Optics express最新文献

This paper proposes a diffusion-model-based method for addressing inverse problems in optical sound-field imaging. Optical sound-field imaging, known for its high spatial resolution, measures sound by detecting small variations in the refractive index of air caused by sound but often suffers from unavoidable noise contamination. Therefore, we present a diffusion model-based approach for sound-field inverse problems, including denoising, noisy sound-field reconstruction and extrapolation. During inference, sound-field degradation is introduced into the inverse denoising process, with range-null space decomposition used as a solver to handle degradation, iteratively generating degraded sound-field information. Numerical experiments show that our method outperforms other deep-learning-based methods in denoising and reconstruction tasks, and obtains effective results in extrapolation task. The experimental results demonstrate the applicability of our model to the real world.

We present an ultrathin microbubble Fabry-Perot interferometer (FPI) sensor designed for low-pressure and low-temperature sensing applications. The preparation of the ultrathin microbubbles was achieved through an improved arc discharge technique. Consequently, a pressure sensitivity of 63 pm/kPa and a temperature sensitivity of 220 pm/°C at room temperature (20°C) and low air pressure (110-200 kPa) were attained, a performance that is highly commendable for a sensor of its kind. Furthermore, the use of a Bragg grating was employed to eliminate the effect of temperature on pressure, thereby enhancing the accuracy of the measured pressure. Experimental findings indicate that this ultrathin microbubble FPI sensor exhibits ultra-high sensitivity to pressure and temperature at low temperatures and pressures, offering what we believe to be a novel solution for the measurement of low temperatures and low-pressure environments.

In this paper, a dual-resonances mid-infrared all-dielectric metasurface sensor based on asymmetric cross dimer, which is driven by quasi-bound states in the continuum (QBIC), is proposed and investigated. The metasurface sensor maintains the total permittivity constant when the asymmetric parameter is adjusted, thereby ensuring the stability of the QBIC resonance wavelengths, which exhibit Q-factors of 6351 and 13561, respectively. The multiple decompositions and electromagnetic field distributions reveal that the toroidal dipole is the dominant component of the dual-resonance modes. The sensitivities to the refractive index are 3559 nm/RIU and 1146 nm/RIU, with corresponding figures of merit of 4449 RIU^-1 and 2453 RIU^-1, respectively. Further numerical simulations have demonstrated a strong coupling phenomenon between the QBIC and the molecular vibrations of polymethyl methacrylate (PMMA), resulting in a significant enhancement of the infrared absorption signal. With the 50-nm-thick PMMA layer, the enhancement of molecular signal is 90.614%.

This study presents a high-power, single-longitudinal-mode (SLM) fiber oscillator with a ring cavity design, operating at 1064 nm. Utilizing a double-cladding ytterbium-doped fiber as the gain medium, the system incorporates a fiber Bragg grating Fabry-Perot cavity and a dual coupler ring for step-by-step filtering to achieve SLM operation. With a pump power of 4.19 W, the oscillator delivered an output power of 1.01 W and narrowed the linewidth to 147 Hz, with the potential for further power increase. The oscillator demonstrated excellent longitudinal-mode stability, maintaining mode-hop-free operation for 8.7 hours after temperature stabilization. To the best of our knowledge, this work represents the longest duration of mode-hop-free operation and the narrowest laser linewidth achieved by a free-running ring-cavity SLM fiber oscillator at watt-level output powers.

Short-reach optical networks, the backbone of data centers, face a significant challenge: transmitting high data rates at low cost and low energy consumption. While coherent signals can carry high data rates, coherent receivers are expensive and complex. Also, to equalize channel dispersion, they rely on digital signal processing modules, which consume large amounts of power and introduce more latency. Photonic reservoirs emerged as a way to process these signals in the analog optical domain, alleviating the power consumption and latency issues in state-of-the-art receivers. In this work, we show in simulations that a photonic reservoir combined with a self-coherent photonic receiver achieves a BER of 3.8 × 10^-3 for a 32 Gbaud 16-QAM signal and an 80 km link, requiring a low CSPR of 3 dB compared to state-of-the-art self-coherent receivers.

Currently, research on optical tweezers technology predominantly focuses on single-trap optical tweezers, which have a limited controllable range. Multi-trap optical tweezers effectively address these limitations. This paper proposes a method for developing a dual-trap optical tweezers system utilizing basic optical elements. Two optical traps are created by reflecting a laser beam off the front and rear surfaces of a beam splitter. The transition between single-trap and dual-trap configurations is facilitated by a lens group, which allows for the adjustment of the distance between the two traps. Furthermore, by incorporating a rotatable optical wedge into the optical path, the optical trap can be rotated along an annular orbit of any radius. This study includes simulations and analyses of the effects of lens spacing, refractive index, and tilt angle on the rotational range of optical traps. An optical trapping experimental system was constructed, and its feasibility was demonstrated using polystyrene particles as the target objects.

Spatial transformations of light are ubiquitous in optics, with examples ranging from simple imaging with a lens to quantum and classical information processing in waveguide meshes. Multi-plane light converter (MPLC) systems have emerged as a platform that promises completely general spatial transformations, i.e., a universal unitary. However, until now, MPLC systems have demonstrated transformations that are far from general, e.g., converting from a Gaussian to Laguerre-Gauss mode. Here, we demonstrate the promise of an MLPC, the ability to impose an arbitrary unitary transformation that can be reconfigured dynamically. Specifically, we consider transformations on superpositions of parallel free-space beams arranged in an array, which is a common information encoding in photonics. We experimentally test the full gamut of unitary transformations for a system of two parallel beams and make a map of their fidelity. We obtain an average transformation fidelity of 0.85 ± 0.03. This high-fidelity suggests that MPLCs are a useful tool for implementing the unitary transformations that comprise quantum and classical information processing.

Modulating the signal is a common method in spectroscopy for reducing noise. However, for broadband coherent light sources like optical frequency combs (OFCs), modulation methods typically involve the use of optical modulators, making the experimental setup cumbersome. This study proposes and successfully implements a broadband Faraday modulation rotation spectroscopy (FAMOS) method combined with an OFC. The development of this method by extending the modulation frequency of the OFC from tens of MHz down to the kHz level, effectively relaxes the stringent demands for high-speed electronics and optoelectronic devices, making modulation spectroscopy techniques more practically useful for diverse real-world environments. Moreover, through specifically designed modulation strategies, this method can effectively suppress low-frequency noise, thereby significantly improving the signal-to-noise ratio of the measurements without sacrificing measurement accuracy.

Time-varying metamaterials have garnered significant attention for their ability to achieve anti-reflection in the time domain. However, current systems face limitations in spin-controlled manipulation, as most studies focus on non-chiral, time-varying metamaterials. Consequently, realizing spin-dependent broadband anti-reflection using time-varying chiral metamaterials remains underexplored. In this work, we propose a time-varying chiral structure composed of four temporal layers, each with distinct impedances and chiral parameters. By carefully adjusting these parameters across the layers, our structure enables broadband anti-reflection for both right- and left-circularly polarized (RCP and LCP) waves under small chiral conditions. Under large chiral parameters, the structure selectively achieves broadband anti-reflection for LCP waves, while consistently reflecting RCP waves across the bandwidth. This unique spin-dependent broadband anti-reflection results from significant phase delays between RCP and LCP waves, a feature not achievable by non-chiral, time-varying multilayer structures. Additionally, the proposed structure allows impedance matching between chiral and non-chiral dielectric spatial-temporal slabs in finite regions under small chiral parameters. These findings offer promising avenues for advanced wave manipulation in chiral metamaterials, with potential applications in broadband absorbers, filters, and quantum information processing systems.

This paper reports a 3.8 µm pulse burst self-optical parametric oscillator (SOPO) employing the Nd:MgO:PPLN crystal, achieving programmable mid-infrared pulse burst output based on step-active Q-switching technology. Building on the intracavity optical parametric oscillator (IOPO) theory, a theoretical model for the step-active Q-switched self-optical parametric oscillator is developed by introducing idler photon and step loss terms. The simulation results elucidate the evolution of population inversion and photon numbers and determine step-active Q-switching loss values for different sub-pulse numbers. Additionally, a 3.8 µm pulse burst laser output with a repetition rate of 10 kHz is experimentally achieved using the step-active Q-switching signal designed from the theoretical simulation. The effective programming of the step-active Q-switching signal achieves control over 2-4 sub-pulses, 260-1000 ns intervals, and any amplitude ratios. The experimental and simulation results demonstrate consistency, offering valuable insights for optimizing the Q-switching technology in other SOPO systems.