Electro-modulation spectroscopy and laser performance of an InGaAsP asymmetric multi-quantum-well structure

Abstract

The optical properties of an asymmetric multi-quantum-well laser structure of 5, 5, 10, 10, 15, 15 nm InGaAsP wells with an integrated 0.2-μm thick passive waveguide layer on the n-cladding side have been investigated by electro-modulation spectroscopy. Photocurrent and differential absorption spectra were measured at different reverse bias voltages to study the electroabsorption behaviors. The e1–hh1 optical transition near λ=1.67 μm attributable to the 15-nm wells shows a 20 nm red-shift at −5 V bias. The chirp parameter, obtained by calculating the differential absorption spectra through Kramers–Krönig transform, has a near-zero value near λ=1.67 μm under several different reverse bias voltages. A ridge waveguide laser with the waveguide width adiabatically tapered-up from 2.5 to 4 μm was fabricated to convert the spot size. The laser has a threshold current of 34 mA and far-field divergence angles of 12°×33° (θ //×θ ⊥) , and a peak wavelength of 1.632 μm.