Offset quantum-well method for tunable distributed Bragg reflector lasers and electro-absorption modulated distributed feedback lasers

Tunable distributed Bragg reflector (DBR) lasers are essential components for future optical fiber communi- cation systems[1]. A tunable laser can replace a large number of distributed feedback (DFB) lasers as sparing source in wavelength division multiplexing (WDM) sys- tems. Moreover they allow flexible switching and routing for distributed data in future network[2]. There are several methods for integrating gain sec- tion with DBR section, such as butt-joint method, bundle method, and …     

GaAs distributed Bragg reflector lasers

An equivalent cavity approach is used to derive the oscillation condition of a distributed Bragg reflector laser. The oscillation frequencies and thresholds are determined graphically. The effect of lossy reflectors is discussed. Several advantages and potential applications of distributed Bragg reflector structures are pointed out. Experimental results on optically pumped GaAs lasers are presented.     

Solgel grating waveguides for distributed Bragg reflector lasers

Solgel grating waveguides and their application to the fabrication of external-cavity distributed Bragg reflector (DBR) lasers are demonstrated. A new composition of aluminosilicate material is developed for the fabrication of single-mode waveguides and Bragg reflectors. An average loss of <0.2 dB/cm is measured in the single-mode waveguides at 1550 nm. The reflectors show filtering greater than 97% near 1530 nm, with a bandwidth of ~0.6 nm . The Bragg reflectors are used as feedback resonators for DBR lasers. Single-mode lasing with a sidemode suppression of better than 25 dB is demonstrated.     

Analysis of the relative intensity noise behaviour in tunable two- and three-section distributed Bragg reflector lasers

A theoretical analysis is made of the relative intensity noise (RIN) in tunable two- and three-section distributed Bragg reflector (DBR) lasers by taking into account the actual frequency dependence of the Bragg reflector. The RIN is shown to depend significantly on the tuning current, especially at low frequencies and for low and moderate values of the grating coupling coefficient. For high values of this coefficient the dependence is insignificant when the tuning is performed through the DBR section, in accordance with the experimental results recently reported. The RIN spectrum is more significantly affected, however, when the phase control current in the three-section device is used for tuning.     

Transmission matrix modelling of sampled-grating distributed Bragg reflector lasers

The transmission matrix model (TMM) has been used to simulate the tuning behaviour of a sampled-grating distributed Bragg reflector (SG-DBR) laser for the first time, to the best of our knowledge. The model is able to describe all details of the spontaneous emission spectrum below threshold and yields results in good qualitative agreement with experiment.     

Improving the modulation efficiency of high-power distributed Bragg reflector tapered diode lasers

Different measures to improve the modulation efficiency of a distributed Bragg reflector tapered diode laser emitting at 1060 nm were investigated. Due to the 6-mm long cavity, the device reached an output power of 10 W with a nearly diffraction-limited beam quality. The input currents to the ridge-waveguide (RW) and tapered gain-region sections can be independently controlled. This allows a low-current modulation of the optical output power in the Watt range. Under optimized quasi-static conditions the power could be modulated between 0.2 and 3.1 W (4.8 W) by a variation of the RW current between 0 and 50 mA (350 mA). Due to the integrated 6th order surface Bragg grating the emission wavelength remains within the spectral range of 80 pm.     

Spatial and spectral filtering of tapered lasers by using tapered distributed Bragg reflector grating

A 1040 nm tapered laser with tapered distributed Bragg reflector (DBR) grating is designed and fabricated. By designing the grating with tapered layout, the tapered DBR grating exhibits the scattering effect on side backward-traveling waves, thus achieving additional suppression of parasitic oscillation. Under the suppression of parasitic oscillation, the spatial and spectral characteristics of the tapered laser are improved. The experimental results show that a near-Gaussian far-field distribution and a kink-free P-I characteristics are achieved, and a single peak emission with a wavelength of 1046.84 nm and a linewidth of 56 pm is obtained.     

Fabrication of an electro-absorption modulated distributed feedback laser by quantum well intermixing with etching ion-implantation buffer layer

We report the fabrication details of a monolithically integrated electro-absorption modulated distributed feedback laser(EML) based on the ion-implantation induced quantum well intermixing(QWI) technique.To well-preserve material quality in the laser region, thermal-oxide Si O2 is deposited before implantation and the ion-implantation buffer layer is etched before annealing. Thirteen pairs quantum well and barrier are employed to compensate deterioration of the modulator's extinction ratio(ER) caused by the QWI process.The fabricated EML exhibits an 18 d B static ER at 5 V reverse bias. The 3 d B small signal modulation bandwidth of modulator is over 13.5 GHz indicating that this EML is a suitable light source for over 16 Gb/s optical transmission links.     

C-band continuously tunable lasers using tunable fiber Bragg gratings

We report the development of a ring tunable fiber laser based on tunable fiber Bragg gratings (TFBG) integrated with an optical circulator. The TFBG is embedded inside a 3-piont bending device for wavelength tuning. The tunable laser operating in the C-band has power variation, tuning resolution, tuning range and laser line width of ±0.5 dB, 0.5 nm, 25.0 nm and less than 0.05 nm, respectively. As 40 mW of pump power is used, the ring tunable laser has a side mode suppression ratio of 60 dB and a power conversion efficiency of 25%. These specifications ensure the high-quality operation of a tunable laser.     

Demonstration of a widely tunable digital supermode distributed Bragg reflector laser as a versatile source for near-infrared spectroscopy

In this paper we report the characterization of a novel, widely tunable, diode laser source operating over the full telecom L-band (1563–1613 nm), namely the digital supermode distributed Bragg reflector (DS-DBR) laser, and its application to multi-wavelength gas sensing via absorption strategies. The spectroscopic performance of the laser has been assessed by investigating the ro-vibrational spectrum of CO₂, and wavelength modulation spectroscopy was accomplished for proof-of-principle sensitive measurements in discrete spectral regions.     

Shielded method for fabricating the long-length phase-shifted distributed feedback fiber lasers

The successful fabrication of phase-shifted distributed feedback (DFB) fiber lasers is very difficult for a long time. The paper introduced the shielded method for fabricating the long-length phase-shifted DFB fiber lasers. The method is simple, convenient, effective and efficient for it can be finished one-off.     

Raman fiber distributed feedback lasers

We demonstrate fiber distributed feedback (DFB) lasers using Raman gain in two germanosilicate fibers. Our DFB cavities were 124 mm uniform fiber Bragg gratings with a π phase shift offset from the grating center. Our pump was at 1480 nm and the DFB lasers operated on a single longitudinal mode near 1584 nm. In a commercial Raman gain fiber, the maximum output power, linewidth, and threshold were 150 mW, 7.5 MHz, and 39 W, respectively. In a commercial highly nonlinear fiber, these figures improved to 350 mW, 4 MHz, and 4.3 W, respectively. In both lasers, more than 75% of pump power was transmitted, allowing for the possibility of substantial amplification in subsequent Raman gain fiber.     

Random distributed feedback fibre lasers

The concept of random lasers exploiting multiple scattering of photons in an amplifying disordered medium in order to generate coherent light without a traditional laser resonator has attracted a great deal of attention in recent years. This research area lies at the interface of the fundamental theory of disordered systems and laser science. The idea was originally proposed in the context of astrophysics in the 1960s by V.S. Letokhov, who studied scattering with “negative absorption” of the interstellar molecular clouds. Research on random lasers has since developed into a mature experimental and theoretical field. A simple design of such lasers would be promising for potential applications. However, in traditional random lasers the properties of the output radiation are typically characterized by complex features in the spatial, spectral and time domains, making them less attractive than standard laser systems in terms of practical applications. Recently, an interesting and novel type of one-dimensional random laser that operates in a conventional telecommunication fibre without any pre-designed resonator mirrors–random distributed feedback fibre laser–was demonstrated. The positive feedback required for laser generation in random fibre lasers is provided by the Rayleigh scattering from the inhomogeneities of the refractive index that are naturally present in silica glass. In the proposed laser concept, the randomly backscattered light is amplified through the Raman effect, providing distributed gain over distances up to 100 km. Although an effective reflection due to the Rayleigh scattering is extremely small (∼0.1%), the lasing threshold may be exceeded when a sufficiently large distributed Raman gain is provided. Such a random distributed feedback fibre laser has a number of interesting and attractive features. The fibre waveguide geometry provides transverse confinement, and effectively one-dimensional random distributed feedback leads to the generation of a stationary near-Gaussian beam with a narrow spectrum. A random distributed feedback fibre laser has efficiency and performance that are comparable to and even exceed those of similar conventional fibre lasers. The key features of the generated radiation of random distributed feedback fibre lasers include: a stationary narrow-band continuous modeless spectrum that is free of mode competition, nonlinear power broadening, and an output beam with a Gaussian profile in the fundamental transverse mode (generated both in single mode and multi-mode fibres).     

Tunable fiber Bragg gratings for application in tunable fiber lasers

The resonance wavelength of the fiber Bragg gratings (FBGs) is tuned using two methods. Tunable FBGs are used as the selecting elements in the cavities of tunable lasers. An ytterbium-doped fiber laser with a wavelength tuning range of 1063–1108 nm and an output power of 6 W, a Raman fiber laser with a wavelength tuning range of 1252–1303 nm and an output power of 3 W, and an erbium-doped fiber laser with a wavelength tuning range of 1530–1580 nm are realized, and their characteristics are studied.     

Realization of a distributed Bragg reflector for propagating guided matter waves

We report on the experimental study of a Bragg reflector for guided, propagating Bose-Einstein condensates. A one-dimensional attractive optical lattice of finite length created by red-detuned laser beams selectively reflects some velocity components of the incident matter wave packet. We find quantitative agreement between the experimental data and one-dimensional numerical simulations and show that the Gaussian envelope of the optical lattice has a major influence on the properties of the reflector. In particular, it gives rise to multiple reflections of the wave packet between two symmetric locations where Bragg reflection occurs. Our results are a further step towards integrated atom-optics setups for quasi-cw matter waves.     

Long-external-cavity distributed Bragg reflector laser with subkilohertz intrinsic linewidth

We report on a simple, compact, and robust 780 nm distributed Bragg reflector laser with subkilohertz intrinsic linewidth. An external cavity with optical path length of 3.6 m, implemented with an optical fiber, reduces the laser frequency noise by several orders of magnitude. At frequencies above 100 kHz the frequency noise spectral density is reduced by over 33 dB, resulting in an intrinsic Lorentzian linewidth of 300 Hz. The remaining low-frequency noise is easily removed by stabilization to an external reference cavity. We further characterize the influence of feedback power and current variation on the intrinsic linewidth. The system is suitable for experiments requiring a tunable laser with narrow linewidth and low high-frequency noise, such as coherent optical communication, optical clocks, and cavity QED experiments.     

具有内部相移的分布反馈半导体激光器电路模型

以耦合波方程为基础,经过适当的近似处理,给出一个比较简单的适用于有内部相移的单模分布反馈半导体激光器电路模型。该模型可用于直流、交流和瞬态分析。适于在开发光电集成回路电路级模拟软件中采用,亦可加入到现有电路模拟软件中。     

Relaxation oscillations in distributed feedback lasers

Using approximate solutions for over-coupled (KL > 1) distributed feedback lasers above threshold and a small-signal perturbation analysis, the frequency and damping of DFL relaxation oscillations are calculated.     

Two-photon-pumped distributed feedback zirconia waveguide lasers

Distributed feedback laser action of narrow line-width output was demonstrated in zirconia waveguides doped with trans-4-[p-(N-hydroxyethyl-N-methylamino) styryl]-N-methylpyridinium p-toluene sulfonate, a compound of strong two-photon up-converted emission near 620 nm. Single-beam pumping at 1.06 m led to intense up-converted amplified spontaneous emission at 620 nm. Transient gratings for coherent scattering were generated in the waveguides by crossing two 1.06-m beams. Narrow line-width distributed feedback laser emission was observed at 627 nm. PACS 42.55.Mv; 42.70.Jk; 42.79.Gn     

Low-loss 1.3-microm GaInNAs saturable Bragg reflector for high-power picosecond neodymium lasers

A novel low-loss, single-step-growth 1.3-microm GaInNAs saturable Bragg reflector mode-locking element has been developed. Combined radial thickness and postgrowth annealing control have permitted a tuning range of 46 nm for passive mode locking to be demonstrated from one wafer. With this structure, stabilized mode locking was obtained from quasi-cw diode-pumped Nd:YLF and Nd:YALO lasers operating at 1314 and 1342 nm, respectively, with average on-time output powers of as much as 20 W and pulse durations as low as 22 ps.