Gaussian beam propagation

Outline


A lens on an L angle Al
illuminated by a laser.

Propagated beam

Focal length measurement of a lens (F=5.5mm)

Green laser waist radius at lens is 0.4mm from beam profiler.

Source laser beam divergence angle 1.3mrad=λ/πw0

w0=141μm, ZR=πw02/λ=117.6mm

At s=312mm

w(s)=w0(1+(zλ/πw02)2)0.5=0.4mm

1/sp=1/f-1/(s+ZR2/(s-f)) sp=5.6mm

1/m=((1-s/f)2+(ZR/f)2)0.5

wp0=mw0=2.4mm

Will expand to 10mm in radius at 145mm.

First calculate from 0.4/fb=10/(145-fb) (0.4+10)fb=145*0.4 fb=5.57mm

Approximate f by fb to calculate- wo’ Propagate by the distance
z=20-fb =14.4mm to see if w(z) match 1.9. If not, improve
approximation off.

Oxide Corporation

Speckle contrast Measurement System