O. Anton

The intrinsic frequency response of 1.3-/spl mu/m InGaAsN lasers in the range T=10/spl deg/C-80/spl deg/C

Optical modulation response experiments above threshold are carried out in ridge waveguide InGaAs and InGaAsN (N=0.5%) in a temperature span of 10 degC-80 degC. The modulation traces are analyzed with a complete rate equation model that allows extraction of the resonance frequency and damping that are intrinsic to the carrier and photon processes occurring in the laser active region. This analysis enables calculation of the K-factor and its temperature behavior. K-values for InGaAsN lasers are larger and show a more pronounced dependence on temperature than in InGaAs lasers. This behavior is ascribed to a decrease in the effective differential gain with nitrogen content

Increased monomolecular recombination in MOCVD grown 1.3-/spl mu/m InGaAsN-GaAsP-GaAs QW lasers from carrier lifetime measurements

The recombination lifetime of metal-organic chemical vapor deposition grown InGaAsN-GaAsP-GaAs lasers with nitrogen content of 0% and 0.5% has been investigated from below threshold modulation frequency response measurements. Using an analysis that removes the contribution of electrical parasitic effects from the measured lifetime, it is shown that the recombination lifetime is significantly reduced when nitrogen is added into the quantum well. Furthermore, it is shown that this reduction is mainly the result of approximately a factor of four increase in the monomolecular recombination rate.

Frequency response of strain-compensated InGaAsN-GaAsP-GaAs SQW lasers

We investigate the below and above threshold frequency response of InGaAsN lasers with different nitrogen content. This is accomplished through detailed analysis of the small signal modulation response of the laser diodes using a comprehensive model based on rate equations and that incorporates the effect of parasitics. For below threshold conditions the model is instrumental in separating the contributions from the parasitics (more severe at low bias) and carrier recombination (predominant at higher bias) to the measured carrier lifetime. It is found that the addition of nitrogen reduces the recombination lifetime, mainly as a result of a four-fold increase in monomolecular recombination which predominates even near threshold. For bias above threshold the analysis compares electrical versus optical modulation frequency responses and concludes that resonance frequency and damping extracted from the electrical modulation responses are significantly influenced by the device parasitics. Instead, it is shown that optical modulation traces allow extraction of a relaxation frequency that is shaped only by the stimulated processes in the laser active region. Even in this case, the damping is found to be affected by the parasitics. When compared with nitrogen free lasers, a reduction in the resonance frequency is observed, while the damping is not altered. The former arises from a factor of /spl sim/2.5 decrease in the combined effect of the differential gain and carrier transport parameters. The latter reflects the more significant contribution of the parasitics to the damping.

Small-signal response of 1.3-/spl mu/m InAsP-InGaAsP quantum-well laser diodes obtained with a terahertz-bandwidth frequency comb

We describe an optical method to carry out small-signal frequency response measurements in laser diodes. This method uses a midinfrared tunable femtosecond optical parametric oscillator (OPO), whose frequency spectrum consists of a comb composed by the multiple harmonics of the 81-MHz repetition rate of the same intensity and extending over 2 THz. Tuning of the OPO allows selective generation of carriers in the different regions of the test laser active area without compromising the frequency bandwidth. The small-signal frequency response of the test laser is retrieved from the intensity changes in the frequency comb spectrum. We apply this method to investigate the small-signal frequency response of 1.3-/spl mu/m InAsP quantum-well (QW) lasers. The results of these experiments show that the intrinsic frequency bandwidth of these lasers is limited to less than 10 GHz as a result of state filling and related carrier escape out of the well. An analysis of the frequency response traces through a solution of a system of rate equations allows us to estimate the magnitude of the gain compression associated with this process.

Small signal frequency response of laser diodes using a femtosectond frequency comb

A novel method to measure the optical modulation response of laser diodes that uses as the modulation source the output of a femtosecond optical parametric oscillator (OPO) is described. The femtosecond OPO generates a train of ~ 150 fs pulses tunable between 1.03 and 1.35 μm with an average power of 12 mW at a repetition rate of 81 MHz. With such a narrow pulse a rich frequency spectrum of flat intensity distribution that easily surpasses the 2000 GHz 3 dB-bandwidth is obtained. To perform modulation response measurements the OPO is selectively tuned to modulate the carrier population in either the well or separate confinement region of the laser diode. Modulation traces obtained with this method in 1.3 μm InAsP lasers are presented and compared with those obtained from electrical modulation at the same operating conditions.

Effect of nitrogen content and temperature on the f/sub 3 dB/ of 1.3 /spl mu/m dilute-nitride SQW lasers

Above-threshold frequency response measurements carried out on strain-compensated InGaAs-and-InGaAsN lasers of identical geometry reveal a reduction in the laser relaxation frequency and damping due to the incorporation of nitrogen. Raising of temperature further decreases f/sub 3 dB/.

Investigation of the carrier dynamics of strain compensated InGaAsN quantum wells

A quantum dot-like behavior in the dynamics of carrier recombination is observed in InGaAsN quantum wells at temperatures at and below /spl sim/ 150 K. At higher temperatures defect recombination plays a dominant role.

Frequency response measurements in pulsed laser diodes by frequency offset detection

We describe a simple technique to obtain the small signal frequency response (FR) of laser diodes that are pulse biased. The method is capable of unprecedented rejection to cross-talk.

The 3 dB bandwidth of strain-compensated dilute-nitride quantum-well lasers

Above threshold frequency response measurements carried out on strain-compensated InGaAs and InGaAsN lasers with similar separate confinement heterostructures show a severe reduction in the laser relaxation frequency and damping due to the incorporation of nitrogen.

Femtosecond optical modulation measurements of the 3 dB bandwidth of 1.3 /spl mu/m InAsP lasers

Summary form only given. We describe a method to obtain the frequency response of semiconductor laser diodes that employs optical instead of electrical modulation. The technique uses the output of a femtosecond Optical Parametric Oscillator to excite the laser diode, biased above threshold, through a window placed on the top p-side of the laser. The laser emission coming from one of the facets passes through an optical isolator and is launched into an optical fiber, which guides the signal to the input of a 26 GHz photodetector. The detector output is connected to an HP 8561 Spectrum Analyzer. The signal at the spectrum analyzer consists of a discrete number of lines separated by a frequency equal to the OPO repetition rate, 81 MHz. The frequency response of the laser is obtained by measuring the amplitude of each of the harmonics with a narrow Intermediate Frequency (IF) bandwidth, thereby reducing the noise floor.