Integrated 1.3-/spl mu/m DFB laser electroabsorption modulator based on identical MQW double-stack active layer with 25-GHz modulation performance

1.31-/spl mu/m electroabsorption modulators monolithically integrated with a DFB laser diode have been realized using an identical InGaAsP-InP multiple quantum-well-layer structure composed of two different QW types. Low laser threshold currents <13 mA and high 3-dBe cutoff frequency up to /spl sim/25 GHz have been measured.     

New integrated buried laser-ridge modulator with identical active layer

Integrated laser modulators are attractive devices for wavelength-division-multiplexing optical systems due to their compactness, high output power, and low cost. Their fabrication simplicity is a way to decrease further the transmitter cost and address new opening markets of short range and metropolitan networks. We report a new integration scheme electroabsorption-modulator distributed feedback (DFB) laser based on well-established industrial solutions for discrete buried ridge (BRS) DFB lasers and discrete shallow ridge modulators. Processing simplification with an identical active layer has been possible due to a good behavior of strongly positively detuned BRS lasers. The integrated devices demonstrated 30-dB extinction ratio with 10-GHz bandwidth and P/sub out/=10 dBm for emission in 1.55-/spl mu/m range.     

Improved behavior of monolithically integrated laser/modulator by modified identical active layer structure

For the monolithic integration of laser and modulator an identical active layer structure is proposed. The combination of different multiquantum wells (MQW's) allows the reduction of the wavelength dependence of the absorption efficiency and the chirp. First experimental results are reported. Structures with two different MQW types and only one MQW type are compared.     

5-Gb/s performance of integrated light source consisting ofλ/4-shifted DFB laser and EA modulator with SI InP BH structure

The fabrication process and characteristics, including 5-Gb/s transmission, of an integrated light source consisting of a λ/4-shifted distributed feedback laser and an electroabsorption (EA) modulator are discussed. By introducing a semi-insulating (SI) InP on the butt-joint region, both the large electrical isolation resistance (>10 MΩ) between the laser and the modulator and a high optical coupling efficiency (>80%) between them are achieved. A typical threshold current was 50-70 mA, and single-mode operation at 1.576 μm was maintained up to 5.5-mW output power. The modulation voltage to swing between 90% transmission and 10% transmission was 6.2-12 V, depending on the modulator length in the range 1000-400 μm. The 3-dB bandwidth is 7.7 GHz and a linewidth enhancement factor (α) of 0.9 is estimated from the sideband-to-carrier ratio of the spectra     

Design rules for a low-chirp integrated DFB laser with an electroabsorption modulator

Feedback from the front facet of an integrated DFB laser with an electroabsorption modulator generates additional chirp to the single modulator. The reduction of the sensitivity to that feedback is in tradeoff relation with the external differential quantum efficiency and the single-mode yield. We introduce a figure-of-merit for the feedback sensitivity. It is obtained from the modeling of the small signal frequency modulation (FM). It indicates design rules for low-chirp and high-efficiency devices.     

24-GHz modulation bandwidth and passive alignment of flip-chip mounted DFB laser diodes

High-frequency lasers have been flip-chip mounted on silicon motherboards. Small-signal modulation bandwidths around 24 GHz were obtained. It was shown that the bandwidth was not limited by extrinsic parasitics associated with the mounting scheme. Lasers were passively aligned to single mode fibers in V-grooves with the self-aligning solder bump technique. By passive alignment 50% of maximum coupling efficiency obtained by active alignment was achieved.     

DFB laser monolithically integrated with an absorption modulator with low residual reflectance and small chirp

Transmission over 150 km of standard fibre at 5 Gbit/s, and over 75 km at 8 Gbit/s, is reported with a monolithically integrated DFB laser and Franz-Keldysh absorption modulator. The modulator facet reflectance is low. The device is stable over a range of operating parameters. The butt-joint, buried-heterostructure device is entirely grown by MOVPE.<>     

Linearization of DFB laser diode by external light-injected cross-gain modulation for radio-over-fiber link

A novel linearization technique of distributed-feedback laser diode in analog optical transmitter for radio-over-fiber (RoF) link was proposed. The proposed scheme was based on a light-injection technique using cross-gain modulation effect. According to the proposed idea, a linearized RoF transmitter module was implemented and evaluated. The enhanced performance of carrier-to-noise ratio and spurious-free dynamic range were experimentally demonstrated in a wide range of radio-frequency (RF) applications. The experimental results show that the proposed scheme can be applicable for broadband RF optical transmission applications.     

Stability of two modes in DFB laser diode under high data rate modulation

Using a DFB-LD with two longitudinal modes in the 1.55 ?m region, the mode stability was examined experimentally. It is found that these modes are very stable under direct modulation at least up to around 300 Mbit/s and there is no power penalty due to mode partition noise in 97 km single-mode-fibre transmission at 280 Mbit/s.     

Optical transmitter module with hybrid integration of DFB laser diode and proton-exchanged LiNbO3 modulator chip

In this work, a hybrid integrated optical transmitter module was designed and fabricated. A proton-exchanged Mach–Zehnder lithium niobate (LiNbO₃) modulator chip was chosen to enhance the output extinction ratio. A fiber was used to adjust the rotation of the polarization direction caused by the optical isolator. The whole optical path structure, including the laser chip, lens, fiber, and modulator chip, was simulated to achieve high optical output efficiency. After a series of process improvements, a module with an output extinction ratio of 34 dB and a bandwidth of 20.5 GHz (from 2 GHz) was obtained. The optical output efficiency of the whole module reached approximately 21%. The link performance of the module was also measured.     

High-energy coherent chirped pulses from multisection laser diode with thick active layer

High-energy (100 pJ) picosecond pulses are obtained from Q-switched AlGaAs multisection lasers with a thick (0.45-/spl mu/m) active layer. Single longitudinal mode operation in the Q-switching regime is achieved by injecting monochromatic optical pulses into the active region. Chirp amplitude and pulse energy are measured for different electrical pumping conditions in the absorber sections. High values of the time-bandwidth product of pulses (up to 30) are observed, it is shown that the chirp amplitude can reach 10 /spl Aring/. Therefore, it is expected that the 100 pJ coherent optical pulses can be compressed down to 1-2 ps, which represents attractive performances for compact short-pulse light sources.     

Transmission performance of monolithically integrated Y-branch tunable laser with zero-chirp Mach-Zehnder modulator

A zero-chirp Mach-Zehnder modulator monolithically integrated with a widely tunable modulated grating Y laser and SOA, operating at 10 Gbit/s, is demonstrated. The device is hermetically packaged with a wavelength locker within a 12.7times15.24 mm module. With a fixed receiver threshold and fixed voltage modulation depth, the extinction ratio exceeds 12 dB and the receiver penalty for dispersion in the range plusmn800 ps/nm is below 1.5 dB on all channels     

Multiwavelength DFB laser array with integrated spot sizeconverters

We describe the design, fabrication, and performance of a five-element quarterwave-shifted distributed feedback laser array with monolithically integrated spot size converters intended for use as a multiple-wavelength source in dense wavelength-division telecommunications systems. Facet power in excess of 10 mW with less than 150 mA bias and longitudinal side mode suppression greater than 40 dB were routinely achieved. Narrow far-field full-width at half-maximum angles of 6.9°×16.3° provided 3.5-dB coupling loss into single-mode fiber with 1.0-dB misalignment tolerances of ±2.0 μm. With ±10°C thermal tuning, 22 1555-nm channels spaced by 50 GHz were accessed with this device. Thorough field evaluation indicates that such a device is consistent with manufacturing requirements     

High-frequency modulation of a quantum-cascade laser using a monolithically integrated intracavity modulator

We report a quantum-cascade laser monolithically integrated with an intracavity modulator which could be operated up to 1 GHz. In contrast to earlier approaches, where the radio frequency (RF) modulation signal was supplied to the entire cavity length of the laser structure, we drive only a relatively small 375-/spl mu/m-long section of the cavity. At the same time, a quasi-continuous-wave signal was supplied to the remaining 1125-/spl mu/m-long section. This modulation scheme resulted in smaller parasitic capacitance effects than what we reported previously, and enabled us to work with lower RF voltages and currents.     

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.     

Extremely small-chirp electroabsorption-modulator integrated distributed feedback laser diode with a shallow quantum-well absorption layer

We have developed an extremely small-chirp electroabsorption modulator integrated with a distributed feedback laser diode (EAM-DFB-LD) with a novel shallow quantum-well (QW) absorption layer. By using a shallow QW absorption layer, the estimated lifetime of the photogenerated holes and thus the estimated concentration of the holes generated by optical absorption has been reduced to 9% of that for a conventional QW. It was experimentally confirmed that the excess chirp due to the pileup of carriers has been reduced to 10% of that for a conventional QW, and this result is consistent with the estimates. The shallow QW EAM-DFB-LD has shown a chirp parameter |/spl alpha/| less than 0.7 over the entire range of the EAM reverse bias voltage of 0-3 V. Finally, successful 10-Gb/s return to zero transmission has been confirmed through both positive dispersion (+425 ps/nm) and negative dispersion (-425 ps/nm).     

Optical nonlinear characteristics of a side-injectionlight-controlled laser diode with a multiple-quantum-well saturableabsorption region

A multiple-quantum-well bistable laser-diode structure in which the input signal is launched into the main laser through an orthogonally configured subwaveguide is proposed. Insensitivity to input light wavelength (28 nm of 3 dB bandwidth) and high isolation of input versus output (over 30 dB) are observed. In addition, reflection of input signal is negligibly small     

基于半导体MZ调制器与DFB激光器混合集成的小型化光发射模块的设计与研究

针对半导体DFB激光器、铌酸锂MZ调制器采用分立封装形式且整体尺寸较大的问题,采用半导体MZ调制器和DFB激光器两类芯片并进行混合集成封装有望显著减小模块的整体尺寸.论文根据芯片和模块尺寸要求提出了一个整体布局结构,并选用双透镜加隔离器以及锥形透镜光纤光耦合方案和微带线转GCPW微波耦合方案.通过仿真计算,对模块中激光...     

Pure frequency modulation or intensity modulation with suppressed frequency chirp using active Bragg reflector integrated laser

The modulation properties of a laser structure which consists of an active Bragg reflector (300 mu m) integrated with an uncorrugated gain region (600 mu m) have been measured. The laser exhibited a flat FM response and very low spurious intensity modulation when modulating the current in the Bragg reflector. Furthermore, broadband intensity modulation with suppressed frequency chirp could also be achieved. An inhomogeneous linewidth enhancement factor alpha caused by the uneven carrier density distribution between the two sections gives a qualitative explanation to our results.<>     

High performance laser with nanopatterned active layer by selective area epitaxy

Lasers containing a nanopatterned active layer demonstrating excellent threshold characteristics are presented. The nanopatterned active layer is fabricated using high-resolution electron beam lithography and selective-area metal organic chemical vapour deposition crystal growth. Results demonstrating an order of magnitude improvement over previous results are reported.