An apparatus for laser frequency conversion, comprising: a fundamental laser light source configured to generate fundamental wavelength laser light; at least one optical crystal configured to receive fundamental laser light from the fundamental laser light source, the at least one optical crystal configured to generate alternate wavelength light by frequency converting at least a portion of the received fundamental laser light to alternate wavelength light; an auxiliary light source configured to generate auxiliary wavelength light, the auxiliary wavelength light having a wavelength different from a wavelength of the fundamental wavelength laser light and a wavelength of the alternate wavelength light, the fundamental laser light source and the auxiliary light source oriented such that at least a portion of fundamental laser light substantially copropagates with at least a portion of auxiliary light through one or more surfaces of the optical crystal; and a detector (126, 322) configured to detect auxiliary light scattered by the optical crystal; one or more filters (124, 320) positioned between the optical crystal and the detector (126, 322), the one or more filters (124, 320) are configured to limit the transmission of scattered fundamental light and alternate light produced by the optical crystal; the one or more filters are configured to transmit the auxiliary light scattered by the optical crystal; and a computer system communicatively coupled to a beam characterization system, wherein the computer system is configured to: receive one or more measurement results from the detector; compare the received one or more detection results to a selected set of calibrated reference data; and determine an amount of time prior to a failure condition of the frequency conversion site of the at least one optical crystal based on the comparison between the received one or more detection results of the auxiliary light and the selected set of calibrated reference data. a fundamental laser light source configured to generate fundamental wavelength laser light; at least one optical crystal configured to receive fundamental laser light from the fundamental laser light source, the at least one optical crystal configured to generate alternate wavelength light by frequency converting at least a portion of the received fundamental laser light to alternate wavelength light; an auxiliary light source configured to generate auxiliary wavelength light, the auxiliary wavelength light having a wavelength different from a wavelength of the fundamental wavelength laser light and a wavelength of the alternate wavelength light, the fundamental laser light source and the auxiliary light source oriented such that at least a portion of fundamental laser light substantially copropagates with at least a portion of auxiliary light through one or more surfaces of the optical crystal; and a detector (126, 322) configured to detect auxiliary light scattered by the optical crystal; one or more filters (124, 320) positioned between the optical crystal and the detector (126, 322), the one or more filters (124, 320) are configured to limit the transmission of scattered fundamental light and alternate light produced by the optical crystal; the one or more filters are configured to transmit the auxiliary light scattered by the optical crystal; and a computer system communicatively coupled to a beam characterization system, wherein the computer system is configured to: receive one or more measurement results from the detector; compare the received one or more detection results to a selected set of calibrated reference data; and determine an amount of time prior to a failure condition of the frequency conversion site of the at least one optical crystal based on the comparison between the received one or more detection results of the auxiliary light and the selected set of calibrated reference data. receive one or more measurement results from the detector; compare the received one or more detection results to a selected set of calibrated reference data; and determine an amount of time prior to a failure condition of the frequency conversion site of the at least one optical crystal based on the comparison between the received one or more detection results of the auxiliary light and the selected set of calibrated reference data.