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Butler, J. K.

Publications and source records attributed to Butler, J. K..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Coupled-mode analysis of gain and wavelength oscillation characteristics of diode laser phased arrays

The lasing wavelengths and gain characteristics of the modes of phase-locked arrays of channel-substrate-planar (CSP) lasers are presented. The gain values for the array modes are determined from complex coupling coefficients calculated using the fields of neighboring elements of the array. The computations show that, for index guided lasers which have nearly planar phase fronts, the highest order array mode will be preferred. The 'in-phase' or fundamental mode, which produces only one major lobe in the far-field radiation pattern, has the lowest modal gain of all array modes. The modal gain differential between the highest order and fundamental modes is less than 10/cm for weak coupling between the elements.

Butler, J. K.↗
NASA NTRS1984

Coupled-mode analysis of phase-locked injection laser arrays

A coupled-mode analysis has been developed to describe the output of phase-locked injection laser arrays. It is shown that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number of and the spacing of the emitters. The interaction between emitters leads to a splitting of the common frequency of operation that can be estimated from the coupling strength. The coupled-mode analysis is compared to calculations based on simple diffraction theory. A consequence of the analysis is an explanation for the commonly observed discrepancy between experimentally observed far-field lobe widths and those predicted by simple diffraction theory.

Butler, J. K.↗
NASA NTRS1982

Mode characteristics of nonplanar double-heterojunction and large-optical-cavity laser structures

Mode behavior of nonplanar double-heterojunction (DH) and large-optical-cavity (LOC) lasers is investigated using the effective index method to model the lateral field distribution. The thickness variations of various layers for the devices discussed are correlated with the growth characteristics of liquid-phase epitaxy over topographical features (channels, mesas) etched into the substrate. The effective dielectric profiles of constricted double-heterojunction (CDH)-LOC lasers show a strong influence on transverse mode operation: the fundamental transverse mode (i.e., in the plane perpendicular to the junction) may be laterally index-guided, while the first (high)-order mode is laterally index-antiguided. The analytical model developed uses a smoothly varying hyperbolic cosine distribution to characterize lateral index variations. The waveguide model is applied to several lasers to illustrate conditions necessary to convert leaky modes to trapped ones via the active-region gain distribution. Theoretical radiation patterns are calculated using model parameters, and matched to an experimental far-field pattern.

Butler, J. K.↗
NASA NTRS1977

Design curves for double-heterojunction laser diodes

This paper reviews theoretical double-heterojunction laser design curves relating the structure with the transverse mode order able to propagate, the degree of radiation confinement to the active region, the maximum field intensity within the device, and the radiated beam shape. The curves presented are general and applicable to any double-heterojunction structure where the spacing of the heterojunctions and the refractive index in the relevant regions are known.

Butler, J. K.↗
NASA NTRS1975

Internal optical losses in very thin CW heterojunction laser diodes

Theoretical calculations are presented showing the relationship between the internal laser absorption and structural parameters appropriate for CW room-temperature lasers. These diodes have submicron-thick recombination regions, and very small spacings between the heat sink and the recombination region to minimize the thermal resistance. The optical loss is shown to be strongly dependent on the degree of radiation confinement to the active region. In particular, absorption in the surface GaAs layer providing the ohmic contact becomes very significant when the intermediate (AlGa)As layer is reduced below about 1 micron. It is further shown that excessive penetration into the GaAs regions gives rise to anomalies in the far-field radiation profiles in the direction perpendicular to the junction plane.

Butler, J. K.↗