The nonlinear spatio-temporal reshaping of the window, coupled with the linear dispersion, yields outcomes that vary according to window material, pulse duration, and wavelength, with longer wavelengths exhibiting greater tolerance to intense pulses. While adjusting the nominal focus to counteract the loss of coupling efficiency, the improvement in pulse duration is negligible. From our simulations, we have derived a clear expression representing the minimal separation between the window and the HCF entrance facet. The outcomes of our study have ramifications for the frequently space-restricted design of hollow-core fiber systems, particularly when the input energy is not uniform.

Within the context of phase-generated carrier (PGC) optical fiber sensing, minimizing the nonlinear effect of variable phase modulation depth (C) on demodulation accuracy is essential for reliable performance in real-world applications. This paper describes a refined carrier demodulation method, utilizing a phase-generated carrier, for the purpose of calculating the C value while minimizing its nonlinear impact on the demodulation results. The orthogonal distance regression algorithm computes the value of C, using the fundamental and third harmonic components within its equation. Employing the Bessel recursive formula, the coefficients of each Bessel function order within the demodulation outcome are converted into C values. The calculated C values are responsible for removing the coefficients from the demodulation outcome. The ameliorated algorithm, evaluated over the C range from 10rad to 35rad, attained a total harmonic distortion of 0.09% and a maximum phase amplitude fluctuation of 3.58%. This drastically surpasses the performance of the traditional arctangent algorithm's demodulation. Experimental findings showcase the proposed method's ability to effectively remove the error introduced by C-value fluctuations, providing a valuable benchmark for signal processing techniques in real-world fiber-optic interferometric sensors.

Electromagnetically induced transparency (EIT) and absorption (EIA) are demonstrable characteristics of whispering-gallery-mode (WGM) optical microresonators. The EIT-to-EIA transition holds potential for applications in optical switching, filtering, and sensing. We present, in this paper, an observation of the transition from EIT to EIA occurring within a solitary WGM microresonator. A fiber taper is employed to couple light into and out of a sausage-like microresonator (SLM), whose internal structure contains two coupled optical modes presenting considerable disparities in quality factors. Axial stretching of the SLM produces a matching of the resonance frequencies of the two coupled modes, and this results in a transition from EIT to EIA within the transmission spectra when the fiber taper is positioned closer to the SLM. The optical modes of the SLM, exhibiting a distinctive spatial distribution, constitute the theoretical underpinning for the observation.

Through two recent publications, the authors have analyzed the spectro-temporal characteristics of random laser emission, concentrating on solid state dye-doped powders under picosecond pump conditions. At and below the threshold, each emission pulse showcases a collection of narrow peaks, with a spectro-temporal width reaching the theoretical limit (t1). This behavior results from the distribution of path lengths for photons within the diffusive active medium, where stimulated emission leads to amplification, as demonstrated by the theoretical model developed by the authors. The primary objective of this work is the development of a model, implemented and free from fitting parameters, that is compatible with both the material's energetic and spectro-temporal properties. A secondary goal is the acquisition of knowledge concerning the emission's spatial characteristics. Having measured the transverse coherence size of each emitted photon packet, we further discovered spatial fluctuations in these materials' emissions, supporting the predictions of our model.

By strategically employing adaptive algorithms, the freeform surface interferometer was able to attain the desired aberration compensation, resulting in interferograms with a sparse distribution of dark areas (incomplete). Nevertheless, traditional search methods reliant on blind approaches suffer from slow convergence, extended computation times, and a lack of user-friendliness. For an alternative, we propose an intelligent method integrating deep learning and ray tracing to recover sparse fringes from the missing interferogram data without any iterative steps. Simulated results highlight a few-second processing time for the proposed method, coupled with a failure rate below 4%. Contrastingly, the proposed technique obviates the need for pre-execution manual parameter adjustments that are mandatory in conventional algorithms. In conclusion, the practicality of the proposed method was empirically verified through the conducted experiment. We anticipate that this approach will yield far more promising results in the future.

The nonlinear optical research field has found in spatiotemporally mode-locked fiber lasers a powerful platform, characterized by a rich tapestry of nonlinear evolution processes. Minimizing the modal group delay disparity within the cavity is frequently critical for surmounting modal walk-off and realizing phase locking across various transverse modes. This paper leverages long-period fiber gratings (LPFGs) to effectively counter large modal dispersion and differential modal gain within the cavity, enabling the achievement of spatiotemporal mode-locking in step-index fiber cavities. Due to the dual-resonance coupling mechanism, the LPFG inscribed in few-mode fiber generates strong mode coupling, leading to a wide bandwidth of operation. We reveal a consistent phase difference between the transverse modes comprising the spatiotemporal soliton, using the dispersive Fourier transform, which incorporates intermodal interference. These results are of crucial importance to the ongoing exploration of spatiotemporal mode-locked fiber lasers.

A theoretical model for a nonreciprocal photon conversion process between arbitrary photon frequencies is presented within a hybrid optomechanical cavity system. Two optical cavities and two microwave cavities are each coupled to distinct mechanical resonators, through radiation pressure. learn more Two mechanical resonators are coupled together by way of the Coulomb interaction. Our research examines the non-reciprocal transitions of photons, considering both similar and different frequency types. The device's time-reversal symmetry is broken through the use of multichannel quantum interference. Our findings demonstrate the precise conditions of nonreciprocity. By altering the Coulomb forces and phase shifts, we ascertain that nonreciprocity can be modified and even converted to reciprocity. These results shed light on the design of nonreciprocal devices, including isolators, circulators, and routers, which have applications in quantum information processing and quantum networks.

We introduce a new dual optical frequency comb source, capable of high-speed measurement applications while maintaining high average power, ultra-low noise, and compactness. Employing a diode-pumped solid-state laser cavity featuring an intracavity biprism, which operates at Brewster's angle, our approach generates two spatially-separated modes with highly correlated attributes. learn more Within a 15-cm-long cavity incorporating an Yb:CALGO crystal and a semiconductor saturable absorber mirror as the end mirror, the system generates more than 3 watts average power per comb at pulse durations below 80 femtoseconds, a repetition rate of 103 gigahertz, and continuously tunable repetition rate differences reaching up to 27 kilohertz. Our study of the dual-comb's coherence using a series of heterodyne measurements, discloses key features: (1) minimal jitter in the uncorrelated part of the timing noise; (2) the free-running interferograms show distinct radio frequency comb lines; (3) we validate that interferogram analysis yields the fluctuations in the phase of all radio frequency comb lines; (4) this phase data allows for the post-processing of coherently averaged dual-comb spectroscopy on acetylene (C2H2) over extensive time scales. Employing a highly compact laser oscillator, which directly integrates low-noise and high-power operation, our results showcase a general and potent dual-comb application approach.

Periodic sub-wavelength semiconductor pillars demonstrate multiple functionalities, including light diffraction, trapping, and absorption, leading to improved photoelectric conversion in the visible spectrum, which has been extensively researched. We create and manufacture micro-pillar arrays composed of AlGaAs/GaAs multiple quantum wells to achieve superior detection of long-wavelength infrared light. learn more Compared to its planar counterpart, the array achieves a remarkable 51-fold increase in absorption at its peak wavelength of 87 meters, while simultaneously diminishing the electrical area by a factor of 4. Through simulation, it is shown that normally incident light, guided within pillars via the HE11 resonant cavity mode, generates a more robust Ez electrical field, facilitating inter-subband transitions within n-type quantum wells. Moreover, the thick active region of the dielectric cavity, comprised of 50 QW periods with a relatively low doping concentration, will be advantageous to the detectors' optical and electrical performance metrics. Employing all-semiconductor photonic designs, this investigation demonstrates an inclusive scheme to substantially enhance the signal-to-noise ratio of infrared detection.

Vernier effect-dependent strain sensors commonly encounter the dual problems of low extinction ratio and high temperature cross-sensitivity. This study presents a novel hybrid cascade strain sensor, integrating a Mach-Zehnder interferometer (MZI) and a Fabry-Perot interferometer (FPI), exhibiting high sensitivity and a high error rate (ER) leveraging the Vernier effect. The two interferometers are separated by a very long piece of single-mode fiber (SMF).