Metric for the measurement of the quality of complex beams: a theoretical study.

We present a theoretical study of various definitions of laser beam width in a given cross section. Quality of the beam is characterized by dimensionless beam propagation products (BPPs) Δx·Δθ(x)/λ, which are different for the 21 definitions presented, but are close to 1. Six particular beams are studied in detail.

Saturation of multiplexed volume Bragg grating recording.

Recording of volume Bragg gratings (VBGs) in photo-thermo-refractive glass is limited to a maximum refractive index change about 0.002. We discuss various saturation curves and their influence on the amplitudes of recorded gratings.