J. J. Yang

HIGH PERFORMANCE SURFACE-EMITTING LASERS WITH 45 INTRACAVITY MICROMIRRORS

For the first time, high performance GaAs/GaAlAs surface‐emitting lasers with internal 45° micromirrors, which totally reflect and emit the beam from the substrate in junction‐down configuration, have been demonstrated. The 45° and 90° mirrors of the device were fabricated by using ion milling and reactive ion etching techniques, respectively. Typical threshold current density of 440 A/cm2, external differential efficiencies of 52%, and output power in excess of 1 W under quasi‐cw operation have been achieved.

Design considerations for diffraction coupled arrays with monolithically integrated self‐imaging cavities

Conditions for stabilization of in‐phase or out‐of‐phase array eigenmodes in diffraction coupled diode laser arrays are derived and applied to several array architectures. The analysis predicts that the discrimination between these two eigenmodes is strongest in arrays with half Talbot distance long free‐propagation region. In this geometry, the out‐of‐phase and in‐phase near fields are, respectively, reproduced and channeled halfway between the original channel locations.

High power cw operation of GaAs/GaAlAs surface‐emitting lasers mounted in the junction‐up configuration

High power cw operation of horizontal cavity monolithic GaAs/GaAlAs surface‐emitting lasers with all dry etched micromirrors in the junction‐up configuration has been demonstrated for the first time. The 45° and 90° mirrors of the devices were fabricated by ion beam etching and reactive ion etching techniques, respectively. Typical threshold current densities of less than 360 A/cm2, external differential efficiencies of 22% (0.34 W/A) from the emitting facet, and output powers in excess of 280 mW were achieved under cw operation.

Diffraction‐limited operation from monolithically integrated diode laser array and self‐imaging (Talbot) cavity

The monolithic integration of a linear array and a separately pumped self‐imaging Talbot cavity has resulted in diffraction‐limited single‐lobe output beams to output powers in excess of 100 mW/facet. A study was made of the device operation as a function of the drive currents applied to the array region and the Talbot cavity.

5 W GaAs/GaAlAs laser diodes with a reactive ion etched facet

GaAs/GaAlAs laser diodes with reactive ion etched facets have been demonstrated for the first time with high output powers (5 W from 100‐μm‐wide apertures), high output power density (15 MW/cm2), and high slope efficiencies (66%) in junction‐up configuration under quasi‐cw operation. Mirror etching was performed in a pure SiCl4 gas environment by maintaining a low background pressure and gas pressure. High quality etched facets have been achieved with almost no scattering loss.

Dependence of external differential efficiency on laser length and reflectivities in multiple quantum well lasers

The external efficiency ηd of quantum well (QW) lasers is maximum at some characteristic laser length, which is dependent upon mirror reflectivities and the number of QWs in the active layer. The observed decrease in ηd in short lasers is caused by increased optical absorption associated with a high concentration of free carriers in the QW and the surrounding waveguide layer. The carriers spill into the waveguide because of QW subband filling in short cavity lasers with high threshold gains.

Coherent operation of injection-locked monolithic surface-emitting diode laser arrays

A row of six surface‐emitting GaAlAs laser diode arrays was locked in a coupled resonator configuration by means of interconnecting waveguides. An external master oscillator was injected into the first array in order to achieve single longitudinal mode operation and wavelength tunability. Spectral data show all six devices were locked in a single longitudinal mode, with tunable operation of over 60 A. Far‐field fringe visibilities greater than 60% were achieved at 100 mW output powers.

High‐power cw operation of InGaAs/GaAs surface‐emitting lasers with 45° intracavity micro‐mirrors

High‐power cw operation of horizontal‐cavity, monolithic InGaAs/GaAs surface‐emitting lasers with all dry etched micro‐mirrors has been demonstrated for the first time. The 45° and 90° micro‐mirrors of the devices were fabricated by ion‐beam etching and reactive ion etching techniques, respectively. Threshold‐current densities of less than 500 A/cm2, external differential quantum efficiencies of 10% (0.12 W/A) from the emitting facet, and output powers in excess of 100 mW were achieved from uncoated devices driven under cw operation.

Monolithic two‐dimensional surface‐emitting diode laser arrays mounted in the junction‐down configuration

We report on the first achievement of large area (0.5 cm2) monolithic two‐dimensional surface‐emitting arrays mounted in the junction‐down configuration. Device fabrication involves dry etching of 45°, and vertical micromirrors with ±2° tolerances and <0.2 μm RMS smoothness, integration of 100‐μm‐thick current‐spreading electrodes for minimizing ohmic loss, large area packaging, and mounting to heat exchangers for long pulse and minimum chirp operation. Uniform lasing is achieved from 0.2×0.5 cm2 and 0.5×1 cm2 active area junction‐down monolithic arrays (120 and 600 emitters, respectively) using 100 μs long pulses at a 1% duty cycle. Differential quantum efficiencies of ≥ (R18)40% and 7% are achieved for rows of 12 emitters, and for 0.2×0.5 cm2 active area arrays, respectively. The decrease in efficiency with increased area is found to be due to current leakage, which in turn limits the 2‐D array emitted optical‐power density to 150 W/cm2. Wavelength chirp in these devices is measured to be <4 nm at twice...

Supermode discrimination in diffraction‐coupled laser arrays with separate contacts

We show that in‐phase lasing is favored in diffraction‐coupled arrays with separate electrical contacts for the common unguided diffraction zone and for the waveguide section, if the common unguided section is biased above a critical level. Below that level, out‐of‐phase lasing will be favored. By varying the current about the critical level, the far‐field intensity switches from a wide far‐field pattern characterized by the admixture of several supermodes, to a near‐diffraction‐limited single peak.