This paper presents an all-silica miniature optical fiber pressure/acoustic sensor based on the Fabry-Perot (FP) interferometric principle. The endface of the etched optical fiber tip and silica thin diaphragm on it form the FP structure. The uniform and thin silica diaphragm was fabricated by etching away the silicon substrate from a commercial silicon wafer that has a thermal oxide layer. The thin film was directly thermally bonded to the endface of the optical fiber thus creating the Fabry-Perot cavity. Thin films with a thickness from 1µm to 3µm have been bonded successfully. The sensor shows good linearity and hysteresis during measurement. A sensor with 0.75 µm-thick diaphragm thinned by post silica etching was demonstrated to have a sensitivity of 11 nm/kPa. The new sensor has great potential to be used as a non-intrusive pressure sensor in a variety of sensing applications.

This paper presents a fast, highly sensitive and low-cost tapered optical fiber biosensor that enables the label-free detection of biomolecules. The sensor takes advantage of the interference effect between the fiber’s first two propagation modes along the taper waist region. The biomolecules bonded on the taper surface were determined by demodulating the transmission spectrum phase shift. Because of the sharp spectrum fringe signals, as well as a relatively long biomolecule testing region, the sensor displayed a fast response and was highly sensitive. To better understand the influence of various biomolecules on the sensor, a numerical simulation that varied biolayer parameters such as thickness and refractive index was performed. The results showed that the spectrum fringe shift was obvious to be measured even when the biolayer was only nanometers thick. A microchannel chip was designed and fabricated for the protection of the sensor and biotesting. Microelectromechanical systems (MEMS) fabrication techniques were used to precisely control the profile and depth of the microchannel on the silicon chip with an accuracy of 2 μm. A tapered optical fiber biosensor was fabricated and evaluated with an Immune globulin G (IgG) antibody-antigen pair.

This paper presents the design, fabrication and characterization of a broadband miniature fiber optic ultrasound generator based on photoacoustic (PA) ultrasound generation principle for biomedical ultrasound imaging and ultrasound non-destructive test (NDT) applications. A novel PA generation material, gold nanocomposite, was synthesized by directly reducing gold nanoparticles within polydimethylsiloxane (PDMS) through a one-pot protocol. The fiber optic ultrasound generator was fabricated by coating the gold nanocomposite on the tip of the optical fiber. The efficiency of the PA generation using gold nanocomposite was increased 10⁵ compared to using aluminum thin film and 10³ compared to using graphite mixed within epoxy. The ultrasound profile and the acoustic distribution have been characterized. The amplitude of the generated ultrasound signal was as high as 0.64 MPa and the bandwidth was more than 20 MHz. This paper also demonstrated its capability for ultrasound imaging of a tissue specimen.

Photoacoustic generation is an attractive alternative to generate ultrasound due to its broad bandwidth and high frequency capabilities. However, the challenges in low generation efficiency need to be addressed. In order to address this issue, a one-pot synthesized polydimethylsiloxane-gold nanoparticle (PDMS/Au NP) nanocomposite was utilized to generate ultrasonic pulses excited by a nanosecond laser. The enhanced efficiency of the photoacoustic signal was investigated by varying the concentration and the thickness of the nanocomposite film. The optimal peak-to-peak amplitude of the acoustic signal was observed to be 189.49 kPa under the laser energy density of $13\mathrm{mJ}/{\mathrm{cm}}^2$ at 1.8 mm away from the nanocomposite film, when the thickness and the concentration of the film were 450 μm and 1.79 wt. %, respectively. Furthermore, the efficiency of the photoacoustic generation was increased 3 orders of magnitude compared to the aluminum thin film. The results indicate that high photoacoustic generation efficiency could be achieved through the PDMS/Au NPs nanocomposite.

This paper presents the design, fabrication and testing of a diaphragm-based, all-silica fiber tip pressure sensor. A piece of 1.2-μm thick silica diaphragm was thermally bonded to the end face of an etched fiber with an outer diameter (OD) of 125 μm to form a Fabry-Perot (FP) interferometer. The diameter of the etched FP cavity is 105 μm, enabling the sensing area to be large, and thus a static pressure sensitivity of 12.4 nm/kPa (85.3 nm/psi) is accomplished with no need of any post polishing or etching. The sensor also shows a low temperature cross sensitivity during tests, owing to its all-silica structure. It is suitable for extensive production and it has a great potential to work in applications where miniature size and high sensitivity are essential, such as medical applications.

Distributed fiber optic sensors (DFOS) have become a new method for continuously monitoring infrastructure status. However, the fiber’s fragility and the installation’s complexity are some of the main drawbacks of this monitoring approach. This paper aims to overcome this limitation by embedding a fiber optic sensor into a textile for a faster and easier installation process. To demonstrate its feasibility, the smart textile was installed on a pedestrian bridge at the University of Massachusetts Lowell. In addition, dynamic strain data were collected for two different years (2021 and 2022) using Optical Frequency Domain Reflectometry (OFDR) and compared, to determine the variability of the data after one year of installation. We determined that no significant change was observed in the response pattern, and the difference between the amplitude of both datasets was 14% (one person jumping on the bridge) and 43% (two people jumping) at the first frequency band. This result shows the proposed system’s functionality after one year of installation, as well as its potential use for traffic monitoring.