Jane J. Yang

In‐phase locking in diffraction‐coupled phased‐array diode lasers

Design criteria are presented for strong in‐phase coupling of diffraction‐coupled phased‐array diode lasers. Theoretical predictions are confirmed by our experimental observations of double‐lobe and single‐lobe far‐field patterns.

Surface‐emitting GaAlAs/GaAs linear laser arrays with etched mirrors

Surface‐emitting GaAlAs/GaAs linear laser arrays are fabricated using the ion milling technique. Low threshold current and differential quantum efficiency comparable to these of the cleaved device are obtained.

High‐power 630–640 nm GaInP/GaAlInP laser diodes

High‐power visible laser diodes operating at 630–640 nm have been demonstrated. The devices have a GaInP/GaAlInP single quantum well, graded‐index separate confinement heterojunction. For 100 μm broad stripe uncoated lasers, threshold current densities of 1.06 KA/cm2 and pulsed output powers as high as 1.5 W/facet (total 3 W) at room temperature were achieved by optimizing the device cavity length. By coating rear facets with high‐reflectivity coatings, threshold current densities were reduced to 750 A/cm2, and output powers of 1.95 W were obtained. Unusual differential quantum efficiency versus cavity length characteristics were observed and are attributed to carriers spillover from the spacer/waveguide regions into the cladding layers.

High-power, high-duty-cycle operation of monolithic two-dimensional surface-emitting diode laser arrays in the junction-down configuration

High-power, high-duty cycle and continuous wave operation of large-area monolithic 2D surface-emitting GaAlAs laser diode arrays mounted junction-down on microchannel heat exchangers have been demonstrated. Devices mounted don 2-mm-thick Cu heat spreaders were operated to peak output power densities of > 100 W/cm2 at 35% duty cycles,a nd exhibited high power conversion efficiencies, and full width emission spectra of < 4nm. Arrays mounted on 1-mm-thick heat spreaders were operated under continuous wave operating condition to approximately equals 50 W/cm2 power density levels. Silicon microchannel heat exchangers with a measured thermal resistance per unit are of 0.0324 degree(s)C cm2/W were used to removed up to 550 W/cm2 of excess heat generated by the arrays.

Modulation characteristics of high-power phase-locked arrays of antiguides

The small signal modulation characteristics, large signal modulation characteristics and dc noise spectra on 70 micron-wide 20-element high-power phase-locked arrays of antiguides are reported. The relaxation resonance frequency at 1.5 times threshold is found to be 1.65 GHz. Large-signal pulse modulation produced no distortion to the far-field characteristics. The dc noise spectra showed a damped shot noise resonance at 1.32 GHz for a dc bias level of 1.18 times threshold.

Monolithic two-dimensional surface-emitting laser diode arrays with 45 degree micromirrors

Development and performance of large area (0.5 cm2) junction-down monolithic two- dimensional surface-emitting arrays is reported. This involves fabrication of 45 degree(s) and vertical micromirrors with +/- 2 degree(s) tolerances and < 0.2 RMS smoothness, lapping and polishing of 2 in. diameter wafers with < 10 micrometers thickness tolerances, integration of 100 micrometers thick current spreading electrodes which minimize ohmic losses, large area packaging, and mounting to heat exchangers for long pulse operation and minimum chirp. Single monolithic surface emitter diodes exhibit superior performance (slope efficiencies of (eta) d > 50%, threshold currents of Ith equals 220 mA, and output powers in excess of 720 mW). This projects to power densities > 860 W/cm2 and > 50% differential slope efficiencies for arrays of devices. Large area array operation (scaling) was demonstrated. Uniform lasing was achieved from 0.2 cm X 0.5 cm and 0.5 cm X 1.0 cm active area junction-down monolithic arrays (120 and 600 emitters respectively) using 100 microsecond(s) ec long pulses at a 1% duty cycle. Differential slope efficiencies of > 40% were achieved for rows of 12 emitters, and 8% for the large area arrays. The drop in efficiency was due to current leakage, which limited the output power densities to 150 W/cm2. Chirp in these devices was measured to be < 4 nm at twice the threshold current.

Semiconductor lasers with dry-etched facets

Semiconductor lasers with dry etched facets are of interest for monolithic 2-D coherent applications such as optical interconnects and optoelectronic integrated circuits. This paper reports recent development on this area including high-performance 3 X 3 individually addressable InGaAs/GaAs single-mode surface emitting laser diodes, 630 nm GaInP/GaAlInP surface-emitting laser diodes, and 1.3 micrometers InGaAsP/InP surface-emitting laser diodes grown on Si substrate.

Diode pumped Nd:YVO/sub 4/ microlaser 2D array

Summary form only given. A 2D microchannel cooled, monolithic surface emitting array operating at 808 nm, has been used to pump a 400 /spl mu/m thick wafer of Nd:YVO/sub 4/. The 12 by 8 diode array is collimated with fiber lenses to pump 80 /spl mu/m diameter spots. The array area has a cross-section of approximately 0.5 cm/sup 2/. Thermal lensing, produced by pump light absorption, provides cavity stability for each microlaser cell in the array. The Nd:YVO/sub 4/ wafer was AR coated on the pumped side at 808 nm and HR coated at 1.064 /spl mu/m.<<ETX>>

Efficient, high-power monolithic two-dimensional surface-emitting diode laser arrays mounted in the junction-down configuration

We review in-plane surface-emitting laser diode arrays and their applications. Efficient operation of monolithic, large area (0.54 cm2, 108 emitters) two-dimensional surface- emitting GaAlAs laser diode arrays mounted junction-down on microchannel heat exchangers has been demonstrated. Devices with 1.5 micrometers thick cladding layers were operated quasi- continuous-wave to high peak output power densities (> 100 W/cm2), exhibited high power conversion efficiencies (22%), and full width emission spectra of < 4 nm at 2% - 5% duty cycles. Arrays with a 2.5 micrometers thick cladding region were operated under continuous wave conditions to 46 W/cm2 power density levels. This corresponded to a 550 W/cm2 heat flux extracted by microchannel heat exchanges.

High-power short-wavelength surface-emitting laser diodes

We report on the first demonstration of high power, short-wavelength, in-plane, horizontal cavity ion-beam-etched surface-emitting lasers with emission wavelengths of 740 nm and 635 nm, and surface-emitting output powers of 850 mW and 170 mW from GaAlAs/GaAs and GaInP/GaAlInP laser diodes, respectively.