arXiv subjects

Tao Chu

Publications and source records attributed to Tao Chu.

23 records · Page 2Linked to original sources

arXiv2023

A general designing approach for polarization-independent photonic on-chip systems

Due to that the polarization states in optical fibers change randomly during transmission, polarization-independent (PID) devices are demanded to receive lights with arbitrary polarization states. Compared with their orthogonal polarization states, the optical profiles of various modes of the same polarization are similar, and their directions of the main electric field are same. Therefore, it's much easier to design PID devices using multi-modes of one polarization state instead of orthogonal polarizations. This paper firstly presents a scalable method to achieve PID devices and systems by transforming the light orthogonal polarization states into one polarization with different modes. Taking thermo-optical switches as an example, the PDL of the fabricated 2 x 2 switch cell was about 0.8 dB at 1300-1360 nm, and its extinction ratio (ER) was larger than 19 dB for both polarizations. A 4 x 4 switch was also demonstrated and its function of dual polarization switching was implemented, whose ER was larger than 11 dB for both polarizations. This method has potential in constructing PID on-chip systems for optical communications, optical interconnections, etc.

physics.optics↗

arXiv2023

V3Det: Vast Vocabulary Visual Detection Dataset

Recent advances in detecting arbitrary objects in the real world are trained and evaluated on object detection datasets with a relatively restricted vocabulary. To facilitate the development of more general visual object detection, we propose V3Det, a vast vocabulary visual detection dataset with precisely annotated bounding boxes on massive images. V3Det has several appealing properties: 1) Vast Vocabulary: It contains bounding boxes of objects from 13,204 categories on real-world images, which is 10 times larger than the existing large vocabulary object detection dataset, e.g., LVIS. 2) Hierarchical Category Organization: The vast vocabulary of V3Det is organized by a hierarchical category tree which annotates the inclusion relationship among categories, encouraging the exploration of category relationships in vast and open vocabulary object detection. 3) Rich Annotations: V3Det comprises precisely annotated objects in 243k images and professional descriptions of each category written by human experts and a powerful chatbot. By offering a vast exploration space, V3Det enables extensive benchmarks on both vast and open vocabulary object detection, leading to new observations, practices, and insights for future research. It has the potential to serve as a cornerstone dataset for developing more general visual perception systems. V3Det is available at https://v3det.openxlab.org.cn/.

cs.CV↗

arXiv2023

High-efficiency electro-optic modulator on thin-film lithium niobate with high-permittivity cladding

Thin-film lithium niobate is a promising platform owing to its large electro-optic coefficients and low propagation loss. However, the large footprints of devices limit their application in large-scale integrated optical systems. A crucial challenge is how to maintain the performance advantage given the design space restrictions in this situation. This article proposes and demonstrates a high-efficiency lithium niobate electro-optic (EO) modulator with high-permittivity cladding to improve the electric field strength in waveguides and its overlap with optical fields while maintaining low optical loss and broad bandwidth. The proposed modulator exhibits considerable improvement, featuring a low half-wave voltage-length product of 1.41 Vcm, a low excess loss of 0.5 dB, and a broad 3 dB EO bandwidth of more than 40 GHz. This modulation efficiency is the highest reported for a broadband lithium niobate modulator so far. The design scheme of using high-permittivity cladding may provide a promising solution for improving the integration of photonic devices on the thin-film lithium niobate platform and these devices may serve as fundamental components in large-scale photonic integrated circuits in the future.

physics.optics↗

arXiv2022

Polarization-Independent Wavelength Demultiplexer Based on Single Etched Diffraction Grating Device

Polarization-compatible receivers are indispensable in transceivers used for wavelength division multiplexing (WDM) optical communications, as light polarization is unpredictable after transmission through network fibers. However, the strong waveguide birefringence makes it difficult to realize a polarization-independent wavelength demultiplexer in a silicon photonic (SiPh) receiver. Here, we utilized the birefringence effect for simultaneously demultiplexing wavelengths and polarizations, and experimentally demonstrated a novel polarization-independent wavelength demultiplexer with a single device on a SiPh platform. The principle was validated on an etched diffraction grating (EDG), which successfully split the arbitrarily polarized light containing four wavelengths into eight channels with single-polarization and single-wavelength signals. Polarization-dependent losses of 0.5-1.8 dB, minimum insertion loss of 0.5 dB, and crosstalks lower than -30 dB were experimentally measured. Thus, a promising general solution was developed for implementing polarization-independent WDM receivers and other polarization-independent devices on SiPh and other platforms with birefringent waveguide devices.

physics.optics↗

arXiv2021

18.8 Gbps real-time quantum random number generator with a photonic integrated chip

Quantum random number generators (QRNGs) can produce true random numbers. Yet, the two most important QRNG parameters highly desired for practical applications, i.e., speed and size, have to be compromised during implementations. Here, we present the fastest and miniaturized QRNG with a record real-time output rate as high as 18.8 Gbps by combining a photonic integrated chip and the technology of optimized randomness extraction. We assemble the photonic integrated circuit designed for vacuum state QRNG implementation, InGaAs homodyne detector and high-bandwidth transimpedance amplifier into a single chip using hybrid packaging, which exhibits the excellent characteristics of integration and high-frequency response. With a sample rate of 2.5 GSa/s in a 10-bit analog-to-digital converter and subsequent paralleled postprocessing in a field programmable gate array, the QRNG outputs ultrafast random bitstreams via a fiber optic transceiver, whose real-time speed is validated in a personal computer.

quant-ph↗