Norihiro Iwai

Recorded Low Power Dissipation in Highly Reliable 1060-nm VCSELs for “Green” Optical Interconnection

1060-nm VCSELs with low power dissipation and high reliability are demonstrated. We designed 1060-nm VCSELs with double intracavity structure to achieve high reliability and low power dissipation for the optical interconnection. We performed evaluations of an error-free 10-Gbps operation at low bias current, and the recorded low power dissipation per data rate of 0.14 mW/Gbps was achieved. Even though the modulation amplitude of the input signal was as small as 75 mVp-p, the extinction ratio of 6.5 dB was observed. From accelerating aging tests with 4898 devices, no random failure was observed, and high reliability of 30 failures in term (FITs)/channel with a confidence level of 90% was achieved.

Effects of well number in 1.3-/spl mu/m GaInAsP/InP GRIN-SCH strained-layer quantum-well lasers

Effects of well number in 1.3-/spl mu/m GaInAsP/InP GRIN-SCH compressively strained-layer quantum-well lasers were investigated from the viewpoint of the crystal quality of the strained-layer quantum wells and low threshold current operation at high temperature. As a result, we find that the optimum well number that gives the minimum threshold current increases with operating temperature and it was limited to the degradation of crystal quality of the quantum wells due to the critical thickness. A very high CW operating temperature of 170/spl deg/C was obtained. A very high output power of over 300 mW was also achieved. >

1.3 mu m InAs/sub y/P/sub 1/-/sub /y-InP strained-layer quantum-well laser diodes grown by metalorganic chemical vapor deposition

The authors have fabricated 1.3- mu m InAsP-InP separate-confinement-heterostructure (SCH) strained-layer double-quantum-well (SL-DQW) laser diodes (LDs) by metalorganic chemical vapor deposition (MOCVD). A low threshold current density of 410 A/cm/sup 2/ was obtained. The CW threshold current was as low as 1.8 mA at 20 degrees C, and maximum CW operating temperature of 120 degrees C was obtained. These characteristics are almost the same as those of well-designed GaInAsP-InP SL-QW LDs. Further improvement of the characteristics of InAsP-InP LDs is expected by optimizing the device structure. >

1.3-/spl mu/m-range GaInNAsSb-GaAs VCSELs

1.3-/spl mu/m-range GaInNAsSb vertical-cavity surface-emitting lasers (VCSELs) with the doped mirror were investigated. GaInNASb active layers that include a small amount of Sb can be easily grown in a two-dimensional manner as compared with GaInNAs due to the suppression of the formation of three-dimensional growth in MBE growth. The authors obtained the lowest J/sub th/ per well (150 A/cm/sup 2//well) for the edge-emission type lasers due to the high quality of GaInNAsSb quantum wells. Using this material for the active media, the authors accomplished the first continuous wave operation of 1.3-/spl mu/m-range GaInNAsSb VCSELs. For the reduction of the threshold voltage and the differential resistance, they used the doped mirror grown by metal-organic chemical vapor deposition (MOCVD). By three-step growth, they obtained 1.3-/spl mu/m GaInNAs-based VCSELs with the low threshold current density (3.6 kA/cm/sup 2/), the low threshold voltage (1.2 V), and the low differential resistance (60 /spl Omega/) simultaneously for the first time. The back-to-back transmission was carried out up to 5 Gb/s. Further, the uniform operation of 10-ch VCSEL array was demonstrated. The maximum output power of 1 mW was obtained at 20/spl deg/C by changing the reflectivity of the front distributed Bragg reflector mirror. GaInNAsSb VCSELs were demonstrated to be very promising material for realizing the 1.3-/spl mu/m signal light sources, and the usage of the doped mirror grown by MOCVD is the best way for 1.3-/spl mu/m VCSELs.

1.3-/spl mu/m InAsP modulation-doped MQW lasers

The effect of both n-type and p-type modulation doping on multiple-quantum-well (MQW) laser performances was studied using gas-source molecular beam epitaxy (MBE) with the object of the further improvement of long-wavelength strained MQW lasers. The obtained threshold current density was as low as 250 A/cm/sup 2/ for 1200-/spl mu/m-long devices in n-type modulation-doped MQW (MD-MQW) lasers. A very low CW threshold current of 0.9 mA was obtained in 1.3-/spl mu/m InAsP n-type MD-MQW lasers at room temperature, which is the lowest ever reported for long-wavelength lasers using n-type modulation doping, and the lowest value for lasers grown by all kinds of MBE in the long-wavelength region. Both a reduction of the threshold current and the carrier lifetime in n-type MD MQW lasers caused the reduction of the turn-on delay time by about 30%. The 1.3-/spl mu/m InAsP strained MQW lasers using n-type modulation doping with very low power consumption and small turn-on delay time are very attractive for laser array applications in high-density parallel optical interconnection systems. On the other hand, the differential gain was confirmed to increase by a factor of 1.34 for p-type MD MQW lasers (N/sub A/=5/spl times/10/sup 18/ cm/sup -3/) as compared with undoped MQW lasers, and the turn-on delay time was reduced by about 20% as compared with undoped MQW lasers. These results indicate that p-type modulation doping is suitable for high-speed lasers.

Tensile-strained GaInAsP-InP quantum-well lasers emitting at 1.3 /spl mu/m

Tensile-strained GaInAsP-InP quantum-well (QW) lasers emitting at 1.3 /spl mu/m are investigated. Low-pressure metalorganic chemical vapor deposition (LP-MOCVD) is used for crystal growth. High-resolution X-ray diffraction shows good agreement with theoretical simulation, photoluminescence spectra have good energy separation between light-hole and heavy-hole bands due to biaxial tension. The lowest threshold current density for infinite cavity length J/sub th//N/sub w//sup /spl infin// of 100 A/cm/sup 2/ is obtained for the device with -1.15% strain and N/sub w/=3. The amount of strain which gives the lowest J/sub th//N/sub w//sup /spl infin// experimentally clarified is around -1.2%. Threshold current of a buried-heterostructure (BH) laser is reduced to be as low as 1.0 mA. Enhanced differential gain of 7.1/spl times/10/sup -16/ cm/sup 2/ is also confirmed by measurements of relative intensity noise. Much improved threshold characteristic with the feasibility of submilliamp threshold current can be achievable by optimizing the BH structure. The tensile-strained QW laser emitting at 1.3 /spl mu/m with very low power consumption is attractive for the light source of fiber in the loop system and optical interconnection applications.

Structural dependence of 1.3-/spl mu/m narrow-beam lasers fabricated by selective MOCVD growth

The effect of structural parameters on the lasing characteristics of 1.3-/spl mu/m narrow beam lasers has been investigated. Monolithically integrated vertically tapered multiquantum-well (MQW) waveguide, fabricated by use of selective metal-organic chemical vapor deposition (MOCVD), is used for the expansion of the optical spot size. It is experimentally shown that the energy separation between the gain and waveguide regions that is formed simultaneously by selective MOCVD is shown to be an important parameter in order to achieve low-threshold current density and good temperature characteristics. The lengths of gain and waveguide regions have been investigated in terms of temperature characteristics of threshold current and far-field angle. A lower threshold current density and a higher characteristic temperature were obtained for longer gain region, We also have estimated the waveguide loss of the mode-field converter lasers diodes (MFC-LDs). High performance of 1.3-/spl mu/m integrated vertically tapered waveguide lasers were achieved in an optimized device.

InAsP/InGaP All-Ternary Strain-Compensated Multiple Quantum Wells and Their Application to Long-Wavelength Lasers

By introducing InGaP tensile-strained layers as barriers of InAsP compressively strained multiple quantum wells, InAsP/InGaP strain-compensated multiple quantum wells with high crystalline quality were successfully grown by metalorganic chemical vapor deposition. For the first time, a laser, emitting at 1.2 µ m, consisting of all-ternary quantum wells as an active layer was fabricated. The threshold current density of 1 kA/cm2 was obtained without the use of a separate confinement heterostructure layer for a cavity length of 1000 µ m.

Very high characteristic temperature and constant differential quantum efficiency 1.3-/spl mu/m GaInAsP-InP strained-layer quantum-well lasers by use of temperature dependent reflectivity (TDR) mirror

A very high characteristic temperature T/sub 0/ of 150 K (25-70/spl deg/C) or 450 K (25-50/spl deg/C) and an almost constant differential quantum efficiency operation in the temperature range of 25-70/spl deg/C were achieved in 1.3-/spl mu/m GaInAsP-InP strained-layer quantum-well (SL-QW) lasers by use of a novel temperature dependent reflectivity (TDR) mirror composed of multiple quarter-lambda thickness /spl alpha/-Si-SiOx dielectric films with quarter-lambda shift in the vicinity of center portion, The mechanism of high T/sub 0/ and constant differential quantum efficiency were explained using the structural parameters, transparent current density and gain coefficient of a SL-QW laser that are derived experimentally. The effect of TDR mirror was confirmed by measuring the temperature dependence of net gain of a SL-QW laser with TDR mirror. It was found that less temperature dependent net gain due to the decrease of mirror loss with temperature played an important role for improving the temperature characteristics of threshold current. Almost constant differential quantum efficiency over a wide temperature range is attributed to the increase of the facet reflectivity with temperature. >

Recorded low power dissipation of 0.14 mW/Gbps in 1060 nm VCSELs for “Green” optical interconnection

Extremely low power dissipation of 0.14 mW/Gbps at 10 Gbps operation with as small as 75 mVp-p of modulation amplitude has been achieved in carefully designed InGaAs/GaAs-MQW 1060 nm VCSELs employed double intra-cavity structure.