46 a Tuesdav Afternoon OFC '98 Technical Digest

Pump power = 18OmW Pump power wavelength 980m

18

16

14 9.

12 w 10 8 8 5 h

a 6 g 4

2 -40 -30 -20 -10 0 10 20

Pout (dBm)

TuH5 Fig. 3. Saturation behavior of the long amplifier.

A O 0 0 A

v + k o o o o o o o

-30 -20 -1 ci 0 10 20

Pout (dBm)

5

TuH5 Fig. 4. 8.6-cm-long waveguide.

Single- and double-pump 5.5-cm saturation behavior of the

It is clear from these results that net gain above 30 dB can be reached with 15-cm-long ion-exchanged phosphate-glass waveguide amplifiers, used in single-pass configuration. But this will require high pump power, which is not desirable. We have demonstrated here that similar gain will be obtained with shorter waveguides and much lower pump power if the mode confinement of these waveguides is high enough. This opens the way toward low-cost, high-gain, compact, Er-doped-glass ion-exchanged waveguide- amplifiers for 1.55-pm telecommunication applications.

The authors thank K. Ogawa for his support. *Lucent Technologzes, Mountain Avenue, Murray Hill, New Jersey 07974- 0636 1. J.M.P. Delavaux, S. Granlund, 0. Mizuhara, L.D. Tzeng, D. Barbier,

M. Rattay, F. Saint Andreand, A. Kevorkian, IEEE Photon. Technol. Lett. 9, (1997). D. Barbier, M. Rattay, N. Krebs, M. Trouillon, F. Saint Andri., G. Clauss, J.M.P. Delavaux, presented at ECI0'97, Stockholm, Swe- den, April 2-4, 1997. D. Barbier, M. Rattay, F. Saint Andre, G. Clauss, M. Trouillon, A. Kevorkian, J.M.P. Delavaux, E. Murphy, IEEE Photon. Technol. Lett. 9, (1997). D. Barbier, in Optical Amnplifitrs and their Applications, Vol. XVI of OSA Trends in Optics and Photonics Series (Optical Society of America, Washington, D.C., 1997).

2.

3.

4.

TuH6 3:30pm

10.6 W continuous wave power from InGaAs/AIGaAs (915 nm) laser diodes

X. He, S. Srinivasan, M. Ung, R. Patel, Opt0 Power Corporation, 3321 E. Global Loop, Tucson, Arizona 85706

High-power continuous wave (cw) InGaAdAlGaAs laser diodes have been the efficient pumping source for fiber lasers. We report 10.6 W cw power from a 100-pm-wide InGaAslAlGaAs quantum well laser diode. Power conversion efficiencies as high as 59% have been achieved for a 2-mm cavity-length diode. These devices also demonstrate a unique resistance to thermal damage.

The laser structures consist of an InGaAs quantum well active region between AlGaAs confinement layers. 100-pm-wide stripe diode lasers were prepared and bonded p-side down on a conduction-cooled heat sink.

Figure 1 shows the cw light-current (L-I) and efficiency-current (qw-I) characteristics of an InGaAslAlGaAs laser diode (cavity length 4 mm) measured at 4 "C heat sink temperature. 10.64 W cw power from front facet has been measured. The device exhibits no degradation at this power level, however, measurement was interrupted to avoid damage to the device. This power is 1.3 W higher than the best published data (9.3 W) for InGaAslAlGaAs laser diodes with nonabsorbing mirrors' and about 30% higher than the best data (8.1 W) for Al-free InGaAs laser diodes.' This laser diode not only shows high power capability, but also reveal high efficiency. It achieves more than 50% power conversion efficiency between 3-7 amp driving currents. The L-I characteristics shown in Fig. 1 also indicate that the maximum power of the diode is limited by cooling efficiency. If superior heat sinks such as, diamond heat sink as in Ref. 2, were used, higher power is conceivable.

The laser structure used for this work shows low loss and high efficiency. Figure 2 shows the L-I and qw-I characteristics of the laser diode with 2-mm cavity length measured at heat sink temperature of 5 "C. As high as 59% power conversion efficiency has been achieved for

--t 'Iw / - L-l

o . ) L / , , , . , . , . , , , , , , 0 2 4 6 8 1 0 1 2 1 4

CW current (A)

60

50

z 40

'0- C cn

30 (D 3 e.

20 2

10 2 0 Y h

0

,

TuH6 Fig. 1. Continuous wave light-current (L-I) and efficiency-current (qw-I) characteristics of an InGaAs/AlGaAs laser diode (cavity length 4 mm) measured at 4 "C heat sink temperature.

OFC '98 Technical Digest Tuesday Afternoon 0 47

0 1 2 3 4 5

CW current (A)

TuH6 Fig. 2. AlGaAs laser measured at heat sink temperature of 5 "C.

Continuous wave L-I and qw-I characteristics of an InGaAs/

the diode. The differential quantum efficiency measured from L-I curve in Fig. 2 is 87% at driving current of 3 amp.

The laser structure used for this work is robust to thermal rolling. Figure 3 shows the L-I characteristics of a device measured at various heat sink temperatures. The diodle was first tested at 15 "C up to 11 amp driving current (open circle in the figure). Thermal roll-over was ob- served. Then the same diode was measured at 5 "C up to 8.3 W without damaging the device. In order to verify that diode was not damaged by previous two measurements, diode was measured again at 15 "C (solid

8

6

ij

n g 4

2

0 I 4 6 8 1'0 12

+ l ' I ' I '

CW current (A) 2

line). The L-I curve matched fairly well at current lower than 6 amp. Above 6 amp, two curve does not match exactly due to the unstable temperature at high power because the thermal-electric cooler used was not capable to maintain the stable temperature. The diode was also tested at 25 "C and 35 "C up to 1 1 amp. Although L-I curve shows thermal-roll over at 25 "C and 35 "C, no damage to the diodl: was observed.

In conclusion, record cw power from 100-pm-wide laser diodes has been reported for an InGaAdAlGaAs quantum well laser. Diodes dem- onstrate high efficiency and robust to thermal damages. 1. B. Li, R.A. Parke, G.S. Jackson, R.R. Craig, i~n Optical Fiber Commu-

nication Conference, Vol. 6 of 1997 OSA Technical Digest Series (Optical Society ofAmerica, Washington, D.C., 1997), pp. 352-353. L.J. Mawst, A. Bhattacharya, M. Nesnidal, J. Lopez, D. Botez, D.Z. Garbuzov, L. DeMarco, J.C. Connolly, h4. Jansen, F. Fang, R.F. Nabiev, Appl. Phys. Lett., 69, 1532 (1996).

2.

TuH7 3 : 4 5 ~ m

Ultrahigh-power laser diode array pump source for fiber lasers

D. Boggavarapu, D. Caffey, X. He, S. Guipta, S. Srinivasan, R. Pleak, R. Patel, Opt0 Power Corporation, 3321 East Global Loop, Tucson, Arizona 85706

High-power laser diode arrays (HPLDAs) are finding increasing ap- plication in many fields due to low cost, small size, and high efficien- cy.l One factor limiting the use of HPLDAs is the highly asymmetric beam (asymmetric MZ factor), which is difficult to efficiently couple to optical fibers or focus to small spots. We remove this obstacle by using a novel optical beamshaping t e c h n i q ~ e ~ , ~ that allows us to achieve unprecedented high brightness fiber-coupled power levels with a single multimode HPLDA.

One-centimeter-wide HPLDAs were fabricated from MOCVD grown InGaAdAlGaAs epitaxial GRINSCH imaterial (48% emitter- packing density) and mounted on conductively cooled heat sinks. These arrays exhibit high slope efficiency (-1.1 WIA) and power conversion efficiency (>55%) with approximately 70 W multimode cw optical power at I = 80 Amps and T = 25 C. We have used this same array geometry to attain a record 155 W cw optical power.' Spectral measurements reveal a center wavelength of 915 nm with -3 nm FWHM at the 70 W power level. Reliability tests are ongoing with initial data showing >3000 hrs continuous operation at the 60 W power level with degradation rates comparable to industry standard

TuH6 Fig. 3. diode at various heat sink temperatures.

Continuous wave L-I characteristics of a InGaAdAlGaAs laser TuH7 Fig. 1. Schematic diagram of the beamshaper optical system (beamtrain from left to right-laser diode array to fiber).