Biomedical subjects

Shiquan Yang

Publications and source records attributed to Shiquan Yang.

5 recordsLinked to original sources

PubMed2006

Effect of Brillouin slow light on distributed Brillouin fiber sensors.

The effect of Brillouin slow light on distributed Brillouin fiber sensors (DBFSs) is studied. We demonstrate Brillouin slow light for a 1.2 ns pulse with peak powers (PS) from 3.3 to 56.2 mW on depletion of the pump power (PP) ranging from 1.3 to 83.2 mW in conventional optical fibers (SMF-28). Experiments show that, when pump power depletion is not negligible, for a given PP the Brillouin gain and delay time of a pulse decrease when PS increases in a long (> or =10 km) sensing fiber. The optimum pump beam depletion resulting from strong interaction of the pump and the probe in the fiber provides accurate temperature and strain information at a high spatial resolution. Our study reveals that at low PP the spatial resolution error caused by the pulse delay for a DBFS with centimeter spatial resolution is less than 5% of the pulse length.

Journal Article↗

PubMed2006

Picosecond-pulse wavelength conversion based on cascaded second-harmonic generation-difference frequency generation in a periodically poled lithium niobate waveguide.

The wavelength conversion of picosecond optical pulses based on the cascaded second-harmonic generation-difference-frequency generation process in a MgO-doped periodically poled lithium niobate waveguide is studied both experimentally and theoretically. In the experiments, the picosecond pulses are generated from a 40 GHz mode-locked fiber laser and two tunable filters, with which the lasing wavelength can be tuned from 1530 to 1570 nm, and the pulse width can be tuned from 2 to 7 ps. New-frequency pulses, i.e., converted pulses, are generated when the picosecond pulse train and a cw wave interact in the waveguide. The conversion characteristics are systematically investigated when the pulsed and cw waves are alternatively taken as the pump at the quasi-phase-matching wavelength of the device. In particular, the conversion dependences on input pulse width, average power, and pump wavelength are examined quantitatively. Based on the temporal and spectral characteristics of wavelength conversion, a comprehensive analysis on conversion efficiency is presented. The simulation results are in good agreement with the measured data.

Journal Article↗

PubMed2006

Development and performance comparison of two different approaches for stabilizing a harmonic mode-locked fiber laser at 40 GHz.

What we believe to be a new and simple approach was developed for stabilizing a harmonic mode-locked fiber laser at 40 GHz. It uses a computer to tune the modulation frequency in a 100 kHz band near 40 GHz to follow variations in the length of the optical cavity. A second approach was also developed to compare with the new approach and to draw conclusions on its performance. Results for the pulse characteristics, side-mode suppression ratio, and timing jitter show that both approaches provide an efficient way of stabilizing a harmonic FM mode-locked fiber laser.

Journal Article↗

PubMed2006

Generating a high-extinction-ratio pulse from a phase-modulated optical signal with a dispersion-imbalanced nonlinear loop mirror.

We demonstrate a method for generating ultrashort pulses from a phase-modulated optical signal by using a dispersion-imbalanced nonlinear loop mirror instead of the traditional linear dispersion medium. The extinction ratio of the pulses is greatly improved at the same time. By controlling the bandwidth of the phase-modulated signal and the dispersion map of the dispersion-imbalanced nonlinear loop mirror, we can control the pulse width from several picoseconds to hundreds of femtoseconds.

Journal Article↗

PubMed2004

[Follow-up surveying the clinical effects after the endoscopic sinus surgery].

OBJECTIVE: To explore the follow-up time and the effect of intranasal glucocorticoid for chronic sinusitis and nasal polyps after endoscopic sinus surgery. METHOD: After the endoscopic sinus surgery, 30 cases of sinusitis and nasal polyps accepted the postsurgical care for the cavity, sinus washing, and intranasal local glucocorticoid rhinocort, then the clinical effects was follow-up surveyed. RESULT: Intranasal local glucocorticoid could evidently reduce the courses of dry and the epithelial metaplasia of nasal cavity and sinus. CONCLUSION: After the endoscopic sinus surgery, follow-up of endoscopic sinus, postsurgical care for the cavity and intranasal local glucocorticoid played equally important roles in treating sinusitis and nasal polyps.

Adolescent↗