Chan A. Tu

Optical electroabsorption modulators for wideband, linear, low-insertion-loss photonic links

We describe the characterization and development of semiconductor quantum well electroabsorption modulators (EAMs) for insertion into high-performance photonic links intended for analog applications. Limitations of existing approaches are described, motivating the potential of EAMs for exploiting the flexibility of semiconductor bandgap engineering. Relationships are established between basic modulator device characteristics and the RF system performance measures of link gain (insertion loss), bandwidth, noise figure, and dynamic range; results are then presented that have established the viability of EAMs for wideband, low-loss, linear analog photonic links.

Recent advances in antiguided diode laser arrays

Antiguided arrays have been optimized for single-spatial-mode operation to high output power. Diffraction-limited beam operation to cw power levels of 0.5 W have been reproducibly obtained. The high efficiency operation (wall plug efficiency = 20%) and demonstrated reliability make these practical devices, and useful for many applications requiring a high output power spatially coherent beam. Two-dimensional optical waveguide calculations demonstrate the mechanisms responsible for the high mode selectivity of these structures. It is also made clear why coupled-mode theory failed to predict how to obtain single-lobe phase-locked array operation, and what are the conditions to obtain stable, in-phase mode behavior.

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.

300-mW diffraction-limited beam from flat-phase-front antiguided master oscillator power amplifier

Semiconductor master oscillator power amplifier (MOPA) devices based on the resonant transmission properties of resonant-optical-waveguide (ROW) antiguided structures are shown to be promising candidates for stable, coherent, high-power sources. A novel mast oscillator for this type of MOPA is proposed: the three-core antiresonant reflecting optical waveguide (ARROW) diode laser. This device is also based on ROW antiguided structures and can easily be integrated with the power amplifier. Three-core ARROW lasers are shown to have large intermodal discrimination against unwanted modes, and when used as the maser oscillator of a ROW-MOPA, a uniform near-field, flat-phasefront, diffraction-limited beam output is obtained. Experimentally, 350 mW diffraction-limited beam operation has been demonstrated in ROW-MOPA devices without extremely low AR coatings.

Integrated optoelectronic interconnect for phased-array antenna applications

An integrated semiconductor interconnect chip is being developed for the distribution of microwave signals to the subarrays and/or radiating elements of a phased array antenna (PAA). The baseline chip design calls for a 1 X 4 distribution fanout, and consists of both waveguide splitters and integrated optical amplifiers to compensate for inherent splitting as well as excess waveguide and coupling losses. Analysis is being performed to evaluate the RF performance of photonic links containing semiconductor optical amplifiers, and to determine the most judicious use of such an interconnect in the photonic feed network of a PAA.

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.

Modal reflectivity of horizontal cavity surface-emitting lasers, amplifiers, and SLEDs

In this paper a beam propagation model used to compute model reflectivities of HC SELs, amplifiers, and SLEDs will be presented. These devices all employ an intracavity 45 degree(s) micromirror which causes the light to propagate in a direction perpendicular to the epilayers. The lack of a waveguide structure for propagation perpendicular to the epilayers and the broad angular spectrum produced by highly confined transverse modes of GRINSCH-SQW devices must be considered when analyzing folded-cavity devices. The model includes Fresnel reflections from multilayer thin-films, angular errors in the 45 degree(s) micromirror, the dependence on the horizontal reflector separation, Fresnel beam propagation, and waveguide coupling losses of the reflected field. The model predicts good conversion efficiencies, despite low effective reflectivities from the folded-end-mirror. There is good agreement with experimental data.

Single-mode ARROW-type diode lasers

Design, fabrication, and characteristics of Antiresonant Reflecting Optical Waveguide (ARROW)-type diode lasers are presented. A complete two-dimensional optical waveguide analysis of the self-aligned-stripe (sas) ARROW-type laser indicates strong single-mode selectivity in these structures. Large core-width devices (10 micron) are expected to operate in a stable, single lateral mode, permitting the potential for reliable single-mode operation in the several hundred milliwatt range.

Monolithic Two-dimensional Surface-emitting Diode Laser Arrays Mounted In The Junction-down Configuration

M. Jansen, J. J. Yang, S. S. Ou, M. Sergant, L. Mawst, J. Rozenbergs, J. Wilcox, and D. Botez Citation: Applied Physics Letters 59, 2663 (1991); doi: 10.1063/1.105932 View online: http://dx.doi.org/10.1063/1.105932 View Table of Contents: http://scitation.aip.org/content/aip/journal/apl/59/21?ver=pdfcov Published by the AIP Publishing