A new type of polydimethylsiloxane (PDMS) optical microring resonator on MgF2 substrate is proposed and fabricated by nano-imprint lithography. The measured quality factors of the resonators were in the order of 104 in the C band. Our work provides a new method for fabrication of on-chip whispering gallery mode resonators, which can benefit the applications in communication and sensing fields.
Tilt sensor is becoming more and more popular in many engineering fields. With the development of the sensor, tilt sensor with high sensitivity and directional is required in these fields. A simple, compact and high sensitivity fiber-optic directional tilt angle sensor is proposed and experimentally demonstrated in this paper. This novel structure is based on an asymmetrical in-line M-Z inclinometer, as a result, the structure is very compact. At the same time, the structure is easy to fabricate. Because of the asymmetrical structure, different changes happened to the sensor and the sensor can recognize the tilt direction. The tilt angle is obtained by monitoring the resonant wavelength shift and the tilt direction can be obtained from the redshift or blueshift. This structure got a very high sensitivity of 0.935nm/° in a range from -3° to 3°.
An in-fiber whispering gallery mode resonator fabricated by femtosecond laser micromaching is demonstrated. The cylinder resonator cavity is fabricated by scanning the D-fiber cladding with infrared femtosecond pulses along a cylindrical trace with radius of 25μm and height of 20μm. Quality factor on the order of 103 is achieved by smoothing the cavity surface with ultrasonic cleaner, which is mainly limited by the surface roughness of hundreds nanometers. Resonant characteristics and polarization dependence of the proposed resonator is also studied in detail. Our method takes a step forward to the integration of whispering gallery mode resonators.
An interferometric microfluidic sensor is proposed by perpendicularly coupling light into/out from a glass capillary with a pair of collimators. Light trapped in the wall of a capillary with inner and outer radius of 245μm and 413.5μm travels along different paths and interferes at the output, resulting in a multiple modes interferometer. By successively injecting salt solutions with different concentrations into the capillary air hole, red shift happens in the interferometric spectra with a sensitivity of 42.75nm/RIU. Such a sensing head offers potentials in identifying solutions in real time, especially for those not transparent for light.
The effect of fiber laser linewidth on the optical time-domain reflectometer based vibration distributed sensing regime is studied experimentally in this paper. Lasers with multi-longitudinal modes, 5 kHz and ~800 Hz linewidth single longitudinal mode are interrogated as light source successively. Experiments show that narrower linewidth laser results in higher repeatable and stable scattering spectrum. When the 800 Hz linewidth laser is modulated into 50 ns width pulses, the signal to noise ratio is ~ 6 dB and the spatial resolution is improved to 3 m, breaking the traditional theory limit.
An all-fiber accelerometer with temperature self-compensation based on Fabry-Pérot interferometer (FPI) and
simple-supported beam is proposed, where the two reflectors are the joint face between single mode fiber (SMF) and
hollow core fiber and the end face of the micro fiber used as vibration beam, respectively. The temperature effect could
be compensated by choosing proper material for the beam because it is movable in the FPI cavity. When the beam length
composed of SMF is 6 cm and the mass block is ~1.3218×10-7 Kg, the acceleration sensitivity is ~0.35 V/g and the
temperature sensitivity is less than 1pm/°C;.
A remote sensing system based on bandpass long-period fiber grating (LPFG) and fiber ring laser is proposed in this
paper. The reflective bandpass LPFG is fabricated by fusion splicing a piece of hollow core fiber (HCF) to the LPFG.
And the fiber ring laser is employed to narrow the line-width of the bandpass LPFG and realize remote sensing. As an
application example, a temperature experiment is conducted at the spot more than 1 km away from the fiber ring laser.
The experimental results show that such a sensor has a sensitivity of 0.0254nm/°C within the range of 20-150°C.