Room-temperature 2.81-/spl mu/m continuous-wave operation of GaInAsSb-AlGaAsSb laser

GaInAsSb-AlGaAsSb multiple quantum-well (QW) lasers with an emission wavelength of 2.81 /spl mu/m are reported. The ridge waveguide lasers with highly strained QWs show continuous-wave laser emission up to 25/spl deg/C; in pulsed mode, the lasers operate up to 60/spl deg/C. For pulsed operation, a threshold current density of 360 A/cm/sup 2/ is found for devices with 30-/spl mu/m stripe width and 2-mm cavity length at room temperature. A low threshold current density at infinite length of 248 A/cm/sup 2/ is derived.     

High-modal gain 1300-nm In(Ga)As-GaAs quantum-dot lasers

A semiconductor laser containing seven InAs-InGaAs stacked quantum-dot (QD) layers was grown by molecular beam epitaxy. Shallow mesa ridge-waveguide lasers with stripe width of 120 /spl mu/m were fabricated and tested. A high modal gain of 41 cm/sup -1/ was obtained at room temperature corresponding to a modal gain of /spl sim/6 cm/sup -1/ per QD layer, which is very promising to enable the realization of 1.3-/spl mu/m ultrashort cavity devices such as vertical-cavity surface-emitting lasers. Ground state laser action was achieved for a 360-/spl mu/m-cavity length with as-cleaved facets. The transparency current density per QD layer and internal quantum efficiency were 13 A/cm/sup 2/ and 67%, respectively.     

Fabrication of high-performance InGaAsN ridge waveguide lasers with pulsed anodic oxidation

We have demonstrated high-performance InGaAsN triple-quantum-well ridge waveguide (RWG) lasers fabricated using pulsed anodic oxidation. The lowest threshold current density of 675 A/cm/sup 2/ was obtained from a P-side-down bonded InGaAsN laser, with cavity length of 1600 /spl mu/m and contact ridge width of 10 /spl mu/m. The emission wavelength is 1295.1 nm. The transparency current density from a batch of unbonded InGaAsN RWG lasers was 397 A/cm/sup 2/ (equivalent to 132 A/cm/sup 2/ per well). High characteristic temperature of 138 K was also achieved from the bonded 10/spl times/1600-/spl mu/m/sup 2/ InGaAsN laser.     

1.3-/spl mu/m InAs quantum-dot laser with high dot density and high uniformity

We realized a triple-stacked 1.3-/spl mu/m InAs quantum dot (QD) with a high density of 2.4/spl times/10/sup 11/ cm/sup -2/ and a high uniformity of below 24 meV that employs an As/sub 2/ source and a gradient composition (GC) strain-reducing layer (SRL) grown on a GaAs substrate. We demonstrated the 1.3-/spl mu/m wavelength emission of this triple-stacked QD laser with a 0.92-mm cavity length and a cleaved facet at room temperature. In addition, we realized the highest maximum modal gain yet reported of 8.1 cm/sup -1/ per QD layer at beyond 1.28 /spl mu/m by using our high-density and high-uniformity QD.     

High performance quantum dot lasers on GaAs substrates operating in 1.5 /spl mu/m range

Stacked InAs/InGaAs quantum dots are used as an active media of metamorphic InGaAs-InGaAlAs lasers grown on GaAs substrates by molecular beam epitaxy. High quantum efficiency (/spl eta//sub i/>60%) and low internal losses (/spl alpha/<3-4 cm/sup -1/) are realised. The transparency current density per single QD layer is estimated as /spl sim/70 A/cm/sup 2/ and the characteristic temperature is 60 K (20-85/spl deg/C). The emission wavelength exceeds 1.51 /spl mu/m at temperatures above 60/spl deg/C.     

Distributed feedback gain-coupled lasers based on InGaAs quantum-wire arrays

Fabrication and characterization of a current-injected InGaAs-GaAs quantum-wire gain-coupled distributed feedback (DFB) laser operating at 77 K at a wavelength of 923 nm are presented. Threshold current densities in broad area lasers were measured to be as low as 160 A/cm/sup 2/. The side-mode suppression ratio at twice threshold is 35 dB. A 4-/spl mu/m rib waveguide device has a threshold of 14 mA. The patterning process for the second-order DFB grating fabricated with deep UV holography and wet-chemical etching is described.     

Minimal group refractive index dispersion and gain evolution in ultra-broad-band quantum cascade lasers

The group refractive index dispersion in ultra-broad-band quantum cascade (QC) lasers has been determined using Fabry-Perot spectra obtained by operating the lasers in continuous wave mode below threshold. In the wavelength range of 5-8 /spl mu/m, the global change of the group refractive index is as small as +8.2 /spl times/ 10/sup -3/ /spl mu/m/sup -1/. Using the method of Hakki and Paoli (1975), the subthreshold gain of the lasers has furthermore been measured as a function of wavelength and current. At the wavelength of best performance, 7.4 /spl mu/m, a modal gain coefficient of 16 cm/spl middot/kA/sup -1/ at threshold and a waveguide loss of 18 cm/sup -1/ have been estimated. The gain evolution confirms an earlier assumption that cross-absorption restricted laser action to above 6 /spl mu/m wavelength.     

Continuous-wave operation of GaInAs-AlGaAsSb quantum cascade lasers

We report on the demonstration of continuous-wave (CW) operation of GaInAs-AlGaAsSb quantum cascade (QC) lasers. By placing a 2.5-/spl mu/m-thick gold layer on both sides of the laser ridge to extract heat from the active region in the lateral direction, together with mounting the device epilayer down, we have achieved CW operation of GaInAs-AlGaAsSb QC lasers composed of 25 stages of active/injection regions. The maximum CW operating temperature of the lasers is 94 K, and the emission wavelength is around /spl lambda//spl sim/4.65 /spl mu/m. For a device with the size of 10/spl times/2000 /spl mu/m/sup 2/, the CW optical output power per facet is 13 mW at 42 K and 4 mW at 94 K. The CW threshold current density is 1.99 kA/cm/sup 2/ at 42 K, and 2.08 kA/cm/sup 2/ at 94 K, respectively.     

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.     

High-frequency modulation characteristics of 1.3-/spl mu/m InGaAs quantum dot lasers

In this letter, we report results of small-signal modulation characteristics of self-assembled 1.3-/spl mu/m InGaAs-GaAs quantum dot (QD) lasers at room temperature. The narrow ridge-waveguide lasers were fabricated with multistack InGaAs self-assembled QDs in active region. A high characteristic temperature of T/sub o/=210 K with threshold current density of 200A/cm/sup 2/ was obtained. Small-signal modulation bandwidth of f/sub -3 dB/=12 GHz was measured at 300 K with differential gain of dg/dn/spl cong/2.4/spl times/10/sup -14/ cm/sup 2/ from detailed characteristics. We observed that a limitation of modulation bandwidth in high current injection appeared with gain saturation. This property can direct future high-speed QD laser design.     

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/.     

Linewidth study of InAs-InGaAs quantum dot distributed feedback lasers

The linewidth of laterally loss-coupled distributed feedback (DFB) lasers based on InAs quantum dots (QDs) embedded in an InGaAs quantum well (QW) is investigated. Narrow linewidth operation of QD devices is demonstrated. A linewidth-power product less than 1.2 MHz /spl middot/ mW is achieved in a device of 300-/spl mu/m cavity length for an output power up to 2 mW. Depending on the gain offset of the DFB modes from the QD ground state gain peak, linewidth rebroadening or a floor is observed at a cavity photon density of about 1.2-2.4/spl times/10/sup 15/ cm/sup -3/, which is much lower than in QW lasers. This phenomenon is attributed to the enhanced gain compression observed in QDs.     

GaInAsN/GaAs quantum dot laser diodes operating in 1.36 /spl mu/m wavelength range

For the first time, a pseudomorphic GaInAsN DWELL laser with laser emission at 1.36 /spl mu/m and a low transparency current density (206 A/cm/sup 2/) grown by molecular beam epitaxy is reported. The GaInAsN DWELL laser shows a redshift in comparison to an N-free GaInAs DWELL laser of about 90 nm and a transparency current density of 35 A/cm/sup 2/ per single QD layer.     

Room temperature continuous-wave operation of buried ridge stripe lasers using InAs-InP (100) quantum dots as active core

Self-organized InAs quantum-dot (QD) lasers emitting at 1.5 /spl mu/m were grown by gas source molecular beam epitaxy on (100) InP substrates. Room temperature continuous-wave (CW) operation of QD-based buried ridge stripe lasers is reported. We investigated experimentally the relevant CW performances of as-cleaved InP-based QD lasers for telecom applications such as temperature properties (T/sub 0/=56 K), infinite length threshold current density (J/sub /spl infin///spl sim/150 A/cm/sup 2/ per QDs layer) and internal efficiency (0.37 W/A). Lasing in pulsed mode is observed for cavity length as short as 200 /spl mu/m with a threshold current of about 37 mA, demonstrating the high gain of the QD's active core. In addition, the Henry parameter of these InP-based QD lasers is experimentally determined using the Hakki-Paoli method (/spl alpha//sub H//spl sim/2.2).     

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.     

High-performance 1.06-/spl mu/m selectively oxidized vertical-cavity surface-emitting lasers with InGaAs-GaAsP strain-compensated quantum wells

We present the first room-temperature continuous-wave operation of high-performance 1.06-/spl mu/m selectively oxidized vertical-cavity surface-emitting lasers (VCSEL's). The lasers contain strain-compensated InGaAs-GaAsP quantum wells (QW's) in the active region grown by metalorganic vapor phase epitaxy. The threshold current is 190 /spl mu/A for a 2.5/spl times/2.5 /spl mu/m/sup 2/ device, and the threshold voltage is as low as 1.255 V for a 6/spl times/6 /spl mu/m/sup 2/ device. Lasing at a wavelength as long as 1.1 /spl mu/m was also achieved. We discuss the wavelength limit for lasers using the strain-compensated QW's on GaAs substrates.     

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.     

Mode switching and singlemode tuning in two-segment distributed feedback quantum cascade lasers

Two-segment distributed feedback (DFB) GaAs/AlGaAs bound-to-continuum quantum cascade lasers emitting at /spl sim/10.8 /spl mu/m were fabricated and investigated. Reversible switching between two different DFB modes by current injection control yielding sidemode suppression ratios up to >23 dB is reported. Two different devices were fabricated for which the distance between the different DFB modes is 1.5 and 2.5 cm/sup -1/, respectively, and quasi-continuous tuning over a range of >9 cm/sup -1/ (105 nm) between 120 and 250 K was observed.     

Long wavelength MOCVD grown InGaAsN-GaAsN quantum well lasers emitting at 1.378-1.41 /spl mu/m

Low threshold InGaAsN QW lasers with lasing wavelength at 1.378 and 1.41 /spl mu/m were demonstrated by metal organic chemical vapour deposition (MOCVD). The threshold current densities are 563 and 1930 A/cm/sup 2/ for the 1.378 and 1.41 /spl mu/m emitting lasers, respectively. The significant improvement of device performance is believed due to utilisation of high temperature annealing and introduction of GaAsN barriers to suppress the resulting wavelength blue shift. A comparable characteristic temperature coefficient of the external differential quantum efficiency, T/sub 1/, is observed for the InGaAsN-GaAsN QW laser compared to similar InGaAsN/GaAs structures.     

Type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region

Operation of type-II interband cascade lasers in the 4.3-4.7-/spl mu/m wavelength region has been demonstrated at temperatures up to 240 K in pulsed mode. These lasers fabricated with 150-/spl mu/m-wide mesa stripes operated in continuous-wave (CW) mode up to a maximum temperature of 110 K, with an output power exceeding 30 mW/f and a threshold current density of about 41 A/cm/sup 2/ at 90 K. The maximum CW operation temperature of 110 K is largely limited by the high specific thermal resistance of the 150-/spl mu/m-wide broad area lasers. A 20-/spl mu/m-wide mesa stripe laser was able to operate in CW mode at higher temperatures up to 125 K as a result of the reduced specific thermal resistance of a smaller device.