Suman Anand - Academia.edu (original) (raw)

Papers by Suman Anand

Journal of the Optical Society of America B, 2016

Optical whispering gallery modes (WGMs) were observed in elastic scattering spectra recorded from... more Optical whispering gallery modes (WGMs) were observed in elastic scattering spectra recorded from oil-in-water emulsion droplets in a microfluidic channel. Droplets with diameters ranging between 15 and 50 μm were trapped by optical tweezers near the tip of a single mode fiber that enabled the excitation of the WGMs using a tunable laser. Quality factors of the WGMs were observed to increase with droplet size. WGMs with quality factors of more than 10 4 were observed for droplets with diameters around 45 μm. In some cases, recorded WGMs drifted monotonically to the blue end of the spectrum due to droplet dissolution in the host liquid. Fluctuating spectral shifts to both blue and red ends of the spectrum were also observed. These were attributed to the presence of randomly diffusing particulate contaminants in the droplet liquid, indicating the potential of optically trapped droplet resonators for optical sensing applications.

Lab on a Chip, 2014

Fluorescent proteins are indispensable for selective, quantitative visualization of localization,... more Fluorescent proteins are indispensable for selective, quantitative visualization of localization, dynamics, and interactions of key molecular constituents of live cells. Incorporation of fluorescent proteins into an optical cavity can lead to a significant increase in fluorescence signal levels due to stimulated emission and light amplification in the cavity, forming a laser with biological gain medium. Utilization of lasing emission from fluorescent biological molecules can then greatly enhance the performance of fluorescence-based biosensors benefiting from the high sensitivity of non-linear lasing processes to small perturbations in the cavity and the gain medium. Here we study optofluidic biolasers that exploit active liquid optical resonators formed by surface-supported aqueous microdroplets containing purified yellow fluorescent protein or a suspension of live E. coli bacterial cells expressing the fluorescent protein. We first demonstrate lasing in fluorescent protein solutions at concentrations as low as 49 μM. Subsequently, we show that a single fluorescent bacterial cell of micrometre size confined in a droplet-based cavity can serve as a laser gain medium. Aqueous droplet microcavities allow the maintenance of the bacterial cells under conditions compatible with unimpeded growth. Therefore, our results also suggest a direct route to microscopic sources of laser light with self-regenerating gain media.

We demonstrate e-cient coupling to the optical whispering gallery modes of a spherical resonator ... more We demonstrate e-cient coupling to the optical whispering gallery modes of a spherical resonator consisting of a liquid droplet embedded in another liquid medium. Whis- pering gallery mode particle sensing experiment is commonly performed with solid resonators, whereby the sensing volume is limited to the weak evanescent tail of the mode near the resonator surface. In this work, we demonstrate e-cient coupling to the optical whispering gallery modes by introducing a portable, all liquid emulsion microdroplet resonator held in a single beam optical trap. We have observed coupling to the fundamental whispering gallery modes of 10 to 60"m diameter emulsion droplets at 1550nm. The experimental challenges towards making, stabilizing and coupling to the droplet resonators are also addressed in this paper. Light inside a microspherical cavity is conflned by total internal re∞ections (TIRs) at the interface between the microsphere and the surrounding medium. The electromagnetic waves c...

The rapid growth of Organic Light Emitting devices is of considerable interest due to their poten... more The rapid growth of Organic Light Emitting devices is of considerable interest due to their potential application in flexible, cost-competitive and large screen flat-panel displays. So, there has been much effort put into the development of novel emitters for use in OLED applications. Unlike fluorescence, phosphorescence makes use of both singlet and triplet excited states, suggesting the potential for reaching a maximum internal efficiency of 100%. Recently, there has been interest in the use of triplet emitting compounds primarily focusing on trivalent iridium complexes. In this work we report the synthesis of Ir(ppy)3 and its characterization by different techniques like DTA/TGA, FTIR, UV-Visible absorption, PL measurements etc. For making OLED, Ir(ppy)3 is doped in different host materials like TPD etc. The device configuration is ITO/TPD-5% Ir(ppy)3/Alq3/LiF/Al.The EL and I-V characteristics have also been measured.

Proceedings of SPIE - The International Society for Optical Engineering, 2012

The use of optical tweezers for the analysis of aerosols is valuable for understanding the dynami... more The use of optical tweezers for the analysis of aerosols is valuable for understanding the dynamics of atmospherically relevant particles. However to be able to make accurate measurements that can be directly tied to real-world phenomena it is important that we understand the influence of the optical trap on those processes. One process that is seemingly straightforward to study with these techniques is binary droplet coalescence, either using dual beam traps, or by particle collision with a single trapped droplet. This binary coalescence is also of interest in many other processes that make use of dense aerosol sprays such as spray drying and the use of inhalers for drug delivery in conditions such as asthma or hay fever. In this presentation we discuss the use of high speed (~5000 frames per second) video microscopy to track the dynamics of particles as they approach and interact with a trapped aqueous droplet and develop this analysis further by considering elastic light scattering from droplets as they undergo coalescence. We find that we are able to characterize the re-equilibration time of droplets of the same phase after they interact and that the trajectories taken by airborne particles influenced by an optical trap are often quite complex. We also examine the role of parameters such as the salt concentration of the aqueous solutions used and the influence of laser wavelength.

The Journal of Physical Chemistry A, 2013

ISIJ international, 2006

High input power density and shorter on-time during pulsed laser spot welding results in high pea... more High input power density and shorter on-time during pulsed laser spot welding results in high peak temperature, steep heating and cooling cycles, which are difficult to mea-sure experimentally.1–3) A quantitative knowledge of the weld thermal cycle is prerequisite for ...

Quantum Electronics, IEEE …, 2002

Abstract—Experimental observations of the phenomenon of spectral switching are made for a class o... more Abstract—Experimental observations of the phenomenon of spectral switching are made for a class of partially coherent light incident on a circular aperture. The on-axis spectrum of the light in the far-field is different from the spectrum of the light at the aperture. It is shown ...

Optics in the Life Sciences Congress, 2017

Journal of Nanoscience and Nanotechnology, 2010

The reaction of [Ir(ppy)2(micro-Cl)]2 (ppy = 2-pyridiylphenyl) with a substituted bpy ligand (5-b... more The reaction of [Ir(ppy)2(micro-Cl)]2 (ppy = 2-pyridiylphenyl) with a substituted bpy ligand (5-bromo-2,2'-bipyridiyl, 5,5'-dibromo-2,2'-bipyridiyl, 5-ethynyl-2,2'-bipyridiyl) affords [Ir(ppy)2R-(bpy)-R'](CIO4) (R = H, R' = Br (1); R = R, R' = Br (2); R = H, R' = ethynyl (3)) in high yield. The structural, physical, and electrochemical properties of the iridium complexes 1, 2, and 3 were characterized by elemental analysis, NMR and optical spectroscopy, cyclic voltammetry, and X-ray structural analysis.

Optical Trapping …, Jan 1, 2011

Abstract We make use of surface acoustic wave nebulization to introduce airborne particles into o... more Abstract We make use of surface acoustic wave nebulization to introduce airborne particles into optical traps in a robust and repeatable manner. We demonstrate the facile loading of aerosols such as organic liquids and solid particles.

Bulletin of Materials Science, 2004

... Page 6. Suman Anand and ON Srivastava 118 Figure ... sites. Acknowledgements The authors are ... more ... Page 6. Suman Anand and ON Srivastava 118 Figure ... sites. Acknowledgements The authors are grateful to Dr Vikram Kumar, Director, National Physical Laboratory, New Delhi, Prof. AR Verma and Prof. RP Rastogi for encouragement. ...

The rapid growth of Organic Light Emitting devices is of considerable interest due to their poten... more The rapid growth of Organic Light Emitting devices is of considerable interest due to their potential application in flexible, cost-competitive and large screen flat-panel displays. So, there has been much effort put into the development of novel emitters for use in OLED applications. Unlike fluorescence, phosphorescence makes use of both singlet and triplet excited states, suggesting the potential for reaching a maximum internal efficiency of 100%. Recently, there has been interest in the use of triplet emitting compounds primarily focusing on trivalent iridium complexes.

ursiweb.intec.ugent.be

The rapid growth of Organic Light Emitting devices is of considerable interest due to their poten... more The rapid growth of Organic Light Emitting devices is of considerable interest due to their potential application in flexible, cost-competitive and large screen flat-panel displays. So, there has been much effort put into the development of novel emitters for use in OLED applications. Unlike fluorescence, phosphorescence makes use of both singlet and triplet excited states, suggesting the potential for reaching a maximum internal efficiency of 100%. Recently, there has been interest in the use of triplet emitting compounds primarily focusing on trivalent iridium complexes.

MAPAN-Journal of Metrology Society of India

ABSTRACT We have investigated the dispersion properties of photonic crystal waveguide resonators.... more ABSTRACT We have investigated the dispersion properties of photonic crystal waveguide resonators. A passive InGaAsP/InP slab waveguide structure was used for the fabrication of the samples. The PhC waveguide resonators were defined by the omission of several rows of holes along the GammaKappa or GammaMu direction of a triangular photonic crystal lattice. In addition, mirrors with a thickness of 1 to 4 rows of holes were inserted into the waveguide. An optimized dry etch process was used to etch the patterns to a depth of 3.5 µm through the waveguide layer. The group delay of the PhC devices was measured using the phase shift technique. The signal of a tunable laser was modulated at 3 GHz using a LiNbO3 Mach-Zehnder modulator and detected with a high-frequency lightwave receiver. A phase sensitive detection with a network analyer measured the phase shift of the transmitted signal, which is proportional to the group delay. Close to the center of the resonances, the chromatic dispersion reaches values of -250 ps/nm and 250 ps/nm. This corresponds to the chromatic dispersion of 15 km standard fiber.

Laser Resonators, Microresonators, and Beam Control XVI, 2014

Holography, Diffractive Optics, and Applications, 2002

ABSTRACT

Optics Communications, 2006

... [10] S. Anand and HC Kandpal, J. Opt. A: Pure Appl. Opt. 6 (2004), p. 177. Full Text via Cros... more ... [10] S. Anand and HC Kandpal, J. Opt. A: Pure Appl. Opt. 6 (2004), p. 177. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (12). [11] J. Pu, H. Zhang and S. Nemoto, Opt. ... [14] S. Anand, BK Yadav and HC Kandpal, J. Opt. Soc. Am. A. 19 (2002), p. 2223. ...

Journal of the Optical Society of America B, 2016

Optical whispering gallery modes (WGMs) were observed in elastic scattering spectra recorded from... more Optical whispering gallery modes (WGMs) were observed in elastic scattering spectra recorded from oil-in-water emulsion droplets in a microfluidic channel. Droplets with diameters ranging between 15 and 50 μm were trapped by optical tweezers near the tip of a single mode fiber that enabled the excitation of the WGMs using a tunable laser. Quality factors of the WGMs were observed to increase with droplet size. WGMs with quality factors of more than 10 4 were observed for droplets with diameters around 45 μm. In some cases, recorded WGMs drifted monotonically to the blue end of the spectrum due to droplet dissolution in the host liquid. Fluctuating spectral shifts to both blue and red ends of the spectrum were also observed. These were attributed to the presence of randomly diffusing particulate contaminants in the droplet liquid, indicating the potential of optically trapped droplet resonators for optical sensing applications.

Lab on a Chip, 2014

Fluorescent proteins are indispensable for selective, quantitative visualization of localization,... more Fluorescent proteins are indispensable for selective, quantitative visualization of localization, dynamics, and interactions of key molecular constituents of live cells. Incorporation of fluorescent proteins into an optical cavity can lead to a significant increase in fluorescence signal levels due to stimulated emission and light amplification in the cavity, forming a laser with biological gain medium. Utilization of lasing emission from fluorescent biological molecules can then greatly enhance the performance of fluorescence-based biosensors benefiting from the high sensitivity of non-linear lasing processes to small perturbations in the cavity and the gain medium. Here we study optofluidic biolasers that exploit active liquid optical resonators formed by surface-supported aqueous microdroplets containing purified yellow fluorescent protein or a suspension of live E. coli bacterial cells expressing the fluorescent protein. We first demonstrate lasing in fluorescent protein solutions at concentrations as low as 49 μM. Subsequently, we show that a single fluorescent bacterial cell of micrometre size confined in a droplet-based cavity can serve as a laser gain medium. Aqueous droplet microcavities allow the maintenance of the bacterial cells under conditions compatible with unimpeded growth. Therefore, our results also suggest a direct route to microscopic sources of laser light with self-regenerating gain media.

We demonstrate e-cient coupling to the optical whispering gallery modes of a spherical resonator ... more We demonstrate e-cient coupling to the optical whispering gallery modes of a spherical resonator consisting of a liquid droplet embedded in another liquid medium. Whis- pering gallery mode particle sensing experiment is commonly performed with solid resonators, whereby the sensing volume is limited to the weak evanescent tail of the mode near the resonator surface. In this work, we demonstrate e-cient coupling to the optical whispering gallery modes by introducing a portable, all liquid emulsion microdroplet resonator held in a single beam optical trap. We have observed coupling to the fundamental whispering gallery modes of 10 to 60"m diameter emulsion droplets at 1550nm. The experimental challenges towards making, stabilizing and coupling to the droplet resonators are also addressed in this paper. Light inside a microspherical cavity is conflned by total internal re∞ections (TIRs) at the interface between the microsphere and the surrounding medium. The electromagnetic waves c...

The rapid growth of Organic Light Emitting devices is of considerable interest due to their poten... more The rapid growth of Organic Light Emitting devices is of considerable interest due to their potential application in flexible, cost-competitive and large screen flat-panel displays. So, there has been much effort put into the development of novel emitters for use in OLED applications. Unlike fluorescence, phosphorescence makes use of both singlet and triplet excited states, suggesting the potential for reaching a maximum internal efficiency of 100%. Recently, there has been interest in the use of triplet emitting compounds primarily focusing on trivalent iridium complexes. In this work we report the synthesis of Ir(ppy)3 and its characterization by different techniques like DTA/TGA, FTIR, UV-Visible absorption, PL measurements etc. For making OLED, Ir(ppy)3 is doped in different host materials like TPD etc. The device configuration is ITO/TPD-5% Ir(ppy)3/Alq3/LiF/Al.The EL and I-V characteristics have also been measured.

Proceedings of SPIE - The International Society for Optical Engineering, 2012

The use of optical tweezers for the analysis of aerosols is valuable for understanding the dynami... more The use of optical tweezers for the analysis of aerosols is valuable for understanding the dynamics of atmospherically relevant particles. However to be able to make accurate measurements that can be directly tied to real-world phenomena it is important that we understand the influence of the optical trap on those processes. One process that is seemingly straightforward to study with these techniques is binary droplet coalescence, either using dual beam traps, or by particle collision with a single trapped droplet. This binary coalescence is also of interest in many other processes that make use of dense aerosol sprays such as spray drying and the use of inhalers for drug delivery in conditions such as asthma or hay fever. In this presentation we discuss the use of high speed (~5000 frames per second) video microscopy to track the dynamics of particles as they approach and interact with a trapped aqueous droplet and develop this analysis further by considering elastic light scattering from droplets as they undergo coalescence. We find that we are able to characterize the re-equilibration time of droplets of the same phase after they interact and that the trajectories taken by airborne particles influenced by an optical trap are often quite complex. We also examine the role of parameters such as the salt concentration of the aqueous solutions used and the influence of laser wavelength.

The Journal of Physical Chemistry A, 2013

ISIJ international, 2006

High input power density and shorter on-time during pulsed laser spot welding results in high pea... more High input power density and shorter on-time during pulsed laser spot welding results in high peak temperature, steep heating and cooling cycles, which are difficult to mea-sure experimentally.1–3) A quantitative knowledge of the weld thermal cycle is prerequisite for ...

Quantum Electronics, IEEE …, 2002

Abstract—Experimental observations of the phenomenon of spectral switching are made for a class o... more Abstract—Experimental observations of the phenomenon of spectral switching are made for a class of partially coherent light incident on a circular aperture. The on-axis spectrum of the light in the far-field is different from the spectrum of the light at the aperture. It is shown ...

Optics in the Life Sciences Congress, 2017

Journal of Nanoscience and Nanotechnology, 2010

The reaction of [Ir(ppy)2(micro-Cl)]2 (ppy = 2-pyridiylphenyl) with a substituted bpy ligand (5-b... more The reaction of [Ir(ppy)2(micro-Cl)]2 (ppy = 2-pyridiylphenyl) with a substituted bpy ligand (5-bromo-2,2'-bipyridiyl, 5,5'-dibromo-2,2'-bipyridiyl, 5-ethynyl-2,2'-bipyridiyl) affords [Ir(ppy)2R-(bpy)-R'](CIO4) (R = H, R' = Br (1); R = R, R' = Br (2); R = H, R' = ethynyl (3)) in high yield. The structural, physical, and electrochemical properties of the iridium complexes 1, 2, and 3 were characterized by elemental analysis, NMR and optical spectroscopy, cyclic voltammetry, and X-ray structural analysis.

Optical Trapping …, Jan 1, 2011

Abstract We make use of surface acoustic wave nebulization to introduce airborne particles into o... more Abstract We make use of surface acoustic wave nebulization to introduce airborne particles into optical traps in a robust and repeatable manner. We demonstrate the facile loading of aerosols such as organic liquids and solid particles.

Bulletin of Materials Science, 2004

... Page 6. Suman Anand and ON Srivastava 118 Figure ... sites. Acknowledgements The authors are ... more ... Page 6. Suman Anand and ON Srivastava 118 Figure ... sites. Acknowledgements The authors are grateful to Dr Vikram Kumar, Director, National Physical Laboratory, New Delhi, Prof. AR Verma and Prof. RP Rastogi for encouragement. ...

The rapid growth of Organic Light Emitting devices is of considerable interest due to their poten... more The rapid growth of Organic Light Emitting devices is of considerable interest due to their potential application in flexible, cost-competitive and large screen flat-panel displays. So, there has been much effort put into the development of novel emitters for use in OLED applications. Unlike fluorescence, phosphorescence makes use of both singlet and triplet excited states, suggesting the potential for reaching a maximum internal efficiency of 100%. Recently, there has been interest in the use of triplet emitting compounds primarily focusing on trivalent iridium complexes.

ursiweb.intec.ugent.be

The rapid growth of Organic Light Emitting devices is of considerable interest due to their poten... more The rapid growth of Organic Light Emitting devices is of considerable interest due to their potential application in flexible, cost-competitive and large screen flat-panel displays. So, there has been much effort put into the development of novel emitters for use in OLED applications. Unlike fluorescence, phosphorescence makes use of both singlet and triplet excited states, suggesting the potential for reaching a maximum internal efficiency of 100%. Recently, there has been interest in the use of triplet emitting compounds primarily focusing on trivalent iridium complexes.

MAPAN-Journal of Metrology Society of India

ABSTRACT We have investigated the dispersion properties of photonic crystal waveguide resonators.... more ABSTRACT We have investigated the dispersion properties of photonic crystal waveguide resonators. A passive InGaAsP/InP slab waveguide structure was used for the fabrication of the samples. The PhC waveguide resonators were defined by the omission of several rows of holes along the GammaKappa or GammaMu direction of a triangular photonic crystal lattice. In addition, mirrors with a thickness of 1 to 4 rows of holes were inserted into the waveguide. An optimized dry etch process was used to etch the patterns to a depth of 3.5 µm through the waveguide layer. The group delay of the PhC devices was measured using the phase shift technique. The signal of a tunable laser was modulated at 3 GHz using a LiNbO3 Mach-Zehnder modulator and detected with a high-frequency lightwave receiver. A phase sensitive detection with a network analyer measured the phase shift of the transmitted signal, which is proportional to the group delay. Close to the center of the resonances, the chromatic dispersion reaches values of -250 ps/nm and 250 ps/nm. This corresponds to the chromatic dispersion of 15 km standard fiber.

Laser Resonators, Microresonators, and Beam Control XVI, 2014

Holography, Diffractive Optics, and Applications, 2002

ABSTRACT

Optics Communications, 2006

... [10] S. Anand and HC Kandpal, J. Opt. A: Pure Appl. Opt. 6 (2004), p. 177. Full Text via Cros... more ... [10] S. Anand and HC Kandpal, J. Opt. A: Pure Appl. Opt. 6 (2004), p. 177. Full Text via CrossRef | View Record in Scopus | Cited By in Scopus (12). [11] J. Pu, H. Zhang and S. Nemoto, Opt. ... [14] S. Anand, BK Yadav and HC Kandpal, J. Opt. Soc. Am. A. 19 (2002), p. 2223. ...