Spin-VCSELs with Local Optical Anisotropies: Toward Terahertz Polarization Modulation

Abstract

We present a semi-classical model for spin-injected vertical-cavity surface-emitting lasers (spin-VCSELs) with local optical anisotropies. Particular focus is put on highly-anisotropic spin-lasers with broad application potential. A generalized matrix formalism for extraction of the laser modes is introduced, which enables to calculate spatial distribution of vectorial modes in arbitrary spin-VCSELs. Time-dependence of such laser modes is further studied using the generalized coupled mode theory (CMT). It is the natural anisotropic generalization of the conventional modedecomposition approach. We use the circularly-polarized optical modes as the basis for CMT, which leads to extension of the well-known spin-flip model (SFM). In contrary to conventional SFM, the only input parameters are the geometric and local optical properties of the multilayer structure and properties of the gain media. The advantages of the theory are demonstrated on design and optimization of spin-VCSEL structure with high-contrast grating. We show that the proposed structures can be used for i) polarization modulation in THz range with tremendous applications for future ultrafast optical communication and ii) as perspective compact THz sources.

All-Optical Linear-Polarization Engineering in Single and Coupled Exciton-Polariton Condensates

“…Different parts for polariton based spin circuitry have already been realized 9,10,[20][21][22] with some recent exciting theoretical proposals 23,24 , but many challenges remain to be solved. Optical applications such as data communication or sensing benefit from precise control over a laser's polarization and modulation speeds, ideally using nonresonant excitation schemes like spin-VCSELs [25][26][27] . In this spirit, a great deal of effort has been devoted to generating sources of linearly polarized light such as colloidal nanorods 28 , materials with anisotropic optical properties 29 , quantum dots 30 , and optical parametric oscillators 31 .…”

Spin Laser Local Oscillators for Homodyne Detection in Coherent Optical Communications

“…When the optical carrier remains after the polarization selective component, it causes cross talk at the stage of polarization hybrid coherent detection. Third, birefringence controls of spin-VCSELs including theoretical modeling are important for efficient generation of orthogonally-polarized modulation sideband with a high frequency [58][59][60][61][62]. Since the sensitivity of spin polarization modulation is subject to birefringence, efficient generation of an orthogonally-polarized modulation sideband requires birefringence control with accuracy in the order of a few gigahertz.…”

Three-Variable Reduction of the Spin-Flip Model for Spin-VCSELs

“…Amongst the proposed advantages of these devices over conventional lasers, the promise of very high speed operation [2] has recently excited much attention. It has been shown that high material birefringence can lead to frequency splitting [3] that enables ultra-fast polarisation modulation [4,5] and a possible route to a practical terahertz source [6]. The birefringence can be increased by applying strain [3][4][5], heating [7] or the incorporation of an integrated surface grating [8].…”

“…In reality, however, this is an approximation since these anisotropies originate from interfacial, surface and strain effects within the VCSEL structure [19]. Hence a more accurate model to account for these non-local anisotropies is based on a matrix approach which yields the spatial distribution of the electromagnetic modes of the spin-VCSEL [6,20]. This model is particularly well suited also to model the effects of an integrated surface grating in order to tailor the high-speed performance of the device [6].…”

“…Hence a more accurate model to account for these non-local anisotropies is based on a matrix approach which yields the spatial distribution of the electromagnetic modes of the spin-VCSEL [6,20]. This model is particularly well suited also to model the effects of an integrated surface grating in order to tailor the high-speed performance of the device [6]. Another model that takes account of spatial effects has been developed to describe the dynamics of arrays of coupled spin-VCSELs [21,22].…”