For tunable quantum well lasers, it has been a huge challenge all along how to achieve an ultra-wide tuning spectrum far exceeding the full width at half maximum (FWHM) of gain in a classic quantum well and the uniform power output for all tunable wavelengths of the laser under a fixed injection power, especially based on a single well structure. In this paper, we are reporting some amazing results from a special asymmetrical InGaAs quantum well structure, with which both incredibly extremely-wide and nearly uniform gain spectra are obtained with a fixed injection power. The excellent gain characteristics may make above dream come ture for the InGaAs-based tunable lasers. The formation of the structure is associated with the Indium-rich island effect. The analysis showed that the spectrally-tunable range from this special well structure could be up to 6 times as broad as the FWHM of gain in the classic InGaAs well and the gain spectrum with quasi-rectangular feature in transverse electric mode was obtained as well. It enables nearly identical power output over the total spectrally tunable range of the laser to be realized with a fixed optical injection power.
In any off-axis holographic experiments, it is generally difficult to accurately obtain plane reference wave angle so that tilt phase aberration (TPA) occurs in three-dimensional phase reconstruction for the object. In this paper, a novel approach to accurately determining the plane reference wave angle for phase reconstruction of the object in digital offaxis holography is described. The method ingeniously constructs a numerical reference plane (NRP) reflecting true tilt of the reconstructed object by randomly choosing three points from a local flat of the reconstructed object image, and establishes the relation between NRP tilt and plane reference wave angle. So the reference wave angle can be exactly obtained by iterative computation and TPA is completely compensated. The experimental result approves of theoretical prediction very well.
In this paper, the loss and gain characteristics of optically-pumped InGaAs/GaAs quantum well lasers are measured based on the photoluminescence spectra from dual facets of a single laser device. The device is pumped by 808nm fiber coupled semiconductor lasers controlled with pulsing signal and beam shaping system to reduce the thermal effect. The result of loss spectra is consistent with gain spectra well. In addition, the special double-peak configuration in the loss and gain spectra is observed and analyzed, in term of the strain mechanism and band structure of InGaAs quantum well. The results will be very helpful to the study and design of the InGaAs semiconductor lasers
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