The authors report InGaAs single quantum well vertical-cavity surface-emitting lasers with an intracavity p-contact fabricated by selective oxidation of AlAs and distributed Bragg reflectors composed of binary materials (AlAs/GaAs). Record low threshold currents of 8.7 µA in ~3 µm square devices and 140 µA in 10 µm square devices with maximum output powers over 1.2 mW are achieved.

Ultralow threshold current vertical-cavity surface-emitting lasers obtained with selective oxidation

The phenomena occurring in semiconductor lasers due to weak external optical feedback are reviewed, including mode hopping and related mode-hopping noise, linewidth narrowing and broadening, and the transition to the coherence collapse regime. Guidelines are given for designing semiconductor lasers, both edge emitters and VCSEL's, with high endurance against external optical feedback. >

External optical feedback phenomena in semiconductor lasers

High-speed studies of packaged, submilliampere threshold, oxide-confined vertical cavity surface emitting lasers show modulation bandwidths > 16 GHz. Very high modulation current efficiency factors occur at low bias but decrease as the modulation bandwidth and frequency of the relative intensity noise peak saturate at higher currents.

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High-frequency modulation of oxide- confined vertical cavity surface emitting lasers

Vertical-Cavity Surface-Emitting Lasers

Increasing copper plated heatsink radii from 0 to 4 mum greater than the mesa in vertical-cavity surface-emitting lasers (VCSELs) reduced the measured thermal resistance for a range of device sizes to values 50% lower than previously reported over a range of device sizes. For a 9-mum diameter oxide aperture, the larger heatsink increases output power and bandwidth by 131% and 40%, respectively. The lasers exhibit a 3-dB modulation frequency bandwidth up to 9.8 GHz at 10.5 kA/cm2. The functional dependence of thermal resistance on oxide aperture diameter indicates the importance of lateral heat flow to mesa sidewalls

Low thermal resistance high-speed top-emitting 980-nm VCSELs

Planar, gain-guided vertical-cavity surface-emitting lasers (VCSELs) with a modulation bandwidth of 14 GHz are described. This bandwidth is reached at a drive current of only 8 mA. The intrinsic bandwidth of these devices is estimated to be greater than 50 GHz. Nonlinear light-current characteristics of these lasers may lead to a high level of nonlinear harmonic distortion of the high-frequency output. It is shown that the relative intensity of the second-harmonic response decreases rapidly at higher drive currents, in agreement with a phenomenological model based on the DC characteristics of the laser. >

High-speed vertical-cavity surface emitting laser

We report room‐temperature measurements of the spontaneous emission factor β in high‐quality gain‐guided GaAs/AlGaAs vertical cavity surface emitting lasers. In devices with 6‐μm diameter we obtain β=2.8×10−3. The measured scaling of β with the cavity volume agrees well with classical electromagnetic model of dipole radiation. The magnitude of β exceeds that predicted by classical theory by approximately a factor of 2.

Spontaneous emission factor and its scaling in vertical cavity surface emitting lasers

We describe the effect of back reflections on the relaxation‐oscillation peaks of low threshold (<6 mA), high intrinsic bandwidth (31 GHz) vertical cavity surface emitting lasers. With the largest feedback possible with our experimental arrangement, x=−5.8 dB, the relaxation‐oscillation peak breaks up into a series of sharp resonances with the spacing corresponding to the round tip frequency of the external cavity. In contrast to edge emitting lasers, no effect of reflections is observed for feedback levels x<−12.9 dB. This relative immunity of vertical cavity lasers to reflection noise is expected to be of interest for their applications to fiber communications.

Reflection noise in vertical cavity surface emitting lasers

We describe a simple technique to precisely measure the reflectivity spectra of the Bragg mirrors in individual vertical cavity surface emitting lasers. Detailed reflectivity spectra are obtained by measuring the response of the active layer junction to light impinging upon the output mirror, corrected by the active layer response spectrum. Precise measurements of the emission spectrum of the laser with respect to the Fabry–Perot notch are then possible. In the temperature range of 20–100 °C we measure the rates of 0.56 and 0.62A/°C for the mirror stack and the lasing wavelength, respectively.

Photocurrent spectroscopy of Bragg mirrors in vertical cavity surface emitting lasers

A combination of spontaneous emission lifetime and spectral measurements is used to estimate the threshold carrier density in small diameter gain guided vertical cavity surface emitting lasers. Differential spontaneous emission lifetimes measured below threshold are extrapolated to a τth=0.4 ns at threshold. The corresponding threshold carrier density is Nth=7.9×1018 cm−3. The measured carrier densities are used to calculate spontaneous emission spectra. These are in agreement with the edge emission spectra obtained on cleaved laser chips. For the measured carrier density, we estimate the threshold gain at the emission wavelength of g=1640 cm−1.

P. Brusenbach

Papers

High-speed vertical-cavity surface emitting laser

Spontaneous emission factor and its scaling in vertical cavity surface emitting lasers

Reflection noise in vertical cavity surface emitting lasers

Photocurrent spectroscopy of Bragg mirrors in vertical cavity surface emitting lasers

Threshold carrier density in vertical cavity surface emitting lasers