M.G. Peters

Enhanced performance of offset-gain high-barrier vertical-cavity surface-emitting lasers

The temperature dependence and power output of vertical-cavity surface-emitting lasers (VCSELs) are addressed. The peak wavelength of the quantum well has been offset from the wavelength of the device cavity mode so that they are aligned at elevated temperatures. The result of this design change is to produce an 8- mu m-diameter VCSEL capable of operation to 145 degrees C, as well as CW operation of broad-area (70- mu m diameter) heat-sunk devices to record power levels. Fiber coupling experiments were also carried out, and a record 33-mW CW power was coupled to a multimode fiber. >

17.3% peak wall plug efficiency vertical-cavity surface-emitting lasers using lower barrier mirrors

Modifications to the epitaxial growth of vertical-cavity surface-emitting laser (VCSEL) material have recently led to improved characteristics. By offsetting the quantum-well gain peak from the cavity mode, and implementing lower barrier p-type Al/sub 0.67/Ga/sub 0.33/As/GaAs DBR mirrors with parabolic interface gradings, better high-temperature operation and lower voltages have been achieved. These effects combine to yield a peak wall plug efficiency of 17.3% for room temperature, CW operation.<<ETX>>

Evaluating the effects of optical and carrier losses in etched‐post vertical cavity lasers

We demonstrate the combined effects of optical scattering loss and surface recombination (or carrier diffusion) on the performance and scalability of etched‐post vertical cavity lasers (VCLs). The size dependence of optical losses and threshold gain are determined from pulsed measurements of external quantum efficiency. Deeper etch depths result in a stronger radial dependence of the threshold gain, which quickly increases the threshold current density. With optical loss accounted for, pulsed threshold current density measurements give the extra information needed for evaluating carrier loss. Surface recombination or carrier diffusion also results in threshold current density increases, but scalability is ultimately limited by the ability of the active region to provide enough gain for smaller size, higher optical loss devices. Even with these losses, three‐quantum‐well VCLs with shallow etches have threshold currents as low as 420 μA.

High-power temperature-insensitive gain-offset InGaAs/GaAs vertical-cavity surface-emitting lasers

The authors have grown 997 nm vertical-cavity surface-emitting lasers with an offset between the wavelength of the cavity mode and the quantum well gain peak to improve high temperature operation, and with higher aluminum-content barriers around the active region to improve the carrier confinement. They fabricated lasers of 8-15 and 20- mu m diameters. The 8- mu m-diameter devices exhibited CW operation up to 140 degrees C with little change in threshold current from 15 degrees C to 100 degrees C, and the 20- mu m-diameter devices showed CW output power of 11 mW at 25 degrees C without significant heat sinking.<<ETX>>

Size-dependent output power saturation of vertical-cavity surface-emitting laser diodes

We demonstrate efficient vertical-cavity surface-emitting laser diodes with high output power levels. Improved output power in these pillar-etched devices is achieved through a 60% lower thermal resistance by using a 15-/spl mu/m-thick Au-plated heat spreading layer on the top surface with a size of 300/spl times/300 /spl mu/m/sup 2/. The maximum continous wave output power increases almost linearly with laser diameter, before it saturates at 42 mW for an unmounted Au-plated device of 64-/spl mu/m diameter. A simple analytical model describes the laser output characteristics and the size-dependent saturation behavior of the maximum output power.

Submilliampere-threshold InGaAs-GaAs quantum-well ridge-waveguide lasers with lateral confinement provided by impurity-induced disordering

Significant reduction of threshold currents in InGaAs-GaAs quantum-well ridge-waveguide lasers has been achieved by using silicon-induced disordering to provide lateral confinement. Room-temperature threshold currents as low as 0.7 mA for pulsed operation and 0.9 mA for cw operation have been obtained from an uncoated 137-/spl mu/m-long and 0.3-/spl mu/m-wide device. In addition, the effects of high-temperature annealing on the various device characteristics, such as the gain curve, internal loss, and quantum efficiency, have been investigated.<<ETX>>

A polarization independent GaAs-AlGaAs electrooptic modulator

Two designs for polarization independent GaAs-AlGaAs interferometric electrooptic modulators are described. One design uses the linear electrooptic effect to couple degenerate TE/TM eigenmodes of a single-mode waveguide. In the other design the eigenmodes need only be near degenerate. The design using the coupling between near degenerate TE/TM modes utilizes a novel biasing scheme. A novel polarization independent GaAs-AlGaAs interferometric optical modulator based on this design has been fabricated and characterized at 1.3 /spl mu/m. This modulator is fabricated as a traveling wave modulator incorporating 50 /spl Omega/, phase velocity matched, low microwave loss electrodes for maximum electrical bandwidth.

Low-temperature operation of vertical cavity surface-emitting lasers

Vertical cavity surface-emitting lasers originally designed for room temperature operation are operated at 77 K. At this temperature, the gain peak and the cavity mode do not overlap. However, due to joule heating, at high biasing levels they come back into alignment and high single-mode output powers and large modulation bandwidths are observed.<<ETX>>

Design of index-guided vertical-cavity lasers for low temperature-sensitivity, sub-milliamp thresholds, and single-mode operation

An improved current-to-light model, including bandgap renormalization, is applied to high-performance vertical-cavity lasers to determine appropriate values for Auger recombination and leakage currents in InGaAs quantum wells. The model is then used to analyze the threshold temperature sensitivity of various cavity designs, showing the design changes needed for broad temperature stability. The practical limits on low-threshold devices are then examined. Finally, a current-apertured design is analyzed in detail, showing stabilized single-mode operation with improved efficiency. >

Spontaneous emission factor in post microcavity lasers

The first measurements of the spontaneous emission coupling efficiency (/spl beta/) for electrically pumped microcavity lasers with transverse photon confinement are reported. The influence of scattering losses and carrier diffusion on microcavity lasers is investigated, A /spl beta/ of 0.01 is measured at 126 K in a 3-/spl mu/m diameter device with optimal gain-cavity detuning.