Electronically tunable single-mode external-cavity diode laser

A six-stage birefringent filter placed in an external cavity of an AlGaAs diode laser is used to scan the laser electronically over 10.3 nm, hopping single modes of the external cavity. Continuous electronic tuning of the single mode over the free spectral range of the external cavity, 182 MHz, is also demonstrated by using a variable-phase plate. All tuning mechanisms use nematic liquid-crystal electro-optic effects operating at <2 V.