With a unique 3D geometry, a broadband polarizer and single-polarization resonator are demonstrated by wrapping a microfiber on a specialized rod with a hybrid polymer-metal-dielectric nanostructure, respectively. The polarizer has an extinction ratio of more than 20 dB over the spectra range of 450 nm. The resonator has a Q-factor of ~ 80,000 with excellent suppressing of polarization noise. By functionalizing the rod surface with nanoscale silver film and tuning the coil geometry, performances can be improved by optimizing those parameters. Such kind of miniature singlepolarization microfiber and resonator are impossible to be realized by conventional fabrication process, and has the potential in gyro and current sensors.
We propose optical frequency comb generation in a monolithic micro-ring resonator. Being different from the previously reported nonlinear optical frequency combs, our scheme is based on more efficient quadratic frequency conversion rather than the third-order nonlinearity. To overcome the phase mismatch, a partly poled nonlinear ring is employed. Cascading second harmonic generation and parametric down conversion processes thus are realized through quasi-phase matching (QPM). Coupling equations are used to describe the related nonlinear interactions among different whispering-gallery modes, showing some interesting characteristics that are different from conventional QPM technology.
Condensed matter systems are potential candidates to realize the integration of quantum information circuits. Surface
phonon polariton (SPhP) is a special propagation mode in condensed matter systems. We present an investigation on the
entanglement of SPhP modes. The entangled pairs are generated from entangled photons injected to the system.
Quantum performances of entangled SPhPs are investigated by using the interaction Hamiltonian and the perturbation
theory. The wave mechanics approach is taken to describe the coupling process as a comparison. Finally, the correlation
of system is examined. A whole set of descriptions of SPhP entanglement thus are presented.
There are two steps to obtain as small as possible fiber Bragg gratings. First, it is to taper the fiber and reduce its diameter. A subwavelength-scale microfiber (MF) is the basic element of miniature fiber devices and sub-systems. Then it is to reduce the grating length. For short fiber grating, strong refractive index modulations are necessary. Strong refractive index modulations can be obtained inducing surface corrugation by alternating layers of different materials, one of which can be air. Several techniques have been proposed for the fabrication of surface-corrugated fiber gratings, including photorefractive inscription using etching, femtosecond lasers, and focused ion beam (FIB). So far, FIB is the most flexible and powerful tool for patterning, cross- sectioning or functionalizing a subwavelength circular MF due to its small and controllable spot size and high beam current density. In past two years, a number of ultra-compact surface corrugated microfiber Bragg gratings (SCMGs) have been successfully fabricated by FIB milling. The length of FIB milled SCGMs can be as small as tens of micrometers. In addition, there are several novel proposals on SCMG including wrapping a microfiber on a microstructure rod or put a microfiber on a surface-corrugated planar grating. In this paper, we will introduce recent advances in these ultra-small SCMGs and their characteristics and applications.
We experimentally demonstrate a compact microfiber Bragg grating (MFBG) force sensor that offers greater sensitivity under load. The FBG is fabricated by focused ion beam (FIB) milling a microfiber tapered from nonphotosensitive standard single-mode fiber. It is only ~58μm in length. The force sensitivity of the MFBG is as high as ~4133nm/N around the resonant wavelength of 1550nm, which is three orders of magnitude larger than that recorded in FBGs inscribed in untapered fibers.
We propose a novel all-fiber vibration sensor without any bulk optical element by employing an in-line nano-wire grid (NWG) fiber polarizer. The NWG is directly fabricated on tip of a single mode fiber (SMF) by focused ion beam technology. According to effective medium theory, the sub-wavelength NWG has strong polarization properties. In our experiment, the reflection contrast between transverse electric and transverse magnetic modes reaches 14 dB, which is sensitive enough to monitor polarization change induced by photoelastic effect. We apply a sinusoidal vibration signal generated by a piezoelectric transducer onto the fiber. The output light signal from the SMF coincides well with the vibration source. The frequency response of the sensor is measured from 20 Hz to 4 kHz showing great consistency.
We fabricate a miniature tapered photonic crystal fiber (PCF) interferometer with enhanced sensitivity by a new acid
microdroplets etching method. This method, without elongating the PCF, moving and re-fixing the device during etching
and measuring refractive index sensitivity, is very simple, cost-efficient and highly stable over time. We investigate the
refractive index sensing properties with different PCF diameters both theoretically and experimentally. The size
decreases and the sensitivity increases an order of magnitude after etching the PCF. If we can optimize the etching
process, we can fabricate more uniformly and thinly tapered PCF interferometer with higher sensitivity (~ 100 times)
theoretically in the future.
By modifying the resonant condition of microfiber resonator sensors while taking the coupling effect into account, we
theoretically investigate coupling influence on the resonant wavelength and sensitivity. Numerical calculation shows
significant difference in resonant wavelength and sensitivity with different coupling strength. Tuning the coupling can
shift the resonant position as far as several nanometers and change the sensitivity as large as 30 nm/RIU in an
all-coupling microfiber coil resonator.
In this paper we investigate the temperature characteristic of an optical microfiber coil resonator (OMCR) which is
wrapped on Teflon coated PMMA rob and embedded in low index polymer Teflon. The micro fiber used to fabricated
the OMCR was 4 ~ 5μm in diameter and 14 mm in waist region length. The PMMA rob has a diameter of 2 mm. Our
sample shows high temperature sensitivity as much as 80 pm/°C. The test result suggests OMCR could be of good value
in application of temperature sensing.
We report a miniaturized fiber probe inline reflective interferometer (FPIRI) sensor,
with a several μ-micro-notch cavity fabricated for highly sensitive refractive index
measurement. Its sensitivity in liquid is ~100 nm/RIU (refractive index unit) near the
wavelength of 1550 nm with a high extinction ratio. This probe sensor is very compact, stable,
and cheap, offering great potentials for detecting inside sub-wavelength particles or biocells.
We present a mathematical model exemplifying the manufacture of microfiber coil resonators (MCRs) with rotational and translational stages controlled by a computer. The MCR profiles are related to the stage positions; the result is important for practical manufacturing and application of MCRs.
An approach to improve the coupling efficiency of bidirectional optical subassembly (BOSA) modules is proposed and experimentally demonstrated. We analyzed the wavefront aberration coefficients of a typical BOSA. It was found that the 45-deg wavelength filter induces coma and astigmatism, and then it further deteriorates the laser diode to fiber coupling. We measured the BOSA efficiencies based on a series of different filters. For a typical 0.5-mm filter, 25% coupling efficiency improvement was achieved by optimizing the filter parameters.