Wideband quantum-dash-in-well superluminescent diode at 1.6 /spl mu/m

We demonstrate broadband superluminescent diode at /spl sim/1.6-/spl mu/m peak emission wavelength using InAs-InAlGaAs quantum-dash-in-well structure on InP substrate. The fabricated device exhibits the close-to-Gaussian emission with a bandwidth of up to 140 nm. The device produces a low spectrum ripple of 0.3dB and an integrated power of 1.7 mW with the corresponding bandwith of 110 nm measured at 20 /spl deg/C under 8 kA/cm/sup 2/.     

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.     

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.     

Wavelength and power stabilisation of uncooled 975 nm thick quantum well lasers over 110/spl deg/C temperature range

The use of a thick quantum well enables coherence-collapse operation of a Bragg grating stabilised laser diode over 110/spl deg/C temperature range, yielding 975 nm wavelength emission with >40 dB sidemode suppression ratio, <1% power variation, and fibre-output power as high as 293 mW at 15/spl deg/C and 168 mW at 125/spl deg/C.     

1.42 /spl mu/m continuous-wave operation of GaInNAs laser diodes

Continuous-wave (CW) operation of GaInNAs laser diodes in the 1.4 /spl mu/m range has been realised for the first time. A GaInNAs double quantum well separate confinement heterostructure was grown by solid source molecular beam epitaxy. Threshold currents as low as 66 mA and external efficiencies as high as 0.29 W/A could be demonstrated in CW operation. Lasing was observed up to 150/spl deg/C and a characteristic temperature T/sub 0/ of 111K was demonstrated. The emission wavelength at room temperature was centred at 1417 nm.     

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.     

Short wavelength (/spl lambda//spl sim/4.3 /spl mu/m) high-performance continuous-wave quantum-cascade lasers

We report continuous-wave (CW) operation of a 4.3-/spl mu/m quantum-cascade laser from 80 K to 313 K. For a high-reflectivity-coated 11-/spl mu/m-wide and 4-mm-long laser, CW output powers of 1.34 W at 80 K and 26 mW at 313 K are achieved. At 298 K, the CW threshold current density of 1.5 kA/cm/sup 2/ is observed with a CW output power of 166 mW and maximum wall-plug efficiency of 1.47%. The CW emission wavelength varies from 4.15 /spl mu/m at 80 K to 4.34 /spl mu/m at 298 K, corresponding to a temperature-tuning rate of 0.87 nm/K. The beam full-width at half-maximum values for the parallel and the perpendicular far-field patterns are 26/spl deg/ and 49/spl deg/ in CW mode, respectively.     

Vertical-cavity surface-emitting lasers in the 8-/spl mu/m midinfrared spectral range with continuous-wave and pulsed emission

Continuous-wave (CW) as well as pulsed-laser emission from a midinfrared (/spl lambda/=7.92 /spl mu/m) IV-VI vertical-cavity surface-emitting laser at 1.8 K is presented. The high-finesse microcavity, containing PbSe as an active medium, was optically pumped with a carbon monoxide laser at a wavelength of 5.28 /spl mu/m (1894 cm/sup -1/) in either CW or Q-switched mode. The maximum achieved CW power was 4.8 mW and pulsed peak powers were up to 23 W. Linewidths are considerably narrower than 0.10 cm/sup -1/, corresponding to 0.6 nm.     

Photopumped lasing at 1.25 /spl mu/m of GaInNAs-GaAs multiple-quantum-well vertical-cavity surface-emitting lasers

We report room-temperature (RT) continuous-wave (CW) photopumped operation of long-wavelength vertical-cavity surface-emitting lasers (VCSELs) employing a Ga/sub 0.7/In/sub 0.3/N/sub 0.007/As/sub 0.993/-GaAs multiple-quantum-well (MQW) active layer grown directly on a GaAs-AlAs distributed Bragg reflector (DBR). Evidence for laser oscillation includes spectral linewidth narrowing, clamping of spontaneous emission, and a distinct increase in slope efficiency at threshold. By taking advantage of lateral growth rate nonuniformity, we obtained laser emission over an extremely broad 110-nm wavelength range, from 1.146-1.256 /spl mu/m. Equivalent threshold current density over this range was estimated at 3.3-10 kA/cm/sup 2/.     

Long wavelength GaInAsSb-AlGaAsSb distributed-feedback lasers emitting at 2.84 /spl mu/m

Room-temperature continuous-wave operation of a singlemode GaInAsSb/GaSb/AlGaAsSb distributed feedback (DFB) laser is presented at a record long emission wavelength for this material system of 2.843 /spl mu/m. The threshold current at 20/spl deg/C is 75 mA. Mode selection was realised by metal gratings laterally patterned to a ridge waveguide. By varying the grating period, DFB emission from 2.738 up to 2.843 /spl mu/m is obtained.     

Continuous-wave operation of GaInNAsSb distributed feedback lasers at 1.5 /spl mu/m

GaAs-based singlemode emission at 1.5 /spl mu/m has been realised for the first time in continuous-wave operation. GaInNAsSb active-layer material and GaAsN strain-compensating barriers have been used in combination with lateral distributed feedback. Laser diodes with a threshold current of 95 mA, an external efficiency of 0.15 W/A and a maximum output power of more than 10 mW could be demonstrated. A sidemode suppression ratio better than 31 dB could be realised at a singlemode emission wavelength of 1496 nm.     

Compact fully fibre integrated source of 100 fs pulses at 1.1 /spl mu/m based on compression in holey fibre

A simple, compact, fully fibre integrated source of /spl sim/100 fs pulses at a wavelength of 1.1 /spl mu/m is reported. 4 ps pulses at 1063 nm from a modelocked fibre laser were amplified to 23 mW in a ytterbium-doped fibre amplifier and subsequently propagated through 62 m of holey fibre with a zero dispersion wavelength at 1040 nm. Soliton formation, breakup and self frequency shift resulted in the formation of /spl sim/100 fs pulses at 1.1 /spl mu/m. Wavelength tunability from 1113 to 1220 nm is demonstrated.     

High-Temperature Continuous-Wave Operation of GaInAsN–GaAs Quantum-Dot Laser Diodes Beyond 1.3 μm

Internal laser parameters and characteristic temperature T₀ of a GaInAsN-GaAs quantum-dot (QD) laser emitting above 1350 nm were determined. Continuous-wave operation of GaInAsN-GaAs QD ridge waveguide laser diodes with an emission wavelength of 1355 nm at room temperature (RT) is reported for the first time. Low threshold currents of 16 mA are achieved at RT. Ground state laser emission is observed up to temperatures of 75degC with a resulting laser emission wavelength of 1395 nm.     

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.     

Fabrication of Germanosilicate glass optical fibers containing Tm/sup 2+/ ions and their nonlinear optical properties

Germanosilicate glass optical fibers incorporated with the Tm/sup 2+/ ions were fabricated to enhance optical nonlinearity by providing a strong reduction environment based on the solution doping technique in the modified chemical vapor deposition (MCVD) process. The incorporation of the Tm/sup 2+/ ions into the fiber core was identified by the electron paramagnetic resonance (EPR) spectrum in the fiber preform, and the absorption and emission properties between 350 and 1600 nm of the Tm/sup 2+/ ions in optical fibers and the fiber preform. A strong broad absorption band due to the Tm/sup 2+/ ions appeared from 350 to /spl sim/900 nm, and a broad emission from /spl sim/600 to /spl sim/1050 nm and the other emission from /spl sim/1050 to /spl sim/1300 nm, which were not shown in the Tm/sup 3+/ ions, were found upon Ar-ion laser pumping at 515 nm. Both absorption and emission results confirm that the Tm/sup 2+/ ions in the germanosilicate glass have the 4f-5d energy band from 350 to /spl sim/900 nm and the 4f-4f energy level at /spl sim/1115 nm. Also, the resonant nonlinearity at /spl sim/1310 and /spl sim/1530 nm due to the Tm/sup 2+/ ions in the fiber was measured upon the 515 nm optical pumping by using a long-period fiber grating (LPG) pair method. The nonlinear refractive index n/sub 2/ at /spl sim/1310 and /spl sim/1530 nm was found to be /spl sim/4/spl times/10/sup -15/ m/sup 2//W, where 70% and 30% of the n/sub 2/ are attributed to the nonradiative transitions and the radiative transitions, respectively.     

Room-temperature continuous-wave laser operation of electrically-pumped 1.55 /spl mu/m VECSEL

A report is presented on room-temperature (RT) continuous-wave (CW) laser emission at 1.55 /spl mu/m of an all InP-based electrically-pumped vertical external-cavity surface-emitting laser (EP-VECSEL). Threshold currents of 1.4 kA/cm/sup 2/ and output powers of up to 0.3 mW were measured under CW operation at RT. A maximum output power of 2.7 mW has been obtained in quasi-CW operation at a heatsink temperature of 10.5/spl deg/C. This first result demonstrates that EP-VECSELs are a potential candidate for the realisation of compact vertical-cavity emitting sources.     

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.     

A novel ultracompact two-mode-interference wavelength division multiplexer for 1.5-/spl mu/m operation

A novel ultracompact 2/spl times/2 wavelength division multiplexer (WDM) for 1.55-/spl mu/m operation based on highly dispersive two-mode interference (TMI) was designed, theoretically modeled, and verified using a finite-difference-time-domain (FDTD) method. A two-moded waveguide assisted with a dispersive tooth-shaped grating provided a mode-dependent reflection band of central wavelength at 1.55 /spl mu/m. The wavelengths of 1538 and 1572 nm that were at the band edges and had the lowest reflection losses and relatively high dispersion were selected for wavelength multiplexing. The result showed that the wavelengths were separated by grating dispersion in a coupler length of 75 /spl mu/m which was much shorter than the required length of 1.1 mm in a regular TMI multiplexer of no grating. Insertion loss of about 1.7 dB and channel contrast of about 12 dB were achieved.     

All-optical gain control of in-line erbium-doped fiber amplifiers for hybrid analog/digital WDM systems

Automatic gain control using an all-optical feedback loop in in-line erbium-doped fiber amplifiers (EDFA's) used in hybrid analog/digital wavelength division multiplexing (WDM) systems was studied. It is found that the signal level variation for the digital channels can be maintained within a range /spl les/3-dB between the presence and dropout of the analog channel when the narrowband feedback is centered at the amplified spontaneous emission (ASE) peak (/spl sim/1532 nm) with loop loss ranging between 13-22 dB. Robust transmission at 2.5 Gb/s without measurable power penalty was obtained for the digital channels when the EDFA was saturated by either the analog or the control lasing signal.     

Blue energy upconversion emission in thulium-doped-SiO/sub 2/-P/sub 2/O/sub 5/ channel waveguides excited at 1.064 /spl mu/m

Blue energy upconversion emission in Tm/sup 3+/-doped SiO/sub 2/-P/sub 2/O/sub 5/ channel waveguides off-resonance pumped by infrared radiation is reported. The waveguide samples were excited by a single continuous-wave laser source at 1.064 /spl mu/m. Two distinct blue emission signals around 450 and 480 nm, in addition to red at 660 nm and near-infrared at 800-nm less intense emissions were observed. The upconversion excitation mechanism was assigned to stepwise multiphoton absorption processes followed by nonradiative multiphonon-assisted relaxation processes. Infrared-to-blue conversion efficiencies with respect to the absorbed pump power of /spl sim/6.0/spl times/10/sup -7/ for this off-resonance pumping scheme was measured. The dependence of the infrared-to-blue upconversion mechanism upon the excitation power and thulium content is also examined.