High continuous wave power, 0.8 μm-band, Al-free active-region diode lasers

Abstract

Efficient, high-power, Al-free active-region diode lasers emitting at ϭ0.83 m have been grown by low-pressure metalorganic chemical vapor deposition. Threshold-current densities as low as 220 A/cm 2 , maximum continuous wave ͑cw͒ power of 4.6 W, and a maximum cw wallplug efficiency of 45% are achieved from 1 mm long, uncoated devices with In 0.5 ͑Ga 0.5 Al 0.5 ͒ 0.5 P cladding layers. Further improvement is obtained by replacing the p-In 0.5 ͑Ga 0.5 Al 0.5 ͒ 0.5 P cladding layer with thin ͑0.1 m͒ electron-blocking layers of Al 0.85 Ga 0.15 As and In 0.5 ͑Ga 0.5 Al 0.5 ͒ 0.5 P, and a pIn 0.5 ͑Ga 0.9 Al 0.1 ͒ 0.5 P cladding layer. Such devices provide a record-high T 0 of 160 K and reach catastrophic optical mirror damage ͑COMD͒ at a record-high cw power of 4.7 W ͑both facets͒. The corresponding COMD power-density level ͑8.7 MW/cm 2 )is ϳ2 times the COMD power-density level for uncoated, 0.81-m-emitting AlGaAs-active devices. Therefore, 0.81-m-emitting, Al-free active-region devices are expected to operate reliably at roughly twice the power of AlGaAs-active region devices. © 1997 American Institute of Physics. ͓S0003-6951͑97͒04302-7͔High-power diode lasers emitting in the wavelength range ϭ0.8-0.87 m are of interest because of important applications such as pump sources for Nd:YAG lasers. Such lasers conventionally use AlGaAs in the active region for р0.84 m, and thus suffer from short lifetimes and limited output powers by comparison to GaAs-active-region devices. The quaternary alloys InGa͑As͒P, lattice matched to GaAs, offer an attractive alternative to the AlGaAs/GaAs material system because: ͑1͒ the potential for better reliability, due to their inherent resistance to the formation of dark-line defects 1 and lower surface recombination velocity of InGaAsP compared to AlGaAs; 2 ͑2͒ a smaller increase in facet temperature 1 with drive current, and ͑3͒ the potential for growing reliable diode lasers on Si substrates. 3 However, the InGaAsP/GaAs material system has small conduction-band offsets, which cause diode lasers made of such material to suffer from massive carrier leakage. As a result, one obtains a relatively high threshold-current density, J th ; 1,4,5 low internal efficiency, i ; 5,6 and low threshold-current characteristic temperature, T 0 . 5,7 A recent attempt to solve the problem of carrier leakage 8 has been the use of high-band-gap material ͑Al 0.7 Ga 0.3 As͒ for the cladding layers which delivered high T 0 , promising reliability data, but also relatively high J th . We have designed and fabricated high-power, efficient, Al-free active-region devices by employing two features: ͑high-band gap͒ cladding layers of In 0.5 ͑Ga 0.5 Al 0.5 ͒ 0.5 P and the ''broad-waveguide'' concept. 9,10 The former significantly reduces carrier leakage, while the latter insures both a low internal loss coefficient, ␣ i (ϳ2 cm Ϫ1 ), since a large fraction of the optical energy is contained within the not intentionally doped ͑i.e., low loss͒ waveguide, 10 as well as a large transverse spot size ͑0.5 m full-width at hal...

Low-temperature sensitive, compressively strained InGaAsP active (/spl lambda/=0.78-0.85 μm) region diode lasers

“…Although a low internal loss is observed ( = 1 cm the relatively low internal quantum efficiency ( = 0.72) is believed to reflect the interfacial quality of the InGaP/InGaAsP active region. Previously reported threshold current density ( ) and external differential efficiency ( ) for ( nm) InGaAsP lattice matched-active diode lasers with a BW structure are about 365 A/cm and 77%, respectively [10]. The threshold current density of our GaAs-active lasers is comparable with the previously published results [9].…”

“…Typical values for for as-cleaved GaAs single-quantum-well (SQW) lasers are about 100-120 K [9]. The values of obtained here are comparable with the previously reported values of GaAs-active [9] and InGaAsP-active ( K) diode lasers ( nm) [10]. In order to assess the Al-free 0.85-m-emitting active region for high-power applications, an optimized edge-emitting laser structure was fabricated by using the broad-waveguide (BW) design [8].…”

“…In order to assess the Al-free 0.85-m-emitting active region for high-power applications, an optimized edge-emitting laser structure was fabricated by using the broad-waveguide (BW) design [8]. The characteristic of BW lasers is that the fundamental transverse mode is designed to have very low loss ( 1 cm ), while the second-order transverse mode is suppressed by large radiation losses [10]. For the BW structure shown in Fig.…”

InGaAsP/GaInP/AlGaInP 0.8μm QW lasers grown by MOCVD using TBP and TBAs

“…This is because the larger band gap of AlGaInP compared with that of GaInP can more effectively block the carrier overflow from the active layer to the cladding layer [5]. Therefore, Al-free active-region InGaAsP/GaInP/AlGaInP lasers have the advantages of both high reliability and good temperature characteristics [5][6][7][8]. InGaAsP/AlGaInP 0.8 mm lasers are usually grown by metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy.…”

“…InGaAsP/AlGaInP 0.8 mm lasers are usually grown by metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy. In the case of MOCVD growth [5][6][7], all the lasers are grown using highly toxic gas sources PH 3 and AsH 3 . Although InGaAsP infrared lasers [9,10] and AlGaInP red lasers [11][12][13] have been successfully grown using the less toxic liquid metalorganic sources tertiarybutylarsine (TBAs) and tertiarybutylphosphine (TBP), so far, there have been no reports on the growth of 0.8 mm InGaAsP/AlGaInP lasers by MOCVD using TBP and TBAs.…”