Bing-Ruey Wu

External-cavity semiconductor laser tunable from 1.3 to 1.54 μm for optical communication

Using semiconductor optical amplifiers with properly designed nonidentical quantum wells made of InGaAsP-InP materials in the external-cavity configuration, the semiconductor laser is broadly tunable. The tuning range covers from 1.3 /spl mu/m to 1.54 /spl mu/m. Without additional filtering techniques, the laser beam emitted from the linear external cavity has the sidemode suppression ratio better than 30 dB. Also, the power ratio of the lasing mode to the total output power is 90%-99%, indicating the dominance of the lasing mode in the amplification process due to the broad gain spectrum.

Sequence influence of nonidentical InGaAsP quantum wells on broadband characteristics of semiconductor optical amplifiers--superluminescent diodes.

Extremely broadband emission is obtained from semiconductor optical amplifiers-superluminescent diodes with nonidentical quantum wells made of InGaAsP/InP materials. The well sequence is experimentally shown to have a significant influence on the emission spectra. With the three In(0.67) Ga(0.33) As(0.72) P(0.28) quantum wells near the n -cladding layer and the two In(0.53) Ga(0.47) As quantum wells near the p -cladding layer, all bounded by In(0.86) Ga(0.14) As(0.3)P(0.7) barriers, the emission spectrum could cover from less than 1.3 to nearly 1.55 microm, and the FWHM could be near 300 nm.

Improved temperature characteristics of laser diodes with nonidentical multiple quantum wells due to temperature-induced carrier redistribution

Laser diodes with nonidentical multiple quantum wells could have the lasing wavelength very insensitive to temperature variation. For temperature varying from 33 to 260 K, the lasing energy changes less than 5 meV, while the band gap energy changes more than 50 meV. The origin is due to the strongly temperature-dependent Fermi–Dirac distribution, which favors carriers in high-energy states at large temperature. The temperature-induced carrier redistribution could even cause negative characteristic temperature for a certain temperature range because the low-energy quantum wells behave like reservoirs to overcome the detrimental influence of temperature.

Extremely broadband tunable semiconductor lasers for optical communication

Using nonidentical multiple quantum wells, semiconductor lasers have very broadband tunability. For single-wavelength oscillation, the tuning range covers from 1300 nm to 1540nm. For dual-wavelength oscillation, the spectral separation is tunable up to 170 nm.

Electron-Determined Nonuniform Carrier Distribution among InGaAsP Multiple Quantum Wells

Experiments on laser diodes and superluminescent diodes with nonidentical InGaAsP multiple quantum wells (MQWs) show that quantum wells near the n-cladding layer could accumulate more carriers than those near the p-cladding layer, indicating that nonuniform carrier distribution is determined by electrons instead of holes. The electron-determined behavior is attributed to the thick separate-confinement heterostructure layer. This contrary observation to hole-determined nonuniform carrier distribution implies that carrier distribution among the MQWs could be engineered for desired purposes.

InGaAsP/InP laser diodes/superluminescent diodes with nonidentical quantum wells

Novel behavior of laser diodes (LDs) and superluminescent diodes (SLDs) fabricated on substrates with nonidentical quantum wells has been discovered. Mirror-imaged nonidentical quantum well (QW) lasers/superluminescent diodes have been designed, fabricated, and measured. Nonuniform carrier distribution inside multiple quantum wells is further verified experimentally. Measured characteristics also show that electrons, instead of holes, are the dominant carrier affecting carrier distribution. The sequence of the nonidentical QW is also shown to have significant influence on device characteristics, showing very different carrier distribution in each sequence.

Improved temperature characteristics of semiconductor lasers due to carrier redistribution among nonidentical multiple quantum wells

Semiconductor lasers with nonidentical InGaAsP/InP multiple quantum wells for optical communication are experimented to show the improved temperature characteristics. We explore the dependence of carrier distribution on temperature and discover the novel temperature characteristics of semiconductor lasers with nonidentical multiple quantum wells, which are different from conventional ones with identical multiple quantum wells. The origin is due to the strongly temperature-dependent Fermi-Dirac distribution, which favors carriers in high-energy states at high temperature. As a result, carriers redistribute among those quantum wells as temperature varies. It causes the lasing wavelength much less dependent on temperature, compared to the bandgap shrinkage. The carrier redistribution favoring high-energy states also significantly improves the characteristic temperature of short-wavelength mode.

Semiconductor lasers tunable from 1.3 μm to 1.54 μm for optical communication

Extremely broadband tunability of semiconductor lasers is achieved. The tuning range covers from 1300 nm to 1540 nm using nonidentical multiple quantum wells (MQWs) in the gain media. The broadband gain medium has two In0.53Ga0.47As quantum wells (Qws) near the n-cladding layer and three In0.67Ga0.33As0.72P0.28 Qws near the p-cladding layer. The sequence of the MQWs is also found to be very influential on the tuning range. For the sequence opposite to the above one, the tuning range is only from 1290 nm to 1450 nm. The reason is because the well sequence influences the carrier distribution. The broadband tunability is possible only when the QW structure could have a better uniformity of carrier distribution.

Reducing temperature dependence of semiconductor lasers using nonidentical multiple quantum wells

Semiconductor lasers with InGaAsP/InP nonidentical multiple quantum wells (MQWs) for optical communication are experimented to show the improved temperature characteristics. With proper layout of the nonidentical MQWs, the characteristic temperature of the laser diodes is increased. Also, the differential quantum efficiency increases to around 40% for the temperature increasing from 30 degree(s)C to 40 degree(s)C and approximately remains at this value for temperature above 40 degree(s)C. The reason is attributed to the carrier redistribution in the nonidentical MQWs as temperature increases. The change in temperature causes certain QWs to have increased carriers. Therefore their corresponding gain increases to overcome other effects that degrade temperature characteristics. With proper design of nonidentical MQWs, significant improvement on temperature characteristics of semiconductor lasers is possible.

Broadband tunability of external-cavity semiconductor lasers for optical communication

This work reports the significant influence of the layout of nonidentical MQWs on the broadband tunability of external-cavity semiconductor lasers. Study shows that, using properly designed MQWs as the laser gain material, the external-cavity semiconductor laser exhibits an extremely broadband tuning range, covering from 1300 nm to 1540 nm. On the other hand, if opposite sequential layout of MQWs is used, tunability covers only from 1290 nm to 1450 nm.