title: Highly coherent modeless broadband semiconductor laser.
abstract: We report on the highly coherent modeless broadband continuous wave operation of a semiconductor vertical-external-cavity-surface-emitting laser. The laser design is based on a frequency-shifted-feedback scheme provided by an acousto-optic frequency shifter inserted in a linear or a ring traveling wave cavity. The gain mirror is a GaAs-based multiple quantum well structure providing large gain at 1.07 μm. This laser exhibits a coherent optical spectrum over 1.27 nm (330 GHz) bandwidth, with 70 mW output power and a high beam quality. The light polarization is linear (>30  dB extinction ratio). The laser dynamics exhibits a low intensity noise close to class A regime, with a ∼1.5  MHz cutoff frequency. The frequency noise spectral density shows a first-order low-pass like shape (130 kHz cutoff) leading to a Gaussian shape for homodyne interferometric signals. The measured beat width is ≃54  kHz and the coherence time of ∼19  μs. No nonlinear effects are observed, showing dynamics very close to theory.
authors.forename: M
authors.initials: M
authors.lastname: Sellahi
authors.forename: M
authors.initials: M
authors.lastname: Myara
authors.forename: G
authors.initials: G
authors.lastname: Beaudoin
authors.forename: I
authors.initials: I
authors.lastname: Sagnes
authors.forename: A
authors.initials: A
authors.lastname: Garnache