How do I calculate the radiance?

The radiance can be estimated in two ways:

• Supposing the laser is emitting monomode transversal and ideal optics for a gaussian 00-beam apply, the radiance is then given by ${B=4\times P/(\lambda^2)}$, with P the optical output power and ${\lambda}$ the wavelength of the laser.

• Using standard values (which can vary for up to factors of 2 between lasers), the aperture A is in the range of 0.03mm by 0.005mm, and the illuminated solid angle (for 60deg vertical and 20deg horizontal divergence) W is in the range of 0.3 (or ${2\times\pi\times 0.045})$, and therefore the radiance ${B=P/A/W}$ or approximately $B=P/(4e-5mm^2)$.

These are highly approximative values; if you need well defined ones, ask for the needed values for a specific laser you are interested in.