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.     

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.     

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.     

Molecular beam epitaxy-grown separate confinement buried heterostructure PbEuSeTe-PbTe diode lasers

Separate confinement buried heterostructure (SCBH) tunable PbEuSeTe-PbTe diode lasers were fabricated by molecular beam epitaxy for the first time. Continuous wave (CW) operating temperature of 215 K was realized, which is the highest CW operating temperature ever reported for lead-chalcogenide diode lasers. Preliminary results show a significant improvement in threshold current and emission power. Exceptionally low threshold currents of 2.5 mA at 120 K, 76 mA at 180 K, and 252 mA at 200 K were measured. The temperature tuning range of the SCBH diode laser spans between 6.49 /spl mu/m at 20 K to 4.19 /spl mu/m at 215 K.     

Ridge-width dependence on high-temperature continuous-wave quantum-cascade laser operation

We report continuous-wave (CW) operation of quantum-cascade lasers (/spl lambda/=6 /spl mu/m) up to a temperature of 313 K (40/spl deg/C). The maximum CW optical output powers range from 212 mW at 288 K to 22 mW at 313 K and are achieved with threshold current densities of 2.21 and 3.11 kA/cm/sup 2/, respectively, for a high-reflectivity-coated 12-/spl mu/m-wide and 2-mm-long laser. At room temperature (298 K), the power output is 145 mW at 0.87 A, corresponding to a power conversion efficiency of 1.68%. The maximum CW operating temperature of double-channel ridge waveguide lasers mounted epilayer-up on copper heatsinks is analyzed in terms of the ridge width, which is varied between 12 and 40 /spl mu/m. A clear trend of improved performance is observed as the ridge narrows.     

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).     

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.     

Continuous-wave operation of quantum cascade laser emitting near 5.6 /spl mu/m

Buried heterostructure quantum cascade lasers emitting at 5.64 /spl mu/m are presented. Continuous-wave (CW) operation has been achieved at -30/spl deg/C for junction down mounted devices with both facets coated. A 750 /spl mu/m-long laser exhibited 3 mW of CW power with a threshold current density of 5.4 kA/cm/sup 2/.     

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.     

High-power ridge waveguide InGaAsN lasers fabricated with pulsed anodic oxidation

High-power InGaAsN triple-quantum-well strain-compensated lasers grown by metal-organic chemical vapor deposition were fabricated with pulsed anodic oxidation. A maximum light power output of 145 mW was obtained from a 4-/spl mu/m ridge waveguide uncoated laser diode in continuous-wave (CW) mode at room temperature. The devices operated in CW mode up to 130/spl deg/C with a characteristic temperature of 138 K in range of 20/spl deg/C-90/spl deg/C.     

Improved CW operation of GaAs-based QC lasers: T/sub max/= 150 K

We present a substantial improvement in the CW performance of GaAs-based quantum cascade lasers with operation up to 150 K. This has been achieved through suitable changes in device processing of a well-characterized laser. The technology optimizes the current injection in the laser by reducing the size of the active stripe whilst maintaining a strong coupling of the optical mode to preserve low current densities. The reduction of total dissipated power is critical for these lasers to operate CW. At 77 K, the maximum CW optical power is 80 mW, threshold current is 470 mA, slope efficiency is 141 mW/A, and lasing wavelength /spl lambda//spl sim/10.3 /spl mu/m.     

Resonant-phonon terahertz quantum-cascade laser operating at 2.1 THz (/spl lambda//spl sime/141 /spl mu/m)

The development of quantum-cascade lasers (QCLs) at 2.1 THz (/spl lambda//spl sime/141 /spl mu/m), which is the longest wavelength QCL to date without the assistance of magnetic fields, is reported. This laser uses a structure based on resonant-phonon depopulation, and a metal-metal waveguide to obtain high modal confinement with low waveguide losses. Lasing was observed up to a heatsink temperature of 72 K in pulsed mode and 40 K in continuous-wave (CW) mode, and 1.2 mW of power was obtained in CW mode at 17 K.     

CW technique for measurement of linewidth enhancement factor: application to 735-nm tensile-strained GaAsP quantum-well lasers

We present a procedure for determining the linewidth enhancement factor (/spl alpha/ parameter) in semiconductor lasers under continuous-wave (CW) operation. It is based on the measurement of the amplified spontaneous emission spectra, with a proper correction of thermal effects. The method is applied to 735-nm tensile strained GaAsP-AlGaAs quantum-well lasers and it is validated by comparing CW results, after correcting thermal effects, with pulsed measurements. The results show a low value of the /spl alpha/ parameter attributed to the tensile strain.     

2.0-/spl mu/m single-mode operation of InGaAs-InGaAsP distributed-feedback buried-heterostructure quantum-well lasers

Distributed-feedback (DFB) buried-heterostructure (BH) lasers with quantum-well active region emitting at 2.0 /spl mu/m have been fabricated and characterized. The lasers with four wells showed performance of practical use: threshold current as low as 15 mA for 600-/spl mu/m-long devices and CW single-mode output up to 5 mW at 2.03 /spl mu/m under operation current of 100 mA were observed. The current- and temperature-tuning rates of DFB mode wavelength are 0.004 nm/mA and 0.125 nm/K, respectively.     

High-power continuous-wave operation of quantum-cascade lasers up to 60/spl deg/C

High-temperature high-power continuous-wave (CW) operation of high-reflectivity-coated 12-/spl mu/m-wide quantum-cascade lasers emitting at /spl lambda/ = 6 /spl mu/m with a thick electroplated Au top contact layer is reported for different cavity lengths. For a 3-mm-long laser, the CW optical output powers of 381 mW at 293 K and 22 mW at maximum operating temperature of 333 K (60/spl deg/C) are achieved with threshold current densities of 1.93 and 3.09 kA/cm/sup 2/, respectively. At 298 K, the same cavity gives a maximum wall plug efficiency of 3.17% at 1.07 A. An even higher CW optical output power of 424 mW at 293 K is obtained for a 4-mm-long laser and the device also operates up to 332 K with an output power of 14 mW. Thermal resistance is also analyzed at threshold as a function of cavity length.     

Damping-limited modulation bandwidths up to 40 GHz in undoped short-cavity In/sub 0.35/Ga/sub 0.65/As-GaAs multiple-quantum-well lasers

We demonstrate record direct modulation bandwidths from MBE-grown In/sub 0.35/Ga/sub 0.65/As-GaAs multiple-quantum-well lasers with undoped active regions and with the upper and lower cladding layers grown at different growth temperatures. Short-cavity ridge waveguide lasers achieve CW direct modulation bandwidths up to 40 GHz for 6/spl times/130 /spl mu/m/sup 2/ devices at a bias current of 155 mA, which is the damping limit for this structure. We further demonstrate large-signal digital modulation up to 20 Gb/s (limited by the measurement setup) and linewidth enhancement factors of 1.4 at the lasing wavelength at threshold of /spl sim/1.1 /spl mu/m for these devices.     

Beam steering in high-power CW quantum-cascade lasers

We report the light-current (L-I), spectral, and far-field characteristics of quantum cascade lasers (QCLs) with seven different wavelengths in the /spl lambda/=4.3 to 6.3 /spl mu/m range. In continuous-wave (CW) mode, the narrow-stripe (/spl ap/13 /spl mu/m) epitaxial- side-up devices operated at temperatures up to 340 K, while at 295 K the CW output power was as high as 640 mW with a wallplug efficiency of 4.5%. All devices with /spl lambda//spl ges/4.7 /spl mu/m achieved room-temperature CW operation, and at T=200 K several produced powers exceeding 1 W with /spl ap/10% wallplug efficiency. The data indicated both spectral and spatial instabilities of the optical modes. For example, minor variations of the current often produced nonmonotonic hopping between spectra with envelopes as narrow as 5-10 nm or as broad as 200-250 nm. Bistable beam steering, by far-field angles of up to /spl plusmn/12/spl deg/ from the facet normal, also occurred, although even in extreme cases the beam quality never became worse than twice the diffraction limit. The observed steering is consistent with a theory for interference and beating between the two lowest order lateral modes. We also describe simulations of a wide-stripe photonic-crystal distributed-feedback QCL, which based on the current material quality is projected to emit multiple watts of CW power into a single-mode beam at T=200 K.     

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.     

Low-temperature optimized vertical-cavity lasers with submilliamp threshold currents over the 77-370 K temperature range

We demonstrate an extended temperature range (77-370 K) of continuous wave (CW) operation for dielectrically-apertured double-intracavity-contacted vertical-cavity InGaAs strained QW lasers optimized for operation at cryogenic temperatures. Superior performance is achieved through the alignment of the cavity mode with the gain of the first and second quantized subbands at 77 K and room temperature, respectively. This design results in submilliamp threshold currents over a 77-370 K temperature range for 5.4-/spl mu/m diameter lasers. The threshold is 120 /spl mu/A and the output power is >8 mW at 77 K.     

Room-temperature pulsed operation of 1.5-/spl mu/m vertical cavity lasers with an InP-based Bragg reflector

We report on a 1.5-/spl mu/m vertical-cavity laser that utilizes one GaInAsP-InP and one Si-SiO/sub 2/ mirror in combination with a strain-compensated GaInAsP quantum-well active layer. Pulsed lasing operation was achieved in a temperature range from -160 to +43/spl deg/C. The lasers exhibit 30-mA pulsed threshold current at room temperature. CW operation was obtained up to -25/spl deg/C.