Rajendhar Junjuri

• Ph.d (Physics)
• Postdoctoral reasearcher at Leibniz Institute of Photonic Technology

Non-resonant background (NRB) plays a significant role in coherent anti-Stokes Raman scattering (CARS) spectroscopic applications. All the recent works primarily focused on removing the NRB using different deep learning methods, and only one study explored the effect of NRB. Hence, in this work, we systematically investigated the impact of NRB vari...

Broadband Coherent anti-Stokes Raman (BCARS) microscopy is an imaging technique that can acquire full Raman spectra (400–3200 cm⁻¹) of biological samples within a few milliseconds. However, the CARS signal suffers from an undesired non-resonant background (NRB), deriving from four-wave-mixing processes, which distorts the peak line shapes and reduc...

Raman spectroscopy, renowned for its unique ability to provide a molecular fingerprint, is an invaluable tool in industry and academic research. However, various constraints often hinder the measurement process, leading to artifacts and anomalies that can significantly affect spectral measurements. This review begins by thoroughly discussing the or...

We report the standoff/remote identification of post-consumer plastic waste by utilizing a low-cost and compact standoff laser-induced breakdown spectroscopy (ST-LIBS) detection system. A single plano-convex lens is used for collecting the optical emissions from the plasma at a standoff distance of 6.5 m. A compact non-gated Czerny–Turner charge-co...

Broadband Coherent Anti-Stokes Raman Scattering (BCARS) is a valuable spectroscopic imaging tool forestimating the biological variance of cells in biomedical applications.

: Non-resonant background (NRB) plays a significant role in coherent anti-Stokes Raman scattering (CARS) spectroscopic applications. All the recent works primarily focused on removing the NRB using different deep learning methods, and only one study explored the effect of NRB. Hence, in this work, we systematically investigated the impact of NRB va...

We explore the possibility of extending the LIBS application combined with machine learning for the identification of optical isomers. Three sets of optical isomers, viz., Tryptophan, Alanine, and Leucine, were chosen to demonstrate this feasibility. Each set comprises D, L, and DL isomers. Identification of specific optical isomers is crucial in t...

Identification of human sex from cadaver examination is crucial for various fields like forensic odontology and archaeology. Sex recognition can be very challenging if the cadaver is exposed to extreme temperature and/or pressure. As the hardest part of the body, tooth remains can be useful in such circumstances. In this report, we demonstrate a pr...

The nonresonant background (NRB) contribution to the coherent anti-Stokes Raman scattering (CARS) signal distorts the spectral line shapes and thus degrades the chemical information. Hence, finding an effective approach for removing NRB and extracting resonant vibrational signals is a challenging task. In this work, a bidirectional LSTM (Bi-LSTM) n...

The present work aims to demonstrate the capabilities of Laser-induced Breakdown Spectroscopy (LIBS) coupled with a multivariate technique for rapid quantification and classification of old Indian coins made of various alloys. Thirteen old Indian coins in different years of circulation, (1922–1986) were selected for the study. The concentrations we...

Coherent anti-Stokes Raman scattering (CARS) is a well-known third-order non-linear spectroscopic technique utilized to analyze the molecule structures. However, it has a coherent non-resonant background (NRB) alongside with Raman resonant, thus, it is difficult to extract the Raman part. In this work, the Raman signal is extracted from the CARS sp...

We report the retrieval of the Raman signal from coherent anti-Stokes Raman scattering (CARS) spectra using a convolutional neural network (CNN) model. Three different types of non-resonant backgrounds (NRBs) were explored to simulate the CARS spectra viz (1) product of two sigmoids following the original SpecNet model, (2) Single Sigmoid, and (3)...

We report a rapid and simplified approach for modeling the temporal evolution of the plasma temperature. The use of only two emission lines makes this technique simple, accurate and fast. Usually, multiple emission lines are required for estimating plasma temperature using Boltzmann/Saha-Boltzmann plot. But, in several cases, either multiple emissi...

We report the studies on the automatic extraction of the Raman signal from coherent anti-Stokes Raman scattering (CARS) spectra by using a convolutional neural network (CNN) model. The model architecture is adapted from literature and retrained with synthetic and semi-synthetic data. The synthesized CARS spectra better approximate the experimental...

The laser induced plasma (LIP) of tungsten is studied using space-resolved laser induced breakdown spectroscopy (SR-LIBS). In the present work a Q-switched Nd:YAG laser working at wavelength of 532 nm having maximum energy of 600 mJ and pulse duration of 7 ns with repetition rate of 1 Hz is used to generate the plasma onto the target sample surface...

We present the spatial and temporal characterization of the copper (Cu) plasma produced by the femtosecond laser filaments. The filaments of various lengths and intensities were generated with the aid of three different focusing lenses. Further, the filamentation induced breakdown spectroscopy (FIBS) measurements were carried out for each filament...

In the present work, laser-induced plasma (LIP) of Mo is studied using both time and space resolved laser-induced breakdown spectroscopy (LIBS) in air as a function of incident laser energy. For this a second harmonic Q-switched Nd:YAG laser having pulse width of 7 ns and repetition rate of 1 Hz is used. The Boltzmann plot method is employed to est...

We report the identification of explosive mixtures using LIBS combined with the multivariate approach. Principal component analysis (PCA) has been employed for the analysis. All the character emissions were deployed for the PCA and excellent discrimination among the samples has been demonstrated.

Plastics recycling can help tackle the vast problem of plastic waste pollution, but accurate identification of plastic type is a crucial step to make such schemes viable. Recently, we enlisted laser-induced breakdown spectroscopy (LIBS) and machine learning to create an approach for rapidly sorting plastic waste—at very low cost.

We present, rapid and efficient identification of ten different types of post-consumer plastics obtained from a local recycling unit by deploying a low cost, compact CCD spectrometer in laser-induced breakdown spectroscopy (LIBS) technique. For this investigation, spectral emissions were collected by an Echelle spectrograph equipped with an intensi...

We present results of the classification contest organized for the EMSLIBS 2019 conference. For this publication, we chose only the five best approaches and discussed their algorithm in detail. The main focus of the contest reflected both recent and long-term challenges of Laser-Induced Breakdown Spectroscopy (LIBS) data processing. The contest was...

In this manuscript, the time-resolved laser-induced breakdown spectroscopy (LIBS) on tungsten target in air and the coexistence of LTE among atoms and ions as well as the fulfillment of optically thin plasma condition are reported. The laser-induced plasma (LIP) of tungsten is generated by focusing the second harmonic of a Q-switched Nd:YAG laser o...

We report the development and optimization of a compact standoff laser-induced breakdown spectroscopy (ST-LIBS) system for the investigation of explosives combined with multivariate approaches. ST-LIBS in tandem with the artificial neural network (ANN) is exploited for the first time towards the identification of explosives to the best of our knowl...

Laser-induced copper plasma is investigated experimentally and theoretically. Laser-induced plasma on the surface of the copper sample is generated by focusing a nanosecond (∼7 ns) laser pulse. The experiment is performed in the ambient atmosphere at three different focal positions (lens to sample distances). The main objective of this work is to i...

Pure and manganese chloride (MnCl2) doped l-arginine maleate dihydrate (LAMD) single crystals are synthesized by slow solvent evaporation technique. Three different doping concentrations are used for the study. The grown crystals are confirmed by single crystal X-ray analysis. Laser-induced breakdown spectroscopy is used to ascertain the presence o...

We report the identification of five extensively used post-consumer plastics using femtosecond laser-induced breakdown spectroscopy (fs-LIBS) technique. All the samples were obtained from a local recycling unit. An ultra-fast amplifier system delivering pulses of ~ 50 fs pulse duration was used for the investigation. Initially, a 2D scatter plot ap...

The slow solvent evaporation technique has been employed for the synthesis of l-arginine perchlorate (LAPCl) single crystals. The grown crystals are doped with 1, 2 and 3 mol% of MnCl2. The Powder X-ray Diffraction (PXRD) analysis confirmed that the pure and doped crystals belong to the orthorhombic crystal system with non-centrosymmetric space gro...

We report an accurate recognition of ten different types of postconsumer plastics, including five extensively used basic plastics, by laser induced breakdown spectroscopy (LIBS). Ratiometric and correlational analysis have been performed for the classification in which C/H ratio yielded partial discrimination while an excellent correlation has been...

In the present work, the transient evolution of laser induced plasma (LIP) of three different copper alloys are reported in order to identify the optimized temporal window for the implementation...

We report the 'standoff detection' of explosives at 1 m in laboratory conditions, for the first time in India, using Laser Induced Breakdown Spectroscopy combined with multivariate analysis. The spectra of a set of five secondary explosives were recorded at a distance of 1 m from the focusing as well as collection optics. The plasma characteristics...

p>An experimental design based on spectral construction, which has potential to minimise the sample consumption, the number of laser shots and time required to collect the data from laser induced breakdown spectroscopy for identification of the explosive materials is reported in the study. This approach is an ideal solution in the field of hazardou...

We report characteristic properties of laser induced plasma of optical isomers in ambient atmospherE.Plasma temperature and electron density are determined and classification performed using ratiometrics/multivariate approaches.