We report the experimental setup of a high power pulsed erbium-doped fiber amplifier. An optical signal at 1550nm emitted by a distributed feedback laser is amplified by two identical stages in reflective configuration using one fiber Bragg grating at each one of those. We demonstrated that for pulses with a frequency of 20kHz and temporal duration of 10, 50, 100, and 500ns, it is possible to obtain output peak powers of 41, 22, 18, and 11W, respectively. We applied our high power amplifier in the characterization of nonlinear optical transmission of single-wall carbon nanotubes deposited on single mode optical fibers end-face by the photodeposition technique. Our results show that the high power system is ideal for carrying out studies of nonlinear effects in optical fibers as well as nonlinear characterization of nanostructured materials deposited on optical fibers

A comparative study on the sensing properties of a tapered optical fiber pristine and functionalized with the palladium nanoparticles to hydrogen and volatile organic compounds (VOCs), is presented. The sensor response and, response/recovery times were extracted from the measurements of the transient response of the device. The tapered optical fiber sensor was fabricated using a single-mode optical fiber by the flame-brushing technique. Functionalization of the optical fiber was performed using an aqueous solution of palladium chloride by drop-casting technique assisted for laser radiation. The detection principle of the sensor is based on the changes in the optical properties of palladium nanoparticles when exposed to reducing gases, which causes a variation in the absorption of evanescent waves. A continuous wave laser diode operating at 1550 nm is used for the sensor characterization. The sensor functionalized with palladium nanoparticles by this technique is viable for the sensing of hydrogen and VOCs, since it shows an enhancement in sensor response and response time compared to the sensor based on the pristine optical microfiber. The results show that the fabricated sensor is competitive with other fiber optic sensors functionalized with palladium nanoparticles to the hydrogen.

Syringe-based drug delivery has been the most common and efficient method for more than a century.¹ With the advent of the COVID-19 pandemic, more than 10 billion vaccines have been administered worldwide. This number increases by at least an order of magnitude when other regularly administered vaccines are included. As a result, tens of billions of needles are produced and wasted each year. The disposal of needles requires special procedures to avoid punctures, yet accidental punctures occur among medical and cleaning staff, exposing them to highly contagious diseases such as hepatitis and human immunodeficiency virus.^2,3 In addition, needle phobia may prevent adequate treatment.⁴ To overcome these problems, needle-free injectors were developed in the 1970s,⁵ but several reasons prevented their massive use: the possibility of cross-contamination, their cost, the complexity of use, and the instability of the jet, which tends to break, causing bruising and even bleeding.^{6 – 8}