Parmeshwar receives DCMP Graduate Student Travel Award!


Parmeshwar Prasad is selected for DCMP Graduate Student Travel Award APS 2019 March APS Meeting in Boston.

The DCMP Graduate Student Travel Awards were established to assist the professional development and careers of graduate student researchers and are presented through the APS Division of Condensed Matter Physics (DCMP).


Carbon-nanotube-on-waveguide thermo-optic tuners

Thermal tuning is an easily implementable, low-cost method often employed in electronic and mechanical devices to extract optimal performance or to match the operating points of multiple devices. Similarly, in photonic integrated circuits (PICs), thermal tuners are essential for matching the operating wavelengths of multiple photonic devices such as resonators, gratings, and filters. They are also used for low frequency optical modulation and optical memory applications. The working principle is thermally induced change in refractive index of the materials interacting with guided light.

Conventional thermo-optic tuners are implemented using metal heaters. However, metals absorb near-IR wavelengths, where most of the applications of PICs are, and thus have to be placed a few microns away from the devices to be tuned to avoid degradation in performance of the optical devices. The heating, therefore, is not localized and leads to thermal cross-talk among multiple optical devices. This prevents dense integration of integrated optics. Moreover, these heaters have low power efficiency and a large thermal transient. It is desirable to have a heater closer to the device, yet have it be non-absorbing.

Continue reading “Carbon-nanotube-on-waveguide thermo-optic tuners”

Chandan’s work on tuning of nonlinearities now in APL

Chandan and Nishta’s work on tuning of nonlinearities using electrostatic gate voltage has now been accepted in Applied Physics Letters.

The work demonstrates the ability to control and manipulate the nonlinearities in ultra-thin resonators. This control over the nonlinearities is used to cancel out the strongest two nonlinearities in the device. This can not only be used to improve the linear dynamic range for NEMS based sensors but can also be used to probe higher order nonlinearities that are typically masked by the quadratic and cubic nonlinearities.

In this work, we observe higher order stiffening nonlinearities as well as some hints of nonlinear damping. Previous reports of nonlinear damping in 2D materials required cooling down to sub 100mK temperatures and quality factor of close to a million. The fact that we are able to see these weak effects at room temperature with modest quality factors of about 100demonstrates the usefulness of results shown in this manuscript.

More in this paper.

Aneesh’s paper in Optics letter is Editor’s pick!

Aneesh’s recent work in Optics Letter has been highlighted as Editor’s pick.

Article presented an on-chip optical transduction scheme to detect the strain and displacement of graphene based nanoeletromechanical system. The scheme, if implemented using ring loaded Mach-Zehnder interferometer with modest optical quality factors of about 2500, should be able to achieve displacement sensitivity of about 30fm/rtHz  and strain sensitivity of 6×10^-6 % .

He is currently working on implementing the scheme.

See the paper here