Kamlesh Alti

Femtosecond laser written channel waveguides in tellurite glass

We have made and characterized a new, erbium-doped tellurite glass that has high glass transition temperature. Addition of phosphate is found to increase the phonon energy. The peak emission cross section is 6 x 10(-21) cm(2) at 1537 nm and the fluorescence lifetime of the (4)I(13/2)-(4)I(15/2) transition is 4.1 ms. We have written 2-D channel waveguides in this glass using focused, 45-fs pulses from an amplified Ti:sapphire laser at different laser energies and writing speeds. Migration of atoms towards the periphery of the waveguides occurs, leading to refractive index changes. Channels show waveguiding at 1310 nm which is promising for the fabrication of integrated lasers and broadband amplifiers.

Optimized LIBS setup with echelle spectrograph-ICCD system for multi-elemental analysis

Laser-Induced Breakdown Spectroscopy (LIBS) is well recognized as a promising tool for in situ/remote elemental analysis of environmental, archeological, clinical, and hazardous samples. With the aim of quantifying trace elements in such samples, using LIBS technique, an echelle spectrograph-ICCD system with high sensitivity and good resolution has been assembled. Various important parameters of this system were studied and optimized. Conditions for getting good quality LIBS spectra and signal for multielemental analysis have been achieved, and these are discussed and illustrated in this paper.

Control of the onset of filamentation in condensed media

Propagation of intense, ultrashort laser pulses through condensed media, like crystals of BaF{sub 2} and sapphire, results in the formation of filaments. We demonstrate that the onset of filamentation may be controlled by rotating the plane of polarization of incident light. We directly visualize filamentation in BaF{sub 2} via six-photon-absorption-induced fluorescence and, concomitantly, by probing the spectral and spatial properties of white light that is generated.

Suppression of ultrafast supercontinuum generation in a salivary protein

The first studies of the propagation of ultrafast (<45 fs) pulses of intense infrared light through protein media reveal that supercontinuum (white light) generation is severely suppressed in the presence of the protein alpha-amylase, a potential stress marker in human saliva. The continuum suppression capacity is attributed to the electron scavenging property of the protein.

Femtosecond laser induced forward transfer of indium thin films

We report utilization of the laser induced forward transfer technique to re-deposit indium thin films onto the accepter substrate using nJ laser pulses from a femtosecond laser oscillator. Keeping the accepter substrate stationary enables dots of Indium to be deposited; in contrast, linear motion of the accepter substrate facilitates deposition of lines of Indium. The effect of laser pulse energy on the deposition process is studied. The effect of translation speed of donor substrate on the laser induced forward transfer pattern is also probed and an upper limit of translation speed is established beyond which smearing is observed to occur.

SIMULATED LITHOGRAPHIC PATTERNS FOR PERIODIC ARRAYS OF ATOMIC BEAMS FOCUSED WITH SINGLE ATOMIC LENS

A new configuration of microscopic square arrays of atomic beams in the presence of TEM00 mode laser, acting as atomic lens, is proposed for atom lithography via dipole force. Simulated patterns using such configuration for rubidium atoms show the formation of nanostructures with periodicity less than λ/2.

Trace Element Analysis using Laser Induced Breakdown Spectroscopy (LIBS) Technique

Laser‐Induced Breakdown Spectroscopy (LIBS) is well recognized as a promising tool for in situ/remote elemental analysis of environmental, archeological, clinical, and hazardous samples. With the aim of quantifying trace elements in such samples, using LIBS technique, an echelle spectrograph‐ICCD system with broad range and good resolution has been assembled. Various important parameters of this system were studied and optimized. Conditions for getting good quality LIBS spectra and signal for multielemental analysis have been achieved, and these are discussed and illustrated in this paper.

White Light Generation in Human Saliva

Interaction of intense, femto‐second pulses of infrared light (800 nm) with water generates white light supercontinuum due to nonlinear optical effects. This supercontinuum was found to be suppressed by the addition of alpha amylase, a major protein in the human saliva. We have studied the suppression of supper continuum by human saliva, collected from healthy subjects with and without smoking habits. Suppression of the blue‐sided components was observed significantly in non‐smokers saliva than chain smokers.

Suppression of white light generation (supercontinuum) in biological media: a pilot study using human salivary proteins

Propagation of ultrashort pulses of intense, infrared light through transparent medium gives rise to a visually spectacular phenomenon known as supercontinuum (white light) generation wherein the spectrum of transmitted light is very considerably broader than that of the incident light. We have studied the propagation of ultrafast (<45 fs) pulses of intense infrared light through biological media (water, and water doped with salivary proteins) which reveal that white light generation is severely suppressed in the presence of a major salivary protein, &agr;-amylase.