Current Research Areas
Low noise rare-earth doped fiber lasers
Our research aims to design and develop up to 100W continuous wave power, low noise rare-earth doped fiber lasers based on Ytterbium and Erbium. Specifically, we investigate the noise properties of conventional linear, ring cavity and master oscillator power amplifier (MOPA) laser architectures and engineer their optical characteristics such as gain, ASE and nonlinearity to enable low noise operation in both broad and narrow optical spectal bandwidths. Such lasers are useful for applications as a pump source for low noise nonlinear frequency generation, and in single-frequency operation, such laser systems find applications in atomic cooling, gravitational wave detection, high efficiency frequency doubling systems.
Low noise tunable fiber lasers
A method to develop high power fiber lasers operating at wavelengths that are not covered by rare-earth dopants is to use nonlinear frequency conversion of high power rare-earth doped fibers lasers. Our research focuses on utilizing the nonlinear effect of Stimulated Raman scattering (SRS) in optical fibers to achieve ultra-wide wavelength tunable fiber lasers with 10s of watts of optical power. Through both numerical simulations and experimental designs, we study the effect of pump laser’s noise, fiber’s dispersion and the laser architecture on the noise properties of the newly generated wavelength through SRS. Guided by these studies we aim to develop optimized pump source, nonlinear fiber medium and the architectures that can achieve low noise, ultra-wide wavelength tunable fiber lasers. Such lasers enable high performance optical communications, biological tissue coagulation, trace gas sensing and low noise tunable visible fiber lasers that are used for laser guide star, super resolution microscopy, flow cytometry and atomic quantum physics applications.
Low noise continous wave supercontinuum generation in optical fibers
Optical sources having octave spanning bandwidths have found many applications in biomedical imaging, non-destructive and non-contact testing, sensing of critical parameters and devices in manufacturing, food industries to name a few. Our research aims to develop continuous wave (CW) fiber supercontinuum sources in a low noise configuration. The advantage of CW supercontinuum over the traditional femto, pico and nanosecond pulsed supercontinuum is the high average power spectral density that enables enhanced signal to noise ratio in the above-mentioned applications. Due to its generation mechanism, CW supercontinuum naturally provides an incoherent output spectrum, and we aim to reduce the intensity noise of this incoherent spectrum. We analyze the effect of noise of different pump laser architectures, optical fibers, and supercontinuum architectures on the noise characteristics of the generated supercontinuum through both numerical simulations and experimental analysis. Such sources enable shot noise detection capability of low-coherence interferometry applications.
Beam combinable high coherence , high-power fiber lasers
For directed energy applications, optical power levels produced by single fiber laser system are not sufficient. Beam combining techniques are necessasy to reach the targeted power levels. Our research focuses on development of high coherence (narrow linewidth), multi kilowatt power fiber laser modules that are naturally compatible with beam combing laser systems. We investigate power scaling limitation effects such as Stimulated Brillouin scattering (SBS), Transverse modal instability (TMI) in these systems and develop systems that optimally mitigate these. Specifically, we deisgn optimized line broadening mechanisms for SBS suppression and develop optimzed power amplifier architectures for both TMI and SBS suppression. This research is done in collaboration with Prof V R supradeepa at CeNSE, IISc, Bengaluru, India
Applications of the fiber laser systems
We also focus on developing emerging application systems for the advanced fiber laser systems developed in our lab. Currently we are interested in the next generation low coherence interferometry applications like Fourier domain optical coherence tomography. We aim to achieve enhanced signal to noise ratios and shot noise detection capabilities in a low cost and efficient manner in these systems using our in-house developed lowl noise supercontinuum sources.
