arXiv subjects

Shivaprasad U. Hulyal

Publications and source records attributed to Shivaprasad U. Hulyal.

3 recordsLinked to original sources

arXiv2026

Terabit-scale wavelength-multiplexed transmitter enabled by thin-film lithium tantalate

Artificial-intelligence systems face a growing data-movement bottleneck and require higher interconnect bandwidth without a proportional increase in electrical power consumption or the number of laser sources and fibre connections. Moving optical interfaces closer to computing chips reduces electrical transmission loss, while demanding optical engines that combine high channel capacity, broadband modulation and simple packaging. Although wavelength multiplexing relieves pressure on the fibre budget, integrating shared multi-wavelength sources with dense wavelength routing and broadband modulation in a compact format remains challenging. Here we demonstrate a monolithic transmitter that brings these functions together on a single material platform, enabled by the low birefringence and native Pockels response of thin-film lithium tantalate. The device separates, independently modulates and recombines eight wavelength channels between one optical input and output. This architecture retains a two-fibre interface as the channel count grows, directly addressing the packaging burden of parallel optical links. Measurements across the eight channels establish an aggregate line rate of 1.6 Tbit s$^{-1}$. Operation with a shared optical frequency comb achieves an estimated net data rate of 0.58 Tbit s$^{-1}$ across four channels, demonstrating compatibility with a common multi-wavelength source. Scaling this architecture into multiple wavelength-multiplexed engines offers a path towards 10 Tbit s$^{-1}$ optical interfaces with high bandwidth per unit package edge, positioning thin-film lithium tantalate for the next generation of co-packaged optical interconnects.

physics.app-ph↗

arXiv2025

Narrow-linewidth, piezoelectrically tunable photonic integrated blue laser

Frequency-agile lasers operating in the ultraviolet-to-blue spectral range (360-480 nm) are critical enablers for a wide range of technologies, including free-space and underwater optical communications, optical atomic clocks, and Rydberg-atom-based quantum computing platforms. Integrated photonic lasers offer a compelling platform for these applications by combining low-noise performance with fast frequency tuning in a compact, robust form factor through monolithic integration. However, realizing such lasers in the blue spectral range remains challenging due to limitations in current semiconductor materials and photonic integration techniques. Here, we report the first demonstration of a photonic integrated blue laser at around 461 nm, which simultaneously achieves frequency agility and low phase noise. This implementation is based on the hybrid integration of a gallium nitride-based laser diode, which is self-injection locked to a high-Q microresonator fabricated on a low-loss silicon nitride photonic platform with 0.4 dB/cm propagation loss. The laser exhibits a sub-30 kHz linewidth and delivers over 1 mW of optical output power. In addition, aluminum nitride piezoelectric actuators are monolithically integrated onto the photonic circuitry to enable high-speed modulation of the refractive index, and thus tuning the laser frequency. This enables mode-hop-free laser linear frequency chirps with excursions up to 900 MHz at repetition rates up to 1 MHz, with tuning nonlinearity below 2%. We showcase the potential applications of this integrated laser in underwater communication and coherent aerosol sensing experiments.

physics.optics↗

arXiv2025

Arrayed waveguide gratings in lithium tantalate integrated photonics

Arrayed Waveguide Gratings (AWGs) are widely used photonic components for splitting and combining different wavelengths of light. They play a key role in wavelength division multiplexing (WDM) systems by enabling efficient routing of multiple data channels over a single optical fiber and as a building block for various optical signal processing, computing, imaging, and spectroscopic applications. Recently, there has been growing interest in integrating AWGs in ferroelectric material platforms, as the platform simultaneously provide efficient electro-optic modulation capability and thus hold the promise for fully integrated WDM transmitters. To date, several demonstrations have been made in the X-cut thin-film lithium niobate ($\mathrm{LiNbO}_3$) platform, yet, the large anisotropy of $\mathrm{LiNbO}_3$ complicates the design and degrades the performance of the AWGs. To address this limitation, we use the recently developed photonic integrated circuits (PICs) based on thin-film lithium tantalate ($\mathrm{LiTaO}_3$), a material with a similar Pockels coefficient as $\mathrm{LiNbO}_3$ but significantly reduced optical anisotropy, as an alternative viable platform. In this work, we manufacture $\mathrm{LiTaO}_3$ AWGs using deep ultraviolet lithography on a wafer-scale. The fabricated AWGs feature a channel spacing of 100 GHz, an insertion loss of < 4 dB and crosstalk of < -14 dB. In addition, we demonstrate a cyclic AWG, as well as a multiplexing and demultiplexing AWG pair for the first time on $\mathrm{LiTaO}_3$ platform. The wafer-scale fabrication of these AWGs not only ensures uniformity and reproducibility, but also paves the way for realizing volume-manufactured integrated WDM transmitters in ferroelectric photonic integrated platforms.

physics.optics↗