Semiconductor optical gain

About: Semiconductor optical gain is a research topic. Over the lifetime, 5997 publications have been published within this topic receiving 96505 citations.

Spectral characteristics of vertical-cavity surface-emitting lasers with external optical feedback

Abstract: The measurement of the effects of external optical feedback on the spectra of VCSELs (vertical-cavity surface-emitting lasers) is reported. It is surprising that VCSELs have a sensitivity to optical feedback comparable to that of conventional edge-emitting lasers such as DFBs despite their significantly different structures. This is because the extremely short cavity length of VCSELs negates the effects of their highly reflective output mirrors. As in edge-emitting lasers, VCSELs exhibit well-defined regimes of feedback effects in their spectra. Since optical isolators cannot be easily applied to VCSELs due to their array structure, these lasers may be most useful in applications which are not sensitive to the spectral qualities of the light source. >

Enhanced modulation bandwidth in injection-locked semiconductor lasers

Abstract: Optical probing of an injection-locked semiconductor laser is used to show significant improvement in the intrinsic broad-band modulation characteristics relative to the free-running case. The regenerative amplification spectra of a weak optical probe in the injection-locked laser are in good agreement with the predictions of a conventional coupled-equation model. Based on the regenerative amplification spectra, the intrinsic modulation characteristic due to a weak injection current modulation can be calculated. It shows approximately a factor of three enhancement of the modulation bandwidth, beyond the K-factor limit of the free-running laser.

Raman injection laser.

Abstract: The Raman effect, in which a material shifts the wavelength of an incident light beam by absorbing part of the photon's energy, has found widespread use as a powerful diagnostic tool in chemistry and materials science. Raman lasers that are currently available, used in applications such as spectroscopy and microscopy, have only a small gain (or signal amplification) and require external pumping with powerful optical lasers. A new electrically driven semiconductor laser described in this issue uses the Raman effect to shift the wavelength of an internally Raman effect to shift the wavelength of an internally generated optical beam. This low-power compact Raman laser functions through most of the infrared wavelengths, and holds promise for extending the tunability, available range and applications of semiconductor lasers. Stimulated Raman scattering is a nonlinear optical process that, in a broad variety of materials, enables the generation of optical gain at a frequency that is shifted from that of the incident radiation by an amount corresponding to the frequency of an internal oscillation of the material1,2. This effect is the basis for a broad class of tunable sources known as Raman lasers2,3. In general, these sources have only small gain (∼ 10-9 cm W-1) and therefore require external pumping with powerful lasers, which limits their applications. Here we report the realization of a semiconductor injection Raman laser designed to circumvent these limitations. The physics underlying our device differs in a fundamental way from existing Raman lasers3,4,5,6,7,8: it is based on triply resonant stimulated Raman scattering between quantum-confined states within the active region of a quantum cascade laser that serves as an internal optical pump—the device is driven electrically and no external laser pump is required. This leads to an enhancement of orders of magnitude in the Raman gain, high conversion efficiency and low threshold. Our lasers combine the advantages of nonlinear optical devices and of semiconductor injection lasers, and could lead to a new class of compact and wavelength-agile mid-and far-infrared light sources.