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.     

2.5-mW single-mode operation of 1.55-/spl mu/m buried tunnel junction VCSELs

We present 1.55-/spl mu/m wavelength buried tunnel junction InGaAlAs-InP vertical-cavity surface-emitting lasers with low threshold current and high efficiency. An improved mirror design is accomplished with high-reflective low-loss epitaxial InGaAlAs-InAlAs and hybrid dielectric CaF/sub 2/-ZnS-Au layer stacks, respectively. Lasers with aperture diameters of only around 5 /spl mu/m exhibit continuous-wave single-mode output powers at room temperature well beyond 2 mW. Threshold voltages and series resistances as low as 0.9 V and 30-40 /spl Omega/ have been measured. The spectral behavior shows excellent performance over the relevant current and temperature range.     

Very Wide Hysteresis Cycles in 1550-nm VCSELs Subject to Orthogonal Optical Injection

A first experimental observation of three different types of frequency-induced polarization bistabilities in 1550-nm single transverse and polarization mode vertical-cavity surface-emitting lasers (VCSELs) subject to orthogonal optical injection is described. The hysteresis width of the bistable region that appears at longer wavelegth detunings increases as the injected power or the VCSEL current increases. Very large hysteresis widths are obtained. These widths are more than seven times larger than previously reported widths.      

1.55-/spl mu/m optically pumped wafer-fused tunable VCSELs with 32-nm tuning range

We demonstrate widely tunable InAlGaAs-InP-AlGaAs-GaAs optically pumped vertical-cavity surface-emitting lasers operating in the 1.55-/spl mu/m waveband. The tuning range of 32 nm is achieved by applying a low tuning voltage of 4 V. Maximum single-mode output power of 2 mW with less than 1.5-dB power variation over the whole tuning range and side-mode suppression ratio in excess of 30 dB have been obtained.     

1.5 ?m phase-shifted DFB lasers for single-mode operation

Fabrication and single-mode laser oscillation were demonstrated for modified DFB lasers where the phase of the corrugations was shifted at the centre by a quarter guided-wavelength and which, in principle, provided a resonance at the Bragg wavelength and stable single-mode oscillation. Phase-shifted corrugations were fabricated using electron-beam lithography.     

Silicon oxide-planarized single-mode 850-nm VCSELs with TO package for 10 Gb/s data transmission

In this letter, we report on an alternative method to fabricate a high-efficiency planar-type oxide-confined 850-nm vertical-cavity surface-emitting lasers (VCSELs). The planarized process of VCSELs was to use the silicon oxide as the buried layer. As a result, these devices with an oxidized aperture of 3 /spl mu/m in diameter exhibit a single-transverse mode behavior throughout the operation current range. In addition, the static characteristics of VCSELs at 300 K include a threshold current of 0.52mA corresponding to a threshold voltage of 2.2 V, a maximum single transverse-mode light output power of 1.13 mW at 4.5 mA, and an external differential quantum efficiency of 35%. On the other hand, this TO-packaged planar-type 850-nm VCSEL for back-to-back test shows a wide open along with symmetric eye diagram and could also pass the 10 Gb/s mask as operating at 10.3 Gb/s and 4 mA. Furthermore, the VCSEL can still keep the eye diagram open and symmetric after the 66-m multi-mode fiber transmission and has a power penalty of 6.6 dB because of fiber dispersion for 10.3 Gb/s data rate at a bit error rate of 10/sup -11/. These results confirm the excellent high-speed performance of SiO/sub x/-planarized VCSELs as compared to the polyimide-planarized VCSELs.     

面向长距离通讯1550 nm垂直腔面发射激光器的研究

采用InP基衬底设计并制备了1550 nm垂直腔面发射激光器。采用混合镜面布拉格发射镜,其中顶部采用4.5对硅和二氧化硅的介电布拉格反射镜,同时采用隧道结的方式降低p层载流子吸收。制备出阈值电流在20 mA,室温直流下输出光功率为7 μW,激射波长为1554 nm,激射谱半高宽为3 nm的垂直腔面发射激光器。     

Analog Modulation of 650-nm VCSELs

Small-signal properties of 650-nm vertical-cavity surface-emitting lasers (VCSELs) with different oxide aperture sizes were measured. A small diameter VCSEL of 3.5 /spl mu/m has a maximum resonance frequency of 5.7 GHz. The photon density determines the maximum resonance frequency. Modeling also indicates higher photon densities in the small VCSEL due to better thermal behavior.     

Wide temperature operation of 40-Gb/s 1550-nm electroabsorption modulated lasers

Electroabsorption modulated lasers (EMLs) exploiting the quantum confined Stark effect need thermoelectric coolers to achieve stable output power levels and dynamic extinction ratios. Temperature-independent operation is reported between 20/spl deg/C and 70/spl deg/C for InGaAlAs-InP-based monolithically integrated 1550-nm EMLs exploiting a shared active area at 40 Gb/s by actively controlling the electroabsorption modulator bias voltage. Dynamic extinction ratios of at least 8 dB and fiber-coupled mean modulated optical power of at least 0.85 mW are obtained over the mentioned temperature range.     

40-mW 650-nm distributed feedback lasers

Using a buried second-order grating in a single-mode GaInP-AlInP laser structure, we obtain single-spatial- and longitudinal-mode operation at 652 nm. Over 40-mW continuous wave (CW) is obtained at room temperature (RT), with efficiencies and far fields comparable to conventional Fabry-Perot lasers. The devices are continuously tunable with current and temperature and exhibit no mode hops, and thus should be useful for applications where short wavelength and longitudinal mode stability is required, such as spectroscopy, interferometry, or optical storage     

Performance comparison of 850-nm and 1550-nm VCSELs exploiting OOK,OFDM, and 4-PAM over SMF/MMF links for low-cost optical interconnects

We experimentally compare the performance of two commercially available vertical-cavity surface-emitting laser diodes (VCSELs), a multi-mode 850-nm and a single-mode 1550-nm, exploiting on–off keying/direct detection (OOK/DD), and orthogonal frequency division multiplexed (OFDM) quadrature phase-shift keying (QPSK)/16-ary quadrature amplitude modulation (16QAM) with direct detection, over SMF (100 m and 5 km) and MMF (100 m and 1 km) short-range links, for their potential application in low-cost rack-to-rack optical interconnects. Moreover, we assess the performance of quaternary-pulse amplitude modulation (4-PAM), for the 1550-nm transmitter over SMF and MMF links and we compare it to the data-rate equivalent NRZ-OOK. The extensive performance comparison under various transmission scenarios shows the superiority of 1550-nm single-mode VCSEL compared to its multi-mode 850-nm counterpart. Moreover, OFDM/DD and 4-PAM in conjunction with low-cost, inexpensive VCSELs as transmitters prove to be an enabling technology for next-generation WDM, point-to-point, short-reach, SMF/MMF optical interconnects and potential candidates to substitute NRZ-OOK. Nevertheless, the sensitivity requirements are higher in that case, whereas these advanced, spectrally-efficient modulation formats become severely degraded when transmitted over MMF links, especially, when employing the inexpensive 850-nm VCSELs as transmitter. Finally, we compare the performance of the point-to-point links under investigation to the performance of a semiconductor optical amplifier (SOA)- based, scalable permutation switch fabric, the Optical Shared MemOry Supercomputer Interconnect System (OSMOSIS).     

400-mW single-frequency 660-nm semiconductor laser

Using an angled-grating broad-area structure in GaInP-AlInP material system, we obtain single spatial and longitudinal-mode operation at 660 nm. The grating stabilizes the mode to deliver over 400-mW continuous-wave at room temperature from a 60-μm-wide stripe. This is about ten times higher than conventional distributed-feedback power output levels, and is the highest single-frequency power from a monolithic semiconductor device in this wavelength range. These devices should be useful for single-mode-fiber coupling and in applications where high-wavelength stability is required, such as spectroscopy, interferometry, or metrology     

Electrical design optimization of single-mode tunnel-junction-based long-wavelength VCSELs

We present principles for tunnel-junction (TJ) design optimization for use in intracavity contacted long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs). Using the WKB approximation, we find that layer thicknesses of 10 nm on the n++ side and 10 nm on the p++ side are large enough to maximize quantum tunneling probability and small enough to yield low optical free-carrier absorption loss. We also conjecture that our experimental test structures and actual devices have far lower active acceptor concentration than we expect based on an analytical model. Finally, we calculate the necessary doping levels to enable single-mode operation of LW-VCSELs and incorporate these conditions into a complete optimized model of our VCSELs. Based on optimal I-V curves, we can expect an increase in single-mode output power from 2 to 3.5 mW.     

High-power 1320-nm wafer-bonded VCSELs with tunnel junctions

A new long-wavelength vertical-cavity surface-emitting laser structure is described that utilizes AlGaAs-GaAs mirrors bonded to AlInGaAs-InP quantum wells with an intracavity buried tunnel junction. This structure offers complete wavelength flexibility in the 1250-1650 nm fiber communication bands and reduces the high free-carrier losses and bonded junction voltage drops in previous devices. The intracavity contacts electrically bypass the bonded junctions to reduce threshold voltage. N-type current spreading layers and undoped AlGaAs mirrors minimize optical losses. This has enabled 134/spl deg/C maximum continuous-wave lasing temperature, 2-mW room-temperature continuous-wave single-mode power, and 1-mW single-mode power at 80/spl deg/C, in various devices in the 1310-1340 nm wavelength range.     

Low thermal resistance high-speed top-emitting 980-nm VCSELs

Increasing copper plated heatsink radii from 0 to 4 /spl mu/m greater than the mesa in vertical-cavity surface-emitting lasers (VCSELs) reduced the measured thermal resistance for a range of device sizes to values 50% lower than previously reported over a range of device sizes. For a 9-/spl mu/m diameter oxide aperture, the larger heatsink increases output power and bandwidth by 131% and 40%, respectively. The lasers exhibit a 3-dB modulation frequency bandwidth up to 9.8 GHz at 10.5 kA/cm/sup 2/. The functional dependence of thermal resistance on oxide aperture diameter indicates the importance of lateral heat flow to mesa sidewalls.     

1550-nm volume holography for optical communication devices

The two-lambda method can provide a strategic approach to implement all-optical devices for communication wavelength division multiplexing (WDM) signal processing based on volume holography. By writing holograms at 488 nm in LiNbO/sub 3/:Fe and reading them in the third window of optical communication systems (1550 nm), the feasibility of WDM demultiplexers and holographic memories for digital bytes is here demonstrated.     

345-mW 1836-nm single-frequency DFB fiber laser MOPA

We demonstrate an in-band-pumped continuous-wave single-frequency distributed-feedback (DFB) fiber laser emitting at a wavelength of 1836 nm with an output power of /spl sim/5 mW. The laser is subsequently amplified to 345 mW using a master-oscillator power amplifier configuration. To the best of the authors' knowledge, this is the first report of a Tm-co-doped single-frequency DFB fiber laser that is in-band pumped at 1565 nm. The laser is confirmed to operate in a single mode, using a scanning Fabry-Pe/spl acute/rot interferometer.     

Wavelength conversion in a 1550-nm multifrequency laser

Wavelength conversion of input signals at data rates of 622 and to 1250 Mb/s was as demonstrated using an integrated multifrequency laser having 8 channels with 1.6-nm channel spacing.     

Highly reliable 60/spl deg/C 50-mW operation of 650-nm band window-mirror laser diodes

High-power GaInP QW laser diodes with a window-mirror-structure lasing at a wavelength of around 650 nm have been fabricated. The maximum light output power over 150 mW has been realized without optical mirror damage. In addition, the laser shows the fundamental-mode-operation at 50 mW and the dynamic characteristics sufficient for recordable digital versatile disc (DVD) applications. The lasers have been operating for 2000 h under the condition of CW, 50 mW, and 60/spl deg/C, for the first time.     

1.5 ?m phase adjusted active distributed reflector laser for complete dynamic single-mode operation

1.5 ?m GaInAsP/InP phase adjusted active distributed reflector laser was proposed and fabricated for stable dynamic single-mode operation. Room-temperature CW operation was obtained with the threshold current of 62 mA. Oscillation at the Bragg wavelength was confirmed experimentally.