S. Murata

InGaAsP double-channel- planar-buried-heterostructure laser diode (DC-PBH LD) with effective current confinement

A new high-performance 1.3-μm InGaAsP semiconductor laser is described, in which effective current confinement into the active region has been realized. A p-n-p-n current blocking structure is made by liquid-phase epitaxy (LPE) on both sides of the active-stripe mesa which is defined by a pair of channels in the double-heterostructure wafer. The double-channel-planar-buried-heterostructure laser diodes (DC-PBH LDs) exhibit high-laser performances, such as a high differential quantum efficiency of 78-percent maximum, which results in high electrical to optical power conversion efficiency 43 percent, and high light output power of over 50 mW, as a result of the improvement in the current blocking structure. The threshold current temperature sensitivity is found experimentally to be reduced remarkably by increasing the doping concentration in the p-cladding layer. Characteristic temperature as high as 100 K has been obtained. CW operation is possible up to 130°C.

THz optical-frequency conversion of 1 Gb/s-signals using highly nondegenerate four-wave mixing in an InGaAsP semiconductor laser

The authors report the application of the highly nondegenerate four-wave mixing (HNDFWM) process to a 1.5- mu m InGaAsP semiconductor laser in optical-frequency conversion experiments on 1-Gb/s intensity-modulated signals in a 1-THz conversion range. This conversion is based on a subpicosecond ultrafast nonlinear gain process in the laser. The HNDFWM was generated through the use of an injection-locking technique. The possibility of applying this phenomenon to an optical fiber dispersion compensator is also discussed.<<ETX>>

Analysis of differential gain in InGaAs-InGaAsP compressive and tensile strained quantum-well lasers and its application for estimation of high-speed modulation limit

A simplified model that furnishes an intuitive insight for the change in quantum-well (QW) laser gain due to QW strain and quantum confinement is presented. Differential gain for InGaAs-InGaAsP compressive and tensile strained multi-quantum-well (MQW) lasers is studied using the model. The comparison between the calculated and experimental results for lattice-matched and compressive strained MQW lasers shows that this model also gives quantitatively reasonable results. It is found that the variance-band barrier height strongly affects the differential gain, especially for compressively strained MQW lasers. The tensile strained MQW lasers are found to have quite high differential gain, due to the large dipole matrix element for the electron-light-hole transition, in spite of the large valence-band state density. Furthermore, a great improvement in the differential gain is expected by modulation p doping in the tensile strained MQW lasers. The ultimate modulation bandwidth for such lasers is studied using the above results. >

A photonic wavelength-division switching system using tunable laser diode filters

A photonic wavelength-division switching system using semiconductor tunable wavelength filters is proposed. A switching system using wavelength switches and multistage switching networks is discussed. A crucial point in developing this switching system is to achieve a large number of wavelength-division channels. The potential of 100 wavelength-division channels in such switching systems is estimated, based on InP optical integrated circuits. A wavelength network synchronization which permits the network to utilize such a large number of wavelength-division channels without wavelength misalignment and drift is proposed. An eight-channel wavelength-division switching experiment, using phase-shift-controlled distributed feedback laser diodes as tunable wavelength filters, is reported. >

Optical-confinement-factor dependencies of the K factor, differential gain, and nonlinear gain coefficient for 1.55 mu m InGaAs/InGaAsP MQW and strained-MQW lasers

Optical-confinement-factor Gamma dependencies of the K factor, differential gain, dg/dN, and nonlinear gain coefficient epsilon , for 1.55 mu m InGaAs/InGaAsP multiple-quantum-well (MQW) and compressively strained MQW lasers, were investigated experimentally. For both MQW and strained-MQW lasers, when Gamma is increased, the K factor is reduced, dg/dN is increased, but epsilon is almost constant. These results indicate that the Gamma dependence of the K factor mainly results from a change in dg/dN, and does not result from a change in epsilon . For the strained MQW lasers, the K factor, dg/dN, and epsilon are, respectively, half as large, twice as large, and the same as those for the MQW lasers, when both types of lasers have the same Gamma (=0.05). This suggests that the strained MQW lasers with a large Gamma have a small K factor and thus are preferable for achieving large modulation bandwidths.<<ETX>>

Observation of highly nondegenerate four‐wave mixing (≳1 THz) in an InGaAsP multiple quantum well laser

Highly nondegenerate four‐wave mixing (NDFWM) in the pump‐probe detuning region of more than 1 THz has been observed in an InGaAsP multiple quantum well laser for the first time. Each of the probe and signal frequencies is closed to cavity resonance modes for the pump laser and those outputs are enhanced. The highly NDFWM process is based on a mechanism whose response time is less than 0.2 ps.

Spectral characteristics for 1.5 &#181;m DBR laser with frequency-tuning region

A 1.5 μm frequency-tunable distributed Bragg reflector (DBR) laser was developed. Frequency tuning was performed by injecting current into the DBR region where the refractive index was reduced to result in the Bragg frequency change. Threshold current and external quantum efficiency were 16 mA and 26 percent, respectively. The maximum continuous wavelength tuning range was 1.03 nm ( = 136 GHz). Spectral linewidth was maintained at an almost constant value when the wavelength was tuned. Large frequency modulation (FM) efficiency of 1-3 GHz/mA and flat FM response up to a few hundred MHz were obtained.

1.5 μm tunable wavelength filter using a phase-shift-controlled distributed feedback laser diode with a wide tuning range and a high constant gain

We demonstrate a 1.5 μm tunable wavelength filter which uses a newly developed phase‐shift‐controlled distributed feedback laser diode. A tuning range as wide as 120 GHz (9.5 A) with 24.5 dB constant gain has been achieved. An 18‐channel wavelength selection with less than −10 dB crosstalk is expected with this filter.

High-performance single-longitudinal-mode operation of InGaAsP/InP DFB-DC-PBH LD's

The lasing performance of InGaAsP/InP distributed feedback laser diodes with double-channel planar buried heterostructure (DFB-DC-PBH LDs) is reported for end-titled and antireflection (AR) coated configuration. High-power CW single-longitudinal-mode (SLM) operation over 55-mW light output at room temperature, high-temperature CW SLM operation over 105°C, as well as stable SLM operation under 2-Gb/s high-speed direct modulation, have been attained for 1.3-μm band DFB-DC-PBH LDs. 1.5-μm band DFB-DC-PBH LDs have also exhibited excellent DFB lasing characteristics, such as high power over 20 mW and high temperature over 75°C CW SLM operation. DFB SLM yield in the laboratory was also examined for 1.3-μm DFB-DC-PBH LDs, giving rise to a good prospect for practical use in optical-fiber communication systems.

Tunable wavelength filters using λ/4-shifted waveguide grating resonators

We report on wide tuning range 1.5 μm wavelength filters using λ/4‐shifted waveguide grating resonators. A tuning range of a transmission resonance wavelength as wide as 42 A by carrier injection and two‐channel wavelength signal switching was achieved.