Apparatuses and methods for alkali spectroscopy

A method, comprising:

• injecting, into a first port of an optical waveguide, an optical pump signal having a frequency approximately the frequency of required to excite electrons, of an alkali atom, to a higher energy state;
• injecting, into a second port of the optical waveguide, an optical probe signal having the frequency approximately the frequency of required to excite electrons, of an alkali atom, to a higher energy state, where a power level of the optical probe signal is less than the power level of the optical pump signal;
• propagating the pump signal and the probe signal in opposite directions along at least a portion of the optical waveguide;
• extending evanescent fields of at least one of the optical pump signal and the optical probe signal outside of the at least a portion of the optical waveguide, so that evanescent fields interact with alkali atoms for a sufficient amount of time to obtain a frequency resolution of spectroscopy of twenty megahertz or less;
• detecting the power level of the optical probe signal emanating from the second port from the optical waveguide;
• and
• adjusting the frequency of the optical pump signal, based upon the detected optical probe signal power level, so that the frequency is equal to a frequency resulting in the optical pump signal exciting, to a higher energy level, electrons, of at least one alkali atom moving in a direction that is orthogonal to the axis along which the optical pump signal and the optical probe signal propagate through the optical waveguide.

A method, comprising forming a porous dielectric on a substrate;

• forming a porous, unclad waveguide;
• forming a low index of refraction region under the porous, unclad waveguide;
• depositing alkali;
• and
• hermetically sealing a cover or cover layer over the low index of refraction region, the porous, unclad waveguide, an environment having a low index of refraction, and the alkali.