Jie Hu

We report the experimental demonstration of a multiwavelength passively mode-locked fiber laser based on an all-fiber Lyot filter (AFLF). The Lyot filter is composed of two 45°-titled fiber gratings (45°-TFGs) and a length of polarization-maintaining fiber (PMF). The free spectrum range (FSR) and the 3-dB bandwidth of the Lyot filter are 7.5 nm and 3.6 nm, respectively. The laser generates 5-wavelength mode-locked pulses, which have 7.49 nm channel spacing, 192.6 kHz fundamental repetition rate and over 50 dB signal-to-noise ratio (SNR). As increasing the pump power from 178 mW to 407 mW, the pulse width and the average output power increased linearly from 10 ns to 23 ns and from <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$256\mu \text{W}$ </tex-math></inline-formula> to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$621\mu \text{W}$ </tex-math></inline-formula> , respectively. In addition, the fluctuations of center wavelength and laser power are < 0.5 nm and < 0.5 dB respectively within a duration of 1 hour.

High polarization extinction ratio (PER) in-fiber polarizers are essential in various fiber-based technologies. In this letter, we propose and demonstrate an in-fiber dispersion compensated polarizer (DCP) based on integrated fiber gratings, which is fabricated by a UV-inscribed 45° tilted fiber grating (TFG) and a chirped fiber Bragg grating (CFBG) in series. Such compact device could enhance the PER of 45° TFG with nearly double value and it is potential to achieve ultra-high PER with relatively short length and simple fabrication. Meanwhile, DCP could also function as a dispersion management component. Finally, with the integrated grating device, we have demonstrated an all fiber mode-locked laser system, generating soliton pulses at the normal and anomalous dispersion regime, respectively.

We have proposed and experimentally demonstrated an ultrasensitive all-fiber angular displacement sensor based on in-fiber polarizing gratings and half waveplate (IFHWP), in which the polarizing gratings are based on 45°-tilted fiber gratings (45°-TFGs) and the IFHWP is constructed by bending-induced birefringence in single mode fiber (SMF). Compared with the existing angular displacement sensors, the structure of our proposed sensor is more desirable to bring the prominent advantages of all-fiber structure, low transmission loss and high sensitivity. The experimental results show that the proposed angular displacement sensor has a sensitivity and a resolution up to 20.477 dB/rad and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.8\times 10^{-3\circ }$ </tex-math></inline-formula> , respectively, within a large measurement range of about 25°. In addition, such sensor also has very low temperature sensitivity around <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.1\times 10^{-4}$ </tex-math></inline-formula> dB/°C.

OBJECTIVE: To evaluate the method, safety and short-term efficacy of ultrasound-guided percutaneous laser ablation (PLA) for benign solid thyroid nodule (BSTN). METHODS: The treatment group consisting of 12 patients with single BSTN were treated with ultrasound-guided PLA. After treatment, the size and blood flow signals in conventional ultrasonography, the ablation extent of lesions in contrast-enhanced ultrasonography (CEUS), and the related complications and thyroid function were assessed in comparison with the the baseline. A control group including 12 untreated patients with single BSTN was followed-up in the same manner as in the treatment group. RESULTS: In the treatment group, all the 12 patients completed the treatment successfully. During the follow-up, the volume of the nodules was reduced gradually (P<0.05), and blood flow signals in the nodules disappeared. Eleven nodules were non-enhanced in CEUS immediately after the treatment, and the complete ablation rate was 91.7%. During the operation, 3 patients complained of intolerable pain, which was ameliorated or totally relieved after appropriate treatment. The thyroid function showed no significant changes after the treatment (P>0.05). The control group followed up for 6 months showed no significant changes in the nodule volume or thyroid function in comparison with the baseline (P>0.05). CONCLUSION: Ultrasound-guided PLA is a safe and effective minimally invasive treatment of BSTN without obvious adverse effect on thyroid function.