arXiv subjects

Xinlin Chen

Publications and source records attributed to Xinlin Chen.

4 recordsLinked to original sources

arXiv2025

Controllable Bistability in Dual-Fiber Optical Trap in Air

The dual-fiber optical trap, owing to its high sensitivity and facile miniaturization, holds significant actual application value in fields such as high-precision metrology of mechanical quantities and biological manipulation. The positional stability of the trapped particle is pivotal to system performance, directly setting the measurement noise floor and operational precision. In this work, we observe bistability and hysteresis in the axial equilibrium position of a 10-um diameter SiO2 microsphere. This bistability arises from optical interference between the fiber ends and the microsphere, creating multiple potential wells. Experimental results demonstrate that the microsphere's transition rate can be effectively modulated through precise control of the trapping laser power. Furthermore, the incorporation of transverse misalignment has effectively eradicated bistability, thereby substantially improving positional stability throughout the entire optical trapping region. This suppression successfully reduced the system's residual positional uncertainty to the thermal noise limit. Consequently, this research will enhance the precision of microparticle manipulation and the sensitivity of sensing in dual-fiber optical trap systems.

physics.optics↗

arXiv2025

Computational TIRF enables optical sectioning beyond the evanescent field for widefield fluorescence microscopy

The resolving ability of widefield fluorescence microscopy is fundamentally limited by out-of-focus background owing to its low axial resolution, particularly for densely labeled biological samples. Although total internal reflection fluorescence (TIRF) microscopy provides strong near-surface sectioning, they are intrinsically restricted to shallow imaging depths. Here we present computational TIRF (cTIRF), a deep learning-based imaging modality that generates TIRF-like sectioned images directly from conventional widefield epifluorescence measurements without any optical modification. By integrating a physics-informed forward model into network training, cTIRF achieves effective background suppression and axial resolution enhancement while maintaining consistency with the measured widefield data. We demonstrate that cTIRF recovers near-surface structures with performance comparable to experimental TIRF, and further enables both single-frame and volumetric sectioned reconstruction in densely labeled samples where conventional TIRF fails. This work establishes cTIRF as a practical and deployable alternative to hardware-based optical sectioning in fluorescence microscopy, enabled by rapid adaptation to new imaging systems with minimal calibration data.

physics.optics↗

arXiv2024

Giant enhancement of higher-order harmonics of an optical-tweezer phonon laser

Phonon lasers, as mechanical analogues of optical lasers, are unique tools for not only fundamental studies of phononics but also diverse applications such as acoustic imaging and force sensing. Very recently, by levitating a micro-size sphere in an optical tweezer, higher-order mechanical harmonics were observed in the phonon-lasing regime, as the first step towards nonlinear levitated optomechanics [Nat. Phys. 19, 414 (2023)]. However, both the lasing strengths and the quality factors of the observed harmonics are typically very low, thus severely hindering their applications. Here we show that, by applying a simple but powerful electronic control to such a levitated micro-sphere, three orders of magnitude enhancement are achievable in the brightness of the phonon lasers, including both the fundamental mode and all its higher-order harmonics. Also, giant improvements of their linewidth and frequency stability are realized in such an electro-optomechanical system, together with further improved higher-order phonon coherence. These results, as a significant step forward for enhancing and controlling micro-object phonon lasers, can be readily used for a wide range of applications involving nonlinear phonon lasers, such as acoustic frequency comb, ultra-sound sensing, atmospherical monitoring, and even bio-medical diagnosis of levitated micro-size objects.

physics.optics↗

arXiv2021

Dual-beam intracavity optical trap with all-optical independent axial and radial self-feedback schemes

Recently single-beam intracavity optical tweezers have been reported and achieved orders-of-magnitude higher confinement than standard optical tweezers. However, there is only one feedback loop between the trapped particle's three-dimensional position and the scattering loss of the intracavity laser. That leads to the coupling effect between the particle's radial and axial motion, and aggravates the axial confinement efficiency. Here, we present and demonstrate the dual-beam intracavity optical trap enabling independent radial and axial self-feedback control of the trapped particle, through offsetting the foci of the clockwise and counter-clockwise beams. We have achieved the axial confinement efficiency of 1.6*10^(-4) mW^(-1) experimentally at very low numerical aperture (NA=0.25), which is the highest axial confinement efficiency of the optical trap to date, to the best of our knowledge. The dual-beam intracavity optical trap will significantly expand the range of applications in the further studies of biology and physics, especially for a sample that is extremely sensitive to heat.

physics.optics↗