Beam nonuniformity ratio (BNR) is defined as:

Beam nonuniformity ratio (BNR) is defined as:

• A. The ratio of the spatial average intensity to the spatial peak intensity
• B. The ratio of the spatial peak intensity to the spatial average intensity
• C. The ratio of duty cycle to frequency
• D. The ratio of on time to total time

Answer: (B)

Beam nonuniformity ratio measures how uneven a laser beam is by comparing the highest intensity across the beam to the average intensity across its cross-section. When a beam is nearly uniform, the peak and the average are close, giving a BNR near 1; real beams have hot spots, so the peak is higher and the BNR exceeds 1. The standard definition is the ratio of spatial peak intensity to spatial average intensity. For example, if the peak is 100 units and the average is 25 units, the BNR is 4, indicating notable nonuniformity. The reciprocal would misrepresent the concept, and duty cycle or on-time to total-time relate to temporal, not spatial, beam properties.

Beam nonuniformity ratio measures how uneven a laser beam is by comparing the highest intensity across the beam to the average intensity across its cross-section. When a beam is nearly uniform, the peak and the average are close, giving a BNR near 1; real beams have hot spots, so the peak is higher and the BNR exceeds 1. The standard definition is the ratio of spatial peak intensity to spatial average intensity. For example, if the peak is 100 units and the average is 25 units, the BNR is 4, indicating notable nonuniformity. The reciprocal would misrepresent the concept, and duty cycle or on-time to total-time relate to temporal, not spatial, beam properties.