Semiconductor Laser Characterization Graded-index separate confinement double he

Question

Semiconductor Laser Characterization
Graded-index separate confinement double heterostructure (GRIN-SCH) InGaAs/GaAs lasers with various cavity lengths were tested in the lab. The 100?m wide oxide strip lasers consists of two pairs of 10nm In0.2Ga0.8As quantum-well (QW). The barriers of the lasers are 10nm GaAs (undoped). The lasers give a lasing wavelength around 970nm at room temperature. The refractive index of the active InGaAs layer is 3.4.


iii) With the aid of a band diagram, explain what is population inversion.

Explanation / Answer

Semi conductor lasers are widely used as coherent light sources in many applications. The semiconductor lasers have very different characteristics compared to conventional atomic or molecular laser resources The main features of the semiconductor lasers are: - very small size - high efficiency - lower price Graded-index seperate confinement hetrostructure singlequantumwell GaAs/ALGaAs diode laser exhibiting continious operation at room temperature have been grown on a si substrate by organmetallic vapor-phase without the help of molecular beam epitaxy. - To improve the quality of laser structure, a defect filtering layer is incorporated between this structure and GaAs buffer layer. -An impurity free vacancy diffusion method was used to intermix the quantum wells.Eventhough intermixing involved annealing at 1000 c whic results in a 42-nm wavelenght blueshift.

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