Bragg-grating-stabilized external cavity lasers for gas sensing using tunable diode laser spectroscopy

摘要

Conventional singlemode semiconductor DFB and VCSEL lasers used in high resolution spectroscopy are often required to operate at specific, custom wavelengths, such as those associated with gas absorption lines. We present the results of work to develop alternative sources in the 1550nm and 1650nm regions, the latter coinciding with an absorption line of methane. Custom wavelength Bragg gratings have been used to stabilize the output of external cavity lasers implemented in both optical fiber and planar silica-on-silicon integrated circuits, using commercially available semiconductor gain chips, to give laser output at 1648 and 1649 nm, respectively. Thermal expansion or mechanical strain of the Bragg grating offers a suitable wavelength tuning mechanism. Results are presented including the wavelength tuning range, output power, relative intensity noise (RIN), side-mode suppression and linewidth of devices for application in high resolution gas spectroscopy. The different methods of writing Bragg gratings in optical fiber and planar silica-on-silicon allow a high degree of flexibility in the choice of emission wavelength.