arXiv subjects

Mallika Irene Suresh

Publications and source records attributed to Mallika Irene Suresh.

5 recordsLinked to original sources

arXiv2025

Spatial mapping and tuning of terahertz modes in a silicon whispering gallery mode resonator

Identification and subsequent manipulation of resonant modes typically relies on comparison with calculations which require precise knowledge of material parameters and dimensions. For millimetre-sized resonators that support millimetre-wave modes, this is particularly challenging due to the poorly determined physical parameters and additional perturbative effects of nearby dielectric or metallic substrates in experimental setups. Here, we use perturbation from a metal needle to experimentally map the spatial distribution of terahertz modes in a silicon disc resonator. We then use this information to design a patterned structure to manipulate specific modes in the system, a technique that could be useful for targeted tuning of such modes.

physics.optics↗

arXiv2024

Single-point-diamond-turned GaAs disk resonator with over a million optical quality factor

Gallium arsenide optical resonators have been identified as platforms for light-matter interactions ranging from optomechanics to quantum electrodynamics involving nonlinear optics. Here, we present a 5-mm-diameter whispering gallery mode resonator made of undoped gallium arsenide. The fabrication was done using single-point diamond turning followed by polishing with diamond solutions of varying grain size. The resulting resonator was optically characterized to have a quality factor of more than a million.

physics.optics↗

arXiv2023

Gallium arsenide whispering gallery mode resonators for terahertz photonics

As the field of terahertz (THz) photonics advances, we present a monolithic gallium arsenide (GaAs) disk-shaped whispering gallery mode resonator that has potential as a component in THz nonlinear optics. GaAs is a material with significant optical nonlinearity which can be enhanced when the crystal is shaped into a microdisk resonator. A 4-mm-disk-resonator was fabricated using single-point diamond turning and was characterised to obtain a quality (Q) factor of 2.2k at ~150 GHz and 1.4k at ~300 GHz. We also demonstrated the blue-shifting of up to ~0.3 GHz of the THz modes using a block of metal. This post-fabrication degree of freedom could be useful for phase-matching requirements for nonlinear optical processes, such as detection based on optical up-conversion of THz radiation. Such a compact, tunable and efficient device could be integrated into nonlinear photonic platforms for THz generation, manipulation and detection.

physics.optics↗

arXiv2021

Deep-UV-enhanced supercontinuum generated in tapered gas-filled photonic crystal fiber

We present the use of linearly down-tapered gas-filled hollow-core photonic crystal fiber in a single-stage, pumped with pulses from a compact infrared laser source, to generate a supercontinuum carrying significant spectral power in the deep ultraviolet (200 - 300 nm). The generated supercontinuum extends from the near infrared down to around 213 nm with up to 0.83 mW/nm in the deep ultraviolet.

physics.optics↗

arXiv2020

Covariance spectroscopy of molecular gases using fs pulse bursts created by modulational instability in gas-filled hollow-core fiber

We present a technique that uses noisy broadband pulse bursts generated by modulational instability to probe nonlinear processes, including infrared-inactive Raman transitions, in molecular gases. These processes imprint correlations between different regions of the noisy spectrum, which can be detected by acquiring single shot spectra and calculating the Pearson correlation coefficient between the different frequency components. Numerical simulations verify the experimental measurements and are used to further understand the system and discuss methods to improve the signal strength and the spectral resolution of the technique.

physics.optics↗