Gigahertz self-pulsation in 1.5 μm wavelength multisection DFBlasers

Self-pulsation in InGaAsP/InP multisection distributed feedback (DFB) lasers was generated reproducibly by adjusting appropriate injection conditions. Frequencies of up to some gigahertz were achieved. It was demonstrated that-in contrast to Fabry-Perot (FP) elements-no selective treatment of one section is required for creating the self-pulsation. It is concluded that the self-pulsation in DFB elements is of a different type than in FP elements     

1300-nm horizontal-cavity surface-emitting BH-DFB lasers for uncooled operation

We present a novel type of 1300-nm horizontal-cavity surface-emitting buried heterostructure distributed feedback (DFB) lasers showing high optical output power and uncooled direct modulation capability of 7.5 Gb/s. These lasers can be fabricated and tested using on-wafer techniques only, so the overall fabrication costs are considerably lower than with conventional edge-emitting DFB lasers.     

All-active tapered 1.55-/spl mu/m InGaAsP BH-DFB laser with continuously chirped grating

We demonstrate the first realization of all-active tapered index coupled 1.55-/spl mu/m InGaAsP buried-heterostructure distributed feedback lasers involving chirped gratings. The variation of the effective refractive index along the tapered active stripe is compensated using an optimized continuously chirped grating. The grating has been formed using a novel direct-write electron-beam lithography technique. Lasers with an antireflection/cleaved cavity show stable single-mode operation and high optical output power up to 60 mW. The yield of lasers with a sidemode suppression ration > 40 dB is more than 70%. The -3-dB farfield angles (full-width at half-maximum) amount to 14/spl deg/ and 20/spl deg/ in lateral and vertical direction, respectively.     

Dispersive self-Q-switching in self-pulsating DFB lasers

Self-pulsations reproducibly achieved in newly developed lasers with two distributed feedback sections and with an additional phase tuning section are investigated. The existence of the dispersive self-Q-switching mechanism for generating the high-frequency self-pulsations is verified experimentally for the first time. This effect is clearly distinguished from other possible self-pulsation mechanisms by detecting the single-mode type of the self-pulsation and the operation of one section near the transparency current density using it as a reflector with dispersive feedback. The operating conditions for generating this self-pulsation type are analyzed. It is revealed that the required critical detuning of the Bragg wavelengths of the two DFB sections is achieved by a combination of electronic wavelength tuning and current-induced heating. The previous reproducibility problems of self-pulsations in two-section DFB lasers operated at, in principle, suited current conditions are discussed, and the essential role of an electrical phase-control section for achieving reproducible device properties is pointed out. Furthermore, it is demonstrated that phase tuning can be used for extending the self-pulsation regime and for optimizing the frequency stability of the self-pulsation. Improved performance of the devices applied as optical clocks thus can be expected     

Dispersive self-Q-switching in DFB lasers-theory versus experiment

The single-mode model of dispersive self-Q-switching is extended to lasers containing a phase tuning section. The parameter set used for modeling is taken from independent measurements on existing self-pulsating devices. Detuning of the Bragg wavelengths by current induced heating is found, and this effect is included in the model. Calculated self-pulsation characteristics were compared quantitatively with experimental results on the device. A very good correspondence between theory and experiment is obtained, e.g., for conditions generating self-pulsations and for the frequency-current dependence. Dispersive self-Q-switching thus is confirmed as the responsible mechanism for high frequency DFB type self-pulsations. The modeling further shows that the delay between the stimulated emission within the device and the radiation of photons from the facets plays an important role for keeping the pulsations running     

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

Clock extraction from an optically or electrically injected 2/sup 23/-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.<>     

Controllable self-pulsations in multi-section DFB lasers with anintegrated phase-tuning section

1.55-μm InGaAsP-InP multi-section DFB lasers with an integrated phase tuning section have been fabricated. It is shown for the first time that the self-pulsation can be electrically switched on and off by adjusting the phase current. Reproducible self-pulsation characteristics from device to device are achieved in this way     

Electrically switchable self-pulsations in integratable multisection DFB-lasers

An integratable version of a self-pulsating AR-coated multisection DFB-laser with a phase-tuning section integrated between two DFB sections is presented. It is shown that the phase current can act as an electrical switch for turning ON and OFF the self-pulsations. In addition, the frequency stability can be improved by properly adjusting the phase current. The frequency of the self-pulsations is electrically tunable over more than one octave continuously.     

Optimization of the optical switching characteristics oftwo-section Fabry-Perot lasers

Bistable two-section Fabry-Perot lasers with a saturable absorber have been fabricated, comprehensively characterized, and optimized with respect to gain and optical switching contrast. Best device performance requires the individual optimization of both section lengths, and a proper choice of current conditions. Light has to be injected into the gain section, instead of the absorber section, to take full advantage of device qualities. Based on this optimization high, all optical switching gain (26 dB) and large contrast (18 dB) have been achieved simultaneously