We report on the development of a single frequency laser operating at a wavelength of 2.1 μm. This laser uses a holmium-doped distributed Bragg reflector (DBR) structure pumped at 1.15 μm. These lasers have applications in precision measurement, coherent laser radar and beam combination. Initial characterisation of the laser is included.
A holmium non-linear polarisation rotation (NLPR) all-fibre mode-locked laser was characterised. The radiofrequency (RF) spectrum of the pulsed train output was used as an automation metric. Non-ideal pulsing behaviour was corrected by changing the intracavity polarisation state using actuators in an electronic polarisation controller. The optimum cavity produced mode-locked pulses with a central wavelength of 2.061 μm and an 8.7 nm optical full-width-at-half-maximum (FWHM).
We have investigated the effect of the frequency shift associated with an acousto-optic (AO) interaction on the spectral quality of acousto-optically tuned external cavity semiconductor lasers. A ring-cavity was built and the wavelength controlled by a frequency compensating acousto-optic tunable filter pair, which allowed user control over the frequency shift of the interacting light. Laser spectra were recorded for a range of frequency shifts, and a 30 kHz driving frequency gave the optimal spectral response where the output spectral shape did not vary as a function of operating wavelength and resulted in <0.1 nm linewidths.