Mode beating noise reduction of mutually injection-locked erbium-doped fiber laser and laser diode link

We report a mutually injection-locked erbium-doped fiber amplifier (or laser) and Fabry-Pe/spl acute/rot laser diode link (EDFA-FPLD or EDFL-FPLD) for single longitudinal mode lasing with linewidth of 0.012 nm and sidemode suppression ratio of 42 dB. The 3-dB linewidths of <20 MHz and 350 kHz for the EDFL-FPLD and EDFA-FPLD links, respectively, are reported using interferometric determination. The mode-beating noise can be completely eliminated in the EDFA-FPLD link.     

The effect of side modes with linewidth and intensity fluctuationsin semiconductor lasers

The influence of side modes on the linewidth and intensity fluctuations of the main mode is studied using Monte Carlo techniques. Explicit analytic relations are developed for the side-mode induced linewidth, using impulse responses of the laser obtained from rate equations. It is found that both the absolute level of the main-mode too side-mode power ratio and the passive loss in the side mode influence the main-mode linewidth. A typical 3-mW laser has negligible linewidth enhancement from the side mode if the modal power ratio is about 300/1 (or greater), corresponding to a side-mode loss of 0.2-0.5 dB (or more) for one round trip within the laser resonator. Lower side-mode losses yield an abrupt catastrophic increase in main-mode linewidth     

Linewidth of 1.3?m cleaved-coupled-cavity lasers

The linewidth and side-mode suppression ratio of three variable-gap C3 lasers were measured as a function of output power and drive currents. With feedback carefully eliminated, the narrowest linewidth obtained was 8 MHz at an output power of 13.6 mW. There was little correlation between line-width and suppression ratio.     

Linewidth reduction of cleaved-coupled-cavity lasers by optical feedback from a single-mode polarisation-preserving fibre external cavity

Linewidth characteristics of a cleaved-coupled-cavity laser with a single-mode polarisation-preserving fibre external cavity have been investigated as a function of feedback power level and side-mode suppression ratio. The optimum power feedback ratio is near 2×10?4 for a minimum linewidth of about 30 kHz. A weak dependence of linewidth on side-mode suppression ratio is observed as long as the suppression ratio is greater than 500:1.     

High performance single frequency fiber grating-basederbium/ytterbium-codoped fiber lasers

The device characteristics of Er³⁺,Yb³⁺ single frequency fiber lasers are reported. A 5-cm long 1550-nm distributed feedback fiber laser with 4 mW output power is shown to have excellent specifications in terms of optical linewidth, signal-to-noise ratio (SNR), relative intensity noise, side-mode suppression and polarization purity. For higher power applications, a 1.5 cm single frequency Er³⁺,Yb³⁺ grating-based fiber laser with 60 mW output power and a net efficiency of 12% is demonstrated     

The influence of power level on injection laser linewidth andintensity fluctuations including side-mode contributions

The contribution of side modes to the main-mode line-width is calculated as function of power output using analytic relations and verified using a series of Monte Carlo calculations. For well-behaved lasers having photon lifetimes of 0.88 and 1.57 ps and gain compression of 10% or less, it is found that the total linewidth decreases monotonically with increasing power output. These lasers have main-mode to side-mode ratios in the range 100-300 at 3 mW output; they exhibit side-mode contributions to main-mode linewidth of 17 and 57% respectively at a power level of 10 mW and modal ratios of 940 and 390. When the gain compression exceeds 10% as it may in lasers running at 10 mW or more, the linewidth can reach a minimum and then increase with increasing power level, in accordance with laboratory observation on some lasers     

Very narrow linewidth asymmetric cladding InGaAs-GaAs ridge waveguide distributed Bragg reflector lasers

Asymmetric cladding InGaAs-GaAs ridge waveguide distributed Bragg reflector (RW-DBR) lasers are demonstrated with a spectral linewidth as low as 39 kHz for an output power of 24 mW. The fabrication requires only a single standard epitaxial growth of a laser structure while the use of a thin top cladding layer allows for a shallow reactive ion etch of the distributed Bragg reflector. These RW-DBR lasers have a threshold current of 12.4 mA, a slope of 0.3 W/A, and over 40 dB side-mode suppression at a wavelength of 1010 nm.     

Tunable Fiber Laser Using a Broad-Band Fiber Mirror and a Tunable FBG as Laser-Cavity Ends

By using a broad-band fiber mirror (BFM) and a tunable fiber-Bragg-grating at either end of laser cavity, a wavelength tunable erbium-doped fiber laser is demonstrated. In a forward pump scheme using 100 mW pump power at 1480 nm, stable lasing output power of 21.14-mW measured at 1544.8 nm is obtained with a threshold pump power of 4.7 mW. A side-mode suppression ratio as high as 57.9 dB, wavelength tuning range up to 30 nm with step resolution of 0.2 nm and power variation less than plusmn1.0 dB are achieved. For a backward pump scheme, the BFM acts as a broad-band reflector both for the lasing signal and pump source. The high performance, cost-effective BFM based tunable fiber laser may play an important role in fiber optics communication and fiber sensing applications.     

Single-transverse-mode vertical-cavity lasers under continuous andpulsed operation

Using a hybrid ion implanted/selectively oxidized device structure, we report high-power single-mode operation of an 850-nm vertical-cavity laser. Under continuous-wave operation, >4 mW of single-mode power with 45 dB of side-mode suppression is achieved. The spectral behavior under pulsed modulation is determined to be influenced by thermal lensing. When biased to threshold, single-mode operation with >35-dB side-mode suppression is obtained for large signal modulation     

A widely tunable fiber ring laser with closed loop control based on high-precision stepper motor

A tunable single-longitudinal mode erbium-doped fiber ring laser based on stepper motor and closed loop control is proposed and demonstrated. The system consists of an erbium-doped fiber (EDF), a tunable fiber Bragg grating (FBG) filter and a wavelength detector. The characteristics of output laser, such as output power, power stability and 3-dB linewidth, are investigated in the operation range of 1 531—1 569 nm. The repeated experimental results of the fiber laser show that the 3-dB linewidth is less than 17 ps, the side-mode suppression ratio (SMSR) is up to 60 dB, the output power is up to 1.37 dBm, and the power variation is less than 0.61 dB.     

A widely tunable SOA-integrated DBR laser by combination of sampled and superstructure gratings

We report on the development of the first 30 nm tunable laser diode utilizing a front sampled grating-distributed Bragg reflector (SG-DBR) and a rear superstructure grating DBR (SSG-DBR). A high output power greater than 18 mW was achieved with superior longitudinal mode stability, as well as an overall power variation of less than 3 dB for the well-defined laser. Furthermore, lasers integrated with a semiconductor optical amplifier (SOA) enabled the output power to be controlled independently both by the active current and the SOA current, as well as achieving a maximum output power of 45 mW. The side-mode suppression ratio was in excess of 40 dB for all the 50 GHz spaced wavelength channels.     

Reliable laboratory transmitter with submegahertz linewidth

An external-cavity transmitter configuration is introduced using a semiconductor laser at 1.3 ?m wavelength, a spherical reflector for laser mode selection and a semitransparent Au-coated GRIN-rod lens for linewidth reduction. At 1.45 mW output power a linewidth of 700 kHz and a laser sidemode suppression of 30 dB is achieved.     

Rational harmonic mode-locking of erbium-doped fiber laser at 40 GHz using a loss-modulated Fabry-Pe/spl acute/rot laser diode

Rational harmonic mode-locking of an Erbium-doped fiber ring laser (EDFL) at repetition frequency of 40 GHz is demonstrated by using a purely loss-modulated Fabry-Pe/spl acute/rot laser diode (FPLD) at 1 GHz. The FPLD is neither lasing nor gain-switching, which requires a threshold modulation power of 18 dBm to initiate harmonic mode-locking of the EDFL. After chirp compensation, the nearly transform-limited pulsewidth and spectral linewidth of 3 ps and 1.3 nm are obtained at repetition frequency of 40 GHz, which corresponds to a time-bandwidth product of 0.31. The EDFL gradually evolves from harmonic mode-locking to injection-locking mode as the FPLD changes from loss-modulation to gain-switching mode by increasing its dc driving current.     

A three-electrode distributed Bragg reflector laser with 22 nm wavelength tuning range

A large wavelength tuning range is demonstrated for a three-electrode distributed Bragg reflector (DBR) laser by applying both forward and reverse bias to the passive Bragg section. In the reverse direction the tuning towards longer wavelengths is mainly attributed to electrical heating. By also using the phase tuning section, all wavelengths within a range of 22.1 nm can be reached with a side-mode suppression better than 25 dB and with an output power exceeding 4.4 mW.<>     

Spectral linewidth and resonant frequency characteristics ofInGaAsP/InP multiquantum well lasers

The spectral linewidth and resonant frequency characteristics of 1.3-μm InGaAsP/InP multi-quantum-well lasers grown by liquid-phase epitaxy were investigated and compared to those of the conventional double heterostructure (DH) lasers. A decrease in spectral linewidth and an increase in resonant frequency f_r with decreasing well thickness were observed. Moreover, the linewidth enhancement factor α was reduced to ~2 for well thicknesses of less than ~200 Å, while that of the DH laser was ~6. An f_r of 9 GHz, which is twice as large as that of conventional DH lasers, was achieved at an optical power of 5.3 mW/facet     

Fabrication of a heterodyne receiver OEIC with optimized integration process using three MOVPE growth steps only

An optimized integration process is reported requiring only three epitaxial growth steps for the fabrication of an OEIC encompassing a single-mode laser, a waveguide element, and fast photodiodes. The process was applied to the fabrication of a heterodyne receiver including a semi-insulating buried heterostructure (SIBH)-DFB-laser with an output power of 14 mW and a side-mode suppression ratio greater than 40 dB, a 3-dB coupler, and high-speed balanced photodiodes with a bandwidth of 9 GHz. The laser can also be used as a transmitter laser exhibiting a modulation bandwidth of 11 GHz.     

The semiconductor laser linewidth due to the presence of side modes

The laser linewidth is evaluated by solving the rate equations for a nearly single-mode laser with two modes. The resulting linewidth contribution due to the presence of side modes is introduced by the nonlinear gain in the laser diode. For weak side modes, the linewidth contribution is proportional to the third power of the side mode intensity. A linewidth contribution of about 20 MHz for a side-mode power of 100 μW has been found experimentally for a 1.3-μm buried-heterostructure laser     

1.5 Gbit/s FSK transmission system using two-electrode Fabry-Perot buried heterostructure laser

The performance of a tunable two-electrode FP laser has been studied experimentally. An FSK transmission system up to 1.5 Gbit/s has been demonstrated using this laser. This new laser showed single longitudinal mode (20 dB side-mode suppression) lasing at different wavelengths through a range of 6.5 nm and minimum spectral linewidth of 30 MHz.<>     

InGaAsSb-AlGaAsSb distributed-feedback lasers emitting at 1.72μm

We have developed distributed-feedback ridge waveguide lasers based on AlGa(In)AsSb emitting at 1.72 μm. The distributed feedback is obtained by first-order Cr-Bragg gratings defined on both sides of the laser ridge. The threshold current under pulsed operation at room temperature was around 180 mA and an output power of 1.5 mW was obtained. The gratings lead to a side-mode suppression ratio of 27 dB     

单频分布布拉格反射光纤激光器及温度传感实验研究

报道利用Er∶Yb双掺杂光纤制作的单频窄线宽分布布拉格反射 (DBR)光纤激光器。在 980nm半导体激光器抽运下 ,当抽运功率为 75mW时 ,获得了输出功率为 2 3mW的单频激光 ,其中心波长为 1 5 5 7 5 2 4nm ,线宽小于 5MHz。利用制作的单频DBR光纤激光器构成光纤有源传感系统 ,进行温度传感实验研究 ,实验结果线性度很好 ,高信噪比和高输出功率使得该系统具有波长易于检测的优点