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By comparison of the measured K factors (ratio of the damping factor to the square of the resonance frequency) of distributed feedback and Fabry–Perot lasers, it is found that the relaxation time associated with nonlinear gain for 1.3 μm InGaAsP lasers is about 0.1 ps. This short time constant is consistent with spectral hole burning being the dominant process responsible for the nonlinear gain.

For the first time, the enhanced low‐frequency relative intensity noise characteristics of semiconductor lasers is explained. It is shown, by multimode rate equation analysis, that the enhanced low‐frequency noise is caused by coupling between longitudinal modes which can renormalize the resonance frequency of the individual modes to very low values. It is further shown that a single‐mode laser will also exhibit enhanced low‐frequency noise unless the side‐mode suppression is high.

An optical modulation technique is used to determine three important parameters for 1.3 μm InGaAsP diode lasers: the rate of spontaneous emission into the guided modes, the nonlinear gain coefficient, and the carrier lifetime at threshold. These results are unaffected by electrical parasitics, and are essential to understanding the noise and modulation properties of diode lasers.

A small‐signal modulation bandwidth of 12.5 GHz is reported for vapor phase regrown 1.3‐μm InGaAsP buried heterostructure (BH) lasers operated at a bias optical power of only 6.9 mW/facet. The bandwidth per square root of bias optical power is a factor of 1.6 higher than previous best results. In addition, the optical modulation amplitude remains flat to 12 GHz in sharp contrast to other types of BH lasers which exhibit signal roll‐off at frequencies below the resonance frequency. The wide modulation bandwidth is attained by increasing the p‐doping level in the active region and by the choice of short cavity length. The device is grown on a conductive substrate, indicating that it is unnecessary to use a semi‐insulating substrate to obtain flat optical response in vapor phase regrown BH lasers.

In this letter the carrier dependence of the radiative bimolecular coefficients obtained from differential carrier lifetime measurements is reported. The bimolecular coefficient B(n) decreases significantly with carrier density. It is found that B(n) is well approximated by B(n)≂B0−B1n, with B1/B0=(1.1±0.2)×10−19 cm3 for GaAlAs and (1.6±0.2)×10−19 cm3 for 1.3 μm InGaAsP. This effect has a strong influence on the spontaneous emission efficiency in both InGaAsP and GaAlAs light sources.

Using the threshold carrier density measurement technique, the differential gain dg/dn at lasing threshold was measured. It was found that the differential gain dg/dn of 1.3‐μm InGaAsP lasers is a strong function of the active layer doping level P0. At a doping level of 2.5×1018 cm−3, the differential gain is several times larger than at 4×1017 cm−3. A factor of 2 increase in the modulation bandwidth is demonstrated using the dg/dn dependency on P0.

The letter describes the theory and experiment of the newly developed parasitic‐free frequency response measurement technique using facet‐pumped optical modulation on diode lasers. It was found that the modulation damping rate depends on the relative position of the pump laser wavelength with respect to the Fabry–Perot resonance wavelength of the laser under study. This effect is fully explained in terms of the carrier‐induced index change. For multilongitudinal mode lasers, it is shown experimentally and theoretically that the damping rate and frequency response measured by this technique give the intrinsic frequency response corresponding to direct current modulation only if the cavity lengths of pump and probed lasers are equal, and then only if the pump laser wavelength coincides with the Fabry–Perot transmission maximum or minimum of the probed laser.

The newly developed differential carrier lifetime and threshold carrier density measurement techniques are applied to temperature‐dependent measurements of the recombination rates and threshold carrier density of III‐V semiconductor lasers. Quantities obtained from these measurements are used to predict the temperature dependence T0 of the threshold current, which is in excellent agreement with T0 observed at 20 °C for both InGaAsP and AlGaAs lasers. The main causes for the stronger temperature sensitivity of InGaAsP material are due to Auger recombination and a smaller radiative coefficient.

Calculation using the recently proposed nonlinear gain caused by the cavity standing wave induced gain and index grating shows that the resonance frequency square is very nearly proportional to the modulation damping factor irrespective of cavity dimensions in semiconductor diode lasers. This is in agreement with experimental observation. Furthermore, the magnitude of the predicted damping factors is compared with measurements of V‐groove lasers and mass‐transport lasers. Excellent agreement is also obtained. This gives an alternative explanation of the origin of nonlinear gain other than spectral hole burning.

A simple and accurate method is described for measurements of the carrier density at lasing threshold in double heterostructure diode lasers. The carrier densities measured are compared with those deduced from differential carrier lifetime measurements. Excellent agreement is obtained for the two independent methods.

The frequency response of a 1.3‐μm InGaAsP vapor phase regrown buried heterostructure laser with an 18‐GHz cw bandwidth is analyzed in detail. The intrinsic bandwidth of the device is shown to be 22 GHz and the 3‐dB RC roll‐off frequency due to electrical parasitics is found to be 10 GHz.

The fabrication and performance of high‐speed and high‐power 1.3‐μm InGaAsP buried crescent lasers with semi‐insulating current blocking layers are reported. A modulation bandwidth of 11 GHz and acw output power of 42 mW/facet have been achieved. An approximate circuit model of the semi‐insulating buried crescent laser, which describes the effect of dc bias on parasitic capacitance at high‐speed operation, is also presented.

A novel method is described for measuring the carrier lifetimes in double heterostructure light‐emitting diodes (LED’s) and lasers. The improved resolution of the technique permits the first reported measurement of the carrier dependence of the radiative recombination coefficient. The technique also provides a reliable measurement of the active region doping level which is in very good agreement with the values calculated from the composition of the growth solutions.

A hybrid growth technique has been used to fabricate low‐threshold, high‐modulation bandwidth, and high‐power 1.3 μm InGaAsP buried crescent injection lasers. The technique involves a first growth of an Fe‐doped semi‐insulating current confinement layer by low‐pressure metalorganic chemical vapor deposition followed by a liquid phase epitaxy regrowth. The lasers have cw threshold currents as low as 10 mA at 25 °C, total differential quantum efficiency over 50%, high‐temperature operation up to 100 °C, and output power more than 33 mW/facet. A 3‐dB modulation bandwidth of 8.4 GHz has been achieved at 5 mW/facet.

A hybrid growth technique has been used to fabricate low threshold 1.51 μm InGaAsP buried crescent injection lasers with a semi‐insulating current confinement layer. The technique involves a first stage of low pressure metalorganic chemical vapor deposition followed by a liquid phase epitaxy stage. The lasers exhibit cw threshold currents as low as 12 mA at 25 °C, high yield, differential quantum efficiency over 41%, and output power more than 18 mW. Small‐signal modulation response to 3.5 GHz has been obtained. The lasers show an initial small degradation rate of 1%/kh at 50 °C which gives an estimated operating lifetime of 47 years at 25 °C.

The hot‐carrier effects reported for InGaAsP light‐emitting diodes are shown to result primarily from lattice heating. The small amount of heating observed at currents corresponding to typical threshold current density has negligible effect on the characteristic temperature T0 measured for InGaAsP lasers under pulsed conditions.