Source based primary standard of spectral radiance in the form of a variable temperature blackbody has been established. This blackbody works in the temperature range of 1800K – 3200K with temperature stability of ± 0.2K. Its emissivity is 0.999, and exhibits radiance uniformity within 0.1%, in the wavelength range 0.2 μm-2.5 μm. The uncertainty in spectral radiance measurement using this blackbody is 0.3-0.5% in the wavelength range 0.2 μm-0.4 μm, and 0.1-0.3% in the wavelength range 0.4 μm-2.5 μm, respectively. The established facility is shown in Fig. 1.3.

The Group has also participated in the APMP Sponsored Key Comparison (CCPR K4.x) on luminous flux with lamps as transfer standards. The transfer standards in the form of three Polaron LF 200 W incandescent lamp having identification nos. as P591, P592 and P593 were procured from NPL, UK. Calibration facilities for the photometric parameters were extended to various lamp and lighting industries, R and D institutions etc. Calibration and Measurement facilities in air UV spectral region were maintained and extended to user industries and institutions.

Basic research on optical coherence for its application on encoding and information processing has been pursued further.

DST sponsored project on “Studies on the effect of dynamic multiple scattering on the frequency shift of spectral lines and applications”

Experimental studies were conducted to study the shift of the spectral lines due to dynamic scattering by producing a gaseous medium whose dielectric susceptibility was a function of both space and time. Dopplet-like wavelength shift of the spectral lines emanated from some discharge lamps was observed despite that the source, the scattering medium and the observer were at rest. Results obtained have been published and presented in various forums. The project has been completed successfully and final report has been submitted to DST, New Delhi.

Space Application Sponsored project on “Development of Calibration-Validation (CALVAL) site at Kavaratti Island”

In this particular project a laboratory has been developed at the Kavratti island for spectral radiance and spectral irradiance calibration of hyperspectral radiometers procured by SAC, Ahmedabad for ocean color studies. This is one of the achievements of the project. Fundamental research for determination of the immersion factor at various levels of water and various type of water was also carried.

On-line approach to non-contact IR sensor technique for estimation of sugars and its byproducts

In the present work infrared spectroscopic technique is investigated as a rapid and nondestructive alternative of chemical methods for the determination of organic acids and sugars in fruit juices. It allows the simultaneous quantification of glucose, fructose and sucrose in fruit juices to make carbohydrate analysis in fruit juices more amenable to routine measurements. Furthermore, the main organic acids in fruit juices, citric acid and malic acid have been monitored by this technique. A successful calibration model is developed with one hundred and twenty five synthetic samples that yield good correlation coefficient. The infrared spectroscopy both in mid infrared and near infrared regions allows nondestructive, rapid and accurate analysis of sugars and organic acids in juices and could be applied in quality control of beverages.

Infrared spectroscopic study for tumor diagnosis

Infrared spectra of normal and malignant breast tissues are measured in the 600 cm-1 to 4000 cm-1 region. The measured spectroscopic features which are the spectroscopic fingerprints of the tissues contain the vital information about the malignant and normal tissues. The novelty of this study is that from the spectroscopic data we could differentiate malignant tissue from the normal one. We analyzed Fourier Transform Infrared (FTIR) data on twenty five cases of infiterating ductal carcinoma of breast with different grades of malignancy from patients of different age groups. Infrared spectra demonstrate significant spectral differences between the normal and the cancerous breast tissues. In particular changes in frequency and intensity in the spectra of protein, nucleic acid and glycogen vibrational modes as well as the band intensity ratios for lipid/proteins, protein/ nucleic acids, protein/glycogen are observed. This allows us to make a qualitative and semi quantitative evaluation of the changes in proliferation activity from normal to diseased tissue.

Switching light with light

Theoretical analyses of laser induced nonlinear absorption processes in rhodopsin protein molecules have been performed. The results validate the feasibility of all-optical switching operation ‘Switching light with light’, in these protein molecules in very simple pump-probe geometry. The switching speed has been shown to be enhanced from milliseconds to nanoseconds time scale. The performance of the switch in terms of contrast has also been enhanced by optimizing the concentration of molecules.