Stable single longitudinal mode erbium-doped silica fiber laser based on an asymmetric linear three-cavity structure

We present a stable linear-cavity single longitudinal mode （SLM） erbium-doped silica fiber laser. It consists of four fiber Bragg gratings （FBGs） directly written in a section of photosensitive erbium-doped fiber （EDF） to form an asymmetric three-cavity structure. The stable SLM operation at a wavelength of 1545.112 nm with a 3-dB bandwidth of 0.012 nm and an optical signal-to-noise ratio （OSNR） of about 60 dB is verified experimentally. Under laboratory conditions, the performance of a power fluctuation of less than 0.05 dB observed from the power meter for 6 h and a wavelength variation of less than 0.01 nm obtained from the optical spectrum analyzer （OSA） for about 1.5 h are demonstrated. The gain fiber length is no longer limited to only several centimeters for SLM operation because of the excellent mode-selecting ability of the asymmetric three-cavity structure. The proposed scheme provides a simple and cost-effective approach to realizing a stable SLM fiber laser.

Ground-state cooling based on a three-cavity optomechanical system in the unresolved-sideband regime

In the unresolved sideband regime,we propose a scheme for cooling mechanical resonator close to its ground state in a three-cavity optomechanical system,where the auxiliary cavities are indirectly connected with the mechanical resonator through standard optomechanical subsystem.The standard optomechanical subsystem is driven by a strong pump laser field.With the help of the auxiliary cavities,the heating process is suppressed and the cooling process of the mechanical resonator is enhanced.More importantly,the average phonon number is much less than 1 in a larger range.This means that the mechanical resonator can be cooled down to its ground state.All these interesting features will significantly promote the physical realization of quantum effects in multi-cavity optomechanical systems.

Theoretical and experimental researches on C-band three-cavity transit-time effect oscillator

The C-band three-cavity transit-time effect oscillator (3C TTTO) is a novel high power microwave device based on the transit-time effect of the three-cavity (3C) resonator. The operational principle of this device is briefly expounded in this paper, and the theoretical and experimental researches on the radial insulation diode, the 3C resonator, the double-gap output cavity and the circular waveguide bevel cut radiation antenna are presented in detail. By using the analytic method, the eigen modes and their field distributions of the 3C resonator are developed, and some basic laws of the transit-time effect are obtained in non-π mode field of the 3C resonator. At last, the experimental results are given. This device generated RF peak power in excess of 400MW with 15ns FWHM, and its beam-wave power conversion efficiency is about 17%.

Three-cavity clearance(TCC)can decrease the fistula rate after drainage of a perianal abscess:a case–control study

Objective:The aim of this study was to evaluate the safety and efficacy of three-cavity clearance(TCC)used for the treatment of perianal abscess.Methods:A case–control study of patients with perianal abscess was conducted at the Second and Third Affiliated Hospitals of Nanjing University of Chinese Medicine from June 2013 to March 2016.Clinical data from 46 patients who had TCC were analysed.At the same time,46 patients had simple incision and drainage and 46 patients had abscess drainage and cutting seton(radical abscess incision);the data from these patients were also analysed.The length of hospital stay,time of wound healing,fistula rate and anal incontinence were assessed.Results:The rate of fistula formation in the TCC group was 13.0%—significantly lower than that in the group with simple incision and drainage(39.1%,p<0.01)and similar to the group with radical abscess incision(8.7%,p>0.05).Two patients(4.3%)in the group with radical abscess incision had anal incontinence,flatus and soiling;their Wexner scores were 6 and 3,respectively.There was no anal incontinence in the TCC group or the simple incision and drainage group.There were no statistical differences in the time of wound healing and length of hospital stay among the three groups(both p>0.05).Conclusion:TCC is a safe and effective sphincter-preserving procedure for perianal abscess formation and can decrease the fistula rate after perianal abscess drainage.It appears to be a valuable method that can be used in clinical practice;however,further studies are needed to verify this finding.