Motoyasu Morinaga

High-speed 1.5- mu m compressively strained multi-quantum well self-aligned constricted mesa DFB lasers

A great improvement in the high-speed characteristics for compressively strained multi-quantum-well (MQW) distributed-feedback (DFB) lasers with self-aligned constricted mesa structures is described. Negative wavelength detuning is an important factor in making possible the extraction of potential advantages for the compressively strained MQW DFB lasers. A 17-GHz bandwidth, which is the highest among the 1.5- mu m MQW DFB lasers, is demonstrated. A wavelength chirp width of 0.42 nm at 10 Gb/s is obtained due to a reduced linewidth enhancement factor that has a magnitude of less than 2. Nonlinear damping K factor in a DFB laser with 45-nm negative detuning has drastically decreased to 0.13 ns, about half of that for unstrained MQW lasers. This is mainly due to an enhanced differential gain as large as 6.9*10/sup -12/ m/sup 3//s. The estimated intrinsic maximum bandwidth is 68 GHz. >

High-speed 1.5 mu m self-aligned constricted mesa DFB lasers grown entirely by MOCVD

Ultrahigh-speed 1.5 mu m wavelength self-aligned constricted mesa GaInAsP-InP distributed-feedback lasers grown entirely by low-pressure metalorganic chemical-vapor deposition are discussed. A self-aligned process was applied to lower the stray InP junction capacitance to as low as 1.6 pF. A record bandwidth of 13 GHz in the 1.5 mu m wavelength region was demonstrated. >

Analysis on wide continuous wavelength tuning of rapid-tunable quantum-well DFB lasers with carrier-transport effects

The authors report, theoretically, the wide and rapid tuning characteristics of the enhanced-plasma effect (EPE) laser. The EPE laser is a novel wavelength tunable laser. It has a thick carrier reservoir between the p-cladding layer and the MQW active layer. Fast blue-frequency shifting, due to the plasma effect, is strikingly enhanced and exceeds the slow red-thermal-frequency drift. Continuous-wave tuning range is analyzed in consideration of the carrier transport time, the carrier lifetime in the reservoir, and heat generation owing to nonradiative recombination current. Wide continuous rapid tuning characteristics are demonstrated, theoretically. Over 10-nm continuous and rapid tuning range would he obtained by using an EPE structure. >

Thermal frequency drift suppression in tunable DFB lasers by plasma induced frequency shift enhancement

The authors propose enhanced-plasma-effect (EPE) lasers for coherent optical frequency division multiplexed networks. In the EPE lasers, the blue frequency shift due to the plasma effect is enhanced by incorporating a very thick p-side optical guide layer as a carrier reservoir for multiple quantum-well distributed feedback laser and it surpasses the red frequency shift due to the thermal effect. The results of demonstrating a frequency step response maintained in the blue shift region and an enhanced blue shift frequency modulation response over the whole modulation frequency range from DC are presented for the first time.<<ETX>>

The high-speed limit of FM response in semiconductor lasers

The high-speed frequency modulation (FM) response has been investigated through rate equation analysis. The intrinsic limit of FM response has been found to be given by the product of FM efficiency, eta /sub FM/, and the FM bandwidth, B. This relation shows that a wide FM bandwidth means a small FM efficiency. Although the FM efficiency changes with the differential gain or the nonlinear gain coefficient, eta /sub FM/B is almost constant. The value of eta /sub FM/B was about 5 GHz/sup 2//mA for 1.5- mu m InGaAsP/InP lasers with 300- mu m cavity length. This limit has been confirmed experimentally.<<ETX>>

High sped (13 GHz) 1.5 μm self-aligned constricted mesa DFB lasers grown entirely by MOCVD

Objective high speed 1.5 μm InGaAsP/InP DFB lasers are required for use in long haul multigigabit optical communication systems.

Analysis on tuning range of enhanced-plasma-effect lasers

The authors show wide and rapid tuning characteristics of the Enhanced-Plasma-Effect (EPE) lasers, which are new frequency tunable lasers having a thick carrier reservoir. Using the EPE lasers, continuous tuning range of more than 10 nm is predicted.