Manipulation of spontaneous emission in a tapered photonic crystal fibre

Light-controllable photoresponsive liquid-crystal photonic crystal fiber

We have developed all-optical modulation of photonic crystal fiber (PCF) by infiltrating photoresponsive liquid crystal (LC) into the voids within the cladding structure. The photo-induced phase transformation of the photoresponsive LC modulates the effective refractive index of the photoresponsive LC-filled cladding, thereby creating an environment of modifiable total internal reflection that tunes the output intensity of guided light upon the stimulus of optical field. The modulation range for the 632 nm wavelength is 10 dB and the response time for switching is less than 1 second by manually obstructing the pumping light path. In addition to altering the power of the pumping laser to actively tune the output intensity, the polarization direction of the pumping laser can also tune the output intensity by 5 dB.

Fluorescence pH probe based on microstructured polymer optical fiber

A kind of optical pH sensor was demonstrated that is based on a pH-sensitive fluorescence dye-doped (eosin) cellulose acetate (CA) thin-film modified microstructured polymer optical fiber (MPOF). It was obtained by directly inhaling an eosin-CA-acetic acid mixed solution into array holes in a MPOF and then removing the solvent (acetic acid). The sensing film showed different fluorescence intensities to different pH solutions in a pH range of 2.5-4.5. Furthermore, the pH response range could be tailored through doping a surfactant, hexadecyl trimethyl ammonium bromide (CTAB), in the sensing film.