InAs quantum dot (QD) ridge waveguide (RWG) lasers comprising single-port multi-mode-interference-reflectors (MMIR) and single-cleaved reflectors are designed, fabricated, and characterized, to demonstrate capability for optoelectronic-integrated circuits. Simulations of an MMI- R show high values of fundamental mode reflectivity (> 80%) and good selectivity against higher-order modes. Deep-etched MMIR lasers fabricated with 0.5 mm long cavities have a threshold current of 24 mA, compared to 75 mA for standard cleaved-cleaved RWG lasers of the same length, both at 25 oC, and 56 mA compared to 102 mA at 55 oC. MMIR lasers exhibit stable ground state operation up to 50oC and show promise as small footprint sources for integrated photonics.

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InAs quantuin uot multi ,noue-interference-1 c::dlector (MM -R) lasers, basea on a 1-port MM� and a sin e le cleaved reflector, are de•igned, fabricated, ana charact1;, rized to demonstrate capability for optoelectronic-inteofllted-circuits. Threshold current densities are less than ..; u% <,fth::ise in cleaved-cleaved ridge waveguid� lasers o�the sam� cavity length.

A systematic analysis of the performance of VCSELs, fabricated with a decreasing number of structural elements, is used to assess the complexity of fabrication (and therefore time) required to obtain sufficient information on epitaxial wafer suitability. Initially, sub-mA threshold current VCSEL devices are produced on AlGaAs-based material, designed for 940 nm emission, using processing methods widely employed in industry. From there, stripped-back Quick Fabrication (QF) devices, based on a bridge-mesa design, are fabricated and this negates the need for benzocyclcobutane (BCB) planarisation. Devices are produced with three variations on the QF design, to characterise the impact on laser performance from removing time-consuming process steps, including wet thermal oxidation and mechanical lapping used to reduce substrate thickness. An increase in threshold current of 1.5 mA for oxidised QF devices, relative to the standard VCSELs, and a further increase of 1.9 mA for unoxidised QF devices are observed, which is a result of leakage current. The tuning of the emission wavelength with current increases by ~0.1 nm/mA for a VCSEL with a 16 μm diameter mesa when the substrate is unlapped, which is ascribed to the increased thermal resistance. Generally, relative to the standard VCSELs, the QF methods employed do not significantly impact the threshold lasing wavelength and the differences in mean wavelengths of the device types that are observed are attributed to variation in cavity resonance with spatial position across the wafer, as determined by photovoltage spectroscopy measurements.