Spontaneous emission

About: Spontaneous emission is a research topic. Over the lifetime, 12855 publications have been published within this topic receiving 323684 citations.

Monolithic Ge-on-Si lasers for large-scale electronic–photonic integration

Abstract: A silicon-based monolithic laser source has long been envisioned as a key enabling component for large-scale electronic–photonic integration in future generations of high-performance computation and communication systems. In this paper we present a comprehensive review on the development of monolithic Ge-on-Si lasers for this application. Starting with a historical review of light emission from the direct gap transition of Ge dating back to the 1960s, we focus on the rapid progress in band-engineered Ge-on-Si lasers in the past five years after a nearly 30-year gap in this research field. Ge has become an interesting candidate for active devices in Si photonics in the past decade due to its pseudo-direct gap behavior and compatibility with Si complementary metal oxide semiconductor (CMOS) processing. In 2007, we proposed combing tensile strain with n-type doping to compensate the energy difference between the direct and indirect band gap of Ge, thereby achieving net optical gain for CMOS-compatible diode lasers. Here we systematically present theoretical modeling, material growth methods, spontaneous emission, optical gain, and lasing under optical and electrical pumping from band-engineered Ge-on-Si, culminated by recently demonstrated electrically pumped Ge-on-Si lasers with >1 mW output in the communication wavelength window of 1500–1700 nm. The broad gain spectrum enables on-chip wavelength division multiplexing. A unique feature of band-engineered pseudo-direct gap Ge light emitters is that the emission intensity increases with temperature, exactly opposite to conventional direct gap semiconductor light-emitting devices. This extraordinary thermal anti-quenching behavior greatly facilitates monolithic integration on Si microchips where temperatures can reach up to 80 °C during operation. The same band-engineering approach can be extended to other pseudo-direct gap semiconductors, allowing us to achieve efficient light emission at wavelengths previously considered inaccessible.

Temperature dependence of threshold of InGaAsP/InP double‐heterostructure lasers and Auger recombination

Abstract: We have calculated the nonradiative Auger recombination rate as a function of temperature in InGaAsP Inclusion of this process can explain the observed temperature dependence of threshold and carrier lifetime of both the 13‐ and 155‐mm InGaAsP double‐heterostructure lasers The threshold calculations are carried out using the Halperin‐Lax‐Kane band model, Stern’s matrix element, and Beattie‐Landsberg theory of Auger recombination Evidence of the Auger recombination is provided by a sublinearity of the spontaneous emission as a function of injection current

Self-consistent gain analysis of type-II ‘W’ InGaN–GaNAs quantum well lasers

Abstract: Type-II InGaN–GaNAs quantum wells (QWs) with thin dilute-As (∼3%) GaNAs layer are analyzed self-consistently as improved III-nitride gain media for diode lasers. The band structure is calculated by using a six-band k⋅p formalism, taking into account valence band mixing, strain effect, spontaneous and piezoelectric polarizations, as well as the carrier screening effect. The type-II InGaN–GaNAs QW structure allows large electron-hole wave function overlap by confining the hole wave function in the GaNAs layer of the QW. The findings based on self-consistent analysis indicate that type-II InGaN-GaNAs QW active region results in superior performance for laser diodes, in comparison to that of conventional InGaN QW. Both the spontaneous emission radiative recombination rate and optical gain of type-II InGaN–GaNAs QW structure are significantly enhanced. Reduction in the threshold current density of InGaN–GaNAs QW lasers is also predicted.

Ground-state emission and gain in ultralow-threshold InAs-InGaAs quantum-dot lasers

Abstract: Emission spectra and modal optical gain are investigated in ultralow-threshold MBE-grown InAs-InGaAs quantum dot (QD) structures. The record lowest room-temperature inversion current is found to be /spl sim/13 A cm/sup -2/. The rate-equation model is proposed describing the optical gain related to the ground-state (GS) transitions in QDs. The ground-state gain goes to the maximum value that corresponds to the total inversion of available levels. The gain cross section for the GS emission is estimated as /spl sim/7/spl times/10/sup -15/ cm/sup 2/.

Indistinguishable single photons from a single-quantum dot in a two-dimensional photonic crystal cavity

Abstract: We report on the spontaneous emission of a single-quantum dot embedded in a two-dimensional photonic crystal cavity. The resonant coupling between the dot and the strongly localized optical mode significantly shortens the spontaneous emission lifetime, so that the coherence time of the emitted photons is dominated by radiative effects: The emitted photons are indistinguishable, with a mean wave-packet overlap as high as 72%.