80/spl deg/C continuous-wave operation of 2.01-/spl mu/m wavelength InGaAlAs-InP vertical-cavity surface-emitting lasers

Electrically pumped buried tunnel junction InGaAlAs-InP vertical-cavity surface-emitting lasers (VCSELs) with self-adjusted lateral current and optical confinement and record emission wavelengths beyond 2 /spl mu/m are presented. Front and back side mirrors are realized using 31.5 epitaxial layer pairs of alternating InGaAs-InAlAs and a dielectric 2.5 pair CaF/sub 2/-a-Si layer stack. The devices show single-mode continuous-wave operation up to heat sink temperatures over 80/spl deg/C. The maximum output power at 20/spl deg/C reaches 0.43 mW, threshold current and voltage are as low as 0.66 mA and 0.73 V, respectively. To reach the long emission wavelength, we use an optimized active region comprising heavily strained quantum wells. High-resolution X-ray diffraction and photoluminescence measurements reveal excellent material quality without relaxation in the quantum wells.     

Efficient CW lasing and high-speed Modulation of 1.3-/spl mu/m AlGaInAs VCSELs with good high temperature lasing performance

The 1.31-/spl mu/m AlGaInAs vertical-cavity surface-emitting lasers achieved efficient single-mode (SM) continuous-wave lasing at temperatures up to 120/spl deg/C, with 2.0-mW output power and 31% slope efficiency, as well as multimode (MM) lasing with up to 9-mW output power and up to 39% slope efficiency. High-speed modulation at data rates up to 10 Gb/s and transmission through different lengths of SM and MM fiber are demonstrated.     

1.3 /spl mu/m InGaAsN vertical cavity surface emitting lasers grown by MOCVD

The first InGaAsN VCSELs grown by MOCVD with CW lasing wavelength longer than 1.3 /spl mu/m are reported. The devices were of conventional p-i-n structure with doped DBR mirrors. CW lasing up to 65/spl deg/C was observed, with a maximum output power at room temperature of 0.8 mW for multimode devices and nearly 0.3 mW for single-mode devices.     

High-performance single-mode VCSELs in the 1310-nm waveband

High-performance vertical-cavity surface-emitting lasers (VCSELs) emitting in the 1310-nm waveband are fabricated by bonding AlGaAs-GaAs distributed Bragg reflectors on both sides of a InP-based cavity. A 2-in wafer bonding process is optimized to produce very good on-wafer device parameter uniformity. Carrier injection is implemented via double intracavity contact layers and a tunnel junction. A 1.2-mW single-mode output power is obtained in the temperature range of 20/spl deg/C-80/spl deg/C. Modulation capability at 3.2 Gb/s is demonstrated up to 70/spl deg/C. Overall VCSEL performance complies with the requirements of the 10 GBASE-LX4 IEEE.802.3ae standard, which opens the way for novel applications of VCSELs emitting in the 1310-nm band.     

Improved spectral properties of an optically pumped semiconductor disk laser using a thin diamond heat spreader as an intracavity filter

This letter describes an optically pumped high-power InP-based semiconductor disk laser with a thin (50 /spl mu/m) diamond heat spreader bonded to the surface of the gain chip. The diamond heat spreader performs the multiple functions of heat removal, spectral filtering, and wavelength stabilization by utilizing the high thermal conductivity and the low thermooptic coefficient of diamond, along with the large free-spectral range of a thin intracavity etalon. A pump-power-limited output power of 680 mW at 1.55 /spl mu/m is demonstrated at a heat sink temperature of -30/spl deg/C, and 140 mW at room temperature. The spectral width was measured to be less than 0.08 nm and the spectral drift with temperature and pump power as low as 0.03 nm//spl deg/C and 0.14 nm/W, respectively.     

Long wavelength-tunable VCSELs with optimized MEMS bridge tuning structure

In this letter, we present the first demonstration of a long wavelength-tunable vertical-cavity surface-emitting laser (VCSEL) using a monolithically integrated bridge tuning microelectromechanical system structure. The use of such a tuning structure allows for better wavelength tuning repeatability and wider tuning range as compared to cantilever-based tunable VCSELs. The devices show tuning ranges over 22 nm with peak output power of 1.3 mW in continuous-wave operation at 15/spl deg/C. The bridge structure has a mechanical resonant frequency of 80 kHz. The transmission test through 300-km single-mode fiber (SMF-28) using the tunable VCSEL under mechanical vibration below 10 KHz and 10-G acceleration shows little bit-error-rate degradation.     

Low threshold current 1.3-/spl mu/m GaInNAs VCSELs grown by MOVPE

The structure of the conventional contact 1.3-/spl mu/m GaInNAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) was optimized and low threshold current 1.3-/spl mu/m GaInNAs VCSELs grown by metal-organic vapor-phase epitaxy were reported. The idea is to optimize the active region, the doping profiles, and the pairs of p-distributed Bragg reflectors, and the detuning between the emission wavelength and the photoluminescence gain peak wavelength. The continuous-wave 1.0-mA threshold current was achieved for the single-mode VCSEL. For the multiple-mode VCSELs, the below 2-mA threshold currents at 5/spl deg/C-85/spl deg/C , the 1.13-mA threshold current at 55/spl deg/C, and 1.52-mA threshold current at 85/spl deg/C are the best results for 1.3-/spl mu/m GaInNAs VCSELs.     

Rapid thermal annealed InGaN/GaN flip-chip LEDs

Nitride-based flip-chip (FC) light-emitting diodes (LEDs) emitting at 465 nm with Ni transparent ohmic contact layers and Ag reflective mirrors were fabricated. With an incident light wavelength of 465 nm, it was found that transmittance of normalized 300/spl deg/C rapid thermal annealed (RTA) Ni(2.5 nm) was 93% while normalized reflectance of 300/spl deg/C RTA Ni(2.5 nm)/Ag(200 nm) was 92%. It was also found that 300/spl deg/C RTA Ni(2.5 nm) formed good ohmic contact on n/sup +/ short-period-superlattice structure with specific contact resistance of 7.8/spl times/10/sup -4/ /spl Omega//spl middot/cm/sup 2/. With 20-mA current injection, it was found that forward voltage and output power were 3.15 V and 16.2 mW for FC LED with 300/spl deg/C RTA Ni(2.5 nm)/Ag(200 nm). Furthermore, it was found that reliabilities of FC LEDs were good.     

100-mW kink-free blue-violet laser diodes with low aspect ratio

400-nm-band GaN-based laser diodes (LDs) operating with a kink-free output power of over 100 mW and having a low aspect ratio of 2.3 have been successfully fabricated for the first time. A new ridge structure, in which the outside of the ridge is covered with a stacked layer of Si on SiO/sub 2/ and the ridge width is as narrow as 1.5 /spl mu/m, is applied to realize high kink-free output power with a wide beam divergence angle parallel to the junction plane. A new layer structure around the active layer is demonstrated to be quite effective for obtaining a narrow beam divergence angle perpendicular to the junction plane, maintaining low threshold current. Ten LDs with low aspect ratio have been operated stably for over 1000 h under 30-mW continuous-wave operation at 60/spl deg/C. Relative intensity noise measured under optical feedback with high-frequency modulation is as low as -125 dB/Hz. These results indicate that this LD is suitable for next-generation high-density optical storage systems.     

Comparison between epi-down and epi-up bonded high-power single-mode 980-nm semiconductor lasers

Epi-down and epi-up bonded high-power single-mode 980-nm lasers have been studied in terms of bonding process, thermal behavior, optical performances, and long-term laser reliability. We demonstrated that epi-down bonding can offer lower thermal resistance and improved optical performance without degrading the long-term laser reliability. An optical power of 630 mW was obtained for the first time from an epi-down bonded 980-nm pump module. Our studies have shown that epi-down bonding of single-mode 980-nm lasers can reduce junction temperature and thermal resistance by up to 30%. Experimental measurements showed over 20% in thermal rollover power improvement and over 25% reduction in wavelength shift versus current in epi-down mounted lasers compared to epi-up mounted lasers. Lifetime test over 14 000 h at 500 mA and 80/spl deg/C of the epi-down bonded lasers is reported for the first time.     

Continuous-wave operation of all-epitaxial InP-based 1.3 /spl mu/m VCSELs with 57% differential quantum efficiency

All-epitaxial InP-based 1.3 /spl mu/m VCSELs with a record-high continuous-wave differential quantum efficiency (57%) for single active region long-wavelength devices are demonstrated. Low-loss optical mode confinement is achieved through a selectively etched undercut tunnel-junction aperture. Singlemode continuous-wave lasing was observed up to 87/spl deg/C and the room-temperature output power was 1.1 mW at a current of 4.1 mA and a wavelength of 1.305 /spl mu/m.     

High-power single-mode antiresonant reflecting optical waveguide-type vertical-cavity surface-emitting lasers

Antiresonant reflecting optical waveguide (ARROW) techniques are employed in vertical cavity surface emitting lasers (VCSELs) to achieve high-power single-mode emission. Using the effective-index method and fiber mode approximation, the cold-cavity lateral modal behavior for the circular shaped ARROW VCSEL demonstrates significant reduction of radiation loss from that of a single antiguide, while maintaining strong discrimination against high-order modes. The circular-waveguide is created by selective chemical etching and two-step metal-organic chemical vapor deposition growth, with proton implantation used to confine the current injection to the low-index core region. A single-mode CW power of 7.1 mW has been achieved from an 8 /spl mu/m diameter ARROW device (index step /spl Delta/n = 0.05, emission at /spl lambda//sub 0/ = 980 nm) with a far-field FWHM of 10/spl deg/. Larger aperture (12 /spl mu/m) devices exhibit multimode operation at lower drive currents with a maximum single-mode continuous-wave output power of 4.3 mW.     

Superlattice barrier 1528-nm vertical-cavity laser with 85/spl deg/C continuous-wave operation

We report 85/spl deg/C continuous-wave electrically pumped operation of a 1528-nm vertical-cavity laser. An InP-InGaAsP active region was wafer bonded to the GaAs-AlGaAs mirrors, with a superlattice barrier to reduce the defect density in the active region.     

Highly reliable high-power 980-nm pump laser

We report on highly reliable, high-power, and high-performance 980-nm quantum-well laser chips and modules. Ridge waveguide laser diode chips with 750-mW output power and 500-mW fiber Bragg grating stabilized modules have been achieved and Telcordia-qualified. Long-term reliability tests show a very low failure rate of 400 FIT (failures in time) at 900-mA operating current or 500-mW module power. The kink-free fiber coupled module output power can be as high as 640 mW with grating stabilization, which produces very good wavelength stability and power stability. A further improved structure shows a record continuous-wave rollover chip power of 1.6 W for the 5-/spl mu/m-wide ridge waveguide laser diodes.     

1.5-mW single-mode operation of wafer-fused 1550-nm VCSELs

We demonstrate 1.5-/spl mu/m waveband wafer-fused InGaAlAs-InP-AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) emitting high single-mode power of 1.5 mW at room temperature with sidemode suppression ratio of over 30 dB and a full-width at half-maximum far field angle of 9/spl deg/. These devices have thermal resistance value below 1.5 K/mW and are emitting 0.2 mW at 70/spl deg/C. VCSELs with a wavelength span of 40-nm emission are produced from the same active cavity material, which shows the potential of realizing multiple-wavelength VCSEL arrays.     

All-epitaxial InAlGaAs-InP VCSELs in the 1.3-1.6-/spl mu/m wavelength range for CWDM band applications

All-epitaxial InAlGaAs-InP vertical-cavity surface-emitting lasers grown by metal-organic chemical vapor deposition were successfully demonstrated in the wavelength ranging from 1.3 to 1.6 /spl mu/m. The devices showed the high performances such as single-mode output power of higher than 1.1mW, sidemode suppression ratio of 37 dB, divergence angle of 9/spl deg/, and CW operation of temperature up to 80 /spl deg/C. We achieved the modulation bandwidth exceeding 2.5 Gb/s and power penalty free transmission over 30 km.     

3.125-Gb/s modulation up to 70/spl deg/C using 1.3-/spl mu/m VCSELs fabricated with localized wafer fusion for 10GBASE LX4 applications

The development of the 10GBASE-LX4 communication standard for aggregated 10-Gb/s rates feeds the need for low-cost laser sources in the 1275-1350-nm wavelength range operating at modulation rates of 3.125 Gb/s. We present comprehensive characterization of wafer fused vertical-cavity surface-emitting lasers with characteristics that meet the IEEE802.3ae specification for 10GBASE-LX4. These include output power greater than 1.5 mW up to 80/spl deg/C, wavelength around 1340 nm, single-mode emission and modulation at 3.125 Gb/s, and wide open eyes with rise and fall times below 100 ps up to 70/spl deg/C.     

Low-threshold continuous-wave 1.5-/spl mu/m GaInNAsSb lasers grown on GaAs

We present the first continuous-wave (CW) edge-emitting lasers at 1.5 /spl mu/m grown on GaAs by molecular beam epitaxy (MBE). These single quantum well (QW) devices show dramatic improvement in all areas of device performance as compared to previous reports. CW output powers as high as 140 mW (both facets) were obtained from 20 /spl mu/m /spl times/ 2450 /spl mu/m ridge-waveguide lasers possessing a threshold current density of 1.06 kA/cm/sup 2/, external quantum efficiency of 31%, and characteristic temperature T/sub 0/ of 139 K from 10/spl deg/C-60/spl deg/C. The lasing wavelength shifted 0.58 nm/K, resulting in CW laser action at 1.52 /spl mu/m at 70/spl deg/C. This is the first report of CW GaAs-based laser operation beyond 1.5 /spl mu/m. Evidence of Auger recombination and intervalence band absorption was found over the range of operation and prevented CW operation above 70/spl deg/C. Maximum CW output power was limited by insufficient thermal heatsinking; however, devices with a highly reflective (HR) coating applied to one facet produced 707 mW of pulsed output power limited by the laser driver. Similar CW output powers are expected with more sophisticated packaging and further optimization of the gain region. It is expected that such lasers will find application in next-generation optical networks as pump lasers for Raman amplifiers or doped fiber amplifiers, and could displace InP-based lasers for applications from 1.2 to 1.6 /spl mu/m.     

Room-temperature continuous-wave operation of GaInNAsSb laser diodes at 1.55 /spl mu/m

The first 1.55 /spl mu/m room-temperature continuous-wave (CW) operation of GaAs-based laser diodes utilising GaInNAsSb/GaNAs double quantum well active regions grown by molecular beam epitaxy is reported. In electrically-pumped CW operation the narrow ridge waveguide devices have a room temperature lasing wavelength of 1550 nm near threshold, increasing to 1553 nm at thermal rollover. The CW threshold current was 132 mA for a 3/spl times/589 /spl mu/m device, with a characteristic temperature of 83 K, measured in pulsed mode between 20 and 70/spl deg/C.     

MOVPE-grown GaInNAs VCSELs at 1.3 /spl mu/m with conventional mirror design approach

1.3 /spl mu/m oxide confined GaInNAs VCSELs designed using the same design philosophy used for standard 850 nm VCSELs is presented. The VCSELs have doped mirrors, with graded and highly doped interfaces, and are fabricated using production-friendly procedures. Multimode VCSELs (11 /spl mu/m oxide aperture) with an emission wavelength of 1287 nm have a threshold current of 3 mA and produce 1 mW of output power at 20/spl deg/C. The maximum operating temperature is 95/spl deg/C. Emission at 1303 nm with 1 mW of output power and a threshold current of 7 mA has been observed from VCSELs with a larger detuning between the gain peak and the cavity resonance.