A longitudinal Pockels cell shutter is cut from ADP (ammonium dihydrogen phosphate)

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Polarisation and anisotropic media · Polarisation and anisotropic media

What an Instrument Can See, Ch Modulating light: electro-optic, acousto-optic and magneto-optic devices

Problem

A longitudinal Pockels cell shutter is cut from ADP (ammonium dihydrogen phosphate), for which

n_o = 1.52

and

r_{63} = 8.5\,\mathrm{pm\,V^{-1}}

\lambda_0 = 633\,\mathrm{nm}

. The crystal's ring electrodes, together with the coaxial drive cable, present a lumped capacitance

C = 8.0\,\mathrm{pF}

to a driver of output resistance

R = 50\,\Omega

; take the drive circuit as a simple lumped

RC

low-pass, neglecting resistive-line and inductive effects. ((a)) Compute the half-wave voltage of the longitudinal cell. ((b)) Compute the 3 dB bandwidth of the lumped drive circuit. ((c)) The shutter must switch within a bandwidth of at least 300 MHz. State whether the drive circuit meets this. Then say which of your two answers would stay the same if the crystal's length were doubled, with the electrodes still on its end faces, and which way the other would move.

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