Polarization dependent study of gain anisotropy in semipolar InGaN lasers

Abstract

The optical gain of single quantum well laser structures on semipolar (1122)-GaN in dependence of the optical polarization and the resonator orientation has been studied by variable stripe length method. The c'-[1123] resonator shows maximum gain in TE mode, followed by the m-[1100]-resonator with extraordinary polarization. The anisotropic gain behaviour is explained by valence sub-band ordering and birefringence of the wurtzite crystal, resulting in a modification of the transition matrix element for stimulated emission. Measurements are accompanied by 6 x 6 k . p band structure calculations and gain analysis

Valence band states and polarized optical emission from nonpolar and semipolar III–nitride quantum well optoelectronic devices

“…Nevertheless, the change in polarization between adjacent layers in a III-nitride waveguide (typically a couple of degrees at most) is still very close to the polarization predicted by the indicatrix construction for waves in a bulk III-nitride crystal, as predicted by theoretical calculations 38,68) and confirmed by experimental measurements. 69,70) The polarization of modes in a birefringent waveguide is often different than the usual polarization parallel (transverse electric or TE mode) and perpendicular (transverse magnetic or TM mode) to the growth plane, as discussed in more detail below.…”

“…71) However, for waveguides on semipolar growth planes, waveguide orientations parallel to the yA-direction do not coincide with natural crystal faces (i.e., crystal planes with rational Miller indices), so mirror facets need to formed on these waveguide orientations by dry etching or polishing. 72) As cleaving is a more mature technology for fabricating mirror facets than dry etching or polishing, there have been many studies to assess the suitability of waveguide orientations perpendicular to the yA-direction for semipolar LDs, 19,24,38,[68][69][70][73][74][75] as discussed in more detail in Sect. 4.5.…”

“…Thus, if ¡ is the angle between â and ðÀih " rÞju i i, then the magnitude of the gain should vary as cos 2 ¡. 70) 4.4 Nonpolar III-nitride edge-emitting LDs Waveguide orientation determines the magnitude of the gain and the polarization of stimulated emission for nonpolar III-nitride edge-emitting LDs. As an example, waveguide orientation is examined below for an m-plane III-nitride edge-emitting LD, although the discussion could be generalized to a-plane III-nitride edge-emitting LDs as well.…”

Demonstration of Electrically Injected Semipolar Laser Diodes Grown on Low-Cost and Scalable Sapphire Substrates

“…A stimulated emission with TE polarization is observed with a polarization ratio of 97.6%, where the ratio is given by ( P TE – P TM )/( P TE + P TM ), and is similar to what is classically observed in c -plane LDs reaching a ratio of 100:1 . Such highly polarized light emission has many potential applications for back-lighting technology or polarization sensitive devices …”

“…33 Such highly polarized light emission has many potential applications for back-lighting technology or polarization sensitive devices. 34…”