arXiv subjects

Srikanth Sugavanam

Publications and source records attributed to Srikanth Sugavanam.

8 recordsLinked to original sources

arXiv2026

Stability analysis and quantum-limited noise properties of the Soliton-similariton fiber laser

Soliton-similariton fiber lasers have demonstrated exceptional operational stability, maintaining continuous mode-locking for weeks despite large intracavity spectral and temporal breathing. We present the first stability study of this laser, rigorously establishing that the anomalous dispersion segment that supports the soliton is the cause of this robustness. Specifically, we perform linear stability analysis of the laser employing a Jacobian-based eigenvalue decomposition and show that the eigenvalues lie within the unit circle, leading to a positive stability margin, which is indicative of the robustness of the laser against small perturbations. Furthermore, the stability margin is observed to increase with the length of the anomalous fiber segment, clearly establishing its role in pulse stabilization. Critically, integrated pulse timing jitter and relative intensity noise as obtained from quantum noise-limited laser simulations are shown to be anti-correlated to the stability margin, further validating the results of the Jacobian analysis and establishing an unequivocal link between the reported noise performance of the soliton-similariton laser to the underlying pulse stabilization mechanism mediated by the anomalous segment. The direct link of the linear stability analysis to the underlying nonlinear physics of the laser, together with its significantly lower computational overhead, establishes it as a highly effective predictive framework for assessing laser noise performance, enabling novel approaches for designing quantum noise-limited ultrafast sources.

physics.optics↗

arXiv2026

The Taguchi method for optimizing nonlinear pulse propagation in optical fibers

Understanding the nuances of nonlinear pulse propagation in optical fibers has led to several impactful applications across domains like optical communications, sensing and biophotonics. A key aspect in this regard is the use of appropriate optimization strategies for attaining requisite performance parameters. In this paper, we present the Taguchi method as a viable tool for optimizing nonlinear pulse propagation in optical fibers. We show that its use of the orthogonal arrays leads to rapid convergences to the desired pulse parameters, with even faster convergences obtained by favouring exploitation over exploration. We demonstrate the application of the method using two well-known problems from the field - the guiding center soliton, and soliton order conservation in dispersion decreasing fibers - which serve to underscore its salient features and also its potential for solution discovery across nonlinear pulse propagation problems.

physics.optics↗

arXiv2021

Computational Compressed Sensing of Fiber Bragg Gratings

State-of-the-art fiber Bragg grating interrogators utilize mature concepts and technologies like tunable lasers, optical spectrum analyzers and a combination of time, wavelength, or spatial division demultiplexing approaches. Here, we propose the use of computational compressed sensing (CS) techniques for interrogation of fiber Bragg gratings, reducing interrogator complexity by using a broadband ASE light source and single-pixel detection. We demonstrate temperature sensing using a pre-calibration approach to achieve reconstruction accuracy comparable to uncompressed measurements. We extend these principles for the interrogation of sensor networks, presenting strategies for tackling sparsity considerations. Our proof-of-principle demonstrations show how the presented computational compressed sensing techniques can provide an alternative for realizing low-complexity, small footprint interrogator configurations.

physics.ins-det↗

arXiv2021

Breather molecular complexes in a passively mode-locked fibre laser

Breathing solitons are nonlinear waves in which the energy concentrates in a localized and oscillatory fashion. Similarly to stationary solitons, breathers in dissipative systems can form stable bound states displaying molecule-like dynamics, which are frequently called breather molecules. So far, the experimental observation of optical breather molecules and the real-time detection of their dynamics have been limited to diatomic molecules, that is, bound states of only two breathers. In this work, we report on the observation of different types of breather complexes in a mode-locked fibre laser: multi-breather molecules, and molecular complexes originating from the binding of two breather-pair molecules or a breather pair molecule and a single breather. The inter-molecular temporal separation of the molecular complexes attains several hundreds of picoseconds, which is more than an order of magnitude larger than that of their stationary soliton counterparts and is a signature of long-range interactions. Numerical simulations of the laser model support our experimental findings. Moreover, non-equilibrium dynamics of breathing solitons are also observed, including breather collisions and annihilation. Our work opens the possibility of studying the dynamics of many-body systems in which breathers are the elementary constituents.

physics.optics↗

arXiv2019

Towards Ultrafast Gyroscopes Employing Real-time Intensity and Spectral Domain Measurements of Ultrashort Pulses

Active ring laser gyroscopes (RLG) operating on the principle of the optical Sagnac effect are preferred instruments for a range of applications, such as inertial guidance systems, seismology, and geodesy, that require both high bias stability and high angular velocity resolutions. Operating at such accuracy levels demands special precautions like dithering or multi-mode operation to eliminate frequency lock-in or similar effects introduced due to synchronisation of counter-propagating channels. Recently proposed bidirectional ultrafast fibre lasers can circumvent the limitations of continuous wave RLGs. However, their performance is limited due to the nature of the highly-averaged interrogation of the Sagnac effect. In general, the performance of current optical gyroscopes relies on the available measurement methods used for extracting the signal. Here, by changing the paradigm of traditional measurement and applying spatio-temporal intensity processing, we demonstrate that the bidirectional ultrafast laser can be transformed to an ultrafast gyroscope with acquisition rates of the order of the laser repetition rate, making them at least two orders of magnitude faster than commercially deployed versions. We also show the proof-of-principle for dead-band-free round trip time-resolved spectral domain measurements using the Dispersive Fourier Transform, further enhancing the gyroscopic sensitivity. Our results reveal the high potential of application of novel methods of signal measurements in mid-sized ultrafast fibre laser gyroscopes to achieve performances that are currently available only with large-scale RLGs.

physics.ins-det↗

arXiv2016

Laminar-Turbulent Transition in Raman Fiber Lasers: A First Passage Statistics Based Analysis

Loss of coherence with increasing excitation amplitudes and spatial size modulation is a fundamental problem in designing Raman fiber lasers. While it is known that ramping up laser pump power increases the amplitude of stochastic excitations, such higher energy inputs can also lead to a transition from a linearly stable coherent laminar regime to a non-desirable disordered turbulent state. This report presents a new statistical methodology, based on first passage statistics, that classifies lasing regimes in Raman fiber lasers, thereby leading to a fast and highly accurate identification of a strong instability leading to a laminar-turbulent phase transition through a self-consistently defined order parameter. The results have been consistent across a wide range of pump power values, heralding a breakthrough in the non-invasive analysis of fiber laser dynamics.

physics.optics↗

arXiv2015

Ginzburg-Landau turbulence in quasi-CW Raman fiber lasers

Fiber lasers operating via Raman gain or based on rare-earth doped active fibers are widely used as sources of CW radiation. However these lasers are only quasi-CW: their intensity fluctuates strongly on short time-scales. Here the framework of the complex Ginzburg-Landau equations, that are well known as an efficient model of mode-locked fiber lasers, is applied for the description of quasi-CW fiber lasers as well. The first ever vector model of a Raman fiber laser describes the experimentally observed turbulent-like intensity dynamics, as well as polarization rogue waves. Our results open debates about the common underlying physics of operation of very different laser types - quasi-CW lasers and passively mode-locked lasers.

physics.optics↗

arXiv2014

Stochasticity, periodicity and coherent structures in partially mode-locked fibre lasers

Physical systems with co-existence and interplay of processes featuring distinct spatio-temporal scales are found in various research areas ranging from studies of brain activity to astrophysics. Complexity of such systems makes their theoretical and experimental analysis technically and conceptually challenging. Here, we discover that radiation of partially mode-locked fibre lasers, while being stochastic and intermittent on short time scale, exhibits periodicity and long scale correlations over slow evolution from one round trip to another. The evolution mapping of intensity auto-correlation function allows us to reveal variety of spatio-temporal coherent structures and to experimentally study their symbiotic co-existence with stochastic radiation. Our measurements of interactions of noisy pulses over a time scale of thousands of non-linear lengths demonstrate that they have features of incoherent temporal solitons. Real-time measurements of spatio-temporal intensity dynamics are set to bring new insight into rich underlying nonlinear physics of practical active- and passive-cavity photonic systems.

physics.optics↗