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Atsuo Michiue coauthored work on blue laser diodes based on indium gallium nitride. The devices delivered $1.17$ W of optical power at $1.0$ A electric current, with $24.3\%$ wall-plug efficiency, for potential full-color displays.^[ref]

A physicist who helped achieve continuous operation of semiconductor lasers at room temperature. A double heterostructure surrounded a thin active layer with different semiconductor layers, reducing the current needed to sustain lasing. This addressed a practical obstacle in early devices and helped make laser diodes useful for optical communication and other technologies.^[ref]

A laser diode is an electrically injected semiconductor laser. Forward biasing supplies electrons and electron holes to an active region, where radiative recombination can amplify a compatible optical mode by stimulated emission.

Reflecting facets or other cavity structures provide feedback. Below the laser threshold, emission is dominated by spontaneous processes; above it, stimulated emission into resonator modes becomes important. A light-emitting diode can also use carrier recombination but does not require this feedback-and-gain threshold. Output power, emitted spectrum and terminal current-voltage characteristic together characterize the device more fully than brightness alone.

A forward-biased p-n junction injects electrons from its n-type semiconductor and electron holes from its p-type semiconductor into an active region. A direct band gap allows radiative transitions without a compensating phonon, so stimulated emission can compete effectively with nonradiative processes. At thermal equilibrium there is one Fermi level; forward injection instead establishes separate electron and valence-electron quasi-Fermi levels $F_c$ and $F_v$. Sufficient injection makes conduction states more occupied than the corresponding valence states, producing optical gain.

Two parallel cleaved facets supply an optical resonator. At normal incidence their approximate intensity reflectance follows the Fresnel equations:A resonant normal mode grows when its round-trip amplification exceeds its losses. For length $L$, material optical gain $g$, overlap factor $\Gamma$, internal intensity loss ${\alpha }_i$ and facet reflectances $R_1,R_2$,The pump supplies the emitted energy; the facets provide feedback and let some output escape. Positive optical gain alone does not establish laser threshold.

A semiconductor laser uses a semiconductor as its laser gain medium. Pumping produces carrier populations that permit stimulated emission between suitable electronic states. An optical resonator supplies feedback, and oscillation begins when the gain compensates round-trip losses.

A laser diode supplies pumping by electrical injection; other semiconductor lasers can be optically pumped. The band gap, confinement and resonator determine the possible emission range. A measurement of optical output versus pump strength helps locate the laser threshold, while an emission spectrum tests the modes involved. Increasing output alone does not establish that the device has entered coherent laser oscillation.

Shin-ichi Nagahama coauthored work on blue laser diodes based on indium gallium nitride. The devices delivered $1.17$ W of optical power at $1.0$ A electric current, with $24.3\%$ wall-plug efficiency, for potential full-color displays.^[ref]

Takashi Miyoshi coauthored work on blue laser diodes based on indium gallium nitride. The devices delivered $1.17$ W of optical power at $1.0$ A electric current, with $24.3\%$ wall-plug efficiency, for potential full-color displays.^[ref]

Tokuya Kozaki coauthored work on blue laser diodes based on indium gallium nitride. The devices delivered $1.17$ W of optical power at $1.0$ A electric current, with $24.3\%$ wall-plug efficiency, for potential full-color displays.^[ref]

Tomoya Yanamoto coauthored work on blue laser diodes based on indium gallium nitride. The devices delivered $1.17$ W of optical power at $1.0$ A electric current, with $24.3\%$ wall-plug efficiency, for potential full-color displays.^[ref]