Research

• My research focuses on the following areas:

  
  

  1) High-power from phase-locked lasers:

  Lasers are the key components for many branches of science and technology and also serve as fundamental tools for studying other systems. Particularly, lasers with very high power and ideal beam quality have a large potential in scientific research, material processing, communication, medical, industrial and defense applications, and research in this direction has been in progress ever since the invention of lasers. High-power lasers often have beam quality, stability, and heat dissipation inferior to those of lower-power lasers. The phase locking of several lasers is a promising approach to synthesize high-power optical sources with ideal beam quality. However, the phase locking of many lasers is a challenging task, since it requires, at the very least, a common lasing frequency to all the lasers, a prospect that vanishes exponentially with the number of lasers. Our group activities are focused on to find solutions to overcome such limitations, and thereby to push the upper limit on the number of lasers that can be phase locked, and hence to increase the output powers while maintaining the ideal beam quality.

  References:

  1. S. Mahler, M. L. Goh, C. Tradonsky, A. A. Friesem, and N. Daivdson, "Improved phase locking of laser arrays with nonlinear coupling," Physical Review Letters 124, 133901 (2020).
  2. M. Nixon, E. Ronen, A. A. Friesem, and N. Davidson, "Observing geometric frustration with thousands of coupled lasers," Physical Review Letters 110, 184102 (2013).
  3. V. Pal, S. Mahler, C. Tradonsky, A. A. Friesem, and N. Davidson, "Rapid fair sampling of the XY spin Hamiltonian with a laser simulator," Physical Review Research 2, 033008 (2020).
  4. C. Tradonsky, V. Pal, R. Chriki, N. Davidson, and A. A. Friesem, "Talbot diffraction and Fourier filtering for phase locking an array of lasers," Applied Optics 56, A126 (2017).
  5. C. Tradonsky, M. Nixon, E. Ronen, V. Pal, R. Chriki, A. A. Friesem, and N. Davidson, "Conversion of out-of-phase to in-phase order in coupled laser arrays with second harmonics," Photonics Research 3, 77 (2015).
  6. S. Karuseichyk, V. Pal, S. Sahoo, G. Beaudoin, I. Sagnes, and F. Bretenaker, "Investigation of noise correlations in the phase-locked class-A VECSEL," Optics Express 31, 41713 (2023).
  7. V. Dev, A. N. K. Reddy, and V. Pal, "Generating high-energy densities by side lobe suppression in the far-field of phase locked lasers," Journal of Optical Society of America B 39, 2254 (2022).

3) Quantum-inspired computing with lasers:

Optimization plays a crucial role in making decisions and in analyzing systems. Specifically, it deals with finding the best solution from among many feasible solutions (for example, traveling salesman problem). Such problems are ubiquitous across social science, biology, chemistry, physics, engineering, computer science, big data and artificial intelligence. Many such problems are classified as computationally hard problems (belong to non-deterministic polynomial time (NP)-hard or NP-complete complexity classes), and solving them efficiently has been beyond the reach of modern computers. Solving them efficiently and rapidly with physical systems has become an emrging field of research. Physical optimization relies on finding the ground state of a complex system as a physical analogy to the optimization problem. 

There has been significant interest in building efficient solvers that are based on physical systems, and recently some of have realized. These include solvers that invlove coupled lasers, Bose-Einstein condenstae (BEC) polaritons and optical parametric oscillators. Particularly, our activities are focused on to build a rapid and efficient solver based on coupled lasers to solve these class of problems.

References:

1. V. Pal, S. Mahler, C. Tradonsky, A. A. Friesem, and N. Davidson, "Rapid fair sampling of the XY spin Hamiltonian with a laser simulator," Physical Review Research 2, 033008 (2020).
   
2. C. Tradonsky, I. Gershenzon, V. Pal, R. Chriki, A. A. Friesem, O. Raz, and N. Davidson, "Rapid laser solver for the phase retrieval problem," Science Advances 5, eaax4530 (2019).
3. V. Pal, C. Tradonsky, R. Chriki, A. A. Friesem, and N. Davidson, "Observing dissipative topological defects with coupled lasers," Physical Review Letters 119, 013902 (2017).
4. M. Nixon, E. Ronen, A. A. Friesem, and N. Davidson, "Observing geometric frustration with thousands of coupled lasers," Physical Review Letters 110, 184102 (2013).
5. M. Nixon, O. Katz, E. Small, Y. Bromberg, A. A. Friesem, Y. Silberberg, and N. Davidson, "Real-time wavefront shaping through scattering media by all optical feedback," Nature Photonics 7, 919 (2013).
6. S. Karuseichyk, V. Pal, S. Sahoo, G. Beaudoin, I. Sagnes, and F. Bretenaker, "Investigation of noise correlations in the phase-locked class-A VECSEL," Optics Express 31, 41713 (2023).

3) Laser beam shaping / Structured light:

Generation of optical fields with complex spatial and temporal distribution has attracted considerable interest due to numerous applications, both in fundamental science as well as engineering applications, in various fields. Typically, the output from a laser source consists of a Gaussian distribution, which is undesirable for many applications. However, in recent years, it has become possible to control the distribution of light in the spatial and temporal domain, which allows to produce spatially variant polarization states, exotic phase structures and tailored intensity patterns. The structured light with a daisy-petal-like intensity pattern was used to probe planer and non-planner surface displacements at picometer scale resolution. This has opened a route to measure weak radiation pressure and optical manipulation of liquid/solid interface that possess the potentials for applications in opto-fluidics, microfluidics, and gravitational waves detection. A synthetic chiral structured light was shown to efficiently control chiral light-matter interaction, and provides the possibility for drug development. The optical vortices were exploited to probe magnetism in materials. The well- known Rayleigh limit was sown to overcome by structured illumination, and thus allowed to achieve super- resolution in the imaging techniques. Very recently, compressive three-dimensional super-resolution microscopy with speckle-saturated fluorescence excitation was demonstrated. Further, polarization based speckle-field digital holograpic microscopy was also shown to probe features in the biological tissues with enhanced spatial resolution and controlled coherent noise reduction. Moreover, structured light is also deployed in many other fields, such as optical metrology, optical communications, optical trapping and manipulations, and atomtronic devices.

References:

1. A. N. Jena, T. M. Hayward, A. Kumari, A. Majumder, J. Devara, R. Menon, K. P. Singh, and V. Pal, "Extended depth-of-focus femtosecond laser pulses for flexible micromachining," Optics Letters (2025) [In press].
2. A. Kumari, V. Dev, and V. Pal, "Abrupt autofocusing of circular Airy derivative beams in complex media," Optics & Laser Technology 183, 112319 (2025).
3. S. Karuseichyk, I. Audoin, V. Pal, and F. Bretenaker, "Non-symmetrical vortex beam shaping in VECSEL laser arrays," Photonics Research 13, 1600 (2025).
4. A. Kumari, V. dev, T. M. Hayward, R. Menon, and V. Pal, "Generating optical vortex needle beams with a flat diffractive lens," Journal of Applied Physics 136, 113105 (2024).
5. V. Dev, and V. Pal, "Probing topological charge of discrete vortices," Physical Review Applied 20, 034071 (2023).
6. V. Dev, A. N. K. Reddy, A. V. Ustinov, S. N. Khonina, and V. Pal, "Auto-focusing and self-healing properties of aberration laser beams in a turbulent media," Physical Review Applied 16, 014061 (2021).
7. C. Tradonsky, S. Mahler, G. Cao, V. Pal, R. Chriki, A. A. Friesem, and N. Davidson, "High-resolution digital spatial control of highly multimode laser," Optica 8, 880 (2021).

References:

1. V. Pal, C. Tradonsky, R. Chriki, A. A. Friesem, and N. Davidson, "Observing dissipative topological defects with coupled lasers," Physical Review Letters 119, 013902 (2017).
2. A laser model for cosmology, Nature 549, 163 (2017).
3. Cooperating lasers make topological defects, APS focus story -- https://physics.aps.org/articles/v10/79
4. S. Mahler, V. Pal, C. Tradonsky, R. Chriki, A. A. Friesem, and N. Davidson, "Dynamics of disspative topological defects in coupled phase oscillators," Journal of Physics B: At. Mol. Opt. Phys. 52, 205401 (2019).
5. L. Lu, J. D. Joannopoulos, and M. Soljacic, "Topological photonics," Nature Photonics 8, 821 (2014).

Group Member

Present members:

• Anita Kumari (August 2021-present)
  
• Love Kumar Sharma (January 2022-present)
  
• Rajneesh Fulara (January 2023-present)
  
• Adityanarayan Jena (August 2023-present)
  

Master students:    

• Ayushi Sood  (August 2024-present)
• Bhanu Pratap Singh Rathore (August 2024 - present) 

Former members:

PhD students:

• Vasu Dev  (August 2018-June 2023); Thesis title: Generation and characterization of spatially controlled structured light with exotic propagation properties. [Presently working as a postdoctoral fellow at Center for Quantum Technologies, National University of Singapore (NUS), Singapore.]
  

Master and summer students:

• Rishabh Sahoo (Summer Intern) (Pursuing B.Tech in Engineering Physics, IIT Guwahati)
  
• Sakshi Raheja (M.Sc. student)
  
• Parmiti Gupta (Summer Intern, B.Tech-EP IIT Guwahati) (Pursuing master program at Abbe School of Photonics, Jena, Germany)
  
• Sahil Sahoo (M.Sc. student) (Pursuing PhD at Ariel University, Israel)
  
• Vivek (M.Sc. student) (Teaching staff at Akash Institute, Delhi)
  
• Manisha Rajpurohit (M.Sc. student)
  
• Pragya Sharma (M.Sc. student) (Pursuing integrated PhD program in the framework of Max Planck School of Photonics at the Friedrich-Alexander-Universität Erlangen-Nürnberg, Bavaria, Germany)
• Sachleen Singh (M.Sc. student) (Pursuing PhD in the group of Prof. Andrew Forbes at University of the Witwatersrand, Johannesburg, South Africa)
  
• Aishwarya CB (Summer intern)
• Vidisha Rao (M.Sc. student)
• Ishmeet Singh Chawla (MSc. student) (Pursuing PhD at IIT Kanpur)
  
• Sobhit Gupta (M.Sc. student)
• Karmender (M.Sc. student)
  

Lab Facility

Publications

• 2025
• 2024
• 2023
• 2022
• 2021
• 2020
• 2019
• 2018
• 2017
• 2016
• 2015
• 2013
• 2011
• 2010

Open Position

• PhD positions are available. Highly motivated candidates having interest in the field of Laser Physics, Optics & Photonics are encouraged to apply. Interested candidates can contact on vishwa.pal@iitrpr.ac.in.
• Postdoc positions: Candidates with background in the field of Laser Physics, Optics & Photonics can send your CV on vishwa.pal@iitrpr.ac.in
  

Teaching

Undergraduate:

• Optics & Photonics (PH303)
  
• Engineering Photonics (PH457)
• Technology Museum Lab (GE101)
• Physics Lab (PH102)

Postgraduate & PhD:

• Modern Optics (PH511)
• Nonlinear Optics (PH510)
• Experimental Methods (PH422)
• Laser Physics (PH614)
• Physics of EM Waves (PH603)
• Physics Lab II (PH510)
  

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