Effect of stress on the polarization of stimulated emission from injection lasers

Abstract

The role of stress on the polarization of stimulated emission is discussed in this paper. The stimulated emission from injection lasers is usually polarized in the TE mode. However, in the presence of a sufficiently high stress in the active region, TM polarized stimulated emission at threshold can be observed. We find that for some InGaAsP buried heterostructure lasers with a kink in the light-current characteristic, the kink represents the onset of a TM polarized stimulated emission. X-ray diffraction measurements show that the active region of these devices are under stress. We show that the change in polarization characteristics associated with the light-current kinks can be due to (i) higher optical gain of the TM emission than TE in the presence of stress and (ii) larger reflectivity of the higher-order TM modes. This mechanism is supported by the observation of higher-order TM modes than TE and the observation that the TM gain is unsaturated above TE threshold. We also find that the TM kinks occur at lower currents as the external pressure is increased. In the absence of stress in the active region, stimulated emission in higher-order TE modes associated with light-current kinks is observed in buried heterostructure lasers with large active region. Our results show that the observation of stimulated TM emission in real index guided laser structures is indicative of internal stress in the active region of these devices.

Enhanced Emission from Defect Levels in Multilayer MoS2

“…To show that the D peak emission is associated with stimulated emission, we next demonstrate strong polarization effects, [49] occurring at the D peak beyond the threshold powers in Figures 1 and 3. We collect PL spectra at 25 mW where the incident light is vertically polarized and the scattered light is either unpolarized (VU), vertically polarized (VV, also p-polarized at prism surface, perpendicular to the grating grooves as seen in the equipment setup in Figure S8 in the Supporting Information), or horizontally polarized (VH, also s-polarized, parallel to the grating grooves).…”

Strain‐Activated Stimulated Emission from Multilayer MoSe2 in a Narrow Operation Window

“…Under 2.5 mW, strong polarization is observed, as the PL intensity ratio increases to 30 near 890 nm (D peak). [32,45] The PL ratio remains around 5 when the multilayer MoSe 2 is excited by 5 mW laser power, indicating no polarization effect, corresponding to the disrupted PL intensity above 4 mW laser power. The PL intensity ratio also stays around 5 from the flat region under a laser power of 2.5 mW in Figure S9, Supporting Information, indicating no polarization effect.…”

Polarized cathodoluminescence for strain measurement

“…For instance, in field-effect transistors, strain engineering is used to enhance the mobility of carriers in the channel. 1 In laser diodes, strain affects the emission wavelength, the emission polarization, the threshold current, and the gain 2,3 as well as the operating lifetime. 4 Photoelastic optical waveguides have also been developed.…”