arXiv subjects

Hsien-Chi Yeh

Publications and source records attributed to Hsien-Chi Yeh.

12 recordsLinked to original sources

arXiv2025

Comprehensive Investigation of Fundamental Mode Profiles in Monolithic Nonplanar Ring Oscillators

Nonplanar ring oscillators (NPROs) are building blocks for high-performance single-frequency lasers and ring-laser gyroscopes that have profoundly improved the state-of-the-art laser technologies, fundamental research and precision measurements. However, a comprehensive investigation of fundamental mode profiles in monolithic NPROs has been a missing part even though they will affect the performance of the lasers or ring-laser gyroscopes. Here, we present a comprehensive finite-element modeling of the output beam profiles of monolithic NPROs by combining ABCD transmission matrix and generalized Huygens-Fresnel integral. We theoretically investigate the effects of geometric parameters of monolithic NPROs on their output mode profiles. In particular, we focus on the thermal effect inside the monolithic NPRO and calculate the equivalent focal-length of the thermal-lens by using a ray-tracing-method. Furthermore, we experimentally characterize the output laser beam profile, reconstruct the beam profile at the A-facet of the monolithic NPRO, and compare the experimental results with the simulation, thereby validating the accuracy and reliability of our model. The investigation may facilitate monolithic NPRO design and subsequently improve the performances of NPRO lasers and gyroscopes in the future.

physics.optics↗

arXiv2025

Frequency-shifted laser feedback interferometry in non-planar ring oscillators

Laser feedback interferometry (LFI) has a wide range of applications such as displacement, distance and velocity measurements. LFI has been realized in many types of lasers but has never been reported in non-planar ring oscillators (NPRO) to the best of our knowledge. Here, we present a new type of LFI based on an NPRO laser. The intrinsic resistance to optical feedback in NPROs is broken under weak magnetic intensity condition, where stable bidirectional lasing is initiated in the ring cavity. The interference signal, i.e., the beat of the bidirectional lasing is with frequency in the range of a few hundred kilohertz, which is mainly determined by the applied magnetic intensity in NPRO. Frequency shifted LFI is thus constructed in NPRO without using acoustic optic modulators as mostly used in conventional LFI. A theoretical model based on two frequency rate equations and Lang-Kobayashi equation is presented to describe the mechanism of LFI in NPRO. In the end, micro-vibrational measurements are demonstrated to prove the potential application, where vibration-detection amplitude limit is sub-picometer, and the detection frequency range from kilohertz to a few hundred kilohertz is achieved. Benefiting from the characteristics of tiny footprint, ruggedized structure, long lifetime and ultralow-noise of NPRO lasers, NPRO-based LFI may find important applications in industry, scientific research,military and aerospace.

physics.optics↗

arXiv2025

Sub-kHz single-frequency pulsed semiconductor laser based on NPRO injection locking

We report a single-frequency, narrow-linewidth semiconductor pulsed laser based on pump current modulation and optical injection locking technique. A monolithic non-planar ring oscillator laser is employed as the seed source to guarantee the single-frequency narrow-linewidth performance. Simultaneously, pulse operation is achieved by directly modulating the pump current of the semiconductor laser. The single-frequency pulsed laser (SFPL) has achieved a pulse repetition rate of 50 kHz-1 MHz, a pulse duration ranging from 120 ns to a quasi-continuous state, and a peak power of 160 mW. Moreover, the SFPL has reached a pulsed laser linewidth as narrow as 905 Hz, optical spectrum signal-to-noise ratio of better than 65 dB at a center wavelength of 1064.45 nm. Such extremely narrow-linewidth, repetition-rate and pulse-width tunable SFPL has great potential for applications in coherent LIDAR, metrology, remote sensing, and nonlinear frequency conversion.

physics.optics↗

arXiv2025

Temperature-insensitive fused-tapered fiber couplers based on negative thermal expansion material coating

A new method based on negative thermal expansion material coating is proposed to realize temperature insensitive fiber coupler. By coating a layer of modified epoxy resin with a negative thermal expansion coefficient onto the coupling region of fiber coupler, a stable splitting ratio over a wide temperature range can be achieved. A finite-element model for simulating the influence of thermal fluctuations on fused-tapered fiber coupler's splitting ratio is built and verified via experimental test. Furthermore, using this model, the influence of the thickness, length, and thermal expansion coefficient of the coating material on the splitting ratio is studied. Through adjusting the parameters of the coating, the temperature stability of the fiber coupler splitting ratio can be improved by more than one order of magnitude and improved to 1.2*10-5/K. The temperature-insensitive fused-tapered fiber coupler can find important application in optical precision measurement under extreme temperature environment, such as inter-satellite laser interferometry and high-precision fiber gyroscopes.

physics.optics↗

arXiv2025

Progress of the TianQin project

TianQin is a future space-based gravitational wave observatory targeting the frequency window of $10^{-4}$ Hz $\sim 1$ Hz. A large variety of gravitational wave sources are expected in this frequency band, including the merger of massive black hole binaries, the inspiral of extreme/intermediate mass ratio systems, stellar-mass black hole binaries, Galactic compact binaries, and so on. TianQin will consist of three Earth orbiting satellites on nearly identical orbits with orbital radii of about $10^5$ km. The satellites will form a normal triangle constellation whose plane is nearly perpendicular to the ecliptic plane. The TianQin project has been progressing smoothly following the ``0123" technology roadmap. In step ``0", the TianQin laser ranging station has been constructed and it has successfully ranged to all the five retro-reflectors on the Moon. In step ``1", the drag-free control technology has been tested and demonstrated using the TianQin-1 satellite. In step ``2", the inter-satellite laser interferometry technology will be tested using the pair of TianQin-2 satellites. The TianQin-2 mission has been officially approved and the satellites will be launched around 2026. In step ``3", i.e., the TianQin-3 mission, three identical satellites will be launched around 2035 to form the space-based gravitational wave detector, TianQin, and to start gravitational wave detection in space.

gr-qc↗

arXiv2024

Postprocessing of tilt-to-length noise with coefficient drifts in TianQin using a null time-delay interferometry channel

Tilt-to-length (TTL) coupling is expected to be one of the major noise sources in the interferometric phase readouts in TianQin mission. Arising from the angular motion of spacecraft (SC) and the onboard movable optical subassemblies (MOSAs), TTL noise needs to be removed in postprocessing after suppressing the laser phase noise with time-delay interferometry (TDI) technique. In this article, we show that we can estimate the TTL coupling coefficients using the null TDI channel ζ and remove the TTL noise in the commonly used Michelson variables with the estimated coefficients. We introduce the theoretical model of TTL noise in TDI and consider linear drifts in the linear TTL coefficients for noise estimation and subtraction. The TTL coefficients with drifts are estimated successfully with an accuracy of 10 μm/rad in our numerical simulation. We discuss the impact of point-ahead angle compensation error and wavefront error, and find it necessary to estimate linear drift coefficients and quadratic TTL coefficients to keep TTL noise residuals below the 0.3 pm noise reference curve. However, the estimation accuracy suffers greatly from the correlation between yaw jitter measurements that contain the same SC jitter. Assuming all angular jitters induced by MOSAs are independent, choosing a frequency range with relatively higher MOSA yaw jitter noise levels is beneficial to the TTL coefficient estimation.

astro-ph.IM↗

arXiv2021

Analyses of Laser Propagation Noises for TianQin Gravitational Wave Observatory Based on the Global Magnetosphere MHD Simulations

TianQin is a proposed space-borne gravitational wave (GW) observatory composed of three identical satellites orbiting around the geocenter with a radius of $10^5$ km. It aims at detecting GWs in the frequency range of 0.1 mHz -- 1 Hz. The detection of GW relies on the high precision measurement of optical path length at $10^{-12}$~m level. The dispersion of space plasma can lead to the optical path difference (OPD, $Δl$) along the propagation of laser beams between any pair of satellites. Here, we study the OPD noises for TianQin. The Space Weather Modeling Framework is used to simulate the interaction between the Earth magnetosphere and solar wind. From the simulations, we extract the magnetic field and plasma parameters on the orbits of TianQin at four relative positions of the satellite constellation in the Earth magnetosphere. We calculate the OPD noise for single link, Michelson combination, and Time-Delay Interferometry (TDI) combinations ($α$ and $X$). For single link and Michelson interferometer, the maxima of $|Δl|$ are on the order of 1 pm. For the TDI combinations, these can be suppressed to about 0.004 and 0.008 pm for $α$ and $X$. The OPD noise of the Michelson combination is colored in the concerned frequency range; while the ones for the TDI combinations are approximately white. Furthermore, we calculate the ratio of the equivalent strain of the OPD noise to that of TQ, and find that the OPD noises for the TDI combinations can be neglected in the most sensitive frequency range of TQ.

astro-ph.SR↗

arXiv2021

Effects of the space plasma density oscillation on the inter-spacecraft laser ranging for TianQin gravitational wave observatory

The TianQin space Gravitational Waves (GW) observatory will contain 3 geocentric and circularly orbiting spacecraft with an orbital radius of 10^5 km, to detect the GW in the milli-hertz frequency band. Each spacecraft pair will establish a 1.7*10^5 km-long laser interferometer immersed in the solar wind and the magnetospheric plasmas to measure the phase deviations induced by the GW. GW detection requires a high-precision measurement of the laser phase. The cumulative effects of the long distance and the periodic oscillations of the plasma density may induce an additional phase noise. This paper aims to model the plasma induced phase deviation of the inter-spacecraft laser signals, using a realistic orbit simulator and the Space Weather Modeling Framework (SWMF) model. Preliminary results show that the plasma density oscillation can induce the phase deviations close to 2*10^-6 rad/Hz^1/2 or 0.3pm/Hz^1/2 in the milli-hertz frequency band and it is within the error budget assigned to the displacement noise of the interferometry. The amplitude spectrum density of phases along three arms become more separated when the orbital plane is parallel to the Sun-Earth line or during a magnetic storm. Finally, the dependence of the phase deviations on the orbital radius is examined.

physics.space-ph↗

arXiv2020

The TianQin project: current progress on science and technology

TianQin is a planned space-based gravitational wave (GW) observatory consisting of three earth orbiting satellites with an orbital radius of about $10^5~{\rm km}$. The satellites will form a equilateral triangle constellation the plane of which is nearly perpendicular to the ecliptic plane. TianQin aims to detect GWs between $10^{-4}~{\rm Hz}$ and $1~{\rm Hz}$ that can be generated by a wide variety of important astrophysical and cosmological sources, including the inspiral of Galactic ultra-compact binaries, the inspiral of stellar-mass black hole binaries, extreme mass ratio inspirals, the merger of massive black hole binaries, and possibly the energetic processes in the very early universe or exotic sources such as cosmic strings. In order to start science operations around 2035, a roadmap called the 0123 plan is being used to bring the key technologies of TianQin to maturity, supported by the construction of a series of research facilities on the ground. Two major projects of the 0123 plan are being carried out. In this process, the team has created a new generation $17~{\rm cm}$ single-body hollow corner-cube retro-reflector which has been launched with the QueQiao satellite on 21 May 2018; a new laser ranging station equipped with a $1.2~{\rm m}$ telescope has been constructed and the station has successfully ranged to all the five retro-reflectors on the Moon; and the TianQin-1 experimental satellite has been launched on 20 December 2019 and the first round result shows that the satellite has exceeded all of its mission requirements.

gr-qc↗

arXiv2020

The First Round Result from the TianQin-1 Satellite

The TianQin-1 satellite (TQ-1), which is the first technology demonstration satellite for the TianQin project, was launched on 20 December 2019. The first round of experiment had been carried out from 21 December 2019 until 1 April 2020. The residual acceleration of the satellite is found to be about $1\times10^{-10}~{\rm m}/{\rm s}^{2}/{\rm Hz}^{1/2}$ at $0.1~{\rm Hz}\,$ and about $5\times10^{-11}~{\rm m}/{\rm s}^{2}/{\rm Hz}^{1/2}$ at $0.05~{\rm Hz}\,$, measured by an inertial sensor with a sensitivity of $5\times10^{-12}~{\rm m}/{\rm s}^{2}/{\rm Hz}^{1/2}$ at $0.1~{\rm Hz}\,$. The micro-Newton thrusters has demonstrated a thrust resolution of $0.1~μ{\rm N}$ and a thrust noise of $0.3~μ{\rm N}/{\rm Hz}^{1/2}$ at $0.1~{\rm Hz}$. The residual noise of the satellite with drag-free control is $3\times10^{-9}~{\rm m}/{\rm s}^{2}/{\rm Hz}^{1/2}$ at $0.1~{\rm Hz}\,$. The noise level of the optical readout system is about $30~{\rm pm}/{\rm Hz}^{1/2}$ at $0.1~{\rm Hz}\,$. The temperature stability at temperature monitoring position is controlled to be about $\pm3~{\rm mK}$ per orbit, and the mismatch between the center-of-mass of the satellite and that of the test mass is measured with a precision of better than $0.1~{\rm mm}$.

physics.ins-det↗

arXiv2016

Measurable signatures of quantum mechanics in a classical spacetime

We propose an optomechanics experiment that can search for signatures of a fundamentally classical theory of gravity and in particular of the many-body Schroedinger-Newton (SN) equation, which governs the evolution of a crystal under a self-gravitational field. The SN equation predicts that the dynamics of a macroscopic mechanical oscillator's center of mass wavefunction differ from the predictions of standard quantum mechanics. This difference is largest for low-frequency oscillators, and for materials, such as Tungsten or Osmium, with small quantum fluctuations of the constituent atoms around their lattice equilibrium sites. Light probes the motion of these oscillators and is eventually measured in order to extract valuable information on the pendulum's dynamics. Due to the non-linearity contained in the SN equation, we analyze the fluctuations of measurement results differently than standard quantum mechanics. We revisit how to model a thermal bath, and the wavefunction collapse postulate, resulting in two prescriptions for analyzing the quantum measurement of the light. We demonstrate that both predict features, in the outgoing light's phase fluctuations' spectrum, which are separate from classical thermal fluctuations and quantum shot noise, and which can be clearly resolved with state of the art technology.

quant-ph↗

arXiv2015

TianQin: a space-borne gravitational wave detector

TianQin is a proposal for a space-borne detector of gravitational waves in the millihertz frequencies. The experiment relies on a constellation of three drag-free spacecraft orbiting the Earth. Inter-spacecraft laser interferometry is used to monitor the distances between the test masses. The experiment is designed to be capable of detecting a signal with high confidence from a single source of gravitational waves within a few months of observing time. We describe the preliminary mission concept for TianQin, including the candidate source and experimental designs. We present estimates for the major constituents of the experiment's error budget and discuss the project's overall feasibility. Given the current level of technology readiness, we expect TianQin to be flown in the second half of the next decade.

astro-ph.IM↗