1.5 ?m phase-shifted DFB laser by EBX and mass-transport technique

The phase-shifted DFB laser is fabricated by the electron-beam lithography and mass-transport technique. The reduction of threshold current and facet reflectivity was achieved by a one-step mass-transport process. Low threshold and stable single-mode operation was obtained. The effect of the phase shift was confirmed from the symmetrical subthreshold spectra.     

Analysis of polarization bistability of phase-shifted DFB laser dueto TM light injection

As a method of high-bit-rate optical processing, the TM light injection-induced optical polarization bistability using Fabry-Perot type laser diodes has been experimentally demonstrated and theoretically analyzed. In these studies, although switching times less than 1 ns both for switch-up and switch-down have been reported, both of the TE and TM outputs exhibit longitudinal multimode spectra. In practical processing systems, a dynamically stable operation of the polarization switching is considered to be essential. It is the purpose of this paper to present an analytical study of the TM light injection-induced polarization bistability using a λ/4-shifted distributed feedback (DFB) laser model and to describe the detailed picture of the mechanism     

Wavelength accuracy in distributed phase-shifted DFB lasers

In the wavelength-division-multiplexed transmission framework, we investigate the ability of the distributed phase-shifted distributed-feedback (DFB) structure by enlarging the ridge to fulfil the wavelength accuracy required for array fabrication. Measurements on three different phase-shift geometries indicate that the poor localization of the optical mode along the cavity is detrimental to the wavelength accuracy. This study points out the best solution for DFB structure implementable in arrays, using already validated low-cost and high-throughput technologies in a production environment     

Stability of phase-shifted DFB lasers against hole burning

To study the above-threshold operation of DFB lasers, we have developed a multisection model which we present in detail. We have assessed the sensitivity to hole burning of various strongly coupled DFB lasers and explained their behavior both qualitatively and quantitatively, Good agreement is found with experimental results. It turns out that DFB lasers with a narrow stripe region are more stable than λ/4-shifted DFB lasers     

1.5 ?m phase-shifted DFB lasers for single-mode operation

Fabrication and single-mode laser oscillation were demonstrated for modified DFB lasers where the phase of the corrugations was shifted at the centre by a quarter guided-wavelength and which, in principle, provided a resonance at the Bragg wavelength and stable single-mode oscillation. Phase-shifted corrugations were fabricated using electron-beam lithography.     

The design assessment of λ/4 phase-shifted DFB laserstructures

A detailed nonlinear model of the performance of single-frequency laser structures operating both below and above threshold is discussed. Arbitrary series combinations of uniform pitch grating, linearly-chirped pitch grating and plane guide sections can be analyzed-taking longitudinal-mode spatial hole burning into account. The material properties of each section of a device structure can be specified. The output power from each end of the laser and the emission wavelength, and the longitudinal intensity, carrier density, and relative permittivity profiles are predicted as a function of drive current above threshold for each lasing mode. The linewidth is also estimated while allowing for the nonuniform longitudinal distribution of spontaneous emission into the mode in a physical manner. The model was used to provide the data with which to trade off the numerous interacting performance parameters of a λ/4 phase-shifted DFB (distributed-feedback) laser. The design options are then summarized     

A new exact and efficient numerical matrix theory of complicated laser structures: properties of asymmetric phase-shifted DFB lasers

A numerical matrix method is developed which permits the analysis of very complicated laser structures. It is applied to different laser structures including asymmetric phase-shifted DFB-lasers both with abrupt and extended phase-shift sections. Results for modal behavior, threshold gain differences and power distribution are presented.     

Corrugation-pitch-modulated MQW-DFB laser with narrow spectrallinewidth (170 kHz)

A spectral linewidth of 170 kHz was achieved at a 1.5-μm wavelength in a 1200-μm long corrugation-pitch-modulated (CPM) distributed feedback (DFB) laser having multiple quantum wells (MQW). This is the narrowest linewidth ever reported for InGaAsP DFB lasers. The CPM structure is effective in maintaining the single longitudinal mode at a high output power by suppressing the spatial hole burning effect. The linewidth-power product is 400 kHz-mW, and the extrapolated residual spectral linewidth is 150 kHz     

High power operation of phase-shifted DFB lasers with amplitude modulated coupling coefficient

The performance characteristics of amplitude modulated coupling (AMC) phase-shifted MQW DFB lasers emitting near 1.55 mu m are reported for the first time. The AMC is obtained by the holographic double-exposure technique, it provides single longitudinal mode oscillation up to 78 mW for I=500 mA. This result confirms that AMC flattens the power distribution along the laser cavity. Linewidths as low as 600 kHz have been obtained for cavities as short as 600 mu m at P=15 mW.<>     

The effects of longitudinal gain distributions on the static andthe dynamic properties in a λ/4 phase-shifted DFB laser

The static and dynamic behaviors of the index-coupled DFB lasers are analyzed. In previous models, spatially dependent values were used for the refractive index distribution, but an averaged value was used for the gain distribution. The key feature of our model is that the “refractive index” and “gain” distributions are spatially dependent. The results of our model show a better agreement with an accurate model such as experimental data compared to those of the previous models. It was known that in the index-coupled DFB-lasers the gain profile as well as the refractive index profile plays an important role in determining the lasing characteristics, such as mode instability, chirping, linearity in the GRIN curve, and output power     

977-nm all-fiber DFB laser

Three-level operation of a fiber distributed feedback (DFB) laser operating around 980 nm is demonstrated for the first time. The ytterbium-doped DFB laser shows a maximum slope efficiency of 61% and output power of 38.2 mW under a launched single-mode pump power of 150 mW at 910 nm. The efficiency of lasers with different coupling strengths and at different pump wavelengths is also investigated.     

Analysis of quarter-wave-shifted DFB laser

Wavelength selectivity of a quarter-wave-shifted DFB laser is analysed taking into account the effect of a mirror facet at the end of the corrugation. The structure with no reflection is found to be the most promising. The effect of a cleaved facet at an end is not serious as long as KL is as large as 3?5.     

Proposed cross grating single-mode DFB laser

A new two-dimensional laser using a cross grating has been proposed. The calculations of the threshold gain and coupling constant show a relation between these parameters similar to the one-dimensional case, and also a uniform mode giving rise to radiation normal to the surface is shown to exist for a two-dimensional cross grating. These results suggest single-mode surface emission lasers with very little beam divergence     

半导体DFB激光器的自动温度控制

阐述了半导体热电制冷器（TEC）的工作原理,分析了线性驱动和脉冲宽度调制（PWM）驱动TEC的原理以及各自的特点,对Linear公司的热电制冷器控制芯片LTC1923作了介绍,讨论了基于LTC1923的半导体分布反馈式（DFB）激光器自动温度控制电路,并对实验和实际应用的结果进行了分析,给出了实测数据和波形。实验结果表明激光器中心波长变化范围为±5pm,对应管芯温度变化±0．05℃,说明温控电路可以有效地对激光器的工作温度进行控制。     

Large-signal dynamic model of the DFB laser

A computer model is proposed to analyze the characteristics of distributed feedback (DFB) lasers. The model is based on time-dependent coupled wave equations, with spontaneous emission taken into account. In order to avoid uncertain phase factors in spontaneous emission, a method of converting field equations to power equations in a matrix format before computation is introduced. The steady-state LI curve and transient response to the pulse excitation are calculated in the λ/4 phase-shifted DFB lasers. The longitudinal variations of the carrier and photon densities as well as of the refractive index are considered in the model     

DFB光纤激光器最佳输出特性研究

采用传输矩阵法,对影响DFB掺铒光纤激光器输出功率的耦合因子、光栅长度进行了研究,数值分析了不同谐振腔损耗下最佳输出功率所对应的最佳光栅长度及耦合因子的变化。结果表明,在设计光纤激光器时,根据光纤光栅的制作损耗,优化光栅长度及耦合因子可以使光纤激光器的输出实现最佳化。这些结论对基于光纤激光器的结构优化具有指导意义。     

High-precision high-yield laser source using DFB array

We present high-yield efficient distributed-feedback lasers with excellent wavelength control. An array of 12 lasers with highly reflecting/antireflecting facets is fabricated on a single chip with precisely controlled variations in the grating period or phase relative to the facets. The stripe that best meets requirements is selected for bonding. From 200 unscreened chips, 93% contained lasers that achieved the specified power of 25 mW at 175 mA, 55/spl deg/C, and 41% achieved a /spl plusmn/0.1-nm wavelength tolerance at 25 mW, 55/spl deg/C. This low-cost high-precision device requires little thermal tuning for wavelength-division-multiplexed applications and reduces the power consumption of the transmitter.     

DFB laser with attached external intensity modulator

A theoretical study is made of the frequency pulling effect exerted on a distributed feedback (DFB) laser by an external amplitude modulator that is directly attached to it. The modulator consists of a piece of waveguide whose loss is modulated by means of an externally applied voltage. The modulator affects the laser due to residual reflections from its far end which appear as a variable effective reflectivity to the output end of the DFB laser. Modulation affects the magnitude as well as the phase of the effective reflection coefficient presented to the laser due to the coupling of the real and imaginary parts of the effective refractive index of the modulator waveguide. The tuning problem is formulated as an eigenvalue equation for the DFB laser in the presence of an externally attached lossy cavity     

Single contact monolithically integrated DFB laser amplifier

A monolithic 1550-nm single-mode AlInGaAs-InP multiple quantum-well distributed feedback laser and amplifier is presented. For the 400-μm-long grating section κ=112+ 30i cm^-1, while the output is taken from the 200-μm-long amplifier section. The slope efficiency of the chip was 0.21 W/A, while the kink free power from the fiber was 34 mW. Narrow linewidths of <50 kHz were measured, and the dispersion penalty remained less than 2.0 dB for a data rate of 2.5 Gb/s over 300 km of SMF-28