Spectroscopic gas detection using a Bragg grating - stabilized external cavity laser, custom written in planar integrated silica-on-silicon

Abstract

We present the development of an external cavity Bragg grating stabilized laser for tunable diode laser spectroscopy (TDLS). Our design uses a planar integrated silica-on-silicon platform incorporating a custom written Bragg grating as the wavelength-selective element of the laser cavity. We have developed a prototype singlemode laser at 1651 nm and performed a detailed characterization of its performance for the purpose of spectroscopic measurement of methane at this wavelength using a 25 cm path-length single-pass cell. Mode hop-free tuning of 0.13 nm has been demonstrated at frequencies of up to 10 kHz. A single-point limit of detection for TDLS of ∆I/I 0 = 8.3 × 10 −5 AU was achieved, which is consistent with the performance of standard distributed feedback lasers. The new device exhibits a side-mode suppression ratio of −40 dB and a low RIN of <−150 dB/Hz, and thus avoids the high levels of noise or instability normally associated with larger, mechanically driven external cavity lasers. The silica-on-silicon platform has the potential for low-volume manufacturing of special lasers at the custom wavelengths required for gas detection, without the need for investment in foundry solutions.

Direct UV written waveguides and Bragg gratings in doped planar silica using a 213 nm laser

“…Introduction: Bragg gratings in planar silica provide functionality for various integrated devices such as optical sensors [1], grating stabilized semiconductor lasers [2], and add-drop filter components [3]. Bragg grating based devices are usually fabricated using conventional lithography and etching to form both the waveguide and grating structures.…”