Leo J. Missaggia

High‐power strained‐layer InGaAs/AlGaAs tapered traveling wave amplifier

High power, nearly diffraction‐limited cw performance has been obtained from a traveling wave amplifier, fabricated in a strained‐layer InGaAs/AlGaAs laser structure, with a laterally tapered gain region and with a cavity‐spoiling feature to prevent laser oscillation. The input beam diffracts as it propagates, efficiently filling the tapered active region. For input optical power of 85 mW from a Ti:sapphire laser, total cw output of 1.44 W has been achieved with 1.28 W in a central lobe with width less than 1.2 times the diffraction limit at 977 nm wavelength. Only 15 mW of power incident on the amplifier was sufficient to provide 1 W output into the central lobe.

High-power, strained-layer amplifiers and lasers with tapered gain regions

Laterally tapered gain regions designed to accommodate the diffraction of narrow single-lobe beams that have been used in both optical amplifiers and lasers are described. Amplifier output power of 3.5 W with 3.1 W in a 1.05 times diffraction-limited lobe and laser output power of over 4 W with approximately half the power in a 1.7 times diffraction-limited lobe have been achieved.<<ETX>>

Microchannel heat sinks for two-dimensional high-power-density diode laser arrays

The operation of a two-dimensional GaInAsP/InP diode laser array with CW power dissipation up to 500 W/cm/sup 2/ into a Si microchannel heat sink is discussed. The approximately 1*4-mm/sup 2/ laser array was used to characterize the heat sink, and the value of 0.040 degrees C cm/sup 2//W was obtained for the thermal resistance per unit area. The extrapolated value for a 1-cm/sup 2/ heated area is 0.070 degrees C cm/sup 2//W. >

Low‐threshold InGaAs strained‐layer quantum‐well lasers (λ=0.98 μm) with GaInP cladding layers and mass‐transported buried heterostructure

Buried‐heterostructure quantum‐well lasers fabricated by mass transport are reported for In0.18Ga0.82As/GaAs/Ga0.5In0.5P strained‐layer structures grown by atmospheric pressure organometallic vapor‐phase epitaxy. Threshold current densities as low as 85 A/cm2 are measured for broad‐stripe lasers, and buried‐stripe devices show threshold currents as low as 3 mA and differential quantum efficiencies as high as 34% per facet without coatings.

Near-diffraction-limited diode laser arrays by wavelength beam combining

We demonstrate 35 W output peak power with M2 approximately 1.35 in both dimensions from a 100 element, 100 microm pitch slab-coupled optical waveguide laser diode array using wavelength beam combining.

High-power 1.5-/spl mu/m InGaAsP-InP slab-coupled optical waveguide amplifier

We report the first demonstration of a high-power semiconductor optical amplifier (SOA) based on the slab-coupled optical waveguide concept. This concept allows the realization of SOAs having large fundamental optical modes, low loss, and small optical confinement factor. These attributes support large output saturation power, long length for efficient heat removal, and direct butt-coupling to single-mode fibers. The 1.5-/spl mu/m InGaAsP-InP quantum-well amplifier described here has a length of 1 cm, 1/e/sup 2/ intensity widths of 4 /spl mu/m (vertical) and 8 /spl mu/m (horizontal), a fiber-to-fiber gain of 13 dB, and a fiber-coupled output saturation power of 630 mW (+28 dBm). The measured butt-coupling efficiency between the amplifier and SMF-28 is 55%. Thus, the output saturation power of the amplifier itself is approximately 1.1 W (+31 dBm).

AlGaAs-InGaAs slab-coupled optical waveguide lasers

The slab-coupled optical waveguide laser (SCOWL) concept, recently proposed and demonstrated, is extended to the AlGaAs-InGaAs-GaAs material system. Both 980- and 915-nm SCOWL devices feature a nearly circular large-diameter single-spatial mode that can be butt coupled with high efficiency to a single-mode fiber. Single-ended continuous-wave output powers of greater than 1 W have been obtained at 980 nm.

Slab-coupled 1.3-μm semiconductor laser with single-spatial large-diameter mode

A high brightness semiconductor diode laser structure, which utilizes a slab-coupled optical waveguide region to achieve several potentially important advances in performance, is proposed and experimentally demonstrated using a simple rib waveguide in an InGaAsP-InP quantum-well structure operating at 1.3-/spl mu/m wavelength. These lasers operate in a large low-aspect-ratio lowest-order spatial mode, which can be butt coupled to a single-mode fiber with high coupling efficiency.

Active coherent beam combining of diode lasers

We have demonstrated active coherent beam combination (CBC) of up to 218 semiconductor amplifiers with 38.5 W cw output using up to eleven one-dimensional 21-element individually addressable diode amplifier arrays operating at 960 nm. The amplifier array elements are slab-coupled-optical-waveguide semiconductor amplifiers (SCOWAs) set up in a master-oscillator-power-amplifier configuration. Diffractive optical elements divide the master-oscillator beam to seed multiple arrays of SCOWAs. A SCOWA was phase actuated by adjusting the drive current to each element and controlled using a stochastic-parallel-gradient-descent (SPGD) algorithm for the active CBC. The SPGD is a hill-climbing algorithm that maximizes on-axis intensity in the far field, providing phase locking without needing a reference beam.

1.5-/spl mu/m InGaAsP-InP slab-coupled optical waveguide lasers

We report the demonstration of high-power semiconductor slab-coupled optical waveguide lasers (SCOWLs) operating at a wavelength of 1.5 /spl mu/m. The lasers operate with large (4/spl times/8 /spl mu/m diameter) fundamental mode and produce output power in excess of 800 mW. These structures have very low loss (/spl sim/0.5 cm/sup -1/) enabling centimeter-long devices for efficient heat removal. The large fundamental mode allows 55% butt-coupling efficiency to standard optical fiber (SMF-28). Comparisons are made between SCOWL structures having nominal 4- and 5-/spl mu/m-thick waveguides.