III. Optics — Control of light — move it from source to detector through experiment

A. Lenses + Mirror (Text: Ch 3 & 1,4) design — shape & materials — efficiency

1.Basic concepts: index of refraction — n = c/v, c = 3 x 108m/s,

conservation law: r(l) + a(l) + T(l) = 1 - mirror T~ 0 & lens T ~ 1

dispersion (n increase with dec l) — dn(l)/dl < 0

Snell’s law of refraction: n, sin q₁ = n₂ sin q₂,

reflection: q₁ = q₃ vs. refraction: q₂ < q₁ for n₁ < n₂

reflection loss: r(l) = (n2-n1/n2+n1)², normal,

Brewster angle, — zero reflection loss in one polarization (II refl. plane) at specific angle q_B = tan^-1(n2/n1)

Total internal reflection, - n1>n2, r(l) max at q1=qc, qc = sin^-1(n2/n1)

air — glass, eq goes here

2. Mirrors: spherical mirror imaging — reflection,

materials — Al(uv), Au(IR), coating can help r

magnification: m = -I/0 = - S₂/ S₁

S₁ > R — demagnify, f < S₁ < R — magnify, S₁ < f — no image

3. Lens: refraction straight line design, must transmit but losses due reflection or absorption

• quartz — uv (180nm) to near IR ~ 3 m. — 4.5 m.
• CaF2 — vuv (140nm) to mid IR ~ 8 m.
• ZnSe — yellow to IR ~ 16 m.
  • Ge — near IR to IR ~ 20 m.

Thin-lens

AR coating — reduce reflection loss (n — index lens, n Å 1 air) - r=(n-1/n+1)²

-- add l/4 layer of index n₁ = n — zero refl.

-- multilayer (N)— get zeros at (N — 1) l’s

4. Light gather power — trade off: more light or smaller image

F-number: [F/n] = f/D, D = (4A/p)^1/2

Varies as solid angle, W, E=B_s(p/4)/(F/n)²

5. Abberations: chromatic, spherical, coma, astigmatism