We report an erbium-doped fiber laser passively Q-switched by a few-layer molybdenum disulfide（MoS2） saturable absorber（SA）.The few-layer MoS2 is grown by the chemical vapor deposition method and transferred onto the end-face of a fiber connector to form a fiber-compatible MoS2 SA.The laser cavity is constructed by using a three-port optical circulator and a fiber Bragg grating（FBG） as the two end-mirrors.Stable Q-switched pulses are obtained with a pulse duration of 1.92 μs at 1560.5 nm.By increasing the pump power from 42 to 204 mW,the pulse repetition rate can be widely changed from 28.6 to 114.8 kHz.Passive Q-switching operations with discrete lasing wavelengths ranging from 1529.8 to 1570.1 nm are also investigated by using FBGs with different central wavelengths.This work demonstrates that few-layer MoS2 can serve as a promising SA for wideband-tunable Q-switching laser operation.
Handing XiaHeping LiChangyong LanChun LiJinbo DuShangjian ZhangYong Liu
Passive harmonic mode locking of an erbium-doped fiber laser based on few-layer molybdenum disulfide(MoS2)saturable absorber(SA) is demonstrated. The few-layer MoS2 is prepared by the chemical vapor deposition(CVD) method and then transferred onto the end face of a fiber connector to form a fiber-compatible Mo S2SA. The 20 th harmonic modelocked pulses at 216-MHz repetition rate are stably generated with a pulse duration of 1.42 ps and side-mode suppression ratio(SMSR) of 36.1dB. The results confirm that few-layer MoS2 can serve as an effective SA for mode-locked fiber lasers.
A novel method for accurately measuring chromatic dispersion of optical fibers is proposed based on the use of chirped intensity-modulated signals.Unlike the conventional method,the proposed method utilizes the configurable transfer function of optical fibers caused by the residual chirp of intensity modulation,which not only eliminates the chirp error but also improves the measurement range through adjusting the chirp parameter of the intensity modulator.Our method is applicable for measuring both the magnitude and sign of chromatic dispersion of optical fibers or other dispersive devices at different operating wavelengths by using a vector network analyzer.
Shangjian ZhangXinhai ZouHeng WangYali ZhangHeping LiYong Liu
Gapless linear energy dispersion of graphene endows it with unique nonlinear optical properties, including broadband nonlinear absorption and giant nonlinear refractive index. Herein, we experimentally observed that fewlayers graphene has obvious nonlinear absorption and large nonlinear refraction, as investigated by the Z-scan technique in the mid-infrared（mid-IR） regime. Our study may not only, for the first time to our knowledge, verify the giant nonlinear refractive index of graphene(～10-7cm2∕W) at the mid-IR, which is 7 orders of magnitude larger than other conventional bulk materials, but also provide some new insights for graphene-based mid-IR photonics,potentially leading to the emergence of several new conceptual mid-IR optoelectronics devices.
This paper presents a brief review of photonic analog-to-digital converters(ADCs).Some typical schemes and operation principles of photonic ADCs,including photonic sampling ADCs,photonic quantizing ADCs,photonic sampling&quantizing ADCs and photonic assisted ADCs,are summarized and analyzed.In addition,some recent breakthrough results in the photonic ADCs are introduced.
A novel two-stage spectral compression structure which employs a logarithmic dispersion increasing fiber （DIF） in- terconnected with a highly nonlinear linear fiber-nonlinear optical loop mirror （HNLF-NOLM） is proposed and dem- onstrated by numerical simulation. The numerical simulation is implemented by solving the generalized nonlinear SchrOdinger equation using split-step Fourier method, where the soliton number is in the range of 0.5≤N≤1.4. The re- suits show that the spectra are well-compressed and low-pedestal, and the maximum spectral compression ratio （SCR） can reach 10.93 when N=l.4.
We propose a new method for characterizing optical phase modulators based on phase modulation-to-intensity modulation (PM-to-IM) conversion in dispersive fibers.The fiber dispersion spectrally alters the relative phasing of the phase-modulated signal and leads to the PM-to-IM conversion,which is extended to measure the modulation efficiency of optical phase modulators.In the demonstration,the frequency-dependent modulation index and half-wave voltage are experimentally measured for a commercial phase modulator.Compared with conventional methods,the proposed method works without the restriction of small-signal operations,and allows swept-frequency measurement with high resolution and accuracy by using a vector network analyzer.
We experimentally demonstrate that a high-power 0.1-THz continuous wave can be generated by external modulation. A low-noise electrical amplifier and a W-band antenna with a gain of 25 dBi are employed to enhance photodiode output power. Detection power exceeds 1 mW when an absolute terahertz power meter is used.
