Laser Science & Technology Centre

Chronic leg ulcers (CLU’s) are one of the most challenging medical conditions, mostly resistant to conventional therapy. Several treatment modalities are present but none have become standard of care. Autologous fat contains adipose derived stem cells (ADSC’s) which is believed to have abundant growth factors (GF’s) required for its regenerative and reparative properties. Our observational study was conducted to see the feasibility and efficacy of fat grafting in management of CLUs with complete wound healing as final outcome. 14 patients with CLUs (any etiology, >3 months and multiple ulcers were counted as individual cases if >3 cm apart) were included with coagulopathies, uncontrolled diabetes mellitus (Hba1c>9 mmol/mol) being the exclusions. Fat was harvested using standard Coleman’s technique. Study was conducted from December 2015 to December 2017 in tertiary care hospital and patients were followed up for next 24 months. All cases were evaluated clinically. Average age of wounds before intervention was 33.34 months, average wound size 16.46 cm2 and 4.9 cc of average fat was transferred underneath the ulcer. 11 out of 14 wounds healed completely within average 27.4 days and final outcome was not achieved in 3. Pain assessed using visual analogue scale (VAS) in immediate post operative period till 48 hours (telephonically). Patients were evaluated at 1 week, 1 month, 3 months and 6 months after procedure for pattern of wound healing and related complications. Fat grafting is easy, safe, effective and a minimally invasive OPD procedure with short recovery time for managing CLUs.

Abstract Computational fluid dynamics (CFD) based thermal design of a transverse flow optical cavity is carried out for 1 kW Nd3+ POCl3 liquid laser source to investigate temperature and velocity distribution in the optical pumping region of the cavity. Temperature gradient and turbulence both affect the refractive index of the liquid gain medium, which results in optical path difference (OPD), divergence and hence, poorer quality of the laser beam. The main purpose of this design is to achieve uniform flow and least temperature gradient in the optical pumping region so that the optical path difference can be minimized and a good beam quality can be achieved. CFD model has been developed for carrying out thermo-fluid simulations for this thermal system and based on these simulations, an optimum geometry of inlet ports along with their position from optical pumping region have been proposed. A user defined function (UDF) is incorporated for the input of spatially varying heat source term in each cell of the optical pumping region of the cavity. Variations in refractive index and optical path difference are estimated from the temperature data using another UDF. Simulation reveals that mass flowrate between 1.5 kg/s and 2.0 kg/s maintains the optical homogeneity of gain medium. Preliminary experiments have been carried out to demonstrate the effect of flowrate on the beam divergence and thereby exhibiting the importance of present simulation work.

Various types of sensors are used for determining the position and orientation of an object, the most commonly used being the gyroscope and the accelerometer. The two are similar from purpose point of view, but actually, they measure different things. Interestingly, when combined into a single device, they can serve as a very powerful tool for providing an array of information. Microelectromechanical sensor (MEMS) called MEMS gyroscope measures changes in the forces acting on two identical masses, oscillating and moving in opposite directions.

A fiber-optic gyroscope (FOG) is an optical device for sensing the changes in orientation, and thereby performing the function of a mechanical gyroscope, and for its operation is based on the interference of light having passed through a coil of optical fiber of very large length ~5 km.

This paper reports the open path measurement of atmospheric transmission in the spectral region of 3000–3450 nm using a mid infrared tunable lidar in New Delhi (28.7oN, 77.1oE), India. Results on the measurement of atmospheric transmission in New Delhi are reported for the first time, to the best of our knowledge. A tunable infrared lidar system has been developed in-house, which transmits laser radiation with the wavelength interval of 1 nm in the above spectral band into the atmosphere. A 200-mm-diameter Cassegrain receiver telescope with mercury cadmium telluride (MCT) detector is used to collect the backscattered radiation from the atmosphere. The reflected laser radiation received from the tower located at a distance of 400 m is used to generate the transmission spectrum. Data recorded during the daytime measurements have been considered in this paper. Transmission spectra measured over several days showed a similar pattern, which confirmed the repeatability of the system performance. The measured spectra are also compared with the SkyCalc transmission model generated using the online database. Preliminary analysis indicated that these spectra had good agreement in general with a small shift in wavelength region. We have also analyzed the HITRAN database line-by-line and identified the possible major absorbing molecules in this band. The sources of air pollutants that absorb in this band and also discussed.

The prelims comprise: Half-Title Page Title Page Copyright Page Dedication Page Table of Contents Preface

One of the major areas of global interest for scientists and engineers today is that of directed‐energy weapons (DEWs). These weapons, with the exception of particle beam and laser‐induced plasma channel, LIPC weapons, generate streams of electromagnetic energy that can be precisely directed over long distances to disable or destroy the intended targets. This chapter focuses on different categories of DEWs including high‐energy laser weapons, high power microwaves, particle beam weapons and laser‐induced plasma channel, LIPC weapons. It explores operational advantages and limitations, system anatomy, involved technologies, international status and emerging trends. The chapter explains the four major categories of DEWs: Microwave‐based DEWs, Laser‐based DEWs, Particle beam weapons (PBW) and Laser‐Induced Plasma Channel, LIPC weapons. There are two broad categories of particle beam weapons, namely the charged particle and neutral‐particle beam weapons. The particle accelerator is the source of high‐energy particle beam and is therefore the heart of the particle beam weapon system.

Metal nanoparticles especially of noble metals are used as an exogenous contrast agent for biomedical photoacoustic (PA) imaging in the tissue transmission window extending from visible to near infrared 700–1100 nm band. Different geometrical configurations of gold and silver nanoparticles like spherical core-shell, nanorod, and nanocages are promising candidates for thermoplasmonics, photothermal therapy, photothermal imaging, and photoacoustic imaging. In the current study, we simulated the photoacoustic response of gold and silica core-shell nanoparticle in water medium. Finite element simulations were carried out to study the spectral absorption response and effect of nanosecond laser pulse excitation on the spatial/temporal temperature as well as photoacoustic pressure variations of different core-shell geometry of nanoparticle. We have optimized the dimensions of gold nanosphere, gold-silica, and silica-gold core-shell geometries for optimum photoacoustic conversion efficiency. Further, the effect of shell thickness on the pulse photoacoustic signals for core-shell gold-silica and silica-gold nanoparticle has been studied. We concluded that silica-gold core-shell nanoparticles possess better photoacoustic conversion efficiency in comparison to gold nanosphere and gold-silica core-shell geometries. The prime aim of this study is to design efficient nano-probes for photoacoustic imaging, photoacoustic tomography, photothermal therapy, and drug delivery.