Class-A dual-frequency VECSEL at telecom wavelength

Abstract

We report class-A dual-frequency oscillation at 1.55 μm in a vertical external cavity surface emitting laser with more than 100 mW optical power. The two orthogonal linear polarizations of different frequencies oscillate simultaneously as their nonlinear coupling is reduced below unity by spatially separating them inside the active medium. The spectral behavior of the radio frequency beatnote obtained by optically mixing two polarizations and the phase noise of the beatnote have been explored for different coupling strengths between the lasing modes.

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…”

“…This ensures relaxation oscillation free class-A dynamical behavior of our DF-VECSEL. Simultaneous oscillation of the two polarizations is achieved by spatially separating them inside the gain medium using an intra-cavity birefringent crystal (BC), which reduces the nonlinear coupling between the modes below unity [11]. A 150-µm thick uncoated glass etalon inserted between the intracavity BC and the output coupler of the cavity forces each polarization to be longitudinally monomode.…”

“…For both weak and moderately strong coupling, the theoretical model nicely agrees with the experiment. The parameter values used for simula-tions for both coupling condition are obtained from the experimental conditions except from the value of τ , which is taken from previous experiments [11]. Here, the important points to note are the values of pump RIN, pump noise correlation amplitude η, and phase ψ used for different coupling situations.…”

“…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].…”