Fiber Coupling Research Articles

A 2 µm Gallium Antimonide Semiconductor Laser Based on Slanted, Wedge-Shaped Microlens Fiber Coupling

Semiconductor lasers with a wavelength of 2 µm, composed of antimonide materials, find important applications in trace gas detection, laser medicine, and free-space optical communication, among others. In this paper, a more suitable microlens shape for 2 µm gallium antimonide semiconductor lasers is designed. Based on the fiber coupling efficiency model, the parameters of the designed slanting wedge-shaped microlens fiber are optimized to improve laser beam quality. The large tangent angle on both sides of the slanted, wedge-shaped microlens fiber is calculated using Snell’s law, and the fiber core diameter and small wedge angle are determined through space fiber coupling experiments. After packaging the fiber coupling module with the chip, the laser output beam exhibits good overall symmetry in the spot with a uniform intensity distribution. The maximum output power is approximately 210 mW, demonstrating good power stability.

A multi-core fiber coupler without a central core

An efficient method for fabricating multi-core fiber couplers based on the thermal diffusion technique is proposed to realize the connection of single-mode fibers to multi-core fibers without a central core. The fabrication efficiency of the multi-core fiber coupler is improved by fiber-loaded hydrogen. The simulation results show that the single-mode fiber and the multi-core fiber can be coupled stably and efficiently by using the designed double-clad fiber to connect the single-mode fiber and the multi-core fiber. Double-clad fiber and multi-core fiber were loaded with hydrogen to enhance the dopant diffusion rate. Three-dimensional refractive index measurements of the multi-core fiber coupler show that the dopant diffusion rate and the diffusion zone length of the hydrogen-loaded fiber are significantly increased compared to the original fiber. These enhancements contributed to the shorter fabrication time of multi-core fiber couplers. The multi-core fiber couplers fabricated by thermal diffusion technology have the advantages of high coupling efficiency, high integration, simple manufacture, and high mechanical strength. Enhancing the diffusion rate of optical fibers by using the hydrogen loading method will increase the application potential of multi-core optical fiber couplers prepared by thermal diffusion technology, and accelerate the translation of multi-core fibers toward optical communication and optical fiber sensing.

Shot-noise limited optical hybrid based on fused fiber couplers

We describe a fiber-based coherent receiver topology which utilizes intrinsic phase shifts from fiber couplers to enable instantaneous quadrature projection with shot-noise limited signal-to-noise ratio (SNR). Fused 3 × 3 fiber couplers generate three phase-shifted signals simultaneously that can be combined with quadrature projection methods to detect magnitude and phase unambiguously. We present a novel, to the best of our knowledge, differential detection topology which utilizes a combination of 3 × 3 and 2 × 2 couplers to enable quadrature projection with fully differential detection. We present a mathematical analysis of this 3 × 3 differential detection topology, extended methods for signal calibration, and SNR analysis. We characterize the SNR advantage of this approach and demonstrate a sample application illustrating simultaneous magnitude and phase imaging of a chrome-on-glass test chart.

Direct laser-written optomechanical membranes in fiber Fabry-Perot cavities

Integrated micro- and nanophotonic optomechanical experiments enable the manipulation of mechanical resonators on the single phonon level. Interfacing these structures requires elaborate techniques limited in tunability, flexibility, and scaling towards multi-mode systems. Here, we demonstrate a cavity optomechanical experiment using 3D-laser-written polymer membranes inside fiber Fabry-Perot cavities. Vacuum coupling rates of g0/2π ≈ 30 kHz to the fundamental megahertz mechanical mode are reached. We observe optomechanical spring tuning of the mechanical resonator frequency by tens of kilohertz exceeding its linewidth at cryogenic temperatures. The direct fiber coupling, its scaling capabilities to coupled resonator systems, and the potential implementation of dissipation dilution structures and integration of electrodes make it a promising platform for fiber-tip integrated accelerometers, optomechanically tunable multi-mode mechanical systems, and directly fiber-coupled systems for microwave to optics conversion.

Measurement and Nonlinear Correction of Instantaneous Relative Frequency of High-Speed FMCW Laser Signal Based on 3×3 Fiber Coupler

Measurement and Nonlinear Correction of Instantaneous Relative Frequency of High-Speed FMCW Laser Signal Based on 3×3 Fiber Coupler

Optical circuit compactification for ultracold atoms.

We develop a modular and compactified optical circuit for the generation of optical beams for cooling, imaging, and controlling ultracold atoms. One of the simplifications that is made in our circuit is to admix the repumping beams to each other optical beams in its dedicated single-mode fiber. We implement our design, characterize the output, and show that the optical power efficiency of the circuit is in the region of 97%, and after fiber coupling, the efficiencies are in the range of 62-85%. Given its compact design and controllable optical sources, this setup should be adaptable to a variety of quantum experiments based on ultracold gases.

About the influence of high temperature or fire testing conditions on the tensile behavior of carbon reinforced poly phenylene sulfide laminates

This study aims to investigate the thermo-mechanical coupling in carbon fibers reinforced Poly Phenylene Sulfide (PPS) laminates subjected to critical temperature conditions. In order to dissociate the physical phenomena (degradation/decomposition on the one hand and deformation/damage mechanisms on the other hand) at play in quasi-isotropic laminates (fiber-dominated mechanical behavior), homogenous and fire testing conditions (heterogenous) were considered with or without mechanical loading. X-Ray tomographic and fractographic analyses were conducted to identify the role played by porosities formation (resulting from thermally induced deformations and damages) on the structural bearing capabilities of C/PPS laminates to be used in high-temperature environments. Under high temperature conditions (homogenous temperature distribution), the retention of tensile properties is not well preserved as the axial stiffness and strength decrease of 50% and 75%, respectively. Under fire conditions (heterogenous temperature distribution), the degradation of tensile properties is more dramatic with an 80% decrease.

Fused Fiber Coupler Demux as an Edge Filter for Optical Sensing: A Low Cost Solution

Fused Fiber Coupler Demux as an Edge Filter for Optical Sensing: A Low Cost Solution

Fiber Coupling System and Beam Shaping Design for High-Power Semiconductor Laser Stack

Fiber Coupling System and Beam Shaping Design for High-Power Semiconductor Laser Stack

High efficiency grating couplers for strain tunable GaAs quantum dot based entangled photon sources

The on-chip integration of single photon and entangled photon emitters such as epitaxially grown semiconductor quantum dots into photonic frameworks is a rapidly evolving research field. GaAs quantum dots offer high purity and a high degree of entanglement due to, in part, exhibiting very small fine structure splitting along with short radiative lifetimes. Integrating strain-tunable quantum dots into nanostructures enhances the quantum optical fingerprint, i.e., radiative lifetimes and coupling of these sources, and allows for on-chip manipulation and routing of the generated quantum states of light. Efficient out-coupling of photons for off-chip processing and detection requires carefully engineered mesoscopic structures. Here, we present numerical studies of highly efficient grating couplers reaching up to over 90% transmission. A 2D Gaussian mode overlap of 83.39% for enhanced out-coupling of light from within strain-tunable photonic nanostructures for free-space transmission and single-mode fiber coupling is shown. The photon wavelength under consideration is 780 nm, corresponding to the emission from GaAs quantum dots resembling the 87Rb D2 line. The presented numerical study helps implement such sources for applications in complex quantum optical networks.

Design and Error Analysis of a Fiber Coupling System Based on THz-TDS Common Optical Path

Design and Error Analysis of a Fiber Coupling System Based on THz-TDS Common Optical Path

Rapid Analysis of Fentanyl and Fentanyl Analogues from Whole Blood Using SPME Coupled to the Microfluidic Open Interface.

Fentanyl and its analogues are potent opioids that pose a significant threat to society. Over the last several years, considerable focus has been on the concerning trend of increasing fentanyl usage among drug users. Fentanyl analogues are mainly synthesized to evade analytical detection or increase their potency; thus, very low concentrations are sufficient to achieve a therapeutic effect. In an effort to help combat the synthetic opioid epidemic, developing targeted mass spectrometric methods for quantifying fentanyl and its analogues at ultralow concentrations is incredibly important. Most methods used to analyze fentanyl and its analogues from whole blood require manual sample preparation protocols (solid-phase extraction or liquid-liquid extraction), followed by chromatographic separation and mass spectrometric detection. The main disadvantages of these methods are the tedious sample preparation workflows, resulting in lengthy analysis times. To mitigate these issues, we present a targeted method capable of analyzing 96 samples containing fentanyl, several fentanyl analogues, and a common fentanyl (analogue) precursor simultaneously in 2.4 min per sample. This is possible by using a high-throughput solid phase microextraction workflow on the Concept96 autosampler followed by manual coupling of solid-phase microextraction fibers to the microfluidic open interface for tandem mass spectrometry analysis. Our quantitative method is capable of extremely sensitive analysis, with limits of quantification ranging from 0.002 to 0.031 ng mL-1 and linearity ranging from 0.010 to 25.0 ng mL-1. The method shows very good reproducibility (1-18%), accuracy (81-100%) of calibration and validation points, and good interday reproducibility (6-15%).

WaveFlex Biosensor-Using Novel Tri-Tapered-in-Tapered Four-Core Fiber With Multimode Fiber Coupling for Detection of Aflatoxin B1

WaveFlex Biosensor-Using Novel Tri-Tapered-in-Tapered Four-Core Fiber With Multimode Fiber Coupling for Detection of Aflatoxin B1

Higher-order matrix nonlinear Schrödinger equation with the negative coherent coupling: binary Darboux transformation, vector solitons, breathers and rogue waves

Optical fiber communication plays a crucial role in modern communication. In this work, we focus on the higher-order matrix nonlinear Schrödinger equation with negative coherent coupling in a birefringent fiber. For the slowly varying envelopes of two interacting optical modes, we construct a binary Darboux transformation using the corresponding Lax pair. With vanishing seed solutions and the binary Darboux transformation, we investigate vector degenerate soliton and exponential soliton solutions. By utilizing these soliton solutions, we demonstrate three types of degenerate solitons and double-hump bright solitons. Furthermore, considering non-vanishing seed solutions and applying the binary Darboux transformation, we obtain vector breather solutions, and present the vector single-hump beak-type Akhmediev breather, Kuznetsov-Ma breathers, double-hump beak-type Akhmediev breather, Kuznetsov-Ma breathers, and vector degenerate beak-type breathers. Additionally, we take the limit in the breather solutions and derive vector rogue wave solutions. We illustrate the beak-type rogue waves and bright-dark rogue waves. Humps of these vector double-hump waves can separate into two individual humps. The results obtained in this work may potentially provide valuable insights for experimentally manipulating the separation of two-hump solitons, breathers, and rogue waves in optical fibers.

Self-starting mode-locking in an all-PM Yb-doped fiber laser oscillator enabled by a 3x3 nonlinear optical lossy loop mirror

Ultrafast fiber oscillators based on loop mirror saturable absorbers often suffer from a problematic self-starting mode-locking operation. It is usually necessary to provide an additional phase shift in the loop, guaranteeing repeatable initiation of the pulsed regime. 3x3 even splitting ratio fiber couplers have recently introduced a required phase shift in an all-fiber loop mirror architecture. Until now, mode-locking induced by a 3x3 fiber coupler has been associated only with nonlinear amplifying loop mirrors. Here, we present a self-starting ultrafast dispersion-managed all-polarization-maintaining Yb-doped oscillator that utilizes a nonlinear optical lossy loop mirror instead. We show three ways of inserting asymmetric losses in a loop via a variable optical attenuator, a fiber coupler, and a very simple lossy splice. Complete characterization of all output ports of the oscillator proves significant spectral and temporal breathing of the pulse when circulating through the net normal dispersion cavity, which can deliver nJ-level pulse energy. The system guarantees excellent stability, low noise and performance comparable to nonlinear amplifying loop mirrors while being simpler, cheaper, and providing more usable output ports with different pulse characteristics.

Estimation of atmospheric refractive index structure constant using an InGaAs/InP single-photon detector.

Remote sensing of atmospheric refractive index structure constant ($\boldsymbol{C}_{\boldsymbol{n}}^2$) using lidar incorporating a single-photon detector (SPD) is proposed. The influence of turbulence on the fiber coupling efficiency with different fiber modes is analyzed. $\boldsymbol{C}_{\boldsymbol{n}}^2$ can be derived from the ratio of the backscattering signals counted on single-mode and multimode fiber-coupling channels of the SPD. In the experiment, by eliminating the shot noise effect on the fluctuation of the ratio, the lowest coupling ratio is used to retrieve $\boldsymbol{C}_{\boldsymbol{n}}^2$ and demonstrated by comparing to the results measured from a large aperture scintillometer (LAS). Good agreement between results from the LAS and the lidar is achieved. The correlation coefficients are 0.90, 0.89, and 0.89, under three different weather conditions.

A direct method for measuring modal coupling and attenuation coefficients of few-mode fibers

A direct method for measuring modal coupling and attenuation coefficients of few-mode fibers

Directional sources and distributed acoustic sensing deployments for near-surface characterization

Active near-surface surveys using distributed acoustic sensing (DAS) have been practically limited to 2D inline acquisitions followed by Rayleigh-wave dispersion analysis. In this study, we analyze different acquisition setups and the subsurface properties that can be estimated from them. First, we find a surface survey dedicated to Love-wave acquisition. We use a horizontal source and common-receiver sorting of the DAS data for a pure Love-wave velocity dispersion analysis yielding an S-wave velocity profile. Common-receiver sorting has the added benefit of practically eliminating the effect of the gauge length. Next, downhole DAS is used in a vertical seismic profile-type survey to recover a 1D P-wave velocity through checkshot analysis. Finally, we find that the horizontal portion of a fiber deployed in a deviated borehole records high-frequency data from surface sources. We use first arrivals for diving-wave tomography, yielding a 2D P-wave velocity model above and below the fiber. We validate the inversion results of all acquisitions through a comparison with geophone-derived velocity models. We conclude that source orientation plays a crucial role and should be considered during survey planning in conjunction with DAS directivity. As anticipated, fiber coupling can strongly influence the signal-to-noise ratio and needs to be adequately planned. In vertical boreholes, infilling offers a viable solution for deployment in existing wells. For deviated boreholes, installation inside the casing yields suboptimal coupling, but more adequate deployment protocols may yield high-frequency data useful for velocity model building and imaging. From a practical point of view, the acquisitions that we describe are difficult to justify due to their operational costs and limitations. Nonetheless, they highlight the potential of DAS in going beyond traditional analysis.

Fabrication and characterization of indium fluoride multimode fused fiber couplers for the mid-infrared.

Results of the fabrication and characterization of optical fiber couplers made of multimode step-index fluoroindate (InF3) fibers are presented. The fabrication setup was customized for this type of glass with a constant source of controlled nitrogen flow heated to a target temperature with an accuracy ±1°C. Combined with a novel fast fusion approach and with excellent control of the viscosity throughout the process, the clean gas flow and well-controlled temperature enable the fabrication of fused fiber couplers absent of any noticeable crystallization. A coupling ratio of 45/55 was achieved, with an excess loss of 0.35 dB, at 1.7 µm. To the best of our knowledge, this represents the first low excess loss (<1 dB), multimode, InF3 fiber couplers.

KSPGD algorithm to restrain the influence of measurement noise in adaptive fiber coupling

KSPGD algorithm to restrain the influence of measurement noise in adaptive fiber coupling