Flip-chip bonded 0.85-/spl mu/m bottom-emitting vertical-cavity laser array on an AlGaAs substrate

We report high-performance 0.85-/spl mu/m bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) on an AlGaAs substrate with 2.1 mA threshold current density 4.2 mW maximum output power, 11.7% power conversion efficiency and a maximum operating temperature of 130/spl deg/C. We also demonstrate a flip-chip bonded 0.85-/spl mu/m bottom-emitting VCSEL array, and confirm all pixels across the 8/spl times/8 VCSEL array operate at a f/sub 3/ dB bandwidth of 2.6 GHz at only 4.2 mA.     

High-performance 1.3 /spl mu/m InGaAs vertical cavity surface emitting lasers

A report is presented on high-performance InGaAs/GaAs double quantum well vertical cavity surface emitting lasers (VCSELs) with record long emission wavelengths up to 1300 nm. Due to a large gain-cavity detuning these VCSELs show excellent temperature performance with very stable threshold current and output power characteristics. For 1.27 /spl mu/m singlemode devices the threshold current is found to decrease from 2 to 1 mA between 10 and 90/spl deg/C, while the peak output power only drops from 1 to 0.6 mW. Large-area 1300 nm VCSELs show multimode output power close to 3 mW.     

"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.     

Fabrication and Characteristics of high-speed oxide-confined VCSELs using InGaAsP-InGaP strain-compensated MQWs

This paper presents the fabrication and characteristics of high-performance 850-nm InGaAsP-InGaP strain-compensated multiple-quantum-well (MQW) vertical-cavity surface-emitting lasers (VCSELs). The InGaAsP-InGaP MQW's composition was optimized through theoretical calculations, and the growth condition was optimized using photoluminescence. These VCSELs exhibit superior performance with characteristics threshold currents /spl sim/0.4 mA and slope efficiencies /spl sim/0.6 mW/mA. The threshold current change with temperature is less than 0.2 mA, and the slope efficiency drops less than /spl sim/30% when the substrate temperature is raised from room temperature to 85/spl deg/C. A high modulation bandwidth of 14.5 GHz and a modulation current efficiency factor of 11.6 GHz/(mA)/sup 1/2/ are demonstrated. The authors have accumulated life test data up to 1000 h at 70/spl deg/C/8 mA.     

650-nm vertical-cavity surface-emitting lasers: laser properties and reliability investigations

650-nm AlGaInP-AlGaAs-based oxide-confined VCSELs are investigated in dependence on the current aperture size. VCSELs with small aperture (a=5 /spl mu/m) have a maximum continuous-wave (CW) output power of about 1 mW at room temperature. They reach higher operating temperatures (T/sub max/=55/spl deg/C), have narrower beam profiles, less transverse modes, and a higher side mode suppression compared to large aperture VCSELs (a>13 /spl mu/m). The latter devices emit a CW-output power P=3 mW at 20/spl deg/C. Reliability tests of 655-nm devices show at 20/spl deg/C an output power of P/spl ap/0.4 mW over more than 1000 h and at 40/spl deg/C P/spl ap/0.1 mW over 500 h.     

Single-mode monolithic quantum-dot VCSEL in 1.3 /spl mu/m with sidemode suppression ratio over 30 dB

We present monolithic quantum-dot vertical-cavity surface-emitting lasers (QD VCSELs) operating in the 1.3-/spl mu/m optical communication wavelength. The QD VCSELs have adapted fully doped structure on GaAs substrate. The output power is /spl sim/330 /spl mu/W with slope efficiency of 0.18 W/A at room temperature. Single-mode operation was obtained with a sidemode suppression ratio of >30 dB. The modulation bandwidth and eye diagram in 2.5 Gb/s was also presented.     

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.     

High-power fundamental-mode and polarisation stabilised VCSELs using sub-wavelength surface grating

A monolithic technique is presented for simultaneous mode and polarisation control in oxide-confined VCSELs using a locally etched sub-wavelength surface grating. A single-fundamental-mode emission with an SMSR >30 dB and an OPSR /spl sim/20 dB is achieved over the entire operational current range, with a maximum output power of 4.1 mW.     

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.     

Long-wavelength InAlGaAs VCSELs with Al/sub 2/O/sub 3/ embedded current-confinement apertures

Long-wavelength InAlGaAs VCSELs with Al/sub 2/O/sub 3/ embedded current-confinement structures are reported. Using atomic layer deposition, the current confinement structures are fabricated by depositing Al/sub 2/O/sub 3/ on airgap surfaces of undercut apertures, which are formed by laterally etching the active region. 1.57 /spl mu/m VCSELs showing an output power of over 1 mW and direct modulation characteristics at 4 Gbit/s are reported using these current-confinement apertures.     

Efficient long wavelength AlGaInAs vertical-cavity surface-emitting lasers for coarse WDM applications over multimode fibre

Novel AlGaInAs VCSELs have been fabricated for coarse wavelength division multiplexing over multimode fibre at wavelengths of 1275, 1300, 1325 and 1350 nm. Efficient monomode lasing (>2.0 mW power, 31% efficiency) and multimode lasing (up to 9 mW power, 39% efficiency) are reported, along with 3.125 and 10 Gbit/s modulation to 85/spl deg/C.     

Vertical-cavity surface-emitting lasers based on submonolayer InGaAs quantum dots

Molecular beam epitaxy-grown 0.98-/spl mu/m vertical-cavity surface-emitting lasers (VCSELs) with a three-stack submonolayer (SML) InGaAs quantum-dot (QD) active region and fully doped Al/sub x/Ga/sub 1-x/As-GaAs DBRs was studied. Large-aperture VCSELs demonstrated internal optical losses less than 0.1% per one pass. Single-mode operation throughout the whole current range was observed for SML QD VCSELs with the tapered oxide apertures diameter less than 2 /spl mu/m. Devices with 3-/spl mu/m tapered-aperture showed high single-mode output power of 4 mW and external quantum efficiency of 68% at room temperature.     

A low-voltage 40-GHz complementary VCO with 15% frequency tuning range in SOI CMOS technology

The design of a low-voltage 40-GHz complementary voltage-controlled oscillator (VCO) with 15% frequency tuning range fabricated in 0.13-/spl mu/m partially depleted silicon-on-insulator (SOI) CMOS technology is reported. Technological advantages of SOI over bulk CMOS are demonstrated, and the accumulation MOS (AMOS) varactor limitations on frequency tuning range are addressed. At 1.5-V supply, the VCO core and each output buffer consumes 11.25 mW and 3 mW of power, respectively. The measured phase noise at 40-GHz is -109.73 dBc/Hz at 4-MHz offset from the carrier, and the output power is -8 dBm. VCO performance using high resistivity substrate (/spl sim/300-/spl Omega//spl middot/cm) has the same frequency tuning range but 2 dB better phase noise compared with using low resistivity substrate (10 /spl Omega//spl middot/cm). The VCO occupies a chip area of only 100 /spl mu/m by 100 /spl mu/m (excluding pads).     

Electrically pumped room temperature CW VCSELs with 2.3 /spl mu/m emission wavelength

Continuous wave (CW) operation at room temperature of electrically pumped InGaAlAs/InP vertical-cavity surface-emitting lasers (VCSELs) at emission wavelengths as high as 2.3 /spl mu/m is demonstrated for the first time. Devices with 15 /spl mu/m active region diameter show a maximum output power of 0.75 mW at 20/spl deg/C and a maximum CW operating temperature of 45/spl deg/C.     

Integrated semiconductor vertical-cavity surface-emitting lasers and PIN photodetectors for biomedical fluorescence sensing

Vertical-cavity surface-emitting lasers (VCSELs), optical emission filters, and PIN photodetectors were fabricated as part of a monolithically integrated near-infrared fluorescence detection system. The integration of these micro-fabricated components with micro-arrays, flow channel arrays, and biochips can drastically reduce cost and enable parallel sensing architectures. An optoelectronic design is presented that integrates VCSELs, optical filters, and photodetectors through a modification to a typical VCSEL structure. System designs were simulated and compared, leading to several innovative approaches for integrated sensors. The laser and detector modules were characterized independently and subsequently integrated to form a complete sensor. VCSELs with oxidation apertures measuring 4, 7, 14, and 20 /spl mu/m showed a lasing wavelength of /spl lambda/=773 nm, threshold current densities from 6400 to 1300 A/spl middot/cm/sup -2/, and maximum output powers of 0.6-4 mW, with transverse single-mode and multimode operation. PIN photodetectors were fabricated with integrated emission filters. Quantum efficiencies above 85% were observed with a dark current of 500 fA/(mm detector diameter). Complete sensor units were tested and near-infrared fluorescent molecules (IR-800) were detected. A theoretical detection limit of 10/sup 5/ fluorophores//spl mu/m/sup 2/ was determined. The compact parallel architecture, high-power laser, and low-noise photodetector make this sensor a good candidate for biomedical fluorescence-based sensing applications.     

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.     

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.     

Suppression of higher-order transverse modes in vertical-cavity lasers by impurity-induced disordering

Etched pillar, bottom emitting vertical cavity surface emitting lasers (VCSELs) employing a zinc diffused and disordered spatial mode filter are fabricated and tested. The filters successfully suppress lasing of higher order transverse modes in VCSELs with diameters greater than 11 /spl mu/m, while obtaining output powers of up to 1.5 mW with threshold currents as low as 2.7 mA. Emission is entirely single mode, with mode suppression ratio greater than 25 dB up to the highest output power levels.     

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.     

1.5-/spl mu/m InGaAsP-InP slab-coupled optical waveguide lasers

We report the demonstration of high-power semiconductor slab-coupled optical waveguide lasers (SCOWLs) operating at a wavelength of 1.5 /spl mu/m. The lasers operate with large (4/spl times/8 /spl mu/m diameter) fundamental mode and produce output power in excess of 800 mW. These structures have very low loss (/spl sim/0.5 cm/sup -1/) enabling centimeter-long devices for efficient heat removal. The large fundamental mode allows 55% butt-coupling efficiency to standard optical fiber (SMF-28). Comparisons are made between SCOWL structures having nominal 4- and 5-/spl mu/m-thick waveguides.