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from powerful modern lasers can safely remove material from a tooth without damaging the surrounding area. Previous attempts to develop this technique have failed because they used longer-lasting laser pulses that heated and cracked healthy parts of the tooth.
(A. Rode et. al., J. Appl. Phys., 92, 2153, 2002
Hollow core photonic crystal fibre raman laser
Laser physicists in the UK have reduced the threshold power needed for stimulated Raman scattering by two orders of magnitude. The Bath University team says that the breakthrough - which exploits a low-loss, hollow-core photonic-crystal fibre filled with hydrogen - marks the beginning of a new era in gas-based nonlinear optics.
(F Benabid et al., 2002 Science, 298, 399)
Electrical pulses break light speed record
Pulses that travel faster than light have been sent over a significant distance for the first time. Alain Hache´ and Louis Poirier of the University of Moncton in Canada transmitted the pulses through a 120-metre cable made from a coaxial 'photonic crystal'. To create their cable, the Canadian researchers joined together five-metre sections of coaxial cable with alternating electrical impedance. They sent electromagnetic pulses with frequencies between 5 and 15 MHz through the cable, and found that the group velocity reached 3 times the speed of light for frequencies in the absorption band. This was remarkable in comparison with many existing information systems that are based on coaxial cables with data speed of just two-thirds the speed of light. The achievement that utilized the back-reflection caused by impedance mismatch raise hopes that data could travel through electronic communications systems at almost the speed of light.
(A Hache´ and L Poirier 2002 Appl. Phys. Lett. 80
518)
A breakthrough in teleportation
When physicists teleported photons for the first time in 1997, they had to destroy the photons to be sure that the teleportation had been successful. Now a team at the University of Vienna has managed to teleport photons without destroying them. Jian-Wei Pan and
colleagues believe that their method could be the next step towards long-distance quantum communication. In a standard teleportation experiment, a laser is directed at a crystal with nonlinear optical properties. Occasionally the photon will be "down-converted" into two lower energy photons, and sometimes these photons will have their polarizations entangled wherein one of them is vertically and the other horizontally polarized. By using a filter to reduce the intensity of the photons that are going to be teleported, the researchers were able to significantly reduce the number of spurious detection events. The Vienna team could be 97% certain that the state had been teleported to a photon without actually having to detect it. Such a high accuracy means that the teleported photons could be used in "quantum repeaters" for long distance communication. The team now hopes to combine these results with a technique known as "entanglement purification" to further develop quantum communication over long distances.
(J -.W Pan et. al. ,Nature, 421 721, 2003).
Laser takes up gene therapy
Scientists in Germany have used a Ti:sapphire laser to transfer DNA into a cell. Femtosecond lasers improve the transfer of DNA into cells and could advance the fields of gene therapy and DNA vaccination, according to Uday Tirlapur and Karsten König of Friedrich Schiller University in Jena.
(U. Tirlapur and K. König, Nature, 418 290)
Power from terahertz beams
Terahertz beams are required in many scientific and technological applications, ranging from the imaging of biological materials to manipulating quantum states in semiconductors. However, existing tera hertz sources have only been able to generate low-power beams. Now, Gwyn Williams and colleagues at the Brookhaven and Lawrence Berkeley National Laboratories in the US have created a beam that is several orders of magnitude more powerful than any other existing source.
(GL Carr et al., 2002 Nature, 420 153)
Crystals for Nonlinear Optics
The significance and relevance of nonlinear optics (NLO) as an integral part of photonics is evident from the fact that nearly all the photonic devices make use of various NLO materials in one-way or the other. In the current research, we focus on developing a variety of organic, inorganic and semi-organic bulk single crystals.
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Two different crystal growth systems, viz., high temperature solution growth (flux growth) and room temperature solution growth have been designed and fabricated for this purpose. Preliminary attempts are being made to develop good quality inorganic single crystals of strontium tetraborate and bismuth triborate by the flux growth technique. Semi organic
crystals grown from aqueous solution, such as the |
recently discovered
L-arginine tetraflouroborate, L-histidine
tetraflouroborate, etc., with improved nonlinearity, SHG efficiency and mechanical stability are also subjects of our investigation.
Nonlinear Optics with Nanoparticles
Recently we have investigated nonlinear absorption in a silver nanosol and observed that they exhibit induced as well as saturable absorption at the same wavelength, near plasmon band, entirely depending on the excitation fluence. Such a behavior is absent in organic systems. Now we are planning to extend the investigation to composite structures of
nanoparticles. organic materials. Such materials, usually called hybrid materials, have potential applications in the design and fabrication of nanodevices, which can revolutionize photonic technology..
Photothermal Studies
Currently we have focused our work on the investigation of nanometal dispersed porous ceramics. The open cell photo acoustic technique has been employed for the evaluation of thermal diffusivity of liquid crystals. The photothermal deflection studies on compound semiconductors has been done by varying the degree of dopants. Investigations carried out on layered structures revealed very interesting properties in the propagation of phonons during their transit through the specimen.
We have been continuing the thermal lens studies of fluorescent materials and recently investigated the effect of silver sol on the Fluorescence Quantum Yield (FQY) of certain xanthene dyes. It has been observed that the presence of silver sol decreases the FQY. This is expected to have an important consequence in enhancing Raman scattering signals, which are often obscured by fluorescence.
Laser Generated Colliding Plasma
| Study of laser produced plasma is an important programme of ISP. Recently plasma group has fabricated a multipurpose plasma chamber to investigate colliding plasma under laser irradiation. Studies on dusty plasma and plasma instabilities are also being undertaken. |
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Fibre Optics Technology
1.
Long Period Fibre Grating:
Recent research work in the area of fibre optic technology is centered on the fabrication of long period fibre gratings and employing them for different sensor applications. The gratings have been fabricated in conventional telecommunication fibres, photosensitive fibres and plastic clad silica fibres by the point-by-point method using the third harmonic radiation (355 nm) from an
Nd:YAG laser . Characterization of these long period gratings was carried out using an optical spectrum analyzer. These gratings were employed for chemical sensing with large dynamic range. Sensors developed using gratings were shown to detect the presence of iron, nitrite etc. contained in water up to the ppb level.
2.
Interferometric Sensors:
Another landmark in sensor research was the development of interferometric sensor to measure force. A very compact and inexpensive sensor was designed and developed for the simultaneous measurement of nitrites and chromium dissolved in water. A notable addition is the development of a sensor for ammonia detection using an indicator dye deposited on an uncladded fibre acting as the sensing element.
3.
Polymer Based Fibre Optics
The global proliferation of optical
fibre-based communication networks has been the enabling factor in the shift from the Electronics Age to the Information (i.e.
Photonics) age.
Though earlier silica glass fibres were extensively used, plastic optical fibres
(POFs) are of great commercial interest now because they can maintain flexibility at thicker fibre sizes making them easier to handle and install in communication systems. Research group of the fibre lab in ISP designed and developed a drawing system to fabricate polymer optical fibres using Polystyrene (PS) and Polymethylmetacrylate
(PMMA). This group is concentrating on the fabrication of some optical components like couplers apart from dye-doped fibres
Laser Chaos
The work currently being pursued analyses the applicability of long wavelength semiconductor lasers for optical communication especially in the secure communication using chaotic optical systems. Chaotic outputs of direct current modulated semiconductor lasers are used for encoding the message by direct amplitude modulation at the output of the transmitter.
The encoding was done successfully in analog and digital messages. The encryption technique involves the achievement of perfect synchronization between the transmitting and receiving systems as well as a proper masking of the signal in the intermediate stages. A proportional - integral feedback function is successfully used for this purpose and the results are very encouraging. The level of security offered by this scheme and the effect of a time delay in the synchronization of the receiver with the transmitter is being investigated.
Computational Neuro science
The momentum gained in the research of fiber
The study of the coordination of the brain regions in normal and epileptic subjects brought forth some interesting results that are expected to be of use to clinicians as well. The establishment of synchronous activity in regions that are far apart during the transient period of an epileptic attack was detected by this method. The complexity of the signals under various conditions involving rest and physical fatigue as well as cognitive and mental task conditions was also carried out. The investigation showed that there exists a difference in the complexity of the EEG signals for women as compared to men. Efforts are also on to devise EEG based brain maps as well as develop these into an online tool for use in diagnosis and treatment of neurological disorders. In addition, the group could establish research collaborations with the Amrita Institute of Medical Sciences, Cochin and the Department of Human Biology, University of Cape Town, South Africa.
In the limelight
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Mrs. Achamma Kurian was awarded Ph.D. under the Faculty of Technology,
CUSAT, for her thesis entitled "Characterization of Photonic Materials using Thermal Lens Technique." She is currently a Senior Lecturer at the Catholicate College,
Pathanamthittta.
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International School of Photonics is to host
PHOTONICS 2004, a biennially held International Conference on
Optoelectronics, Fibre optics and Photonics. The conference is sponsored by
SPIE, The International Society for Optical Engineering. The conference is a forum for interaction and exchange of ideas among participants from research institutions, universities, government organizations and industry. For more information visit
the
conference
home page
Seminar
by Visitors
1.
Prof. R. Pratap
Prof. Emeritus, ISP
Evolution of Thought Function
8th February, 2002.
2.
Dr. V. Kumar
Scientist, Centre for Materials for Electronic Technology, Thrissur.
Synthesis of Nanocrystalline Materials
15th April 2002
3.
Dr. G. D. Sockalingam
University of Reims, France
Biomedical Applications of Vibrational Spectroscopy.
12th November 2002
4.
Dr. C. Murali Krishna
Centre for Laser Spectroscopy, MAHE, Manipal
Laser Spectroscopy for diagnosis and early detection of malignancy
12th November 2002
5.
Prof. Dino Jaroszynski
University of Strathclyde
Intense Laser Interaction with Plasma
13th December 2002.
Accolade
1.
Prof. V P N Nampoori attended the Belgium Photonics Fabrication Europe Conference held during 28th October-1st November 2002 at Brugge. He presented papers on fibre optic sensors by Thomas Lee S and P Suresh Kumar at the Transducing Materials and Devices conference.
2.
Dr. A. Deepthy, DST Young Scientist Fellow at ISP, won the best thesis award at the National Laser Symposium2002, held at Thiruvananthapuram. Her thesis entitled "Growth and Physical Properties of Nonlinear Optical KTP and Ferroelectric GPI single crystals" was done under the supervision of Prof. H.L. Bhat at the Indian Institute of Science, Bangalore.
3. Research Scholars of ISP,
Thomas Lee S and Sajan D. George presented papers at the Photonics Asia-02 along with
P. Suresh Kumar and K. Geetha at the APOC-2002 held at Shanghai, China in October 2002.
Recent publications from ISP
1. Thermal lens spectrum of organic dyes using optical parametric oscillator.
Achamma Kurian, K. P. Unnikrishnan, Sajan D. George, Pramod Gopinath, V.P.N Nampoori & C. P. G. Vallabhan. Spectrochimica Acta part A, 59 , 487-491, 2003.
2. Studies on two-photon absorption of aniline using thermal lens effect.
Achamma Kurian, K P Unnikrishnan, S Thomas Lee, Sajan D. George, V P N Nampoori and C P G Vallabhan.
J. of Nonlinear Optical Physics & Materials.
3. Effect of pH on quantum yield of fluorescein using thermal lens technique.
Achamma Kurian, Nibu A George, Sajan D George, K P Unnikrishnan, Binoy Paul, Pramod Gopinath, V P N Nampoori and C P G Vallabhan,
Journal of Optics, 31 (1), 29-36, 2002.
4. Studies on fluorescence efficiency and photodegeneration of rhodamine 6G doped PMMA using thermal lens technique.
Achamma Kurian, Nibu A George, Binoy Paul, V P N Nampoori and C P G Vallabhan.
Laser Chemistry, 20 (2-4), 99-110, 2002.
5. Realization of optical logic gates using thermal lens technique.
Achamma Kurian, Nibu A George, S. Thomas Lee, K P Unnikrishnan, V P N Nampoori and C P G Vallabhan.
Laser Chemistry, 20 (2-4), 81-87, 2002.
6. Photoacoustic measurement of transport properties in doped GaAs epitaxial layers.
Sajan D George, Dilna. S, P. Radhakrishnan, C. P. G. Vallabhan and V.P.N.Nampoori.
Physica Status Solidi (A), 195 No-2, 416-421, 2003.
7. Effect of Te doping on thermal diffusivity of Bi2Se3 crystals: A study using open cell photoacoustic technique.
Sajan. D. George, Saji Augustine, Elizabeth Mathai, P. Radhakrishnan,V. P. N. Nampoori and C. P. G. Vallabhan.
Physica Status Solidi (A), In press.
8. A photoacoustic study of the effect of doping concentration in the transport properties of GaAs epitaxial layers.
Sajan D George, Dilna. S, Prasanth. R, P. Radhakrishnan, C. P. G. Vallabhan and V. P. N. Nampoori.
Optical Engineering ,42(5), 2003.
9. Photoacoustic Investigation of doped InP using open cell configuration.
Sajan . George, C.P.G.Vallabhan, M. Heck, P.Radhakrishnan and V.P.N.Nampoori.
Nondestructive Evaluation and Testing,18, 75-82, 2002.
10. Design and development of an LED based fiber optic evanescent wave sensor for simultaneous detection of chromium and nitrite traces in water.
P. Suresh Kumar, S. Thomas Lee, C.P.G.Vallabhan, V.P.N. Nampoori and P. Radhakrishnan.
Optics Communications, 214, 25-30, 2002.
11. A Fiber optic evanescent wave sensor used for the detection of trace nitrites in water.
P Sureshkumar, C P G Vallabhan, V P N Nampoori, V N Sivasankara Pillai and P Radhakrishnan.
J. of Optics A-Pure & Appl. Opt., 4, 247-250, 2002.
12. Compact polarization-independent Mach-Zhender space switch combining carrier depletion and the quantum confined stark effect.
R.Prasanth, J.E.M.Haverkort, J.H.Wolter.
IEEE J. of Quantum Electronics Vol: 39 , 2003, 379- 383.
13. Photothermal deflection studies on GaAs epitaxial layers.
George N A, Vallabhan C P G, Nampoori V P N and Radhakrishnan P.
Applied Optics, 41(24), 5179-5184, 2002.
14. Degenerate four wave mixing in some metal phthalocyanines and naphthalocyanines.
K. P. Unnikrishnan, Jayan Thomas, V. P. N. Nampoori and C. P. G. Vallabhan,
Chem. Phys., 279, 209-213, 2002.
15. Third order nonlinear optical studies in europium naphthalocyanine using degenerate four wave mixing and Z-scan.
K. P. Unnikrishnan, Jayan Thomas, V. P. N. Nampoori and C. P. G. Vallabhan,
Optics Communications, 204, 385-390, 2002.
16. Wavelength dependence of nonlinear absorption in a bis-phthalocyanines studied using Z-scan technique.
K P Unnikrishnan, Jayan Thomas, V P N Nampoori and C P G Vallabhan.
Applied Physics B, 75, 871 , 2002.
17. Nonlinear absorption in certain metal phthalocyanines at resonant and near resonant wavelengths.
K P Unnikrishnan, Jayan Thomas, V P N Nampoori and
C P G Vallabhan
Optics Communication (In press)
18. Microbent Optical Fibers as Evanescent Wave Sensors .
S Thomas Lee, K. Geetha, V P N Nampoori, C P G Vallabhan and P Radhakrishnan
Optical Engg., 41, 3260-3264, 2002.
19. A microbent fiber optic pH sensor.
S. Thomas Lee, B. Aneeshkumar, P. Radhakrishnan,
C. P. G. Vallabhan and V. P. N. Nampoori
Optics Communications, 205, 253 - 256 , 2002.
20. Photoacoustic studies on n-type InP.
Nibu A. George, C. P. G. Vallabhan, V. P. N. Nampoori, and P. Radhakrishnan,
Optical Engineering, 41(1), 251-254, ,2002.
21. Optical properties of porphyrins in borate glassy matrix.
Kumar, G. A.; Thomas, Vinoy; Jose, Gin; Unnikrishnan, N. V.; Nampoori, V. P. N.,
Materials Chemistry and Physics , 73(2-3), 206-211, 2002.
22. Chaotic encryption using long wavelength directly modulated semiconductor lasers.
V. Bindu, V M Nandakumaran.
J. Optics A- Pure & Appl. Optics, 4 , 115, 2002.
23. Coordination in the Dynamics of the Brain as Inferred from EEG Analysis.
Pravitha Ramanand and V.P.N. Nampoori
Intl. Journal of Neuroscience, 112, 10, 1245 - 1262, 2002.
And
the last word...
When
you know a thing, to hold that you know it; and when you do
not know a thing, to allow that you do not know it; this is
knowledge
-Confucius
The
only thing I know is that I do not know anything
-Socrates
Editor: Dr. V P N Nampoori
Creative Team: Rekha Mathew, Pravitha Ramanand
Online version: B.Aneesh
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