Ridge Waveguide DFB Laser Research Articles

Direct modulation bandwidth enhancement of uncooled DFB laser operating over a wide temperature range based on groove-in-trench waveguide structure

Uncooled direct modulation DFB laser offers high speed transmission rate over a wide temperature range with high reliability and low cost, making it a cost-effective light source choice for 5G fronthaul and data center applications. However, a significant 3dB bandwidth decrease can be observed in high temperature for conventional DFB lasers. We present an uncooled DFB laser operating up to 85°C with extended direct modulation bandwidth and high reliability based on a novel groove-in-trench ridge waveguide structure, where two narrow grooves penetrating the active layer are etched symmetrically in the two conventional trenches by deep wet etching, respectively. By optimizing the distance between the groove and the mesa stripe, we obtain a 3dB bandwidth of 15.3 GHz at 85°C, which is a 3.7 GHz improvement compared with the conventional ridge waveguide DFB laser. Transmissions of 25 Gb/s NRZ signal at 25°C and 85°C with clear eye openings have been demonstrated. It also achieves 25 Gb/s transmission over 10 km optical fiber with a low power penalty of 0.5 dB for a bit error rate of 10-12 at 85°C. In addition, the result of 2000-hour aging test shows that the proposed groove-in-trench structure DFB lasers have the same excellent reliability as the conventional ones.

A horn ridge waveguide DFB laser with reduced spatial hole burning for high-speed modulation

In this paper, we propose a DFB laser with a horn ridge waveguide (HRW) to suppress the longitudinal spatial hole burning (LSHB) effect in the lasers cavity, thus to reduce the rolloff at low frequency. The simulation result shows that HRW DFB lasers could significantly suppress the LSHB effect and its modulation bandwidth is increased by 14% comparing with the conventional straight ridge waveguide (RW) DFB lasers when the normalized coupling coefficient (κL) is 3.0. The calculated eye diagrams of HRW DFB lasers under direct 25 Gbps modulation have clearer opening than that of the conventional RW DFB lasers. These superior properties are due to the suppression of the LSHB effect by the HRW structure.

10 Gbit/s transmission using directly modulateduncooled MQW ridge waveguide DFB lasers inTO package

Direct modulation at 10 Gbit/s and uncooled operation of a MQW ridge waveguide laser at 1.3 /spl mu/m is demonstrated. Transmission experiments over 10 km at room temperature and over 4 km at a transmitter case temperature of 65/spl deg/C over standard singlemode fibre have been performed. Both transmitter and receiver are packaged into standard TO46 cases, thus offering low-cost potential for future high-speed datacom applications.

A ridge waveguide DFB laser model including transverse carrier and optical effects

In this paper, a steady-state model for ridge waveguide DFB lasers is presented. The complex two-dimensional semivectorial optical mode in the transverse direction is solved using a finite difference scheme without introducing any approximations. The electron and hole diffusion in the lateral direction is also considered, Along the longitudinal direction, a novel "Superposition of Spectral Power Method" is used, based on the coupled mode formulation. This model enables one to examine the interaction between the optical and carrier profiles for different injection levels and arbitrary transverse index profiles. As such, it is useful for studying CW characteristics such as lasing wavelength and threshold current. Finally, the results from this model are compared with experimental data from a varying ridge width laser array fabricated from a 1.55 /spl mu/m InGaAsP-InP compressively strained multiquantum-well loss-coupled DFB structure.

Realization and Characterization of Optically-Pumped GaInN-DFB Lasers

ABSTRACTWe demonstrate room temperature laser activity of optically pumped GaN/GalnN-DFB-lasers. The ridge-waveguide DFB lasers were realized on GaN/GalnN double heterostructures grown by low-pressure metal-organic vapor phase epitaxy. The best laser threshold we achieved is 1.9 MW/cm2.By varying the grating period, the laser emission wavelength could be tuned from 399 to 415 nm. This allows to determine the dispersion relation of the effective refractive index neff(λ) and the spectral dependence of the pump power density at the laser threshold Pth(λ) over the whole emission range. Furthermore, the shift of the emission wavelength with temperature of the DFB-lasers is investigated and is found to be small compared to the emission wavelength shift of the gain maximum.

Selection of transverse oscillation modes in tilted ridge DFB lasers

In this paper, the effects of tilt angle on multi-transverse moded ridge-waveguide DFB lasers is presented. A small tilt angle is introduced between the waveguide orientation and the gratings to control the lasing wavelength. The authors find that although each transverse mode experiences a wavelength shift that approximately varies as 1/cos /spl theta/, the accompanying variation in /spl kappa/ dictates which transverse mode will oscillate. At small tilt angles the fundamental E/sub x,0/ mode has the lowest threshold gain; at larger angles the higher order transverse modes will be sequentially selected while all other modes are attenuated. As a result, the wavelength versus tilt angle exhibits sudden jumps due to this transverse mode selection in addition to the 1/cos /spl theta/ dependence. For the analysis, the authors develop a two-dimensional finite-difference method for modeling the multilayered ridge waveguide modes. The effect of tilt angle on the intramode coupling coefficient is derived and the behavior of lasing wavelength, threshold gain and stop-band width are studied.

Clock recovery based on a new type of selfpulsation in a 1.5 μm two-section InGaAsP-InP DFB laser

Clock extraction from an optically or electrically injected 223 − 1 PRBS RZ data signal in a two-section ridge waveguide DFB laser with a new type of selfpulsation is demonstrated between 0.4 and 0.7 GHz. A locking range of 50 MHz is measured.

Self-Aligned Ridge-Waveguide DFB Lasers Emitting at 1.55 µm: Ridge-Width Dependence

Self-aligned ridge-waveguide (SA-RG) DFB lasers emitting at 1.55 µm have been fabricated utilizing the MOVPE growth technique and a self-aligning process. The ridge-width dependence of the threshold current and the optical lateral mode is investigated. Ridge-waveguide lasers with a thin active layer of 0.1 µm for low threshold current provide sufficient index guiding. The fabricated SA-RG DFB laser has a threshold current of as low as 29 mA. The threshold current density increases as the ridge width becomes narrower than 10 µm. This is explained by the electron diffusion in the active layer and the diffusion length is experimentally estimated to be 2–5 µm. The measured far-field pattern parallel to the junction shows a single-lobe pattern at a ridge width of less than 10 µm.

Stabilisation of oscillation frequency of an AlGaAs/GaAs ridge waveguide distributed feedback laser

Oscillation frequency of an AlGaAs/GaAs ridge waveguide DFB laser is stabilised without temperature control. The frequency fluctuation is suppressed to less than±5 MHz for a temperature change of 0.1 deg C.

Reduction of laser chirp in 1.5 μm DFB lasers by modulation pulse shaping

The dynamic linewidth of 1.5 μm ridge waveguide DFB lasers is shown to be reduced by shaping the pulse of the laser modulating waveform. Pulse shaping is performed by a second-order network designed to cancel the small-signal laser resonance. Results demonstrate a dynamic linewidth reduction from 1.4 A to 0.55 A FWHM for a 500 ps pulse.

Long-span optical transmission experiment over 222.8 km of commercial monomode fibre at 140 Mbit/s and 1.525 μm

A 140 Mbit/s optical transmission experiment has been conducted over 222.8 km of commercially available monomode, step-index fibre using a 1.525 μm ridge-waveguide DFB laser and hybrid Ge APD receiver. An overall system margin of 1.2 dB was observed after full regeneration.

Continuous-wave operation of 1.5 μm distributed-feedback ridge-waveguide lasers

CW operation of 1.5 μm ridge-waveguide DFB lasers is reported for the first time. The ridge-waveguide DFB laser structure offers the prospect of high modulation speeds due to the absence of parasitic capacitances associated with reverse-biased current-blocking layers. These devices also represent the first report of CW operation of DFB lasers fabricated using the hybrid LPE/MOCVD crystal-growth technique and also of DFB lasers with gratings produced by electron-beam lithography.