We present theory and experiment for high-speed optical injection in the absorption region of a quantum-well laser and compare the results with those of electrical injection including the carrier transport effect. We show that the main difference between the two responses is the low-frequency roll-off. By using both injection methods, we obtain more accurate and consistent measurements of many important dynamic laser parameters, including the differential gain, carrier lifetime, K factor, and gain compression factor. Temperature-dependent data of the test laser are presented which show that the most dominant effect is the linear degradation of differential gain and injection efficiency with increasing temperature. While the K-factor is insensitive to temperature variation for multiple-quantum-well lasers, we find that the carrier capture time and nonlinear gain suppression coefficient decreases as temperature increases.

/pdf/temperature-dependence-of-electrical-and-optical-modulation-3hucbjwrzq.pdf

Temperature dependence of electrical and optical modulation responses of quantum-well lasers

An approach for single mode operation of 1.3 /spl mu/m distributed feedback (DFB) lasers with a large side mode suppression ratio over a wide temperature range of -40/spl deg/C to 100/spl deg/C, is reported. The lasers utilize an optimized strained-layer multiquantum well (MQW) active region in combination with index/gain-coupling and detuning effect. A high characteristic temperature T/sub 0/ (90-100 K) was obtained in 1.3 /spl mu/m InGaAsP/InP strained-layer MQW Fabry-Perot lasers when the number of QWs exceeded 10. In gain-coupled DFB lasers, a very low temperature dependence of the threshold current has been obtained when there is no detuning or positive detuning of the lasing wavelength at room temperature with respect to the material gain peak. An infinite T/sub 0/ can be realized over certain temperature ranges, in which the threshold current exhibits a minimum, depending on the amount of detuning. The physical mechanism responsible for the appearance of this minimum, as well as the high side mode suppression ratio, are explained theoretically.

Single-mode operation over a wide temperature range in 1.3 /spl mu/m InGaAsP/InP distributed feedback lasers

The application of low-chirp MQW (multiquantum well)-EA (electro-absorption) modulators to subcarrier multiplexing (SCM) optical transmission systems is studied. The authors show that a third-order predistortion circuit is feasible for compensating the nonlinearity of this type of modulator. The degree of frequency chirping per optical intensity modulation depth of the modulator is theoretically determined to be about 1.4 MHz. A 42-channel AM-SCM signal transmitter with the predistortion circuit realizes both composite second-order distortion (CSO) and composite triple beat distortion (CTB) values under -57 dBc after 200-km-long transmission. The authors confirm dispersion-induced distortion of the MQW-EA modulator is as small as that of the LiNbO/sub 3/ modulator. Carrier-to-noise ratios (CNRs) of 45.2 dB for channel 1 and 43.8 dB for channel 42 were measured after 100 km transmission. It is found that the deterioration of a CNR is caused by the cascaded erbium doped fiber amplifiers (EDFAs), Rayleigh backscattered power and the optical phase noise. Theoretical CNRs show that the output power of the modulator should be higher to improve CNR.

Reduction of dispersion-induced distortion in SCM transmission systems by using predistortion-linearized MQW-EA modulators

A first comprehensive study of impact of random phase at cleaved facet on modal properties of partly in-phase gain-coupled distributed-feedback (GC DFB) lasers is carried out both theoretically and experimentally. It is shown that, variation of grating phase of antireflective (AR) facet has a relatively small impact on lasing properties, while that of cleaved facet has a significant influence not only on modal properties such as threshold, efficiency, front-to-back facet efficiency ratio (FB ratio), side-mode-suppression-ratio (SMSR), and transient SMSR (TSMSR), but also on DFB lasers' long term stability against longitudinal mode-switching. Correlation among different laser properties is revealed for GC DFB lasers, and compared with that of index-coupled ones. It is found that FB ratio provides a good description of long-term longitudinal mode stability against CL facet phase variation and equivalent external feedback in GC DFB lasers, while TSMSR reveals their dynamic properties for a fixed facet phase. It is shown that devices with a possible stable operation will exhibit both a large TSMSR and a large FB ratio in GC DFB lasers. Lasers that are located within the transition region between left Bragg mode region and the stably operated right Bragg mode region in phase-space will have either a low TSMSR or a small FB ratio, and, therefore, are susceptible to longitudinal Bragg mode-switching. The combination of TSMSR and FB ratio as a screening criteria provides a simple and yet powerful tool to single out the potentially unstable devices due to random facet phase distribution in AR/CL GC DFB lasers.

Impact of random facet phases on modal properties of partly gain-coupled distributed-feedback lasers

Single mode operation in a wide temperature range (-40/spl deg/C/spl sim/+85/spl deg/C) has been obtained, from an etched-QW strongly gain-coupled (SGC) distributed-feedback laser at 1.3 /spl mu/m. The SGC lasers exhibit an excellent sidemode-suppression-ratio (SMSR) of around 45-55 dB in continuous-wave operation, and a very good transient SMSR (TSMSR) of more than 35 dB during a gain-switched operation, both are over the entire temperature range. When mounted P-side up, the threshold current is about 12 mA at room temperature and 28 mA at +85/spl deg/C. The output power is more than 20 mW with only 120-mA injection current at +85/spl deg/C.

Strongly gain-coupled (SGC) coolerless (-40/spl deg/C/spl sim/+85/spl deg/C) MQW DFB lasers

In-phase gain-coupled distributed feedback (DFB) lasers with etched quantum-well active-layers emitting at 1.3-/spl mu/m wavelength have been fabricated for the first time. High optical output power up to 50 mW was achieved while single-mode operation was maintained at the longer wavelength side of the Bragg stop band because the in-phase gain coupling effect favors this wavelength. With the optimization of the strained-layer multi-quantum wells (MQW) in the active region, a large effective differential gain of 7.5-19/spl times/10/sup -16/ cm/sup 2/, a high modulation bandwidth of 18 GHz, and high temperature operation up to 100/spl deg/C were obtained when the DFB wavelength was not detuned from the material gain peak. >

High-power and high-speed performance of 1.3-/spl mu/m strained MQW gain-coupled DFB lasers

Summary form only given. High power and high modulation bandwidth 1.3 /spl mu/m DFB InGaAsP QW lasers with gain coupling in a strained-layer MQW active region are reported for the first time. Due to the nature of the gain coupling effect, devices show lasing spectra with a consistently high single mode yield.

http://ieeexplore.ieee.org/iel3/3955/11437/00518914.pdf

High-power and high-speed performance of gain-coupled 1.3 /spl mu/m strained-layer MQW DFB lasers

Dynamic single-mode 1.3-μm and 1.55-μm DFB lasers with high-modulation-bandwidth, high power, and high-temperature operation are desirable for long-haul optical communication systems, for low-cost operation of multichannel data interconnects, and for switching applications. Recently, high single-mode yield and high modulation bandwidths have been achieved by fabricating the grating corrugation in the strained-layer MQW active region1,2 in order to incorporate gain-coupling effects.

C. Blaauw

Papers

High-power and high-speed performance of 1.3-/spl mu/m strained MQW gain-coupled DFB lasers

High-power and high-speed performance of gain-coupled 1.3 /spl mu/m strained-layer MQW DFB lasers

Strained-layer MQW gain-coupled DFB lasers: an approach for high power and high-temperature operation