M. Aoki et al., INP-BASED REVERSED-MESA RIDGE-WAVE-GUIDE STRUCTURE FOR HIGH-PERFORMANCE LONG-WAVELENGTH LASER-DIODES, IEEE journal of selected topics in quantum electronics, 3(2), 1997, pp. 672-683
A novel structure for an InP-based ridge-waveguide (RWG) laser is demo
nstrated. It has a reverse-trapezoid-ridge shape which offers reduced
threshold current and smaller electrical and thermal resistances over
the conventional vertical-mesa (VM) RWG devices. We found this new RWG
laser quite suitable for wide-temperature-range and high-power operat
ions. 1.3-1.55-mu m wavelength strained InGaAsP-InP multiple quantum-w
ell (MQW) lasers were demonstrated with the new ridge structure, which
showed sufficient lasing behavior such as high-temperature lasing up
to 165 degrees C and a high light output over 300 mW. This simple and
high-performance laser structure was also applied for integrated laser
s with other functional elements such as an absorption-type modulator
or a beam-expander waveguide lens. To achieve low-threshold current op
eration in RWG lasers, suppression of the lateral-current spreading is
important. We proposed a new method to effectively reduce this latera
l diffusion current by using a doped active region with n-type dopant.
Combined by the reduced transparency carrier density in the n-doped a
ctive region, this leads to a very low-threshold current of less than
2.2 mA for a coated 200-mu m-long cavity device, which is comparable t
o those of recent advanced same-material buried-heterostructure (BH) L
asers. These excellent lasing properties, along with the sufficient de
vice reliability under strict environmental conditions, make this reve
rsed-mesa (RM) RWG a promising candidate for the widespread use of low
-cast long-wavelength light sources.