Vertical External Cavity Surface Emitting Lasers for Laser Threshold Magnetometry and Tunable Transverse Mode Control

Abstract

Vertical external cavity surface emitting lasers (VECSELs) have undergone impressive advancements and maturation since their first demonstration over twenty years ago. The VECSEL benefits from the spectral tailoring of a semiconductor laser through bandgap engineering and structure design while maintaining an external cavity like many solid-state lasers, allowing access to high circulating powers. High output powers, diffraction-limited beams, ultrashort pulses, and nonlinear frequency conversions have all been demonstrated using this laser platform. In this dissertation, we cover the general design, fabrication, and testing of VECSELs at various wavelengths. We highlight our work on GaAs-based high power VECSELs in the near-IR and visible wavelengths as well as the preliminary efforts on InP-based VECSELs for mode-locked operation in the telecommunication O-band. This is followed by a demonstration of the direct generation of tunable Laguerre-Gaussian beams, and potentially mode-locked tunable Hermite-Gaussian beams using VECSELs. The second part of the thesis covers the incorporation of a diamond-plate doped with nitrogen-vacancy (NV) centers into the external cavity of a VECSEL to implement optically detected magnetic resonance (ODMR) using a proposed technique known as laser threshold magnetometry (LTM). Published work on NV center ODMR has primarily focused on optical readout through photoluminescence, which suffers from poor collection efficiencies and limited signal contrast. Optical readout using cavity enhanced infrared probe absorption to increase collection efficiencies has also been performed; however, the signal contrast has been limited to a similar degree as photoluminescent readout. By implementing LTM with an infrared VECSEL, we demonstrate both high collection efficiencies and signal contrast. Although the measured magnetic sensitivity of 2.5 nT/√Hz was modest, the elevated contrast of 18.4% indicates the potential for a new class of NV center magnetometers which may be capable of outperforming existing approaches. The projected photon shot noise limited sensitivity of 9.7 pT/√Hz was comparable to other ODMR demonstrations with little optimization of the external cavity. This demonstration is followed by a discussion of the technical noise sources limiting the performance and outlines potential approaches to reduce them, thereby realizing enhanced magnetic sensitivities.