Spatial and polarization entanglement of lasing patterns and related dynamic behaviors in laser-diode-pumped solid-state lasers

Abstract

To provide the underlying physical mechanism for formations of spatial- and polarization-entangled lasing patterns (namely, SPEPs), we performed experiments using a c-cut Nd:GdVO(4) microchip laser with off-axis laser-diode pumping. This extends recent work on entangled lasing pattern generation from an isotropic laser, where such a pattern was explained only in terms of generalized coherent states (GCSs) formed by mathematical manipulation. Here, we show that polarization-resolved transverse patterns can be well explained by the transverse mode-locking of distinct orthogonal linearly polarized Ince-Gauss (IG) mode pairs rather than GCSs. Dynamic properties of SPEPs were experimentally examined in both free-running and modulated conditions to identify long-term correlations of IG mode pairs over time. The complete chaos synchronization among IG mode pairs subjected to external perturbation is also demonstrated.

Polarization-dependent intensity noise in a microchip solid-state laser with spatially coherent polarization vector fields

“…At this moment, the laser behaves like an "all-inone" coherent mode, featuring a strong correlation of amplitude fluctuations of paring IG modes [6] contrary to the anticorrelated orthogonally polarized modes in VCSELs [1,2]. Indeed, the intensity noise peaks only at the relaxation oscillation frequency, f RO , as shown in Fig.…”

“…Spatially coherent vector fields forming higher order transverse modes with vector singularities, that is, SU(2) coherent state, were reported along this framework in a purely isotopic solid-state laser crystal [3]. Apart from VCSELs, such lasing patterns are formed by a coherent superposition of degenerate eigenstates, that is, the transverse mode locking of a pair of orthogonally polarized frequencydegenerate Ince-Gauss (IG) modes, which constitute the third family of transverse resonator eigenmodes initiated by Bandres and Gutiérrez-Vega [4], with a fixed phase difference of ΔΦ 0 or π, in the form of IG 1 w e iΔΦ IG 2 , where w is the field weighting ratio of pairing IG modes [5,6]. Because an output from a well-stabilized single-frequency laser is spontaneously a coherent state, it is interesting to identify polarization-dependent noise properties of these transverse modes within the corresponding SU(2) coherent states.…”

“…The observed patterns were well reproduced theoretically, assuming ΔΦ 0, π, and the experimentally determined w-values for Figs. 2(a) and 2(b), respectively [6].…”

“…Despite the same p-value for a cold-cavity IGp; p mode pair, there is still certain anisotropy in the cavity because of thermal birefringence, which results in small frequency splitting of a degenerate IG mode pair. However, such a frequency splitting is removed through transverse mode locking of nearly degenerate modes assisted by the inherent saturation type of χ 3 optical nonlinearity in microchip solid-state lasers [5,6].…”

“…3(b) shows polarization-dependent power spectra, and the upper image shows the total output power spectrum. A strong correlation exists between the emission pattern and the polarization state in the present system [3,6], and the intensity noise power spectrum for the total output was fitted by the sum of polarizationresolved intensity noise spectra, that is, Iω ≃ P θ I ω; θ, contrary to the case of VCSELs for which orthogonally polarized modes are not degenerate and transverse mode locking is absent in general. In the case of Fig.…”