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Combined microwave-optical pump-probe methods are emerging to study the quantum state of spin qubit centers and the charge dynamics in semiconductors. A major hindrance is the limited bandwidth of microwave irradiation/detection circuitry which could be overcome with the use of broadband coplanar waveguides (CPW). We present the development and performance characterization of two spectrometers: an optically detected magnetic resonance spectrometer (ODMR) and a microwave detected photoconductivity measurement. In the first method light serves as detection and microwaves excite the investigated medium, while in the second the roles are interchanged. The performance is demonstrated by measuring ODMR maps on the nitrogen-vacancy center in diamond and time resolved photoconductivity in p-doped silicon. The results demonstrate both an efficient coupling of the microwave irradiation to the samples as well as an excellent sensitivity for minute changes in sample conductivity., 5 pages, 5 figures

Alkali intercalated graphite compounds represent a compelling modification of carbon with significant application potential and various fundamentally important phases. We report on the intercalation of graphite with alkali atoms (Li and K) using liquid ammonia solution as mediating agent. Alkali atoms dissolve well in liquid ammonia which simplifies and speeds up the intercalation process, and it also avoids the high temperature formation of alkali carbides. Optical microscopy, Raman, and electron spin resonance spectroscopy attest that the prepared samples are highly and homogeneously intercalated to a level approaching Stage-I intercalation compounds. The method and the synthesis route may serve as a starting point for the various forms of alkali atom intercalated carbon compounds (including carbon nanotubes and graphene), which could be exploited in energy storage and further chemical modifications.