements lies between 0.011 and 0.0069. We have observed that the amplitude of emitted THz radiation from Ni films is proportional to Gilbert damping factor of films. The amplitude of emitted THz radiation from 65 nm Ni film is 1.19 and 1.66 times higher than 135 and 1018 nm films.

© 2016 Optical Society of America

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