Research

Laser Physics

Laser is a source of highly coherent light which has a wide range of applications such as communication, LiDAR, sensors, medicine, surgery, and micro-machining. A conventional laser has mainly three components: a gain medium, a feedback system, and a pumping mechanism. To build a laser, optical feedback is essential to confine light inside the gain medium to enhance the amplification process. In our lab, we mainly deal with random lasers and distributed feedback lasers. The former one utilizes the light scattering mediated feedback for light amplification whereas the latter one makes use of grating induced optical feedback. We develop these lasers and study their different properties

Optofluidic random laser

Random Laser

Presence of a large number of randomly distributed scatterers in a system causes multiple scattering of light that can eventually lead to amplify the light. This new kind of laser is known as random laser (RL). RLs have unique characteristics and a wide range of potential applications such as speckle free imaging, super resolution spectroscopy, bio-imaging and optical sensors. We investigate the spatial and temporal dynamics of the random lasing modes, their interactions, decay behavior and intensity fluctuations.

Distributed feedback laser

Instead of using feedback mirrors, periodic grating structure can be used to provide optical feedback by exploiting the photonic band-gap effect and this kind of lasers are known as Distributed feedback (DFB) laser. Stable, ultra-narrow line-width single mode lasing emission can be achieved in a DFB laser by using suitable gain medium. These lasers can further be utilized for intra-cavity optical sensing applications with unprecedented sensitivity.

Imaging through disordered media

Light scattering is detrimental for optical imaging. For strong light scattering, the wavefront is completely scrambled and image forms a random speckle pattern. However, utilizing the optical memory effect, imaging of objects hidden behind a scattering medium possible by speckle-correlations. These family of methods are known as Imaging through disordered media. Here, we employ correlation analysis to determine the dynamical properties of fluorescent objects hidden behind a visually opaque layer.

Optical sensors

In this research domain, our main focus is on development of innovative optofluidic based sensors. Light diffraction and/or interference patterns are utilized to measure different optical properties and physical parameters. These micro-channeled optofluidic devices have the potential for on-chip sensing applications.

Optical waveguide

Optical waveguide is an important component in integrated optics for low loss transmission of optical signal. Glass-ceramic and polymer based waveguides hold great potential in development of low loss waveguides. These waveguides are widely used to develop different optoelectronic devices such as light-emitting diodes (LEDs), semiconductor micro-lasers, flat-panel displays, photovoltaic cells and active waveguides.

Photonic crystals

Periodic variation of electric permittivity in a certain direction prohibits a certain band of photon frequencies to propagate in a certain direction due to the existence of the photonic stop-band (PSB). This kind of optical structure is known as Photonic crystal. Opal is a group of artificially fabricated 3-D photonic crystals which exhibit pseudo PSB. Incorporation of a lasing system within a cavity formed by opal structures play a significant role in development of low threshold lasing devices.

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