M.G. Harvey

4 W quasi-continuous-wave output power from 2 μm AlGaAsSb/InGaAsSb single-quantum-well broadened waveguide laser diodes

AlGaAsSb/InGaAsSb single-quantum-well (SQW) laser diodes emitting at 2 μm were fabricated and tested. At 10–15 °C, the uncoated SQW lasers with 2–3 mm cavity lengths exhibit a threshold current density of 115 A/cm2, a continuous-wave output power of 1.9 W, a differential efficiency of 53%, and a quasi-continuous-wave output power of 4 W. Their performance deteriorates rapidly as output losses increase beyond 10 cm−1.

High-power separate-confinement heterostructure AlGaAs/GaAs laser diodes with broadened waveguide

AlGaAs/GaAs graded-index separate-confinement heterostructure single quantum well (GRINSCH-SQW) lasers with different waveguide thickness have been analyzed experimentally and compared with results from modeling using transverse optical field distributions. We have found that for GRINSCH lasers the halfwidth of near-field and far-field patterns depends very weakly on the waveguide thickness due to the focusing of the optical field in the transverse direction by the graded-index waveguide. At the same time, the mode intensity in the cladding layers is reduced by two orders of magnitude as the waveguide thickness is increased from 40 nm to 1200 nm. As a result, a 20% improvement in the differential quantum efficiency ((eta) d) is realized, while the threshold current density remains unchanged. Differential quantum efficiency as high as 78% and output power exceeding 4 W cw have been obtained for broadened waveguide lasers.

Operating characteristics of InGaAs/AlGaAs strained single quantum well lasers

The performance of a series of InxGa1−xAs/AlGaAs (x=0.20 and 0.25) strained single quantum well (SSQW) lasers with lasing wavelengths in the range 930≤λ≤1000 nm is discussed. Less‐strained devices, with x=0.20 and QW thickness 7 nm (λ∼930 nm), perform comparably with GaAs QW lasers. Longer wavelength (λ>950 nm), more highly strained lasers exhibit poorer performance. Our results suggest that interfacial recombination limits the performance at the longer wavelength structures.

980 nm diode laser for pumping Er/sup 3+/-doped fiber amplifiers

A high-power 980-nm diode laser, whose performance satisfies the requirements for pumping Er/sup 3+/-doped optical fiber amplifiers, is described. The device is grown by atmospheric pressure organometallic vapor-phase epitaxy and contains a strained, step-graded In/sub 0.25/Ga/sub 0.75/As/AlGaAs single-quantum-well active region. The threshold current of the ridge-waveguide laser is 8 mA, and a CW power output of 125 mW with a different quantum efficiency of 59% is demonstrated.<<ETX>>

Magnetic resonance imaging of hyperpolarized 129Xe produced by spin exchange with diode-laser pumped Cs

We report the results of experiments leading to the production of an image of a polarized 129Xe sample prepared by spin exchange with Cs, optically pumped with a spectrally narrowed 894.3 nm diode laser. Representative images of the average electron spin polarization are shown. Appreciable cesium electron polarization values were achieved, and a nuclear polarization of about 2.5% was measured for 129Xe. The absolute nuclear polarization was measured by water-calibrated free induction decay of the nuclear magnetic resonance signal, and the polarized xenon imaged using a 2 T magnetic resonance imaging system.

Low-threshold, high-power, 1.3-/spl mu/m wavelength, InGaAsP-InP etched-facet folded-cavity surface-emitting lasers

A 1.3-/spl mu/m wavelength, InGaAsP-InP folded-cavity, surface-emitting laser with CH/sub 4/-H/sub 2/ reactive ion-etched vertical and 45/spl deg/ angled facets was demonstrated for the first time. Continuous-wave threshold currents of 32 mA have been achieved, with >15 mW CW power for the surface-emitted light. These surface-emitting lasers with two dry-etched facets are suitable for wafer-level testing and for monolithic integration with other InP-based photonic devices.<<ETX>>

Linear, high-speed, high-power strained quantum-well LEDs

InGaAs/AlGaAs edge-emitting LEDs are shown to be efficient (4% quantum efficiency), linear over four decades of current, and capable of operating in a analog or digital mode at modulation bandwidths exceeding 500 MHz. The spectral width of these LEDs is on the order of 700 AA at the 3-dB intensity points. The device is suited for high-speed backplane and short-distance local area network applications, where fiber dispersion is inconsequential. It appears to be a competitive optical power source for a variety of advanced applications, with speed and power outputs approaching those of laser diodes, but without the complication of a threshold current and associated active stabilization circuitry.<<ETX>>

High‐power GaAs/AlGaAs diode lasers grown on a Si substrate by metalorganic chemical vapor deposition

High‐power GaAs/AlGaAs double‐heterostructure lasers have been fabricated on Si substrates using a single‐step metalorganic chemical vapor deposition process. An output power of 130 mW (per facet) and a slope efficiency of 38% have been obtained under pulsed operation. The peak emission wavelength of the laser was 8823 A and the beam full width at half power for the parallel and perpendicular far‐field radiation patterns were 6° and 41°, respectively.

Super-high-power operation of 0.98-μm InGaAs(P)/InGaP/GaAs-broadened waveguide separate confinement heterostructure quantum well diode lasers

Record high powers of 16.8 W and 23.5 W have been obtained at CW and Quasi-CW (QCW) operation of 200 μm-aperture Al-free broad waveguide 0.98 μm SCH QW InGaAs(P)/InGaP/GaAs lasers. Some new features of diode laser operation at the super high power regime are considered. Non-thermal, purely current-induced mechanism of power saturation decreases the output powers at P>14 W. Influence of thermal-induced power saturation at high CW currents can be reduced by the stabilization of active region temperature. The main portion (-70%) of active region overheating is associated with a temperature gradient in the copper heatsink. The computed temperature distribution across device is in a good agreement with the spectral and direct measurements of the diode laser temperature. Life-testing at an output power level of 6 W CW and 45 °C has shown only about 6% degradation after more than 1200 hours of operation.

Non-thermal saturation of P-I characteristics for InP- and GaSb-based broad-contact SCH-QW lasers

Summary form only given. High-power pulsed eye-safe IR laser diodes are currently of increasing interest for applications including range finders and IRCM systems. The output power for InP-based lasers is limited by power-current (P-I) characteristics saturation (rollover effect) rather than by the catastrophic optical damage of the mirror facets as observed for shorter wavelength devices. The current leakage from the quantum well active region has been considered as one of the main reasons of the rollover effect. We present data on the studies of P-I characteristics in the short pulsed regime for broad-contact InP-and GaSb-based separate-confinement heterostructure double-quantum-well (SCH-DQW) lasers emitting in the wavelength range 1.45-1.95 /spl mu/m.