In the development of semiconductor lasers, it has been a dream all along to simultaneously obtain extremely wide and uniform gain distribution, because such a gain configuration can greatly enhance semiconductor laser performance. Hence, it has also been a huge challenge to realize this dream so far. In this paper, we are reporting a special InGaAs-based well–island composite quantum-confined structure, with which the best results to date in achieving both superwide and very uniform gain and power distributions are obtained. The spectral flatness of the output power can reach 0.1 dB, and the gain bandwidth is broadened to 6-fold broader than the fwhm (full width at half-maximum) of the standard gain spectrum from a classic InGaAs quantum well under the same carrier density. The formation of the well–island composite quantum-confined structure is associated with the indium-rich island effect in the material growth. The great significance of this work lies in that it is making the above dream come true, since it not only can tremendously increase the spectral tuning range of an InGaAs-based semiconductor laser but also exhibits a great potential on achieving uniform output power over the full spectral tuning range of the laser.

In this Letter, the loss and gain characteristics of an unconventional In x Ga 1−x As∕GaAs asymmetrical step well structure consisting of variable indium contents of In x Ga 1−x As materials are measured and analyzed for the first time, to the best of our knowledge. This special well structure is formed based on the indium-rich effect from the material growth process. The loss and gain are obtained by optical pumping and photoluminescence (PL) spectrum measurement at dual facets of an edge-emitting device. Unlike conventional quasi-rectangle wells, the asymmetrical step well may lead to a hybrid strain configuration containing both compressive and tensile strains and, thus, special loss and gain characteristics. The results will be very helpful in the development of multiple wavelength InGaAs-based semiconductor lasers.

In this paper, an absolute-phase unwrapping and speckle suppression approach to reconstruct a three-dimensional (3-D) image of an object with laser digital holography is described. This method offers three advantages to enhance the performance of the phase reconstruction technique. First, both speckle suppression and phase unwrapping are processed in the complex amplitude domain rather than in the single phase or amplitude domain. With this approach, the phase details of the object are better preserved upon phase reconstruction. Second, the proposed algorithm requires no threshold determination and thus achieves self-adaptive speckle suppression and robust phase unwrapping, in contrast to other methods. Finally, an improved dual-domain image denoising method is applied to further remove speckle-remnant-induced phase distortion. Ideal 3-D phase reconstruction results are obtained both theoretically and experimentally for the first time.

A kind of new quantum confined indium (In)rich cluster (IRC) laser with polarized dual-wavelength output is first proposed and realized. Unlike conventional quantum well/dot lasers, its optical characteristics depend on the special IRC effect-formed quantum confined structure, in which the asymmetric distribution and various sizes of IRCs are generated due to high strains in the indium-based material system. It may lead to a special band structure suitable for synchronous dual-wavelength lasing generation. The mechanism of the laser operation is associated with independent carrier transitions and stimulated emissions from multiple local indium-based active regions, which have various areas and different indium contents due to the IRC effect. The sample uses InGaAs/GaAs/GaAsP as the kernel of lasing medium with the edge-emitting configuration, both facets of which are used as cavity mirrors. The experiment exhibits synchronous dual wavelengths of lasing at 970 and 980 nm in transverse electric (TE) polarization, with a total slope efficiency of 34.6% at a room temperature of 300 K. The result is of great significance in the development of new types of monolithic quantum confined lasers with dual-wavelength and polarization output.

In this paper, an experimental approach to acquiring true spontaneous emission rate of optically-pumped InGaAs/GaAs quantum-well laser structure is described. This method is based on a single edge-emitting laser chip with simple sample processing. The photoluminescence spectra are measured at both facets of the edge-emitting device and transformed to the spontaneous emission rate following the theory described here. The unusual double peaks appearing in the spontaneous emission rate spectra are observed for the InGaAs/GaAs quantum-well structure. The result is analyzed in terms of Indium-rich island and Model-Solid theories. The proposed method is suitable for electrically-pumped quantum-well laser structures, as well.