Permanent optical bleaching in HPHT-diamond via aggregation of C- and NV-centers excited by visible-range femtosecond laser pulses

Abstract

Red-colored high-pressure, high-temperature synthesized (HPHT) diamond was exposed in its bulk in a number of patterns to millions of 0.3-ps, 515-nm laser pulses focused by a 0.25-NA micro-objective. The resulting arrays of bright micrometer-scale spots produced at variable laser exposure and pulse energy was characterized by optical transmission microspectroscopy, room-temperature dynamic and stationary 3D confocal photoluminescence (PL) microspectroscopy, FT-IR microspectroscopy. These bleached spots exhibit 1) reduced IR-absorbance of C- and A-centers at the pertaining absorbance of interstitials, 2) stronger reduced visible-range absorbance of C centers, comparing to that of NV0 and NV− centers, 3) considerably depth-wise reduced PL intensity of NV0 and NV− centers in favor of the emerging blue-green (480–550 nm) PL band of indistinguishable higher-aggregated H3, H4 centers. The photo-activated aggregation process of nitrogen centers exhibits second-power dependence on laser energy and is apparently related to direct agitation of low-aggregated centers, rather than to photo-generation of interstitial-vacancy pairs.