Continuous-Wave Single Wavelength Or Multi-Wavelength Ring-Cavity Fiber Laser Based On Semiconductor Optical Amplifier

Fiber lasers have many outstanding advantages,such as ideal beam quality,ultra-high conversion efficiency,high stability and small volume.They have been widely used in optical communication systems,fiber sensor networks,spectroscopy and optical information processing.Recently,semiconductor optical amplifiers(SOA)have attracted much attention due to their small size,light weight,low power consumption and easy integration with other optical components.Fiber lasers based on semiconductor optical amplifier have gradually become the focus of research groups.Inthis paper,we research the continuous-wave single wavelength or multi-wavelength ring-cavity fiber laser based on semiconductor optical amplifier and the compression of oscillating mode number by a SESAM.The main contents are outlined as follows:1、The spontaneous emission characteristics of InP/InGaAsP multiple quantum wells semiconductor optical amplifiers under different injection currents are studied.At a certain injection current and operating temperature,the spontaneous emission linear function of InP/InGaAsP multiple quantum wells semiconductor optical amplifiers can be described by Gaussian function.When the injection current increases gradually,the peak power of spontaneous emission gradually reaches saturation,which is caused by the gain saturation.At the same time,the central wavelength moves to the shortwave direction with the increase of the injection current.When the injection current is increased from 50 mA to 350 mA,the central wavelength shifts from 1568.6 nm to1540.75 nm,bandwidth from 49.2 nm to 82.5 nm,which is due to the enhancement of spontaneous emission effect and temperature characteristics of InP/InGaAsP multiple quantum well semiconductor laser.2、The compression of InP/InGaAsP multiple quantum well semiconductor optical amplifiers spontaneous emission by semiconductor saturable absorber mirror(SESAM)is proposed.When the injection current of the semiconductor optical amplifier is 100 mA,150 mA,200 mA,250 mA and 300 mA,the compression bandwidth is 1.22 nm,3.2 nm,4.85 nm,5.97 nm and 6.9 nm,respectively.Ina laser system with InP/InGaAsP multiple quantum well semiconductor optical amplifiers as gain medium,the compression effect of SESAM may reduce the number of oscillating mode number of the system.3、A fiber ring-cavity laser based on InP/InGaAsP multiple quantum well semiconductor optical amplifier is proposed and experimentally studied.The laser uses InP/InGaAsP multiple quantum well semiconductor optical amplifier as gain mediumand fiber Bragg grating as wavelength selector.When the fiber Bragg grating operates at23℃,and the injection current of the semiconductor optical amplifier is 100 mA,a central wavelength at 1549.66 nm lasing with the average output power of-5 d Bm and signal-to-noise ratio of 45 d B.The threshold current of the laser is 78 mA.When the temperature of fiber Bragg grating increases from 8 ℃ to 28 ℃,the laser output center wavelength increases from 1549.27 nm to 1549.59 nm,drift only 0.32 nm,which indicates that the laser has good temperature stability.4、A novel dual-wavelength continuous-wave ring-cavity fiber laser based on InP/InGaAsP multiple quantum well semiconductor optical amplifier is proposed and experimentally studied.The structure uses InP/InGaAsP multiple quantum well semiconductor optical amplifiers as gain medium and two intracavity cascaded controlled temperature identical fiber Bragg gratings(FBG1 and FBG2)as wavelength selectors.When the injection current of the semiconductor optical amplifier is 120 mA,FBG1 and the FBG2 is working at 5 ℃ and 25 ℃,the dual wavelengths of 1549.56 nm and 1549.18 nm with signal-to-noise ratio of >45 d B are observed.Tunable dual-wavelength can be achieved by adjusting the temperature of FBG1,and the tunable range is 0.6 nm.The generation of microwave signal is simulated by Optisystem software,and the adjustable microwave signal with the frequency range of 22.5 GHz ～74.9 GHz is obtained.The temperature variation coefficient is about 2.10 GHz/℃.Finally,two external-cavity injection lasers with a temperature coefficient of 0.106nm/℃ and 0.108 nm/℃ are used to obtain a tunable ring-shaped cavity laser,and when the working temperature difference of the two injected DFB lasers is changed from 5℃to 25℃,the wavelength interval can be tuned between 0.68 and 2.95 nm.5、The effect of SESAM on continuous-wave multi-wavelength fiber ring-cavity laser with semiconductor optical amplifier is experimentally demonstrated.Inthe case without SESAM,when the injection current of SOA is below 115 mA,a dual-wavelength lasing at 1573.81 nm and 1578.09 nm with a side-mode ratio of ～30d B is achieved.When the injection current of SOA is increased up to ～115 mA,the third mode at 1582.37 nm starts oscillation,a stable triple-wavelength lasing at 1573.81 nm,1578.09 nm and 1582.37 nm is obtained.Inthe case with SESAM,a stable dual-wavelength lasing at 1560.91 nm and 1564.12 nm is achieved because of the compression of oscillating mode number by a SESAM.