How We Use LPP & PAL

Using Liquid Crystal Polymers (LCP), Photo-Alignment Layer (PAL) and a variety of dopants, we are able to create three-dimensional patterns of liquid crystals captured within a thin film (2-4um).

Photo-Alignment Layer


Actual LCP Thickness of 2um

Actual LCP Thickness of 2umreactive LC photo alignment layer


“Standard” Thin-Film Fabrication Techniques

alignment layer processing


Underlying Technology: PGs

  • Polarization Gratings (PGs) are basis for IO technology
  • Polarized diffraction
  • Right & left circular
  • +/- 1st orders only
  • Highly efficient
  • Low leakage: <1%
  • Tunable operation
  • Broadband
  • Narrowband

Geometric vs Dynamic Phase

(The Dynamic) Phasedynamic-phase term

The “normal” phase delay.

For example,

  • Prisms
  • Lenses
  • Phase gratings
  • Spatial Light Modulators (computer generated holograms)

All optical path length difference

(The Geometric) Phase

(Reference, wave in vacuum)geometric phase term

(Isotropic media) “normal” phase delay called dynamic phase due to optical path length difference

(Anisotropic media)

“extra” phase delay

called geometric phase


Geometric Phase Hologram Theory

  • Phase encoded into orientation
  • Hologram, with primary, conjugate, and leakage waves
  • Spectral behavior depends on retardation not spatial profile
  • Features
    • around 100% efficient for most and interesting profiles
    • 1000s of radians, continuous phase profile
    • Max phase slope ~ π rad/µm (!)