Welcome to the

Liquid Crystal and Biometric

research group

Crystal Liquid Crystal

Liquid

Introduction• Liquid Crystals (LCs) represent a state of matter intermediate between the liquid state and the crystalline state.

• LCs are systems with orientational order and lacking in positional ordering.

• LCs are anisotropic in nature (ideal for its application in optical devices) while retaining its fluidic nature where it

can still flow like a liquid.

Our interest is in thermotropic liquid crystals where the compound makes a transition from crystalline to liquid

crystalline state with increase in temperature. Further heating results in the liquid (isotropic) state at relatively higher

temperatures. We investigate and characterize the compound in its liquid crystalline state where several liquid

crystalline phases also appear with temperature.

Crystal Smectic Isotropic Liquid

Temperature Increasing

Thermotropic LC Phase

Nematic

At the Liquid Crystal and Biometric research group our present work is primarily focused on the following

Characterization of liquid crystalline systemsLC cells are first fabricated, various liquid crystalline phases are then identified via textural observations through

polarizing optical microscopy and characterized by means of dielectric spectroscopy, electro-optic and structural studies.

References: 1. RSC Adv., 2016, 6, 43069–43079; 2. RSC Adv., 2015, 5, 7001–7006

Schematic diagram of the experimental setup Dielectric spectrum of thermotropic bent-core LCs

Observed textures of different LC phases recorded using a polarizing optical microscope (POM)LC texture under external electric field

Liquid Crystal based core waveguides (LCWs)We design and fabricate electrically controllable Liquid Crystal based core wave guides and study their electro-optic

properties.

References: 1. JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 33, NO. 10, MAY 15, 2015 ; 2. JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 34, NO. 13, JULY 1, 2016 ; 3. Optical Materials 49 (2015) 292–296

LCW fabrication processing steps Polarization dependent light propagation in

LCW

Variation in output power with applied voltage

Light propagation inside LCW Experimental setup to characterize LCW Light propagation in periodically segmented

LCW

Study on Liquid Crystal nanocompositesNanoparticles of different materials are unique because of their interesting properties which are different from their

bulk counterparts. It is expected that when these nanoparticles are dispersed in any liquid crystal material to make

liquid crystal nanocomposite, they may share their intrinsic properties with the liquid crystals host. This improves

the various photonic and electro-optical properties of the existing liquid crystals used for various optical devices

and display applications.

The effect of doping on the conductivity of ferroelectric liquid crystal samples (5F6T and 6F6T)

References: 1. Appl. Phys. Lett. 108, 262903 (2016) ; 2. Phase Transitions, 2015, Vol. 88, No. 6, 605-620

Biometric based recognition systemsOur current research interest in this field involves image processing, pattern recognition, Digital holography, and

optical information processing techniques involving biometrics. We aim to develop new biometric based

recognition systems and work towards the realization of the cancellable fingerprint biometric approach using digital

holography. We are also working on the key generation scheme using biometrics for an optical encryption system.

References: 1. J. Opt. 18 (2016) 115701 ; 2. Journal of Modern Optics, 2017 http://dx.doi.org/10.1080/09500340.2017.1287435

Reconstructed amplitude and phase information obtained from fingerprint hologram

Proposed schematics of the biometric key generation

Biometric keys based image

encryption and decryption