0.85-/spl mu/m vertical-cavity surface-emitting laser diode arrays grown on p-type GaAs substrate

We have fabricated the first room-temperature (RT) continuous-wave (CW) 0.85-/spl mu/m 8/spl times/8 bottom-emitting vertical-cavity surface-emitting AlGaAs-GaAs DBR QW laser diode (VCSEL) arrays on a p-type GaAs substrate, which are applicable to optical interconnection. The laser characteristics are slightly inferior to those of VCSEL arrays made on n-type GaAs substrate with the same reflectivity, but exhibit for better array uniformity of threshold current density than previously reported. Such devices are applicable to N-MOS integration.     

"Anti" up the aperture [antiguided VCSEL structures]

Coupled vertical cavity surface-emitting laser (VCSEL) arrays are an attractive means to increase the coherent output power of VCSELs. Single-mode VCSELs, with output powers greater than 10 mW, would be useful as telecommunication transmitters /spl lambda/=1.3-1.55 /spl mu/m) or sources for optical interconnects. Commercially available single-mode VCSELs, even at shorter wavelengths /spl lambda/=0.85 /spl mu/m), are generally limited to a few milliwatts of output power. The conventional VCSEL structure incorporates a built-in positive-index waveguide, designed to support a single fundamental mode. Promising results in the 3-5 mW range (/spl lambda/=0.85 /spl mu/m) have been obtained from wet-oxidized, positive-index-guided VCSELs with small emission apertures (less than 3.5 /spl mu/m-dia). The small aperture size leads to a high electrical resistance and high current density, which can impact device reliability. By contrast, antiguided VCSEL structures have shown promise for achieving larger aperture single-mode operation. To obtain high single-mode powers with a larger emitting aperture, the use of a negative-index guide (antiguide) is beneficial. This paper discusses antiguided structures and some of their advantages when incorporated in 2-D VCSEL array structures.     

Development of bottom-emitting 1300-nm vertical-cavity surface-emitting lasers

We present experimental results on the development of bottom-emitting GaInNAs vertical-cavity surface-emitting lasers (VCSELs) operating at wavelengths near 1300 nm. This development effort is based on the modification of oxide-apertured top-emitting structures to allow emission through the GaAs substrate. Similar device performance was seen in both the top- and bottom-emitting structures. Single-mode output powers (adjusted for substrate absorption) of /spl sim/0.75 mW, with threshold currents of 1.3 mA, were achieved with /spl sim/3.5-/spl mu/m aperture diameters. Larger multimode devices exhibited a maximum adjusted output power of 2.2 mW. To the best of our knowledge, these are the first bottom-emitting flip-chip compatible 1300-nm VCSELs fabricated with GaInNAs-GaAs active regions.     

Low-threshold operation of 1.34-/spl mu/m GaInNAs VCSEL grown by MOVPE

Low-threshold operation was demonstrated for a 1.34-/spl mu/m vertical-cavity surface-emitting laser (VCSEL) with GaInNAs quantum wells (QWs) grown by metal-organic vapor-phase epitaxy. Optimizing the growth conditions and QW structure of the GaInNAs active layers resulted in edge-emitting lasers that oscillated with low threshold current densities of 0.87 kA/cm/sup 2/ at 1.34 /spl mu/m and 1.1 kA/cm/sup 2/ at 1.38 /spl mu/m, respectively. The VCSEL had a low threshold current of 2.8 mA and a lasing wavelength of 1.342 /spl mu/m at room temperature and operated up to 60/spl deg/C.     

Continuous-wave operation up to 36/spl deg/C of 1.3-/spl mu/m GaInAsP-InP vertical-cavity surface-emitting lasers

We introduced ion-beam assisted deposition in order to improve the quality of Al/sub 2/O/sub 3/ and SiO/sub 2/, which were used as part of the mirrors of 1.3-/spl mu/m GaInAsP-InP vertical-cavity surface-emitting lasers (VCSELs). The refractive index of Al/sub 2/O/sub 3/ was improved to 1.63 from 1.56 and the one of SiO/sub 2/ increased to 1.47 from 1.45. Low-threshold room-temperature continuous-wave (CW) operation of 1.3-/spl mu/m VCSEL with the improved mirrors was demonstrated. The threshold current was 2.4 mA at 20/spl deg/C. The CW operating temperature was raised to 36/spl deg/C, which is a record high temperature for 1.3-/spl mu/m VCSEL.     

High-yield flip-chip bonding and packaging of low-threshold VCSEL arrays on sapphire substrates

Oxide-confined top-emitting 850 nm and bottom-emitting 980 nm vertical-cavity surface-emitting laser (VCSEL) 8/spl times/8 arrays were designed and fabricated for applications of optical interconnects. The arrays were flip-chip bonded onto sapphire substrates that contain complimentary metal-oxide-semiconductor (CMOS) driver and fan-out circuitries. The off-sited bonding contacts and minimized bonding force produced very high yield of the hybridization process without causing damage to the VCSEL mesas. The hybridized devices were further mounted either on printed circuit board (PCB) or in 68-pin pin-grid-array (PGA) packages. The transparent sapphire substrate allowed optical outputs from the top-emitting VCSEL arrays to transmit directly through without additional substrate removal procedure. Lasing thresholds below 250 /spl mu/A for 850 nm VCSELs and 800 /spl mu/A for 980 nm VCSEL were found at room temperature. The oxide confinement apertures of VCSELs were measured to be around 6 /spl mu/m in diameter. High-speed data transmission demonstrated a bandwidth of up to 1 Gbits/s per channel for these hybridized VCSEL transmitters.     

Study on high-temperature performances of 1.3-/spl mu/m InGaAsP-InP strained multiquantum-well buried-heterostructure lasers

Stripe-width and cavity length dependencies of high-temperature performances of 1.3-/spl mu/m InGaAsP-InP well-designed buried-heterostructure strained multiquantum-well (MQW) lasers were investigated. The threshold currents as low as 4.5/10.5 mA and slope efficiencies as high as 0.48/0.42 mW/mA at 25/spl deg/C/85/spl deg/C were obtained in the MQW lasers with 1.5-/spl mu/m width, 250-/spl mu/m length, and 0.3/0.85 facet reflectivity. With temperature increasing from 25/spl deg/C to 85/spl deg/C, the MQW lasers exhibited lower output power degradation, the minimum value was 1.78 dB at an operation current of 45 mA. The MQW lasers were suitable for application in optical access networks.     

Performance analysis of 10-/spl mu/m-thick VCSEL array in fully embedded board level guided-wave optoelectronic interconnects

We introduce a simple and effective heat sink structure for thin-film vertical cavity surface emitting lasers (VCSELs) in fully embedded board level guided-wave interconnects. A 50% quantum efficiency increase is experimentally confirmed for the 10-/spl mu/m thin-film VCSELs. The thermal resistance of a 1 /spl times/ 12 embedded thin-film VCSEL array in printed circuit board (PCB) is further analyzed. The experimental results show an excellent match with the simulated results. The 10-/spl mu/m-thick VCSEL had the lowest thermal resistance and the highest differential efficiency compared to 250-, 200-, 150-, and 100-/spl mu/m-thick VCSELs. A substrate removed VCSEL can be used in fully embedded board level optical interconnects without special cooling techniques.     

Continuously tunable 1.55-/spl mu/m VCSEL implemented by precisely curved dielectric top DBR involving tailored stress

We present an optically pumped and continuously tunable 1.55-/spl mu/m vertical-cavity surface-emitting laser (VCSEL). The device shows 26-nm spectral tuning range, 400-/spl mu/W maximum output power, and 57-dBm side-mode suppression ratio. The VCSEL is implemented using a two-chip concept. The movable top mirror membrane is precisely designed to obtain a tailored air-gap length (L'=16 /spl mu/m) and a radius of curvature (ROC=4.5mm) in order to efficiently support the fundamental optical mode of the plane-concave resonator. It consists of a distributed Bragg reflector (DBR) with periodic, differently stressed silicon nitride and silicon dioxide multilayers implemented by plasma-enhanced chemical vapor deposition. The lower InP-based part, comprising the InP-InGaAsP bottom DBR and the active region, is grown monolithically using metal-organic vapor phase epitaxy.     

Long-wavelength In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As large-area avalanche photodiodes and arrays

Large-area (500-/spl mu/m diameter) mesa-structure In/sub 0.53/Ga/sub 0.47/As-In/sub 0.52/Al/sub 0.48/As avalanche photodiodes (APDs) are reported. The dark current density was /spl sim/2.5/spl times/10/sup -2/ nA//spl mu/m/sup 2/ at 90% of breakdown; low surface leakage current density (/spl sim/4.2 pA//spl mu/m) was achieved with wet chemical etching and SiO/sub 2/ passivation. An 18 /spl times/ 18 APD array with uniform distributions of breakdown voltage, dark current, and multiplication gain has also been demonstrated. The APDs in the array achieved 3-dB bandwidth of /spl sim/8 GHz at low gain and a gain-bandwidth product of /spl sim/120 GHz.     

Low-threshold high-T/sub 0/ 1.3-/spl mu/m InAs quantum-dot lasers due to p-type modulation doping of the active region

P-type doping is used to demonstrate high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot lasers. A 5-/spl mu/m-wide oxide confined stripe laser with a 700-/spl mu/m-long cavity exhibits a pulsed T/sub 0/ = 213 K (196 K CW) from 0/spl deg/C to 80/spl deg/C. At room temperature, the devices have a CW threshold current of /spl sim/4.4 mA with an output power over 15 mW. The threshold at 100/spl deg/C is 8.4 mA with an output power over 8 mW.     

AlGaAs vertical-cavity surface-emitting laser responses to 4.5-MeV proton irradiation

We have irradiated single- and multimode AlGaAs vertical-cavity surface-emitting laser (VCSEL) arrays operating at a nominal wavelength of 780 nm with 4.5-MeV protons and doses ranging from 10 to 30 Mrad in the active region. We observed a peak power reduction of about 2% per Mrad in the 14-/spl mu/m aperture, multimode VCSELs. Single-mode VCSELs having an aperture of 6 /spl mu/m exhibited a smaller peak power reduction of 0.4%-1% per Mrad. A slight shift in the current threshold was observed only for the multimode VCSELs at dose levels above 10 Mrad. First results indicate a reduced VCSEL peak laser power output that is dominated by a temperature shift caused by the radiation induced increase in resistive heating. In contrast, the power reduction in edge-emitting lasers is dominated by the enhanced radiation induced nonradiative recombination rate. The VCSEL irradiation was performed with a focused ion micro beam that was rastered over the device surface, ensuring a very uniform exposure of a single device in the array.     

Continuous-wave operation of GaInAsSb-GaSb type-II ridge waveguide lasers emitting at 2.8 /spl mu/m

We have realized compressively strained GaInAsSb-GaSb type-II double quantum-well lasers with an emission wavelength of 2.8 /spl mu/m. Using broad area devices, an internal absorption of 9.8 cm/sup -1/ and an internal quantum efficiency of 0.57 is determined. For the increase of the threshold current with temperature, a T/sub 0/ of 44 K is obtained. Narrow ridge waveguide lasers show continuous-wave laser operation at temperatures up to 45 /spl deg/C, with room-temperature (RT) threshold current of 37 mA. At RT, the maximum optical output power per facet of an uncoated 800/spl times/7 /spl mu/m/sup 2/ ridge waveguide laser exceeds 8 mW.     

Arrays of AC-excited, silicon microdischarge devices as large as 40 000 (200/spl times/200) pixels: electrical and optical characteristics for operation in neon

Electrical characteristics of arrays of (50 /spl mu/m)/sup 2/ Si microplasma devices operating in 500-900 Torr of Ne are presented. Arrays as large as 200/spl times/200 pixels have been AC-excited at frequencies of 5-20 kHz and all exhibit reproducible ignition voltages and lifetimes. At 700 Torr, the power consumed per pixel for a 200/spl times/200 pixel array is 85/spl plusmn/2 /spl mu/W, 190/spl plusmn/2 /spl mu/W, and 290/spl plusmn/2 /spl mu/W for excitation frequencies of 5, 10, and 15 kHz, respectively, and 5.5, 12.0, and 17.8 mA, respectively, of total current (RMS) drawn by the array.     

A 35 ns 2K /spl times/ 8 HMOS static RAM

This paper describes the circuit design and process techniques used to produce a 35-ns 2K /spl times/ 8 HMOS static RAM aimed at future high-end microprocessor applications. The circuit design uses predecoding of the row and column decoder/driver circuits to reduce active power, address-transition detection schemes to equalize internal nodes, and dynamic depletion-mode configurations for increased drive and speed. The technology is 2.5-3.0-/spl mu/m design rule HMOS employing an L/SUB eff/ of 1.7 /spl mu/m, t/SUB ox/=400 /spl Aring/, double-poly resistor loads, RIE and plasma etching, and wafer-stepper lithography. Using these techniques an access time of 35 ns, dc active power of 65 mA, standby power of 14 mA, and die size of 37.5K mil/SUP 2/ has been achieved. The cell size is 728 /spl mu/m/SUP 2/.     

High-power vertical cavity surface emitting laser with good performances

Fabrication and performance of a high-power bottom-emitting InGaAs/GaAsP vertical cavity surface emitting laser with 430 /spl mu/m diameter are described. The device realises the maximum room temperature CW output power 1.52 W at 987.6 nm with FWHM 0.8 nm. The far-field divergence angle is below 20/spl deg/. Reliability test shows at 70/spl deg/C an output power 0.35 W over 500 h.     

High-power vertical-cavity surface-emitting laser with an extra Au layer

We report the performance of a high-power vertical-cavity surface-emitting laser (VCSEL) with an extra Au layer. By using the extra Au layer, the far-field divergence angle from a 600-/spl mu/m diameter VCSEL device is suppressed from 30/spl deg/ to 15/spl deg/, and no strong sidelobe is observed in far-field pattern. There is a slight drop in optical output power due to the introduction of the extra Au layer. By improving the device packaging method, the VCSEL device produces the maximum continuous-wave optical output power of 1.95 W with lasing wavelength of 981.5 nm. The aging test is carried out under constant current mode at 60/spl deg/C, and the preliminary result shows that the total degradation of output power is less than 10% after 800 h.     

Plug-in type 1.3-/spl mu/m fiber amplifier module for rack-mounted shelves

We have successfully developed a plug-in type PDFA module for rack mounted shelves which is assembled on a printed-board. In this module, we use a newly developed Pr/sup 3+/-doped high-NA PbF/sub 2//InF/sub 3/-based fluoride fiber and wavelength stabilized 1.017-/spl mu/m laser diodes (LDs). We have obtained a small-signal gain of 24 dB and a noise figure of 6.6 dB at 1.30 /spl mu/m with an LD drive current of 240 mA/spl times/2. We achieved an output power of 10 dBm with a signal input power of 0 dBm. The total power consumption of this module, including that of a Peltier cooler, was 3.5 W when the LD drive current was 240 mA/spl times/2.     

Millimeter-wave high-power 0.25-/spl mu/m gate-length AlGaN/GaN HEMTs on SiC substrates

Reports on the CW power performance at 20 and 30 GHz of 0.25 /spl mu/m /spl times/ 100 /spl mu/m AlGaN/GaN high electron mobility transistors (HEMTs) grown by MOCVD on semi-insulating SiC substrates. The devices exhibited current density of 1300 mA/mm, peak dc extrinsic transconductance of 275 mS/mm, unity current gain cutoff (f/sub T/) of 65 GHz, and maximum frequency of oscillation (f/sub max/) of 110 GHz. Saturated output power at 20 GHz was 6.4 W/mm with 16% power added efficiency (PAE), and output power at 1-dB compression at 30 GHz was 4.0 W/mm with 20% PAE. This is the highest power reported for 0.25-/spl mu/m gate-length devices at 20 GHz, and the 30 GHz results represent the highest frequency power data published to date on GaN-based devices.     

DC and RF characteristics of E-mode Ga/sub 0.51/In/sub 0.49/P-In/sub 0.15/Ga/sub 0.85/As pseudomorphic HEMTs

The DC and RF characteristics of Ga/sub 0.49/In/sub 0.51/P-In/sub 0.15/Ga/sub 0.85/As enhancement- mode pseudomorphic HEMTs (pHEMTs) are reported for the first time. The transistor has a gate length of 0.8 /spl mu/m and a gate width of 200 /spl mu/m. It is found that the device can be operated with gate voltage up to 1.6 V, which corresponds to a high drain-source current (I/sub DS/) of 340 mA/mm when the drain-source voltage (V/sub DS/) is 4.0 V. The measured maximum transconductance, current gain cut-off frequency, and maximum oscillation frequency are 255.2 mS/mm, 20.6 GHz, and 40 GHz, respectively. When this device is operated at 1.9 GHz under class-AB bias condition, a 14.7-dBm (148.6 mW/mm) saturated power with a power-added efficiency of 50% is achieved when the drain voltage is 3.5 V. The measured F/sub min/ is 0.74 dB under I/sub DS/=15 mA and V/sub DS/=2 V.