Working research areas

Currently, I am working on beam optics and its applications in the material science                                                                                                                                 

1. Nonlinear Optics

2. Structured Beam Optics

3. Laser Engineering

4. Light-matter interaction

Major research projects carried out till now

1. Study of optical Nonlinearity in the Absorption and Refraction

2. Structured Optical Beams generation by Diffractive optical elements

3. Direct generation of Generalized Gaussian beams from Solid State Lasers

4. Nonlinear Frequency Mixing of Generalized Gaussian Modes

5. Application of Generalized Gaussian beams in Material science and bioscience

Research articles

Journals

1. A. S. Rao, “An Intriguing Interpretation of 1D and 2D Non-Diffracting Modes in Cosine Profile,” Photonics 10(12) 1358 (2023) (https://doi.org/10.3390/photonics10121358).
2. T. Morohashi, A. S. Rao*, and T. Omatsu, “Direct generation of lower-order cylindrical vector vortex modes from an end-pumped Pr³⁺: LiYF₄ laser,” Appl. Opt. 62(34), 9183-9187 (2023) (https://doi.org/10.1364/AO.509263).
3. A. S. Rao, “Illustrations of Bessel Beams in s-Polarization, p-Polarization, Transverse Polarization, and Longitudinal Polarization,” Photonics 10(10), 1092 (2023) (https://doi.org/10.3390/photonics10101092).
4. W. R. Kerridge-Johns*, A. S. Rao, Y. Fujimoto, and T. Omatsu, “Red, orange, and dual wavelength vortex emission from Pr: WPFGF fiber laser using a microscope slide output coupler,” Opt. Exp. 31(10),16607-16614 (2023) (https://doi.org/10.1364/OE.491867).
5. A. S. Rao*, T. Morohashi, W. R. Kerridge-Johns, and T. Omatsu, “Generation of higher-order Laguerre–Gaussian modes from a diode-pumped Pr³⁺: LiYF₄ laser with an intra-cavity spherical aberration,” JOSA B, 40(2), 406-411 (2023) (https://doi.org/10.1364/JOSAB.481727) (Editiors’ Pick).
6. P. Kumar*, A. S. Rao, and T. Omatsu, “Generation of V-point polarization singularity using single phase encoding with a spatial light modulator,” Sci. Rep. 13(1), 1-7 (2023) (https://doi.org/10.1038/s41598-022-27337-x).
7. P. Kumar, N. K. Nishchal*, T. Omatsu, and A. S. Rao. "Self-referenced interferometry for single-shot detection of vector-vortex beams," Sci. Rep. 12, 1 (2022) 1-11 (https://doi.org/10.1038/s41598-022-21485-w).
8. P. Kumar, N. K. Nishchal*, T. Omatsu, and A. S. Rao, “Optical vortex array for two-dimensional exclusive-OR operation”, Appl. Phys. B 128 5 (2022) 1-7 (https://doi.org/10.1007/s00340-022-07818-7).
9. S. U. Alam*, N. K. Soni, A. S. Rao, H. He, Y. Ren, and K. W. Kenneth*, "Two-photon microscopy with enhanced resolution and SBR using hollow Gaussian beam excitation." Opt. Lett. 15 8 (2022) 2048-2051 (https://doi.org/10.1364/OL.454140).
10. A. S. Rao, T. Miike, K. Miyamoto, and T. Omatsu*, “Direct generation of 523 nm orbital Poincaré mode from a diode-pumped Pr³⁺:LiYF₄ laser with an off-axis optical needle pumping geometry.” Opt. Exp. 29 19 (2021) 30409 (https://doi.org/10.1364/OE.439491).
11. A. S. Rao, T. Miike, K. Miyamoto, and T. Omatsu*, “Optical vortex lattice mode generation from a diode-pumped Pr³⁺:LiYF₄ laser.” J. Opt. 23 (2021) 075502 (https://doi.org/10.1088/2040-8986/ac067d).
12. A. S. Rao^#*, D. Yadav^#, and G. K. Samanta, "Nonlinear frequency conversion of 3-D optical bottle beams generated using a single axicon." Opt. Lett. 46 3 (2021) 657-660 (doi.org/10.1364/OL.413899).
13. A. S. Rao, K. Miyamoto, and T. Omatsu*, “Ultraviolet intracavity frequency-doubled Pr³⁺:LiYF₄ orbital Poincaré laser.” Opt. Exp. 28 25 (2020) 37397 (doi.org/10.1364/OE.411624).
14. A. S. Rao*, L. Liu, and Y. Cai*, " A new method for generating approximate non-diffractive three dimensional micro-size optical potentials." Opt. Commun. 477 (2020) 126297 (doi.org/10.1016/j.optcom.2020.126297).
15. A. S. Rao, "Characterization of off-axis phase singular optical vortex and its nonlinear wave-mixing to generate control broad OAM spectra." Phys. Scr. 95 5 (2020) 055508 (doi.org/10.1088/1402-4896/ab7b09).
16. A. S. Rao, " Theoretical study on saturable absorption using Gaussian vortex beam z-scan." JNOPM 28 3 (2020) 1950038 (doi.org/10.1142/S0218863519500383).
17. A. S. Rao, "Analysis of multi-photon absorption: z-scan using ultra-short Gaussian vortex beam." Laser Phys. 30 2 (2019) 025403 (doi.org/10.1088/1555-6611/ab5e23).
18. A. S. Rao, "Equations for beam waist measurement of high peak power lasers.” JNOPM 28 (2019) 1950020 (doi.org/10.1142/S0218863519500206).
19. A. S. Rao, "Nonlinear spectroscopy of three-level cascade systems in the act of saturable and reverse saturable absorption." Optik 185 (2019) 14-19 (doi.org/10.1016/j.ijleo.2019.03.091).
20. A. S. Rao, “Nonlinear behavior of the population dynamics of three-level systems in the presence of single photon absorption” Chin. Phys. B 28 2 (2019) 024200 (doi.org/10.1088/1674-1056/28/2/024211).
21. A. S. Rao, A. Chaitanya,* and G. K. Samanta, "High power, ultrafast, efficient source for 266 nm." OSA cont. 2 (2019) 99-106 (doi.org/10.1364/OSAC.2.000099).
22. A. S. Rao, "Single Photon Nonlinear Absorption Spectroscopy of Cascade Energy Level Systems." Optik 179 (2019) 222 (doi.org/10.1016/j.ijleo.2018.10.197).
23. N. B. Hemanth,  A. S. Rao, V. S. Sravanthi,S. Alok, and R. Baskaran*, "Femtosecond laser pulse assisted photoporation for drug delivery in Chronic myelogenous leukemia cells" J. Photochem. Photobio. B: Bio. 187 (2018) 35 (doi.org/10.1016/j.jphotobiol.2018.07.031).
24. A. S. Rao, "Nonlinear absorption study in four and five energy level systems" Optik 171 (2018) 377 (doi.org/10.1016/j.ijleo.2018.06.088).
25. A. S. Rao,* and G. K. Samanta, "On-axis intensity modulation-free, segmented, zero-order Bessel beams with tunable ranges." Opt. Lett. 43 (2018) 3029-3032 (doi.org/10.1364/OL.43.003029).
26. S. U. Alam^#, A. S. Rao^#, A. Ghosh, P. Vaity, and G. K. Samanta*, "Nonlinear frequency doubling characteristics of asymmetric vortices of tunable, broad orbital angular momentum spectrum." Appl. Phys. Lett. 112 (2018) 171102 (doi.org/10.1063/1.5024445).
27. A. S. Rao, "Comparison of Rate Equation models for Nonlinear Absorption." Optik 158 (2018) 652 (doi.org/10.1016/j.ijleo.2017.12.170).
28. A S. Rao, "Optical limiting in the presence of simultaneous one and two photon absorption." Optik 157 (2018) 900 (doi.org/10.1016/j.ijleo.2017.11.163).
29. A. S. Rao*, and S. Alok. "One, two and three photon absorption of two level system in femto-second laser excitation." J. Opt. 46 4 (2017) 486 (doi.org/10.1007/s12596-017-0412-3).
30. A. S. Rao, M. H. Dar, N. Venkatramaiah, R. Venkatesan, and S. Alok*, “Third order optical nonlinear studies in tetra-phenyl porphyrin derivatives and its use to estimate thickness of sandwiched films.” J. Non. Opt. Phys. & Mater. 25 03 (2016) 1650039 (doi.org/10.1142/S0218863516500399).
31. G. Chakravarthy, A. S. Rao, A. Sharan*, O. S. N. Ghosh, S. Gayathri, A. K. Viswanath, M. N. Prabhakar, J. I. Song, “Understanding the effect of bound excitons on two photon absorption process in anatase TiO₂nanospheres using ultrafast pulses.” J. Non. Opt. Phys. & Mat. 25 02 (2016)1650019 (doi.org/10.1142/S0218863516500193).
32. A. S. Rao, “Theoretical study on nonlinear properties of four level systems under nano-second illumination.” Laser Phys. 25 5 (2015) 055701 (doi.org/10.1088/1054-660X/25/5/055701).

* corresponding author, ^# equal contribution

Review articles

1. A S. Rao, "Saturation effects in nonlinear absorption, refraction, and frequency conversion: a review" Optik 267 (2022) 169638 (doi.org/10.1016/j.ijleo.2022.169638).