Scope and Objectives

The project is to design, fabricate and prototype dielectric coatings for optics applications. The objective is to make coatings for very high reflection (99%), very low reflection (2%), reducing transmitted intensities to protect laser user's eyes by coated goggles, coating on flexible substrate and coating on lenses to reduce reflected light in low-light imaging.

Deliverables

1. Eye-safety goggles capable of blocking better than 99% of incident intensity.
2. High-reflection mirrors of 99.9% reflectivity.
3. Broadband reflection of over 200 nm bandwidth.
4. Anti-reflection (reflection less than 1%) optics.
5. IR lenses coated for optimum performance at 3 different chosen wavelengths.
6. Flexible surfaces with protective IR or visible coatings.

Scientific Output

All the optical components being fabricated in this work are designed in-house. Component fabrication is carried out in our lab and all optical characterizations are also completed in our lab. High-reflection optics for the visible range, with a single band and a bandwidth of 100 nm, is completed. High reflection in normal incidence is not always sufficient. Hence oblique incidence results are also completed for an angular range of 8 to 50 degrees. High-reflection optics is further improved to a broader band (approximately 200 nm bandwidth) by a double-stack arrangement. Highest reflectance achieved till date is 98% when the multilayer stack is coated on silicon substrate; the center wavelength of high reflection and the bandwidth are variable as per the requirement. Anti-reflection optics based on mono-layer, bi-layer and tri-layer coatings on the substrates is fabricated and optically characterized. Optimizations of bi-layer and tri-layer designs are in progress.

Results and outcome till date

Significant experience is gained in coating high-reflection optics and anti-reflection optics on different substrates (glass, quartz, silicon wafer, flexible substrate) for chosen wavelength ranges.

Societal benefit and impact anticipated

A large number of technological applications, ranging from research-grade mirrors to sensors, require coatings with high tolerance values. Eye-protection goggles, used in laser-based combat operations, require high-quality coatings. These are usually imported at very high costs. Developing the competence to make standard coatings for optical components, as well as designing specialty coatings for novel applications, is an essential competence required at the national level.

Next steps

Almost all the optical coatings should be multiply-checked for their characteristics before finalizing their suitability for applications. In addition, all the parameters should be optimized for the best performance.

Publications and reports

Journals
1. Anupa Kumari et al. Coupling to Tamm plasmon polaritons, dependence on structural parameters J.Phys.D Appl.Phys. 51, 255103, 2018.
2. Dipal Rout et al. Interplay of dual photonic stopband in fluorescence enhancement from dye doped photonic crystal heterostructures J. Nanophot. 13, 046005, 2019.

International conferences
1. Photonics 2018 Delhi Dec. 12-15 2018 Single Material Periodic Photonic Structures for Dispersion Compensation by Nitish Kumar Gupta and R. Vijaya (oral).
2. Photonics 2018 Delhi Dec. 12-15 2018 Impact of geometrical parameters on excitation of Tamm plasmon polaritons by Anupa Kumari, Samir Kumar, Govind Kumar, Mukesh K. Shukla, Partha S. Maji, R. Vijaya and Ritwick Das (poster).
3. icONMAT 2019 Kochi Jan 3-5 2019 Tamm Plasmon Coupled Fluorescence Enhancement in One Dimensional Distributed Feedback Cavity by Govind Kumar, Nitish Kumar Gupta and R. Vijaya (Oral).
4. International conference ADMAT 2019 Hyderabad 23-25 Sept 2019 Special purpose Dielectric Optical Coatings by Govind Kumar, Linu George and R.Vijaya (e-poster),

Patents

Nil

Scholars and Project Staff

Ummer K.V: Oct 2017 to April 2018
Ashwani Kumar Rajput: Jan 2018 - July2019
Asha Yadav: May-July 2018
Linu George: June 2018 - ongoing
Sumedha: Sept 2018 - ongoing
Happy Yadav: Sept 2019-ongoing

Challenges faced

Project staff left whenever they got Ph.D admission or a better job; frequent change delayed the progress. The funds in Equipment are insufficient to buy a new ion-based sputtering system that is required for high-quality coatings (as originally proposed in the project proposal). Hence the old system available with the PI has been utilized so far.

Other information

For reproducible and reliable coatings, ion-based coating system is essential.