VSPIN: a new model relying on the vectorial description of the laser field for predicting the polarization dynamics of spin-injected V(e)CSELs

Spin injection enhancement in CW VECSEL at room temperature using push-pull optical pumping

We report the enhancement of spin injection efficiency in an external-cavity VCSEL based on a non-resonant pumping coupled with a polarized optical resonant illumination. This double pumping scheme allows both the injection of spin polarized electrons in the conduction band and the selection of the spin orientation for the electron/hole recombination laser process. Experimentally, a flip of the polarization state of the laser is achieved with an ellipticity of +31° (spin down) and -33° (spin up), so an increase of about 50% of the ellipticity is achieved in comparison to an optical non-resonant pumping alone.

Spin Laser Local Oscillators for Homodyne Detection in Coherent Optical Communications

We numerically investigate spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) for local oscillators, which are based on an injection locking technique used in coherent optical communications. Under the spin polarization modulation of an injection-locked spin-VCSEL, frequency-shifted and phase-correlated optical sidebands are generated with an orthogonal polarization against the injection light, and one of the sidebands is resonantly enhanced due to the linear birefringence in the spin-VCSEL. We determine that the peak strength and peak frequency in the spin polarization modulation sensitivity of the injection-locked spin-VCSEL depend on detuning frequency and injection ratio conditions. As a proof of concept, 25-Gbaud and 16-ary quadrature amplitude modulation optical data signals and a pilot tone are generated, and the pilot tone is used for the injection locking of a spin-VCSEL. An orthogonally-polarized modulation sideband generated from the injection-locked spin-VCSEL is used as a frequency-shifted local oscillator (LO). We verify that the frequency-shifted LO can be used for the homodyne detection of optical data signals with no degradation. Our findings suggest a novel application of spin-VCSELs for coherent optical communications.

Generalised theory of polarisation modes for resonators containing birefringence and anisotropic gain

Polarisation eigenmode theory is well established for laser cavities in which the principal axes for gain and polarisation elements are parallel. Here we generalise the theory to include the case for gain axes at arbitrary angle to the birefringence, which is the case for Raman lasers based on cubic-class gain crystals that contain stress-induced birefringence. The theory describes regimes dominated by gain, linear or circular birefringence, and the intermediate regime in which elliptically polarised output modes are obtained. Previously reported behaviour for diamond Raman lasers are found to be in accord with the findings. Design criteria are obtained to enable prediction of polarisation behaviour as functions of birefringence and resonator design.