We demonstrate vertical integration of InGaAs mesa photodiodes with InGaAsP rib waveguides employing an intermediate optical impedance matching layer. The diode length necessary for 90% light absorption at 1.52 μm wavelength was 42 μm, a threefold reduction in diode length with respect to previous work employing similar waveguides without a matching layer. The quantum efficiency was observed to be almost independent of the optical wavelength and polarization. The influence of spatial transient intensity redistribution effects on these devices is investigated in detail.
We show that the coupling efficiency from a laser diode (LD) to an optical fiber through a ball lens can be calculated accurately using the exact solution to Maxwell's equations for the scattering of a beam from a dielectric sphere. Our calculated results agree closely with coupling measurements from an asymmetric LD for two different ball lenses.
A novel impedance-matched structure is proposed for improved coupling in evanescently coupled, integrated waveguide/photodetectors. We show that insertion of an impedance-matching layer between waveguide and detector regions can improve the coupling by a factor of ≊7, resulting in shorter detectors with lower capacitance and higher frequency response. The impedance-matching mechanism is discussed in detail.
We present a semi-empirical, analytic formula for the refractive index of AlxGa1−xAs below the band edge. The formula describes experimental refractive indices to within ±0.02 accuracy over the wavelength range from 1.5 to 0.75 μm and over the complete range of AlGaAs compositions.
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