Experimental demonstration of a tunable dual-frequency semiconductor laser free of relaxation oscillations

Abstract

Tunable dual-frequency oscillation is demonstrated in a vertical external-cavity surface-emitting laser. Simultaneous and robust oscillation of the two orthogonally polarized eigenstates is achieved by reducing their overlap in the optical active medium. The class-A dynamics of this laser, free of relaxation oscillations, enables one to suppress the electrical phase noise in excess that is usually observed in the vicinity of the beat note.

Intensity- and phase-noise correlations in a dual-frequency vertical-external-cavity surface-emitting laser operating at telecom wavelength

“…In the absence of noise, N 0x and N 0y can be replaced by their time averaged values N 0x and N 0y and the steadystate solutions of Eqs. (9)(10)(11)(12) for simultaneous oscillation of the two cross-polarized modes are…”

“…The Fourier transform δφ H (f ) of this RF phase noise can be readily obtained thanks to Eqs. (9)(10)(11)(12) as…”

“…More importantly, the intensity and phase fluctuations of the two polarizations are expected to be strongly correlated as the two laser modes are oscillating inside the same cavity and pumped by the same laser source. Such DF-VECSELs have been demonstrated for several different wavelengths such as * Electronic address: Fabien.Bretenaker@u-psud.fr 1 µm [9], 852 nm [10], and recently we have realized DF-VECSEL operating at 1.55 µm wavelength [11]. The noise properties of such DF-VECSEL are not easy to analyze as the two laser modes are coupled and, in addition to that, phase and intensity fluctuations are linked with each other due to the large Henry factor (α-factor) of the semiconductor gain medium [12].…”

Influence of spin-dependent carrier dynamics on the properties of a dual-frequency vertical-external-cavity surface-emitting laser

“…This low-frequency intensity noise limits the spectral purity of the beatnote generated by dualfrequency solid-state lasers. On the contrary, the dualfrequency VECSEL overcomes this limitation since the cm-long external cavity ensures class-A dynamical behavior of the laser by making intra-cavity photon lifetime much longer than the carrier lifetime inside the semiconductor active medium [13,24]. Moreover, to obtain stable simultaneous oscillation of the two modes, the nonlinear coupling constant between the modes is reduced below unity by spatially separating the two modes inside the gain medium with an intra-cavity birefringent crystal.…”

Tunable dual-frequency laser source for coherent population trapping cesium atomic clocks

“…This configuration takes benefit of the intrinsically strong correlation between the two laser lines which share the same cavity; additionally, the frequency difference is tunable by adjusting the cavity anisotropy. Finally, the low relative-intensity-noise (RIN) of VECSELs on a wide spectral range is of particular interest for this application, as it should provide a high-purity RF beat-note phase spectrum [3]. A dual-frequency VECSEL should thus have major potentials for miniature atomic clocks.…”