John C. Connolly

8 W continuous wave front‐facet power from broad‐waveguide Al‐free 980 nm diode lasers

Al‐free 980 nm InGaAs/InGaAsP/InGaP laser structures grown by low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD) have been optimized for high cw output power by incorporating a broad waveguide design. Increasing the optical‐confinement layer total thickness from 0.2 to 1.0 μm decreases the internal loss fivefold to 1.0–1.5 cm−1, and doubles the transverse spot size to 0.6 μm (full width half‐maximum). Consequently, 4‐mm long, 100‐μm‐aperture devices emit up to 8.1 W front‐facet cw power. cw power conversion efficiencies as high as 59% are obtained from 0.5‐mm long devices. Catastrophic‐optical‐mirror‐damage (COMD) power‐density levels reach 15.0–15.5 MW/cm2, and are found similar to those for InGaAs/AlGaAs facet‐coated diode lasers.

High-power (>10 W) continuous-wave operation from 100-μm-aperture 0.97-μm-emitting Al-free diode lasers

By incorporating a broad transverse waveguide (1.3 μm) in 0.97-μm-emitting InGaAs(P)/InGaP/GaAs separate-confinement-heterostructure quantum-well diode-laser structures we obtain record-high continuous-wave (cw) output powers for any type of InGaAs-active diode lasers: 10.6–11.0 W from 100-μm-wide-aperture devices at 10 °C heatsink temperature, mounted on either diamond or Cu heatsinks. Built-in discrimination against the second-order transverse mode allows pure fundamental-transverse-mode operation (θ⊥=36°) to at least 20-W-peak pulsed power, at 68×threshold. The internal optical power density at catastrophic optical mirror damage (COMD) PCOMD is found to be 18–18.5 MW/cm2 for these conventionally facet-passivated diodes. The lasers are 2-mm-long with 5%/95% reflectivity for front/back facet coating. A low internal loss coefficient (αi=1 cm−1) allows for high external differential quantum efficiency ηd (85%). The characteristic temperatures for the threshold current T0 and the differential quantum effic...

Multiwavelength 10-GHz picosecond pulse generation from a single-stripe semiconductor diode laser

A single-stripe GaAs-AlGaAs semiconductor optical amplifier (SOA) has been used to generate four tunable wavelength-division multiplexed (WDM) channels simultaneously, each transmitting 12-ps pulses at 2.5 GHz, for an aggregate pulse rate of 10 GHz. Wavelength tuning over 18 nm has been demonstrated with channel spacing ranging from 0.8 to 2.1 nm. A potential spectral correlation across the multiwavelength spectrum has been studied in both experiment and simulation methods. These results show the potential for utilizing single stripe laser diodes as multiwavelength sources in WDM-TDM network.

2.3-2.7-μm room temperature CW operation of InGaAsSb-AlGaAsSb broad waveguide SCH-QW diode lasers

A new approach in the design of (Al)InGaAsSb-GaSb quantum-well separate confinement heterostructure (QW-SCH) diode lasers has led to continuous-wave (CW) room-temperature lasing up to 2.7 /spl mu/m. This has been achieved by using quasiternary heavily strained InGaSb(As) QWs inside a broad-waveguide SCH laser structure. The QW compositions are chosen in the region outside the miscibility gap and, as a consequence, do not suffer from clustering and composition inhomogeneity normally found with quaternary InGaAsSb compounds of 2.3-2.7-/spl mu/m spectral range. Very low threshold current density (/spl sim/300 A/cm/sup 2/) and high CW output powers (>100 mW) were obtained from devices operating in the 2.3-2.6-/spl mu/m wavelength range.

Continuous-wave operation of λ=3.25 μm broadened-waveguide W quantum-well diode lasers up to T=195 K

Mid-infrared (λ=3.25 μm) broadened-waveguide diode lasers with active regions consisting of 5 type-II “W” quantum wells operated in continuous-wave (cw) mode up to 195 K. At 78 K, the threshold current density was 63 A/cm2, and up to 140 mW of cw output power was generated. A second structure with ten quantum wells operated up to 310 K in pulsed mode.

Ultralow‐loss broadened‐waveguide high‐power 2 μm AlGaAsSb/InGaAsSb/GaSb separate‐confinement quantum‐well lasers

Broadening the waveguides of 2 μm AlGaAsSb/InGaAsSb separate‐confinement multiquantum‐well lasers decreases their internal losses to 2 cm−1, while threshold current densities remain as low as 300 A/cm2. The consequently high cw differential efficiency of 0.36 results in output powers of 1.2 W from 100 μm aperture lasers at 15 °C.

Demonstration of phase correlation in multiwavelength mode-locked semiconductor diode lasers

Wideband spectral phase correlation is demonstrated from a multiwavelength mode-locked semiconductor laser. By use of frequency-resolved optical gating techniques, significant phase correlation was observed between multiple intracavity oscillating wavelengths, with wavelength separations of ~1 nm . The resultant temporal characteristics show a substantial modulation owing to the spectral coupling induced by intracavity-generated four-wave mixing. This result may lead to novel methods for directly generating ultrafast subpicosecond optical pulse sequences with spectrally tailored amplitude and phase characteristics from actively mode-locked semiconductor lasers.

Morphology-dependent resonances of a microsphere–optical fiber system

Morphology-dependent resonances of microspheres sitting upon an index-matched single-mode fiber half-coupler are excited by a tunable 753-nm distributed-feedback laser. Resonance peaks in the scattering spectra and associated dips in the transmission spectra for the TE and TM modes are observed. We present a new model that describes this interaction in terms of the fiber-sphere coupling coefficient and the microspheres intrinsic quality factor Q(0). This model enables us to obtain expressions for the finesse and the Q factor of the composite particle-fiber system, the resonance width, and the depth of the dips measured in the transmission spectra. Our model shows that index matching improves the coupling efficiency by more than a factor of 2 compared with that of a non-index-matched system.

Above-room-temperature optically pumped midinfrared W lasers

We report temperature-dependent pulsed lasing performance, internal losses, and Auger coefficients for optically pumped type-II W lasers with wavelengths in the range of 3.08–4.03 μm at room temperature. All lased to at least 360 K, and produced 1.5–5 W peak power at 300 K. Internal losses at 100 K were as low as 10 cm−1, but increased to 90–360 cm−1 at 300 K. Room temperature Auger coefficients varied from 5×10−28 cm6/s at the shortest wavelength to 3×10−27 cm6/s at the longest.

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.