High power tunable sources

Coherent electromagnetic spectrum, ranging from deep ultra-violet (UV) to far-infrared or terahertz (THz) frequencies, is an important tool for applications in science and technology. After the invention of the lasers in 1960, research activities in the areas of communication, spectroscopy, meteorology, and medicine have undergone an unprecented growth over the last 50 years [1]. Lasers have played important role in shaping as well as resolving many theoretical aspects of modern physics in form of spectroscopic analysis. Due to the inherent mechanism of coherent generation, most of the lasers are of fixed frequency and a few have limited tunability over a narrow spectral band. In addition, broad tunability along with high optical power remains a challenge in the field of laser development. High-power semiconductor diode lasers have exhibited a possibility of achieving high power with broad tunability. However, their tunability is limited upto 2 µm owing to paucity of material availability and sophisticated electronics. In the present thesis, I have made an effort to address the issue of broad tunability with high power by using χ (2) based nonlinear optical phenomenon [2]. I design and develop χ (2) crystal based continuous-wave single-frequency optical parametric oscillators pumped by modern generation fiber lasers. Optical parametric oscillators are tunable optical sources which employ ‘long’ χ (2) nonlinear crystals in appropriately designed optical cavity. In the present case, we consider only one of the nonlinearly generated frequencies to be resonated which is also known as singly resonant optical parametric oscillator (SRO). The output wavelengths of the SRO can be coarsely tuned over a wide range (∼ 100 nm) by changing the nonlinear crystal temperature. In this talk, I will demonstrate our experimental results on the generation of high-power, single frequency radiation from visible to mid-infrared band using an SRO and analyze the spatial as well as temporal characteristics of the output beams [3, 4]. Additionally, I will also present high power frequency doubled sources working at 532 nm [5, 6]. 
References 
[1] C. H. Townes, How the laser happened: Adventures of a Scientist, Oxford University Press, 1999. 
[2] R. W. Boyd, Nonlinear Optics, Academic Press, 2008. 
[3] M. K. Shukla, P. S. Maji and R. Das , Opt. Lett., vol. 41, no. 13, pp. 3033–3036, 2016. 
[4] M. K. Shukla and R. Das, IEEE J. Sel. Top. Quant. Electron., vol. 24, pp. 1–6, 2018.
[5] M. K. Shukla, S. Kumar, and R. Das, IEEE Photon. Technol. Lett., vol. 27, pp. 1379–  1382, 2015
6] M. K. Shukla, S. Kumar, and R. Das, Appl. Phys. B, vol. 122, pp. 114, 2016