Figure 1
From: Application of a self-injection locked cyan laser for Barium ion cooling and spectroscopy
Diagrams of self-injection laser to illustrate principle of operation. (a) Top view. Light from a single mode Fabry Perot laser diode (LD) is focused with a lens and sent through an adjustable glass slide into an anti-reflection coated coupling prism (P1) made out of BK7. The glass slide, mounted on a tilt stage, compensates for mechanical creep. A piezo-electric transducer (PZT) adjusts the distance between P1 and the whispering gallery mode laser (WGM) cavity to control the evanescent coupling into laser cavity and to ensure single-mode operation20. Light circulates in the WGM cavity and the resonant modes are controlled by the geometry of the cavity. The reflective gold nano-particle (NP) size and spacing aid in rarefying the resonant modes in the cavity. A PZT on top of the WGM cavity, not shown in the illustration, controls the wavelength of the light by applying a force on the WGM cavity to change its refractive index [see (b)]. A third PZT controls the distance between the WGM and the reflector prism (P2) to adjust the amount of optical feedback into the laser diode. Light from the WGM evanescently couples into P2, and a gold-coated face of P2 reflects light back into the laser diode. The laser output exits P1 where it is collimated by a lens. (b) Side view with P1, P2, and associated PZTs not shown. The temperature of the Fabry Perot laser diode and optical bench are controlled by thermo-electric cooler (TEC) baseplates. The LD focusing lens is mounted on a five axis stage (not shown in the figure for clarity) for beam steering and adjusting mode-matching into the WGM cavity.
