Mid-infrared interferometry with non-adiabatic tapered ZBLAN optical fiber.

This work illustrates, to the best of our knowledge, the first non-adiabatic tapered single-mode zirconium fluoride optical fiber sensor in the mid-infrared spectral range. It is designed and fabricated via pulling and heating technique. A waist diameter dw = 25 µm with no visible crystallization is achieved, overcoming the typical fluoride glass challenges associated with crystallization, narrow temperature fabrication window, and low glass transition temperature. The performance of the non-adiabatic tapered optical fiber is theoretically and experimentally investigated, demonstrating its high potential for a wide range of sensing applications in the mid-infrared spectral range.

2.8-µm polarization-maintaining Er fiber laser mode-locked by a GaSb-based SESAM.

A GaSb-based SEmiconductor Saturable Absorber Mirror (SESAM) enables continuous-wave picosecond mode-locked operation with excellent stability of a polarization-maintaining mid-infrared Er:ZBLAN fiber laser. The GaSb-based SESAM mode-locked fiber laser delivers an average output power of 190 mW at 2.76 µm at a repetition rate of 32.07 MHz (corresponding to a pulse energy of ∼6 nJ) and exhibits a high signal-to-noise ratio of ∼80 dB. The polarization extinction ratio is more than 23 dB. By employing an intracavity diffraction grating, the laser wavelength is continuously tunable across 2.706-2.816 µm. Passively Q-switched operation of this laser is also demonstrated.

Fused optical fiber combiner based on indium fluoride glass: perspectives for mid-IR applications.

For the first time, to the best of our knowledge, the design and characterization of a 3 × 1 fused fiber combiner based on multimode step-index fluoroindate optical fibers (InF3) has been performed. Several efforts to develop a well-consolidated normalization procedure and a fabrication protocol have been required due to the low melting temperature and the mechanical properties of fluoroindates. Fabrication results demonstrate repeatability and absence of crystallization. Therefore, the described fabrication process paves the way for manufacturing fluoroindate devices. The electromagnetic design of the combiner is carried out through modal investigation and beam propagation method by computing the transmission efficiency. The experimental results agree with the simulation and demonstrate the device feasibility to operate in the mid-infrared spectral range.

Femtosecond laser direct-written fiber Bragg gratings with high reflectivity and low loss at wavelengths beyond 4 µm.

We report on the fabrication of, to the best of our knowledge, the first highly reflective fiber Bragg gratings for the 4 µm wavelength range. A second-order grating with a coupling coefficient (κ) of 230m-1, losses <0.25dB/cm, and a bandwidth of approximately 3 nm was inscribed into the core of a passive indium fluoride (InF3) fiber using a femtosecond (fs) laser. Thermal annealing of this grating at a temperature of 150°C for 90 min resulted in the enhancement of κ to 275m-1. Further, we show that InF3 fibers respond very differently to irradiation with fs laser pulses as compared to ZBLAN fibers and that this difference manifests itself in a significantly larger process window for inscription and in the formation of a more complex refractive index profile that is believed to be caused by the larger nonlinearity of InF3. This Letter paves the way to the development of new wavelength stabilized all-fiber mid-infrared lasers beyond 4 µm.

Local infiltration analgesia versus interscalene nerve block for postoperative pain control after shoulder arthroplasty: a prospective, randomized, comparative noninferiority study involving 99 patients.

BACKGROUND: The aim of this study was to compare the efficacy of local infiltration analgesia (LIA) and interscalene nerve block (ISB) for early postoperative pain control after total shoulder arthroplasty (TSA). The hypothesis was that LIA is not inferior to ISB. METHODS: A prospective, randomized controlled study was performed in 2014-2016. All patients who underwent TSA for shoulder osteoarthritis were included. Patients in the ISB group received a continuous infusion of 0.2% ropivacaine by perineural catheter for 48 hours. The surgeon injected 110 mL of 0.2% ropivacaine, 30 mg of ketoprofen, and 0.5 mg of epinephrine before TSA in the LIA group and inserted a catheter into the glenohumeral joint. The next morning, 10 mL of 0.2% ropivacaine, 30 mg of ketoprofen, and epinephrine were injected through the catheter, which was then removed. The primary outcome was the mean shoulder pain score for the 48-hour postoperative period on a numerical scale (0-10). The secondary outcomes were postoperative opioid requirements, complications, and shoulder function at the 1-month follow-up visit. The sample size was calculated for a noninferiority study. RESULTS: The study included 99 patients (50 LIA and 49 ISB patients) with a mean age of 72 ± 9.6 years. Although no significant difference in the mean pain score was found between the 2 groups for the 48-hour postoperative period (1.4 ± 0.9 for LIA vs 1.7 ± 1 for ISB, P = .19), the LIA group had significantly less severe pain (P = .003) and less opioid consumption (P = .01) in the recovery room. No complications occurred. A negative but nonsignificant correlation was found between postoperative pain and Constant score at the 1-month follow-up. CONCLUSION: LIA is not less effective than ISB for early postoperative pain control after TSA.

Infrared supercontinuum generated in concatenated InF3 and As2Se3 fibers.

We report on infrared supercontinuum (SC) generation through subsequent nonlinear propagation in concatenated step-index fluoride and As2Se3 fiber. These fibers were pumped by an all-fiber laser source based on an erbium amplifier followed by a thulium power amplifier. ZBLAN and InF3 fibers were compared for the concatenated scheme. The broadest SC produced was achieved by optimizing the length of the InF3 fiber. This arrangement allowed the generation of 200 mW infrared SC with high spectral flatness and spanning from 1.4 µm to 6.4 µm.

Emission beyond 4 µm and mid-infrared lasing in a dysprosium-doped indium fluoride (InF3) fiber.

Optical emission from rare-earth-doped fluoride fibers has thus far been limited to less than 4 µm. We extend emission beyond this limit by employing an indium fluoride (InF3) glass fiber as the host, which exhibits an increased infrared transparency over commonly used zirconium fluoride (ZBLAN). Near-infrared pumping of a dysprosium-doped InF3 fiber results in broad emission centered around 4.3 µm, representing the longest emission yet achieved from a fluoride fiber. The first laser emission in an InF3 fiber is also demonstrated from the 3 µm dysprosium transition. Finally, a frequency domain excited state lifetime measurement comparison between fluoride hosts suggests that multiphonon effects are significantly reduced in indium fluoride fiber, paving the way to more efficient, longer wavelength lasers compared to ZBLAN fibers.

Supercontinuum generation in ZBLAN glass photonic crystal fiber with six nanobore cores.

Photonic crystal fibers (PCFs) made from ZBLAN glass are of great interest for generating broadband supercontinua extending into the ultraviolet and mid-infrared regions. Precise sub-micrometer structuring makes it possible to adjust the modal dispersion over a wide range, making the generation of new frequencies more efficient. Here we report a novel ZBLAN PCF with six cores, each containing a central nanobore of a diameter ∼330 nm. Each nanobore core supports several guided modes, and the presence of the nanobore significantly modifies the dispersion, strongly influencing the dynamics and the extent of supercontinuum generation. Spectral broadening is observed when a single core is pumped in the fundamental and first higher order core modes with 200 fs long pulses at a wavelength of 1042 nm. Frequency-resolved optical gating is used to characterize the output pulses when pumping in the lowest order mode. The results are verified by numerical simulations.

Mid-IR supercontinuum from 2.4 to 5.4 µm in a low-loss fluoroindate fiber.

A mid-infrared supercontinuum extending up to 5.4 µm is generated in a low-loss fluoroindate fiber. It is pumped with an erbium-doped fluoride fiber amplifier seeded with 400 ps pulses at 2.75 µm. Both fibers are fusion spliced to increase the robustness and long-term stability of the system. With more than 82% of the total power beyond 3 µm, this approach is promising for efficient mid-IR light generation.