Vertical-cavity surface-emitting laser diodes with post-growthwavelength adjustment

A novel vertical-cavity surface-emitting laser design enables the post-growth determination of the emission wavelength. The lasers employ a hybrid top mirror consisting of a semiconductor Bragg mirror and a metal reflector. The laser cavity length of each element in a 2-D array can be precisely adjusted after epitaxial growth by anodic oxidation and etching. An emission wavelength range of 25 nm is experimentally observed. Lasers operate under continuous wave conditions with threshold currents of about 6 mA and output powers up to 0.5 mW     

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.     

Tunable extremely low threshold vertical-cavity laser diodes

Submilliampere-threshold wavelength-tunable three-terminal vertical-cavity laser diodes have been fabricated by proton implantation and wet chemical etching. Laser diodes of 8-μm active diameter exhibit record low threshold currents of 650 μA and emit upto 170-μW output power under CW conditions and 0.4 mW under pulsed excitation. Slightly larger devices of about 12-μm diameter emit up to 1.85 mW in a single mode under pulsed conditions. The emission wavelength is about 970 nm and matched to the spectral gain of the three active InGaAs quantum wells. Individual elements in a two-dimensional array can be continuously tuned over 2.2 nm by applying separate tuning currents of 70 μA to the corresponding top mesa electrodes. Tuning and laser currents are controlled independently     

Thermal crosstalk in 4/spl times/4 vertical-cavity surface-emitting laser arrays

We measured thermal crosstalk in 4/spl times/4 VCSEL arrays with a 30-/spl mu/m pitch between devices. The effective thermal resistance of laser diodes in two-dimensional (2-D) arrays is about 50% higher than that of single elements. The output power of the lasers is fairly temperature insensitive under constant voltage operation. From experiments we inferred values for the average thermal conductivity of AlAs-GaAs Bragg reflectors. We found anisotropy in the effective thermal conductivity with numbers of 0.28 W/(cmK) and 0.35 W/(cmK) for the transverse and lateral direction, respectively.