A tunable distributed amplification DFB laser diode (TDA-DFB-LD)

A novel wavelength-tunable distributed amplification distributed feedback laser diode (TDA-DFB-LD) is proposed and fabricated. The proposed structure provides synchronous change between the longitudinal mode and the Bragg wavelength in tuning; thereby continuous wavelength tuning can be realized with single control-current. Moreover, extended tuning is also possible with two control-currents. A continuous tuning range of 2.9 nm and an extended discrete tuning range of 15 nm are experimentally obtained with a 1.55-μm TDA-DFB-LD     

1064-nm DFB laser diode modules applicable to seeder for pulse-on-demand fiber laser systems

Semiconductor DFB (Distributed feedback) laser diodes with an operating wavelength of 1064 nm, which is suitable for pulse-on-demand fiber laser, have been developed. The stable performance of CW and nanosecond/picosecond pulsed operation is reviewed. By applying gain-switching operation with a simple direct modulation technique, 50-ps pulse generation with a stable spectral single-mode property was obtained. For the efficient amplification of the obtained 50-ps pulse, a monolithic semiconductor optical amplifier (SOA) was integrated into the DFB lasers. An improved peak power of 300 mW at 50-ps pulse was observed with limited optical noise injection when the synchronous modulation technique of the DFB and the SOA was employed. Short cavity lasers showed a high-frequency response compared to the original DFB lasers and achieved a short pulse width of 13 ps by standard gain-switched operation.     

Realisation of flat FM response by directly modulating a phase tunable DFB laser diode

Flat and efficient FM responses in a wide frequency range were obtained by directly modulating the injection current of a 1.3 ?m phase-tunable DFB-DC-PBH laser diode. The FM response is flat between 1 kHz and 300 MHz, and the nor malised frequency deviation is 1?3 GHz/mA, which is 5?10 times larger than that of a conventional laser diode in the several hundred megahertz region.     

Micromirror device controlled tunable diode laser diode laser

An electronically controlled external cavity laser diode for fast wavelength tuning and multiple-colour lasing is presented. The spectral-tuning is accomplished by a digital micromirror device. Tuning of 47.4 nm with a tuning speed of 0.85 nm/ms was achieved. Simultaneous emission of up to 9 laser lines is demonstrated     

Transmission characteristics of DFB laser modules for analogapplications

Analog transmission characteristics of highly linear 1.3- and 1.55-μm distributed feedback (DFB) laser modules are described. To obtain high-power and high-performance DFB lasers, the bias dependence of distortion characteristics is discussed. The carrier-to-noise ratio, the composite second-order distortion, and the composite triple beat of the DFB laser module which is developed for analog CATV applications are presented. The analog transmission characteristics, such as CNR degradation, after fiber transmission, dispersion-induced distortion, and the influence of reflection, have been made clear. The stable high linearity of the DFB laser also has been confirmed by the composite distortion measurement under an accelerated aging test     

Spice simulation of laser diode modules

For simulating laser diode modules, a subcircuit has been implemented in the SPICE network simulation program. In addition to the properties of the laser chip and electrical package parasitics, incoherent optical reflections from the end of the fibre pigtail are included. Numerical results are compared to measurements on DFB and FP lasers.     

氧化锌单晶DFB半导体激光器的设计与分析

基于严格耦合波理论(RCWA)和介质平板波导理论,针对光通信中的1550 nm波长,设计了一种基于氧化锌(ZnO)单晶的分布反馈式(DFB)半导体激光器的光栅结构,分析了二维电场模式图以及激射波长线宽图,得到了光栅结构的变化对其单纵模传输的影响。仿真结果表明,当光栅的周期为489 nm,占空比为50%,光栅深度为400 nm时,全局电场能量达到了8.3×107 J,光谱线宽小于0.1 。该激光器具有很好的窄线宽输出以及波长选择特性。理论分析与仿真结果基本一致为后期进行该器件的制备提供了较好的参考。     

Analysis of linewidth of separated-electrode DFB laser diode

Presents a new linewidth formula for DFB lasers, which includes the spatial hole burning effect. The linewidth of DFB lasers with three separated electrodes is calculated in various bias conditions. The optimum bias condition is discussed to obtain a narrow linewidth.<>     

Design and analysis of widely tunable sampled grating DFB laser diode integrated with sampled grating distributed Bragg reflector

A new widely tunable laser diode structure that requires only two tuning currents is proposed. The laser diode consists of a sampled grating distributed feedback (SGDFB) laser diode monolithically integrated with a sampled grating distributed Bragg reflector (SGDBR). The phase control sections are properly inserted between the grating bursts of the SGDBR and SGDFB sections for the discrete and continuous tuning. To confirm the feasibility of the new structure, the split-step time domain model is used. The simulation result for a particular design shows that the tuning range as wide as 27 nm is possible with side-mode suppression ratio exceeding 35 dB. Furthermore, the output power is larger than that from SGDBR laser diodes with similar parameters.     

Widely tunable coupled-ring reflector laser diode

A coupled-ring reflector (CRR), which is composed of two coupled rings both of which are coupled with a straight waveguide, is applied to a widely tunable laser diode. When the radii of two rings are slightly different, the peak reflection wavelength of the CRR can be widely tuned over a few tens nanometers by a small amount of refractive index change. It is shown that a few tens nanometers of tuning with a sidemode suppression ratio exceeding 45 dB both for adjacent cavity mode and for adjacent ring mode is achievable in the widely tunable CRR laser diode.     

FMCW-LIDAR with tunable twin-guide laser diode

The realisation of a coherent frequency modulated continuous wave LIDAR used for the accurate measurement of short distances employing a tunable twin-guide laser diode is demonstrated for the first time. A relative accuracy of distance measurement of 4×10^-3 has been achieved at a distance of some centimetres     

Two-channel tunable laser diode based on photonic crystals

We report the development of a tunable laser diode array monolithically integrated with a Y-coupler structure based on photonic crystals. The laser diodes consist of two longitudinally coupled photonic crystal waveguide segments that are separated by a photonic crystal mirror section. Quasicontinuous tuning is achieved in a 30.6-nm window with 100-GHz channel spacing as typically required by wavelength-division-multiplexing applications. The sources can be operated independently allowing the simultaneous transmission of two freely selectable wavelengths.     

The reliability of laser diodes and laser transmitter modules

This paper reviews the reliability of laser transmitter modules for use in optical fibre transmission systems. Methods for reliability testing and lifetime prediction are discussed and the dominant failure mechanisms affecting laser modules are described. The current status of laser module reliability is discussed, based on both published results, and on the findings of a study at BT Laboratories of the reliability of commercial laser modules from ten manufacturers. It is concluded that significant progress has been made in the reliability of laser diodes, through the understanding of basic failure mechanisms, leading to long predicted lifetimes for a number of different laser structures. However, module packaging is less reliable and further work is required to identify and eliminate those materials and processing technologies which lead to the risk of early failure.     

Proposal of electrically tunable external-cavity laser diode

We propose and demonstrate a novel tunable external-cavity laser diode that simultaneously achieves rapid tuning rate and wide tuning range by electrical control. This contains new-type integrated laser diode, collimating lens, and diffraction grating mirror. The integrated laser diode consists of Fabry-Pe/spl acute/rot laser diode and waveguide-type deflector, which can deflect the beam passing through the waveguide. By control of the current in the deflector region, maximum wavelength variation of 8.6 nm and sidemode suppression ratio of >35 dB were obtained.     

A tunable dual-wavelength fiber Bragg grating laser using an external-injected DFB laser

A tunable dual-wavelength fiber Bragg grating (FBG) laser based on a distributed feedback (DFB) laser injection is proposed and experimentally demonstrated. The wavelength spacing can be tuned by adjusting the operation temperature of the DFB laser. When the DFB works at 25 ℃, a dual-wavelength simultaneous oscillation at 1 549.67 nm and 1 553.44 nm with wavelength spacing of 3.77 nm is achieved. Our experimental results demonstrate the new concept of dual-wavelength lasing with a DFB laser injection and the technical feasibility.     

EAM-integrated DFB laser modules with more than 40-GHz bandwidth

Electroabsorption modulator (EAM)-distributed feedback (DFB) modules with record-high bandwidth of 41 GHz have been developed. 40-Gb/s nonreturn to zero (NRZ) operation with 12-dB extinction ratio and -1.6-dBm average output power have been successfully achieved by optimizing the EAM length and detuning. A clearly opened eye diagram was maintained even after 80-km nonzero dispersion shifted fiber (NZ-DSF) transmission with dispersion compensation, 40-GHz short pulse trains with 6-ps pulsewidth have been also generated by sinusoidal electrical modulation     

Broad-band tunable two-section laser diode with external gratingfeedback

A tunable laser light source consisting of a two-section laser diode and an external grating is discussed. A wide tunable range of 154 nm was realized by improving the antireflection (AR) coating and the coupling efficiency. At both edges of the tunable range, however, the tuning characteristics were strongly influenced by the internal mode, in spite of the high-quality AR coating. The effects of the internal mode were avoided by using a phase-control section of the laser. Consequently, single-mode oscillation can be obtained at any desirable wavelength within the above tunable range by controlling the current injected into the phase-control section     

Optical feedback-induced noise in pigtailed laser diode modules

The sensitivity of commercially available pigtailed laser diode modules to optical feedback, in terms of laser relative intensity noise, is investigated. A pigtailed laser diode model which is based on multimode rate equations, Langevin operators, and optical feedback terms in used to predict that operation in the coherence collapse region can be avoided in high-speed, short-haul, optical data links by trading off optical launch power into the pigtail with decreased laser/fiber coupling efficiency. Experimental results for three pigtailed laser diode modules indicate that with a laser/fiber coupling efficiency of 4%, an external feedback level of between -15 and -17 dB can be tolerated before the laser enters the coherence collapse region. Good correlation between these results and predictions from the numerical model is obtained.<>     

A tunable cavity-locked diode laser source for terahertzphotomixing

An all solid-state approach to the precise frequency synthesis and control of widely tunable terahertz radiation by differencing continuous-wave diode lasers at 850 nm is reported in this paper. The difference frequency is synthesized by three fiber-coupled external-cavity laser diodes. Two of the lasers are Pound-Drever-Hall locked to different orders of a Fabry-Perot (FP) cavity, and the third is offset-frequency locked to the second of the cavity-locked lasers using a tunable microwave oscillator. The first cavity-locked laser and the offset-locked laser produce the difference frequency, whose value is accurately determined by the sum of an integer multiple of the free spectral range of the FP cavity and the offset frequency. The dual-frequency 850-nm output of the three laser system is amplified to 500 mW through two-frequency injection seeding of a single semiconductor tapered optical amplifier. As proof of precision frequency synthesis and control of tunability, the difference frequency is converted into a terahertz wave by optical-heterodyne photomixing in low-temperature-grown GaAs and used for the spectroscopy of simple molecules. The 3-dB spectral power bandwidth of the terahertz radiation is routinely observed to be ≲1 MHz. A simple, but highly accurate, method of obtaining an absolute frequency calibration is proposed and an absolute calibration of 10^-7 demonstrated using the known frequencies of carbon monoxide lines between 0.23-1.27 THz     

紧凑型光栅外腔可调谐半导体激光器

研制了一台结构紧凑的窄线宽、可调谐半导体激光器.采用光栅外腔Littrow结构,将光栅和平面反射镜置于同一个旋转平台上,并使光栅衍射平面和平面镜反射平面的交线与平台旋转轴重合,通过旋转平台实现光栅外腔选取单纵模、压窄线宽和波长调谐,并保证输出光的方位不发生改变,同时用棱镜将输出光斑压缩成为类方形.该激光器的尺寸为110 mm×80 mm×35 mm,中心输出波长为653 nm,谱宽0.07 nm,调谐范围4.6 nm,可连续稳定运转4小时以上.