MONOLITHIC INTEGRATION IN INGAAS-INGAASP MULTIPLE-QUANTUM-WELL STRUCTURES USING LASER INTERMIXING

The bandgap of InGaAs-InGaAsP multiple-quantum-well (MQW) material can be accurately tuned by photoabsorption-induced disordering (PAID), us ing a Nd:YAG laser, to allow lasers, modulators, and passive waveguide s to be fabricated from a standard MQW structure, The process relies o n optical absorption in the active region of the MQW to produce suffic ient heat to cause interdiffusion between the wells and barriers, Band gap shifts larger than 100 meV are obtainable using laser power densit ies of around 5 W . mm(-2) and periods of illumination of a few minute s to tens of minutes, This process provides an effective way of alteri ng the emission wavelengths of lasers fabricated from a single epitaxi al wafer, Blue shifts of up to 160 nm in the lasing spectra of both br oad-area and ridge waveguide lasers are reported, The bandgap-tuned la sers are assessed in terms of threshold current density, internal quan tum efficiency, and internal losses, The ON/OFF ratios of bandgap-tune d electroabsorption modulators were tested over a range of wavelengths , with modulation depths of 20 dB obtained from material which has bee n bandgap-shifted by 120 nm, while samples shifted by 80 mn gave modul ation depths as high as 27 dB, Single-mode waveguide losses are as low as 5 dB . cm(-1) at 1550 mm, Selective-area disordering has been used in the fabrication of extended cavity lasers, The retention of good e lectrical and optical properties in intermixed material demonstrates t hat PAID is a promising technique for the integration of devices to pr oduce photonic integrated circuits, A quantum-well intermixing techniq ue using a pulsed laser is also demonstrated.