laser diodes with decoupled confinement heterostructure - cloudfront.net
Characteristics and reliability of high-power InGaAs/A1GaAs laser diodes with decoupled confinement heterostructure Yoshikazu Yamada, A.Okubo, Y..Oeda, Yumi Yamada, T.Fujimoto, K.Muro Electronics & Information Materials Laboratory,Mitsui-Chemicals,Inc.
Nagaura 580-32,Sodegaura,Chiba 299-0265,Japan Tel.+8 1 -43 8-62-3625 Fax.+8 1-438-62-3530
E-mai1:Yoshikazu.Yarnadamitsui-chem.co.jp ABSTRACT In order to overcome catastrophic optical damage(COD), decoupled confinement heterostructure(DCH) featuring abroadened
waveguide andthin carrierbiock layers havebeen developed. I)ue to decoupling ofcarner and optical confinement, aDCH laser can be designed more flexibly than a conventional separated confinement heterostructure (SCH) laser, i.e., laser diodes can be
designed with a variety of gain coupling flictor r , quantum-well number N, keeping the beam divergence angle constant. COD level ofvarious DCH laseis with uncoated icet was examined in 5Otsec pulse opemtion and ibliowing results weie obtained; COD was normalizedby equivalent vertical beam width d/ F (where d is thickness ofquantum-well) and COD level of 980nm InciaAs quantum-well lasers was twice as high asthat of86Onm GaAs quantum-well lasers, i.e., 100-1 1OmW/im for
InGaAs-QW and 4O-5OmW/im for GaAs-QW in the case of d/ F -1 . So, COD level can be manage in DCH scheme. Epitaxial stmctuie has been optimized thiough the high-power pethrmance of gain guided multi-mode laseis. The CW maximum power 6.3W was attained for 5Ojtm aperture and 9.5W for lOOjim aperture, which was limited by thermal saturation. Liletest was carned out for5Opim aperture devices at the condition of5O°C-1 OW. All 14 devices were operating over 13,000hrs
without failure. The median life was estimated to be more than one hundred thousand hours at 50°C. Real index guided structure was fabricated with a multi-step MOVPE epitaxial growth. Stable fabrication could be possible even in a conventional process, since chemically active Al-content was greatly reduced at 980nm in DCH. The maximum CW
output power was 1 .3W, which was limited by thermal saturation. Single mode operation was extended up to 700mW. And 500mW lank-free output was reproducibly obtained in a seff-aligned real index guide structure. Preliminarylife tests showed the
stable operation at 300mW-50°C and 300mW-70°C.
Keywords:High-power laser diodes, Catastrophic optical damage(COD), InGaAs/AlGaAs laser, Decoupled confinement heterostructure(DCH)
1.INTROI)UCTION High-power and high reliability laser diodes ai requiied in vaiious industiious fields such as DPSS, printing, medical treatment, material processing and telecommunication.
980nm laser diode is most inpoitant devices as a pump souice in eibium-doped fiber ampliiieis(EDFAs)' of optical transmission system applications, since it has low-noise figure than l4SOnm pumping. However so Jar it is generally believed that the reliability ofhigh-power of980nm laser diodes is not good as 1480nm laser
Part of the SP)E Conference on TestinQ, Packaging, and Reliability of Semiconductor Lasers IV • San Jose, California • January 1999 SPIE Vol. 3626 • 0277-786X/99/$1O.OO
231
because of the occunence of catastiophic optical mirmr damage (COMD)'9. Namely nonnidiative recombination and reabsorption oflaser light via sur!äce states on the normal facets induces facet heat-up, subsequent facet degradation and finally sudden failure in high-power operation2'3.
To overcome this problem, a variety of laser structures, that is, window structure, flicet passivation etc. has been developed. And we have proposed decoupled confinement heterostructure (DCH) in GaAS/AIGaAS quantum-well laser diodes4.
lii this paper, 980nm broad areaand single mode InGaAs/A1GaAs lasers th DCH ait reported. The authors think that those
lasers have two e&cts. First, gain coupling tor F is le to be ieduced. So equivalent veitical beam width d/ r is enlaiged. As a result, COD level is incieased and reliability in high-power opemtion is enhanced. And simultaneously the
decrease of F suppitssed hole burning eIct. So in the case ofsingle mode lasers, lateral mode is expected to be moie stabilized for less F and higher power single mode operation is anticipated. Second, reduction ofAl content is possible in comparison with SCH. So DCH gets the advantage to low electric andlow thermal resistance. This has an effect of supressing temperature rising oflaser chip and improving energy efficiency. And it is favemble to broad arealasers which is operated on large
current.
2.LASER STRUCTURES FLEXIBLY DESiGNED BY DCH In Fig. 1 , a schematic DCH epitaxial profile is shown. DCH laser diode is characterizedby broadened waveguide layers and
thin carrier-block layers sandwiching active area It is one of the atures of DCFI that veiy flexible design ofoptical intense distribution inthe waveguide mode is possible. Due to decoupling between carrier and optical confinement, it expands freedom
x1
of designing laser diodes.
>Eg
//vp p-clad
i
: Substrate
layer
carrier block layer
waveguide
N
n-clad
t
Ni
Nagaura 580-32,Sodegaura,Chiba 299-0265,Japan Tel.+8 1 -43 8-62-3625 Fax.+8 1-438-62-3530
E-mai1:Yoshikazu.Yarnadamitsui-chem.co.jp ABSTRACT In order to overcome catastrophic optical damage(COD), decoupled confinement heterostructure(DCH) featuring abroadened
waveguide andthin carrierbiock layers havebeen developed. I)ue to decoupling ofcarner and optical confinement, aDCH laser can be designed more flexibly than a conventional separated confinement heterostructure (SCH) laser, i.e., laser diodes can be
designed with a variety of gain coupling flictor r , quantum-well number N, keeping the beam divergence angle constant. COD level ofvarious DCH laseis with uncoated icet was examined in 5Otsec pulse opemtion and ibliowing results weie obtained; COD was normalizedby equivalent vertical beam width d/ F (where d is thickness ofquantum-well) and COD level of 980nm InciaAs quantum-well lasers was twice as high asthat of86Onm GaAs quantum-well lasers, i.e., 100-1 1OmW/im for
InGaAs-QW and 4O-5OmW/im for GaAs-QW in the case of d/ F -1 . So, COD level can be manage in DCH scheme. Epitaxial stmctuie has been optimized thiough the high-power pethrmance of gain guided multi-mode laseis. The CW maximum power 6.3W was attained for 5Ojtm aperture and 9.5W for lOOjim aperture, which was limited by thermal saturation. Liletest was carned out for5Opim aperture devices at the condition of5O°C-1 OW. All 14 devices were operating over 13,000hrs
without failure. The median life was estimated to be more than one hundred thousand hours at 50°C. Real index guided structure was fabricated with a multi-step MOVPE epitaxial growth. Stable fabrication could be possible even in a conventional process, since chemically active Al-content was greatly reduced at 980nm in DCH. The maximum CW
output power was 1 .3W, which was limited by thermal saturation. Single mode operation was extended up to 700mW. And 500mW lank-free output was reproducibly obtained in a seff-aligned real index guide structure. Preliminarylife tests showed the
stable operation at 300mW-50°C and 300mW-70°C.
Keywords:High-power laser diodes, Catastrophic optical damage(COD), InGaAs/AlGaAs laser, Decoupled confinement heterostructure(DCH)
1.INTROI)UCTION High-power and high reliability laser diodes ai requiied in vaiious industiious fields such as DPSS, printing, medical treatment, material processing and telecommunication.
980nm laser diode is most inpoitant devices as a pump souice in eibium-doped fiber ampliiieis(EDFAs)' of optical transmission system applications, since it has low-noise figure than l4SOnm pumping. However so Jar it is generally believed that the reliability ofhigh-power of980nm laser diodes is not good as 1480nm laser
Part of the SP)E Conference on TestinQ, Packaging, and Reliability of Semiconductor Lasers IV • San Jose, California • January 1999 SPIE Vol. 3626 • 0277-786X/99/$1O.OO
231
because of the occunence of catastiophic optical mirmr damage (COMD)'9. Namely nonnidiative recombination and reabsorption oflaser light via sur!äce states on the normal facets induces facet heat-up, subsequent facet degradation and finally sudden failure in high-power operation2'3.
To overcome this problem, a variety of laser structures, that is, window structure, flicet passivation etc. has been developed. And we have proposed decoupled confinement heterostructure (DCH) in GaAS/AIGaAS quantum-well laser diodes4.
lii this paper, 980nm broad areaand single mode InGaAs/A1GaAs lasers th DCH ait reported. The authors think that those
lasers have two e&cts. First, gain coupling tor F is le to be ieduced. So equivalent veitical beam width d/ r is enlaiged. As a result, COD level is incieased and reliability in high-power opemtion is enhanced. And simultaneously the
decrease of F suppitssed hole burning eIct. So in the case ofsingle mode lasers, lateral mode is expected to be moie stabilized for less F and higher power single mode operation is anticipated. Second, reduction ofAl content is possible in comparison with SCH. So DCH gets the advantage to low electric andlow thermal resistance. This has an effect of supressing temperature rising oflaser chip and improving energy efficiency. And it is favemble to broad arealasers which is operated on large
current.
2.LASER STRUCTURES FLEXIBLY DESiGNED BY DCH In Fig. 1 , a schematic DCH epitaxial profile is shown. DCH laser diode is characterizedby broadened waveguide layers and
thin carrier-block layers sandwiching active area It is one of the atures of DCFI that veiy flexible design ofoptical intense distribution inthe waveguide mode is possible. Due to decoupling between carrier and optical confinement, it expands freedom
x1
of designing laser diodes.
>Eg
//vp p-clad
i
: Substrate
layer
carrier block layer
waveguide
N
n-clad
t
Ni
