The conventional pedagogical techniques in Indian schools are predominantly limited to coursework and involve just necessary laboratory work. It lacks in inculcating the aptitude for practical applications relevant to the coursework amongst the students. This results in a major setback for the students as their mental approach remains constrained to books, where on the contrary, the future depends only on technologies and applications. Considering this, under Optics Outreach Education Program 2014, University of Delhi at Acharya Narendra Dev College SPIE Student Chapter conducted workshops in 22 schools of Delhi including various Government schools as well. The workshop zeroed into the concepts of optics and various innovative techniques developed by our Student chapter members to embark a new method of teaching.
As part of the course curriculum of Physics of class XII, students do a comprehensive theoretical study about the wave nature of light specially related to interference, diffraction and polarisation. But, these studies are not backed up by any experiments. This makes the understanding of these complex topics very difficult. The purpose of the present outreach activity is to make students do many hands-on experiments on the above topics. The experiments have been designed keeping in mind the various theoretical concepts taught to the students. The studies are helpful in making the students understand fringe formation, intensity variation across the fringes formed helping them compare interference and diffraction fringes, dependence of fringe separation on various parameters, linear polarization, Malus‟ law and Brewster‟s law. The tools used to perform the experiments include He-Ne/ diode laser(s), Laptop/Digital Storage Oscilloscope, CCD, various optical components like set of polarisers and analysers, glass plate and hardware components like single slit and double slit. The class XII students are divided into batches and each batch is handled by a team of three University of Delhi at ANDC SPIE student chapter members. The gains of the activity are measured through pre and post-tests.
India has a population of more than 770 million mobile subscribers with number increasing at a swift rate. Most of the
service providers have shifted to optical technologies based on fiber optics. Though, we have subscribers to various
telecom services starting from the school level but they have little idea about the fiber optic technology used. The
present development is an attempt to design a “Low cost optical fiber kit” which will explain the basics in a simpler and
uncomplicated way. Some of the experiments which are planned to be developed and demonstrated include that on
determination of numerical aperture, bending loss, fiber to fiber alignment losses, wavelength division multiplexing,
process of optical communication etc. These kits have been developed under University of Delhi at ANDC SPIE student
chapter’s optics outreach program. The kits will be demonstrated by the chapter student members at various schools in
Delhi and distributed free.
Students are less enthused in performing various spectrometry experiments in a conventional optics laboratory at the
undergraduate level. In order to motivate students towards spectrometry, the present development focuses on innovating
spectrometry experiments in undergraduate optics laboratory by integrating a linear CCD (Charge Coupled Device) for
optical intensity capture using LabVIEW based application and a Digital Storage Oscilloscope with NI LabVIEW Signal
Express. In the first step, students have calibrated wavelength in terms of x- position using a standard Mercury light
source. Then this calibration has been used to display and measure the emission spectra of various light sources. Various
measurements performed include characterizing various LEDs in terms of wavelengths emitted for use in measurement
of Planck's constant, measuring characteristic wavelengths in emission spectra of hydrogen lamp (for calculating
Students at the school level from grade 7 to 12 are taught various concepts of geometrical optics but with little hands-on
activities. Light propagation through different media, image formation using lenses and mirrors under different
conditions and application of basic principles to characterization of lenses, mirrors and other instruments has been a
subject which although fascinates students but due to lack of suitable demonstrating setups, students find difficulty in
understanding these concepts and hence unable to appreciate the importance of such concepts in various useful scientific
apparatus, day to day life, instruments and devices. Therefore, students tend to cram various concepts related to
geometrical optics instead of understanding them. As part of the extension activity in the University Grants Commission
major research project "Investigating science hands-on to promote innovation and research at undergraduate level" and
University of Delhi at Acharya Narendra Dev College SPIE student chapter, students working under this optics outreach
programme have demonstrated various experiments on geometrical optics using a five beam laser ray box and various
optical components like different types of mirrors, lenses, prisms, optical fibers etc. The various hands-on activities
includes demonstrations on laws of reflection, image formation using plane, concave and convex mirrors, mirror
formula, total internal reflection, light propagation in an optical fiber, laws of refraction, image formation using concave
and convex lenses and combination of these lenses, lens formula, light propagation through prisms, dispersion in prism,
defects in eye- Myopia and hypermetropia. Subjects have been evaluated through pre and post tests in order to measure
the improvement in their level of understanding.
We have investigated laser ablation in InSb in the fluence regime of 8.5 J/cm2 to 21 J/cm2 by studying the
crater morphology. Crater morphology shows a non linear change in depth, volume and roughness at fluence of 14.5
J/cm2 (Fcr) and above. These non linear variations with presence of several micro-cavities at the crater bottom (potential
bubble nucleation sites) suggest a different material removal mechanism at Fcr and above. The results have been
explained in light of various ablation theories which support explosive boiling as a possible mass removal mechanism at
Fcr and above. Thermal melting model for laser ablated InSb is in good agreement with the experimental results.
Present studies report step by step analysis, theoretical as well as experimental along with
simulations, of evaluating the output Jones matrix for different experimental configurations consisting
of combination of polarizers and waveplates at different orientations using Jones calculus. This
development is an attempt to ease the polarization studies using Jones calculus through sensors, data
acquisition and analysis tools. The studies provide an extensive laboratory exercise through hands-on
as well as computer simulations to the undergraduate students to comprehend various concepts related
We report here the development of an automated modern optics laboratory for undergraduate students. This developed modern optics laboratory have automated experiments on optoelectronic device characterisation, optical instrumentation, CCD based optical experiments and advanced applications in optics. In the device characterisation section, Voltage-Current (V-I) and Optical Power-Current (P-I) characteristics of various optoelectronic devices like LEDs, Laser diodes and photo diodes have been automated. In the optical instrumentation section, development of PC based optical power meter have been reported whose functionality can be tailored as per the need of the designed experiment. In the CCD based optical experiments section, CCD has been integrated for fringe capture and analysis by studying the diffraction pattern of a pinhole. In the advanced applications in optics section, molar absorbivity of NiSO4 has been calculated. Further work is in progress to develop heart rate monitoring system, non-evasive jaundice studies from the skin, CCD based real time spectrometers as well as elaborate studies on interference, diffraction and polarisation. The automation of this laboratory has been done by integrating various sensors (photodetectors, CCDs, Current and others) with data acquisition cards connected to PC and one of the most widely used world wide scientific graphical programming software LabVIEW. The purpose of the laboratory is to invoke student interest by exposing them to various modern tools in comparison to very conventional as well as boring existing optics laboratories. The use of this scientific graphical programming software will help in performing various real time measurements and calculations with ease. The automation of the experiments will also save great amount of experimentation time and procurement of costly equipments dedicated to each experiment thus providing an efficient way to carry out studies with reduced financial constraints and better manoeuvrability.
The entrance and exit surface damage has been observed in newly developed Neodymium doped phosphate laser glasses viz. Potassium Barium Aluminium Phosphate (KBAP), Lanthanum Potassium Barium Aluminium Phosphate (LKBAP), Yttrium Aluminium Phosphate (YAP) under Q switched Nd:YAG laser irradiation at 1.06 μm wavelength near normal incidence. The YAP glass is suitable for low repetition rate system such as range finders while KBAP and LKBAP find applications for high repetition rate systems which are used in material processing and electro-optic counter measures. The difference between the entrance and exit surface damage thresholds has been explained using electromagnetic effects. The comparison of the morphological features of the KBAP and LKBAP suggest the role of metallic inclusion in the samples whereas in the case of YAP sample, the damage is governed by the intrinsic physical properties of this glass.
Evolution of laser damage morphology has been studied in 112 oriented, mirror polished Indium Antimonide(InSb)samples as a function of increasing energy, pulse repetition rate and number of pulses using a Nd:Cr:GSGG laser of 1.06 μm wavelength having a pulse width of 20ns. Scanning Electron Microscope (SEM) investigations of the irradiated samples have been done to understand the evolution of damage morphology. Damage morphology is consistent with surface melting and solidification along with an evidence of subsurface overheating. Temperature profiles calculated at different fluence levels confirm substantial subsurface heating. Multiple pulse damage seen at 20Hz with increasing fluence levels is mainly thermal damage. Thermal modeling has been done to explain different morphological features.
Evolution of damage in mirror polished samples of HgCdTe, CdTe & CdZnTe has been studied for three fluence regimes-Damage Threshold (Fth), Five Times Damage Threshold (5Fth), Ten Times Damage Threshold (10Fth) with multiple pulses of a Q-switched 1.06 μm Nd:YAG laser of 20ns pulse duration. Damage morphology observed under Scanning Electron Microscope (SEM) seem to evolve almost in similar fashion with increasing number of pulses as well as incident energy in HgCdTe and CdZnTe on account of uniform heating through a significant depth through the sample surface whereas in case of CdTe, effect of subsurface superheating is evident. Thermal modeling has been done to explain the evolution of laser damage.