arXiv subjects

X. Steve Yao

Publications and source records attributed to X. Steve Yao.

6 recordsLinked to original sources

arXiv2025

Ultra-narrow linewidth light generation based on an optoelectronic oscillator

Narrow-linewidth light sources are essential for both fundamental research and various technological applications, yet they are challenging to generate directly due to instabilities in active laser cavities and the misalignment between closely spaced resonator modes and broad gain bandwidth. In this study, we demonstrate the direct generation of low-noise light from an optoelectronic oscillator (OEO). By minimizing the delay in the optoelectronic link and employing a high-quality optical resonator, an OEO can simultaneously generate both a low-phase-noise optical oscillation that is resilient to phase fluctuations of its pump laser, and a radio frequency (RF) oscillation that captures these fluctuations. We leverage these RF-domain fluctuations to implement a high-performance feedback loop, which stabilizes the pump laser and significantly enhances the performance of optical oscillation. This approach achieves an outstanding phase noise level of -100 dBc/Hz at a 1 kHz offset and an integrated linewidth as narrow as 0.23 Hz. The integration of optoelectronic oscillation and feedback loop provides significant broadband noise suppression compared to conventional schemes for generating narrow-linewidth light, paving the way for developments in fields such as coherent optical communications, atomic spectroscopy, metrology, and quantum optics.

physics.optics↗

arXiv2025

On-chip real-time detection of optical frequency variations with ultrahigh resolution using the sine-cosine encoder approach

Real-time measurement of optical frequency variations (OFVs) is crucial for various applications including laser frequency control, optical computing, and optical sensing. Traditional devices, though accurate, are often too large, slow and costly. Here we present a photonic integrated circuit (PIC) chip, utilizing the sine-cosine encoder principle, for high-speed and high-resolution real-time OFV measurement. Fabricated on a thin film lithium niobate (TFLN) platform, this chip-sized optical frequency detector (OFD) (5.5 mm * 2.7 mm) achieves a speed of up to 2500 THz/s and a resolution as fine as 2 MHz over a range exceeding 160 nm. Our robust algorithm overcomes the device imperfections and ensures precise quantification of OFV parameters. As a practical demonstration, the PIC OFD surpasses existing fiber Bragg grating (FBG) interrogators in sensitivity and speed for strain and vibration measurements. This work opens new avenues for on-chip OFV detection and offers significant potential for diverse applications involving OFV measurement.

physics.optics↗

arXiv2023

Single-frequency lasers' linewidth elegantly characterized with Sigmoid functions of observation time

Linewidth is the most important parameter for characterizing the coherence properties of a single-frequency laser, but unfortunately only the natural linewidth representing the contributions of the spontaneous emission or quantum noise can be described with an analytical expression known as the Schawlow-Townes-Henry formula. To the best of authors' knowledge, no analytical expression is formulized after 63 years since laser's invention for characterizing the effective linewidth of a single-frequency laser including the linewidth broadening caused by the flicker noises, which strongly depends on the measurement duration and is much larger than the natural linewidth. By carefully measuring the instantaneous frequency fluctuations of multiple commercial single-frequency lasers using a self-built optical frequency analyzer with ultra-high resolution and speed to obtain their linewidths with our time domain statistical analysis method, we discover and validate that the laser linewidths can be expressed as one or more Sigmoid functions of observation time. Not only the simple Sigmoid linewidth expression provides clear linewidth information of the laser, but also better understanding of the physical origins affecting the laser linewidths, which will benefit a large number of applications ranging from coherent distributed sensing to gravitational wave detection and therefore is worthy to be widely adopted to fully and elegantly characterize the linewidths of single-frequency lasers.

physics.optics↗

arXiv2021

High Performance Polarization Management Devices Based on Thin-Film Lithium Niobate

High-speed polarization management is highly desirable for many applications, such as remote sensing, telecommunication, and medical diagnosis. However, most of the approaches for polarization management rely on bulky optical components that are slow to respond, cumbersome to use, and sometimes with high drive voltages. Here, we overcome these limitations by harnessing photonic integrated circuits based on thin-film lithium niobate platform. We successfully realize a portfolio of thin-film lithium niobate devices for essential polarization management functionalities, including arbitrary polarization generation, fast polarization measurement, polarization scrambling, and automatic polarization control. The present devices feature ultra-fast control speed, low drive voltages, low optical losses and compact footprints. Using these devices, we achieve high fidelity polarization generation with a polarization extinction ratio up to 41.9 dB, fast polarization scrambling with a scrambling rate up to 65 Mrad/s, and endless polarization control with a tracking speed up to 10 Krad/s, all of which are best results in integrated optics. The demonstrated devices unlock a drastically new level of performance and scales in polarization management devices, leading to a paradigm shift in polarization management.

physics.optics↗

arXiv2021

Wavelength-switchable ultra-narrow linewidth fiber laser enabled by a figure-8 compound-ring-cavity filter and a polarization-managed four-channel filter

We propose and demonstrate a high performance four-wavelength erbium-doped fiber laser (EDFL), enabled by a figure-8 compound-ring-cavity (F8-CRC) filter for single-longitudinal-mode (SLM) selection and a polarization-managed four-channel filter (PM-FCF) for defining four lasing wavelengths. We introduce a novel methodology utilizing signal-flow graph combined with Mason's rule to analyze a CRC filter in general and apply it to obtain the important design parameters for the F8-CRC filter used in this paper. By combining the functions of the F8-CRC filter and the PM-FCF filter assisted by the enhanced polarization hole-burning and polarization dependent loss, we achieve the EDFL with fifteen lasing states, including four single-, six dual-, four tri- and one quad-wavelength lasing operations. In particular, all the four single-wavelength operations are in stable SLM oscillation, typically with a linewidth of <600 Hz, a RIN of <=-154.58 dB/Hz@>=3 MHz and an output power fluctuation of <=+/-3.45%. In addition, all the six dual-wavelength operations have very similar performances, with the performance parameters close to those of the single-wavelength lasing operations. Finally, we achieve the wavelength spacing tuning of the dual-wavelength operations for the photonic generation of tunable microwave signals, and successfully obtain a signal at 23.10 GHz as a demonstration.

physics.optics↗

arXiv2000

Microtorus: a High Finesse Microcavity with Whispering-Gallery Modes

We have demonstrated a 165 micron oblate spheroidal microcavity with free spectral range 383.7 GHz (3.06nm), resonance bandwidth 25 MHz (Q ~ 10^7) at 1550nm, and finesse F > 10^4. The highly oblate spheroidal dielectric microcavity combines very high Q-factor, typical of microspheres, with vastly reduced number of excited whispering-gallery (WG) modes (by two orders of magnitude). The very large free spectral range in the novel microcavity - few hundred instead of few GigaHertz in typical microspheres - is desirable for applications in spectral analysis, narrow-linewidth optical and RF oscillators, and cavity QED.

physics.optics↗