arXiv subjects

Parag Deotare

Publications and source records attributed to Parag Deotare.

5 recordsLinked to original sources

arXiv2026

Electrically pumped AlGaN edge-emitting UV-B laser diodes grown by molecular beam epitaxy

Mid and deep ultraviolet (UV) laser diodes remain among the least explored devices in semiconductor optoelectronics, despite their importance for spectroscopy, biochemical sensing, disinfection, and emerging quantum photonics. Here, we demonstrate an electrically pumped AlGaN-based laser diode operating in the UV-B band (280-315 nm). The device is grown by molecular beam epitaxy (MBE) on single-crystal AlN substrate and fabricated in a ridge-waveguide geometry. The laser diode operates at 298.5 nm and exhibits a relatively low threshold current density of 3.4 kA/cm$^2$. Clear nonlinear light-current characteristics and pronounced spectral narrowing with a full-width-at-half-maximum (FWHM) of 0.2 nm are measured above threshold.

physics.optics↗

arXiv2022

Two-dimensional charge order stabilized in clean polytype heterostructures

Compelling evidence suggests distinct correlated electron behavior may exist only in clean 2D materials such as 1T-TaS2. Unfortunately, experiment and theory suggest that extrinsic disorder in free standing 2D layers disrupts correlation-driven quantum behavior. Here we demonstrate a route to realizing fragile 2D quantum states through endotaxial polytype engineering of van der Waals materials. The true isolation of 2D charge density waves (CDWs) between metallic layers stabilizes commensurate long-range order and lifts the coupling between neighboring CDW layers to restore mirror symmetries via interlayer CDW twinning. The twinned-commensurate charge density wave (tC-CDW) reported herein has a single metal--insulator phase transition at ~350 K as measured structurally and electronically. Fast in-situ transmission electron microscopy and scanned nanobeam diffraction map the formation of tC-CDWs. This work introduces endotaxial polytype engineering of van der Waals materials to access latent 2D ground states distinct from conventional 2D fabrication.

cond-mat.mtrl-sci↗

arXiv2012

Optomechanical and Photothermal Interactions in Suspended Photonic Crystal Membranes

We present here an optomechanical system fabricated with novel stress management techniques that allow us to suspend an ultrathin defect-free silicon photonic-crystal membrane above a Silicon-on-Insulator (SOI) substrate with a gap that is tunable to below 200 nm. Our devices are able to generate strong attractive and repulsive optical forces over a large surface area with simple in- and outcoupling and feature the strongest repulsive optomechanical coupling in any geometry to date (gOM/2π ~ -65 GHz/nm). The interplay between the optomechanical and photo-thermal-mechanical dynamics is explored, and the latter is used to achieve cooling and amplification of the mechanical mode, demonstrating that our platform is well-suited for applications in low-power mass, force, and refractive index sensing as well as and optomechanical accelerometry.

physics.optics↗

arXiv2010

Fabrication and characterization of high quality factor silicon nitride nanobeam cavities

Si3N4 is an excellent material for applications of nanophotonics at visible wavelengths due to its wide bandgap and moderately large refractive index (n $\approx$ 2.0). We present the fabrication and characterization of Si3N4 photonic crystal nanobeam cavities for coupling to diamond nanocrystals and Nitrogen-Vacancy centers in a cavity QED system. Confocal micro-photoluminescence analysis of the nanobeam cavities demonstrates quality factors up to Q ~ 55,000, which is limited by the resolution of our spectrometer. We also demonstrate coarse tuning of cavity resonances across the 600-700nm range by lithographically scaling the size of fabricated devices. This is an order of magnitude improvement over previous SiNx cavities at this important wavelength range.

quant-ph↗

arXiv2010

Photonic crystal nanobeam lasers

Photonic crystal lasers operating at room temperature based on high Q/V nanobeam cavities have been demonstrated. We reported a large spontaneous emission factor (~0.97) by fitting the L-L curve with the rate equations.

physics.optics↗