Ivan Hernandez-Romano

Optical fiber temperature sensor based on a microcavity with polymer overlay

An ultracompact, cost-effective, and highly accurate fiber optic temperature sensor is proposed and demonstrated. The sensing head consists of Fabry-Perot microcavity formed by an internal mirror made of a thin titanium dioxide (TiO2) film and a microscopic segment of single-mode fiber covered with Poly(dimethylsiloxane) (PDMS). Due to the high thermo-optic coefficient of PDMS the reflectance of the fiber-PDMS interface varies strongly with temperature which in turn modifies the amplitude of the interference pattern. To quantify the changes of the latter we monitored the visibility of the interference pattern and analyzed it by means of the fast Fourier transform. Our sensor exhibits linear response, high sensitivity, and response time of 14 seconds. We believe that the microscopic dimensions along with the performance of the sensor here presented makes it appealing for sensing temperature in PDMS microfluidic circuits or in biological applications.

Mode-locked fiber laser using an SU8/SWCNT saturable absorber.

We report the fabrication of a saturable absorber based on SU8 single wall carbon nanotube (SWCNT) composite material. Thin films with a controllable thickness can be fabricated using a simple and reliable process. These films can be inserted between two FC/APC connectors in order to have an inline saturable absorber. A passive mode-locked laser was built by interleaving the fiberized saturable absorber in an erbium-doped fiber (L-band) ring cavity laser. The laser produces 871 fs pulses with a repetition rate of 21.27 MHz and a maximum average power of 1 mW.

Surface Plasmon Resonance-Based Optical Fiber Embedded in PDMS for Temperature Sensing

A compact, simple-to-fabricate, low-cost, and highly sensitive optical fiber temperature sensor based on surface plasmon resonance (SPR) is reported. The sensor consists of a core mismatch fiber structure fabricated by splicing a small piece of single-mode fiber (SMF) between two multimode fibers (MMF). SPR is generated when evanescent field interacts with the gold layer deposited over the SMF cladding. Then, the sensor was embedded in polydimethylsiloxane (PDMS), which acts as a temperature to refractive index transducer. Due to PDMS high thermooptic coefficient, the SPR dip underwent a noticeable wavelength shift when a variation of temperature occurred. The device was tested in the 20-60 °C range showing a linear response and a sensitivity of 2.60 nm/°C. This sensor is appealing for temperature monitoring in microfluidic devices made of PDMS due to its high performance and simply fabrication process.

Hybrid Mode Locked Fiber Laser Using a PDMS/SWCNT Composite Operating at 4 GHz

A hybrid mode-locked Erbium-doped fiber laser that provides very short pulse-widths while achieving high repetition rates is proposed and experimentally demonstrated. This hybrid configuration is realized by using a thin film of polydimethylsiloxane (PDMS) doped with single wall carbon nanotubes (SWCNT). This PDMS/SWCNT composite acts as a saturable absorber and is inserted within an active mode-locked laser system using angled connectors. Therefore, the effect of the PDMS/SWCNT composite is to effectively narrow the width of the pulses generated by the active system without modifying its repetition rate. A pulse-width of 730 fs was generated at a repetition rate of 4 GHz, while achieving an average output power of 4 mW. A reduction in the noise of the photodetected RF spectrum was also observed in the hybrid system.

Fiber optic vibration sensor based on Multimode Interference effects

A fiber optic vibration sensor based on Multimode Interference (MMI) effects is demonstrated. The proposed sensor is tested by characterizing its bending response, impulse response, and its response to fixed external frequencies. Induced vibration is measured in the range from 0 Hz to 2.5 kHz; the main frequency component overcomes on the first and second harmonics with a difference of 32.4 dB and 37.2 dB, respectively.

Fiber Optic Bending Sensor Based on Multimode Interference (MMI) Effects

Here we report a fiber bending sensor based on multimode interference effects. Sensing is achieved through losses induced in the propagating modes, which directly affects the intensity of the imaged formed by the multimode fiber.

Microsecond switching of plasmonic nanorods in an all-fiber optofluidic component

As information technologies move from electron-to photon-based systems, the need to rapidly modulate light is of paramount importance. Here, we study the evolution of the electric-field-induced ali ...

Refractive Index sensor using a Two-Core optical fiber

A Refractive Index sensor based on a Two-Core optical fiber is demonstrated. The sensor response and sensitivity can be easily adjusted by simply controlling an etching process to expose the off-axis core. The proposed RI sensor exhibits a sensitivity exceeding 2,100 nm/RIU.

Fabrication of PDMS/SWCNT thin films as saturable absorbers

We present a novel technique to fabricate a saturable absorber thin film based on Polydimethylsiloxane doped with Single Wall Carbon Nanotubes. Using this film a passive mode-locked fiber laser in a standard ring cavity configuration was built by inserting the film between two angled connectors. Self-starting passively mode-locked laser operation was easily observed. The generated pulses have a width of 1.26 ps at a repetition rate of 22.7 MHz with an average power of 4.89 mW.

4 GHz hybrid mode-locked fiber laser using PDMS/SWCNT thin film composite

A hybrid mode-locked fiber laser was built by using a PDMS/SWCNTs film as a saturable absorber. The system allows for a high repetition rate of 4 GHz, while achieving pulse widths of 730 fs.